javassist:增强型的java反射工具,获取方法参数名

java的反射是不能获取方法的参数名的。比如：

public String concatString(String  param1,String  param2){
         return param1+param2;
    }

 

想获取"param1",和"param2"这个参数名，貌似是不行的。借助第三方包javaassist就可以获得。

 

整合原作者代码：

 

 

 import javassist.ClassPool;
 import javassist.CtClass;
 import javassist.CtMethod;
 import javassist.Modifier;
 import javassist.NotFoundException;
 import javassist.bytecode.CodeAttribute;
 import javassist.bytecode.LocalVariableAttribute;
 import javassist.bytecode.MethodInfo;

 public class Test {
     public static void main(String[] args) {

         testReflectParamName();

     }

     /**
      * 反射获取方法参数名称
      */
     public static void testReflectParamName() {
         Class clazz = MyClass.class;
         try {
             ClassPool pool = ClassPool.getDefault();
             CtClass cc = pool.get(clazz.getName());
             CtMethod cm = cc.getDeclaredMethod("concatString");

             // 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) {
                 // exception
             }
             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);
             // paramNames即参数名
             for (int i = 0; i < paramNames.length; i++) {
                 System.out.println("参数名" + i + ":" + paramNames[i]);
             }

         } catch (NotFoundException e) {
             e.printStackTrace();
         }
     }
 }

 class MyClass {
     public String concatString(String param1, String param2) {
         return param1 + param2;
     }
 }

 

 

反射获取参数注解：

 

 

 import java.lang.annotation.Annotation;
 import java.lang.annotation.ElementType;
 import java.lang.annotation.Retention;
 import java.lang.annotation.RetentionPolicy;
 import java.lang.annotation.Target;
 import java.lang.reflect.Method;
 import java.util.Date;

 import javassist.ClassPool;
 import javassist.CtClass;
 import javassist.CtMethod;
 import javassist.Modifier;
 import javassist.NotFoundException;
 import javassist.bytecode.CodeAttribute;
 import javassist.bytecode.LocalVariableAttribute;
 import javassist.bytecode.MethodInfo;

 public class Test {
     public static void main(String[] args) {

         testReflectParamName();
         // 反射获取方法参数注解
         testReflectMethodParamAnno();
     }

     /**
      * 反射获取方法参数名称
      */
     public static void testReflectParamName() {
         Class clazz = MyClass.class;
         try {
             ClassPool pool = ClassPool.getDefault();
             CtClass cc = pool.get(clazz.getName());
             CtMethod cm = cc.getDeclaredMethod("concatString");

             // 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) {
                 // exception
             }
             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);
             // paramNames即参数名
             for (int i = 0; i < paramNames.length; i++) {
                 System.out.println("参数名" + i + ":" + paramNames[i]);
             }

         } catch (NotFoundException e) {
             e.printStackTrace();
         }
     }

     /**
      * 反射获取方法参数注解
      */
     public static void testReflectMethodParamAnno() {
         Class clazz = MyClass.class;
         try {
             // 使用jdk原生的反射方法
             Method m = clazz.getDeclaredMethod("datefomat",
                     new Class[] { Date.class });
             Annotation[][] annotations = m.getParameterAnnotations();
             System.out.println("jdk获取方法参数anno:"+annotations[0][0]);
         } catch (SecurityException e) {
             e.printStackTrace();
         } catch (NoSuchMethodException e) {
             e.printStackTrace();
         }

         try {
             ClassPool pool = ClassPool.getDefault();
             CtClass cc = pool.get(clazz.getName());
             CtMethod cm = cc.getDeclaredMethod("datefomat");

             // 使用javassist的反射方法可以获得参数标注值
             Object[][] annotations = cm.getParameterAnnotations();
             DateFormat myAnno = (DateFormat) annotations[0][0];
             System.out.println("参数注解："+myAnno.value());

         } catch (NotFoundException e) {
             e.printStackTrace();
         } catch (ClassNotFoundException e) {
             e.printStackTrace();
         }
     }
 }

 class MyClass {
     public String concatString(String param1, String param2) {
         return param1 + param2;
     }

     public String datefomat(@DateFormat("yyyy-MM-dd HH")
     Date date1) {
         return date1.toString();
     }
 }

 // 注解类
 @Target(ElementType.PARAMETER)
 @Retention(RetentionPolicy.RUNTIME)
 @interface DateFormat {
     String value() default "yyyy-MM-dd";
 }