Java tutorial
/* * Copyright (c) 2012, 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 java.lang.annotation.*; import java.util.Arrays; import java.util.Map; import java.util.Objects; import java.util.StringJoiner; import java.util.stream.Stream; import java.util.stream.Collectors; import jdk.internal.access.SharedSecrets; import sun.reflect.annotation.AnnotationParser; import sun.reflect.annotation.AnnotationSupport; import sun.reflect.annotation.TypeAnnotationParser; import sun.reflect.annotation.TypeAnnotation; import sun.reflect.generics.repository.ConstructorRepository; /** * A shared superclass for the common functionality of {@link Method} * and {@link Constructor}. * * @since 1.8 */ public abstract class Executable extends AccessibleObject implements Member, GenericDeclaration { /* * Only grant package-visibility to the constructor. */ Executable() { } /** * Accessor method to allow code sharing */ abstract byte[] getAnnotationBytes(); /** * Does the Executable have generic information. */ abstract boolean hasGenericInformation(); abstract ConstructorRepository getGenericInfo(); boolean equalParamTypes(Class<?>[] params1, Class<?>[] params2) { /* Avoid unnecessary cloning */ if (params1.length == params2.length) { for (int i = 0; i < params1.length; i++) { if (params1[i] != params2[i]) return false; } return true; } return false; } Annotation[][] parseParameterAnnotations(byte[] parameterAnnotations) { return AnnotationParser.parseParameterAnnotations(parameterAnnotations, SharedSecrets.getJavaLangAccess().getConstantPool(getDeclaringClass()), getDeclaringClass()); } void printModifiersIfNonzero(StringBuilder sb, int mask, boolean isDefault) { int mod = getModifiers() & mask; if (mod != 0 && !isDefault) { sb.append(Modifier.toString(mod)).append(' '); } else { int access_mod = mod & Modifier.ACCESS_MODIFIERS; if (access_mod != 0) sb.append(Modifier.toString(access_mod)).append(' '); if (isDefault) sb.append("default "); mod = (mod & ~Modifier.ACCESS_MODIFIERS); if (mod != 0) sb.append(Modifier.toString(mod)).append(' '); } } String sharedToString(int modifierMask, boolean isDefault, Class<?>[] parameterTypes, Class<?>[] exceptionTypes) { try { StringBuilder sb = new StringBuilder(); printModifiersIfNonzero(sb, modifierMask, isDefault); specificToStringHeader(sb); sb.append(Arrays.stream(parameterTypes).map(Type::getTypeName) .collect(Collectors.joining(",", "(", ")"))); if (exceptionTypes.length > 0) { sb.append(Arrays.stream(exceptionTypes).map(Type::getTypeName) .collect(Collectors.joining(",", " throws ", ""))); } return sb.toString(); } catch (Exception e) { return "<" + e + ">"; } } /** * Generate toString header information specific to a method or * constructor. */ abstract void specificToStringHeader(StringBuilder sb); static String typeVarBounds(TypeVariable<?> typeVar) { Type[] bounds = typeVar.getBounds(); if (bounds.length == 1 && bounds[0].equals(Object.class)) { return typeVar.getName(); } else { return typeVar.getName() + " extends " + Arrays.stream(bounds).map(Type::getTypeName).collect(Collectors.joining(" & ")); } } String sharedToGenericString(int modifierMask, boolean isDefault) { try { StringBuilder sb = new StringBuilder(); printModifiersIfNonzero(sb, modifierMask, isDefault); TypeVariable<?>[] typeparms = getTypeParameters(); if (typeparms.length > 0) { sb.append(Arrays.stream(typeparms).map(Executable::typeVarBounds) .collect(Collectors.joining(",", "<", "> "))); } specificToGenericStringHeader(sb); sb.append('('); StringJoiner sj = new StringJoiner(","); Type[] params = getGenericParameterTypes(); for (int j = 0; j < params.length; j++) { String param = params[j].getTypeName(); if (isVarArgs() && (j == params.length - 1)) // replace T[] with T... param = param.replaceFirst("\\[\\]$", "..."); sj.add(param); } sb.append(sj.toString()); sb.append(')'); Type[] exceptionTypes = getGenericExceptionTypes(); if (exceptionTypes.length > 0) { sb.append(Arrays.stream(exceptionTypes).map(Type::getTypeName) .collect(Collectors.joining(",", " throws ", ""))); } return sb.toString(); } catch (Exception e) { return "<" + e + ">"; } } /** * Generate toGenericString header information specific to a * method or constructor. */ abstract void specificToGenericStringHeader(StringBuilder sb); /** * Returns the {@code Class} object representing the class or interface * that declares the executable represented by this object. */ public abstract Class<?