Java Code Examples for javassist.bytecode.MethodInfo#getCodeAttribute()

/**
 * Get method arg names.
 *
 * @param clazz
 * @param methodName
 * @return
 */
public static <T> String[] getMethodArgNames(Class<T> clazz, String methodName) {
    try {
        ClassPool pool = ClassPool.getDefault();
        CtClass cc = pool.get(clazz.getName());

        CtMethod cm = cc.getDeclaredMethod(methodName);

        // 使用javaassist的反射方法获取方法的参数名
        MethodInfo methodInfo = cm.getMethodInfo();
        CodeAttribute codeAttribute = methodInfo.getCodeAttribute();
        LocalVariableAttribute attr = (LocalVariableAttribute) codeAttribute.getAttribute(LocalVariableAttribute.tag);
        if (attr == null) {
            throw new RuntimeException("LocalVariableAttribute of method is null! Class " + clazz.getName() + ",method name is " + methodName);
        }
        String[] paramNames = new String[cm.getParameterTypes().length];
        int pos = Modifier.isStatic(cm.getModifiers()) ? 0 : 1;
        for (int i = 0; i < paramNames.length; i++)
            paramNames[i] = attr.variableName(i + pos);

        return paramNames;
    } catch (NotFoundException e) {
        throw new RuntimeException(e.getMessage(), e);
    }
}
 

private static String[] getMethodParamNames(CtMethod ctMethod) throws RuntimeException {
    CtClass ctClass = ctMethod.getDeclaringClass();
    MethodInfo methodInfo = ctMethod.getMethodInfo();
    CodeAttribute codeAttribute = methodInfo.getCodeAttribute();
    LocalVariableAttribute attr = (LocalVariableAttribute) codeAttribute.getAttribute(LocalVariableAttribute.tag);
    if (attr == null) {
        throw new RuntimeException(ctClass.getName());
    }
    try {
        String[] paramNames = new String[ctMethod.getParameterTypes().length];
        int pos = Modifier.isStatic(ctMethod.getModifiers()) ? 0 : 1;
        for (int i = 0; i < paramNames.length; i++) {
            paramNames[i] = attr.variableName(i + pos);
        }
        return paramNames;
    } catch (Exception e) {
        throw new RuntimeException(e);
    }
}
 

public String[] getParameterNameByMethod(Method method) throws NotFoundException {
	CtMethod ctm = ct.getDeclaredMethod(method.getName());
	MethodInfo methodInfo = ctm.getMethodInfo();
	CodeAttribute codeAttribute = methodInfo.getCodeAttribute();
	LocalVariableAttribute attr = (LocalVariableAttribute)codeAttribute.getAttribute(LocalVariableAttribute.tag);
	String[] params = null;
	if (attr != null) {
		int len = ctm.getParameterTypes().length;
		params = new String[len];
		TreeMap<Integer, String> sortMap = Maps.newTreeMap();
		for (int i = 0; i < attr.tableLength(); i++)
			sortMap.put(attr.index(i), attr.variableName(i));
		int pos = Modifier.isStatic(ctm.getModifiers()) ? 0 : 1;
		params = Arrays.copyOfRange(sortMap.values().toArray(new String[0]), pos, params.length + pos);
	}
	return params;
}
 

/**
 * get method parameter names
 * @param cls
 * @param method
 * @return
 * @throws Exception
 */
public static String[] getParamNames(Class<?> cls, Method method) throws Exception {
    ClassPool pool = ClassPool.getDefault();
    CtClass cc = pool.get(cls.getName());

    Class<?>[] paramAry = method.getParameterTypes();
    String[] paramTypeNames = new String[paramAry.length];
    for (int i = 0; i < paramAry.length; i++) {
        paramTypeNames[i] = paramAry[i].getName();
    }

    CtMethod cm = cc.getDeclaredMethod(method.getName(), pool.get(paramTypeNames));

    MethodInfo methodInfo = cm.getMethodInfo();
    CodeAttribute codeAttribute = methodInfo.getCodeAttribute();
    LocalVariableAttribute attr = (LocalVariableAttribute) codeAttribute.getAttribute(LocalVariableAttribute.tag);
    if (attr == null) {
        throw new Exception("class:" + cls.getName() + ", have no LocalVariableTable, please use javac -g:{vars} to compile the source file");
    }
    String[] paramNames = new String[cm.getParameterTypes().length];
    int pos = Modifier.isStatic(cm.getModifiers()) ? 0 : 1;
    for (int i = 0; i < paramNames.length; i++) {
        paramNames[i] = attr.variableName(i + pos);
    }
    return paramNames;
}
 

private void initMethodParamInfo(Object controller, String methodName) {
	methodParamInfo = new LinkedHashMap<Class<?>, String>();
	Class<?> clazz = controller.getClass();
	try {
		ClassPool classPool = ClassPool.getDefault();
		classPool.insertClassPath(new ClassClassPath(clazz));
		CtClass ctClass = classPool.get(clazz.getName());
		CtMethod ctMethod = ctClass.getDeclaredMethod(methodName);

		MethodInfo methodInfo = ctMethod.getMethodInfo();
		CodeAttribute codeAttribute = methodInfo.getCodeAttribute();
		LocalVariableAttribute attr = (LocalVariableAttribute) codeAttribute
				.getAttribute("LocalVariableTable");

		CtClass[] parameterTypes = ctMethod.getParameterTypes();
		int pos = Modifier.isStatic(ctMethod.getModifiers()) ? 0 : 1;
		for (int i = 0; i < parameterTypes.length; i++)
			methodParamInfo.put(Class.forName(parameterTypes[i].getName()),
					attr.variableName(i + pos));
	} catch (Exception e) {
		throw new RuntimeException(e.getMessage());
	}
}
 

