Spring_总结_03_装配Bean(三)之XML配置

一、前言

本文承接上一节:Spring_总结_03_装配Bean(二)之Java配置

上一节说到,当需要显示配置时,首选类型安全并且比XML更强大Java配置。

那什么时候使用XML配置呢?

(1)维护已有XML配置

(2)想使用便利的XML命名空间,并且在JavaConfig中没有同样的实现。

 

二、引入schema

Spring_总结_03_装配Bean(三)之XML配置Spring_总结_03_装配Bean(三)之XML配置
<?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">


</beans>
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用来装配bean的最基本的XML元素包含在spring-beans模式中,在上面这个XML文件中,它被定义为根命名空间。

<beans>是该模式中的一个元素,它是所有Spring配置文件的根元素。

 

三、声明Bean

    <bean id="compactDisc" class="soundsystem.SgtPeppers"></bean>

id :指定bean的名字,以便于被其他bean引用。

class : 全类名,指定创建bean的Class

 

注:

(1)通过xml配置的方式,我们不再直接负责创SgtPeppers,而在JavaConfig中,我们却是需要这样做的。当Spring发现 <bean>元素时,他会调用默认构造器来创建bean。

(2)将bean的类型以字符串的形式设置在class属性中,不便于重构。(如修改类名时)

 

 

四、构造器注入

注入bean有两种方式:

(1)构造器注入

(2)属性注入

 

这两种方式如何选择:强依赖选择构造器注入,可选性依赖使用属性注入。

 

1. constructor-arg

Spring_总结_03_装配Bean(三)之XML配置Spring_总结_03_装配Bean(三)之XML配置
<?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="compactDisc" class="soundsystem.SgtPeppers"></bean>

    <bean id="cdPlayer"    class="soundsystem.CDPlayer">
        <constructor-arg ref="compactDisc" />
    </bean>
    
</beans>
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2. c-命名空间

Spring_总结_03_装配Bean(三)之XML配置Spring_总结_03_装配Bean(三)之XML配置
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:c="http://www.springframework.org/schema/c"
       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="compactDisc" class="soundsystem.SgtPeppers"></bean>
  
    <bean id="cdPlayer" class="soundsystem.CDPlayer"
          c:cd-ref="compactDisc"/>
    
    <bean id="cdPlayer2" class="soundsystem.CDPlayer"
          c:_0-ref="compactDisc"/>


</beans>
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(1)构造器参数名

"c:"为命名空间

“-ref”表示注入引用

“cd”为构造器参数名

 

(2)构造器参数索引

“_i”为第i个参数。

表示为第i个参数注入bean

 

3. 字面量

将字面量注入到构造器中

(1)constructor-arg

Spring_总结_03_装配Bean(三)之XML配置Spring_总结_03_装配Bean(三)之XML配置
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:c="http://www.springframework.org/schema/c"
       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="blankDisc" class="soundsystem.BlankDisc">
        <constructor-arg value="字面量"/>
    </bean>



</beans>
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(2)构造器参数名

Spring_总结_03_装配Bean(三)之XML配置Spring_总结_03_装配Bean(三)之XML配置
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:c="http://www.springframework.org/schema/c"
       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="blankDisc" class="soundsystem.BlankDisc"
          c:_title="标题"
          c:_author="作者" />

</beans>
View Code

 

(3)构造器参数索引

Spring_总结_03_装配Bean(三)之XML配置Spring_总结_03_装配Bean(三)之XML配置
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:c="http://www.springframework.org/schema/c"
       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="blankDisc" class="soundsystem.BlankDisc"
          c:_0="标题"
          c:_1="作者" />

</beans>
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4. 集合

BlankDisc

Spring_总结_03_装配Bean(三)之XML配置Spring_总结_03_装配Bean(三)之XML配置
public class BlankDisc  implements CompactDisc{
    private String title;
    private String author;
    private List<String> tracks;

    public BlankDisc(String title, String author, List<String> tracks) {
        this.title = title;
        this.author = author;
        this.tracks = tracks;
    }

    public void play(){
        System.out.print("aaaaaaaa");
    }
}
View Code

 

beans.xml

Spring_总结_03_装配Bean(三)之XML配置Spring_总结_03_装配Bean(三)之XML配置
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:c="http://www.springframework.org/schema/c"
       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="compactDisc" class="soundsystem.BlankDisc">
        <constructor-arg value="标题"/>
        <constructor-arg value="作者"/>
        <constructor-arg>
            <list>
                <value>111111111</value>
                <value>222222222</value>
                <value>333333333</value>
                <value>444444444</value>
                <value>555555555</value>
            </list>
        </constructor-arg>
    </bean>

