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Java Example of Spring Dependency Injection

05 Jul

This tutorial uses the following:

    • Eclipse IDE
    • Spring Jars
    • commons-logging-api-1.1.jar
  1. Make a new Java Project in Eclipse.
  2. Add the following jars to its classpath:
    • commons-logging-api-1.1.jar
    • org.springframework.core-3.0.2.jar
    • org.springframework.beans-3.0.2.jar

The Spring jars can be taken from the dist folder of the expanded zip file. Here you have to include the two jars one for core and other for beans. Commons-logging is used for logging purpose.

  • Make a new class – Person.java. It is a 100% Java bean and has the proper getters and setters.
package com.spring.ioc.beans;

public class Person {

	private String name;

	private String address;

	/**
	 * @return the name
	 */
	public String getName() {
		return name;
	}

	/**
	 * @param name the name to set
	 */
	public void setName(String name) {
		this.name = name;
	}

	/**
	 * @return the address
	 */
	public String getAddress() {
		return address;
	}

	/**
	 * @param address the address to set
	 */
	public void setAddress(String address) {
		this.address = address;
	}

}

  • Make an XML file and name it context.xml and save it in the src folder.  This file contains all the meta information needed for bean creation. Here the bean id is person and class has the full qualified name of the class. The “name” property of the class Person is populated with the value Mac.

<?xml version="1.0" encoding="UTF-8"?>
xmlns="http://www.springframework.org/schema/beans"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:p="http://www.springframework.org/schema/p"
	xsi:schemaLocation="
       http://www.springframework.org/schema/beans
       http://www.springframework.org/schema/beans/spring-beans.xsd">
	<bean id="person" class="com.spring.ioc.beans.Person">
	<property name="name" value="Mac"></property>
	</bean>
</beans>

  • Make another class named Main.java.  Here an object of XmlBeanFactory loads the configurations from contect.xml file. Also its constructor takes an argument of ClassPathResource.
  • To get a bean from XmlBeanFactory object use its reference type to invoke the method getBean(<bean id>) and it will return the bean as defined in the spring context file.  The Object it returns is of type Object so you do have to cast it to the correct type.
package com.spring.ioc.main;

import org.springframework.beans.factory.xml.XmlBeanFactory;
import org.springframework.core.io.ClassPathResource;

import com.spring.ioc.beans.Person;

/**
 * @author hgupta
 *
 */
public class Main {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		XmlBeanFactory beanFactory = new XmlBeanFactory(new ClassPathResource(
				"context.xml"));
		Person person = (Person) beanFactory.getBean("person");
		System.out.println(person.getName());
	}

}

  • Run the Main class as Java Application and you will see the following output: The output is the name of the person which you configured in the xml file.

Output:

May 27, 2010 6:54:04 PM org.springframework.beans.factory.xml.XmlBeanDefinitionReader loadBeanDefinitions

INFO: Loading XML bean definitions from class path resource [context.xml]

Mac

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Posted by on July 5, 2010 in Java, Spring

 

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