Spring杂记之Bean注入(xml)

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I. 声明一个简单的Bean

1. 声明bean：

package io.codetisan.spring;public class Singer {    public void sing() {        System.out.println("when i was young i'd listen to the radio");    }}

2. spring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"    xsi:schemaLocation="http://www.springframework.org/schema/beans    http://www.springframework.org/schema/beans/spring-beans.xsd">    <bean id="singer" class="io.codetisan.spring.Singer" /></beans>

3. 测试代码：

package io.codetisan.spring;import org.springframework.context.ApplicationContext;import org.springframework.context.support.ClassPathXmlApplicationContext;public class MainTest {    public static void main(String[] args) {        ApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml");        Singer singer = context.getBean("singer",Singer.class);        singer.sing();    }}

II. 构造器注入

1. 声明bean

package io.codetisan.spring;public class Song {    private String name;    public Song(String name) {        this.name = name;    }    public String getName(){        return this.name;    }}

package io.codetisan.spring;public class Singer {    private String name;    private Song song;    public Singer(String name, Song song) {        this.name = name;        this.song = song;    }    public void sing() {        System.out.println("I'm " + name + " I'm singing " + song.getName());    }}

2. spring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"    xsi:schemaLocation="http://www.springframework.org/schema/beans    http://www.springframework.org/schema/beans/spring-beans.xsd">    <bean id="song" class="io.codetisan.spring.Song" >        <constructor-arg value="Yesterday Once More" />    </bean>    <bean id="singer" class="io.codetisan.spring.Singer" >        <constructor-arg value="Carpenters" />        <constructor-arg ref="song"/>    </bean></beans>

如果引用的bean只使用一次，也可以如下声明：

<?xml version="1.0" encoding="UTF-8"?><beans xmlns="http://www.springframework.org/schema/beans"    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"    xsi:schemaLocation="http://www.springframework.org/schema/beans    http://www.springframework.org/schema/beans/spring-beans.xsd">    <bean id="singer" class="io.codetisan.spring.Singer">        <constructor-arg value="Carpenters" />        <constructor-arg>            <bean class="io.codetisan.spring.Song">                <constructor-arg value="Yesterday Once More" />            </bean>        </constructor-arg>    </bean></beans>

3. 测试代码

同上

III. 注入Bean属性

1. 声明bean

package io.codetisan.spring;public class Song {    private String name;    public void setName(String name) {        this.name = name;    }    public String getName() {        return this.name;    }}package io.codetisan.spring;import java.util.List;public class Singer {    private String name;    private Song song;    private List<String> instruments;    public String getName() {        return name;    }    public void setName(String name) {        this.name = name;    }    public Song getSong() {        return song;    }    public void setSong(Song song) {        this.song = song;    }    public void sing() {        System.out.println("I'm " + name + " I'm singing " + song.getName()+" I can play with"+instruments.toString());    }    public List<String> getInstruments() {        return instruments;    }    public void setInstruments(List<String> instruments) {        this.instruments = instruments;    }}

2. spring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"    xsi:schemaLocation="http://www.springframework.org/schema/beans    http://www.springframework.org/schema/beans/spring-beans.xsd">    <bean id="song" class="io.codetisan.spring.Song">        <property name="name" value="Yesterday Once More" />    </bean>    <bean id="singer" class="io.codetisan.spring.Singer">        <property name="name" value="Carpenters" />        <property name="song" ref="song" />        <property name="instruments">            <list>                <value>guitar</value>            </list>        </property>    </bean></beans>

3. 测试代码

同上

spring提供了四种集合配置元素

集合元素用途 < list> 装配list类型的值，允许重复 < set> 装配set类型的值，不允许重复 < map> 装配map类型的值，key和value可以是任何值 < props> 装配properties类型的值，key和value必须都是string

当装配类型为数组或者java.util.Collection任意实现的属性时，选择< list>和< set>都是可以的
map和props示例

    <map>        <entry key="GUITAR" value-ref="guitar" />    </map>    <map>        <entry key-ref="guitarkey" value-ref="guitar" />    </map>    <props>        <prop key="GUITAR">strum</prop>    </props>

IV. 工厂方法创建Bean
有时候，Bean只提供了静态工厂方法来实例化的方法，Spring可以通过< bean>元素的factory-method属性来装配工厂创建的Bean

声明Bean

package io.codetisan.spring;public class Stage {    private Stage() {    }    private static class StageSingletonHolder {        private static Stage instance = new Stage();    }    public static Stage getInstance() {        return StageSingletonHolder.instance;    }}

2. spring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"    xsi:schemaLocation="http://www.springframework.org/schema/beans    http://www.springframework.org/schema/beans/spring-beans.xsd">    <bean id="stage" class="io.codetisan.spring.Stage" factory-method="getInstance"/></beans>

3. 测试代码

package io.codetisan.spring;import org.junit.Assert;import org.springframework.context.ApplicationContext;import org.springframework.context.support.ClassPathXmlApplicationContext;public class MainTest {    public static void main(String[] args) {        ApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml");        Stage stage = context.getBean("stage",Stage.class);        Assert.assertNotNull(stage);    }}

V. 初始化和销毁Bean

当我们实例化一个Bean时，可能要执行一些初始化操作来确保该Bean处于可用状态，同样的，当Bean从容器中移除时，可能也需要做一些清理工作。Spring中可以通过init-method和destroy-method来完成这些功能

1. 声明Bean

package io.codetisan.spring;public class Singer {    private String name;    public String getName() {        return name;    }    public void setName(String name) {        this.name = name;    }    public void sing() {        System.out.println("I'm " + name );    }    public void beforeSing(){        System.out.println("welcome...");    }    public void afterSing(){        System.out.println("thank you...");    }}

2. spring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"    xsi:schemaLocation="http://www.springframework.org/schema/beans    http://www.springframework.org/schema/beans/spring-beans.xsd">    <bean id="singer" class="io.codetisan.spring.Singer" init-method="beforeSing" destroy-method="afterSing">        <property name="name" value="Carpenters" />    </bean></beans>

VI. 使用Spring的命名空间p装配属性

Spring提供了一个p命名空间来简化xml的配置
如：

<?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:p="http://www.springframework.org/schema/p"    xsi:schemaLocation="http://www.springframework.org/schema/beans    http://www.springframework.org/schema/beans/spring-beans.xsd">    <bean id="song" class="io.codetisan.spring.Song">        <property name="name" value="Yesterday Once More" />    </bean>    <bean id="singer" class="io.codetisan.spring.Singer" p:name="Carpenters" p:song-ref="song"/></beans>

等同于

<?xml version="1.0" encoding="UTF-8"?><beans xmlns="http://www.springframework.org/schema/beans"    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"    xsi:schemaLocation="http://www.springframework.org/schema/beans    http://www.springframework.org/schema/beans/spring-beans.xsd">    <bean id="song" class="io.codetisan.spring.Song">        <property name="name" value="Yesterday Once More" />    </bean>    <bean id="singer" class="io.codetisan.spring.Singer">        <property name="name" value="Carpenters" />        <property name="song" ref="song" />    </bean></beans>

参考：《Spring实战第3版》

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