Java tutorial
/* * Copyright (c) 1996, 2019, 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 jdk.internal.HotSpotIntrinsicCandidate; import jdk.internal.access.SharedSecrets; import jdk.internal.reflect.CallerSensitive; import jdk.internal.reflect.MethodAccessor; import jdk.internal.reflect.Reflection; import jdk.internal.vm.annotation.ForceInline; import sun.reflect.annotation.ExceptionProxy; import sun.reflect.annotation.TypeNotPresentExceptionProxy; import sun.reflect.generics.repository.MethodRepository; import sun.reflect.generics.factory.CoreReflectionFactory; import sun.reflect.generics.factory.GenericsFactory; import sun.reflect.generics.scope.MethodScope; import sun.reflect.annotation.AnnotationType; import sun.reflect.annotation.AnnotationParser; import java.lang.annotation.Annotation; import java.lang.annotation.AnnotationFormatError; import java.nio.ByteBuffer; import java.util.StringJoiner; /** * A {@code Method} provides information about, and access to, a single method * on a class or interface. The reflected method may be a class method * or an instance method (including an abstract method). * * <p>A {@code Method} permits widening conversions to occur when matching the * actual parameters to invoke with the underlying method's formal * parameters, but it throws an {@code IllegalArgumentException} if a * narrowing conversion would occur. * * @see Member * @see java.lang.Class * @see java.lang.Class#getMethods() * @see java.lang.Class#getMethod(String, Class[]) * @see java.lang.Class#getDeclaredMethods() * @see java.lang.Class#getDeclaredMethod(String, Class[]) * * @author Kenneth Russell * @author Nakul Saraiya * @since 1.1 */ public final class Method extends Executable { private Class<?> clazz; private int slot; // This is guaranteed to be interned by the VM in the 1.4 // reflection implementation private String name; private Class<?> returnType; private Class<?>[] parameterTypes; private Class<?>[] exceptionTypes; private int modifiers; // Generics and annotations support private transient String signature; // generic info repository; lazily initialized private transient MethodRepository genericInfo; private byte[] annotations; private byte[] parameterAnnotations; private byte[] annotationDefault; private volatile MethodAccessor methodAccessor; // For sharing of MethodAccessors. This branching structure is // currently only two levels deep (i.e., one root Method and // potentially many Method objects pointing to it.) // // If this branching structure would ever contain cycles, deadlocks can // occur in annotation code. private Method root; // Generics infrastructure private String getGenericSignature() { return signature; } // Accessor for factory private GenericsFactory getFactory() { // create scope and factory return CoreReflectionFactory.make(this, MethodScope.make(this)); } // Accessor for generic info repository @Override MethodRepository getGenericInfo() { // lazily initialize repository if necessary if (genericInfo == null) { // create and cache generic info repository genericInfo = MethodRepository.make(getGenericSignature(), getFactory()); } return genericInfo; //return cached repository } /** * Package-private constructor used by ReflectAccess to enable * instantiation of these objects in Java code from the java.lang * package via sun.reflect.LangReflectAccess. */ Method(Class<?> declaringClass, String name, Class<?>[] parameterTypes, Class<?> returnType, Class<?>[] checkedExceptions, int modifiers, int slot, String signature, byte[] annotations, byte[] parameterAnnotations, byte[] annotationDefault) { this.clazz = declaringClass; this.name = name; this.parameterTypes = parameterTypes; this.returnType = returnType; this.exceptionTypes = checkedExceptions; this.modifiers = modifiers; this.slot = slot; this.signature = signature; this.annotations = annotations; this.parameterAnnotations = parameterAnnotations; this.annotationDefault = annotationDefault; } /** * Package-private routine (exposed to java.lang.Class via * ReflectAccess) which returns a copy of this Method. The copy's * "root" field points to this Method. */ Method copy() { // This routine enables sharing of MethodAccessor objects // among Method objects which refer to the same underlying // method in the VM. (All of this