classfile.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.bytecode;

import java.io.DataInputStream;
import java.io.DataOutputStream;
import java.io.IOException;
import java.util.ArrayList;
import java.util.LinkedList;
import java.util.List;
import java.util.ListIterator;
import java.util.Map;
import javassist.CannotCompileException;

/**
 * <code>ClassFile</code> represents a Java <code>.class</code> file, which
 * consists of a constant pool, methods, fields, and attributes.
 * 
 * @see javassist.CtClass#getClassFile()
 */
public final class ClassFile {
    int major, minor; // version number
    ConstPool constPool;
    int thisClass;
    int accessFlags;
    int superClass;
    int[] interfaces;
    ArrayList fields;
    ArrayList methods;
    LinkedList attributes;
    String thisclassname; // not JVM-internal name
    String[] cachedInterfaces;
    String cachedSuperclass;

    /**
     * Constructs a class file from a byte stream.
     */
    public ClassFile(DataInputStream in) throws IOException {
        read(in);
    }

    /**
     * Constructs a class file including no members.
     * 
     * @param isInterface
     *            true if this is an interface. false if this is a class.
     * @param classname
     *            a fully-qualified class name
     * @param superclass
     *            a fully-qualified super class name
     */
    public ClassFile(boolean isInterface, String classname, String superclass) {
        major = 45;
        minor = 3; // JDK 1.1 or later
        constPool = new ConstPool(classname);
        thisClass = constPool.getThisClassInfo();
        if (isInterface)
            accessFlags = AccessFlag.SUPER | AccessFlag.INTERFACE
                    | AccessFlag.ABSTRACT;
        else
            accessFlags = AccessFlag.SUPER;

        initSuperclass(superclass);
        interfaces = null;
        fields = new ArrayList();
        methods = new ArrayList();
        thisclassname = classname;

        attributes = new LinkedList();
        attributes.add(new SourceFileAttribute(constPool,
                getSourcefileName(thisclassname)));
    }

    private void initSuperclass(String superclass) {
        if (superclass != null) {
            this.superClass = constPool.addClassInfo(superclass);
            cachedSuperclass = superclass;
        }
        else {
            this.superClass = constPool.addClassInfo("java.lang.Object");
            cachedSuperclass = "java.lang.Object";
        }
    }

    private static String getSourcefileName(String qname) {
        int index = qname.lastIndexOf('.');
        if (index >= 0)
            qname = qname.substring(index + 1);

        return qname + ".java";
    }

    /**
     * Eliminates dead constant pool items. If a method or a field is removed,
     * the constant pool items used by that method/field become dead items. This
     * method recreates a constant pool.
     */
    public void compact() {
        ConstPool cp = compact0();
        ArrayList list = methods;
        int n = list.size();
        for (int i = 0; i < n; ++i) {
            MethodInfo minfo = (MethodInfo)list.get(i);
            minfo.compact(cp);
        }

        list = fields;
        n = list.size();
        for (int i = 0; i < n; ++i) {
            FieldInfo finfo = (FieldInfo)list.get(i);
            finfo.compact(cp);
        }

        attributes = AttributeInfo.copyAll(attributes, cp);
        constPool = cp;
    }

    private ConstPool compact0() {
        ConstPool cp = new ConstPool(thisclassname);
        thisClass = cp.getThisClassInfo();
        String sc = getSuperclass();
        if (sc != null)
            superClass = cp.addClassInfo(getSuperclass());

        if (interfaces != null) {
            int n = interfaces.length;
            for (int i = 0; i < n; ++i)
                interfaces[i]
                    = cp.addClassInfo(constPool.getClassInfo(interfaces[i]));
        }

        return cp;
    }

    /**
     * Discards all attributes, associated with both the class file and the
     * members such as a code attribute and exceptions attribute. The unused
     * constant pool entries are also discarded (a new packed constant pool is
     * constructed).
     */
    public void prune() {
        ConstPool cp = compact0();
        LinkedList newAttributes = new LinkedList();
        AttributeInfo invisibleAnnotations
            = getAttribute(AnnotationsAttribute.invisibleTag);
        if (invisibleAnnotations != null) {
            invisibleAnnotations = invisibleAnnotations.copy(cp, null);
            newAttributes.add(invisibleAnnotations);
        }

        AttributeInfo visibleAnnotations
            = getAttribute(AnnotationsAttribute.visibleTag);
        if (visibleAnnotations != null) {
            visibleAnnotations = visibleAnnotations.copy(cp, null);
            newAttributes.add(visibleAnnotations);
        }

        ArrayList list = methods;
        int n = list.size();
        for (int i = 0; i < n; ++i) {
            MethodInfo minfo = (MethodInfo)list.get(i);
            minfo.prune(cp);
        }

        list = fields;
        n = list.size();
        for (int i = 0; i < n; ++i) {
            FieldInfo finfo = (FieldInfo)list.get(i);
            finfo.prune(cp);
        }

        attributes = newAttributes;
        cp.prune();
        constPool = cp;
    }

    /**
     * Returns a constant pool table.
     */
    public ConstPool getConstPool() {
        return constPool;
    }

