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17 package org.apache.bcel.util;
18
19 import java.io.OutputStream;
20 import java.io.PrintWriter;
21 import java.util.Locale;
22 import org.apache.bcel.Constants;
23 import org.apache.bcel.Repository;
24 import org.apache.bcel.classfile.ClassParser;
25 import org.apache.bcel.classfile.ConstantValue;
26 import org.apache.bcel.classfile.Field;
27 import org.apache.bcel.classfile.JavaClass;
28 import org.apache.bcel.classfile.Method;
29 import org.apache.bcel.classfile.Utility;
30 import org.apache.bcel.generic.ArrayType;
31 import org.apache.bcel.generic.ConstantPoolGen;
32 import org.apache.bcel.generic.MethodGen;
33 import org.apache.bcel.generic.Type;
34
35 /***
36 * This class takes a given JavaClass object and converts it to a
37 * Java program that creates that very class using BCEL. This
38 * gives new users of BCEL a useful example showing how things
39 * are done with BCEL. It does not cover all features of BCEL,
40 * but tries to mimic hand-written code as close as possible.
41 *
42 * @version $Id: BCELifier.java 394939 2006-04-18 13:23:49Z tcurdt $
43 * @author <A HREF="mailto:m.dahm@gmx.de">M. Dahm</A>
44 */
45 public class BCELifier extends org.apache.bcel.classfile.EmptyVisitor {
46
47 private static final int FLAG_FOR_UNKNOWN = -1;
48 private static final int FLAG_FOR_CLASS = 0;
49 private static final int FLAG_FOR_METHOD = 1;
50 private JavaClass _clazz;
51 private PrintWriter _out;
52 private ConstantPoolGen _cp;
53
54
55 /*** @param clazz Java class to "decompile"
56 * @param out where to output Java program
57 */
58 public BCELifier(JavaClass clazz, OutputStream out) {
59 _clazz = clazz;
60 _out = new PrintWriter(out);
61 _cp = new ConstantPoolGen(_clazz.getConstantPool());
62 }
63
64
65 /*** Start Java code generation
66 */
67 public void start() {
68 visitJavaClass(_clazz);
69 _out.flush();
70 }
71
72
73 public void visitJavaClass( JavaClass clazz ) {
74 String class_name = clazz.getClassName();
75 String super_name = clazz.getSuperclassName();
76 String package_name = clazz.getPackageName();
77 String inter = Utility.printArray(clazz.getInterfaceNames(), false, true);
78 if (!"".equals(package_name)) {
79 class_name = class_name/substring(package_name/length() + 1)/package-summary.html">strong>_name = class_name.substring(package_name.length() + 1);
80 _out.println("package " + package_name + ";");
81 _out.println();
82 }
83 _out.println("import org.apache.bcel.generic.*;");
84 _out.println("import org.apache.bcel.classfile.*;");
85 _out.println("import org.apache.bcel.*;");
86 _out.println("import java.io.*;");
87 _out.println();
88 _out.println("public class " + class_name + "Creator implements Constants {");
89 _out.println(" private InstructionFactory _factory;");
90 _out.println(" private ConstantPoolGen _cp;");
91 _out.println(" private ClassGen _cg;");
92 _out.println();
93 _out.println(" public " + class_name + "Creator() {");
94 _out.println(" _cg = new ClassGen(\""
95 + (("".equals(package_name)) ? class_name : package_name + "." + class_name)
96 + "\", \"" + super_name + "\", " + "\"" + clazz.getSourceFileName() + "\", "
97 + printFlags(clazz.getAccessFlags(), FLAG_FOR_CLASS) + ", " + "new String[] { "
98 + inter + " });");
99 _out.println();
100 _out.println(" _cp = _cg.getConstantPool();");
101 _out.println(" _factory = new InstructionFactory(_cg, _cp);");
102 _out.println(" }");
103 _out.println();
104 printCreate();
105 Field[] fields = clazz.getFields();
106 if (fields.length > 0) {
107 _out.println(" private void createFields() {");
108 _out.println(" FieldGen field;");
109 for (int i = 0; i < fields.length; i++) {
110 fields[i].accept(this);
111 }
112 _out.println(" }");
113 _out.println();
114 }
115 Method[] methods = clazz.getMethods();
116 for (int i = 0; i < methods.length; i++) {
117 _out.println(" private void createMethod_" + i + "() {");
118 methods[i].accept(this);
119 _out.println(" }");
120 _out.println();
121 }
122 printMain();
123 _out.println("}");
124 }
125
126
127 private void printCreate() {
128 _out.println(" public void create(OutputStream out) throws IOException {");
129 Field[] fields = _clazz.getFields();
130 if (fields.length > 0) {
131 _out.println(" createFields();");
132 }
133 Method[] methods = _clazz.getMethods();
134 for (int i = 0; i < methods.length; i++) {
135 _out.println(" createMethod_" + i + "();");
136 }
137 _out.println(" _cg.getJavaClass().dump(out);");