/**
 * 获取方法参数名称
 * 
 * @param cm <br>
 * @return <br>
 * @throws NotFoundException <br>
 * @throws UtilException 如果最终编译的class文件不包含局部变量表信息 <br>
 */
protected static String[] getMethodParamNames(final CtMethod cm) throws NotFoundException, UtilException {
    CtClass cc = cm.getDeclaringClass();
    MethodInfo methodInfo = cm.getMethodInfo();
    CodeAttribute codeAttribute = methodInfo.getCodeAttribute();
    if (codeAttribute == null) {
        throw new UtilException(ErrorCodeDef.CAN_NOT_FIND_VER_NAME_10003, cc.getName());
    }
    LocalVariableAttribute attr = (LocalVariableAttribute) codeAttribute.getAttribute(LocalVariableAttribute.tag);
    if (null == attr) {
        throw new UtilException(ErrorCodeDef.CAN_NOT_FIND_VER_NAME_10003, cc.getName());
    }
    String[] paramNames = new String[cm.getParameterTypes().length];
    int pos = Modifier.isStatic(cm.getModifiers()) ? 0 : 1;
    for (int i = 0; i < paramNames.length; i++) {
        paramNames[i] = attr.variableName(i + pos);
    }
    return paramNames;
}
 

@Test
public void givenJavaClass_whenLoadAtByJavassist_thenTraversWholeClass() throws NotFoundException, CannotCompileException, BadBytecode {
    // given
    ClassPool cp = ClassPool.getDefault();
    ClassFile cf = cp.get("com.baeldung.javasisst.Point").getClassFile();
    MethodInfo minfo = cf.getMethod("move");
    CodeAttribute ca = minfo.getCodeAttribute();
    CodeIterator ci = ca.iterator();

    // when
    List<String> operations = new LinkedList<>();
    while (ci.hasNext()) {
        int index = ci.next();
        int op = ci.byteAt(index);
        operations.add(Mnemonic.OPCODE[op]);
    }

    // then
    assertEquals(operations, Arrays.asList("aload_0", "iload_1", "putfield", "aload_0", "iload_2", "putfield", "return"));

}
 

/**
 * 基于javassist获取类方法参数名称
 * @param method
 * @return
 * @throws Exception
 */
public static String[] getMethodParamsName(Method method) throws Exception{
    Class<?> clazz = method.getDeclaringClass();
    ClassPool pool = ClassPool.getDefault();
    CtClass clz = pool.get(clazz.getName());
    CtClass[] params = new CtClass[method.getParameterTypes().length];
    for (int i = 0; i < method.getParameterTypes().length; i++) {
        params[i] = pool.getCtClass(method.getParameterTypes()[i].getName());
    }
    CtMethod cm = clz.getDeclaredMethod(method.getName(), params);
    MethodInfo methodInfo = cm.getMethodInfo();
    CodeAttribute codeAttribute = methodInfo.getCodeAttribute();
    if (codeAttribute==null) {
        return null;
    }
    LocalVariableAttribute attr = (LocalVariableAttribute) codeAttribute
            .getAttribute(LocalVariableAttribute.tag);
    int pos = Modifier.isStatic(cm.getModifiers()) ? 0 : 1;
    String[] paramNames = new String[cm.getParameterTypes().length];
    if (attr==null) {
        return null;
    }
    for (int i = 0; i < paramNames.length; i++) {
        paramNames[i] = attr.variableName(i + pos);
    }
    return paramNames;
}
 

private void transformInvokevirtualsIntoPutAndGetfields(ClassFile classfile)
		throws CannotCompileException {
	List methods = classfile.getMethods();
	for (Iterator method_iter = methods.iterator(); method_iter.hasNext();) {
		MethodInfo minfo = (MethodInfo) method_iter.next();
		String methodName = minfo.getName();
		if (methodName.startsWith(EACH_READ_METHOD_PREFIX)
		    || methodName.startsWith(EACH_WRITE_METHOD_PREFIX)
		    || methodName.equals(GETFIELDHANDLER_METHOD_NAME)
		    || methodName.equals(SETFIELDHANDLER_METHOD_NAME)) {
			continue;
		}
		CodeAttribute codeAttr = minfo.getCodeAttribute();
		if (codeAttr == null) {
			return;
		}
		CodeIterator iter = codeAttr.iterator();
		while (iter.hasNext()) {
			try {
				int pos = iter.next();
				pos = transformInvokevirtualsIntoGetfields(classfile, iter,
				                                           pos);
				pos = transformInvokevirtualsIntoPutfields(classfile, iter,
				                                           pos);

			} catch (BadBytecode e) {
				throw new CannotCompileException(e);
			}
		}
	}
}
 

private CodeAttribute getMethodCodeAttribute(Signature methodSignature) 
throws MethodNotFoundException, MethodCodeNotFoundException {
    final MethodInfo m = findMethodDeclaration(methodSignature);
    if (m == null) { 
        throw new MethodNotFoundException(methodSignature.toString());
    }
    final CodeAttribute ca = m.getCodeAttribute();
    if (ca == null) {
        throw new MethodCodeNotFoundException(methodSignature.toString()); 
    }
    return ca;
}
 

@Override
public boolean hasMethodImplementation(Signature methodSignature) {
    final MethodInfo m = findMethodDeclaration(methodSignature);
    return (m != null && (m.getCodeAttribute() != null || Modifier.isNative(AccessFlag.toModifier(m.getAccessFlags()))));
}