Back to index...

	/*
	* Copyright (c) 2013, 2021, 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.lang.reflect;

	import java.lang.annotation.*;
	import java.util.HashMap;
	import java.util.Map;
	import java.util.Objects;
	import sun.reflect.annotation.AnnotationSupport;

	/**
	* Information about method parameters.
	*
	* A {@code Parameter} provides information about method parameters,
	* including its name and modifiers. It also provides an alternate
	* means of obtaining attributes for the parameter.
	*
	* @since 1.8
	*/
	public final class Parameter implements AnnotatedElement {

	private final String name;
	private final int modifiers;
	private final Executable executable;
	private final int index;

	/**
	* Package-private constructor for {@code Parameter}.
	*
	* If method parameter data is present in the classfile, then the
	* JVM creates {@code Parameter} objects directly. If it is
	* absent, however, then {@code Executable} uses this constructor
	* to synthesize them.
	*
	* @param name The name of the parameter.
	* @param modifiers The modifier flags for the parameter.
	* @param executable The executable which defines this parameter.
	* @param index The index of the parameter.
	*/
	Parameter(String name,
	int modifiers,
	Executable executable,
	int index) {
	this.name = name;
	this.modifiers = modifiers;
	this.executable = executable;
	this.index = index;
	}

	/**
	* Compares based on the executable and the index.
	*
	* @param obj The object to compare.
	* @return Whether or not this is equal to the argument.
	*/
	@Override
	public boolean equals(Object obj) {
	return (obj instanceof Parameter other)
	&& other.executable.equals(executable)
	&& other.index == index;
	}

	/**
	* Returns a hash code based on the executable's hash code and the
	* index.
	*
	* @return A hash code based on the executable's hash code.
	*/
	@Override
	public int hashCode() {
	return executable.hashCode() ^ index;
	}

	/**
	* Returns true if the parameter has a name according to the class
	* file; returns false otherwise. Whether a parameter has a name
	* is determined by the {@literal MethodParameters} attribute of
	* the method which declares the parameter.
	*
	* @return true if and only if the parameter has a name according
	* to the class file.
	*/
	public boolean isNamePresent() {
	return executable.hasRealParameterData() && name != null;
	}

	/**
	* Returns a string describing this parameter. The format is the
	* modifiers for the parameter, if any, in canonical order as
	* recommended by <cite>The Java Language
	* Specification</cite>, followed by the fully-qualified type of
	* the parameter (excluding the last [] if the parameter is
	* variable arity), followed by "..." if the parameter is variable
	* arity, followed by a space, followed by the name of the
	* parameter.
	*
	* @return A string representation of the parameter and associated
	* information.
	*/
	@Override
	public String toString() {
	final StringBuilder sb = new StringBuilder();
	final Type type = getParameterizedType();
	final String typename = type.getTypeName();

	sb.append(Modifier.toString(getModifiers()));

	if(0 != modifiers)
	sb.append(' ');

	if(isVarArgs())
	sb.append(typename.replaceFirst("\\[\\]$", "..."));
	else
	sb.append(typename);

	sb.append(' ');
	sb.append(getName());

	return sb.toString();
	}

	/**
	* {@return the {@code Executable} declaring this parameter}
	*/
	public Executable getDeclaringExecutable() {
	return executable;
	}

	/**
	* {@return the Java language {@linkplain Modifier modifiers} for
	* the parameter represented by this object}
	*
	* @jls 8.4.1 Formal Parameters
	* @see <a
	* href="{@docRoot}/java.base/java/lang/reflect/package-summary.html#LanguageJvmModel">Java
	* programming language and JVM modeling in core reflection</a>
	*/
	public int getModifiers() {
	return modifiers;
	}

	/**
	* Returns the name of the parameter. If the parameter's name is
	* {@linkplain #isNamePresent() present}, then this method returns
	* the name provided by the class file. Otherwise, this method
	* synthesizes a name of the form argN, where N is the index of
	* the parameter in the descriptor of the method which declares
	* the parameter.
	*
	* @return The name of the parameter, either provided by the class
	* file or synthesized if the class file does not provide
	* a name.
	*/
	public String getName() {
	// Note: empty strings as parameter names are now outlawed.
	// The .isEmpty() is for compatibility with current JVM
	// behavior. It may be removed at some point.
	if(name == null \|\| name.isEmpty())
	return "arg" + index;
	else
	return name;
	}

	// Package-private accessor to the real name field.
	String getRealName() {
	return name;
	}

	/**
	* Returns a {@code Type} object that identifies the parameterized
	* type for the parameter represented by this {@code Parameter}
	* object.
	*
	* @return a {@code Type} object identifying the parameterized
	* type of the parameter represented by this object
	*/
	public Type getParameterizedType() {
	Type tmp = parameterTypeCache;
	if (null == tmp) {
	tmp = executable.getAllGenericParameterTypes()[index];
	parameterTypeCache = tmp;
	}

	return tmp;
	}

	private transient volatile Type parameterTypeCache;

