Back to index...

	/*
	* Copyright (c) 1995, 2017, Oracle and/or its affiliates. All rights reserved.
	* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
	*
	* This code is free software; you can redistribute it and/or modify it
	* under the terms of the GNU General Public License version 2 only, as
	* published by the Free Software Foundation. Oracle designates this
	* particular file as subject to the "Classpath" exception as provided
	* by Oracle in the LICENSE file that accompanied this code.
	*
	* This code is distributed in the hope that it will be useful, but WITHOUT
	* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
	* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
	* version 2 for more details (a copy is included in the LICENSE file that
	* accompanied this code).
	*
	* You should have received a copy of the GNU General Public License version
	* 2 along with this work; if not, write to the Free Software Foundation,
	* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
	*
	* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
	* or visit www.oracle.com if you need additional information or have any
	* questions.
	*/

	package java.net;

	import java.io.IOException;
	import java.io.InputStream;
	import java.io.OutputStream;
	import java.security.PrivilegedAction;
	import java.util.Hashtable;
	import java.util.concurrent.ConcurrentHashMap;
	import java.util.Date;
	import java.util.Iterator;
	import java.util.Locale;
	import java.util.Objects;
	import java.util.ServiceConfigurationError;
	import java.util.ServiceLoader;
	import java.util.StringTokenizer;
	import java.util.Collections;
	import java.util.Map;
	import java.util.List;
	import java.security.Permission;
	import java.security.AccessController;
	import sun.security.util.SecurityConstants;
	import sun.net.www.MessageHeader;
	import sun.security.action.GetPropertyAction;

	/**
	* The abstract class {@code URLConnection} is the superclass
	* of all classes that represent a communications link between the
	* application and a URL. Instances of this class can be used both to
	* read from and to write to the resource referenced by the URL.
	*
	* <p>
	* In general, creating a connection to a URL is a multistep process:
	* <ol>
	* <li>The connection object is created by invoking the
	* {@link URL#openConnection() openConnection} method on a URL.
	* <li>The setup parameters and general request properties are manipulated.
	* <li>The actual connection to the remote object is made, using the
	* {@link #connect() connect} method.
	* <li>The remote object becomes available. The header fields and the contents
	* of the remote object can be accessed.
	* </ol>
	* <p>
	* The setup parameters are modified using the following methods:
	* <ul>
	* <li>{@code setAllowUserInteraction}
	* <li>{@code setDoInput}
	* <li>{@code setDoOutput}
	* <li>{@code setIfModifiedSince}
	* <li>{@code setUseCaches}
	* </ul>
	* <p>
	* and the general request properties are modified using the method:
	* <ul>
	* <li>{@code setRequestProperty}
	* </ul>
	* <p>
	* Default values for the {@code AllowUserInteraction} and
	* {@code UseCaches} parameters can be set using the methods
	* {@code setDefaultAllowUserInteraction} and
	* {@code setDefaultUseCaches}.
	* <p>
	* Each of the above {@code set} methods has a corresponding
	* {@code get} method to retrieve the value of the parameter or
	* general request property. The specific parameters and general
	* request properties that are applicable are protocol specific.
	* <p>
	* The following methods are used to access the header fields and
	* the contents after the connection is made to the remote object:
	* <ul>
	* <li>{@code getContent}
	* <li>{@code getHeaderField}
	* <li>{@code getInputStream}
	* <li>{@code getOutputStream}
	* </ul>
	* <p>
	* Certain header fields are accessed frequently. The methods:
	* <ul>
	* <li>{@code getContentEncoding}
	* <li>{@code getContentLength}
	* <li>{@code getContentType}
	* <li>{@code getDate}
	* <li>{@code getExpiration}
	* <li>{@code getLastModified}
	* </ul>
	* <p>
	* provide convenient access to these fields. The
	* {@code getContentType} method is used by the
	* {@code getContent} method to determine the type of the remote
	* object; subclasses may find it convenient to override the
	* {@code getContentType} method.
	* <p>
	* In the common case, all of the pre-connection parameters and
	* general request properties can be ignored: the pre-connection
	* parameters and request properties default to sensible values. For
	* most clients of this interface, there are only two interesting
	* methods: {@code getInputStream} and {@code getContent},
	* which are mirrored in the {@code URL} class by convenience methods.
	* <p>
	* More information on the request properties and header fields of
	* an {@code http} connection can be found at:
	* <blockquote><pre>
	* <a href="http://www.ietf.org/rfc/rfc2616.txt">http://www.ietf.org/rfc/rfc2616.txt</a>
	* </pre></blockquote>
	*
	* Invoking the {@code close()} methods on the {@code InputStream} or {@code OutputStream} of an
	* {@code URLConnection} after a request may free network resources associated with this
	* instance, unless particular protocol specifications specify different behaviours
	* for it.
	*
	* @author James Gosling
	* @see java.net.URL#openConnection()
	* @see java.net.URLConnection#connect()
	* @see java.net.URLConnection#getContent()
	* @see java.net.URLConnection#getContentEncoding()
	* @see java.net.URLConnection#getContentLength()
	* @see java.net.URLConnection#getContentType()
	* @see java.net.URLConnection#getDate()
	* @see java.net.URLConnection#getExpiration()
	* @see java.net.URLConnection#getHeaderField(int)
	* @see java.net.URLConnection#getHeaderField(java.lang.String)
	* @see java.net.URLConnection#getInputStream()
	* @see java.net.URLConnection#getLastModified()
	* @see java.net.URLConnection#getOutputStream()
	* @see java.net.URLConnection#setAllowUserInteraction(boolean)
	* @see java.net.URLConnection#setDefaultUseCaches(boolean)
	* @see java.net.URLConnection#setDoInput(boolean)
	* @see java.net.URLConnection#setDoOutput(boolean)
	* @see java.net.URLConnection#setIfModifiedSince(long)
	* @see java.net.URLConnection#setRequestProperty(java.lang.String, java.lang.String)
	* @see java.net.URLConnection#setUseCaches(boolean)
	* @since 1.0
	*/
	public abstract class URLConnection {

	/**
	* The URL represents the remote object on the World Wide Web to
	* which this connection is opened.
	* <p>
	* The value of this field can be accessed by the
	* {@code getURL} method.
	* <p>
	* The default value of this variable is the value of the URL
	* argument in the {@code URLConnection} constructor.
	*
	* @see java.net.URLConnection#getURL()
	* @see java.net.URLConnection#url
	*/
	protected URL url;

	/**
	* This variable is set by the {@code setDoInput} method. Its
	* value is returned by the {@code getDoInput} method.
	* <p>
	* A URL connection can be used for input and/or output. Setting the
	* {@code doInput} flag to {@code true} indicates that
	* the application intends to read data from the URL connection.
	* <p>
	* The default value of this field is {@code true}.
	*
	* @see java.net.URLConnection#getDoInput()
	* @see java.net.URLConnection#setDoInput(boolean)
	*/
	protected boolean doInput = true;

	/**
	* This variable is set by the {@code setDoOutput} method. Its
	* value is returned by the {@code getDoOutput} method.
	* <p>
	* A URL connection can be used for input and/or output. Setting the
	* {@code doOutput} flag to {@code true} indicates
	* that the application intends to write data to the URL connection.
	* <p>
	* The default value of this field is {@code false}.
	*
	* @see java.net.URLConnection#getDoOutput()
	* @see java.net.URLConnection#setDoOutput(boolean)
	*/
	protected boolean doOutput = false;

	private static boolean defaultAllowUserInteraction = false;

