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();
    }
}