Java tutorial
/* * Licensed to the Apache Software Foundation (ASF) under one or more * contributor license agreements. See the NOTICE file distributed with * this work for additional information regarding copyright ownership. * The ASF licenses this file to You under the Apache License, Version 2.0 * (the "License"); you may not use this file except in compliance with * the License. You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. * */ package org.apache.commons.bcel6.classfile; import java.io.DataInput; import java.io.IOException; import org.apache.commons.bcel6.Constants; import org.apache.commons.bcel6.generic.Type; import org.apache.commons.bcel6.util.BCELComparator; /** * This class represents the method info structure, i.e., the representation * for a method in the class. See JVM specification for details. * A method has access flags, a name, a signature and a number of attributes. * * @version $Id$ * @author <A HREF="mailto:m.dahm@gmx.de">M. Dahm</A> */ public final class Method extends FieldOrMethod { private static final long serialVersionUID = -2013983967283787941L; private static BCELComparator _cmp = new BCELComparator() { public boolean equals(Object o1, Object o2) { Method THIS = (Method) o1; Method THAT = (Method) o2; return THIS.getName().equals(THAT.getName()) && THIS.getSignature().equals(THAT.getSignature()); } public int hashCode(Object o) { Method THIS = (Method) o; return THIS.getSignature().hashCode() ^ THIS.getName().hashCode(); } }; // annotations defined on the parameters of a method private ParameterAnnotationEntry[] parameterAnnotationEntries; /** * Empty constructor, all attributes have to be defined via `setXXX' * methods. Use at your own risk. */ public Method() { } /** * Initialize from another object. Note that both objects use the same * references (shallow copy). Use clone() for a physical copy. */ public Method(Method c) { super(c); } /** * Construct object from file stream. * @param file Input stream * @throws IOException * @throws ClassFormatException */ Method(DataInput file, ConstantPool constant_pool) throws IOException, ClassFormatException { super(file, constant_pool); } /** * @param access_flags Access rights of method * @param name_index Points to field name in constant pool * @param signature_index Points to encoded signature * @param attributes Collection of attributes * @param constant_pool Array of constants */ public Method(int access_flags, int name_index, int signature_index, Attribute[] attributes, ConstantPool constant_pool) { super(access_flags, name_index, signature_index, attributes, constant_pool); } /** * Called by objects that are traversing the nodes of the tree implicitely * defined by the contents of a Java class. I.e., the hierarchy of methods, * fields, attributes, etc. spawns a tree of objects. * * @param v Visitor object */ public void accept(Visitor v) { v.visitMethod(this); } /** * @return Code attribute of method, if any */ public final Code getCode() { for (Attribute attribute : attributes) { if (attribute instanceof Code) { return (Code) attribute; } } return null; } /** * @return ExceptionTable attribute of method, if any, i.e., list all * exceptions the method may throw not exception handlers! */ public final ExceptionTable getExceptionTable() { for (Attribute attribute : attributes) { if (attribute instanceof ExceptionTable) { return (ExceptionTable) attribute; } } return null; } /** @return LocalVariableTable of code attribute if any, i.e. the call is forwarded * to the Code atribute. */ public final LocalVariableTable getLocalVariableTable() { Code code = getCode(); if (code == null) { return null; } return code.getLocalVariableTable(); } /** @return LineNumberTable of code attribute if any, i.e. the call is forwarded * to the Code atribute. */ public final LineNumberTable getLineNumberTable() { Code code = getCode(); if (code == null) { return null; } return code.getLineNumberTable(); } /** * Return string representation close to declaration format, * `public static void main(String[] args) throws IOException', e.g. * * @return String representation of the method. */ @Override public final String toString() { ConstantUtf8 c; String name, signature, access; // Short cuts to constant pool StringBuilder buf; access = Utility.accessToString(access_flags); // Get name and signature from constant pool c = (ConstantUtf8) constant_pool.getConstant(signature_index, Constants.CONSTANT_Utf8); signature = c.getBytes(); c = (ConstantUtf8) constant_pool.getConstant(name_index, Constants.CONSTANT_Utf8); name = c.getBytes(); signature = Utility.methodSignatureToString(signature, name, access, true, getLocalVariableTable()); buf = new StringBuilder(signature); for (Attribute attribute : attributes) { if (!((attribute instanceof Code) || (attribute instanceof ExceptionTable))) { buf.append(" [").append(attribute.toString()).append("]"); } } ExceptionTable e = getExceptionTable(); if (e != null) { String str = e.toString(); if (!str.equals("")) { buf.append("\n\t\tthrows ").append(str); } } return buf.toString(); } /** * @return deep copy of this method */ public final Method copy(ConstantPool _constant_pool) { return (Method) copy_(_constant_pool); } /** * @return return type of method */ public Type getReturnType() { return Type.getReturnType(getSignature()); } /** * @return array of method argument types */ public Type[] getArgumentTypes() { return Type.getArgumentTypes(getSignature()); } /** * @return Comparison strategy object */ public static BCELComparator getComparator() { return _cmp; } /** * @param comparator Comparison strategy object */ public static void setComparator(BCELComparator comparator) { _cmp = comparator; } /** * Return value as defined by given BCELComparator strategy. * By default two method objects are said to be equal when * their names and signatures are equal. * * @see java.lang.Object#equals(java.lang.Object) */ @Override public boolean equals(Object obj) { return _cmp.equals(this, obj); } /** * Return value as defined by given BCELComparator strategy. * By default return the hashcode of the method's name XOR signature. * * @see java.lang.Object#hashCode() */ @Override public int hashCode() { return _cmp.hashCode(this); } /** * @return Annotations on the parameters of a method */ public ParameterAnnotationEntry[] getParameterAnnotationEntries() { if (parameterAnnotationEntries == null) { parameterAnnotationEntries = ParameterAnnotationEntry.createParameterAnnotationEntries(getAttributes()); } return parameterAnnotationEntries; } }