从头认识Spring-1.16 SpEl对集合的操作-建立集合以及访问集合的元素，以<util:list/>为例
Posted 李灵晖
tags:
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这一章节我们来讨论一下如何建立集合以及访问集合的元素？
1.建立集合？
（1）domain
蛋糕类：
package com.raylee.my_new_spring.my_new_spring.ch01.topic_1_20;
public class Cake {
private String name = "";
private double size = 0;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public double getSize() {
return size;
}
public void setSize(double size) {
this.size = size;
}
}
（2）配置文件
<?xml version="1.0" encoding="UTF-8"?> <beans xmlns="http://www.springframework.org/schema/beans" xmlns:context="http://www.springframework.org/schema/context" xmlns:p="http://www.springframework.org/schema/p" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:tx="http://www.springframework.org/schema/tx" xmlns:aop="http://www.springframework.org/schema/aop" xmlns:util="http://www.springframework.org/schema/util" xsi:schemaLocation=" http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.1.xsdhttp://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util-2.0.xsd
http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.1.xsdhttp://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-3.1.xsdhttp://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util-3.1.xsdhttp://www.springframework.org/schema/data/jpa http://www.springframework.org/schema/data/jpa/spring-jpa-1.0.xsdhttp://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop.xsd"><util:list id="cakes"><bean class="com.raylee.my_new_spring.my_new_spring.ch01.topic_1_20.Cake"p:name="blueberry cheese cake" p:size="5" scope="prototype" /><bean class="com.raylee.my_new_spring.my_new_spring.ch01.topic_1_20.Cake"p:name="chocolate cheese cake" p:size="6" scope="prototype" /><bean class="com.raylee.my_new_spring.my_new_spring.ch01.topic_1_20.Cake"p:name="banana oatmel mousse cake" p:size="7" scope="prototype" /><bean class="com.raylee.my_new_spring.my_new_spring.ch01.topic_1_20.Cake"p:name="vanilla eclair" p:size="8" scope="prototype" /><bean class="com.raylee.my_new_spring.my_new_spring.ch01.topic_1_20.Cake"p:name="ligueur perfumed triplet cake" p:size="5.5" scope="prototype" /></util:list></beans>
上面的配置文件需要注意的地方：
<1>引入util的命名空间，需要在头部加上：
xmlns:util="http://www.springframework.org/schema/util"http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util-2.0.xsd<3>除了<util:list/>还有<util:set/>和<util:map/>等常用容器
<4>Bean由于在容器里面，因此不需要id，当做内部类来引入
2.访问集合的元素
（1）domain
蛋糕类：（沿用上面的代码）
package com.raylee.my_new_spring.my_new_spring.ch01.topic_1_20;
public class Cake {
private String name = "";
private double size = 0;
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public double getSize() {
return size;
}
public void setSize(double size) {
this.size = size;
}
}
厨师类：（为了方便，我们减轻一下属性）
package com.raylee.my_new_spring.my_new_spring.ch01.topic_1_20;
public class Chief {
private Cake cake = null;
private String name = "";
public Cake getCake() {
return cake;
}
public String getName() {
return name;
}
public Cake makeOneCake() {
return cake;
}
public void setCake(Cake cake) {
this.cake = cake;
}
public void setName(String name) {
this.name = name;
}
}
（2）测试类：
package com.raylee.my_new_spring.my_new_spring.ch01.topic_1_20;
import java.util.ArrayList;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.ApplicationContext;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(locations = {
"/com/raylee/my_new_spring/my_new_spring/ch01/topic_1_20/ApplicationContext-test.xml" })
public class CakeTest {
@Autowired
private ApplicationContext applicationContext;
@Test
public void testChief() {
@SuppressWarnings("unchecked")
ArrayList<Cake> cakes = (ArrayList<Cake>) applicationContext.getBean("cakes");
System.out.println(cakes.size());
Chief jack=applicationContext.getBean(Chief.class);
Cake cake =jack.getCake();
System.out.println(cake.getName());
}
}
（3）配置文件
<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:context="http://www.springframework.org/schema/context" xmlns:p="http://www.springframework.org/schema/p"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:tx="http://www.springframework.org/schema/tx"
xmlns:aop="http://www.springframework.org/schema/aop" xmlns:util="http://www.springframework.org/schema/util"
xsi:schemaLocation="
http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.1.xsd
http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util-2.0.xsd
http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.1.xsd
http://www.springframework.org/schema/tx http://www.springframework.org/schema/tx/spring-tx-3.1.xsd
http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util-3.1.xsd
http://www.springframework.org/schema/data/jpa http://www.springframework.org/schema/data/jpa/spring-jpa-1.0.xsd
http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
http://www.springframework.org/schema/aop http://www.springframework.org/schema/aop/spring-aop.xsd">
<util:list id="cakes">
<bean class="com.raylee.my_new_spring.my_new_spring.ch01.topic_1_20.Cake"
p:name="blueberry cheese cake" p:size="5" scope="prototype" />
<bean class="com.raylee.my_new_spring.my_new_spring.ch01.topic_1_20.Cake"
p:name="chocolate cheese cake" p:size="6" scope="prototype" />
<bean class="com.raylee.my_new_spring.my_new_spring.ch01.topic_1_20.Cake"
p:name="banana oatmel mousse cake" p:size="7" scope="prototype" />
<bean class="com.raylee.my_new_spring.my_new_spring.ch01.topic_1_20.Cake"
p:name="vanilla eclair" p:size="8" scope="prototype" />
<bean class="com.raylee.my_new_spring.my_new_spring.ch01.topic_1_20.Cake"
p:name="ligueur perfumed triplet cake" p:size="5.5" scope="prototype" />
</util:list>
<bean id="jack"
class="com.raylee.my_new_spring.my_new_spring.ch01.topic_1_20.Chief"
p:name="jack">
<property name="cake" value="#{cakes[1]}" />
</bean>
</beans>
配置文件的注意点：
<1>我们需要使用前面的#{}表达式
<2>在属性注入的时候，不再是ref，因为找不到相应的bean，直接使用value，因为我们通过表达式返回的是一个对象
测试输出：
5
chocolate cheese cake
总结：这一章节主要介绍了如何建立集合以及访问集合的元素。
目录：http://blog.csdn.net/raylee2007/article/details/50611627
我的github：https://github.com/raylee2015/my_new_spring
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