Spring: Referring a bean from other bean

In any application, it is common that one bean refer other beans in its implementation. For example, take two classes Author, Book.

Author: Stores author firstName, lastName, dateOfBirth, country

Book: title, noOfPages, price, isbn, Author

Book class refer Author instance to store author details. Lets us implement this scenario using Spring IOC.

        <bean id="osho" class="com.sample.pojo.Author">
  <property name="firstName" value="Chandra Mohan" />
  <property name="lastName" value="Jain" />
  <property name="dateOfBirth" value="11 December 1931" />
  <property name="country" value="India" />
 </bean>

 <bean id="book1" class="com.sample.pojo.Book">
  <property name="title" value="Vedanta An Art of Dying" />
  <property name="noOfPages" value="164" />
  <property name="price" value="90" />
  <property name="isbn" value="8184192045" />
  <property name="author" ref="osho" />
 </bean>

Following are the bean definitions.

package com.sample.pojo;

public class Author {
 private String firstName;
 private String lastName;
 private String dateOfBirth;
 private String country;

 public String getFirstName() {
  return firstName;
 }

 public void setFirstName(String firstName) {
  this.firstName = firstName;
 }

 public String getLastName() {
  return lastName;
 }

 public void setLastName(String lastName) {
  this.lastName = lastName;
 }

 public String getDateOfBirth() {
  return dateOfBirth;
 }

 public void setDateOfBirth(String dateOfBirth) {
  this.dateOfBirth = dateOfBirth;
 }

 public String getCountry() {
  return country;
 }

 public void setCountry(String country) {
  this.country = country;
 }

 @Override
 public String toString() {
  StringBuilder builder = new StringBuilder();
  builder.append("Author [firstName=").append(firstName).append(", lastName=").append(lastName)
    .append(", dateOfBirth=").append(dateOfBirth).append(", country=").append(country).append("]");
  return builder.toString();
 }

}

package com.sample.pojo;

public class Book {
 private String title;
 private int noOfPages;
 private float price;
 private String isbn;
 private Author author;

 public String getTitle() {
  return title;
 }

 public void setTitle(String title) {
  this.title = title;
 }

 public int getNoOfPages() {
  return noOfPages;
 }

 public void setNoOfPages(int noOfPages) {
  this.noOfPages = noOfPages;
 }

 public float getPrice() {
  return price;
 }

 public void setPrice(float price) {
  this.price = price;
 }

 public String getIsbn() {
  return isbn;
 }

 public void setIsbn(String isbn) {
  this.isbn = isbn;
 }

 public Author getAuthor() {
  return author;
 }

 public void setAuthor(Author author) {
  this.author = author;
 }

 @Override
 public String toString() {
  StringBuilder builder = new StringBuilder();
  builder.append("Book [title=").append(title).append(", noOfPages=").append(noOfPages).append(", price=")
    .append(price).append(", isbn=").append(isbn).append(", author=").append(author).append("]");
  return builder.toString();
 }

}

Following is the configuration file.

myConfiguration.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.xsd">

 <bean id="osho" class="com.sample.pojo.Author">
  <property name="firstName" value="Chandra Mohan" />
  <property name="lastName" value="Jain" />
  <property name="dateOfBirth" value="11 December 1931" />
  <property name="country" value="India" />
 </bean>

 <bean id="book1" class="com.sample.pojo.Book">
  <property name="title" value="Vedanta An Art of Dying" />
  <property name="noOfPages" value="164" />
  <property name="price" value="90" />
  <property name="isbn" value="8184192045" />
  <property name="author" ref="osho" />
 </bean>

</beans>

As you see the definition of bean book1, the property "author" refers to "osho", that means it points to the bean with id "osho".

         <bean id="book1" class="com.sample.pojo.Book">

                 <property name="title" value="Vedanta An Art of Dying" />

                 <property name="noOfPages" value="164" />

                 <property name="price" value="90" />

                 <property name="isbn" value="8184192045" />

                 <property name="author" ref="osho" />

         </bean>

package com.sample.test;

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

import com.sample.pojo.Book;

public class HelloWorld {
 public static void main(String args[]) {
  ApplicationContext context = new ClassPathXmlApplicationContext(new String[] { "myConfiguration.xml" });

  Book book = context.getBean(Book.class);

  System.out.println(book);

  ((ClassPathXmlApplicationContext) context).close();
 }
}

Run HelloWorld.java, you can able to see following output.

Book [title=Vedanta An Art of Dying, noOfPages=164, price=90.0, isbn=8184192045, author=Author [firstName=Chandra Mohan, lastName=Jain, dateOfBirth=11 December 1931, country=India]]

        

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