contortion is only necessary // because of the "accessibility" bit in AccessibleObject, // which implicitly requires that new java.lang.reflect // objects be fabricated for each reflective call on Class // objects.) if (this.root != null) throw new IllegalArgumentException("Can not copy a non-root Method"); Method res = new Method(clazz, name, parameterTypes, returnType, exceptionTypes, modifiers, slot, signature, annotations, parameterAnnotations, annotationDefault); res.root = this; // Might as well eagerly propagate this if already present res.methodAccessor = methodAccessor; return res; } /** * Make a copy of a leaf method. */ Method leafCopy() { if (this.root == null) throw new IllegalArgumentException("Can only leafCopy a non-root Method"); Method res = new Method(clazz, name, parameterTypes, returnType, exceptionTypes, modifiers, slot, signature, annotations, parameterAnnotations, annotationDefault); res.root = root; res.methodAccessor = methodAccessor; return res; } /** * @throws InaccessibleObjectException {@inheritDoc} * @throws SecurityException {@inheritDoc} */ @Override @CallerSensitive public void setAccessible(boolean flag) { AccessibleObject.checkPermission(); if (flag) checkCanSetAccessible(Reflection.getCallerClass()); setAccessible0(flag); } @Override void checkCanSetAccessible(Class<?> caller) { checkCanSetAccessible(caller, clazz); } @Override Method getRoot() { return root; } @Override boolean hasGenericInformation() { return (getGenericSignature() != null); } @Override byte[] getAnnotationBytes() { return annotations; } /** * Returns the {@code Class} object representing the class or interface * that declares the method represented by this object. */ @Override public Class<?> getDeclaringClass() { return clazz; } /** * Returns the name of the method represented by this {@code Method} * object, as a {@code String}. */ @Override public String getName() { return name; } /** * {@inheritDoc} */ @Override public int getModifiers() { return modifiers; } /** * {@inheritDoc} * @throws GenericSignatureFormatError {@inheritDoc} * @since 1.5 */ @Override @SuppressWarnings({ "rawtypes", "unchecked" }) public TypeVariable<Method>[] getTypeParameters() { if (getGenericSignature() != null) return (TypeVariable<Method>[]) getGenericInfo().getTypeParameters(); else return (TypeVariable<Method>[]) new TypeVariable[0]; } /** * Returns a {@code Class} object that represents the formal return type * of the method represented by this {@code Method} object. * * @return the return type for the method this object represents */ public Class<?> getReturnType() { return returnType; } /** * Returns a {@code Type} object that represents the formal return * type of the method represented by this {@code Method} object. * * <p>If the return type is a parameterized type, * the {@code Type} object returned must accurately reflect * the actual type arguments used in the source code. * * <p>If the return type is a type variable or a parameterized type, it * is created. Otherwise, it is resolved. * * @return a {@code Type} object that represents the formal return * type of the underlying method * @throws GenericSignatureFormatError * if the generic method signature does not conform to the format * specified in * <cite>The Java™ Virtual Machine Specification</cite> * @throws TypeNotPresentException if the underlying method's * return type refers to a non-existent type declaration * @throws MalformedParameterizedTypeException if the * underlying method's return typed refers to a parameterized * type that cannot be instantiated for any reason * @since 1.5 */ public Type getGenericReturnType() { if (getGenericSignature() != null) { return getGenericInfo().getReturnType(); } else { return getReturnType(); } } @Override Class<?>[] getSharedParameterTypes() { return parameterTypes; } @Override Class<?>[] getSharedExceptionTypes() { return exceptionTypes; } /** * {@inheritDoc} */ @Override public Class<?>[] getParameterTypes() { return parameterTypes.clone(); } /** * {@inheritDoc} * @since 1.8 */ public int getParameterCount() { return parameterTypes.length; } /** * {@inheritDoc} * @throws GenericSignatureFormatError {@inheritDoc} * @throws TypeNotPresentException {@inheritDoc} * @throws MalformedParameterizedTypeException {@inheritDoc} * @since 1.5 */ @Override public Type[] getGenericParameterTypes() { return super.getGenericParameterTypes(); } /** * {@inheritDoc} */ @Override public Class<?