Spring框架context的注解管理方法之二 使用注解注入基本类型和对象属性 注解annotation和配置文件混合使用(半注解)

时间：2023-12-27 13:34:19

首先还是xml的配置文件

<?xml version="1.0" encoding="UTF-8"?>

<beans xmlns="http://www.springframework.org/schema/beans"

    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

    xmlns:context="http://www.springframework.org/schema/context" xsi:schemaLocation="

        http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd

        http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context.xsd">

      <!--  开启注解扫描  -->

     <context:component-scan base-package="com.swift"></context:component-scan>

</beans>

接着是假定dao的类

package com.swift;

import org.springframework.stereotype.Component;

@Component(value="dao")

public class Dao {

    public String fun() {

        return "This is Dao's fun()........";

    }

}

生成一个对象很方便，甚至@Component(value="dao")中的value=都可以不写，变成

@Component("dao")

然后是假定service的类

package com.swift;

import org.springframework.beans.factory.annotation.Autowired;

import org.springframework.stereotype.Component;

@Component(value="service")

public class Service {

    @Autowired

    private Dao dao;

    public String fun() {

        return "This is Service's fun()......."+"\r\n"+this.dao.fun();

    }

    //注意使用注解方法，不需要自己生成setter方法了

    public void setDao(Dao dao) {

        this.dao = dao;

    }

}

与配置文件中使用<bean id="service" class="com.swift.Service"><property name="dao" ref="dao"></property></bean>

不同，注解生成两个对象后，再注解属性

@Autowired

就搞定了，自动装配，自动连线

最后使用Servlet来测试一下

package com.swift;

import java.io.IOException;

import javax.servlet.ServletException;

import javax.servlet.annotation.WebServlet;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import org.springframework.context.ApplicationContext;

import org.springframework.context.support.ClassPathXmlApplicationContext;

@WebServlet("/test")

public class ServletTest extends HttpServlet {

    private static final long serialVersionUID = 1L;

    public ServletTest() {

        super();

    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        response.getWriter().append("Served at: ").append(request.getContextPath());

        ApplicationContext context=new ClassPathXmlApplicationContext("zhujie.xml");

        Service service=(Service) context.getBean("service");

        String test=service.fun();

        response.getWriter().append(test);

    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        doGet(request, response);

    }

}

浏览器结果如下

Spring框架context的注解管理方法之二 使用注解注入基本类型和对象属性 注解annotation和配置文件混合使用(半注解)

自动装载的这种方法   @Autowired    原理是通过类名找到定义的对象，这种注解使用不多，因为多个对象存在的话，注入的是哪个？

所以，使用

另一个注解，可以明确到底注入哪个对象

@Resource(name="dao")
private Dao dao;

这种方法使用较多

 注入基本类型和对象属性

半注解方式

package cn.itcast.domain;

import javax.annotation.PostConstruct;

import javax.annotation.PreDestroy;

import javax.annotation.Resource;

import org.springframework.beans.factory.annotation.Autowired;

import org.springframework.beans.factory.annotation.Qualifier;

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

import org.springframework.context.annotation.Scope;

import org.springframework.stereotype.Component;

//<bean name="user" class="cn.itcast.domain.User" />

@Component("user")

/*    //注册service层对象

@Service

@Repository        //注册Dao层对象

@Controller        //注册Web层对象*/

//<bean scope="singleton|prototype" >

@Scope("prototype")

public class User {

    @Value("tom") //为name赋值为tom

    private String name;

    private Integer age;

    @Resource(name="car2")

    /*

     * @Autowired 自动注入 有就注入 默认名car开始

     * 注意:如果匹配到多个会抛出异常*/

//     @Autowired

    /*

     *  当自动注入匹配到多个对象时,可以使用@Qualifier 指定具体注入哪一个(不常用)

     */

    @Autowired

    @Qualifier("car2")

    private Car car;

    public User() {

        super();

    }

    public String getName() {

        return name;

    }

    public void setName(String name) {

        this.name = name;

    }

    public Integer getAge() {

        return age;

    }

    //将赋值注解放到set方法上,可执行方法中判断逻辑

    @Value("18")//为age赋值

    public void setAge(Integer age) {

        System.out.println("public void setAge(Integer age)!");

        this.age = age;

    }

    public Car getCar() {

        return car;

    }

    public void setCar(Car car) {

        this.car = car;

    }

    //<bean init-method="init" >

    @PostConstruct

    public void init() {

        System.out.println("构造之后初始化方法!");

    }

    //<bean destory-method="destory" >

    @PreDestroy

    public void destory() {

        System.out.println("销毁之前销毁方法!");

    }

    @Override

    public String toString() {

        return "User [name=" + name + ", age=" + age + ", car=" + car + "]";

    }

}

引用类型Car

package cn.itcast.domain;

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

import org.springframework.stereotype.Component;

@Component

public class Car {

    @Value("哈佛H6")

    private String name;

    public String getName() {

        return name;

    }

    public void setName(String name) {

        this.name = name;

    }

    @Override

    public String toString() {

        return "Car [name=" + name + "]";

    }

}

XML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 ">

    <!-- 开启ioc注解 -->

    <context:component-scan base-package="cn.itcast"></context:component-scan>

    <!---->

    <bean name="car1" class="cn.itcast.domain.Car" >

        <property name="name" value="五菱宏光"></property>

    </bean>

     <bean name="car2" class="cn.itcast.domain.Car" >

        <property name="name" value="长安CS95" ></property>

    </bean> 

</beans>

测试类

package cn.itcast.a_ioc;

import org.junit.Test;

import org.springframework.context.ApplicationContext;

import org.springframework.context.support.ClassPathXmlApplicationContext;

import cn.itcast.domain.User;

public class Demo {

    @Test

    public void fun1(){

        ApplicationContext ac = new ClassPathXmlApplicationContext("applicationContext.xml");

        User u1 = (User) ac.getBean("user");

        User u2 = (User) ac.getBean("user");

        System.out.println(u1==u2);

    }

    @Test

    public void fun2(){

        ApplicationContext ac = new ClassPathXmlApplicationContext("applicationContext.xml");

        User u1 = (User) ac.getBean("user");

        System.out.println(u1);

    }

}

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