Injecting inner beans in Spring

Similar to Java which provides defining inner class inside another class, Spring IOC provides defining a bean inside another bean.This will be useful when a bean is declared as property in another bean.

Let us see the inner bean in action

Lets say i have an Employee bean and employee has an address object declared as a field in Employee object.

Employee.java:

package com.ramesh.domain;

public class Employee {

 private int id;
 private String name;
 private long salary;
 private Address address;

 public int getId() {
  return id;
 }

 public void setId(int id) {
  this.id = id;
 }

 public String getName() {
  return name;
 }

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

 public long getSalary() {
  return salary;
 }

 public void setSalary(long salary) {
  this.salary = salary;
 }

 public Address getAddress() {
  return address;
 }

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

}

As shown above employee as a Address field.Lets see the Address bean

Address.java

package com.ramesh.domain;

public class Address {

 private String street;
 private String pinCode;
 private String city;

 public String getStreet() {
  return street;
 }

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

 public String getPinCode() {
  return pinCode;
 }

 public void setPinCode(String pinCode) {
  this.pinCode = pinCode;
 }

 public String getCity() {
  return city;
 }

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

}

Now configure the spring-context.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:mvc="http://www.springframework.org/schema/mvc"
 xmlns:context="http://www.springframework.org/schema/context"
 xsi:schemaLocation="
        http://www.springframework.org/schema/mvc http://www.springframework.org/schema/mvc/spring-mvc-3.0.xsd
        http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
        http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-3.0.xsd">


 <bean id="employee" class="com.ramesh.domain.Employee">
  <property name="id" value="844" />
  <property name="name" value="Ramesh M" />
  <property name="salary" value="85000" />
  <property name="address">
   <bean class="com.ramesh.domain.Address">
    <property name="street">
     <value>Embassy Golflinks Business Park Street</value>
    </property>
    <property name="city">
     <value>Bangalore</value>
    </property>
    <property name="pinCode">
     <value>560071</value>
    </property>
   </bean>
  </property>

 </bean>

</beans>


Since we completed the configuration lets test 

package com.ramesh;

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

import com.ramesh.domain.Employee;

public class MainApp {

 public static void main(String[] args) {
  ApplicationContext appContext = new ClassPathXmlApplicationContext(
    "spring-context.xml");
  Employee employee = (Employee) appContext.getBean("employee");

  // displaying employee name
  System.out.println(employee.getName());

  // displaying inner bean address details

  System.out.println(employee.getAddress().getStreet());

 }
}

The output:

INFO: Pre-instantiating singletons in org.springframework.beans.factory.support.DefaultListableBeanFactory@1b4fad5: defining beans [employee]; root of factory hierarchy
Ramesh M
Embassy Golflinks Business Park Street