Spring List Examples

A List object is something we often rely on in our classes and there are times when we may need to configure it directly in our bean configurations.

In this article we will see several examples of list element. We will create an empty list, a proper list, a list with a mix of different value types and finally a list which enforces the value type.

We will also see how to create a list object using ListFactoryBean and util:list.

So let’s get start with the examples but first a bit about the setup.

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>3.2.3.RELEASE</spring.version>
	</properties>

</project>

About the List Examples

Our examples contain two central beans Tutorial and Topic. A tutorial is composed of list of topics. It also has a name attribute to describe the tutorial.

Topic:

package com.javarticles.spring;

public class Topic {
    private String name;

    public String getName() {
        return name;
    }

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

Tutorial:

package com.javarticles.spring;

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

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

    public String getName() {
        return name;
    }

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

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

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

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

ListFactoryBean Example

In this example, we will use spring provided ListFactoryBean, a FactoryBean implementation, to create a java.util.List instance initialized with values provided by sourceList property. The targetListClass property defines the actual implementation type of the List. Once we have defined out list factory, we just need to point the list property topicsList to the bean reference topicListFactory.

listFactoryApplicationContext.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" 
	xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">

	<bean id="topicListUsingFactory" class="com.javarticles.spring.Tutorial">
		<property name="name" value="Get Topics using ListFactoryBean"></property>
		<property name="topicsList" ref="topicListFactory" />
	</bean>

	<bean id="topicListFactory"
		class="org.springframework.beans.factory.config.ListFactoryBean">
		<property name="sourceList">
			<list>
				<ref local="javaCore" />
				<ref local="scalaBasics" />
			</list>
		</property>
		<property name="targetListClass">
			<value>java.util.LinkedList</value>
		</property>
	</bean>
	<bean id="javaCore" class="com.javarticles.spring.Topic">
		<property name="name" value="JavaCore" />
	</bean>
	<bean id="scalaBasics" class="com.javarticles.spring.Topic">
		<property name="name" value="ScalaBasics" />
	</bean>
</beans>

SpringListFactoryBeanExample:

package com.javarticles.spring;

import org.springframework.context.support.ClassPathXmlApplicationContext;

public class SpringListFactoryBeanExample {
    public static void main(String[] args) {
        ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext(
                "listFactoryApplicationContext.xml");
        try {
            Tutorial tutorial = (Tutorial) context.getBean("topicListUsingFactory");
            System.out.println(tutorial);
        } finally {
            context.close();
        }
    }
}

Output:

Get Topics using ListFactoryBean[JavaCore, ScalaBasics]

util:list Example

Instead of explicitly relying on ListFactoryBean, you can use the spring utility schema which has an easy way of creating list using <util:list> element. You can define the exact type of List using the list-class attribute on the element. Let’s do the above example using util:list.

listFactoryApplicationContext.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:util="http://www.springframework.org/schema/util"
	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-2.0.xsd">

	<bean id="topicListUsingFactory" class="com.javarticles.spring.Tutorial">
		<property name="name" value="Get Topics using ListFactoryBean"></property>
		<property name="topicsList" ref="topicListFactory" />
	</bean>

	<bean id="topicListFactory"
		class="org.springframework.beans.factory.config.ListFactoryBean">
		<property name="sourceList">
			<list>
				<ref local="javaCore" />
				<ref local="scalaBasics" />
			</list>
		</property>
		<property name="targetListClass">
			<value>java.util.LinkedList</value>
		</property>
	</bean>

	<bean id="topicListUsingUtilList" class="com.javarticles.spring.Tutorial">
		<property name="name" value="Get Topics using Util:List"></property>
		<property name="topicsList" ref="topicListUtil" />
	</bean>

	<util:list id="topicListUtil" list-class="java.util.LinkedList">
		<ref local="javaCore" />
		<ref local="scalaBasics" />
	</util:list>

