第2章 装配Bean---xml显示装配---笔记4

概述：

初学者用到spring的时候自然想到用xml配置文件，xml几乎是spring实现代名词

主要学习点：

1.构造器注入。

2.属性注入

1.构造器注入

• <constructor-arg>元素
• 使用Spring3.0所引入的c-命名空间

<?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"xmlns:c="http://www.springframework.org/schema/c"xsi:schemaLocation="http://www.springframework.org/schema/beanshttp://www.springframework.org/schema/beans/spring-beans.xsdhttp://www.springframework.org/schema/contexthttp://www.springframework.org/schema/context/spring-context.xsd"><!-- <bean id="adeleSong" class="learn.chapter2.AdeleSong" /> --><!-- <bean id="girlSong" class="learn.chapter2.GirlSong"> <constructor-arg ref="adeleSong"/> </bean> --><!-- c命名空间来 --><!-- <bean id="girlSong" class="learn.chapter2.GirlSong"c:compactDisc-ref="adeleSong" /> --><!-- c命名空间来  可以用索引，不过前面必须要下划线，因为不能以数字开头--><!-- <bean id="girlSong" class="learn.chapter2.GirlSong" c:_0-ref="adeleSong" /> --><!-- c命名空间来 如果是一个参数的构造方法可以省略索引--><!-- <bean id="girlSong" class="learn.chapter2.GirlSong" c:_-ref="adeleSong" /> --><!-- <bean id="adeleSong" class="learn.chapter2.AdeleSong"><constructor-arg value="hellossssss"></constructor-arg><constructor-arg value="Adeleeeee"></constructor-arg></bean> --><!-- <bean id="adeleSong" class="learn.chapter2.AdeleSong"c:title="hellossssssss"c:artist="Adeleeeeee"/> --><bean id="adeleSong" class="learn.chapter2.AdeleSong"c:_0="hellossssssss"c:_1="Adeleeeeee"/></beans>

package learn.chapter;import static org.junit.Assert.assertNotNull;import org.junit.Test;import org.junit.runner.RunWith;import org.springframework.context.ApplicationContext;import org.springframework.context.support.ClassPathXmlApplicationContext;import org.springframework.test.context.ContextConfiguration;import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;import learn.chapter2.AdeleSong;import learn.chapter2.GirlSong;import learn.chapter2.javaConfig.CDPlayerConfig;@RunWith(SpringJUnit4ClassRunner.class)@ContextConfiguration(classes=CDPlayerConfig.class)public class XMLClearTest2 {@Testpublic void CompactDiscIsNotNull(){ApplicationContext ac = new ClassPathXmlApplicationContext("constructor.xml");assertNotNull(ac.getBean("girlSong"));GirlSong girl = (GirlSong) ac.getBean("girlSong");girl.getCompactDisc().play();}@Testpublic void CompactDisc(){ApplicationContext ac = new ClassPathXmlApplicationContext("constructor.xml");assertNotNull(ac.getBean("adeleSong"));AdeleSong girl = (AdeleSong) ac.getBean("adeleSong");girl.play();}}

package learn.chapter2;import org.springframework.stereotype.Component;/** * 创建一个Adele的歌曲hello * @author Administrator * */@Componentpublic class AdeleSong implements CompactDisc{private String title = "hello";private String artist = "Adele";public AdeleSong() {super();// TODO Auto-generated constructor stub}public AdeleSong(String title, String artist) {super();this.title = title;this.artist = artist;}public void play() {System.out.println("歌曲为：" + title + "\t歌手为：" + artist);}}

总结：构造方法注入有三种方式

<constructor-arg value =""/>

<c:_索引-ref=Id/>

<c:构造参数名-ref=beanId/>

2.装配集合（这时候c:空间不可以装配集合）

package learn.chapter2;import java.util.List;public class BlankDisc implements CompactDisc {private String title;private String artist;private List<String> tracks;public BlankDisc(String title, String artist, List<String> tracks) {super();this.title = title;this.artist = artist;this.tracks = tracks;}public void play() {System.out.println("专辑为" + title + "\t 歌手为：" + artist);if(null!=tracks && tracks.size() > 0){for (String track : tracks){System.out.println("---磁道: " + track);}}}}

