创建一个接口:
package cn.itcast.mapper;
public interface StudentMapper {
public void add();
public void del();
public void update();
public void query();
}
书写实现类
package cn.itcast.mapper.impl;
import cn.itcast.mapper.StudentMapper;
public class StudentMapperImpl implements StudentMapper {
public void add() {
System.out.println("增加了一个用户");
}
public void del() {
System.out.println("删除了一个用户");
}
public void update() {
System.out.println("更新了一个用户");
}
public void query() {
System.out.println("查询了一个用户");
}
}
要求在不改变接口和实现类的前提下,完成添加打印日志功能
public class StudentMapperImpl1 implements StudentMapper {
private StudentMapper studentMapper;
//给studentMapper赋值,不然会爆空指针异常
public void setStudentMapper(StudentMapper studentMapper) {
this.studentMapper = studentMapper;
}
public void add() {
log("add");
studentMapper.add();
}
public void del() {
log("del");
studentMapper.del();
}
public void update() {
log("update");
studentMapper.update();
}
public void query() {
log("query");
studentMapper.query();
}
//添加的日志方法
public void log(String msg){
System.out.println("执行了"+msg+"方法");
}
}
测试:
public class Test01 {
@Test
public void show() {
//获取原始对象实例对象
StudentMapperImpl studentMapper = new StudentMapperImpl();
//获取增强对象实例对象
StudentMapperImpl1 studentMapper1 = new StudentMapperImpl1();
//将原始对象赋值给需要增强的对象
studentMapper1.setStudentMapper(studentMapper);
//方法调用
studentMapper1.add();
studentMapper1.del();
studentMapper1.update();
studentMapper1.query();
}
}
结果:
com.intellij.rt.execution.junit.JUnitStarter -ideVersion5 -junit4 Test01,show
执行了add方法
增加了一个用户
执行了del方法
删除了一个用户
执行了update方法
更新了一个用户
执行了query方法
查询了一个用户
Process finished with exit code 0