Setter Dependency Injection with List of String example

In some scenarios, we may need to inject a list of string to an object rather than just one string value.

In such cases, let us see how we inject a list of string through a setter injection.

Consider the example where one Person knows multiple languages

In this case, we are required to inject list of string to person object.

So Let us see the same in spring through Setter Dependency Injection

Create a class called Person

It contains 3 attributes id,name and languages where languages is a list of string

It contains 3 setter methods one corresponding to each attribute.

It also contains showPersonLanguages() method to display the list of languages that we have injected to the person object.

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package com.kb.di;
 
import java.util.List;
 
public class Person {
    private int id;
    private String name;
    private List<String> languages;
 
    public void showPersonLanguages() {
        for (String language : languages) {
            System.out.println(language);
        }
    }
 
    public void setId(int id) {
        this.id = id;
    }
 
    public void setName(String name) {
        this.name = name;
    }
 
    public void setLanguages(List<String> languages) {
        this.languages = languages;
    }
}
package com.kb.di;

import java.util.List;

public class Person {
	private int id;
	private String name;
	private List<String> languages;

	public void showPersonLanguages() {
		for (String language : languages) {
			System.out.println(language);
		}
	}

	public void setId(int id) {
		this.id = id;
	}

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

	public void setLanguages(List<String> languages) {
		this.languages = languages;
	}
}

Create a spring bean definition file

In this file, we used < property > tag with < list > to define the list of string.

< value > tag is used to inject each value of the list

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<?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:p="http://www.springframework.org/schema/p"
    xsi:schemaLocation="http://www.springframework.org/schema/beans
        http://www.springframework.org/schema/beans/spring-beans-3.2.xsd">
 
 
    <bean id="person" class="com.kb.di.Person">
        <property name="id" value="1"></property>
        <property name="name" value="Raj"></property>
        <property name="languages">
            <list>
                <value>English</value>
                <value>Spnaish</value>
                <value>German</value>
                <value>French</value>
            </list>
        </property>
 
    </bean>
</beans>
<?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:p="http://www.springframework.org/schema/p"
	xsi:schemaLocation="http://www.springframework.org/schema/beans
        http://www.springframework.org/schema/beans/spring-beans-3.2.xsd">


	<bean id="person" class="com.kb.di.Person">
		<property name="id" value="1"></property>
		<property name="name" value="Raj"></property>
		<property name="languages">
			<list>
				<value>English</value>
				<value>Spnaish</value>
				<value>German</value>
				<value>French</value>
			</list>
		</property>

	</bean>
</beans>

Create a pom.xml file

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<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>Spring</groupId>
  <artifactId>SpringCore</artifactId>
  <version>0.0.1-SNAPSHOT</version>
  <packaging>jar</packaging>
 
  <name>SpringCore</name>
  <url>http://maven.apache.org</url>
 
  <properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
  </properties>
 
  <dependencies>
  <dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-core</artifactId>
    <version>4.2.4.RELEASE</version>
</dependency>
  <dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-context</artifactId>
    <version>4.2.4.RELEASE</version>
</dependency>
  
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>3.8.1</version>
      <scope>test</scope>
    </dependency>
  </dependencies>
</project>
<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>Spring</groupId>
  <artifactId>SpringCore</artifactId>
  <version>0.0.1-SNAPSHOT</version>
  <packaging>jar</packaging>

  <name>SpringCore</name>
  <url>http://maven.apache.org</url>

  <properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
  </properties>

  <dependencies>
  <dependency>
	<groupId>org.springframework</groupId>
	<artifactId>spring-core</artifactId>
	<version>4.2.4.RELEASE</version>
</dependency>
  <dependency>
	<groupId>org.springframework</groupId>
	<artifactId>spring-context</artifactId>
	<version>4.2.4.RELEASE</version>
</dependency>
  
    <dependency>
      <groupId>junit</groupId>
      <artifactId>junit</artifactId>
      <version>3.8.1</version>
      <scope>test</scope>
    </dependency>
  </dependencies>
</project>

Create a SetterDI class

This class loads the spring beans using application context and calls the person class method to display the languages.

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package com.kb.di;
 
import org.springframework.beans.factory.BeanFactory;
import org.springframework.beans.factory.xml.XmlBeanFactory;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import org.springframework.core.io.ClassPathResource;
import org.springframework.core.io.Resource;
 
public class SetterDI{
    
    public static void main(String[] args) {
        ApplicationContext applicationContext=new ClassPathXmlApplicationContext("beans.xml");  
        Person person = (Person)applicationContext.getBean("person");
        person. showPersonLanguages ();
        
    }
}
package com.kb.di;

import org.springframework.beans.factory.BeanFactory;
import org.springframework.beans.factory.xml.XmlBeanFactory;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import org.springframework.core.io.ClassPathResource;
import org.springframework.core.io.Resource;

public class SetterDI{
	
	public static void main(String[] args) {
        ApplicationContext applicationContext=new ClassPathXmlApplicationContext("beans.xml");  
        Person person = (Person)applicationContext.getBean("person");
        person. showPersonLanguages ();
        
	}
}

Run the SetterDI class and see the output as below

Download this project SetterDIWithListOfString.zip

About the Author

Karibasappa G C (KB)
Founder of javainsimpleway.com
I love Java and open source technologies and very much passionate about software development.
I like to share my knowledge with others especially on technology 🙂
I have given all the examples as simple as possible to understand for the beginners.
All the code posted on my blog is developed,compiled and tested in my development environment.
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