	/**
	* If {@code true}, this {@code URL} is being examined in
	* a context in which it makes sense to allow user interactions such
	* as popping up an authentication dialog. If {@code false},
	* then no user interaction is allowed.
	* <p>
	* The value of this field can be set by the
	* {@code setAllowUserInteraction} method.
	* Its value is returned by the
	* {@code getAllowUserInteraction} method.
	* Its default value is the value of the argument in the last invocation
	* of the {@code setDefaultAllowUserInteraction} method.
	*
	* @see java.net.URLConnection#getAllowUserInteraction()
	* @see java.net.URLConnection#setAllowUserInteraction(boolean)
	* @see java.net.URLConnection#setDefaultAllowUserInteraction(boolean)
	*/
	protected boolean allowUserInteraction = defaultAllowUserInteraction;

	private static volatile boolean defaultUseCaches = true;

	/**
	* If {@code true}, the protocol is allowed to use caching
	* whenever it can. If {@code false}, the protocol must always
	* try to get a fresh copy of the object.
	* <p>
	* This field is set by the {@code setUseCaches} method. Its
	* value is returned by the {@code getUseCaches} method.
	* <p>
	* Its default value is the value given in the last invocation of the
	* {@code setDefaultUseCaches} method.
	* <p>
	* The default setting may be overridden per protocol with
	* {@link #setDefaultUseCaches(String,boolean)}.
	*
	* @see java.net.URLConnection#setUseCaches(boolean)
	* @see java.net.URLConnection#getUseCaches()
	* @see java.net.URLConnection#setDefaultUseCaches(boolean)
	*/
	protected boolean useCaches;

	private static final ConcurrentHashMap<String,Boolean> defaultCaching =
	new ConcurrentHashMap<>();

	/**
	* Some protocols support skipping the fetching of the object unless
	* the object has been modified more recently than a certain time.
	* <p>
	* A nonzero value gives a time as the number of milliseconds since
	* January 1, 1970, GMT. The object is fetched only if it has been
	* modified more recently than that time.
	* <p>
	* This variable is set by the {@code setIfModifiedSince}
	* method. Its value is returned by the
	* {@code getIfModifiedSince} method.
	* <p>
	* The default value of this field is {@code 0}, indicating
	* that the fetching must always occur.
	*
	* @see java.net.URLConnection#getIfModifiedSince()
	* @see java.net.URLConnection#setIfModifiedSince(long)
	*/
	protected long ifModifiedSince = 0;

	/**
	* If {@code false}, this connection object has not created a
	* communications link to the specified URL. If {@code true},
	* the communications link has been established.
	*/
	protected boolean connected = false;

	/**
	* @since 1.5
	*/
	private int connectTimeout;
	private int readTimeout;

	/**
	* @since 1.6
	*/
	private MessageHeader requests;

	/**
	* @since 1.1
	*/
	private static volatile FileNameMap fileNameMap;

	/**
	* Loads filename map (a mimetable) from a data file. It will
	* first try to load the user-specific table, defined
	* by "content.types.user.table" property. If that fails,
	* it tries to load the default built-in table.
	*
	* @return the FileNameMap
	* @since 1.2
	* @see #setFileNameMap(java.net.FileNameMap)
	*/
	public static FileNameMap getFileNameMap() {
	FileNameMap map = fileNameMap;

	if (map == null) {
	fileNameMap = map = new FileNameMap() {
	private FileNameMap internalMap =
	sun.net.www.MimeTable.loadTable();

	public String getContentTypeFor(String fileName) {
	return internalMap.getContentTypeFor(fileName);
	}
	};
	}

	return map;
	}

	/**
	* Sets the FileNameMap.
	* <p>
	* If there is a security manager, this method first calls
	* the security manager's {@code checkSetFactory} method
	* to ensure the operation is allowed.
	* This could result in a SecurityException.
	*
	* @param map the FileNameMap to be set
	* @exception SecurityException if a security manager exists and its
	* {@code checkSetFactory} method doesn't allow the operation.
	* @see SecurityManager#checkSetFactory
	* @see #getFileNameMap()
	* @since 1.2
	*/
	public static void setFileNameMap(FileNameMap map) {
	SecurityManager sm = System.getSecurityManager();
	if (sm != null) sm.checkSetFactory();
	fileNameMap = map;
	}

	/**
	* Opens a communications link to the resource referenced by this
	* URL, if such a connection has not already been established.
	* <p>
	* If the {@code connect} method is called when the connection
	* has already been opened (indicated by the {@code connected}
	* field having the value {@code true}), the call is ignored.
	* <p>
	* URLConnection objects go through two phases: first they are
	* created, then they are connected. After being created, and
	* before being connected, various options can be specified
	* (e.g., doInput and UseCaches). After connecting, it is an
	* error to try to set them. Operations that depend on being
	* connected, like getContentLength, will implicitly perform the
	* connection, if necessary.
	*
	* @throws SocketTimeoutException if the timeout expires before
	* the connection can be established
	* @exception IOException if an I/O error occurs while opening the
	* connection.
	* @see java.net.URLConnection#connected
	* @see #getConnectTimeout()
	* @see #setConnectTimeout(int)
	*/
	public abstract void connect() throws IOException;

	/**
	* Sets a specified timeout value, in milliseconds, to be used
	* when opening a communications link to the resource referenced
	* by this URLConnection. If the timeout expires before the
	* connection can be established, a
	* java.net.SocketTimeoutException is raised. A timeout of zero is
	* interpreted as an infinite timeout.

	* <p> Some non-standard implementation of this method may ignore
	* the specified timeout. To see the connect timeout set, please
	* call getConnectTimeout().
	*
	* @param timeout an {@code int} that specifies the connect
	* timeout value in milliseconds
	* @throws IllegalArgumentException if the timeout parameter is negative
	*
	* @see #getConnectTimeout()
	* @see #connect()
	* @since 1.5
	*/
	public void setConnectTimeout(int timeout) {
	if (timeout < 0) {
	throw new IllegalArgumentException("timeout can not be negative");
	}
	connectTimeout = timeout;
	}

	/**
	* Returns setting for connect timeout.
	* <p>
	* 0 return implies that the option is disabled
	* (i.e., timeout of infinity).
	*
	* @return an {@code int} that indicates the connect timeout
	* value in milliseconds
	* @see #setConnectTimeout(int)
	* @see #connect()
	* @since 1.5
	*/
	public int getConnectTimeout() {
	return connectTimeout;
	}

	/**
	* Sets the read timeout to a specified timeout, in
	* milliseconds. A non-zero value specifies the timeout when
	* reading from Input stream when a connection is established to a
	* resource. If the timeout expires before there is data available
	* for read, a java.net.SocketTimeoutException is raised. A
	* timeout of zero is interpreted as an infinite timeout.
	*
	*<p> Some non-standard implementation of this method ignores the
	* specified timeout. To see the read timeout set, please call
	* getReadTimeout().
	*
	* @param timeout an {@code int} that specifies the timeout
	* value to be used in milliseconds
	* @throws IllegalArgumentException if the timeout parameter is negative
	*
	* @see #getReadTimeout()
	* @see InputStream#read()
	* @since 1.5
	*/
	public void setReadTimeout(int timeout) {
	if (timeout < 0) {
	throw new IllegalArgumentException("timeout can not be negative");
	}
	readTimeout = timeout;
	}

