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

        ArrayList list = methods;
        int 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, classnames));
        }

        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, classnames));
        }
    }

    /**
     * Returns the names of the interfaces implemented by the class.
     * The returned array is read only.
     */
    public String[] getInterfaces() {
        if (cachedInterfaces != null)
            return cachedInterfaces;

        String[] rtn = null;
        if (interfaces == null)
            rtn = new String[0];
        else {
            int n = interfaces.length;
            String[] list = new String[n];
            for (int i = 0; i < n; ++i)
                list[i] = constPool.getClassInfo(interfaces[i]);

            rtn = list;
        }

        cachedInterfaces = rtn;
        return rtn;
    }

    /**
     * Sets the interfaces.
     * 
     * @param nameList
     *            the names of the interfaces.
     */
    public void setInterfaces(String[] nameList) {
        cachedInterfaces = null;
        if (nameList != null) {
            int n = nameList.length;
            interfaces = new int[n];
            for (int i = 0; i < n; ++i)
                interfaces[i] = constPool.addClassInfo(nameList[i]);
        }
    }

    /**
     * Appends an interface to the interfaces implemented by the class.
     */
    public void addInterface(String name) {
        cachedInterfaces = null;
        int info = constPool.addClassInfo(name);
        if (interfaces == null) {
            interfaces = new int[1];
            interfaces[0] = info;
        }
        else {
            int n = interfaces.length;
            int[] newarray = new int[n + 1];
            System.arraycopy(interfaces, 0, newarray, 0, n);
            newarray[n] = info;
            interfaces = newarray;
        }
    }

    /**
     * Returns all the fields declared in the class.
     * 
     * @return a list of <code>FieldInfo</code>.
     * @see FieldInfo
     */
    public List getFields() {
        return fields;
    }

    /**
     * Appends a field to the class.
     *
     * @throws DuplicateMemberException         when the field is already included.
     */
    public void addField(FieldInfo finfo) throws DuplicateMemberException {
        testExistingField(finfo.getName(), finfo.getDescriptor());
        fields.add(finfo);
    }

    private void addField0(FieldInfo finfo) {
        fields.add(finfo);
    }

    private void testExistingField(String name, String descriptor)
            throws DuplicateMemberException {
        ListIterator it = fields.listIterator(0);
        while (it.hasNext()) {
            FieldInfo minfo = (FieldInfo)it.next();
            if (minfo.getName().equals(name))
                throw new DuplicateMemberException("duplicate field: " + name);
        }
    }

    /**
     * Returns all the methods declared in the class.
     * 
     * @return a list of <code>MethodInfo</code>.
     * @see MethodInfo
     */
    public List getMethods() {
        return methods;
    }

    /**
     * Returns the method with the specified name. If there are multiple methods
     * with that name, this method returns one of them.
     * 
     * @return null if no such a method is found.
     */
    public MethodInfo getMethod(String name) {
        ArrayList list = methods;
        int n = list.size();
        for (int i = 0; i < n; ++i) {
            MethodInfo minfo = (MethodInfo)list.get(i);
            if (minfo.getName().equals(name))
                return minfo;
        }

        return null;
    }

    /**
     * Returns a static initializer (class initializer), or null if it does not
     * exist.
     */
    public MethodInfo getStaticInitializer() {
        return getMethod(MethodInfo.nameClinit);
    }

    /**
     * Appends a method to the class.
     *
     * @throws DuplicateMemberException         when the method is already included.
     */
    public void addMethod(MethodInfo minfo) throws DuplicateMemberException {
        testExistingMethod(minfo);
        methods.add(minfo);
    }

    private void addMethod0(MethodInfo minfo) {
        methods.add(minfo);
    }

    private void testExistingMethod(MethodInfo newMinfo)
        throws DuplicateMemberException
    {
        String name = newMinfo.getName();
        String descriptor = newMinfo.getDescriptor();
        ListIterator it = methods.listIterator(0);
        while (it.hasNext()) {
            MethodInfo minfo = (MethodInfo)it.next();
            if (minfo.getName().equals(name)
                    && notBridgeMethod(minfo) && notBridgeMethod(newMinfo)
                    && Descriptor.eqParamTypes(minfo.getDescriptor(),
                                               descriptor))
                throw new DuplicateMemberException("duplicate method: " + name
                                                 + " in " + this.getName());
        }
    }

    /* For a bridge method, see Sec. 15.12.4.5 of JLS 3rd Ed.
     */
    private boolean notBridgeMethod(MethodInfo minfo) {
        return (minfo.getAccessFlags() & AccessFlag.BRIDGE) == 0;
    }

