Spring EL Lists, Maps example-优快云博客

本文通过示例介绍了如何使用 Spring 表达式语言 (Spring EL) 从 Map 和 List 中获取值。示例包括了通过注解方式及 XML 文件配置方式演示 Spring EL 的用法。

In this article, we show you how to use Spring EL to get value from Map and List. Actually, the way of SpEL works with Map and List is exactly same with Java. See example :

        //get map whete key = 'MapA'
    @Value("#{testBean.map['MapA']}")
    private String mapA;

    //get first value from list, list is 0-based.
    @Value("#{testBean.list[0]}")
    private String list;

Spring EL in Annotation

Here, created a HashMap and ArrayList, with some initial data for testing.

package com.mkyong.core;

import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Component;

@Component("customerBean")
public class Customer {

    @Value("#{testBean.map['MapA']}")
    private String mapA;

    @Value("#{testBean.list[0]}")
    private String list;

    public String getMapA() {
        return mapA;
    }

    public void setMapA(String mapA) {
        this.mapA = mapA;
    }

    public String getList() {
        return list;
    }

    public void setList(String list) {
        this.list = list;
    }

    @Override
    public String toString() {
        return "Customer [mapA=" + mapA + ", list=" + list + "]";
    }

}

package com.mkyong.core;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
import org.springframework.stereotype.Component;

@Component("testBean")
public class Test {

    private Map<String, String> map;
    private List<String> list;

    public Test() {
        map = new HashMap<String, String>();
        map.put("MapA", "This is A");
        map.put("MapB", "This is B");
        map.put("MapC", "This is C");

        list = new ArrayList<String>();
        list.add("List0");
        list.add("List1");
        list.add("List2");

    }

    public Map<String, String> getMap() {
        return map;
    }

    public void setMap(Map<String, String> map) {
        this.map = map;
    }

    public List<String> getList() {
        return list;
    }

    public void setList(List<String> list) {
        this.list = list;
    }

}

Run it

       Customer obj = (Customer) context.getBean("customerBean");
       System.out.println(obj);

Output

Customer [mapA=This is A, list=List0]

Spring EL in XML

See equivalent version in bean definition XML file.

<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-3.0.xsd">

    <bean id="customerBean" class="com.mkyong.core.Customer">
        <property name="mapA" value="#{testBean.map['MapA']}" />
        <property name="list" value="#{testBean.list[0]}" />
    </bean>

    <bean id="testBean" class="com.mkyong.core.Test" />

</beans>

转载于:https://www.cnblogs.com/ghgyj/p/4749608.html