org.apache.bytecode.ChainedParamReader Maven / Gradle / Ivy
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* 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
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* 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.bytecode;
import java.io.IOException;
import java.lang.reflect.Constructor;
import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
/**
* Description: In ParamReader class, user cannot get inherited method parameter
* from the class they passed in for performance reasons This class
* is walks up the inheritance chain. If the method is not found in
* the derived class, search in super class. If not found in the immedidate super
* class, search super class's super class, until the root, which is java.lang.Object,
* is reached. This is not an eager load since it only start searching the super class
* when it is asked to.
*/
public class ChainedParamReader {
private List chain = new ArrayList();
private List clsChain = new ArrayList();
private Map methodToParamMap = new HashMap();
/**
* Processes a given class's parameter names.
*
* @param cls the class which user wants to get parameter info from
* @throws IOException
*/
public ChainedParamReader(Class cls) throws IOException {
ParamReader reader = new ParamReader(cls);
chain.add(reader);
clsChain.add(cls);
}
//now I need to create deligate methods
/**
* Returns 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 Returns array of names, one per parameter, or null
*/
public String[] getParameterNames(Constructor ctor) {
//there is no need for the constructor chaining.
return ((ParamReader) chain.get(0)).getParameterNames(ctor);
}
/**
* Returns the names of the declared parameters for the given method.
* If cannot determine the names in the current class, search its parent
* class until we reach java.lang.Object. If still can not find the method,
* returns null. The returned array has 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[] Returns array of names, one per parameter, or null
*/
public String[] getParameterNames(Method method) {
//go find the one from the cache first
if (methodToParamMap.containsKey(method)) {
return (String[]) methodToParamMap.get(method);
}
String[] ret = null;
for (Iterator it = chain.iterator(); it.hasNext();) {
ParamReader reader = (ParamReader) it.next();
ret = reader.getParameterNames(method);
if (ret != null) {
methodToParamMap.put(method, ret);
return ret;
}
}
//if we here, it means we need to create new chain.
Class cls = (Class) clsChain.get(chain.size() - 1);
while (cls != null && cls != java.lang.Object.class && cls.getSuperclass() != null) {
Class superClass = cls.getSuperclass();
try {
ParamReader _reader = new ParamReader(superClass);
chain.add(_reader);
clsChain.add(cls);
ret = _reader.getParameterNames(method);
if (ret != null) { //we found it so just return it.
methodToParamMap.put(method, ret);
return ret;
}
} catch (IOException e) {
//can not find the super class in the class path, abort here
return null;
}
cls = superClass;
}
methodToParamMap.put(method, ret);
return null;
}
}