138 _out.println(" }");
139 _out.println();
140 }
141
142
143 private void printMain() {
144 String class_name = _clazz.getClassName();
145 _out.println(" public static void main(String[] args) throws Exception {");
146 _out.println(" " + class_name + "Creator creator = new " + class_name + "Creator();");
147 _out.println(" creator.create(new FileOutputStream(\"" + class_name + ".class\"));");
148 _out.println(" }");
149 }
150
151
152 public void visitField( Field field ) {
153 _out.println();
154 _out.println(" field = new FieldGen(" + printFlags(field.getAccessFlags()) + ", "
155 + printType(field.getSignature()) + ", \"" + field.getName() + "\", _cp);");
156 ConstantValue cv = field.getConstantValue();
157 if (cv != null) {
158 String value = cv.toString();
159 _out.println(" field.setInitValue(" + value + ")");
160 }
161 _out.println(" _cg.addField(field.getField());");
162 }
163
164
165 public void visitMethod( Method method ) {
166 MethodGen mg = new MethodGen(method, _clazz.getClassName(), _cp);
167 Type result_type = mg.getReturnType();
168 Type[] arg_types = mg.getArgumentTypes();
169 _out.println(" InstructionList il = new InstructionList();");
170 _out.println(" MethodGen method = new MethodGen("
171 + printFlags(method.getAccessFlags(), FLAG_FOR_METHOD) + ", "
172 + printType(result_type) + ", " + printArgumentTypes(arg_types) + ", "
173 + "new String[] { " + Utility.printArray(mg.getArgumentNames(), false, true)
174 + " }, \"" + method.getName() + "\", \"" + _clazz.getClassName() + "\", il, _cp);");
175 _out.println();
176 BCELFactory factory = new BCELFactory(mg, _out);
177 factory.start();
178 _out.println(" method.setMaxStack();");
179 _out.println(" method.setMaxLocals();");
180 _out.println(" _cg.addMethod(method.getMethod());");
181 _out.println(" il.dispose();");
182 }
183
184
185 static String printFlags( int flags ) {
186 return printFlags(flags, FLAG_FOR_UNKNOWN);
187 }
188
189
190 static String printFlags( int flags, int reason ) {
191 if (flags == 0) {
192 return "0";
193 }
194 StringBuffer buf = new StringBuffer();
195 for (int i = 0, pow = 1; pow <= Constants.MAX_ACC_FLAG; i++) {
196 if ((flags & pow) != 0) {
197 if ((pow == Constants.ACC_SYNCHRONIZED) && (reason == FLAG_FOR_CLASS)) {
198 buf.append("ACC_SUPER | ");
199 } else if ((pow == Constants.ACC_VOLATILE) && (reason == FLAG_FOR_METHOD)) {
200 buf.append("ACC_BRIDGE | ");
201 } else if ((pow == Constants.ACC_TRANSIENT) && (reason == FLAG_FOR_METHOD)) {
202 buf.append("ACC_VARARGS | ");
203 } else {
204 buf.append("ACC_")
205 .append(Constants.ACCESS_NAMES[i].toUpperCase(Locale.ENGLISH)).append(
206 " | ");
207 }
208 }
209 pow <<= 1;
210 }
211 String str = buf.toString();
212 return str.substring(0, str.length() - 3);
213 }
214
215
216 static String printArgumentTypes( Type[] arg_types ) {
217 if (arg_types.length == 0) {
218 return "Type.NO_ARGS";
219 }
220 StringBuffer args = new StringBuffer();
221 for (int i = 0; i < arg_types.length; i++) {
222 args.append(printType(arg_types[i]));
223 if (i < arg_types.length - 1) {
224 args.append(", ");
225 }
226 }
227 return "new Type[] { " + args.toString() + " }";
228 }
229
230
231 static String printType( Type type ) {
232 return printType(type.getSignature());
233 }
234
235
236 static String printType( String signature ) {
237 Type type = Type.getType(signature);
238 byte t = type.getType();
239 if (t <= Constants.T_VOID) {
240 return "Type." + Constants.TYPE_NAMES[t].toUpperCase(Locale.ENGLISH);
241 } else if (type.toString().equals("java.lang.String")) {
242 return "Type.STRING";
243 } else if (type.toString().equals("java.lang.Object")) {
244 return "Type.OBJECT";
245 } else if (type.toString().equals("java.lang.StringBuffer")) {
246 return "Type.STRINGBUFFER";
247 } else if (type instanceof ArrayType) {
248 ArrayType at = (ArrayType) type;
249 return "new ArrayType(" + printType(at.getBasicType()) + ", " + at.getDimensions()
250 + ")";
251 } else {
252 return "new ObjectType(\"" + Utility.signatureToString(signature, false) + "\")";
253 }
254 }
255
256
257 /*** Default main method
258 */
259 public static void main( String[] argv ) throws Exception {
260 JavaClass java_class;
261 String name = argv[0];
262 if ((java_class = Repository.lookupClass(name)) == null) {
263 java_class = new ClassParser(name).parse();
264 }
265 BCELifier bcelifier = new BCELifier(java_class, System.out);
266 bcelifier.start();
267 }
268 }