Constructor Dependency Injection with Array of String

In some scenarios, we may need to inject an array of strings to an object.

Consider the example where Person has hobbies

In this case, we can use Array of Strings which stores the hobbies

Let us see the same in spring through Constructor Dependency Injection

Create a class called Person

It contains 3 attributes id,name and hobbies where hobbies is an array of String.
It also contains showHobbies() method to display the hobbies injected to the person object.

  1. package com.kb.di;
  2.  
  3. import java.util.Map;
  4. import java.util.Map.Entry;
  5.  
  6. public class Person {
  7.     private int id;
  8.     private String name;
  9.     private String[] hobbies;
  10.  
  11.     public Person(int id, String name, String[] hobbies) {
  12.         this.id = id;
  13.         this.name = name;
  14.         this.hobbies = hobbies;
  15.     }
  16.  
  17.     public void showHobbies() {
  18.         for (int i = 0; i < hobbies.length; i++) {
  19.             System.out.println(hobbies[i]);
  20.         }
  21.  
  22.     }
  23.  
  24. }
package com.kb.di;

import java.util.Map;
import java.util.Map.Entry;

public class Person {
	private int id;
	private String name;
	private String[] hobbies;

	public Person(int id, String name, String[] hobbies) {
		this.id = id;
		this.name = name;
		this.hobbies = hobbies;
	}

	public void showHobbies() {
		for (int i = 0; i < hobbies.length; i++) {
			System.out.println(hobbies[i]);
		}

	}

}

Create a spring bean definition file

In this file, we used < constructor-arg > tag with < array > to define the hobbies
< array > tag is used to inject the hobbies defined as array of strings in the Person class.

  1. <?xml version="1.0" encoding="UTF-8"?>
  2. <beans xmlns="http://www.springframework.org/schema/beans"
  3.     xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  4.     xmlns:p="http://www.springframework.org/schema/p"
  5.     xsi:schemaLocation="http://www.springframework.org/schema/beans
  6.        http://www.springframework.org/schema/beans/spring-beans-3.2.xsd">
  7.  
  8.  <bean id="person" class="com.kb.di.Person">  
  9.     <constructor-arg value="1" type="int"/>
  10.     <constructor-arg value="Raj"/>
  11.     <constructor-arg>
  12.     <array>
  13.     <value>Playing cricket</value>
  14.     <value>Coding</value>
  15.     <value>Reading books</value>
  16.     </array>
  17.     </constructor-arg>
  18.  </bean>
  19. </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">  
	<constructor-arg value="1" type="int"/>
	<constructor-arg value="Raj"/> 
	<constructor-arg>
	<array>
	<value>Playing cricket</value>
	<value>Coding</value>
	<value>Reading books</value>
	</array>
	</constructor-arg> 
 </bean>
</beans>

Create a pom.xml file

  1. <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  2.   xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
  3.   <modelVersion>4.0.0</modelVersion>
  4.  
  5.   <groupId>Spring</groupId>
  6.   <artifactId>SpringCore</artifactId>
  7.   <version>0.0.1-SNAPSHOT</version>
  8.   <packaging>jar</packaging>
  9.  
  10.   <name>SpringCore</name>
  11.   <url>http://maven.apache.org</url>
  12.  
  13.   <properties>
  14.     <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
  15.   </properties>
  16.  
  17.   <dependencies>
  18.   <dependency>
  19.     <groupId>org.springframework</groupId>
  20.     <artifactId>spring-core</artifactId>
  21.     <version>4.2.4.RELEASE</version>
  22. </dependency>
  23.   <dependency>
  24.     <groupId>org.springframework</groupId>
  25.     <artifactId>spring-context</artifactId>
  26.     <version>4.2.4.RELEASE</version>
  27. </dependency>
  28.  
  29.     <dependency>
  30.       <groupId>junit</groupId>
  31.       <artifactId>junit</artifactId>
  32.       <version>3.8.1</version>
  33.       <scope>test</scope>
  34.     </dependency>
  35.   </dependencies>
  36. </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 ConstructorDI class

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

  1. package com.kb.di;
  2.  
  3. import org.springframework.context.ApplicationContext;
  4. import org.springframework.context.support.ClassPathXmlApplicationContext;
  5.  
  6. public class ConstructorDI {
  7.    
  8.     public static void main(String[] args) {
  9.         ApplicationContext applicationContext=new ClassPathXmlApplicationContext("beans.xml");  
  10.         Person person = (Person)applicationContext.getBean("person");
  11.         person.showHobbies();
  12.    
  13.     }
  14.  
  15. }
package com.kb.di;

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

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

}

Run the ConstructorDI class and see the output as below

Download this project SpringDIWithArrayOfString.zip

About the Author

Raj
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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