<?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"xmlns:c="http://www.springframework.org/schema/c"xsi:schemaLocation="http://www.springframework.org/schema/beanshttp://www.springframework.org/schema/beans/spring-beans.xsdhttp://www.springframework.org/schema/contexthttp://www.springframework.org/schema/context/spring-context.xsd"<!-- 容易报空指针异常 --><!-- <bean id="compactDisc" class="learn.chapter2.BlankDisc"><constructor-arg value="海阔天空"></constructor-arg><constructor-arg value="beyond"></constructor-arg><constructor-arg ><null/></constructor-arg></bean> --><!-- 容易报空指针异常 --><bean id="compactDisc" class="learn.chapter2.BlankDisc"><constructor-arg value="海阔天空"></constructor-arg><constructor-arg value="beyond"></constructor-arg><constructor-arg ><list><value>磁道一</value><value>磁道二</value><value>磁道仨</value><value>磁道四</value><value>磁道五</value></list></constructor-arg></bean></beans>

测试类：

package learn.chapter;import static org.junit.Assert.assertNotNull;import org.junit.Test;import org.junit.runner.RunWith;import org.springframework.context.ApplicationContext;import org.springframework.context.support.ClassPathXmlApplicationContext;import org.springframework.test.context.ContextConfiguration;import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;import learn.chapter2.AdeleSong;import learn.chapter2.CompactDisc;import learn.chapter2.GirlSong;import learn.chapter2.javaConfig.CDPlayerConfig;@RunWith(SpringJUnit4ClassRunner.class)@ContextConfiguration(classes=CDPlayerConfig.class)public class XMLClearTest2 {@Testpublic void CompactDiscIsNotNull(){ApplicationContext ac = new ClassPathXmlApplicationContext("constructor.xml");assertNotNull(ac.getBean("girlSong"));GirlSong girl = (GirlSong) ac.getBean("girlSong");girl.getCompactDisc().play();}@Testpublic void CompactDisc(){ApplicationContext ac = new ClassPathXmlApplicationContext("constructor.xml");assertNotNull(ac.getBean("adeleSong"));AdeleSong girl = (AdeleSong) ac.getBean("adeleSong");girl.play();}/** * 测试集合 */@Testpublic void CompactDiscSet(){ApplicationContext ac = new ClassPathXmlApplicationContext("constructor.xml");assertNotNull(ac.getBean("compactDisc"));CompactDisc girl = (CompactDisc) ac.getBean("compactDisc");girl.play();}}

总结主要涉及到值的注入，这里可以用list 和set ，两者的区别就是list能保证顺序，而set保证唯一性

注入对象：

package learn.chapter2;import java.util.List;import org.springframework.stereotype.Component;@Componentpublic class GirlSong {private CompactDisc compactDisc;private List<CompactDisc> compactDiscs;public GirlSong(List<CompactDisc> compactDiscs) {super();this.compactDiscs = compactDiscs;}public GirlSong(CompactDisc compactDisc) {this.compactDisc = compactDisc;}public CompactDisc getCompactDisc() {return compactDisc;}public void setCompactDisc(CompactDisc compactDisc) {this.compactDisc = compactDisc;}}

<bean id="adeleSong" class="learn.chapter2.AdeleSong"/><bean id="ananRyokoSong" class="learn.chapter2.AnanRyokoSong"/><bean id="keshaSong" class="learn.chapter2.KeshaSong"/><bean id="girlSong" class="learn.chapter2.GirlSong"><constructor-arg><list><ref bean="adeleSong"/><ref bean="ananRyokoSong"/><ref bean="keshaSong"/></list></constructor-arg></bean>

测试方法：

/** * 测试集合注入bean */@Testpublic void CompactDiscBeanSet(){ApplicationContext ac = new ClassPathXmlApplicationContext("constructor.xml");assertNotNull(ac.getBean("girlSong"));GirlSong girl = (GirlSong) ac.getBean("girlSong");List<CompactDisc> lis = girl.getCompactDiscs();for(CompactDisc d : lis){d.play();}}

结果：

歌曲为：hello 歌手为：Adele
歌曲为：Refrain 歌手为：AnanRyoko
歌曲为：Tik Tok 歌手为：Kesha

2.属性注入

属性注入跟构造方式注入很相似，对应构造有c:命名空间 属性有p:命名空间，同时提供非常有用的帮助util标签，完成组件的效果

属性注入一般用于弱依赖，也就是可有可无补充条件，而构造一般用于强依赖，也就是必要的条件

定义三个属性：

package learn.chapter2;import java.util.List;public class BlankDisc implements CompactDisc {private String title;private String artist;private List<String> tracks;public String getTitle() {return title;}public void setTitle(String title) {this.title = title;}public String getArtist() {return artist;}public void setArtist(String artist) {this.artist = artist;}public List<String> getTracks() {return tracks;}public void setTracks(List<String> tracks) {this.tracks = tracks;}@Overridepublic String toString() {return "BlankDisc [title=" + title + ", artist=" + artist + ", tracks=" + tracks + "]";}public void play() {System.out.println("专辑为" + title + "\t 歌手为：" + artist);if(null!=tracks && tracks.size() > 0){for (String track : tracks){System.out.println("---磁道: " + track);}}}}