	<bean id="javaCore" class="com.javarticles.spring.Topic">
		<property name="name" value="JavaCore" />
	</bean>
	<bean id="scalaBasics" class="com.javarticles.spring.Topic">
		<property name="name" value="ScalaBasics" />
	</bean>
</beans>

SpringListFactoryBeanExample:

package com.javarticles.spring;

import org.springframework.context.support.ClassPathXmlApplicationContext;

public class SpringListFactoryBeanExample {
    public static void main(String[] args) {
        ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext(
                "listFactoryApplicationContext.xml");
        try {
            Tutorial tutorial = (Tutorial) context.getBean("topicListUsingFactory");
            System.out.println(tutorial);
            
            tutorial = (Tutorial) context.getBean("topicListUsingUtilList");
            System.out.println(tutorial);
        } finally {
            context.close();
        }
    }
}

Output:

Get Topics using ListFactoryBean[JavaCore, ScalaBasics]
Get Topics using Util:List[JavaCore, ScalaBasics]

Set Empty List

We can also directly create the list using collection element <list>. Let’s start with an empty list. You just need to include empty <list> element without any values.

emptyListApplicationContext.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"
	xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">

	<bean id="emptyList" class="com.javarticles.spring.Tutorial">
		<property name="name" value="Empty List"/>
		<property name="topicsList">
			<list>
			</list>
		</property>
	</bean>
</beans>

SpringEmptyListExample:

package com.javarticles.spring;

import org.springframework.context.support.ClassPathXmlApplicationContext;

public class SpringEmptyListExample {
    public static void main(String[] args) {
        ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext(
                "emptyListApplicationContext.xml");
        try {
            Tutorial tutorial = (Tutorial) context.getBean("emptyList");
            System.out.println(tutorial);
        } finally {
            context.close();
        }
    }
}

Output:

Empty List[]

Inject List Using Spring list Element

Let’s inject a proper list using spring’s <list> element. The list element contains two values which refer to Topic beans javaCore and scalaBasics.

listApplicationContext.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"
	xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">

	<bean id="onlyTopicList" class="com.javarticles.spring.Tutorial">
		<property name="name" value="Proper List Example"/>
		<property name="topicsList">
			<list>
				<ref local="javaCore" />
				<ref local="scalaBasics" />
			</list>
		</property>
	</bean>
		
	<bean id="javaCore" class="com.javarticles.spring.Topic">
		<property name="name" value="JavaCore" />
	</bean>
	
	<bean id="scalaBasics" class="com.javarticles.spring.Topic">
		<property name="name" value="ScalaBasics" />
	</bean>	
</beans>

SpringListExample:

package com.javarticles.spring;

import org.springframework.context.support.ClassPathXmlApplicationContext;

public class SpringListExample {
    public static void main(String[] args) {
        ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext(
                "listApplicationContext.xml");
        try {
            Tutorial tutorial = (Tutorial) context.getBean("onlyTopicList");
            System.out.println(tutorial);
        } finally {
            context.close();
        }
    }
}

Output:

Proper List Example[JavaCore, ScalaBasics]

List With Mixed Value Types

In this example, we will create a list of which contains a mix of references and individual values.
Our bean mixedTypeTopicList contains Topic bean, a string value, a string value which is a bean ID and a list containing another set of mixed values.

listApplicationContext.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"
	xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">

	<bean id="onlyTopicList" class="com.javarticles.spring.Tutorial">
		<property name="name" value="Proper List Example"/>
		<property name="topicsList">
			<list>
				<ref local="javaCore" />
				<ref local="scalaBasics" />
			</list>
		</property>
	</bean>
		
	<bean id="javaCore" class="com.javarticles.spring.Topic">
		<property name="name" value="JavaCore" />
	</bean>
	
	<bean id="scalaBasics" class="com.javarticles.spring.Topic">
		<property name="name" value="ScalaBasics" />
	</bean>	
	
