ctnewmethod.java

Javassist是一个开源的分析、编辑和创建Java字节码的类库。是由东京技术学院的数学和计算机科学系的 Shigeru Chiba 所创建的。它已加入了开放源代码JBoss 应用服务器项目,通过使

/*
 * Javassist, a Java-bytecode translator toolkit.
 * Copyright (C) 1999-2006 Shigeru Chiba. All Rights Reserved.
 *
 * The contents of this file are subject to the Mozilla Public License Version
 * 1.1 (the "License"); you may not use this file except in compliance with
 * the License.  Alternatively, the contents of this file may be used under
 * the terms of the GNU Lesser General Public License Version 2.1 or later.
 *
 * Software distributed under the License is distributed on an "AS IS" basis,
 * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
 * for the specific language governing rights and limitations under the
 * License.
 */

package javassist;

import javassist.bytecode.*;
import javassist.compiler.Javac;
import javassist.compiler.CompileError;
import javassist.CtMethod.ConstParameter;

/**
 * A collection of static methods for creating a <code>CtMethod</code>.
 * An instance of this class does not make any sense.
 *
 * @see CtClass#addMethod(CtMethod)
 */
public class CtNewMethod {

    /**
     * Compiles the given source code and creates a method.
     * The source code must include not only the method body
     * but the whole declaration, for example,
     *
     * <ul><pre>"public Object id(Object obj) { return obj; }"</pre></ul>
     *
     * @param src               the source text. 
     * @param declaring    the class to which the created method is added.
     */
    public static CtMethod make(String src, CtClass declaring)
        throws CannotCompileException
    {
        return make(src, declaring, null, null);
    }

    /**
     * Compiles the given source code and creates a method.
     * The source code must include not only the method body
     * but the whole declaration, for example,
     *
     * <ul><pre>"public Object id(Object obj) { return obj; }"</pre></ul>
     *
     * <p>If the source code includes <code>$proceed()</code>, then
     * it is compiled into a method call on the specified object.
     *
     * @param src               the source text. 
     * @param declaring    the class to which the created method is added.
     * @param delegateObj       the source text specifying the object
     *                          that is called on by <code>$proceed()</code>.
     * @param delegateMethod    the name of the method
     *                          that is called by <code>$proceed()</code>.
     */
    public static CtMethod make(String src, CtClass declaring,
                                String delegateObj, String delegateMethod)
        throws CannotCompileException
    {
        Javac compiler = new Javac(declaring);
        try {
            if (delegateMethod != null)
                compiler.recordProceed(delegateObj, delegateMethod);

            CtMember obj = compiler.compile(src);
            if (obj instanceof CtMethod)
                return (CtMethod)obj;
        }
        catch (CompileError e) {
            throw new CannotCompileException(e);
        }

        throw new CannotCompileException("not a method");
    }

    /**
     * Creates a public (non-static) method.  The created method cannot
     * be changed to a static method later.
     *
     * @param returnType        the type of the returned value.
     * @param mname             the method name.
     * @param parameters        a list of the parameter types.
     * @param exceptions        a list of the exception types.
     * @param body              the source text of the method body.
     *                  It must be a block surrounded by <code>{}</code>.
     *                  If it is <code>null</code>, the created method
     *                  does nothing except returning zero or null.
     * @param declaring    the class to which the created method is added.
     */
    public static CtMethod make(CtClass returnType,
                                String mname, CtClass[] parameters,
                                CtClass[] exceptions,
                                String body, CtClass declaring)
        throws CannotCompileException
    {
        return make(Modifier.PUBLIC, returnType, mname, parameters, exceptions,
                    body, declaring);
    }