	/**
	* Returns setting for read timeout. 0 return implies that the
	* option is disabled (i.e., timeout of infinity).
	*
	* @return an {@code int} that indicates the read timeout
	* value in milliseconds
	*
	* @see #setReadTimeout(int)
	* @see InputStream#read()
	* @since 1.5
	*/
	public int getReadTimeout() {
	return readTimeout;
	}

	/**
	* Constructs a URL connection to the specified URL. A connection to
	* the object referenced by the URL is not created.
	*
	* @param url the specified URL.
	*/
	protected URLConnection(URL url) {
	this.url = url;
	if (url == null) {
	this.useCaches = defaultUseCaches;
	} else {
	this.useCaches = getDefaultUseCaches(url.getProtocol());
	}
	}

	/**
	* Returns the value of this {@code URLConnection}'s {@code URL}
	* field.
	*
	* @return the value of this {@code URLConnection}'s {@code URL}
	* field.
	* @see java.net.URLConnection#url
	*/
	public URL getURL() {
	return url;
	}

	/**
	* Returns the value of the {@code content-length} header field.
	* <P>
	* <B>Note</B>: {@link #getContentLengthLong() getContentLengthLong()}
	* should be preferred over this method, since it returns a {@code long}
	* instead and is therefore more portable.</P>
	*
	* @return the content length of the resource that this connection's URL
	* references, {@code -1} if the content length is not known,
	* or if the content length is greater than Integer.MAX_VALUE.
	*/
	public int getContentLength() {
	long l = getContentLengthLong();
	if (l > Integer.MAX_VALUE)
	return -1;
	return (int) l;
	}

	/**
	* Returns the value of the {@code content-length} header field as a
	* long.
	*
	* @return the content length of the resource that this connection's URL
	* references, or {@code -1} if the content length is
	* not known.
	* @since 1.7
	*/
	public long getContentLengthLong() {
	return getHeaderFieldLong("content-length", -1);
	}

	/**
	* Returns the value of the {@code content-type} header field.
	*
	* @return the content type of the resource that the URL references,
	* or {@code null} if not known.
	* @see java.net.URLConnection#getHeaderField(java.lang.String)
	*/
	public String getContentType() {
	return getHeaderField("content-type");
	}

	/**
	* Returns the value of the {@code content-encoding} header field.
	*
	* @return the content encoding of the resource that the URL references,
	* or {@code null} if not known.
	* @see java.net.URLConnection#getHeaderField(java.lang.String)
	*/
	public String getContentEncoding() {
	return getHeaderField("content-encoding");
	}

	/**
	* Returns the value of the {@code expires} header field.
	*
	* @return the expiration date of the resource that this URL references,
	* or 0 if not known. The value is the number of milliseconds since
	* January 1, 1970 GMT.
	* @see java.net.URLConnection#getHeaderField(java.lang.String)
	*/
	public long getExpiration() {
	return getHeaderFieldDate("expires", 0);
	}

	/**
	* Returns the value of the {@code date} header field.
	*
	* @return the sending date of the resource that the URL references,
	* or {@code 0} if not known. The value returned is the
	* number of milliseconds since January 1, 1970 GMT.
	* @see java.net.URLConnection#getHeaderField(java.lang.String)
	*/
	public long getDate() {
	return getHeaderFieldDate("date", 0);
	}

	/**
	* Returns the value of the {@code last-modified} header field.
	* The result is the number of milliseconds since January 1, 1970 GMT.
	*
	* @return the date the resource referenced by this
	* {@code URLConnection} was last modified, or 0 if not known.
	* @see java.net.URLConnection#getHeaderField(java.lang.String)
	*/
	public long getLastModified() {
	return getHeaderFieldDate("last-modified", 0);
	}

	/**
	* Returns the value of the named header field.
	* <p>
	* If called on a connection that sets the same header multiple times
	* with possibly different values, only the last value is returned.
	*
	*
	* @param name the name of a header field.
	* @return the value of the named header field, or {@code null}
	* if there is no such field in the header.
	*/
	public String getHeaderField(String name) {
	return null;
	}

	/**
	* Returns an unmodifiable Map of the header fields.
	* The Map keys are Strings that represent the
	* response-header field names. Each Map value is an
	* unmodifiable List of Strings that represents
	* the corresponding field values.
	*
	* @return a Map of header fields
	* @since 1.4
	*/
	public Map<String,List<String>> getHeaderFields() {
	return Collections.emptyMap();
	}

	/**
	* Returns the value of the named field parsed as a number.
	* <p>
	* This form of {@code getHeaderField} exists because some
	* connection types (e.g., {@code http-ng}) have pre-parsed
	* headers. Classes for that connection type can override this method
	* and short-circuit the parsing.
	*
	* @param name the name of the header field.
	* @param Default the default value.
	* @return the value of the named field, parsed as an integer. The
	* {@code Default} value is returned if the field is
	* missing or malformed.
	*/
	public int getHeaderFieldInt(String name, int Default) {
	String value = getHeaderField(name);
	try {
	return Integer.parseInt(value);
	} catch (Exception e) { }
	return Default;
	}

	/**
	* Returns the value of the named field parsed as a number.
	* <p>
	* This form of {@code getHeaderField} exists because some
	* connection types (e.g., {@code http-ng}) have pre-parsed
	* headers. Classes for that connection type can override this method
	* and short-circuit the parsing.
	*
	* @param name the name of the header field.
	* @param Default the default value.
	* @return the value of the named field, parsed as a long. The
	* {@code Default} value is returned if the field is
	* missing or malformed.
	* @since 1.7
	*/
	public long getHeaderFieldLong(String name, long Default) {
	String value = getHeaderField(name);
	try {
	return Long.parseLong(value);
	} catch (Exception e) { }
	return Default;
	}

	/**
	* Returns the value of the named field parsed as date.
	* The result is the number of milliseconds since January 1, 1970 GMT
	* represented by the named field.
	* <p>
	* This form of {@code getHeaderField} exists because some
	* connection types (e.g., {@code http-ng}) have pre-parsed
	* headers. Classes for that connection type can override this method
	* and short-circuit the parsing.
	*
	* @param name the name of the header field.
	* @param Default a default value.
	* @return the value of the field, parsed as a date. The value of the
	* {@code Default} argument is returned if the field is
	* missing or malformed.
	*/
	@SuppressWarnings("deprecation")
	public long getHeaderFieldDate(String name, long Default) {
	String value = getHeaderField(name);
	try {
	return Date.parse(value);
	} catch (Exception e) { }
	return Default;
	}

	/**
	* Returns the key for the {@code n}<sup>th</sup> header field.
	* It returns {@code null} if there are fewer than {@code n+1} fields.
	*
	* @param n an index, where {@code n>=0}
	* @return the key for the {@code n}<sup>th</sup> header field,
	* or {@code null} if there are fewer than {@code n+1}
	* fields.
	*/
	public String getHeaderFieldKey(int n) {
	return null;
	}

	/**
	* Returns the value for the {@code n}<sup>th</sup> header field.
	* It returns {@code null} if there are fewer than
	* {@code n+1}fields.
	* <p>
	* This method can be used in conjunction with the
	* {@link #getHeaderFieldKey(int) getHeaderFieldKey} method to iterate through all
	* the headers in the message.
	*
	* @param n an index, where {@code n>=0}
	* @return the value of the {@code n}<sup>th</sup> header field
	* or {@code null} if there are fewer than {@code n+1} fields
	* @see java.net.URLConnection#getHeaderFieldKey(int)
	*/
	public String getHeaderField(int n) {
	return null;
	}

