关于类和接口的对象创建问题

public interface targetInterface {
    public void save();
}

package com.jiang;

public class target implements targetInterface {
    @Override
    public void save() {
        System.out.println("target");
    }
}

import com.jiang.target;
import com.jiang.targetInterface;
import org.junit.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class test {
    @Test
public void test(){
    ApplicationContext app = new ClassPathXmlApplicationContext("applicationContext.xml");
        targetInterface target = (targetInterface) app.getBean("target");
        target.save();
    }
}

import com.jiang.target;
import com.jiang.targetInterface;
import org.junit.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class test {
    @Test
public void test(){
    ApplicationContext app = new ClassPathXmlApplicationContext("applicationContext.xml");
        targetInterface target = (targetInterface) app.getBean("target");
        target.save();
    }
}

以aop单元测试为例,在测绘类中,创建对象要以接口作为类型

 

如果不以接口为对象类型就会出现bag