Spring（2）：实例化Bean的三种方法

一、实现功能

学习使用spring实例化bean，通过构造方法、静态方法和实例方法实例化Bean，同时学习Bean的别名方法

二、准备

1.Pom

<dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-core</artifactId>
    <version>4.3.7.RELEASE</version>
</dependency>
<dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-context</artifactId>
    <version>4.3.7.RELEASE</version>
</dependency>
<!--单元测试-->
<dependency>
    <groupId>junit</groupId>
    <artifactId>junit</artifactId>
    <version>4.12</version>
    <scope>test</scope>
</dependency>

2.Spirng.xml模板

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


</beans>

三、通过三种实例化Bean方法以及别名方法

1.构造方法实例化bean

（1）Bean1：需要有构造方法

package com.spring.ioc;

/**
 * Created by Administrator on 2019/10/24.
 */
public class Bean1 {
    public Bean1() {
        System.out.println("Bean1 is ini");
    }
}

（2）交由spring管理

<bean class="com.spring.ioc.Bean1" id="bean1"/>

（3）测试函数

package com.spring.ioc;

import org.junit.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

/**
 * Created by Administrator on 2019/10/24.
 */
public class test {
    @Test
    public void fortest(){

        ApplicationContext context=new ClassPathXmlApplicationContext("spring.xml");
        //通过构造方法实例化bean的测试
        Bean1 bean1=context.getBean("bean1",Bean1.class);
        System.out.println("bean1 = " + bean1);
    }
}

2.静态方法实例化bean

（1）类
-》Bean2

package com.spring.ioc;

/**
 * Created by Administrator on 2019/10/24.
 */
public class Bean2 {
    public Bean2() {
        System.out.println("Bean2 is ini");
    }
}

-》Bean2Factory

package com.spring.ioc;

/**
 * Created by Administrator on 2019/10/24.
 */
public class Bean2Factory {
    public static Bean2 getBean2(){
        return new Bean2();
    }
}

（2）交给spring

<bean class="com.spring.ioc.Bean2Factory" factory-method="getBean2" id="bean2"/>

（3）测试代码

package com.spring.ioc;

import org.junit.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

/**
 * Created by Administrator on 2019/10/24.
 */
public class test {
    @Test
    public void fortest(){

        ApplicationContext context=new ClassPathXmlApplicationContext("spring.xml");
        //通过构造方法实例化bean的测试
        Bean1 bean1=context.getBean("bean1",Bean1.class);
        System.out.println("bean1 = " + bean1);

        //通过静态方法实例化bean的测试
//        Bean2 bean2=Bean2Factory.getBean2();
        Bean2 bean2=context.getBean("bean2",Bean2.class);
        System.out.println("bean2 = " + bean2);
    }

}

3.实例方法实例化bean3

（1）类
-》Bean3

package com.spring.ioc;

/**
 * Created by Administrator on 2019/10/24.
 */
public class Bean3 {
    public Bean3() {
        System.out.println("Bean3 is ini");
    }
}

-》Bean3Factory

package com.spring.ioc;

/**
 * Created by Administrator on 2019/10/24.
 */
public class Bean3Factory {
    public Bean3 getBean3(){
        return new Bean3();
    }
}

（2）交由Spirng.xml容器管理

<bean class="com.spring.ioc.Bean3Factory" id="bean3Factory"/>
<bean class="com.spring.ioc.Bean3" id="bean3" factory-bean="bean3Factory"
      factory-method="getBean3"/>

（3）测试代码

package com.spring.ioc;

import org.junit.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

/**
 * Created by Administrator on 2019/10/24.
 */
public class test {
    @Test
    public void fortest(){

        ApplicationContext context=new ClassPathXmlApplicationContext("spring.xml");
        //通过构造方法实例化bean的测试
        Bean1 bean1=context.getBean("bean1",Bean1.class);
        System.out.println("bean1 = " + bean1);

        //通过静态方法实例化bean的测试
//        Bean2 bean2=Bean2Factory.getBean2();
        Bean2 bean2=context.getBean("bean2",Bean2.class);
        System.out.println("bean2 = " + bean2);

        //通过实例化方法实例化bean的测试
//        Bean3 bean3=Bean3Factory.getBean2();
//        Bean3Factory bean3Factory=new Bean3Factory();
//        Bean3 bean3=bean3Factory.getBean3();
        Bean3 bean3=context.getBean("bean3",Bean3.class);
        System.out.println("bean3 = " + bean3);

    }

}

4.bean别名

（1）方法一：spirng.xml中使用name属性配置

<bean class="com.spring.ioc.Bean1" name="bean1_1,bean1_2" id="bean1"/>

（2）方法二：spirng.xml中使用alias标签配置:只支持一个别名

<alias name="bean1" alias="bean1_3"/>

（3）测试代码

package com.spring.ioc;

import org.junit.Test;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

/**
 * Created by Administrator on 2019/10/24.
 */
public class test {
    @Test
    public void fortest(){

        ApplicationContext context=new ClassPathXmlApplicationContext("spring.xml");
        //通过构造方法实例化bean的测试
        Bean1 bean1=context.getBean("bean1",Bean1.class);
        System.out.println("bean1 = " + bean1);

        //通过静态方法实例化bean的测试
//        Bean2 bean2=Bean2Factory.getBean2();
        Bean2 bean2=context.getBean("bean2",Bean2.class);
        System.out.println("bean2 = " + bean2);

        //通过实例化方法实例化bean的测试
//        Bean3 bean3=Bean3Factory.getBean2();
//        Bean3Factory bean3Factory=new Bean3Factory();
//        Bean3 bean3=bean3Factory.getBean3();
        Bean3 bean3=context.getBean("bean3",Bean3.class);
        System.out.println("bean3 = " + bean3);

        //测试别名
        Bean1 bean1_1=context.getBean("bean1_1",Bean1.class);
        System.out.println("bean1_1 = " + bean1_1);
        Bean1 bean1_2=context.getBean("bean1_2",Bean1.class);
        System.out.println("bean1_2 = " + bean1_2);
        Bean1 bean1_3=context.getBean("bean1_3",Bean1.class);
        System.out.println("bean1_3 = " + bean1_3);

    }

}