	/**
	* Retrieves the contents of this URL connection.
	* <p>
	* This method first determines the content type of the object by
	* calling the {@code getContentType} method. If this is
	* the first time that the application has seen that specific content
	* type, a content handler for that content type is created.
	* <p> This is done as follows:
	* <ol>
	* <li>If the application has set up a content handler factory instance
	* using the {@code setContentHandlerFactory} method, the
	* {@code createContentHandler} method of that instance is called
	* with the content type as an argument; the result is a content
	* handler for that content type.
	* <li>If no {@code ContentHandlerFactory} has yet been set up,
	* or if the factory's {@code createContentHandler} method
	* returns {@code null}, then the {@linkplain java.util.ServiceLoader
	* ServiceLoader} mechanism is used to locate {@linkplain
	* java.net.ContentHandlerFactory ContentHandlerFactory}
	* implementations using the system class
	* loader. The order that factories are located is implementation
	* specific, and an implementation is free to cache the located
	* factories. A {@linkplain java.util.ServiceConfigurationError
	* ServiceConfigurationError}, {@code Error} or {@code RuntimeException}
	* thrown from the {@code createContentHandler}, if encountered, will
	* be propagated to the calling thread. The {@code
	* createContentHandler} method of each factory, if instantiated, is
	* invoked, with the content type, until a factory returns non-null,
	* or all factories have been exhausted.
	* <li>Failing that, this method tries to load a content handler
	* class as defined by {@link java.net.ContentHandler ContentHandler}.
	* If the class does not exist, or is not a subclass of {@code
	* ContentHandler}, then an {@code UnknownServiceException} is thrown.
	* </ol>
	*
	* @return the object fetched. The {@code instanceof} operator
	* should be used to determine the specific kind of object
	* returned.
	* @exception IOException if an I/O error occurs while
	* getting the content.
	* @exception UnknownServiceException if the protocol does not support
	* the content type.
	* @see java.net.ContentHandlerFactory#createContentHandler(java.lang.String)
	* @see java.net.URLConnection#getContentType()
	* @see java.net.URLConnection#setContentHandlerFactory(java.net.ContentHandlerFactory)
	*/
	public Object getContent() throws IOException {
	// Must call getInputStream before GetHeaderField gets called
	// so that FileNotFoundException has a chance to be thrown up
	// from here without being caught.
	getInputStream();
	return getContentHandler().getContent(this);
	}

	/**
	* Retrieves the contents of this URL connection.
	*
	* @param classes the {@code Class} array
	* indicating the requested types
	* @return the object fetched that is the first match of the type
	* specified in the classes array. null if none of
	* the requested types are supported.
	* The {@code instanceof} operator should be used to
	* determine the specific kind of object returned.
	* @exception IOException if an I/O error occurs while
	* getting the content.
	* @exception UnknownServiceException if the protocol does not support
	* the content type.
	* @see java.net.URLConnection#getContent()
	* @see java.net.ContentHandlerFactory#createContentHandler(java.lang.String)
	* @see java.net.URLConnection#getContent(java.lang.Class[])
	* @see java.net.URLConnection#setContentHandlerFactory(java.net.ContentHandlerFactory)
	* @since 1.3
	*/
	public Object getContent(Class<?>[] classes) throws IOException {
	// Must call getInputStream before GetHeaderField gets called
	// so that FileNotFoundException has a chance to be thrown up
	// from here without being caught.
	getInputStream();
	return getContentHandler().getContent(this, classes);
	}

	/**
	* Returns a permission object representing the permission
	* necessary to make the connection represented by this
	* object. This method returns null if no permission is
	* required to make the connection. By default, this method
	* returns {@code java.security.AllPermission}. Subclasses
	* should override this method and return the permission
	* that best represents the permission required to make
	* a connection to the URL. For example, a {@code URLConnection}
	* representing a {@code file:} URL would return a
	* {@code java.io.FilePermission} object.
	*
	* <p>The permission returned may dependent upon the state of the
	* connection. For example, the permission before connecting may be
	* different from that after connecting. For example, an HTTP
	* sever, say foo.com, may redirect the connection to a different
	* host, say bar.com. Before connecting the permission returned by
	* the connection will represent the permission needed to connect
	* to foo.com, while the permission returned after connecting will
	* be to bar.com.
	*
	* <p>Permissions are generally used for two purposes: to protect
	* caches of objects obtained through URLConnections, and to check
	* the right of a recipient to learn about a particular URL. In
	* the first case, the permission should be obtained
	* <em>after</em> the object has been obtained. For example, in an
	* HTTP connection, this will represent the permission to connect
	* to the host from which the data was ultimately fetched. In the
	* second case, the permission should be obtained and tested
	* <em>before</em> connecting.
	*
	* @return the permission object representing the permission
	* necessary to make the connection represented by this
	* URLConnection.
	*
	* @exception IOException if the computation of the permission
	* requires network or file I/O and an exception occurs while
	* computing it.
	*/
	public Permission getPermission() throws IOException {
	return SecurityConstants.ALL_PERMISSION;
	}

	/**
	* Returns an input stream that reads from this open connection.
	*
	* A SocketTimeoutException can be thrown when reading from the
	* returned input stream if the read timeout expires before data
	* is available for read.
	*
	* @return an input stream that reads from this open connection.
	* @exception IOException if an I/O error occurs while
	* creating the input stream.
	* @exception UnknownServiceException if the protocol does not support
	* input.
	* @see #setReadTimeout(int)
	* @see #getReadTimeout()
	*/
	public InputStream getInputStream() throws IOException {
	throw new UnknownServiceException("protocol doesn't support input");
	}

	/**
	* Returns an output stream that writes to this connection.
	*
	* @return an output stream that writes to this connection.
	* @exception IOException if an I/O error occurs while
	* creating the output stream.
	* @exception UnknownServiceException if the protocol does not support
	* output.
	*/
	public OutputStream getOutputStream() throws IOException {
	throw new UnknownServiceException("protocol doesn't support output");
	}

	/**
	* Returns a {@code String} representation of this URL connection.
	*
	* @return a string representation of this {@code URLConnection}.
	*/
	public String toString() {
	return this.getClass().getName() + ":" + url;
	}

	/**
	* Sets the value of the {@code doInput} field for this
	* {@code URLConnection} to the specified value.
	* <p>
	* A URL connection can be used for input and/or output. Set the doInput
	* flag to true if you intend to use the URL connection for input,
	* false if not. The default is true.
	*
	* @param doinput the new value.
	* @throws IllegalStateException if already connected
	* @see java.net.URLConnection#doInput
	* @see #getDoInput()
	*/
	public void setDoInput(boolean doinput) {
	checkConnected();
	doInput = doinput;
	}

	/**
	* Returns the value of this {@code URLConnection}'s
	* {@code doInput} flag.
	*
	* @return the value of this {@code URLConnection}'s
	* {@code doInput} flag.
	* @see #setDoInput(boolean)
	*/
	public boolean getDoInput() {
	return doInput;
	}

	/**
	* Sets the value of the {@code doOutput} field for this
	* {@code URLConnection} to the specified value.
	* <p>
	* A URL connection can be used for input and/or output. Set the doOutput
	* flag to true if you intend to use the URL connection for output,
	* false if not. The default is false.
	*
	* @param dooutput the new value.
	* @throws IllegalStateException if already connected
	* @see #getDoOutput()
	*/
	public void setDoOutput(boolean dooutput) {
	checkConnected();
	doOutput = dooutput;
	}

	/**
	* Returns the value of this {@code URLConnection}'s
	* {@code doOutput} flag.
	*
	* @return the value of this {@code URLConnection}'s
	* {@code doOutput} flag.
	* @see #setDoOutput(boolean)
	*/
	public boolean getDoOutput() {
	return doOutput;
	}