	/**
	* Returns a {@code Class} object that identifies the
	* declared type for the parameter represented by this
	* {@code Parameter} object.
	*
	* @return a {@code Class} object identifying the declared
	* type of the parameter represented by this object
	*/
	public Class<?> getType() {
	Class<?> tmp = parameterClassCache;
	if (null == tmp) {
	tmp = executable.getParameterTypes()[index];
	parameterClassCache = tmp;
	}
	return tmp;
	}

	/**
	* Returns an AnnotatedType object that represents the use of a type to
	* specify the type of the formal parameter represented by this Parameter.
	*
	* @return an {@code AnnotatedType} object representing the use of a type
	* to specify the type of the formal parameter represented by this
	* Parameter
	*/
	public AnnotatedType getAnnotatedType() {
	// no caching for now
	return executable.getAnnotatedParameterTypes()[index];
	}

	private transient volatile Class<?> parameterClassCache;

	/**
	* Returns {@code true} if this parameter is implicitly declared
	* in source code; returns {@code false} otherwise.
	*
	* @return true if and only if this parameter is implicitly
	* declared as defined by <cite>The Java Language
	* Specification</cite>.
	*/
	public boolean isImplicit() {
	return Modifier.isMandated(getModifiers());
	}

	/**
	* Returns {@code true} if this parameter is neither implicitly
	* nor explicitly declared in source code; returns {@code false}
	* otherwise.
	*
	* @return true if and only if this parameter is a synthetic
	* construct as defined by
	* <cite>The Java Language Specification</cite>.
	* @jls 13.1 The Form of a Binary
	* @see <a
	* href="{@docRoot}/java.base/java/lang/reflect/package-summary.html#LanguageJvmModel">Java
	* programming language and JVM modeling in core reflection</a>
	*/
	public boolean isSynthetic() {
	return Modifier.isSynthetic(getModifiers());
	}

	/**
	* Returns {@code true} if this parameter represents a variable
	* argument list; returns {@code false} otherwise.
	*
	* @return {@code true} if an only if this parameter represents a
	* variable argument list.
	*/
	public boolean isVarArgs() {
	return executable.isVarArgs() &&
	index == executable.getParameterCount() - 1;
	}


	/**
	* {@inheritDoc}
	* <p>Note that any annotation returned by this method is a
	* declaration annotation.
	* @throws NullPointerException {@inheritDoc}
	*/
	@Override
	public <T extends Annotation> T getAnnotation(Class<T> annotationClass) {
	Objects.requireNonNull(annotationClass);
	return annotationClass.cast(declaredAnnotations().get(annotationClass));
	}

	/**
	* {@inheritDoc}
	* <p>Note that any annotations returned by this method are
	* declaration annotations.
	*
	* @throws NullPointerException {@inheritDoc}
	*/
	@Override
	public <T extends Annotation> T[] getAnnotationsByType(Class<T> annotationClass) {
	Objects.requireNonNull(annotationClass);

	return AnnotationSupport.getDirectlyAndIndirectlyPresent(declaredAnnotations(), annotationClass);
	}

	/**
	* {@inheritDoc}
	* <p>Note that any annotations returned by this method are
	* declaration annotations.
	*/
	@Override
	public Annotation[] getDeclaredAnnotations() {
	return executable.getParameterAnnotations()[index];
	}

	/**
	* {@inheritDoc}
	* <p>Note that any annotation returned by this method is a
	* declaration annotation.
	*
	* @throws NullPointerException {@inheritDoc}
	*/
	@Override
	public <T extends Annotation> T getDeclaredAnnotation(Class<T> annotationClass) {
	// Only annotations on classes are inherited, for all other
	// objects getDeclaredAnnotation is the same as
	// getAnnotation.
	return getAnnotation(annotationClass);
	}

	/**
	* {@inheritDoc}
	* <p>Note that any annotations returned by this method are
	* declaration annotations.
	*
	* @throws NullPointerException {@inheritDoc}
	*/
	@Override
	public <T extends Annotation> T[] getDeclaredAnnotationsByType(Class<T> annotationClass) {
	// Only annotations on classes are inherited, for all other
	// objects getDeclaredAnnotations is the same as
	// getAnnotations.
	return getAnnotationsByType(annotationClass);
	}

	/**
	* {@inheritDoc}
	* <p>Note that any annotations returned by this method are
	* declaration annotations.
	*/
	@Override
	public Annotation[] getAnnotations() {
	return getDeclaredAnnotations();
	}

	private transient Map<Class<? extends Annotation>, Annotation> declaredAnnotations;

	private synchronized Map<Class<? extends Annotation>, Annotation> declaredAnnotations() {
	if(null == declaredAnnotations) {
	declaredAnnotations = new HashMap<>();
	for (Annotation a : getDeclaredAnnotations())
	declaredAnnotations.put(a.annotationType(), a);
	}
	return declaredAnnotations;
	}

	}

Back to index...