> getDeclaringClass(); /** * Returns the name of the executable represented by this object. */ public abstract String getName(); /** * Returns the Java language {@linkplain Modifier modifiers} for * the executable represented by this object. */ public abstract int getModifiers(); /** * Returns an array of {@code TypeVariable} objects that represent the * type variables declared by the generic declaration represented by this * {@code GenericDeclaration} object, in declaration order. Returns an * array of length 0 if the underlying generic declaration declares no type * variables. * * @return an array of {@code TypeVariable} objects that represent * the type variables declared by this generic declaration * @throws GenericSignatureFormatError if the generic * signature of this generic declaration does not conform to * the format specified in * <cite>The Java™ Virtual Machine Specification</cite> */ public abstract TypeVariable<?>[] getTypeParameters(); // returns shared array of parameter types - must never give it out // to the untrusted code... abstract Class<?>[] getSharedParameterTypes(); // returns shared array of exception types - must never give it out // to the untrusted code... abstract Class<?>[] getSharedExceptionTypes(); /** * Returns an array of {@code Class} objects that represent the formal * parameter types, in declaration order, of the executable * represented by this object. Returns an array of length * 0 if the underlying executable takes no parameters. * Note that the constructors of some inner classes * may have an implicitly declared parameter in addition to * explicitly declared ones. * * @return the parameter types for the executable this object * represents */ public abstract Class<?>[] getParameterTypes(); /** * Returns the number of formal parameters (whether explicitly * declared or implicitly declared or neither) for the executable * represented by this object. * * @return The number of formal parameters for the executable this * object represents */ public int getParameterCount() { throw new AbstractMethodError(); } /** * Returns an array of {@code Type} objects that represent the formal * parameter types, in declaration order, of the executable represented by * this object. Returns an array of length 0 if the * underlying executable takes no parameters. * Note that the constructors of some inner classes * may have an implicitly declared parameter in addition to * explicitly declared ones. * * <p>If a formal parameter type is a parameterized type, * the {@code Type} object returned for it must accurately reflect * the actual type arguments used in the source code. * * <p>If a formal parameter type is a type variable or a parameterized * type, it is created. Otherwise, it is resolved. * * @return an array of {@code Type}s that represent the formal * parameter types of the underlying executable, in declaration order * @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 any of the parameter * types of the underlying executable refers to a non-existent type * declaration * @throws MalformedParameterizedTypeException if any of * the underlying executable's parameter types refer to a parameterized * type that cannot be instantiated for any reason */ public Type[] getGenericParameterTypes() { if (hasGenericInformation()) return getGenericInfo().getParameterTypes(); else return getParameterTypes(); } /** * Behaves like {@code getGenericParameterTypes}, but returns type * information for all parameters, including synthetic parameters. */ Type[] getAllGenericParameterTypes() { final boolean genericInfo = hasGenericInformation(); // Easy case: we don't have generic parameter information. In // this case, we just return the result of // getParameterTypes(). if (!genericInfo) { return getParameterTypes(); } else { final boolean realParamData = hasRealParameterData(); final Type[] genericParamTypes = getGenericParameterTypes(); final Type[] nonGenericParamTypes = getParameterTypes(); final Type[] out = new Type[nonGenericParamTypes.length]; final Parameter[] params = getParameters(); int fromidx = 0; // If we have real parameter data, then we use the // synthetic and mandate flags to our advantage. if (realParamData) { for (int i = 0; i < out.length; i++) { final Parameter param = params[i]; if (param.isSynthetic() || param.isImplicit()) { // If we hit a synthetic or mandated parameter, // use the non generic parameter info. out[i] = nonGenericParamTypes[i]; } else { // Otherwise, use the generic parameter info. out[i] = genericParamTypes[fromidx]; fromidx++; } } } else { // Otherwise, use the non-generic parameter data. // Without method parameter reflection data, we have // no way to figure out which parameters are // synthetic/mandated, thus, no way to match up the // indexes. return genericParamTypes.length == nonGenericParamTypes.length ? genericParamTypes : nonGenericParamTypes; } return out; } } /** * Returns an array of {@code Parameter} objects that represent * all the parameters to the underlying executable represented by * this object. Returns an array of length 0 if the executable * has no parameters. * * <p>The parameters of the underlying executable do not necessarily * have unique names, or names that are legal identifiers in the * Java programming language (JLS 3.8). * * @throws MalformedParametersException if the class file contains * a MethodParameters attribute that is improperly formatted. * @return an array of {@code Parameter} objects representing all * the parameters to the executable this object represents. */ public Parameter[] getParameters() { // TODO: This may eventually need to be guarded by security // mechanisms similar to those in Field, Method, etc. // // Need to copy the cached array to prevent users from messing // with it. Since parameters are immutable, we can // shallow-copy. return privateGetParameters().clone(); } private Parameter[] synthesizeAllParams() { final int realparams = getParameterCount(); final Parameter[] out = new Parameter[realparams]; for (int i = 0; i < realparams; i++) // TODO: is there a way to synthetically derive the // modifiers? Probably not in the general case, since // we'd have no way of knowing about them, but there // may be specific cases. out[i] = new Parameter("arg" + i, 0, this, i); return out; } private void verifyParameters(final Parameter[] parameters) { final int mask = Modifier.FINAL | Modifier.SYNTHETIC | Modifier.MANDATED; if (getParameterTypes().length != parameters.length) throw new MalformedParametersException("Wrong number of parameters in MethodParameters attribute"); for (Parameter parameter : parameters) { final String name = parameter.getRealName(); final int mods = parameter.getModifiers(); if (name != null) { if (name.isEmpty() || name.indexOf('.') != -1 || name.indexOf(';') != -1 || name.indexOf('[') != -1 || name.indexOf('/') != -1) { throw new MalformedParametersException("Invalid parameter name \"" + name + "\""); } } if (mods != (mods & mask)) { throw new MalformedParametersException("Invalid parameter modifiers"); } } } private Parameter[] privateGetParameters() { // Use tmp to avoid multiple writes to a volatile. Parameter[] tmp = parameters; if (tmp == null) { // Otherwise, go to the JVM to get them try { tmp = getParameters0(); } catch (IllegalArgumentException e) { // Rethrow ClassFormatErrors throw new MalformedParametersException("Invalid constant pool index"); } // If we get back nothing, then synthesize parameters if (tmp == null) { hasRealParameterData = false; tmp = synthesizeAllParams(); } else { hasRealParameterData = true; verifyParameters(tmp); } parameters = tmp; } return tmp; } boolean hasRealParameterData() { // If this somehow gets called before parameters gets // initialized, force it into existence. if (parameters == null) { privateGetParameters(); } return hasRealParameterData; } private transient volatile boolean hasRealParameterData; private transient volatile Parameter[] parameters; private native Parameter[] getParameters0(); native byte[] getTypeAnnotationBytes0(); // Needed by reflectaccess byte[] getTypeAnnotationBytes() { return getTypeAnnotationBytes0(); } /** * Returns an array of {@code Class} objects that represent the * types of exceptions declared to be thrown by the underlying * executable represented by this object. Returns an array of * length 0 if the executable declares no exceptions in its {@code * throws} clause. * * @return the exception types declared as being thrown by the * executable this object represents */ public abstract Class<?>[] getExceptionTypes(); /** * Returns an array of {@code Type} objects that represent the * exceptions declared to be thrown by this executable object. * Returns an array of length 0 if the underlying executable declares * no exceptions in its {@code throws} clause. * * <p>If an exception type is a type variable or a parameterized * type, it is created. Otherwise, it is resolved. * * @return an array of Types that represent the exception types * thrown by the underlying executable * @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 executable's * {@code throws} clause refers to a non-existent type declaration * @throws MalformedParameterizedTypeException if * the underlying executable's {@code throws} clause refers to a * parameterized type that cannot be instantiated for any reason */ public