    /**
     * Creates a method.
     *
     * @param modifiers         access modifiers.
     * @param returnType        the type of the returned value.
     * @param mname             the method name.
     * @param parameters        a list of the parameter types.
     * @param exceptions        a list of the exception types.
     * @param body              the source text of the method body.
     *                  It must be a block surrounded by <code>{}</code>.
     *                  If it is <code>null</code>, the created method
     *                  does nothing except returning zero or null.
     * @param declaring    the class to which the created method is added.
     *
     * @see Modifier
     */
    public static CtMethod make(int modifiers, CtClass returnType,
                                String mname, CtClass[] parameters,
                                CtClass[] exceptions,
                                String body, CtClass declaring)
        throws CannotCompileException
    {
        try {
            CtMethod cm
                = new CtMethod(returnType, mname, parameters, declaring);
            cm.setModifiers(modifiers);
            cm.setExceptionTypes(exceptions);
            cm.setBody(body);
            return cm;
        }
        catch (NotFoundException e) {
            throw new CannotCompileException(e);
        }
    }

    /**
     * Creates a copy of a method.  This method is provided for creating
     * a new method based on an existing method.
     *
     * @param src       the source method.
     * @param declaring    the class to which the created method is added.
     * @param map       the hashtable associating original class names
     *                  with substituted names.
     *                  It can be <code>null</code>.
     *
     * @see CtMethod#CtMethod(CtMethod,CtClass,ClassMap)
     */
    public static CtMethod copy(CtMethod src, CtClass declaring,
                                ClassMap map) throws CannotCompileException {
        return new CtMethod(src, declaring, map);
    }

    /**
     * Creates a copy of a method with a new name.
     * This method is provided for creating
     * a new method based on an existing method.
     *
     * @param src       the source method.
     * @param name      the name of the created method.
     * @param declaring    the class to which the created method is added.
     * @param map       the hashtable associating original class names
     *                  with substituted names.
     *                  It can be <code>null</code>.
     *
     * @see CtMethod#CtMethod(CtMethod,CtClass,ClassMap)
     */
    public static CtMethod copy(CtMethod src, String name, CtClass declaring,
                                ClassMap map) throws CannotCompileException {
        CtMethod cm = new CtMethod(src, declaring, map);
        cm.setName(name);
        return cm;
    }

    /**
     * Creates a public abstract method.
     *
     * @param returnType        the type of the returned value
     * @param mname             the method name
     * @param parameters        a list of the parameter types
     * @param exceptions        a list of the exception types
     * @param declaring    the class to which the created method is added.
     *
     * @see CtMethod#CtMethod(CtClass,String,CtClass[],CtClass)
     */
    public static CtMethod abstractMethod(CtClass returnType,
                                          String mname,
                                          CtClass[] parameters,
                                          CtClass[] exceptions,
                                          CtClass declaring)
        throws NotFoundException
    {
        CtMethod cm = new CtMethod(returnType, mname, parameters, declaring);
        cm.setExceptionTypes(exceptions);
        return cm;
    }

    /**
     * Creates a public getter method.  The getter method returns the value
     * of the specified field in the class to which this method is added.
     * The created method is initially not static even if the field is
     * static.  Change the modifiers if the method should be static.
     *
     * @param methodName        the name of the getter
     * @param field             the field accessed.
     */
    public static CtMethod getter(String methodName, CtField field)
        throws CannotCompileException
    {
        FieldInfo finfo = field.getFieldInfo2();
        String fieldType = finfo.getDescriptor();
        String desc = "()" + fieldType;
        ConstPool cp = finfo.getConstPool();
        MethodInfo minfo = new MethodInfo(cp, methodName, desc);
        minfo.setAccessFlags(AccessFlag.PUBLIC);

        Bytecode code = new Bytecode(cp, 2, 1);
        try {
            String fieldName = finfo.getName();
            if ((finfo.getAccessFlags() & AccessFlag.STATIC) == 0) {
                code.addAload(0);
                code.addGetfield(Bytecode.THIS, fieldName, fieldType);
            }
            else
                code.addGetstatic(Bytecode.THIS, fieldName, fieldType);