Javassist之常用API的应用 02

测试模型代码：

 package org.study2.JavaSenior.annotation.javassistDemo;

 /**
  * @Auther:GongXingRui
  * @Date:2018/10/30
  * @Description:
  **/

 @Author(name = "gxr", year = 2018)
 public class Emp {

     private int empno;
     private String ename;

     public void sayHello(int a) {
         System.out.println("sayHello," + a);
     }

     public int getEmpno() {
         return empno;
     }

     public void setEmpno(int empno) {
         this.empno = empno;
     }

     public String getEname() {
         return ename;
     }

     public void setEname(String ename) {
         this.ename = ename;
     }

     public Emp(int empno, String ename) {
         super();
         this.empno = empno;
         this.ename = ename;
     }

     public Emp() {
     }
 }

API应用代码：

 package org.study2.JavaSenior.annotation.javassistDemo;

 import javassist.*;

 import java.lang.reflect.Method;
 import java.util.Arrays;

 /**
  * @Auther:GongXingRui
  * @Date:2018/10/30
  * @Description: Javassist 常用API的应用
  **/
 public class JavassistDemo2 {
     /**
      * 处理类的基本用法
      *
      * @throws Exception
      */
     public static void test01() throws Exception {
         ClassPool pool = ClassPool.getDefault();
         CtClass cc = pool.get("org.study2.JavaSenior.annotation.javassistDemo.Emp");

         byte[] bytes = cc.toBytecode();
         System.out.println(Arrays.toString(bytes));

         System.out.println(cc.getName()); //获取类名
         System.out.println(cc.getSimpleName()); //获取简要类名
         System.out.println(cc.getSuperclass()); //获得父类
         System.out.println(cc.getInterfaces()); //获得接口

     }

     /**
      * 测试产生新的方法
      *
      * @throws Exception
      */
     public static void test02() throws Exception {
         ClassPool pool = ClassPool.getDefault();
         CtClass cc = pool.get("org.study2.JavaSenior.annotation.javassistDemo.Emp");

         // CtMethod m = CtNewMethod.make("public int add(int a,int b){return a+b;}", cc);

         CtMethod m = new CtMethod(CtClass.intType, "add",
                 new CtClass[]{CtClass.intType, CtClass.intType}, cc);
         m.setModifiers(Modifier.PUBLIC);
         m.setBody("{System.out.println(\"www.sxt.cn\");return $1+$2;}");

         cc.addMethod(m);

         //通过反射调用新生成的方法
         Class clazz = cc.toClass();
         Object obj = clazz.newInstance();  //通过调用Emp无参构造器，创建新的Emp对象
         Method method = clazz.getDeclaredMethod("add", int.class, int.class);
         Object result = method.invoke(obj, 200, 300);
         System.out.println(result);
     }

     /**
      * 修改已有的方法的信息，修改方法体的内容
      *
      * @throws Exception
      */
     public static void test03() throws Exception {
         ClassPool pool = ClassPool.getDefault();
         CtClass cc = pool.get("org.study2.JavaSenior.annotation.javassistDemo.Emp");

         CtMethod cm = cc.getDeclaredMethod("sayHello", new CtClass[]{CtClass.intType});
         cm.insertBefore("System.out.println($1);System.out.println(\"start!!!\");");
         cm.insertAt(9, "int b=3;System.out.println(\"b=\"+b);");
         cm.insertAfter("System.out.println(\"end!!!\");");

         //通过反射调用新生成的方法
         Class clazz = cc.toClass();
         Object obj = clazz.newInstance();  //通过调用Emp无参构造器，创建新的Emp对象
         Method method = clazz.getDeclaredMethod("sayHello", int.class);
         method.invoke(obj, 300);
     }

     /**
      * 属性的操作
      *
      * @throws Exception
      */
     public static void test04() throws Exception {
         ClassPool pool = ClassPool.getDefault();
         CtClass cc = pool.get("org.study2.JavaSenior.annotation.javassistDemo.Emp");

         //  CtField f1 = CtField.make("private int empno;", cc);
         CtField f1 = new CtField(CtClass.intType, "salary", cc);
         f1.setModifiers(Modifier.PRIVATE);
         cc.addField(f1);

         //  cc.getDeclaredField("ename");   //获取指定的属性

         //增加相应的set和get方法
         cc.addMethod(CtNewMethod.getter("getSalary", f1));
         cc.addMethod(CtNewMethod.setter("setSalary", f1));

         Class clazz = cc.toClass();
         Object obj = clazz.newInstance();
         Method method = clazz.getDeclaredMethod("setSalary", int.class);
         method.invoke(obj, 2000);
         Method method2 = clazz.getDeclaredMethod("getSalary", null);
         int n = (int) method2.invoke(obj, null);
         System.out.println("Salary=" + n);

     }

     /**
      * 构造方法的操作
      *
      * @throws Exception
      */
     public static void test05() throws Exception {
         ClassPool pool = ClassPool.getDefault();
         CtClass cc = pool.get("org.study2.JavaSenior.annotation.javassistDemo.Emp");

         CtConstructor[] cs = cc.getConstructors();
         for (CtConstructor c : cs) {
             System.out.println(c.getLongName());
         }
     }

     public static void test06() throws Exception {
         CtClass cc = ClassPool.getDefault().get("org.study2.JavaSenior.annotation.javassistDemo.Emp");
         Object[] all = cc.getAnnotations();
         Author a = (Author) all[0];
         String name = a.name();
         int year = a.year();
         System.out.println("name: " + name + ", year: " + year);

     }

     public static void main(String[] args) throws Exception {
         test06();
     }
 }