Type[] getGenericExceptionTypes() { Type[] result; if (hasGenericInformation() && ((result = getGenericInfo().getExceptionTypes()).length > 0)) return result; else return getExceptionTypes(); } /** * Returns a string describing this {@code Executable}, including * any type parameters. * @return a string describing this {@code Executable}, including * any type parameters */ public abstract String toGenericString(); /** * Returns {@code true} if this executable was declared to take a * variable number of arguments; returns {@code false} otherwise. * * @return {@code true} if an only if this executable was declared * to take a variable number of arguments. */ public boolean isVarArgs() { return (getModifiers() & Modifier.VARARGS) != 0; } /** * Returns {@code true} if this executable is a synthetic * construct; returns {@code false} otherwise. * * @return true if and only if this executable is a synthetic * construct as defined by * <cite>The Java™ Language Specification</cite>. * @jls 13.1 The Form of a Binary */ public boolean isSynthetic() { return Modifier.isSynthetic(getModifiers()); } /** * Returns an array of arrays of {@code Annotation}s that * represent the annotations on the formal parameters, in * declaration order, of the {@code Executable} represented by * this object. Synthetic and mandated parameters (see * explanation below), such as the outer "this" parameter to an * inner class constructor will be represented in the returned * array. If the executable has no parameters (meaning no formal, * no synthetic, and no mandated parameters), a zero-length array * will be returned. If the {@code Executable} has one or more * parameters, a nested array of length zero is returned for each * parameter with no annotations. The annotation objects contained * in the returned arrays are serializable. The caller of this * method is free to modify the returned arrays; it will have no * effect on the arrays returned to other callers. * * A compiler may add extra parameters that are implicitly * declared in source ("mandated"), as well as parameters that * are neither implicitly nor explicitly declared in source * ("synthetic") to the parameter list for a method. See {@link * java.lang.reflect.Parameter} for more information. * * @see java.lang.reflect.Parameter * @see java.lang.reflect.Parameter#getAnnotations * @return an array of arrays that represent the annotations on * the formal and implicit parameters, in declaration order, of * the executable represented by this object */ public abstract Annotation[][] getParameterAnnotations(); Annotation[][] sharedGetParameterAnnotations(Class<?>[] parameterTypes, byte[] parameterAnnotations) { int numParameters = parameterTypes.length; if (parameterAnnotations == null) return new Annotation[numParameters][0]; Annotation[][] result = parseParameterAnnotations(parameterAnnotations); if (result.length != numParameters && handleParameterNumberMismatch(result.length, numParameters)) { Annotation[][] tmp = new Annotation[result.length + 1][]; // Shift annotations down one to account for an implicit leading parameter System.arraycopy(result, 0, tmp, 1, result.length); tmp[0] = new Annotation[0]; result = tmp; } return result; } abstract boolean handleParameterNumberMismatch(int resultLength, int numParameters); /** * {@inheritDoc} * @throws NullPointerException {@inheritDoc} */ public <T extends Annotation> T getAnnotation(Class<T> annotationClass) { Objects.requireNonNull(annotationClass); return annotationClass.cast(declaredAnnotations().get(annotationClass)); } /** * {@inheritDoc} * @throws NullPointerException {@inheritDoc} */ @Override public <T extends Annotation> T[] getAnnotationsByType(Class<T> annotationClass) { Objects.requireNonNull(annotationClass); return AnnotationSupport.getDirectlyAndIndirectlyPresent(declaredAnnotations(), annotationClass); } /** * {@inheritDoc} */ public Annotation[] getDeclaredAnnotations() { return AnnotationParser.toArray(declaredAnnotations()); } private transient volatile Map<Class<? extends Annotation>, Annotation> declaredAnnotations; private Map<Class<? extends Annotation>, Annotation> declaredAnnotations() { Map<Class<? extends Annotation>, Annotation> declAnnos; if ((declAnnos = declaredAnnotations) == null) { synchronized (this) { if ((declAnnos = declaredAnnotations) == null) { Executable root = (Executable) getRoot(); if (root != null) { declAnnos = root.declaredAnnotations(); } else { declAnnos = AnnotationParser.parseAnnotations(getAnnotationBytes(), SharedSecrets.getJavaLangAccess().getConstantPool(getDeclaringClass()), getDeclaringClass()); } declaredAnnotations = declAnnos; } } } return declAnnos; } /** * Returns an {@code AnnotatedType} object that represents the use of a type to * specify the return type of the method/constructor represented by this * Executable. * * If this {@code Executable} object represents a constructor, the {@code * AnnotatedType} object represents the type of the constructed object. * * If this {@code Executable} object represents a method, the {@code * AnnotatedType} object represents the use of a type to specify the return * type of the method. * * @return an object representing the return type of the method * or constructor represented by this {@code Executable} */ public abstract AnnotatedType getAnnotatedReturnType(); /* Helper for subclasses of Executable. * * Returns an AnnotatedType object that represents the use of a type to * specify the return type of the method/constructor represented by this * Executable. */ AnnotatedType getAnnotatedReturnType0(Type returnType) { return TypeAnnotationParser.buildAnnotatedType(getTypeAnnotationBytes0(), SharedSecrets.getJavaLangAccess().getConstantPool(getDeclaringClass()), this, getDeclaringClass(), returnType, TypeAnnotation.TypeAnnotationTarget.METHOD_RETURN); } /** * Returns an {@code AnnotatedType} object that represents the use of a * type to specify the receiver type of the method/constructor represented * by this {@code Executable} object. * * The receiver type of a method/constructor is available only if the * method/constructor has a receiver parameter (JLS 8.4.1). If this {@code * Executable} object <em>represents an instance method or represents a * constructor of an inner member class</em>, and the * method/constructor <em>either</em> has no receiver parameter or has a * receiver parameter with no annotations on its type, then the return * value is an {@code AnnotatedType} object representing an element with no * annotations. * * If this {@code Executable} object represents a static method or * represents a constructor of a top level, static member, local, or * anonymous class, then the return value is null. * * @return an object representing the receiver type of the method or * constructor represented by this {@code Executable} or {@code null} if * this {@code Executable} can not have a receiver parameter * * @jls 8.4 Method Declarations * @jls 8.4.1 Formal Parameters * @jls 8.8 Constructor Declarations */ public AnnotatedType getAnnotatedReceiverType() { if (Modifier.isStatic(this.getModifiers())) return null; return TypeAnnotationParser.buildAnnotatedType(getTypeAnnotationBytes0(), SharedSecrets.getJavaLangAccess().getConstantPool(getDeclaringClass()), this, getDeclaringClass(), getDeclaringClass(), TypeAnnotation.TypeAnnotationTarget.METHOD_RECEIVER); } /** * Returns an array of {@code AnnotatedType} objects that represent the use * of types to specify formal parameter types of the method/constructor * represented by this Executable. The order of the objects in the array * corresponds to the order of the formal parameter types in the * declaration of the method/constructor. * * Returns an array of length 0 if the method/constructor declares no * parameters. * Note that the constructors of some inner classes * may have an implicitly declared parameter in addition to * explicitly declared ones. * * @return an array of objects representing the types of the * formal parameters of the method or constructor represented by this * {@code Executable} */ public AnnotatedType[] getAnnotatedParameterTypes() { return TypeAnnotationParser.buildAnnotatedTypes(getTypeAnnotationBytes0(), SharedSecrets.getJavaLangAccess().getConstantPool(getDeclaringClass()), this, getDeclaringClass(), getAllGenericParameterTypes(), TypeAnnotation.TypeAnnotationTarget.METHOD_FORMAL_PARAMETER); } /** * Returns an array of {@code AnnotatedType} objects that represent the use * of types to specify the declared exceptions of the method/constructor * represented by this Executable. The order of the objects in the array * corresponds to the order of the exception types in the declaration of * the method/constructor. * * Returns an array of length 0 if the method/constructor declares no * exceptions. * * @return an array of objects representing the declared * exceptions of the method or constructor represented by this {@code * Executable} */ public AnnotatedType[] getAnnotatedExceptionTypes() { return TypeAnnotationParser.buildAnnotatedTypes(getTypeAnnotationBytes0(), SharedSecrets.getJavaLangAccess().getConstantPool(getDeclaringClass()), this, getDeclaringClass(), getGenericExceptionTypes(), TypeAnnotation.TypeAnnotationTarget.THROWS); } }