javassist

￡神魔★判官ぃ 2022-05-27 11:57 221阅读 0赞

/\*\*  
  \* 产生新的方法  
  \* @throws Exception  
  \*/  
 public static void test01() throws Exception \{  
  ClassPool pool = ClassPool.getDefault();  
  CtClass cc = pool.get("包名 . 类名");  
//两种方式产生新的方法   
//  CtMethod m1 =  CtMethod.make("public int getEmpNo()\{return empNo;\}", cc);  
    
  CtMethod m2 = new CtMethod(CtClass.intType, "add",  
                        new CtClass\[\] \{CtClass.intType,CtClass.intType\} , cc);  
     m2. setModifiers(Modifier.PUBLIC);  
     m2. setBody("return $1 + $2;");  
    
    
//      cc.addMethod(m1);      
        cc. addMethod(m2);      
    
     //通过反射调用新生成的方法  
        Class c = cc.toClass();  
        Object obj = c.newInstance();  //调用无参构造来创建对象  
        Method method = c.getDeclaredMethod("add", int.class,int.class);  
        Object result = method.invoke(obj, 100,300);  
        System.out.println(result);                
 \}

/\*\*  
  \* 新的属性并生成get 和 set  
  \* @throws Exception  
  \*/

public  static void test04() throws Exception \{  
  ClassPool pool = ClassPool.getDefault();  
  CtClass cc = pool.get("JavassistTest.TestClass\_Emp");

//两种方式产生新的属性  
//  CtField f1 = CtField. make("private int age", cc);  
  CtField f2 = new CtField(CtClass.intType,"age",cc);  
  f2. setModifiers(Modifier.PRIVATE);  
     cc. addField(f2);  
      
        cc.getDeclaredField("age");//获得这个属性

//增加相应的get set方法  
         cc.addMethod(CtNewMethod.getter("getAge", f2));  
        cc.addMethod(CtNewMethod.getter("setAge", f2));

/\*\*  
  \*  修改已有的方法  
  \* @throws Exception  
  \*/  
 public static void test03() throws Exception\{  
  ClassPool pool = ClassPool.getDefault();  
  CtClass cc = pool.get("JavassistTest.TestClass\_Emp");  
    
  CtMethod m1 = cc.getDeclaredMethod("sayHello",new CtClass \[\] \{CtClass.intType\});  
     m1. insertBefore("System.out.println($1);System.out.println(\\"start!!!\\");");  
   
     Class c = cc.toClass();  
        Object obj = c.newInstance();  //调用无参构造来创建对象  
        Method method = c.getDeclaredMethod("sayHello", int.class);  
        Object result = method.invoke(obj,300);  
        System.out.println(result);      
 \}