>[] getExceptionTypes() { return exceptionTypes.clone(); } /** * {@inheritDoc} * @throws GenericSignatureFormatError {@inheritDoc} * @throws TypeNotPresentException {@inheritDoc} * @throws MalformedParameterizedTypeException {@inheritDoc} * @since 1.5 */ @Override public Type[] getGenericExceptionTypes() { return super.getGenericExceptionTypes(); } /** * Compares this {@code Method} against the specified object. Returns * true if the objects are the same. Two {@code Methods} are the same if * they were declared by the same class and have the same name * and formal parameter types and return type. */ public boolean equals(Object obj) { if (obj != null && obj instanceof Method) { Method other = (Method) obj; if ((getDeclaringClass() == other.getDeclaringClass()) && (getName() == other.getName())) { if (!returnType.equals(other.getReturnType())) return false; return equalParamTypes(parameterTypes, other.parameterTypes); } } return false; } /** * Returns a hashcode for this {@code Method}. The hashcode is computed * as the exclusive-or of the hashcodes for the underlying * method's declaring class name and the method's name. */ public int hashCode() { return getDeclaringClass().getName().hashCode() ^ getName().hashCode(); } /** * Returns a string describing this {@code Method}. The string is * formatted as the method access modifiers, if any, followed by * the method return type, followed by a space, followed by the * class declaring the method, followed by a period, followed by * the method name, followed by a parenthesized, comma-separated * list of the method's formal parameter types. If the method * throws checked exceptions, the parameter list is followed by a * space, followed by the word "{@code throws}" followed by a * comma-separated list of the thrown exception types. * For example: * <pre> * public boolean java.lang.Object.equals(java.lang.Object) * </pre> * * <p>The access modifiers are placed in canonical order as * specified by "The Java Language Specification". This is * {@code public}, {@code protected} or {@code private} first, * and then other modifiers in the following order: * {@code abstract}, {@code default}, {@code static}, {@code final}, * {@code synchronized}, {@code native}, {@code strictfp}. * * @return a string describing this {@code Method} * * @jls 8.4.3 Method Modifiers * @jls 9.4 Method Declarations * @jls 9.6.1 Annotation Type Elements */ public String toString() { return sharedToString(Modifier.methodModifiers(), isDefault(), parameterTypes, exceptionTypes); } @Override void specificToStringHeader(StringBuilder sb) { sb.append(getReturnType().getTypeName()).append(' '); sb.append(getDeclaringClass().getTypeName()).append('.'); sb.append(getName()); } @Override String toShortString() { StringBuilder sb = new StringBuilder("method "); sb.append(getDeclaringClass().getTypeName()).append('.'); sb.append(getName()); sb.append('('); StringJoiner sj = new StringJoiner(","); for (Class<?> parameterType : getParameterTypes()) { sj.add(parameterType.getTypeName()); } sb.append(sj); sb.append(')'); return sb.toString(); } /** * Returns a string describing this {@code Method}, including type * parameters. The string is formatted as the method access * modifiers, if any, followed by an angle-bracketed * comma-separated list of the method's type parameters, if any, * including informative bounds of the type parameters, if any, * followed by the method's generic return type, followed by a * space, followed by the class declaring the method, followed by * a period, followed by the method name, followed by a * parenthesized, comma-separated list of the method's generic * formal parameter types. * * If this method was declared to take a variable number of * arguments, instead of denoting the last parameter as * "<code><i>Type</i>[]</code>", it is denoted as * "<code><i>Type</i>...