	<bean id="mixedTypeTopicList" class="com.javarticles.spring.Tutorial">
		<property name="name" value="Mixed List Example"/>
		<property name="topicsList">
			<list>
				<ref local="javaCore" />
				<value>Concurrency</value>
				<idref local="scalaBasics" />
				<list>
					<ref local="android" />
					<idref local="spring" />
				</list>
			</list>
		</property>
	</bean>

	<bean id="spring" class="com.javarticles.spring.Topic">
		<property name="name" value="Spring" />
	</bean>
	<bean id="android" class="com.javarticles.spring.Topic">
		<property name="name" value="Android" />
	</bean>	
	
</beans>

SpringListExample:

package com.javarticles.spring;

import org.springframework.context.support.ClassPathXmlApplicationContext;

public class SpringListExample {
    public static void main(String[] args) {
        ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext(
                "listApplicationContext.xml");
        try {
            Tutorial tutorial = (Tutorial) context.getBean("onlyTopicList");
            System.out.println(tutorial);
            
            tutorial = (Tutorial) context.getBean("mixedTypeTopicList");
            System.out.println(tutorial);
        } finally {
            context.close();
        }
    }
}

Output:

Proper List Example[JavaCore, ScalaBasics]
Mixed List Example[JavaCore, Concurrency, scalaBasics, [Android, spring]]

Enforce List Value Type

We can also enforce list’s value type using value-type attribute. We have added a new bean topicTypeList to our configuration, the value-typecom.javarticles.spring.Topic which means the list will accept only values of type Topic.

listApplicationContext.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"
	xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">

	<bean id="onlyTopicList" class="com.javarticles.spring.Tutorial">
		<property name="name" value="Proper List Example"/>
		<property name="topicsList">
			<list>
				<ref local="javaCore" />
				<ref local="scalaBasics" />
			</list>
		</property>
	</bean>
		
	<bean id="javaCore" class="com.javarticles.spring.Topic">
		<property name="name" value="JavaCore" />
	</bean>
	
	<bean id="scalaBasics" class="com.javarticles.spring.Topic">
		<property name="name" value="ScalaBasics" />
	</bean>	
	
	<bean id="mixedTypeTopicList" class="com.javarticles.spring.Tutorial">
		<property name="name" value="Mixed List Example"/>
		<property name="topicsList">
			<list>
				<ref local="javaCore" />
				<value>Concurrency</value>
				<idref local="scalaBasics" />
				<list>
					<ref local="android" />
					<idref local="spring" />
				</list>
			</list>
		</property>
	</bean>

	<bean id="spring" class="com.javarticles.spring.Topic">
		<property name="name" value="Spring" />
	</bean>
	<bean id="android" class="com.javarticles.spring.Topic">
		<property name="name" value="Android" />
	</bean>
	
	<bean id="topicTypeList" class="com.javarticles.spring.Tutorial">
		<property name="name" value="Enforce value-type List Example"/>
		<property name="topicsList">
			<list value-type="com.javarticles.spring.Topic">
				<ref local="javaCore" />
				<ref local="scalaBasics" />
			</list>
		</property>
	</bean>
	
</beans>

SpringListExample:

package com.javarticles.spring;

import org.springframework.context.support.ClassPathXmlApplicationContext;

public class SpringListExample {
    public static void main(String[] args) {
        ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext(
                "listApplicationContext.xml");
        try {
            Tutorial tutorial = (Tutorial) context.getBean("onlyTopicList");
            System.out.println(tutorial);
            
            tutorial = (Tutorial) context.getBean("mixedTypeTopicList");
            System.out.println(tutorial);
            
            tutorial = (Tutorial) context.getBean("topicTypeList");
            System.out.println(tutorial);
        } finally {
            context.close();
        }
    }
}

Output:

Proper List Example[JavaCore, ScalaBasics]
Mixed List Example[JavaCore, Concurrency, scalaBasics, [Android, spring]]
Enforce value-type List Example[JavaCore, ScalaBasics]

Download the source code

This was an example about spring list element and spring’s ListFactoryBean. You can download the source code here: springListExample.zip