    <bean id="compactDisc2" class="soundsystem.BlankDisc">
        <constructor-arg value="标题"/>
        <constructor-arg value="作者"/>
        <constructor-arg>
            <list>
                <ref bean="compactDisc" />
                <ref bean="compactDisc" />
                <ref bean="compactDisc" />
                <ref bean="compactDisc" />
            </list>
        </constructor-arg>
    </bean>


    <bean id="compactDisc3" class="soundsystem.BlankDisc">
        <constructor-arg value="标题"/>
        <constructor-arg value="作者"/>
        <constructor-arg>
            <set>
                <value>111111111</value>
                <value>222222222</value>
                <value>333333333</value>
                <value>444444444</value>
                <value>555555555</value>
            </set>
        </constructor-arg>
    </bean>

</beans>
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五、属性注入

1.注入引用

Spring_总结_03_装配Bean(三)之XML配置Spring_总结_03_装配Bean(三)之XML配置
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:c="http://www.springframework.org/schema/c"
       xmlns:p="http://www.springframework.org/schema/p"
       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="compactDisc" class="soundsystem.CompactDisc" />

    <bean id="cdPlayer" class="soundsystem.CDPalyer" >
        <property name="compactDisc" ref="compactDisc" />
    </bean>

    <bean id="cdPlayer2" class="soundsystem.CDPalyer"
          p:compactDisc-ref="compactDisc"/>

</beans>
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2.注入字面量

BlankDisc

Spring_总结_03_装配Bean(三)之XML配置Spring_总结_03_装配Bean(三)之XML配置
public class BlankDisc  implements CompactDisc{
    private String title;
    private String author;
    private List<String> tracks;

    public void setTitle(String title) {
        this.title = title;
    }

    public void setAuthor(String author) {
        this.author = author;
    }

    public void setTracks(List<String> tracks) {
        this.tracks = tracks;
    }

    public void play(){
        System.out.print("aaaaaaaa");
    }
}
View Code

 

beans.xml

Spring_总结_03_装配Bean(三)之XML配置Spring_总结_03_装配Bean(三)之XML配置
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:c="http://www.springframework.org/schema/c"
       xmlns:p="http://www.springframework.org/schema/p"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:util="http://www.springframework.org/schema/plugin"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/plugin http://www.springframework.org/schema/plugin/spring-plugin.xsd">

    <!--1.空属性-->
    <bean id="reallyBlankDisc" class="soundsystem.BlankDisc" />

    <!--2.注入list-->
    <bean id="compactBlankDisc" class="soundsystem.BlankDisc" >
        <property name="title" value="标题"/>
        <property name="author" value="作者"/>
        <property name="tracks" >
            <list>
                <value>11111111</value>
                <value>11111111</value>
                <value>11111111</value>
                <value>11111111</value>
            </list>
        </property>

    </bean>


    <!--3.p命名空间装配引用与装配字面量的唯一区别在于是否带有 -ref
          p命名空间不能用来装配集合
    -->
    <bean id="compactBlankDisc2" class="soundsystem.BlankDisc" 
          p:title="标题"
          p:author="作者">
        <property name="tracks" >
            <list>
                <value>11111111</value>
                <value>11111111</value>
                <value>11111111</value>
                <value>11111111</value>
            </list>
        </property>
    </bean>

    <!--4.<util:list>会创建一个列表bean -->
    <util:list id="tracklist">
        <value>1111111111</value>
        <value>1111111111</value>
        <value>1111111111</value>
        <value>1111111111</value>
    </util:list>
    <bean id="compactBlankDisc3" class="soundsystem.BlankDisc"
          p:title="标题"
          p:author="作者"
          p:tracks-ref="tracklist" />
</beans>
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