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How to use Java based configuration in Spring Framework without using XML based configuration ?.

A simple application to demonstrate how to use Java based configuration in Spring Framework without using XML based configuration.

The following steps / classes are taken for this simple application to work.

1. A simple POJO bean as Address
package com.hubberspot.spring.configuration;


public class Address {

 private String street;
 private String city;
 private String state;

 public Address() {

 }


 public String getStreet() {
  return street;
 }


 public void setStreet(String street) {
  this.street = street;
 }


 public String getCity() {
  return city;
 }


 public void setCity(String city) {
  this.city = city;
 }


 public String getState() {
  return state;
 }


 public void setState(String state) {
  this.state = state;
 }
 
 public void initialize() {
  System.out.println("Initialization of Address ... ");
 }
 
 public void destroy() {
  System.out.println("Destruction of Address ... ");
 }

}




2. A simple POJO bean as Employee having being injected by Address object.
package com.hubberspot.spring.configuration;

import javax.inject.Inject;

// Create a POJO class Employee which has a 
// Address Object reference as instance variable
public class Employee {

 private String name;
 private int age;

 @Inject
 private Address address;

 public Employee() {

 }

 public String getName() {
  return name;
 }

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

 public int getAge() {
  return age;
 }

 public void setAge(int age) {
  this.age = age;
 }

 public Address getAddress() {
  return address;
 }

 public void setAddress(Address address) {
  this.address = address;
 }

 public void init() {
  System.out.println("Initialization of Employee ... ");
 }

 public void clean() {
  System.out.println("Destruction of Employee ... ");
 }

}



3. Java Based Configuration class replacing Spring Configuration XML.
package com.hubberspot.spring.configuration;

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

// @Configuration makes this Java class as configuration
// for the Spring Framework. It declares two beans here 
// instead of providing it in spring configuration file
// we can provide it in Java class

@Configuration
public class EmployeeConfiguration {

 // @Bean registers Address as a Spring bean

 @Bean(initMethod="initialize", destroyMethod= "destroy")
 public Address address() {

  Address address = new Address();
  address.setStreet("Town Hall Street");
  address.setCity("Pune");
  address.setState("Maharashtra");
  return address;
 }

 // @Bean registers Employee as a Spring bean

 @Bean(initMethod="init", destroyMethod= "clean")
 public Employee employee() {
  Employee employee = new Employee();
  employee.setName("Jonty");
  employee.setAge(28);
  employee.setAddress(address());
  return employee;
 }

}



4. A simple Spring xml file having components scan tag


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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:context="http://www.springframework.org/schema/context"
 xsi:schemaLocation="http://www.springframework.org/schema/beans
        http://www.springframework.org/schema/beans/spring-beans-3.1.xsd
        http://www.springframework.org/schema/context
        http://www.springframework.org/schema/context/spring-context-3.1.xsd">

<!-- This tag helps Spring to automatically scan annotations based components -->
 <context:component-scan base-package="com.hubberspot.spring.configuration">
 </context:component-scan>

</beans>


5. Test class for running the example

package com.hubberspot.spring.configuration;

import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import org.springframework.context.support.AbstractApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class Test {

 public static void main(String[] args) {

  // ApplicationContext is a Spring interface which 
  // provides with the configuration for an application. 
  // It provides us with all the methods that BeanFactory 
  // provides. It loads the file resources in a older 
  // and generic manner. It helps us to publish events to the
  // listener registered to it. It also provides quick support
  // for internationalization. It provides us with the object 
  // requested, it reads the configuration file and provides
  // us with the necessary object required.
  // Since we are using Java based configuration method so instead
  // of using concrete implementation of ApplicationContext
  // which is ClassPathXmlApplicationContext we are using 
  // AnnotationConfigApplicationContext to load and register
  // annotated configuration classes. Instead of xml we provide
  // name of the java configuration Class object (instance of this Class)

  AbstractApplicationContext context = 
    new AnnotationConfigApplicationContext(EmployeeConfiguration.class);

  context.registerShutdownHook();

  // In order to get a object instantiated for a particular bean 
  // we call getBean() method of ClassPathXmlApplicationContext
  // passing it the id for which the object is to be needed. 
  // Here getBean() returns an Object. We need to cast it back 
  // to the Employee object. Without implementing new keyword we 
  // have injected object of Employee just by reading an xml 
  // configuration file.
  Employee employee = (Employee)context.getBean("employee");

  if(employee.getAddress()==null){
   System.out.println("The Employee Name : " + employee.getName());
   System.out.println("The Employee Age : " + employee.getAge());
   System.out.println("The Employee Address : " + "is not provided");
  }
  else{
   System.out.println("The Employee Name : " + employee.getName());
   System.out.println("The Employee Age : " + employee.getAge());
   System.out.println("The Employee Address : " +   
     employee.getAddress().getStreet() + " " +
     employee.getAddress().getCity() + " " +
     employee.getAddress().getState());
  }
 }
}



Note : To run above example application classpath must include all Spring Jars and CGLIB jar [cglib-nodep-x.x.x.jar]

Output of the program :


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