【备战春招】第16天 Spring入门

课程名称：Spring入门

课程章节：第2章 使用Spring实例化Bean

课程讲师： 西昆仑

课程内容：

一、实例化Bean的方式

1、通过构造方法实例化Bean

//Bean1.class

public class Bean1 {

public Bean1(){

System.out.println("Bean1.Bean1");

}

}

//spring.xml

<bean class = "com.imooc.spring.ioc.class05.Bean1" id="bean1"/>

//Class005Test.clss

public void test(){

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

Bean1 bean1 = context.getBean("bean1",Bean1.class);

System.out.println("bean1="+bean1);

}

运行结果

2、通过静态方法实例化Bean

//Bean2.class

public class Bean2 {

public Bean2(){

System.out.println("Bean2.Bean2");

}

}

//Bean2Factory.class

public class Bean2Factory {

public static Bean2 getBean2(){

return new Bean2();

}

}

//spring.xml

<bean class = "com.imooc.spring.ioc.class05.Bean2Factory" factory-method = "getBean2" id="bean2"/>

//Class005Test.clss

public void test(){

//Bean2 bean2 = Bean2Factory.getBean2();

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

Bean2 bean2 = context.getBean("bean2",Bean2.class);

}

运行结果

3、通过实例方法实例化Bean

//Bean3.class

public class Bean3 {

public Bean3(){

System.out.println("Bean3.Bean3");

}

}

//Bean3Factory.class

public class Bean3Factory {

public Bean3 getBean3(){

return new Bean3();

}

}

//spring.xml

<bean class = "com.imooc.spring.ioc.class05.Bean3Factory" id="bean3Factory"/>

<bean class = "com.imooc.spring.ioc.class05.Bean3" factory-bean = "bean3Factory" factory-method = "getBean3" id="bean3"/>

//Class005Test.clss

public void test(){

//Bean3Factory bean3Factory = new Bean3Factory();

//Bean3 bean3 = bean3Factory.getBean3();

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

Bean3 bean3 = context.getBean("bean3",Bean3.class);

}

运行结果

4、Bean的别名

//spring.xml

<bean class="com.imooc.spring.ioc.class05.Bean1" name="bean1_1,bean1_2" id="bean1"/>

<alias name="bean1" alias="bean1_3"/> //只支持一个别名

//Class005Test.clss

public void test(){

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

Bean1 bean1_1 = context.getBean("bean1_1",Bean1.class);

Bean1 bean1_2 = context.getBean("bean1_2",Bean1.class);

Bean1 bean1_3 = context.getBean("bean1_3",Bean1.class);

System.out.println("bean1="+bean1);

}

运行结果

二、注入Bean的方式

1、通过构造方法注入Bean

//Bean对象定义

《图片》

//spring.xml

<bean class="com.imooc.spring.ioc.class06.AnotherBean" id="anotherBean"/>

<bean class="com.imooc.spring.ioc.class06.Bean" id="bean">

<constructor-arg index="0" name="anotherBean" type="com.imooc.spring.ioc.class06.AnotherBean" ref="anotherBean"/>

<constructor-arg index="1" name="string" type="java.lang.String" value="aaaaa"/>

</bean>

//Class006Test.clss

public void test(){

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

Bean bean = context.getBean("bean",Bean.class);

System.out.println("bean="+bean);

}

2、通过set方法注入Bean

//Bean对象定义

//spring.xml

<bean class="com.imooc.spring.ioc.class06.AnotherBean" id="anotherBean"/>

<bean class="com.imooc.spring.ioc.class06.Bean" id="bean">

<constructor-arg index="0" name="anotherBean" type="com.imooc.spring.ioc.class06.AnotherBean" ref="anotherBean"/>

<constructor-arg index="1" name="string" type="java.lang.String" value="aaaaa"/>

<property name="anotherBean1" ref="anotherBean"/>

<property name="string1" ref="bbbbb"/>

</bean>

运行结果

简化写法：

//spring.xml

<bean class="com.imooc.spring.ioc.class06.AnotherBean" id="anotherBean"/>

<bean class="com.imooc.spring.ioc.class06.Bean" id="bean">

c:anotherBean-ref="anotherBean" c:string="ccccc"

p:anotherBean1-ref="anotherBean" p:string="ddddd"/>

</bean>

3、集合Bean的注入

//spring.xml

<bean class="com.imooc.spring.ioc.class06.Bean" id="bean">

<constructor-arg index="0" name="anotherBean" type="com.imooc.spring.ioc.class06.AnotherBean" ref="anotherBean"/>

<constructor-arg index="1" name="string" type="java.lang.String" value="aaaaa"/>

<property name="anotherBean1" ref="anotherBean"/>

<property name="string1" ref="bbbbb"/>

<property name="stringList">

<list>

<value>aaaaa</value>

<value>bbbbb</value>

</list>

</property>

<property name="anotherBeanList">

<list>

<ref bean="anotherBean"/>

<ref bean="anotherBean"/>

</list>

</property>

<property name="stringSet">

<set>

<value>aaaaa</value>

<value>bbbbb</value>

</set>

</property>

<property name="anotherBeanSet">

<set>

<ref bean="anotherBean"/>

<ref bean="anotherBean"/>

</set>

</property>

</bean>

运行结果

课程收获：

本节课程讲解了bean实例化及注入的方式，内容较容易理解，但各种方式对应的使用场景及优劣势还需继续摸索，期待后续的课程学习。