org.apache.cxf.common.util.ParamReader Maven / Gradle / Ivy
/**
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you 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.cxf.common.util;
// import org.apache.axis.utils.Messages;
import java.io.IOException;
import java.lang.reflect.Constructor;
import java.lang.reflect.Member;
import java.lang.reflect.Method;
import java.lang.reflect.Modifier;
import java.lang.reflect.Proxy;
import java.util.HashMap;
import java.util.Map;
/**
* This is the class file reader for obtaining the parameter names for declared
* methods in a class. The class must have debugging attributes for us to obtain
* this information.
*
* This does not work for inherited methods. To obtain parameter names for
* inherited methods, you must use a paramReader for the class that originally
* declared the method.
*
* don't get tricky, it's the bare minimum. Instances of this class are not
* threadsafe -- don't share them.
*/
public class ParamReader extends ClassReader {
private String methodName;
private Map methods = new HashMap();
private Class[] paramTypes;
/**
* process a class file, given it's class. We'll use the defining
* classloader to locate the bytecode.
*
* @param c
* @throws IOException
*/
public ParamReader(Class c) throws IOException {
this(getBytes(c));
}
/**
* process the given class bytes directly.
*
* @param b
* @throws IOException
*/
public ParamReader(byte[] b) throws IOException {
super(b, findAttributeReaders(ParamReader.class));
// check the magic number
if (readInt() != 0xCAFEBABE) {
// not a class file!
throw new IOException();
}
readShort(); // minor version
readShort(); // major version
readCpool(); // slurp in the constant pool
readShort(); // access flags
readShort(); // this class name
readShort(); // super class name
int count = readShort(); // ifaces count
for (int i = 0; i < count; i++) {
readShort(); // interface index
}
count = readShort(); // fields count
for (int i = 0; i < count; i++) {
readShort(); // access flags
readShort(); // name index
readShort(); // descriptor index
skipAttributes(); // field attributes
}
count = readShort(); // methods count
for (int i = 0; i < count; i++) {
readShort(); // access flags
int m = readShort(); // name index
String name = resolveUtf8(m);
int d = readShort(); // descriptor index
this.methodName = name + resolveUtf8(d);
readAttributes(); // method attributes
}
}
/**
* Retrieve a list of function parameter names from a method Returns null if
* unable to read parameter names (i.e. bytecode not built with debug).
*/
public static String[] getParameterNamesFromDebugInfo(Method method) {
// Don't worry about it if there are no params.
int numParams = method.getParameterTypes().length;
if (numParams == 0) {
return null;
}
// get declaring class
Class c = method.getDeclaringClass();
// Don't worry about it if the class is a Java dynamic proxy
if (Proxy.isProxyClass(c)) {
return null;
}
try {
// get a parameter reader
ParamReader pr = new ParamReader(c);
// get the parameter names
try {
return pr.getParameterNames(method);
} finally {
pr.close();
}
} catch (IOException e) {
// log it and leave
// log.info(Messages.getMessage("error00") + ":" + e);
return null;
}
}
public void readCode() throws IOException {
readShort(); // max stack
int maxLocals = readShort(); // max locals
MethodInfo info = new MethodInfo(maxLocals);
if (methods != null && methodName != null) {
methods.put(methodName, info);
}
skipFully(readInt()); // code
skipFully(8 * readShort()); // exception table
// read the code attributes (recursive). This is where
// we will find the LocalVariableTable attribute.
readAttributes();
}
/**
* return the names of the declared parameters for the given constructor. If
* we cannot determine the names, return null. The returned array will have
* one name per parameter. The length of the array will be the same as the
* length of the Class[] array returned by Constructor.getParameterTypes().
*
* @param ctor
* @return String[] array of names, one per parameter, or null
*/
public String[] getParameterNames(Constructor ctor) {
paramTypes = ctor.getParameterTypes();
return getParameterNames(ctor, paramTypes);
}
/**
* return the names of the declared parameters for the given method. If we
* cannot determine the names, return null. The returned array will have one
* name per parameter. The length of the array will be the same as the
* length of the Class[] array returned by Method.getParameterTypes().
*
* @param method
* @return String[] array of names, one per parameter, or null
*/
public String[] getParameterNames(Method method) {
paramTypes = method.getParameterTypes();
return getParameterNames(method, paramTypes);
}
protected String[] getParameterNames(Member member, Class[] pTypes) {
// look up the names for this method
MethodInfo info = methods.get(getSignature(member, pTypes));
// we know all the local variable names, but we only need to return
// the names of the parameters.
if (info != null) {
String[] paramNames = new String[pTypes.length];
int j = Modifier.isStatic(member.getModifiers()) ? 0 : 1;
boolean found = false; // did we find any non-null names
for (int i = 0; i < paramNames.length; i++) {
if (info.names[j] != null) {
found = true;
paramNames[i] = info.names[j];
}
j++;
if (pTypes[i] == double.class || pTypes[i] == long.class) {
// skip a slot for 64bit params
j++;
}
}
if (found) {
return paramNames;
} else {
return null;
}
} else {
return null;
}
}
private static class MethodInfo {
String[] names;
public MethodInfo(int maxLocals) {
names = new String[maxLocals];
}
}
private MethodInfo getMethodInfo() {
MethodInfo info = null;
if (methods != null && methodName != null) {
info = methods.get(methodName);
}
return info;
}
/**
* this is invoked when a LocalVariableTable attribute is encountered.
*
* @throws IOException
*/
public void readLocalVariableTable() throws IOException {
int len = readShort(); // table length
MethodInfo info = getMethodInfo();
for (int j = 0; j < len; j++) {
readShort(); // start pc
readShort(); // length
int nameIndex = readShort(); // name_index
readShort(); // descriptor_index
int index = readShort(); // local index
if (info != null) {
info.names[index] = resolveUtf8(nameIndex);
}
}
}
}