Constructor Injection with Dependent-Object

Constructor-Injection-with-Dependent-Object

If there is HAS-A relationship between the classes, first we create the instance of dependent object and then pass it as an argument of the main class constructor.

    e.g. Employee HAS-A Address, so Address class object will be the dependent.

<bean id="addressBean" class="Address">

<constructor-arg value="126B, Pubudu Uyana"></constructor-arg>

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

<constructor-arg value="Western Province"></constructor-arg>

<constructor-arg value="Sri Lanka"></constructor-arg>

</bean>

<bean id="employeeBean" class="Employee">

<constructor-arg type="int" value="100123"></constructor-arg>

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

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

<constructor-arg><ref bean="addressBean"/> </constructor-arg>

</bean>

Step 01 : Create Address.java

import java.io.Serializable;

public class Address implements Serializable {

   private static final long serialVersionUID = 1L;

   private String number;

   private String city;

   private String province;

   private String country;

   Address(String number, String city, String province, String country){

     super();

     this.number = number;

     this.city = city;

     this.province = province;

     this.country = country;

   }

   String displayAddressInfo(){

     return this.number + ", " + this.city + ", " + this.province + ", " + this.country;

   }

}

Step 02 : Create Address.java

import java.io.Serializable;

public class Employee implements Serializable {

    private static final long serialVersionUID = 1L;

    private int id;

    private String firstname;

    private String lastname;

    private Address address;

 

    public Employee(int id, String fname, String lname, Address address) {

      super();

      this.id = id;

      this.firstname = fname;

      this.lastname = lname;

      this.address = address;

    }

    void displayEmployee(){

      System.out.println("Employee ID : " + id);

      System.out.println("Employee First Name : " + firstname);

      System.out.println("Employee Last Name : " + lastname);

      System.out.println("Employee Address : " + address.displayAddressInfo());

    }

}

Step 03 : Create 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"

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

<bean id="addressBean" class="Address">

<constructor-arg value="126B, Pubudu Uyana"></constructor-arg>

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

<constructor-arg value="Western Province"></constructor-arg>

<constructor-arg value="Sri Lanka"></constructor-arg>

</bean>

<bean id="employeeBean" class="Employee">

<constructor-arg type="int" value="100123"></constructor-arg>

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

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

<constructor-arg><ref bean="addressBean"/></constructor-arg>

</bean>

</beans>

Step 04 : Create DisplayInformation.java

import org.springframework.beans.factory.BeanFactory;

import org.springframework.beans.factory.xml.XmlBeanFactory;

import org.springframework.core.io.ClassPathResource;

import org.springframework.core.io.Resource;

public class DisplayInformation {

/**

* @param args

*/

   public static void main(String[] args) {

     DisplayInformation displayInformation = new     DisplayInformation();

     displayInformation.doExecute();

   }

   private void doExecute(){

     Resource resource = new ClassPathResource("ApplicationContext.xml");

     BeanFactory beanFactory = new XmlBeanFactory(resource);

     Employee employee = (Employee)beanFactory.getBean("employeeBean");

     employee.displayEmployee();

   }

}

Out Put as follows :

Employee ID : 100123

Employee First Name : Sanjeeva

Employee Last Name : Pathirana

Employee Address : 126B, Pubudu Uyana, Piliyandala, Western Province, Sri Lanka