/*
* Copyright 2000-2004 The Apache Software Foundation
*
* Licensed 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.bcel.util;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.util.Locale;
import org.apache.bcel.Constants;
import org.apache.bcel.Repository;
import org.apache.bcel.classfile.ClassParser;
import org.apache.bcel.classfile.ConstantValue;
import org.apache.bcel.classfile.Field;
import org.apache.bcel.classfile.JavaClass;
import org.apache.bcel.classfile.Method;
import org.apache.bcel.classfile.Utility;
import org.apache.bcel.generic.ArrayType;
import org.apache.bcel.generic.ConstantPoolGen;
import org.apache.bcel.generic.MethodGen;
import org.apache.bcel.generic.Type;
/**
* This class takes a given JavaClass object and converts it to a
* Java program that creates that very class using BCEL. This
* gives new users of BCEL a useful example showing how things
* are done with BCEL. It does not cover all features of BCEL,
* but tries to mimic hand-written code as close as possible.
*
* @version $Id: BCELifier.java 394939 2006-04-18 13:23:49Z tcurdt $
* @author <A HREF="mailto:m.dahm@gmx.de">M. Dahm</A>
*/
public class BCELifier extends org.apache.bcel.classfile.EmptyVisitor {
private static final int FLAG_FOR_UNKNOWN = -1;
private static final int FLAG_FOR_CLASS = 0;
private static final int FLAG_FOR_METHOD = 1;
private JavaClass _clazz;
private PrintWriter _out;
private ConstantPoolGen _cp;
/** @param clazz Java class to "decompile"
* @param out where to output Java program
*/
public BCELifier(JavaClass clazz, OutputStream out) {
_clazz = clazz;
_out = new PrintWriter(out);
_cp = new ConstantPoolGen(_clazz.getConstantPool());
}
/** Start Java code generation
*/
public void start() {
visitJavaClass(_clazz);
_out.flush();
}
public void visitJavaClass( JavaClass clazz ) {
String class_name = clazz.getClassName();
String super_name = clazz.getSuperclassName();
String package_name = clazz.getPackageName();
String inter = Utility.printArray(clazz.getInterfaceNames(), false, true);
if (!"".equals(package_name)) {
class_name = class_name.substring(package_name.length() + 1);
_out.println("package " + package_name + ";");
_out.println();
}
_out.println("import org.apache.bcel.generic.*;");
_out.println("import org.apache.bcel.classfile.*;");
_out.println("import org.apache.bcel.*;");
_out.println("import java.io.*;");
_out.println();
_out.println("public class " + class_name + "Creator implements Constants {");
_out.println(" private InstructionFactory _factory;");
_out.println(" private ConstantPoolGen _cp;");
_out.println(" private ClassGen _cg;");
_out.println();
_out.println(" public " + class_name + "Creator() {");
_out.println(" _cg = new ClassGen(\""
+ (("".equals(package_name)) ? class_name : package_name + "." + class_name)
+ "\", \"" + super_name + "\", " + "\"" + clazz.getSourceFileName() + "\", "
+ printFlags(clazz.getAccessFlags(), FLAG_FOR_CLASS) + ", " + "new String[] { "
+ inter + " });");
_out.println();
_out.println(" _cp = _cg.getConstantPool();");
_out.println(" _factory = new InstructionFactory(_cg, _cp);");
_out.println(" }");
_out.println();
printCreate();
Field[] fields = clazz.getFields();
if (fields.length > 0) {
_out.println(" private void createFields() {");
_out.println(" FieldGen field;");
for (int i = 0; i < fields.length; i++) {
fields[i].accept(this);
}
_out.println(" }");
_out.println();
}
Method[] methods = clazz.getMethods();
for (int i = 0; i < methods.length; i++) {
_out.println(" private void createMethod_" + i + "() {");
methods[i].accept(this);
_out.println(" }");
_out.println();
}
printMain();
_out.println("}");
}
private void printCreate() {
_out.println(" public void create(OutputStream out) throws IOException {");
Field[] fields = _clazz.getFields();
if (fields.length > 0) {
_out.println(" createFields();");
}
Method[] methods = _clazz.getMethods();
for (int i = 0; i < methods.length; i++) {
_out.println(" createMethod_" + i + "();");
}