</code>". * * A space is used to separate access modifiers from one another * and from the type parameters or return type. If there are no * type parameters, the type parameter list is elided; if the type * parameter list is present, a space separates the list from the * class name. If the method is declared to throw exceptions, the * parameter list is followed by a space, followed by the word * "{@code throws}" followed by a comma-separated list of the generic * thrown exception types. * * <p>The access modifiers are placed in canonical order as * specified by "The Java Language Specification". This is * {@code public}, {@code protected} or {@code private} first, * and then other modifiers in the following order: * {@code abstract}, {@code default}, {@code static}, {@code final}, * {@code synchronized}, {@code native}, {@code strictfp}. * * @return a string describing this {@code Method}, * include type parameters * * @since 1.5 * * @jls 8.4.3 Method Modifiers * @jls 9.4 Method Declarations * @jls 9.6.1 Annotation Type Elements */ @Override public String toGenericString() { return sharedToGenericString(Modifier.methodModifiers(), isDefault()); } @Override void specificToGenericStringHeader(StringBuilder sb) { Type genRetType = getGenericReturnType(); sb.append(genRetType.getTypeName()).append(' '); sb.append(getDeclaringClass().getTypeName()).append('.'); sb.append(getName()); } /** * Invokes the underlying method represented by this {@code Method} * object, on the specified object with the specified parameters. * Individual parameters are automatically unwrapped to match * primitive formal parameters, and both primitive and reference * parameters are subject to method invocation conversions as * necessary. * * <p>If the underlying method is static, then the specified {@code obj} * argument is ignored. It may be null. * * <p>If the number of formal parameters required by the underlying method is * 0, the supplied {@code args} array may be of length 0 or null. * * <p>If the underlying method is an instance method, it is invoked * using dynamic method lookup as documented in The Java Language * Specification, section 15.12.4.4; in particular, * overriding based on the runtime type of the target object may occur. * * <p>If the underlying method is static, the class that declared * the method is initialized if it has not already been initialized. * * <p>If the method completes normally, the value it returns is * returned to the caller of invoke; if the value has a primitive * type, it is first appropriately wrapped in an object. However, * if the value has the type of an array of a primitive type, the * elements of the array are <i>not</i> wrapped in objects; in * other words, an array of primitive type is returned. If the * underlying method return type is void, the invocation returns * null. * * @param obj the object the underlying method is invoked from * @param args the arguments used for the method call * @return the result of dispatching the method represented by * this object on {@code obj} with parameters * {@code args} * * @exception IllegalAccessException if this {@code Method} object * is enforcing Java language access control and the underlying * method is inaccessible. * @exception IllegalArgumentException if the method is an * instance method and the specified object argument * is not an instance of the class or interface * declaring the underlying method (or of a subclass * or implementor thereof); if the number of actual * and formal parameters differ; if an unwrapping * conversion for primitive arguments fails; or if, * after possible unwrapping, a parameter value * cannot be converted to the corresponding formal * parameter type by a method invocation conversion. * @exception InvocationTargetException if the underlying method * throws an exception. * @exception NullPointerException if the specified object is null * and the method is an instance method. * @exception ExceptionInInitializerError if the initialization * provoked by this method fails. */ @CallerSensitive @ForceInline // to ensure Reflection.getCallerClass optimization @HotSpotIntrinsicCandidate public Object invoke(Object obj, Object... args) throws IllegalAccessException, IllegalArgumentException, InvocationTargetException { if (!override) { Class<?