	/**
	* Set the value of the {@code allowUserInteraction} field of
	* this {@code URLConnection}.
	*
	* @param allowuserinteraction the new value.
	* @throws IllegalStateException if already connected
	* @see #getAllowUserInteraction()
	*/
	public void setAllowUserInteraction(boolean allowuserinteraction) {
	checkConnected();
	allowUserInteraction = allowuserinteraction;
	}

	/**
	* Returns the value of the {@code allowUserInteraction} field for
	* this object.
	*
	* @return the value of the {@code allowUserInteraction} field for
	* this object.
	* @see #setAllowUserInteraction(boolean)
	*/
	public boolean getAllowUserInteraction() {
	return allowUserInteraction;
	}

	/**
	* Sets the default value of the
	* {@code allowUserInteraction} field for all future
	* {@code URLConnection} objects to the specified value.
	*
	* @param defaultallowuserinteraction the new value.
	* @see #getDefaultAllowUserInteraction()
	*/
	public static void setDefaultAllowUserInteraction(boolean defaultallowuserinteraction) {
	defaultAllowUserInteraction = defaultallowuserinteraction;
	}

	/**
	* Returns the default value of the {@code allowUserInteraction}
	* field.
	* <p>
	* This default is "sticky", being a part of the static state of all
	* URLConnections. This flag applies to the next, and all following
	* URLConnections that are created.
	*
	* @return the default value of the {@code allowUserInteraction}
	* field.
	* @see #setDefaultAllowUserInteraction(boolean)
	*/
	public static boolean getDefaultAllowUserInteraction() {
	return defaultAllowUserInteraction;
	}

	/**
	* Sets the value of the {@code useCaches} field of this
	* {@code URLConnection} to the specified value.
	* <p>
	* Some protocols do caching of documents. Occasionally, it is important
	* to be able to "tunnel through" and ignore the caches (e.g., the
	* "reload" button in a browser). If the UseCaches flag on a connection
	* is true, the connection is allowed to use whatever caches it can.
	* If false, caches are to be ignored.
	* The default value comes from defaultUseCaches, which defaults to
	* true. A default value can also be set per-protocol using
	* {@link #setDefaultUseCaches(String,boolean)}.
	*
	* @param usecaches a {@code boolean} indicating whether
	* or not to allow caching
	* @throws IllegalStateException if already connected
	* @see #getUseCaches()
	*/
	public void setUseCaches(boolean usecaches) {
	checkConnected();
	useCaches = usecaches;
	}

	/**
	* Returns the value of this {@code URLConnection}'s
	* {@code useCaches} field.
	*
	* @return the value of this {@code URLConnection}'s
	* {@code useCaches} field.
	* @see #setUseCaches(boolean)
	*/
	public boolean getUseCaches() {
	return useCaches;
	}

	/**
	* Sets the value of the {@code ifModifiedSince} field of
	* this {@code URLConnection} to the specified value.
	*
	* @param ifmodifiedsince the new value.
	* @throws IllegalStateException if already connected
	* @see #getIfModifiedSince()
	*/
	public void setIfModifiedSince(long ifmodifiedsince) {
	checkConnected();
	ifModifiedSince = ifmodifiedsince;
	}

	/**
	* Returns the value of this object's {@code ifModifiedSince} field.
	*
	* @return the value of this object's {@code ifModifiedSince} field.
	* @see #setIfModifiedSince(long)
	*/
	public long getIfModifiedSince() {
	return ifModifiedSince;
	}

	/**
	* Returns the default value of a {@code URLConnection}'s
	* {@code useCaches} flag.
	* <p>
	* This default is "sticky", being a part of the static state of all
	* URLConnections. This flag applies to the next, and all following
	* URLConnections that are created. This default value can be over-ridden
	* per protocol using {@link #setDefaultUseCaches(String,boolean)}
	*
	* @return the default value of a {@code URLConnection}'s
	* {@code useCaches} flag.
	* @see #setDefaultUseCaches(boolean)
	*/
	public boolean getDefaultUseCaches() {
	return defaultUseCaches;
	}

	/**
	* Sets the default value of the {@code useCaches} field to the
	* specified value. This default value can be over-ridden
	* per protocol using {@link #setDefaultUseCaches(String,boolean)}
	*
	* @param defaultusecaches the new value.
	* @see #getDefaultUseCaches()
	*/
	public void setDefaultUseCaches(boolean defaultusecaches) {
	defaultUseCaches = defaultusecaches;
	}

	/**
	* Sets the default value of the {@code useCaches} field for the named
	* protocol to the given value. This value overrides any default setting
	* set by {@link #setDefaultUseCaches(boolean)} for the given protocol.
	* Successive calls to this method change the setting and affect the
	* default value for all future connections of that protocol. The protocol
	* name is case insensitive.
	*
	* @param protocol the protocol to set the default for
	* @param defaultVal whether caching is enabled by default for the given protocol
	* @since 9
	*/
	public static void setDefaultUseCaches(String protocol, boolean defaultVal) {
	protocol = protocol.toLowerCase(Locale.US);
	defaultCaching.put(protocol, defaultVal);
	}

	/**
	* Returns the default value of the {@code useCaches} flag for the given protocol. If
	* {@link #setDefaultUseCaches(String,boolean)} was called for the given protocol,
	* then that value is returned. Otherwise, if {@link #setDefaultUseCaches(boolean)}
	* was called, then that value is returned. If neither method was called,
	* the return value is {@code true}. The protocol name is case insensitive.
	*
	* @param protocol the protocol whose defaultUseCaches setting is required
	* @return the default value of the {@code useCaches} flag for the given protocol.
	* @since 9
	*/
	public static boolean getDefaultUseCaches(String protocol) {
	Boolean protoDefault = defaultCaching.get(protocol.toLowerCase(Locale.US));
	if (protoDefault != null) {
	return protoDefault.booleanValue();
	} else {
	return defaultUseCaches;
	}
	}

	/**
	* Sets the general request property. If a property with the key already
	* exists, overwrite its value with the new value.
	*
	* <p> NOTE: HTTP requires all request properties which can
	* legally have multiple instances with the same key
	* to use a comma-separated list syntax which enables multiple
	* properties to be appended into a single property.
	*
	* @param key the keyword by which the request is known
	* (e.g., "{@code Accept}").
	* @param value the value associated with it.
	* @throws IllegalStateException if already connected
	* @throws NullPointerException if key is {@code null}
	* @see #getRequestProperty(java.lang.String)
	*/
	public void setRequestProperty(String key, String value) {
	checkConnected();
	if (key == null)
	throw new NullPointerException ("key is null");

	if (requests == null)
	requests = new MessageHeader();

	requests.set(key, value);
	}

	/**
	* Adds a general request property specified by a
	* key-value pair. This method will not overwrite
	* existing values associated with the same key.
	*
	* @param key the keyword by which the request is known
	* (e.g., "{@code Accept}").
	* @param value the value associated with it.
	* @throws IllegalStateException if already connected
	* @throws NullPointerException if key is null
	* @see #getRequestProperties()
	* @since 1.4
	*/
	public void addRequestProperty(String key, String value) {
	checkConnected();
	if (key == null)
	throw new NullPointerException ("key is null");

	if (requests == null)
	requests = new MessageHeader();

