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Spring EL Calling a Method

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By on Spring

In this article, I will show you how to use spring EL to invoke a method on a bean or a literal and inject the method returned value into property.

This example uses the following frameworks:

  1. Maven 3.2.3
  2. Spring 4.1.5.RELEASE
  3. Eclipse  as the IDE, version Luna 4.4.1.

Dependencies

Add the following dependencies:

  1. spring-core
  2. spring-context
  3. spring-beans

pom.xml:

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
	<modelVersion>4.0.0</modelVersion>
	<groupId>com.javarticles.spring</groupId>
	<artifactId>springListExample</artifactId>
	<version>0.0.1-SNAPSHOT</version>

	<dependencies>
		<dependency>
			<groupId>org.springframework</groupId>
			<artifactId>spring-core</artifactId>
			<version>${spring.version}</version>
		</dependency>
		<dependency>
			<groupId>org.springframework</groupId>
			<artifactId>spring-context</artifactId>
			<version>${spring.version}</version>
		</dependency>
		<dependency>
			<groupId>org.springframework</groupId>
			<artifactId>spring-beans</artifactId>
			<version>${spring.version}</version>
		</dependency>
	</dependencies>

	<properties>
		<spring.version>4.1.6.RELEASE</spring.version>
	</properties>

</project>

Spring EL method invocation

You can invoke methods using spring EL the way you invoke methods in java. For example, to invoke a method on a bean:

"#{beanName.method()}"

In Spring EL, you can reference a bean, and nested properties using a ‘dot (.)‘ symbol.

"#{listOfTopics.getTopicsList().size()}"

Methods can also be invoked on literals, for example:

"#{'JavaThreads'.toUpperCase()}"

Spring EL in Annotation

Let’s see some examples of method invocation in spring EL. We will use some simple beans related to some topics of training.
A topic is represented by Topic bean.

Topic:

package com.javarticles.spring;

public class Topic {
    private String name;
    
    public Topic(){}

    public Topic(String name) {
        this.name = name;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }
    
    public String toString() {
        return name;
    }
}

You can create a list of topics using ListOfTopics bean.

ListOfTopics:

package com.javarticles.spring;

import java.util.ArrayList;
import java.util.List;

public class ListOfTopics {
    private String name;
    
    private List<Topic> topicsList = new ArrayList<Topic>();

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }   

    public List<Topic> getTopicsList() {
        return topicsList;
    }

    public void setTopicsList(List<Topic> topicsList) {
        this.topicsList = topicsList;
    }

    public String toString() {
        return name + topicsList;
    }    
}

Let’s configure the above beans in spring XML context.

applicationContext.xml:

<?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"
	xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
	http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-2.5.xsd">

	<context:component-scan base-package="com.javarticles.spring" />

	<bean id="listOfTopics" class="com.javarticles.spring.ListOfTopics">
		<property name="topicsList">
			<list>
				<ref local="java" />
				<ref local="scala" />
			</list>
		</property>
	</bean>

	<bean id="java" class="com.javarticles.spring.Topic">
		<property name="name" value="JavaThreads" />
	</bean>

	<bean id="scala" class="com.javarticles.spring.Topic">
		<property name="name" value="ScalaFunctions" />
	</bean>
</beans>

A Training bean is a bean composed using the Topic and ListOfTopics beans.
We will use spring EL to populate training bean’s members.

  1. @Value(“#{java.getName()}”) – Invoke getName() method on bean java
  2. @Value(“#{listOfTopics.getTopicsList().size()}”) – Invoke getTopicsList() on bean listOfTopics. The return value is a list of topics. Call size() on the returned list to know the size.
  3. @Value(“#{java.getName().toUpperCase() == ‘JavaThreads’.toUpperCase()}”) – You can call methods on literals, 'JavaThreads'.toUpperCase(). It is compared with java.getName().toUpperCase(), the returned value is a boolean
  4. @Value(“#{listOfTopics.getTopicsList()[0]}”) – Returns the first topic from the list of topics
  5. @Value(“#{T(java.util.Arrays).asList(new com.javarticles.spring.Topic(‘Spring Data’), listOfTopics.getTopicsList()[0])}”) – Creates a custom list. We have used spring EL to make a static method call on Arrays.asList(). We pass in a new Topic and an existing topic.

