java:axis2环境下获取方法参数名的另一种方法
2015-09-24 16:48
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java本身提供的方法不能获取方法的参数名的,只能获取每个参数的类型
比如:
想获取”param1”,和”param2”这个参数名,肯定是不行的。关于获取方法的参数名字(不是参数类型),一般的做法是借助第三方包javassist或asm来实现。参见下面的文章:
java反射:使用asm 获取方法的参数名
javassist:增强型的java反照工具,获取方法参数名
不过如果你的项目是基于axis2环境的,其实还有第三种方法:
我做基于axis2的项目时,需要获取方法的参数名字,当时也找到了上述的两种办法,都可以实现,没啥问题,但是系统要多一个jar包,感觉不爽。想到axis2在生成wsdl文件时需要获取方法的名字,所以我认为axis2的jar包中肯定有办法获取方法的参数名。于是研究了axis2 关于生成wsdl文件的相关代码,总算找到了,用法也很简单。
在axsi2生成wsdl文件时,使用了一个叫org.apache.axis2.description.java2wsdl.bytecode.MethodTable(axis2-kernel-1.6.2.jar)的类来获取方法的参数名,代码如下:
看上面的代码,这个类其实很简单,实际实现获取参数名的工作都是在org.apache.axis2.description.java2wsdl.bytecode.ChainedParamReader下完成的
仔细看代码,ChainedParamReader也只是一层级联封装,实现对父类的方法搜索,真正实现对每个class文件字节读取解析是在 org.apache.axis2.description.java2wsdl.bytecode.ParamReader(axis2-kernel-1.6.2.jar)里完成的,如果你想继续深入可以看axis2的源代码。
对于我来说,我只要关心org.apache.axis2.description.java2wsdl.bytecode.ChainedParamReader这个类就够了。
于是我根据自己的需要,基于ChainedParamReader写了这个下面这个类,来实现获取一般方法和构造方法的参数名。
注意:
不论是使用asm,javassist,还是我上述的办法,都只能获取实体类中方法的参数名,对于抽象类或接口,是没有办法的。
比如:
public String concatString(String param1,String param2){ return param1+param2; }
想获取”param1”,和”param2”这个参数名,肯定是不行的。关于获取方法的参数名字(不是参数类型),一般的做法是借助第三方包javassist或asm来实现。参见下面的文章:
java反射:使用asm 获取方法的参数名
javassist:增强型的java反照工具,获取方法参数名
不过如果你的项目是基于axis2环境的,其实还有第三种方法:
我做基于axis2的项目时,需要获取方法的参数名字,当时也找到了上述的两种办法,都可以实现,没啥问题,但是系统要多一个jar包,感觉不爽。想到axis2在生成wsdl文件时需要获取方法的名字,所以我认为axis2的jar包中肯定有办法获取方法的参数名。于是研究了axis2 关于生成wsdl文件的相关代码,总算找到了,用法也很简单。
在axsi2生成wsdl文件时,使用了一个叫org.apache.axis2.description.java2wsdl.bytecode.MethodTable(axis2-kernel-1.6.2.jar)的类来获取方法的参数名,代码如下:
/* * 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.axis2.description.java2wsdl.bytecode; import java.lang.reflect.Method; import java.util.HashMap; public class MethodTable { private HashMap nameToMethodMap; //关键的实现都在这个类中 private ChainedParamReader cpr; public MethodTable(Class cls) throws Exception { cpr = new ChainedParamReader(cls); nameToMethodMap = new HashMap(); loadMethods(cls); } /** * To load all the methods in the given class by Java reflection * * @param cls * @throws Exception */ private void loadMethods(Class cls) throws Exception { Method [] methods = cls.getMethods(); for (int i = 0; i < methods.length; i++) { Method method = methods[i]; if (method.isBridge()) { continue; } nameToMethodMap.put(method.getName(), method); } } public String [] getParameterNames(String methodName) { Method method = (Method) nameToMethodMap.get(methodName); if (method == null) { return null; } return cpr.getParameterNames(method); } }
看上面的代码,这个类其实很简单,实际实现获取参数名的工作都是在org.apache.axis2.description.java2wsdl.bytecode.ChainedParamReader下完成的
/* * 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.axis2.description.java2wsdl.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 { //具体解析每个class文件是由这个ParamReader实现的 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; //在当前类中寻找指定的方法,找到就返回 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); //如果在当前类中找不到指定的方法,就到父类中寻找,找不到就返回null 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; } }
仔细看代码,ChainedParamReader也只是一层级联封装,实现对父类的方法搜索,真正实现对每个class文件字节读取解析是在 org.apache.axis2.description.java2wsdl.bytecode.ParamReader(axis2-kernel-1.6.2.jar)里完成的,如果你想继续深入可以看axis2的源代码。
对于我来说,我只要关心org.apache.axis2.description.java2wsdl.bytecode.ChainedParamReader这个类就够了。
于是我根据自己的需要,基于ChainedParamReader写了这个下面这个类,来实现获取一般方法和构造方法的参数名。
import java.io.IOException; import java.lang.reflect.Constructor; import java.lang.reflect.Member; import java.lang.reflect.Method; import java.util.HashMap; import java.util.Map; import org.apache.axis2.description.java2wsdl.bytecode.ChainedParamReader; /** * 获取构造函数或方法的参数名 * @author guyadong * */ public class ParameterNames { private final Map<Class<?>, ChainedParamReader> readers = new HashMap<Class<?>, ChainedParamReader>(); private final Class<?> clazz; /** * @param clazz 要构造函数或方法的参数名的类 */ public ParameterNames(Class<?> clazz) { this.clazz = clazz; try { Class<?> c = clazz; do { readers.put(c, new ChainedParamReader(c)); } while (null != (c = c.getSuperclass())); } catch (IOException e) { throw new RuntimeException(e); } } /** * 获取构造函数或方法的参数名 * @param reader * @param member 构造函数或方法对象 * @return */ private final String[] getParameterNames(ChainedParamReader reader, Member member) { if (member instanceof Method) return reader.getParameterNames((Method) member); else if (member instanceof Constructor) return reader.getParameterNames((Constructor<?>) member); else throw new IllegalArgumentException("member type must be Method or Constructor"); } /** * 获取构造函数或方法的参数名 * @param member 构造函数或方法对象 * @return * @see #getParameterNames(ChainedParamReader, Member) */ public final String[] getParameterNames(Member member) { Assert.notNull(member, "member"); Class<?> declaringClass = member.getDeclaringClass(); ChainedParamReader reader; if (null == (reader = readers.get(declaringClass))) { throw new IllegalArgumentException(String.format("%s is not member of %s", member.toString(), declaringClass.getName())); } return getParameterNames(reader, member); } /** * 获取构造函数或方法的参数名<br> * {@code name}为{@code null}时,获取构造函数的参数名 * @param name 方法名 * @param parameterTypes 构造函数或方法的参数类型 * @return * @throws NoSuchMethodException * @see {@link #getParameterNames(String, Class)} */ public final String[] getParameterNames(String name, Class<?>[] parameterTypes) throws NoSuchMethodException { try { Member member = null == name ? clazz.getConstructor(parameterTypes) : clazz.getMethod(name, parameterTypes); return getParameterNames(member); } catch (SecurityException e) { throw new IllegalArgumentException(e); } } }
注意:
不论是使用asm,javassist,还是我上述的办法,都只能获取实体类中方法的参数名,对于抽象类或接口,是没有办法的。
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