Spring Tutorials

We can inject the dependency by constructor. The subelement of is used for constructor injection. Constructor-based DI is accomplished by the container invoking a constructor with a number of arguments, each representing a dependency. Calling a static factory method with specific arguments to construct the bean is nearly equivalent, and this discussion treats arguments to a constructor and to a static factory method similarly.

1. Spring 3.0
2. Eclipse IDE
3. JDK 1.6

Example

Let us have working Eclipse IDE in place and follow the following steps to create a Spring application:

Step1. Now you create a simple Java Project using Eclipse IDE. Follow the option File -> New -> Project and finally select Java Project wizard from the wizard list. Now name your project as ConstructorBasedDi using the wizard window as given below.

Step2. Now add spring jar in your project, To do this, right click on your project name ConstructorBasedDi and then follow the following option available in context menu: Build Path -> Configure Build Path to display the Java Build Path window as given below. There are some jar files required to run this application, To load the jar files in eclipse IDE, Right click on your project - Build Path - Add external archives - select all the required jar files - finish.

1. antlr-runtime-3.0.1
2. org.springframework.aop-3.1.0
3. org.springframework.asm-3.1.0.
4. org.springframework.aspects-3.1.0.
5. org.springframework.beans-3.1.0.
6. org.springframework.context.support-3.1.0.
7. org.springframework.context-3.1.0.
8. org.springframework.core-3.1.0.
9. org.springframework.expression-3.1.0.
10. commons-logging-1.1.1

Step3. Now you create simply java file with any name. First we need to create a package with any name like com.r4r. To do this, Right click on src in package explorer section and follow the option : New -> Package. and then Right click on package(com.r4r) - New - class - Write the class name e.g. Demo - finish. Write the following code:

package com.r4r;
public class Demo {
	private Message msg;
	public Demo(Message msg) {
	System.out.println("Constructor Message." );
	this.msg = msg;
	}
	public void show() 
	{
	msg.showmsg();
	}
}

Step4. Now you create another dependent java class named Message.java.

package com.r4r;
public class Message {
public Message(){
System.out.println("Message constructor." );
} 
public void showmsg() 
	{
System.out.println("Inside show message." );
   } 
}

Step5. Now create the xml file click on src- new -file -give the file name like Beans.xml then finish.

<?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="demo" class="com.r4r.Demo">
<constructor-arg ref="msg"/>
</bean>
<bean id="msg" class="com.r4r.Message">
</bean>
</beans>

Step6.Now Create the java Main class (MainApp.java).

package com.r4r;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
public class MainApp {
public static void main(String[] args) {
ApplicationContext context = 
	new ClassPathXmlApplicationContext("Beans.xml");
Demo d = (Demo) context.getBean("demo");
d.show();
} }

Now run the Application you see the following output