    /**
     * Returns true if this is an interface.
     */
    public boolean isInterface() {
        return (accessFlags & AccessFlag.INTERFACE) != 0;
    }

    /**
     * Returns true if this is a final class or interface.
     */
    public boolean isFinal() {
        return (accessFlags & AccessFlag.FINAL) != 0;
    }

    /**
     * Returns true if this is an abstract class or an interface.
     */
    public boolean isAbstract() {
        return (accessFlags & AccessFlag.ABSTRACT) != 0;
    }

    /**
     * Returns access flags.
     * 
     * @see javassist.bytecode.AccessFlag
     */
    public int getAccessFlags() {
        return accessFlags;
    }

    /**
     * Changes access flags.
     * 
     * @see javassist.bytecode.AccessFlag
     */
    public void setAccessFlags(int acc) {
        accessFlags = acc | AccessFlag.SUPER;
    }

    /**
     * Returns access and property flags of this nested class.
     * This method returns -1 if the class is not a nested class. 
     *
     * <p>The returned value is obtained from <code>inner_class_access_flags</code>
     * of the entry representing this nested class itself
     * in <code>InnerClasses_attribute</code>>. 
     */
    public int getInnerAccessFlags() {
        InnerClassesAttribute ica
            = (InnerClassesAttribute)getAttribute(InnerClassesAttribute.tag);
        if (ica == null)
            return -1;

        String name = getName();
        int n = ica.tableLength();
        for (int i = 0; i < n; ++i)
            if (name.equals(ica.innerClass(i)))
                return ica.accessFlags(i);

        return -1;
    }

    /**
     * Returns the class name.
     */
    public String getName() {
        return thisclassname;
    }

    /**
     * Sets the class name. This method substitutes the new name for all
     * occurrences of the old class name in the class file.
     */
    public void setName(String name) {
        renameClass(thisclassname, name);
    }

    /**
     * Returns the super class name.
     */
    public String getSuperclass() {
        if (cachedSuperclass == null)
            cachedSuperclass = constPool.getClassInfo(superClass);

        return cachedSuperclass;
    }

    /**
     * Returns the index of the constant pool entry representing the super
     * class.
     */
    public int getSuperclassId() {
        return superClass;
    }

    /**
     * Sets the super class.
     * 
     * <p>
     * This method modifies constructors so that they call constructors declared
     * in the new super class.
     */
    public void setSuperclass(String superclass) throws CannotCompileException {
        if (superclass == null)
            superclass = "java.lang.Object";

        try {
            this.superClass = constPool.addClassInfo(superclass);
            ArrayList list = methods;
            int n = list.size();
            for (int i = 0; i < n; ++i) {
                MethodInfo minfo = (MethodInfo)list.get(i);
                minfo.setSuperclass(superclass);
            }
        }
        catch (BadBytecode e) {
            throw new CannotCompileException(e);
        }
        cachedSuperclass = superclass;
    }

    /**
     * Replaces all occurrences of a class name in the class file.
     * 
     * <p>
     * If class X is substituted for class Y in the class file, X and Y must
     * have the same signature. If Y provides a method m(), X must provide it
     * even if X inherits m() from the super class. If this fact is not
     * guaranteed, the bytecode verifier may cause an error.
     * 
     * @param oldname
     *            the replaced class name
     * @param newname
     *            the substituted class name
     */
    public final void renameClass(String oldname, String newname) {
        ArrayList list;
        int n;

        if (oldname.equals(newname))
            return;

        if (oldname.equals(thisclassname))
            thisclassname = newname;

        oldname = Descriptor.toJvmName(oldname);
        newname = Descriptor.toJvmName(newname);
        constPool.renameClass(oldname, newname);

        list = methods;
        n = list.size();
        for (int i = 0; i < n; ++i) {
            MethodInfo minfo = (MethodInfo)list.get(i);
            String desc = minfo.getDescriptor();
            minfo.setDescriptor(Descriptor.rename(desc, oldname, newname));
        }

        list = fields;
        n = list.size();
        for (int i = 0; i < n; ++i) {
            FieldInfo finfo = (FieldInfo)list.get(i);
            String desc = finfo.getDescriptor();
            finfo.setDescriptor(Descriptor.rename(desc, oldname, newname));
        }
    }

    /**
     * Replaces all occurrences of several class names in the class file.
     * 
     * @param classnames
     *            specifies which class name is replaced with which new name.
     *            Class names must be described with the JVM-internal
     *            representation like <code>java/lang/Object</code>.
     * @see #renameClass(String,String)
     */
    public final void renameClass(Map classnames) {
        String jvmNewThisName = (String)classnames.get(Descriptor
                .toJvmName(thisclassname));
        if (jvmNewThisName != null)
            thisclassname = Descriptor.toJavaName(jvmNewThisName);

        constPool.renameClass(classnames);