_out.println(" _cg.getJavaClass().dump(out);");
_out.println(" }");
_out.println();
}
private void printMain() {
String class_name = _clazz.getClassName();
_out.println(" public static void main(String[] args) throws Exception {");
_out.println(" " + class_name + "Creator creator = new " + class_name + "Creator();");
_out.println(" creator.create(new FileOutputStream(\"" + class_name + ".class\"));");
_out.println(" }");
}
public void visitField( Field field ) {
_out.println();
_out.println(" field = new FieldGen(" + printFlags(field.getAccessFlags()) + ", "
+ printType(field.getSignature()) + ", \"" + field.getName() + "\", _cp);");
ConstantValue cv = field.getConstantValue();
if (cv != null) {
String value = cv.toString();
_out.println(" field.setInitValue(" + value + ")");
}
_out.println(" _cg.addField(field.getField());");
}
public void visitMethod( Method method ) {
MethodGen mg = new MethodGen(method, _clazz.getClassName(), _cp);
Type result_type = mg.getReturnType();
Type[] arg_types = mg.getArgumentTypes();
_out.println(" InstructionList il = new InstructionList();");
_out.println(" MethodGen method = new MethodGen("
+ printFlags(method.getAccessFlags(), FLAG_FOR_METHOD) + ", "
+ printType(result_type) + ", " + printArgumentTypes(arg_types) + ", "
+ "new String[] { " + Utility.printArray(mg.getArgumentNames(), false, true)
+ " }, \"" + method.getName() + "\", \"" + _clazz.getClassName() + "\", il, _cp);");
_out.println();
BCELFactory factory = new BCELFactory(mg, _out);
factory.start();
_out.println(" method.setMaxStack();");
_out.println(" method.setMaxLocals();");
_out.println(" _cg.addMethod(method.getMethod());");
_out.println(" il.dispose();");
}
static String printFlags( int flags ) {
return printFlags(flags, FLAG_FOR_UNKNOWN);
}
static String printFlags( int flags, int reason ) {
if (flags == 0) {
return "0";
}
StringBuffer buf = new StringBuffer();
for (int i = 0, pow = 1; pow <= Constants.MAX_ACC_FLAG; i++) {
if ((flags & pow) != 0) {
if ((pow == Constants.ACC_SYNCHRONIZED) && (reason == FLAG_FOR_CLASS)) {
buf.append("ACC_SUPER | ");
} else if ((pow == Constants.ACC_VOLATILE) && (reason == FLAG_FOR_METHOD)) {
buf.append("ACC_BRIDGE | ");
} else if ((pow == Constants.ACC_TRANSIENT) && (reason == FLAG_FOR_METHOD)) {
buf.append("ACC_VARARGS | ");
} else {
buf.append("ACC_")
.append(Constants.ACCESS_NAMES[i].toUpperCase(Locale.ENGLISH)).append(
" | ");
}
}
pow <<= 1;
}
String str = buf.toString();
return str.substring(0, str.length() - 3);
}
static String printArgumentTypes( Type[] arg_types ) {
if (arg_types.length == 0) {
return "Type.NO_ARGS";
}
StringBuffer args = new StringBuffer();
for (int i = 0; i < arg_types.length; i++) {
args.append(printType(arg_types[i]));
if (i < arg_types.length - 1) {
args.append(", ");
}
}
return "new Type[] { " + args.toString() + " }";
}
static String printType( Type type ) {
return printType(type.getSignature());
}
static String printType( String signature ) {
Type type = Type.getType(signature);
byte t = type.getType();
if (t <= Constants.T_VOID) {
return "Type." + Constants.TYPE_NAMES[t].toUpperCase(Locale.ENGLISH);
} else if (type.toString().equals("java.lang.String")) {
return "Type.STRING";
} else if (type.toString().equals("java.lang.Object")) {
return "Type.OBJECT";
} else if (type.toString().equals("java.lang.StringBuffer")) {
return "Type.STRINGBUFFER";
} else if (type instanceof ArrayType) {
ArrayType at = (ArrayType) type;
return "new ArrayType(" + printType(at.getBasicType()) + ", " + at.getDimensions()
+ ")";
} else {
return "new ObjectType(\"" + Utility.signatureToString(signature, false) + "\")";
}
}
/** Default main method
*/
public static void main( String[] argv ) throws Exception {
JavaClass java_class;
String name = argv[0];
if ((java_class = Repository.lookupClass(name)) == null) {
java_class = new ClassParser(name).parse(); // May throw IOException
}
BCELifier bcelifier = new BCELifier(java_class, System.out);
bcelifier.start();
}
}