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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

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 * 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

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package jdk.jfr;

import java.security.AccessController;

import java.util.Set;

import jdk.jfr.internal.Control;

/**

 * Base class to extend to create setting controls.

 * <p>

 * The following example shows a naive implementation of a setting control for

 * regular expressions:

 *

 * <pre>

 * <code>

 * final class RegExpControl extends SettingControl {

 *   private Pattern pattern = Pattern.compile(".*");

 *

 *   {@literal @}Override

 *   public void setValue(String value) {

 *     this.pattern = Pattern.compile(value);

 *   }

 *

 *   {@literal @}Override

 *   public String combine(Set{@literal <}String{@literal >} values) {

 *     return String.join("|", values);

 *   }

 *

 *   {@literal @}Override

 *   public String getValue() {

 *     return pattern.toString();

 *   }

 *

 *   public String matches(String s) {

 *     return pattern.matcher(s).find();

 *   }

 * }

 * </code>

 * </pre>

 *

 * The {@code setValue(String)}, {@code getValue()} and

 * {@code combine(Set<String>)} methods are invoked when a setting value

 * changes, which typically happens when a recording is started or stopped. The

 * {@code combine(Set<String>)} method is invoked to resolve what value to use

 * when multiple recordings are running at the same time.

 * <p>

 * The setting control must have a default constructor that can be invoked when

 * the event is registered.

 * <p>

 * To use a setting control with an event, add a method that returns a

 * {@code boolean} value and takes the setting control as a parameter. Annotate

 * the method with the {@code @SettingDefinition} annotation. By default, the

 * method name is used as the setting name, but the name can be set explicitly

 * by using the {@code @Name} annotation. If the method returns {@code true},

 * the event will be committed.

 * <p>

 * It is recommended that the {@code setValue(String)} method updates an

 * efficient data structure that can be quickly checked when the event is

 * committed.

 * <p>

 * The following example shows how to create an event that uses the

 * regular expression filter defined above.

 *

 * <pre>

 * <code>

 * abstract class HTTPRequest extends Event {

 *   {@literal @}Label("Request URI")

 *   protected String uri;

 *

 *   {@literal @}Label("Servlet URI Filter")

 *   {@literal @}SettingDefinition

 *   protected boolean uriFilter(RegExpControl regExp) {

 *     return regExp.matches(uri);

 *   }

 * }

 *

 * {@literal @}Label("HTTP Get Request")

 * class HTTPGetRequest extends HTTPRequest {

 * }

 *

 * {@literal @}Label("HTTP Post Request")

 * class HTTPPostRequest extends HTTPRequest {

 * }

 *

 * class ExampleServlet extends HTTPServlet {

 *   protected void doGet(HttpServletRequest req, HttpServletResponse resp) {

 *     HTTPGetRequest request = new HTTPGetRequest();

 *     request.begin();

 *     request.uri = req.getRequestURI();

 *     ...

 *     request.commit();

 *   }

 *

 *   protected void doPost(HttpServletRequest req, HttpServletResponse resp) {

 *     HTTPPostRequest request = new HTTPPostRequest();

 *     request.begin();

 *     request.uri = req.getRequestURI();

 *     ...

 *     request.commit();

 *   }

 * }

 * </code>

 * </pre>

 *

 * The following example shows how an event can be filtered by assigning the

 * {@code "uriFilter"} setting with the specified regular expressions.

 *

 * <pre>

 * <code>

 * Recording r = new Recording();

 * r.enable("HTTPGetRequest").with("uriFilter", "https://www.example.com/list/.*");

 * r.enable("HTTPPostRequest").with("uriFilter", "https://www.example.com/login/.*");

 * r.start();

 * </code>

 * </pre>

 *

 *

 *

 * @see SettingDefinition

 *

 * @since 8

 */

@MetadataDefinition

public abstract class SettingControl extends Control {

    /**

     * Constructor for invocation by subclass constructors.

     */

    protected SettingControl() {

        super(AccessController.getContext());

    }

    /**

     * Combines the setting values for all running recordings into one value when

     * multiple recordings are running at the same time,

     * <p>

     * The semantics of how setting values are combined depends on the setting

     * control that is implemented, but all recordings should get at least all the

     * events they request.

     * <p>

     * This method should have no side effects, because the caller might cache values.

     * This method should never return {@code null} or throw an exception. If a

     * value is not valid for this setting control, the value should be ignored.

     * <p>

     * Examples:

     * <p>

     * if the setting control represents a threshold and three recordings are

     * running at the same time with the setting values {@code "10 ms"},

     * {@code "8 s"}, and {@code  "1 ms"}, this method returns {@code "1 ms"}

     * because it means that all recordings get at least all the requested data.

     * <p>

     * If the setting control represents a set of names and two recordings are

     * running at the same time with the setting values {@code "Smith, Jones"} and {@code "Jones,

     * Williams"} the returned value is {@code "Smith, Jones, Williams"} because all names would be accepted.

     * <p>

     * If the setting control represents a boolean condition and four recordings are

     * running at the same time with the following values {@code "true"}, {@code "false"}, {@code "false"}, and

     * {@code "incorrect"}, this method returns {@code "true"}, because all

     * recordings get at least all the requested data.

     *

     * @param settingValues the set of values, not {@code null}

     *

     * @return the value to use, not {@code null}

     */

    @Override

    public abstract String combine(Set<String> settingValues);

    /**

     * Sets the value for this setting.

     * <p>

     * If the setting value is not valid for this setting, this method

     * does not throw an exception. Instead, the value is ignored.

     *

     * @param settingValue the string value, not {@code null}

     */

    @Override

    public abstract void setValue(String settingValue);

    /**

     * Returns the currently used value for this setting, not {@code null}.

     * <p>

     * The value returned by this method is valid as an argument to both

     * the {@code setValue(String)} method and {@code combine(Set)} method.

     * <p>

     * This method is invoked when an event is registered to obtain the

     * default value. It is therefore important that a valid value can be

     * returned immediately after an instance of this class is created. It is

     * not valid to return {@code null}.

     *

     * @return the setting value, not {@code null}

     */

    @Override

    public abstract String getValue();

}