spring框架学习（二）使用注解代替xml配置

注解

1.使用注解配置spring

1)开启使用注解代理配置文件

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://www.springframework.org/schema/beans" xmlns:context="http://www.springframework.org/schema/context" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-4.2.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.2.xsd ">

<!-- 指定扫描cn.mf.bean报下的所有类中的注解. 注意:扫描包时.会扫描指定报下的所有子孙包-->
<context:component-scan base-package="cn.mf.bean"></context:component-scan>
</beans>

2.在类中使用注解完成配置

1)将对象注册到容器

//@Component("user")相当于//<bean name="user" class="cn.itcast.bean.User"  />
//@Service("user") // service层
//@Controller("user") // web层
@Repository("user")// dao层

2)修改对象的作用范围

//指定对象的作用范围
@Scope(scopeName="singleton")

3)值类型注入

通过反射的Field赋值,破坏了封装性

    @Value("18")
    private Integer age;

通过set方法赋值,推荐使用.

    @Value("tom")    
    public void setName(String name) {
        this.name = name;
    }

4)引用类型注入

@Autowired //自动装配
private Car car;

@Autowired //自动装配
@Qualifier("car2")//使用@Qualifier注解告诉spring容器自动装配哪个名称的对象
private Car car;

@Resource(name="car")//手动注入,指定注入哪个名称的对象
    private Car car;

5)初始化|销毁方法

@PostConstruct //在对象被创建后调用.init-method
    public void init(){
        System.out.println("我是初始化方法!");
    }
    @PreDestroy //在销毁之前调用.destory-method
    public void destory(){
        System.out.println("我是销毁方法!");
    }

实战总结

applicationContext.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://www.springframework.org/schema/beans" xmlns:context="http://www.springframework.org/schema/context" xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-4.2.xsd http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-4.2.xsd ">

<!-- 指定扫描cn.mf.bean报下的所有类中的注解. 注意:扫描包时.会扫描指定报下的所有子孙包-->
<context:component-scan base-package="cn.mf.bean"></context:component-scan>
<bean name="car2" class="cn.mf.bean.Car"  >
    <property name="name" value="布加迪威龙" ></property>
    <property name="color" value="black"  ></property>
</bean>
</beans>

User.java

package cn.mf.bean;

import javax.annotation.PostConstruct;
import javax.annotation.PreDestroy;
import javax.annotation.Resource;
import org.springframework.beans.factory.annotation.Value;
import org.springframework.context.annotation.Scope;
import org.springframework.stereotype.Repository;


//<bean name="user" class="cn.itcast.bean.User"  />
//@Component("user")
//@Service("user") // service层
//@Controller("user") // web层
@Repository("user")// dao层
//指定对象的作用范围
@Scope(scopeName="singleton")
public class User {
    private String name;
    @Value("18")
    private Integer age;
    
    //@Autowired //自动装配
    //问题:如果匹配多个类型一致的对象.将无法选择具体注入哪一个对象.
    //@Qualifier("car2")//使用@Qualifier注解告诉spring容器自动装配哪个名称的对象
    
    @Resource(name="car")//手动注入,指定注入哪个名称的对象
    private Car car;
    
    public Car getCar() {
        return car;
    }
    public void setCar(Car car) {
        this.car = car;
    }
    public String getName() {
        return name;
    }
    @Value("tom")    
    public void setName(String name) {
        this.name = name;
    }
    public Integer getAge() {
        return age;
    }
    public void setAge(Integer age) {
        this.age = age;
    }
    @PostConstruct //在对象被创建后调用.init-method
    public void init(){
        System.out.println("我是初始化方法!");
    }
    @PreDestroy //在销毁之前调用.destory-method
    public void destory(){
        System.out.println("我是销毁方法!");
    }
    @Override
    public String toString() {
        return "User [name=" + name + ", age=" + age + ", car=" + car + "]";
    }
    
}

Car.java

package cn.mf.bean;

import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Component;

@Component("car")
public class Car {
    @Value("玛莎拉蒂")
    private String  name;
    @Value("呕吐绿")
    private String color;
    
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public String getColor() {
        return color;
    }
    public void setColor(String color) {
        this.color = color;
    }
    @Override
    public String toString() {
        return "Car [name=" + name + ", color=" + color + "]";
    }
    
    
}

Junit

@Test
    public void fun1(){        
        //1 创建容器对象
        ClassPathXmlApplicationContext ac = new ClassPathXmlApplicationContext("applicationContext.xml");
        //2 向容器"要"user对象
        User u1 = (User) ac.getBean("user");
        User u2 = (User) ac.getBean("user");
        System.out.println(u1==u2);
        //3 打印user对象
        System.out.println(u1);
        ac.close();
    }