	requests.add(key, value);
	}


	/**
	* Returns the value of the named general request property for this
	* connection.
	*
	* @param key the keyword by which the request is known (e.g., "Accept").
	* @return the value of the named general request property for this
	* connection. If key is null, then null is returned.
	* @throws IllegalStateException if already connected
	* @see #setRequestProperty(java.lang.String, java.lang.String)
	*/
	public String getRequestProperty(String key) {
	checkConnected();

	if (requests == null)
	return null;

	return requests.findValue(key);
	}

	/**
	* Returns an unmodifiable Map of general request
	* properties for this connection. The Map keys
	* are Strings that represent the request-header
	* field names. Each Map value is a unmodifiable List
	* of Strings that represents the corresponding
	* field values.
	*
	* @return a Map of the general request properties for this connection.
	* @throws IllegalStateException if already connected
	* @since 1.4
	*/
	public Map<String,List<String>> getRequestProperties() {
	checkConnected();

	if (requests == null)
	return Collections.emptyMap();

	return requests.getHeaders(null);
	}

	/**
	* Sets the default value of a general request property. When a
	* {@code URLConnection} is created, it is initialized with
	* these properties.
	*
	* @param key the keyword by which the request is known
	* (e.g., "{@code Accept}").
	* @param value the value associated with the key.
	*
	* @see java.net.URLConnection#setRequestProperty(java.lang.String,java.lang.String)
	*
	* @deprecated The instance specific setRequestProperty method
	* should be used after an appropriate instance of URLConnection
	* is obtained. Invoking this method will have no effect.
	*
	* @see #getDefaultRequestProperty(java.lang.String)
	*/
	@Deprecated
	public static void setDefaultRequestProperty(String key, String value) {
	}

	/**
	* Returns the value of the default request property. Default request
	* properties are set for every connection.
	*
	* @param key the keyword by which the request is known (e.g., "Accept").
	* @return the value of the default request property
	* for the specified key.
	*
	* @see java.net.URLConnection#getRequestProperty(java.lang.String)
	*
	* @deprecated The instance specific getRequestProperty method
	* should be used after an appropriate instance of URLConnection
	* is obtained.
	*
	* @see #setDefaultRequestProperty(java.lang.String, java.lang.String)
	*/
	@Deprecated
	public static String getDefaultRequestProperty(String key) {
	return null;
	}

	/**
	* The ContentHandler factory.
	*/
	private static volatile ContentHandlerFactory factory;

	/**
	* Sets the {@code ContentHandlerFactory} of an
	* application. It can be called at most once by an application.
	* <p>
	* The {@code ContentHandlerFactory} instance is used to
	* construct a content handler from a content type.
	* <p>
	* If there is a security manager, this method first calls
	* the security manager's {@code checkSetFactory} method
	* to ensure the operation is allowed.
	* This could result in a SecurityException.
	*
	* @param fac the desired factory.
	* @exception Error if the factory has already been defined.
	* @exception SecurityException if a security manager exists and its
	* {@code checkSetFactory} method doesn't allow the operation.
	* @see java.net.ContentHandlerFactory
	* @see java.net.URLConnection#getContent()
	* @see SecurityManager#checkSetFactory
	*/
	public static synchronized void setContentHandlerFactory(ContentHandlerFactory fac) {
	if (factory != null) {
	throw new Error("factory already defined");
	}
	SecurityManager security = System.getSecurityManager();
	if (security != null) {
	security.checkSetFactory();
	}
	factory = fac;
	}

	private static final Hashtable<String, ContentHandler> handlers = new Hashtable<>();

	/**
	* Gets the Content Handler appropriate for this connection.
	*/
	private ContentHandler getContentHandler() throws UnknownServiceException {
	String contentType = stripOffParameters(getContentType());
	if (contentType == null) {
	throw new UnknownServiceException("no content-type");
	}

	ContentHandler handler = handlers.get(contentType);
	if (handler != null)
	return handler;

	if (factory != null) {
	handler = factory.createContentHandler(contentType);
	if (handler != null)
	return handler;
	}

	handler = lookupContentHandlerViaProvider(contentType);

	if (handler != null) {
	ContentHandler h = handlers.putIfAbsent(contentType, handler);
	return Objects.requireNonNullElse(h, handler);
	}

	try {
	handler = lookupContentHandlerClassFor(contentType);
	} catch (Exception e) {
	e.printStackTrace();
	handler = UnknownContentHandler.INSTANCE;
	}

	assert handler != null;

	ContentHandler h = handlers.putIfAbsent(contentType, handler);
	return Objects.requireNonNullElse(h, handler);
	}

	/*
	* Media types are in the format: type/subtype*(; parameter).
	* For looking up the content handler, we should ignore those
	* parameters.
	*/
	private String stripOffParameters(String contentType)
	{
	if (contentType == null)
	return null;
	int index = contentType.indexOf(';');

	if (index > 0)
	return contentType.substring(0, index);
	else
	return contentType;
	}

	private static final String contentClassPrefix = "sun.net.www.content";
	private static final String contentPathProp = "java.content.handler.pkgs";

	/**
	* Looks for a content handler in a user-definable set of places.
	* By default it looks in {@value #contentClassPrefix}, but users can define
	* a vertical-bar delimited set of class prefixes to search through in
	* addition by defining the {@value #contentPathProp} property.
	* The class name must be of the form:
	* <pre>
	* {package-prefix}.{major}.{minor}
	* e.g.
	* YoyoDyne.experimental.text.plain
	* </pre>
	*/
	private ContentHandler lookupContentHandlerClassFor(String contentType) {
	String contentHandlerClassName = typeToPackageName(contentType);

	String contentHandlerPkgPrefixes = getContentHandlerPkgPrefixes();

	StringTokenizer packagePrefixIter =
	new StringTokenizer(contentHandlerPkgPrefixes, "\|");

	while (packagePrefixIter.hasMoreTokens()) {
	String packagePrefix = packagePrefixIter.nextToken().trim();

	try {
	String clsName = packagePrefix + "." + contentHandlerClassName;
	Class<?> cls = null;
	try {
	cls = Class.forName(clsName);
	} catch (ClassNotFoundException e) {
	ClassLoader cl = ClassLoader.getSystemClassLoader();
	if (cl != null) {
	cls = cl.loadClass(clsName);
	}
	}
	if (cls != null) {
	@SuppressWarnings("deprecation")
	Object tmp = cls.newInstance();
	return (ContentHandler) tmp;
	}
	} catch(Exception ignored) { }
	}

	return UnknownContentHandler.INSTANCE;
	}

	private ContentHandler lookupContentHandlerViaProvider(String contentType) {
	return AccessController.doPrivileged(
	new PrivilegedAction<>() {
	@Override
	public ContentHandler run() {
	ClassLoader cl = ClassLoader.getSystemClassLoader();
	ServiceLoader<ContentHandlerFactory> sl =
	ServiceLoader.load(ContentHandlerFactory.class, cl);

	Iterator<ContentHandlerFactory> iterator = sl.iterator();

	ContentHandler handler = null;
	while (iterator.hasNext()) {
	ContentHandlerFactory f;
	try {
	f = iterator.next();
	} catch (ServiceConfigurationError e) {
	if (e.getCause() instanceof SecurityException) {
	continue;
	}
	throw e;
	}
	handler = f.createContentHandler(contentType);
	if (handler != null) {
	break;
	}
	}
	return handler;
	}
	});
	}