    /**
     * Returns all the attributes.  The returned <code>List</code> object
     * is shared with this object.  If you add a new attribute to the list,
     * the attribute is also added to the classs file represented by this
     * object.  If you remove an attribute from the list, it is also removed
     * from the class file.
     * 
     * @return a list of <code>AttributeInfo</code> objects.
     * @see AttributeInfo
     */
    public List getAttributes() {
        return attributes;
    }

    /**
     * Returns the attribute with the specified name.  If there are multiple
     * attributes with that name, this method returns either of them.   It
     * returns null if the specified attributed is not found.
     * 
     * @param name          attribute name
     * @see #getAttributes()
     */
    public AttributeInfo getAttribute(String name) {
        LinkedList list = attributes;
        int n = list.size();
        for (int i = 0; i < n; ++i) {
            AttributeInfo ai = (AttributeInfo)list.get(i);
            if (ai.getName().equals(name))
                return ai;
        }

        return null;
    }

    /**
     * Appends an attribute. If there is already an attribute with the same
     * name, the new one substitutes for it.
     *
     * @see #getAttributes()
     */
    public void addAttribute(AttributeInfo info) {
        AttributeInfo.remove(attributes, info.getName());
        attributes.add(info);
    }

    /**
     * Returns the source file containing this class.
     * 
     * @return null if this information is not available.
     */
    public String getSourceFile() {
        SourceFileAttribute sf
            = (SourceFileAttribute)getAttribute(SourceFileAttribute.tag);
        if (sf == null)
            return null;
        else
            return sf.getFileName();
    }

    private void read(DataInputStream in) throws IOException {
        int i, n;
        int magic = in.readInt();
        if (magic != 0xCAFEBABE)
            throw new IOException("non class file");

        minor = in.readUnsignedShort();
        major = in.readUnsignedShort();
        constPool = new ConstPool(in);
        accessFlags = in.readUnsignedShort();
        thisClass = in.readUnsignedShort();
        constPool.setThisClassInfo(thisClass);
        superClass = in.readUnsignedShort();
        n = in.readUnsignedShort();
        if (n == 0)
            interfaces = null;
        else {
            interfaces = new int[n];
            for (i = 0; i < n; ++i)
                interfaces[i] = in.readUnsignedShort();
        }

        ConstPool cp = constPool;
        n = in.readUnsignedShort();
        fields = new ArrayList();
        for (i = 0; i < n; ++i)
            addField0(new FieldInfo(cp, in));

        n = in.readUnsignedShort();
        methods = new ArrayList();
        for (i = 0; i < n; ++i)
            addMethod0(new MethodInfo(cp, in));

        attributes = new LinkedList();
        n = in.readUnsignedShort();
        for (i = 0; i < n; ++i)
            addAttribute(AttributeInfo.read(cp, in));

        thisclassname = constPool.getClassInfo(thisClass);
    }

    /**
     * Writes a class file represened by this object into an output stream.
     */
    public void write(DataOutputStream out) throws IOException {
        int i, n;

        out.writeInt(0xCAFEBABE); // magic
        out.writeShort(minor); // minor version
        out.writeShort(major); // major version
        constPool.write(out); // constant pool
        out.writeShort(accessFlags);
        out.writeShort(thisClass);
        out.writeShort(superClass);

        if (interfaces == null)
            n = 0;
        else
            n = interfaces.length;

        out.writeShort(n);
        for (i = 0; i < n; ++i)
            out.writeShort(interfaces[i]);

        ArrayList list = fields;
        n = list.size();
        out.writeShort(n);
        for (i = 0; i < n; ++i) {
            FieldInfo finfo = (FieldInfo)list.get(i);
            finfo.write(out);
        }

        list = methods;
        n = list.size();
        out.writeShort(n);
        for (i = 0; i < n; ++i) {
            MethodInfo minfo = (MethodInfo)list.get(i);
            minfo.write(out);
        }

        out.writeShort(attributes.size());
        AttributeInfo.writeAll(attributes, out);
    }

    /**
     * Get the Major version.
     * 
     * @return the major version
     */
    public int getMajorVersion() {
        return major;
    }

    /**
     * Set the major version.
     * 
     * @param major
     *            the major version
     */
    public void setMajorVersion(int major) {
        this.major = major;
    }

    /**
     * Get the minor version.
     * 
     * @return the minor version
     */
    public int getMinorVersion() {
        return minor;
    }

    /**
     * Set the minor version.
     * 
     * @param minor
     *            the minor version
     */
    public void setMinorVersion(int minor) {
        this.minor = minor;
    }

    /**
     * Sets the major and minor version to Java 5.
     *
     * If the major version is older than 49, Java 5
     * extensions such as annotations are ignored
     * by the JVM.
     */
    public void setVersionToJava5() {
        this.major = 49;
        this.minor = 0;
    }
}