How to get method parameter names?

朱雀 2022-07-13 10:23 222阅读 0赞

# 如何获取方法参数命名？ #

## 1.通过javassist获取 ##

/** * Get Method Parameter Names in JAVA * 参考：http://blog.hailinzeng.com/2014/10/10/get-method-parameter-name-in-java/ * * @param clazz * @param method * @return 参数名称数组 */
        public static String[] getMethodParamNames(Class<?> clazz, Method method) throws NotFoundException {
            ClassPool pool = ClassPool.getDefault();
            pool.insertClassPath(new ClassClassPath(clazz));
            CtClass cc = pool.get(clazz.getName());
            Class<?>[] paramTypes = method.getParameterTypes();
            String[] paramTypeNames = new String[method.getParameterTypes().length];
            for (int i = 0; i < paramTypes.length; i++)
                paramTypeNames[i] = paramTypes[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 RuntimeException("class:" + clazz.getName()
                        + ", have no LocalVariableTable, please use javac -g:{vars} to compile the source file");
            }
    
            String[] paramNames = new String[cm.getParameterTypes().length];
            TreeMap<Integer, Integer> map = new TreeMap<>();
            for (int i = 0; i < attr.tableLength(); i++) {
                map.put(attr.index(i), i);
            }
            int index = 0;
            boolean isStaticMethod = Modifier.isStatic(cm.getModifiers());
            boolean flag = false;
            for (Integer key : map.keySet()) {
                //如果是非静态方法，第0个attr.variableName(0)返回this,所以要跳过
                if (!isStaticMethod && !flag) {
                    flag = true;
                    continue;
                }
    
                if (index < paramNames.length) {
                    paramNames[index++] = attr.variableName(map.get(key));
                } else {
                    break;
                }
            }
            return paramNames;
        }

参考:  
[Get Method Parameter Names in JAVA][]  
[How to get method parameter names with javassist?][How to get method parameter names with javassist]  
[Javassist初体验][Javassist]

## 2.java8 可直接使用java.lang.reflect.Parameter\#getName()获取参数命名 ##

前提是使用javac compiler，并在编译时带上-parameters option。具体参考  
[Obtaining Names of Method Parameters][]

--------------------

[Get Method Parameter Names in JAVA]: http://blog.hailinzeng.com/2014/10/10/get-method-parameter-name-in-java/
[How to get method parameter names with javassist]: https://github.com/jboss-javassist/javassist/issues/14
[Javassist]: http://www.cnblogs.com/asfeixue/p/4278471.html
[Obtaining Names of Method Parameters]: https://docs.oracle.com/javase/tutorial/reflect/member/methodparameterreflection.html