	/**
	* Utility function to map a MIME content type into an equivalent
	* pair of class name components. For example: "text/html" would
	* be returned as "text.html"
	*/
	private String typeToPackageName(String contentType) {
	// make sure we canonicalize the class name: all lower case
	contentType = contentType.toLowerCase();
	int len = contentType.length();
	char nm[] = new char[len];
	contentType.getChars(0, len, nm, 0);
	for (int i = 0; i < len; i++) {
	char c = nm[i];
	if (c == '/') {
	nm[i] = '.';
	} else if (!('A' <= c && c <= 'Z' \|\|
	'a' <= c && c <= 'z' \|\|
	'0' <= c && c <= '9')) {
	nm[i] = '_';
	}
	}
	return new String(nm);
	}


	/**
	* Returns a vertical bar separated list of package prefixes for potential
	* content handlers. Tries to get the java.content.handler.pkgs property
	* to use as a set of package prefixes to search. Whether or not
	* that property has been defined, the {@value #contentClassPrefix}
	* is always the last one on the returned package list.
	*/
	private String getContentHandlerPkgPrefixes() {
	String packagePrefixList =
	GetPropertyAction.privilegedGetProperty(contentPathProp, "");

	if (packagePrefixList != "") {
	packagePrefixList += "\|";
	}

	return packagePrefixList + contentClassPrefix;
	}

	/**
	* Tries to determine the content type of an object, based
	* on the specified "file" component of a URL.
	* This is a convenience method that can be used by
	* subclasses that override the {@code getContentType} method.
	*
	* @param fname a filename.
	* @return a guess as to what the content type of the object is,
	* based upon its file name.
	* @see java.net.URLConnection#getContentType()
	*/
	public static String guessContentTypeFromName(String fname) {
	return getFileNameMap().getContentTypeFor(fname);
	}

	/**
	* Tries to determine the type of an input stream based on the
	* characters at the beginning of the input stream. This method can
	* be used by subclasses that override the
	* {@code getContentType} method.
	* <p>
	* Ideally, this routine would not be needed. But many
	* {@code http} servers return the incorrect content type; in
	* addition, there are many nonstandard extensions. Direct inspection
	* of the bytes to determine the content type is often more accurate
	* than believing the content type claimed by the {@code http} server.
	*
	* @param is an input stream that supports marks.
	* @return a guess at the content type, or {@code null} if none
	* can be determined.
	* @exception IOException if an I/O error occurs while reading the
	* input stream.
	* @see java.io.InputStream#mark(int)
	* @see java.io.InputStream#markSupported()
	* @see java.net.URLConnection#getContentType()
	*/
	public static String guessContentTypeFromStream(InputStream is)
	throws IOException {
	// If we can't read ahead safely, just give up on guessing
	if (!is.markSupported())
	return null;

	is.mark(16);
	int c1 = is.read();
	int c2 = is.read();
	int c3 = is.read();
	int c4 = is.read();
	int c5 = is.read();
	int c6 = is.read();
	int c7 = is.read();
	int c8 = is.read();
	int c9 = is.read();
	int c10 = is.read();
	int c11 = is.read();
	int c12 = is.read();
	int c13 = is.read();
	int c14 = is.read();
	int c15 = is.read();
	int c16 = is.read();
	is.reset();

	if (c1 == 0xCA && c2 == 0xFE && c3 == 0xBA && c4 == 0xBE) {
	return "application/java-vm";
	}

	if (c1 == 0xAC && c2 == 0xED) {
	// next two bytes are version number, currently 0x00 0x05
	return "application/x-java-serialized-object";
	}

	if (c1 == '<') {
	if (c2 == '!'
	\|\| ((c2 == 'h' && (c3 == 't' && c4 == 'm' && c5 == 'l' \|\|
	c3 == 'e' && c4 == 'a' && c5 == 'd') \|\|
	(c2 == 'b' && c3 == 'o' && c4 == 'd' && c5 == 'y'))) \|\|
	((c2 == 'H' && (c3 == 'T' && c4 == 'M' && c5 == 'L' \|\|
	c3 == 'E' && c4 == 'A' && c5 == 'D') \|\|
	(c2 == 'B' && c3 == 'O' && c4 == 'D' && c5 == 'Y')))) {
	return "text/html";
	}

	if (c2 == '?' && c3 == 'x' && c4 == 'm' && c5 == 'l' && c6 == ' ') {
	return "application/xml";
	}
	}

	// big and little (identical) endian UTF-8 encodings, with BOM
	if (c1 == 0xef && c2 == 0xbb && c3 == 0xbf) {
	if (c4 == '<' && c5 == '?' && c6 == 'x') {
	return "application/xml";
	}
	}

	// big and little endian UTF-16 encodings, with byte order mark
	if (c1 == 0xfe && c2 == 0xff) {
	if (c3 == 0 && c4 == '<' && c5 == 0 && c6 == '?' &&
	c7 == 0 && c8 == 'x') {
	return "application/xml";
	}
	}

	if (c1 == 0xff && c2 == 0xfe) {
	if (c3 == '<' && c4 == 0 && c5 == '?' && c6 == 0 &&
	c7 == 'x' && c8 == 0) {
	return "application/xml";
	}
	}

	// big and little endian UTF-32 encodings, with BOM
	if (c1 == 0x00 && c2 == 0x00 && c3 == 0xfe && c4 == 0xff) {
	if (c5 == 0 && c6 == 0 && c7 == 0 && c8 == '<' &&
	c9 == 0 && c10 == 0 && c11 == 0 && c12 == '?' &&
	c13 == 0 && c14 == 0 && c15 == 0 && c16 == 'x') {
	return "application/xml";
	}
	}

	if (c1 == 0xff && c2 == 0xfe && c3 == 0x00 && c4 == 0x00) {
	if (c5 == '<' && c6 == 0 && c7 == 0 && c8 == 0 &&
	c9 == '?' && c10 == 0 && c11 == 0 && c12 == 0 &&
	c13 == 'x' && c14 == 0 && c15 == 0 && c16 == 0) {
	return "application/xml";
	}
	}

	if (c1 == 'G' && c2 == 'I' && c3 == 'F' && c4 == '8') {
	return "image/gif";
	}

	if (c1 == '#' && c2 == 'd' && c3 == 'e' && c4 == 'f') {
	return "image/x-bitmap";
	}

	if (c1 == '!' && c2 == ' ' && c3 == 'X' && c4 == 'P' &&
	c5 == 'M' && c6 == '2') {
	return "image/x-pixmap";
	}

	if (c1 == 137 && c2 == 80 && c3 == 78 &&
	c4 == 71 && c5 == 13 && c6 == 10 &&
	c7 == 26 && c8 == 10) {
	return "image/png";
	}

	if (c1 == 0xFF && c2 == 0xD8 && c3 == 0xFF) {
	if (c4 == 0xE0 \|\| c4 == 0xEE) {
	return "image/jpeg";
	}

	/**
	* File format used by digital cameras to store images.
	* Exif Format can be read by any application supporting
	* JPEG. Exif Spec can be found at:
	* http://www.pima.net/standards/it10/PIMA15740/Exif_2-1.PDF
	*/
	if ((c4 == 0xE1) &&
	(c7 == 'E' && c8 == 'x' && c9 == 'i' && c10 =='f' &&
	c11 == 0)) {
	return "image/jpeg";
	}
	}

	if ((c1 == 0x49 && c2 == 0x49 && c3 == 0x2a && c4 == 0x00)
	\|\| (c1 == 0x4d && c2 == 0x4d && c3 == 0x00 && c4 == 0x2a)) {
	return "image/tiff";
	}

	if (c1 == 0xD0 && c2 == 0xCF && c3 == 0x11 && c4 == 0xE0 &&
	c5 == 0xA1 && c6 == 0xB1 && c7 == 0x1A && c8 == 0xE1) {

