In the previous example, How do I access collections members using Spring EL?, you have seen how to access a member of a collection using Spring EL square-braces [] operator. In this post you will learn how to use the same operator to access an element of a Map object.
For demonstration, we will use the same Book class in the previous example to create the bean. The class without the corresponding getters and setters is as follows:
package org.kodejava.spring.core.el;
public class Book {
private Long id;
private String title;
private String author;
private String type;
// Getters & Setters
}
Next, let’s create the spring configuration file. In this configuration file we create a map using the <util:map> with the map id of books and add some key-value pair entries in the map.
<?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:util="http://www.springframework.org/schema/util" 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 http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util.xsd">
<util:map id="books">
<entry key="0-201-61622-X" value="The Pragmatic Programmer" />
<entry key="978-1-934356-56-2" value="Hello, Android" />
<entry key="978-1-933988-69-6" value="Secret of The JavaScript Ninja" />
<entry key="978-1-449-37017-6" value="Java EE 7 Essentials" />
<entry key="9781935182962" value="Spring Roo in Action" />
</util:map>
<bean id="book1" class="org.kodejava.spring.core.el.Book" p:title="#{books['9781935182962']}" />
<bean id="book2" class="org.kodejava.spring.core.el.Book" p:title="#{books['978-1-933988-69-6']}" />
</beans>
After defining the map, you can see how we access an element of the map. We use the square-braces operator [], we use the same operator as we are accessing a collection member. But instead of passing the index to the operator we pass the key of the map element that we are going to read.
<bean id="book2" class="org.kodejava.spring.core.el.Book" p:title="#{books['978-1-933988-69-6']}"/>
Finally, to run the configuration you’ll need to create the following class:
package org.kodejava.spring.core.el;
import org.springframework.context.support.ClassPathXmlApplicationContext;
public class SpELMapExample {
public static void main(String[] args) {
try (ClassPathXmlApplicationContext context =
new ClassPathXmlApplicationContext("spel-map.xml")) {
Book book1 = (Book) context.getBean("book1");
Book book2 = (Book) context.getBean("book2");
System.out.println("book1.getTitle() = " + book1.getTitle());
System.out.println("book2.getTitle() = " + book2.getTitle());
}
}
}
And example of output produced by this code can be seen below:
book1.getTitle() = Spring Roo in Action
book2.getTitle() = Secret of The JavaScript Ninja
Maven Dependencies
<dependencies>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-core</artifactId>
<version>5.3.23</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-beans</artifactId>
<version>5.3.23</version>
</dependency>
<dependency>
<groupId>org.springframework</groupId>
<artifactId>spring-context-support</artifactId>
<version>5.3.23</version>
</dependency>
</dependencies>
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