Spring Constructor Injection Using List With Dependent Object

Spring Constructor Injection Using List With Dependent Object

In spring we can inject values to Collection by constructor injection. We can use three elements in <constructor-arg> element, it can be list, set and map etc.

In this example we are going to use List<Address> to store Players multiple address, similarly what we have done in previous tutorial for List<String> but here object is user defined i.e Address class.

Info  :  List can contain duplicate object.

Here Address class contains property such as city and country with constructors and also having toString() method.

Address.java

package com.TheTechMatin.Entity;

public class Address {

private String city;

private String country;

public Address() {}

public Address(String city, String country) {

     this.city = city;

     this.country = country;

}

@Override

public String toString() {

     return "Address [city=" + city + ",country=" + country+"]";

}

}

Here players class contains fullName, role, board and List<Address> with constructor and with displayInfo() method which is responsible to display Players information in convenient way.

Players.class

package com.TheTechMatin.Entity;

import java.util.List;

public class Players {

     private String fullName;

     private String role;

     private String board;

     private List<Address> playersAddress;

     public Players() {

     }

     public Players(String fullName, String role, String board, List<Address> playersAddress) {

          this.fullName = fullName;

          this.role = role;

          this.board = board;

          this.playersAddress = playersAddress;

     }

     public void displayInfo() {

          System.out.println("Name :"+fullName +" Role :"+role+" Board :"+board);

          int count = 0;

          for(Address ad : playersAddress) {

              count++;

              System.out.println("Addresss "+count+" :"+ad);

          }

     }

}

This applicationContext.xml file is a configuration file in which we have injected the values to a particular fields via constructor injection using <constructor-arg> element and using the things which we have already seen in our last tutorials.

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:p="http://www.springframework.org/schema/p" 

    xsi:schemaLocation="http://www.springframework.org/schema/beans  

http://www.springframework.org/schema/beans/spring-beans-3.0.xsd">

     <bean id="addressOfIndia" class="com.TheTechMatin.Entity.Address">

      <constructor-arg value="Jam Nagar"></constructor-arg>

      <constructor-arg value="India"></constructor-arg>

     </bean>

    

     <bean id="addressOfEngland" class="com.TheTechMatin.Entity.Address">

       <constructor-arg value="London"></constructor-arg>

      <constructor-arg value="England"></constructor-arg>

     </bean>

    

     <bean id="player" class="com.TheTechMatin.Entity.Players">

          <constructor-arg value="Sir Ravindra Jadeja"></constructor-arg>

          <constructor-arg value="All Rounder"></constructor-arg>

          <constructor-arg value="BCCI"></constructor-arg>

          <constructor-arg>

           <list>

            <ref bean="addressOfIndia"/>

            <ref bean="addressOfEngland"/>

           </list>

          </constructor-arg>

     </bean>

</beans>

In TestApp.java class first we are loading applicationContext.xml file which is responsible for configurations, then printing a message after that getting bean form config file and then calling displayInfo() method and at the lass closing the context

TestApp.java

package com.TheTechMatin.Entity;

import org.springframework.context.support.ClassPathXmlApplicationContext;

public class TestApp {

     public static void main(String[] args) {

         

          //load the configuration file

          ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml");

         

          //just printing the message

          System.out.println("Hello Welcome To Sping Constructor Injection!");

         

          //get the bean

          Players player = context.getBean(Players.class);

         

          //call method to display info

          player.displayInfo();

         

          //close the context

          context.close();

     }

}

On execution of main class the following output will be displayed.

Hello Welcome To Sping Constructor Injection!

Name :Sir Ravindra Jadeja Role :All Rounder Board :BCCI

Addresss 1 :Address [city=Jam Nagar,country=India]

Addresss 2 :Address [city=London,country=England]

Tested On Eclipse 2019-06

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