1 package com.swust.javassist;
  2 
  3 import java.lang.reflect.Field;
  4 import java.lang.reflect.Method;
  5 import java.util.Arrays;
  6 
  7 import javassist.ClassPool;
  8 import javassist.CtClass;
  9 import javassist.CtConstructor;
 10 import javassist.CtField;
 11 import javassist.CtMethod;
 
 12 import javassist.CtNewMethod;
 13 import javassist.Modifier;
 14 
 15 public class Example2 {
 16         //獲取類的簡單資訊  
 17         public static void test01() throws Exception{ 
 18             ClassPool pool = ClassPool.getDefault();  
 19             CtClass cc = pool.get("com.swust.beans.Person"
 
);  
 20             //得到位元組碼  
 21             byte[] bytes = cc.toBytecode();  
 22             System.out.println(Arrays.toString(bytes));  
 23             System.out.println(cc.getName());//獲取類名  
 24             System.out.println(cc.getSimpleName());//獲取簡要類名  
 25             System.out.println(cc.getSuperclass());//
 
獲取父類  
 26             System.out.println(cc.getInterfaces());//獲取介面  
 27             System.out.println(cc.getMethods());//獲取  
 28         }  
 29         //新生成一個方法  
 30         public static void test02() throws Exception{  
 31             ClassPool pool = ClassPool.getDefault();  
 32             CtClass cc = pool.get("com.swust.beans.Person");  
 33             //第一種  
 34             //CtMethod cm = CtMethod.make("public String getName(){return name;}", cc);  
 35             //第二種  
 36             //引數：返回值型別，方法名，引數，物件  
 37             CtMethod cm = new CtMethod(CtClass.intType,"add",new CtClass[]{CtClass.intType,CtClass.intType},cc);  
 38             cm.setModifiers(Modifier.PUBLIC);//訪問範圍  
 39             cm.setBody("{return $1+$2;}");  
 40             //cc.removeMethod(m) 刪除一個方法  
 41             cc.addMethod(cm);  
 42             //通過反射呼叫方法  
 43             Class clazz = cc.toClass();  
 44             Object obj = clazz.newInstance();//通過呼叫無參構造器，生成新的物件  
 45             Method m = clazz.getDeclaredMethod("add", int.class,int.class);  
 46             Object result = m.invoke(obj, 2,3);  
 47             System.out.println(result);  
 48         }  
 49           
 50         //修改已有的方法  
 51         public static void test03() throws Exception{  
 52             ClassPool pool  = ClassPool.getDefault();  
 53             CtClass cc = pool.get("bean.User");  
 54               
 55             CtMethod cm = cc.getDeclaredMethod("hello",new CtClass[]{pool.get("java.lang.String")});  
 56             cm.insertBefore("System.out.println(\"呼叫前\");");//呼叫前  
 57             cm.insertAt(29, "System.out.println(\"29\");");//行號  
 58             cm.insertAfter("System.out.println(\"呼叫後\");");//呼叫後  
 59               
 60             //通過反射呼叫方法  
 61             Class clazz = cc.toClass();  
 62             Object obj = clazz.newInstance();  
 63             Method m = clazz.getDeclaredMethod("hello", String.class);  
 64             Object result = m.invoke(obj, "張三");  
 65             System.out.println(result);       
 66         }  
 67           
 68         //修改已有屬性  
 69         public static void test04() throws Exception{  
 70             ClassPool pool  = ClassPool.getDefault();  
 71             CtClass cc = pool.get("bean.User");  
 72               
 73             //屬性  
 74             CtField cf = new CtField(CtClass.intType,"age",cc);  
 75             cf.setModifiers(Modifier.PRIVATE);  
 76             cc.addField(cf);  
 77             //增加響應的get set方法  
 78             cc.addMethod(CtNewMethod.getter("getAge",cf));  
 79             cc.addMethod(CtNewMethod.setter("setAge",cf));  
 80               
 81             //訪問屬性  
 82             Class clazz = cc.toClass();  
 83             Object obj = clazz.newInstance();         
 84             Field field = clazz.getDeclaredField("age");  
 85             System.out.println(field);  
 86             Method m = clazz.getDeclaredMethod("setAge", int.class);  
 87             m.invoke(obj, 16);  
 88             Method m2 = clazz.getDeclaredMethod("getAge", null);  
 89             Object resutl = m2.invoke(obj,null);          
 90             System.out.println(resutl);  
 91         }  
 92           
 93         //操作構造方法  
 94         public static void test05() throws Exception{  
 95             ClassPool pool = ClassPool.getDefault();  
 96             CtClass cc = pool.get("com.swust.beans.Person");  
 97               
 98             CtConstructor[] cons = cc.getConstructors();  
 99             for(CtConstructor con:cons){  
100                 System.out.println(con);  
101             }  
102         }  
103         public static void main(String[] args) throws Exception {  
104             test01();  
105             //test02();  
106             //test03();  
107             //test04();  
108             test05();  
109     }
110 }