Dependency Injection by Constructor Example

Dependency Injection by Constructor Example

Simple example to inject primitive and String-based values.

Steps as follows:

1. Create Employee.java POJO
2. Create ApplicationContext emaple
3. Create executable class called ExecuteEmployee.java

1. Create Employee.java POJO

package com;

import java.io.Serializable;

public class Employee implements Serializable {

   /**

   *

   */

   private static final long serialVersionUID = 1L;

   private int id;

   private String name;

   Employee(){} //default Constructor

   

   Employee(int id){ this.id = id; }

   

   Employee(String name){ this.name = name; }

   

   Employee(int id, String name){

     this.id = id;

     this.name = name;

   }

   void displayEmployee(){

     System.out.println("id | name : " + this.id + " | " + this.name);

   }

}

2. 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="employeeID" class="com.Employee">

<constructor-arg type="int" value="100"></constructor-arg>

</bean>

<bean id="employeeIDString" class="com.Employee">

<constructor-arg value="100"></constructor-arg>

</bean>

<bean id="employeeNameString" class="com.Employee">

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

</bean>

<bean id="employee" class="com.Employee">

<constructor-arg type="int" value="100"></constructor-arg>

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

</bean>

</beans>

3. Create ExecuteEmployee.java

package com;

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 ExecuteEmployee {

   /**

   * @param args

   */

   public static void main(String[] args) {

     ExecuteEmployee exEmployee = new ExecuteEmployee();

     exEmployee.doExecute();

   }

   private void doExecute(){

     

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

     BeanFactory beanFactory = new  XmlBeanFactory(resource);

     

     Employee employeeID = (Employee)beanFactory.getBean("employeeID");

     employeeID.displayEmployee();

     System.out.println("\nInjecting String-based values --> \n");

     Employee employeeIDString = (Employee)beanFactory.getBean("employeeIDString");

     employeeIDString.displayEmployee();

     System.out.println("--------------------------------- ");

     Employee employeeNameString = (Employee)beanFactory.getBean("employeeNameString");

     employeeNameString.displayEmployee();

     System.out.println("--------------------------------- ");

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

     employee.displayEmployee();

  }

}

Out put as follows:

Aug 26, 2013 8:48:21 AM

id | name : 100 | null

Injecting String-based values -->

id | name : 0 | 100

---------------------------------

id | name : 0 | Sanjeeva

---------------------------------

id | name : 100 | Sanjeeva