> caller = Reflection.getCallerClass(); checkAccess(caller, clazz, Modifier.isStatic(modifiers) ? null : obj.getClass(), modifiers); } MethodAccessor ma = methodAccessor; // read volatile if (ma == null) { ma = acquireMethodAccessor(); } return ma.invoke(obj, args); } /** * Returns {@code true} if this method is a bridge * method; returns {@code false} otherwise. * * @return true if and only if this method is a bridge * method as defined by the Java Language Specification. * @since 1.5 */ public boolean isBridge() { return (getModifiers() & Modifier.BRIDGE) != 0; } /** * {@inheritDoc} * @since 1.5 */ @Override public boolean isVarArgs() { return super.isVarArgs(); } /** * {@inheritDoc} * @jls 13.1 The Form of a Binary * @since 1.5 */ @Override public boolean isSynthetic() { return super.isSynthetic(); } /** * Returns {@code true} if this method is a default * method; returns {@code false} otherwise. * * A default method is a public non-abstract instance method, that * is, a non-static method with a body, declared in an interface * type. * * @return true if and only if this method is a default * method as defined by the Java Language Specification. * @since 1.8 */ public boolean isDefault() { // Default methods are public non-abstract instance methods // declared in an interface. return ((getModifiers() & (Modifier.ABSTRACT | Modifier.PUBLIC | Modifier.STATIC)) == Modifier.PUBLIC) && getDeclaringClass().isInterface(); } // NOTE that there is no synchronization used here. It is correct // (though not efficient) to generate more than one MethodAccessor // for a given Method. However, avoiding synchronization will // probably make the implementation more scalable. private MethodAccessor acquireMethodAccessor() { // First check to see if one has been created yet, and take it // if so MethodAccessor tmp = null; if (root != null) tmp = root.getMethodAccessor(); if (tmp != null) { methodAccessor = tmp; } else { // Otherwise fabricate one and propagate it up to the root tmp = reflectionFactory.newMethodAccessor(this); setMethodAccessor(tmp); } return tmp; } // Returns MethodAccessor for this Method object, not looking up // the chain to the root MethodAccessor getMethodAccessor() { return methodAccessor; } // Sets the MethodAccessor for this Method object and // (recursively) its root void setMethodAccessor(MethodAccessor accessor) { methodAccessor = accessor; // Propagate up if (root != null) { root.setMethodAccessor(accessor); } } /** * Returns the default value for the annotation member represented by * this {@code Method} instance. If the member is of a primitive type, * an instance of the corresponding wrapper type is returned. Returns * null if no default is associated with the member, or if the method * instance does not represent a declared member of an annotation type. * * @return the default value for the annotation member represented * by this {@code Method} instance. * @throws TypeNotPresentException if the annotation is of type * {@link Class} and no definition can be found for the * default class value. * @since 1.5 */ public Object getDefaultValue() { if (annotationDefault == null) return null; Class<?> memberType = AnnotationType.invocationHandlerReturnType(getReturnType()); Object result = AnnotationParser.parseMemberValue(memberType, ByteBuffer.wrap(annotationDefault), SharedSecrets.getJavaLangAccess().getConstantPool(getDeclaringClass()), getDeclaringClass()); if (result instanceof ExceptionProxy) { if (result instanceof TypeNotPresentExceptionProxy) { TypeNotPresentExceptionProxy proxy = (TypeNotPresentExceptionProxy) result; throw new TypeNotPresentException(proxy.typeName(), proxy.getCause()); } throw new AnnotationFormatError("Invalid default: " + this); } return result; } /** * {@inheritDoc} * @throws NullPointerException {@inheritDoc} * @since 1.5 */ public <T extends Annotation> T getAnnotation(Class<T> annotationClass) { return super.getAnnotation(annotationClass); } /** * {@inheritDoc} * @since 1.5 */ public Annotation[] getDeclaredAnnotations() { return super.getDeclaredAnnotations(); } /** * {@inheritDoc} * @since 1.5 */ @Override public Annotation[][] getParameterAnnotations() { return sharedGetParameterAnnotations(parameterTypes, parameterAnnotations); } /** * {@inheritDoc} * @since 1.8 */ @Override public AnnotatedType getAnnotatedReturnType() { return getAnnotatedReturnType0(getGenericReturnType()); } @Override boolean handleParameterNumberMismatch(int resultLength, int numParameters) { throw new AnnotationFormatError("Parameter annotations don't match number of parameters"); } }