<?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"xmlns:c="http://www.springframework.org/schema/c"xsi:schemaLocation="http://www.springframework.org/schema/beanshttp://www.springframework.org/schema/beans/spring-beans.xsdhttp://www.springframework.org/schema/contexthttp://www.springframework.org/schema/context/spring-context.xsd"><!-- 只注入两个属性 --><bean id="blankDisc" class="learn.chapter2.BlankDisc"><property name="title" value="hello"/><property name="artist" value="adele"/></bean></beans>

测试类：

package learn.chapter;import static org.junit.Assert.assertNotNull;import org.junit.Test;import org.junit.runner.RunWith;import org.springframework.context.ApplicationContext;import org.springframework.context.support.ClassPathXmlApplicationContext;import org.springframework.test.context.ContextConfiguration;import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;import learn.chapter2.BlankDisc;import learn.chapter2.javaConfig.CDPlayerConfig;@RunWith(SpringJUnit4ClassRunner.class)@ContextConfiguration(classes=CDPlayerConfig.class)public class XMLClearTest2 {/** * 测试集合注入bean */@Testpublic void CompactDiscBeanSet(){ApplicationContext ac = new ClassPathXmlApplicationContext("constructor.xml");assertNotNull(ac.getBean("blankDisc"));BlankDisc girl = (BlankDisc) ac.getBean("blankDisc");System.out.println(girl);}}

结果：

BlankDisc [title=hello, artist=adele, tracks=null]

接下来用p空间来设置，首先要添加命名空间的头部 xmlns:p="http://www.springframework.org/schema/p"

<?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"xmlns:c="http://www.springframework.org/schema/c"xmlns:p="http://www.springframework.org/schema/p"xsi:schemaLocation="http://www.springframework.org/schema/beanshttp://www.springframework.org/schema/beans/spring-beans.xsdhttp://www.springframework.org/schema/contexthttp://www.springframework.org/schema/context/spring-context.xsd"><!-- 只注入两个属性 --><!-- <bean id="blankDisc" class="learn.chapter2.BlankDisc"><property name="title" value="hello"/><property name="artist" value="adele"/></bean> --><!-- 只注入两个属性 采用p空间--><bean id="blankDisc" class="learn.chapter2.BlankDisc"p:title="hello" p:artist="adele"/></beans>

测试的结果是一样的。注意如果是字面值不用-ref，反之

通过属性配置集合

<!-- 用属性配置集合，这时候只能有property属性 --><bean id="blankDisc" class="learn.chapter2.BlankDisc"><property name="title" value="hello" /><property name="artist" value="adele" /><property name="tracks"><list><value>磁道1</value><value>磁道2</value><value>磁道3</value></list></property></bean>

结果为：

BlankDisc [title=hello, artist=adele, tracks=[磁道1, 磁道2, 磁道3]]

通过帮助命名空间：增加头信息

xmlns:util="http://www.springframework.org/schema/util"

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

<?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"xmlns:c="http://www.springframework.org/schema/c" xmlns:p="http://www.springframework.org/schema/p"xmlns:util="http://www.springframework.org/schema/util"xsi:schemaLocation="http://www.springframework.org/schema/beanshttp://www.springframework.org/schema/beans/spring-beans.xsdhttp://www.springframework.org/schema/contexthttp://www.springframework.org/schema/context/spring-context.xsdhttp://www.springframework.org/schema/utilhttp://www.springframework.org/schema/util/spring-util.xsd"><!-- property帮助标签 util，首先要引入命名空间 --><!-- 它可以将list单独分开出来，其它bean可以复用 --><util:list id="trackList"><value>磁道1</value><value>磁道2</value><value>磁道3</value></util:list ><util:map><entry key=""><value></value></entry></util:map><bean id="blankDisc" class="learn.chapter2.BlankDisc"p:title="hello"p:artist="adele"p:tracks-ref="trackList"></bean></beans>

测试的效果是一样的

其它所有的标签

• util:constant   引用某个类型的public static域，并将其暴露为bean
• util:list            创建一个java.util.List类型的bean，其中包含值或引用
• util:map         创建一个java.util.Map类型的bean，其中包含值或引用
• util:properties 创建一个java.util.Properties类型的bean
• util:property-path 引用一个bean的属性（或内嵌属性），并将其暴露为bean
• util:set             创建一个java.util.Set类型的bean，其中包含值或引用

总结：构造方法注入和属性注入，属性注入相对于构造多了util标签，方便复用