Training:

package com.javarticles.spring;

import java.util.List;

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

@Component
public class Training {
    @Value("#{java.getName()}")
    private String javaTopic;

    @Value("#{listOfTopics.getTopicsList().size()}")
    private int totalTopics;

    @Value("#{java.getName().toUpperCase() == 'JavaThreads'.toUpperCase()}")
    private boolean hasThreadTutorial;

    @Value("#{listOfTopics.getTopicsList()[0]}")
    private Topic firstTopic;

    @Value("#{T(java.util.Arrays).asList(new com.javarticles.spring.Topic('Spring Data'), listOfTopics.getTopicsList()[0])}")
    private List<Topic> customTopics;        

    public String getJavaTopic() {
        return javaTopic;
    }

    public int getTotalTopics() {
        return totalTopics;
    }

    public boolean isHasThreadTutorial() {
        return hasThreadTutorial;
    }

    public Topic getFirstTopic() {
        return firstTopic;
    }

    public List<Topic> getCustomTopics() {
        return customTopics;
    }       

    public void setJavaTopic(String javaTopic) {
        this.javaTopic = javaTopic;
    }

    public void setTotalTopics(int totalTopics) {
        this.totalTopics = totalTopics;
    }

    public void setHasThreadTutorial(boolean hasThreadTutorial) {
        this.hasThreadTutorial = hasThreadTutorial;
    }

    public void setFirstTopic(Topic firstTopic) {
        this.firstTopic = firstTopic;
    }

    public void setCustomTopics(List<Topic> customTopics) {
        this.customTopics = customTopics;
    }

    public String toString() {
        return "Total topics: " + totalTopics + ", Java Topic: " + javaTopic
                + ", has thread tutorial: " + hasThreadTutorial
                + ", first topic: " + firstTopic + ", custom topics: "
                + customTopics;
    }
}

To test the spring EL method invocation we just need to load the context and then print the training bean.

SpringELMethodInvocationExample:

package com.javarticles.spring;

import org.springframework.context.support.ClassPathXmlApplicationContext;

public class SpringELMethodInvocationExample {
    public static void main(String[] args) {
        ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext(
                "applicationContext.xml");
        try {
            Training training = (Training) context.getBean("training");
            System.out.println(training);
        } finally {
            context.close();
        }
    }
}

Output:

Total topics: 2, Java Topic: JavaThreads, has thread tutorial: true, first topic: JavaThreads, custom topics: [Spring Data, JavaThreads]

Spring EL in spring context XML

In this example, we achieve the above using spring context XML.

applicationContext.xml:

<?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"
	xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
	http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-2.5.xsd">

	<context:component-scan base-package="com.javarticles.spring" />

	<bean id="listOfTopics" class="com.javarticles.spring.ListOfTopics">
		<property name="topicsList">
			<list>
				<ref local="java" />
				<ref local="scala" />
			</list>
		</property>
	</bean>

	<bean id="java" class="com.javarticles.spring.Topic">
		<property name="name" value="JavaThreads" />
	</bean>

	<bean id="scala" class="com.javarticles.spring.Topic">
		<property name="name" value="ScalaFunctions" />
	</bean>

	<bean id="myTraining" class="com.javarticles.spring.Training">
		<property name="javaTopic" value="#{java.getName()}" />
		<property name="totalTopics" value="#{listOfTopics.getTopicsList().size()}" />
		<property name="hasThreadTutorial"
			value="#{java.getName().toUpperCase() == 'JavaThreads'.toUpperCase()}" />
		<property name="firstTopic" value="#{listOfTopics.getTopicsList()[0]}" />
		<property name="customTopics"
			value="#{T(java.util.Arrays).asList(new com.javarticles.spring.Topic('Spring Data'), listOfTopics.getTopicsList()[0])}" />
	</bean>
</beans>

SpringELMethodInvocationExample:

package com.javarticles.spring;

import org.springframework.context.support.ClassPathXmlApplicationContext;

public class SpringELMethodInvocationExample {
    public static void main(String[] args) {
        ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext(
                "applicationContext.xml");
        try {
            Training training = (Training) context.getBean("training");
            System.out.println(training);
            
            System.out.println(context.getBean("myTraining"));
        } finally {
            context.close();
        }
    }
}

Output:

Total topics: 2, Java Topic: JavaThreads, has thread tutorial: true, first topic: JavaThreads, custom topics: [Spring Data, JavaThreads]
Total topics: 2, Java Topic: JavaThreads, has thread tutorial: true, first topic: JavaThreads, custom topics: [Spring Data, JavaThreads]

Download the source code

This was an example about spring EL Method Invocation.

You can download the source code here: springELMethodInvocationExample.zip
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