	/* Above is signature of Microsoft Structured Storage.
	* Below this, could have tests for various SS entities.
	* For now, just test for FlashPix.
	*/
	if (checkfpx(is)) {
	return "image/vnd.fpx";
	}
	}

	if (c1 == 0x2E && c2 == 0x73 && c3 == 0x6E && c4 == 0x64) {
	return "audio/basic"; // .au format, big endian
	}

	if (c1 == 0x64 && c2 == 0x6E && c3 == 0x73 && c4 == 0x2E) {
	return "audio/basic"; // .au format, little endian
	}

	if (c1 == 'R' && c2 == 'I' && c3 == 'F' && c4 == 'F') {
	/* I don't know if this is official but evidence
	* suggests that .wav files start with "RIFF" - brown
	*/
	return "audio/x-wav";
	}
	return null;
	}

	/**
	* Check for FlashPix image data in InputStream is. Return true if
	* the stream has FlashPix data, false otherwise. Before calling this
	* method, the stream should have already been checked to be sure it
	* contains Microsoft Structured Storage data.
	*/
	private static boolean checkfpx(InputStream is) throws IOException {

	/* Test for FlashPix image data in Microsoft Structured Storage format.
	* In general, should do this with calls to an SS implementation.
	* Lacking that, need to dig via offsets to get to the FlashPix
	* ClassID. Details:
	*
	* Offset to Fpx ClsID from beginning of stream should be:
	*
	* FpxClsidOffset = rootEntryOffset + clsidOffset
	*
	* where: clsidOffset = 0x50.
	* rootEntryOffset = headerSize + sectorSize*sectDirStart
	* + 128*rootEntryDirectory
	*
	* where: headerSize = 0x200 (always)
	* sectorSize = 2 raised to power of uSectorShift,
	* which is found in the header at
	* offset 0x1E.
	* sectDirStart = found in the header at offset 0x30.
	* rootEntryDirectory = in general, should search for
	* directory labelled as root.
	* We will assume value of 0 (i.e.,
	* rootEntry is in first directory)
	*/

	// Mark the stream so we can reset it. 0x100 is enough for the first
	// few reads, but the mark will have to be reset and set again once
	// the offset to the root directory entry is computed. That offset
	// can be very large and isn't know until the stream has been read from
	is.mark(0x100);

	// Get the byte ordering located at 0x1E. 0xFE is Intel,
	// 0xFF is other
	long toSkip = (long)0x1C;
	long posn;

	if ((posn = skipForward(is, toSkip)) < toSkip) {
	is.reset();
	return false;
	}

	int c[] = new int[16];
	if (readBytes(c, 2, is) < 0) {
	is.reset();
	return false;
	}

	int byteOrder = c[0];

	posn+=2;
	int uSectorShift;
	if (readBytes(c, 2, is) < 0) {
	is.reset();
	return false;
	}

	if(byteOrder == 0xFE) {
	uSectorShift = c[0];
	uSectorShift += c[1] << 8;
	}
	else {
	uSectorShift = c[0] << 8;
	uSectorShift += c[1];
	}

	posn += 2;
	toSkip = (long)0x30 - posn;
	long skipped = 0;
	if ((skipped = skipForward(is, toSkip)) < toSkip) {
	is.reset();
	return false;
	}
	posn += skipped;

	if (readBytes(c, 4, is) < 0) {
	is.reset();
	return false;
	}

	int sectDirStart;
	if(byteOrder == 0xFE) {
	sectDirStart = c[0];
	sectDirStart += c[1] << 8;
	sectDirStart += c[2] << 16;
	sectDirStart += c[3] << 24;
	} else {
	sectDirStart = c[0] << 24;
	sectDirStart += c[1] << 16;
	sectDirStart += c[2] << 8;
	sectDirStart += c[3];
	}
	posn += 4;
	is.reset(); // Reset back to the beginning

	toSkip = 0x200L + (long)(1<<uSectorShift)*sectDirStart + 0x50L;

	// Sanity check!
	if (toSkip < 0) {
	return false;
	}

	/*
	* How far can we skip? Is there any performance problem here?
	* This skip can be fairly long, at least 0x4c650 in at least
	* one case. Have to assume that the skip will fit in an int.
	* Leave room to read whole root dir
	*/
	is.mark((int)toSkip+0x30);

	if ((skipForward(is, toSkip)) < toSkip) {
	is.reset();
	return false;
	}

	/* should be at beginning of ClassID, which is as follows
	* (in Intel byte order):
	* 00 67 61 56 54 C1 CE 11 85 53 00 AA 00 A1 F9 5B
	*
	* This is stored from Windows as long,short,short,char[8]
	* so for byte order changes, the order only changes for
	* the first 8 bytes in the ClassID.
	*
	* Test against this, ignoring second byte (Intel) since
	* this could change depending on part of Fpx file we have.
	*/

	if (readBytes(c, 16, is) < 0) {
	is.reset();
	return false;
	}

	// intel byte order
	if (byteOrder == 0xFE &&
	c[0] == 0x00 && c[2] == 0x61 && c[3] == 0x56 &&
	c[4] == 0x54 && c[5] == 0xC1 && c[6] == 0xCE &&
	c[7] == 0x11 && c[8] == 0x85 && c[9] == 0x53 &&
	c[10]== 0x00 && c[11]== 0xAA && c[12]== 0x00 &&
	c[13]== 0xA1 && c[14]== 0xF9 && c[15]== 0x5B) {
	is.reset();
	return true;
	}

	// non-intel byte order
	else if (c[3] == 0x00 && c[1] == 0x61 && c[0] == 0x56 &&
	c[5] == 0x54 && c[4] == 0xC1 && c[7] == 0xCE &&
	c[6] == 0x11 && c[8] == 0x85 && c[9] == 0x53 &&
	c[10]== 0x00 && c[11]== 0xAA && c[12]== 0x00 &&
	c[13]== 0xA1 && c[14]== 0xF9 && c[15]== 0x5B) {
	is.reset();
	return true;
	}
	is.reset();
	return false;
	}

	/**
	* Tries to read the specified number of bytes from the stream
	* Returns -1, If EOF is reached before len bytes are read, returns 0
	* otherwise
	*/
	private static int readBytes(int c[], int len, InputStream is)
	throws IOException {

	byte buf[] = new byte[len];
	if (is.read(buf, 0, len) < len) {
	return -1;
	}

	// fill the passed in int array
	for (int i = 0; i < len; i++) {
	c[i] = buf[i] & 0xff;
	}
	return 0;
	}


	/**
	* Skips through the specified number of bytes from the stream
	* until either EOF is reached, or the specified
	* number of bytes have been skipped
	*/
	private static long skipForward(InputStream is, long toSkip)
	throws IOException {

	long eachSkip = 0;
	long skipped = 0;

	while (skipped != toSkip) {
	eachSkip = is.skip(toSkip - skipped);

	// check if EOF is reached
	if (eachSkip <= 0) {
	if (is.read() == -1) {
	return skipped ;
	} else {
	skipped++;
	}
	}
	skipped += eachSkip;
	}
	return skipped;
	}

	private void checkConnected() {
	if (connected)
	throw new IllegalStateException("Already connected");
	}
	}

	class UnknownContentHandler extends ContentHandler {
	static final ContentHandler INSTANCE = new UnknownContentHandler();

	public Object getContent(URLConnection uc) throws IOException {
	return uc.getInputStream();
	}
	}

Back to index...