Spring Framework - Inversion Of Control - Basic Example

Here, we are going to learn the simple steps to create the first spring application. To run this application, we are not using any IDE. We are simply using the command prompt. Let's see the simple steps to create the spring application

• create the class
• create the xml file to provide the values
• create the test class
• Load the spring jar files
• Run the test class

Steps to create spring application 

Let's see the 5 steps to create the first spring application.

1) Create Java class

This is the simple java bean class containing the name property only.

public class Student {
    private String name;

    public String getName() {
        return name;
    }

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

    public void displayInfo() {
        System.out.println("Hello: " + name);
    }
}

 

This is simple bean class, containing only one property name with its getters and setters method. This class contains one extra method named displayInfo() that prints the student name by the hello message.

2) Create the xml file

In case of myeclipse IDE, you don't need to create the xml file as myeclipse does this for yourselves. Open the applicationContext.xml file, and write the following code:

<?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:p="http://www.springframework.org/schema/p"
    xsi:schemaLocation="http://www.springframework.org/schema/beans
               http://www.springframework.org/schema/beans/spring-beans-3.0.xsd">

<bean id="studentbean" class="com.javatpoint.Student">
<property name="name" value="Vimal Jaiswal"></property>
</bean>

</beans>  

The bean element is used to define the bean for the given class. The property subelement of bean specifies the property of the Student class named name. The value specified in the property element will be set in the Student class object by the IOC container.

3) Create the test class

Create the java class e.g. Test. Here we are getting the object of Student class from the IOC container using the getBean() method of BeanFactory. Let's see the code of test class.

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

public class Test {
    public static void main(String[] args) {
        Resource resource = new ClassPathResource("applicationContext.xml");
        BeanFactory factory = new XmlBeanFactory(resource);

        Student student = (Student) factory.getBean("studentbean");
        student.displayInfo();
    }
}

The Resource object represents the information of applicationContext.xml file. The Resource is the interface and the ClassPathResource is the implementation class of the Reource interface. The BeanFactory is responsible to return the bean. The XmlBeanFactory is the implementation class of the BeanFactory. There are many methods in the BeanFactory interface. One method is getBean(), which returns the object of the associated class.

4) Load the jar files required for spring framework

There are mainly three jar files required to run this application.

• org.springframework.core-3.0.1.RELEASE-A
• com.springsource.org.apache.commons.logging-1.1.1
• org.springframework.beans-3.0.1.RELEASE-A

For the future use, You can download the required jar files for spring core application.

Link: Download the core jar files for spring

5) Running the code

You will have the following directory structure after writing the code files:
C:\Users\Rajeev\Desktop\fsp>dir /b

applicationContext.xml
Student.java
Test.java 

Next you only have to fire the "javac" and "java" commands as shown below.

Following pointers show commands in blue and output in red.

• C:\Users\Rajeev\Desktop\fsp>javac -classpath "D:\Workspace\Java Library\Spring Core 3.0.1\org.springframework.beans-3.0.1.RELEASE-A.jar;.;D:\Workspace\Java Library\Spring Core 3.0.1\org.springframework.core-3.0.1.RELEASE-A.jar" Test.java

• C:\Users\Rajeev\Desktop\fsp>java -classpath "D:\Workspace\Java Library\Spring Core 3.0.1\org.springframework.beans-3.0.1.RELEASE-A.jar;.;D:\Workspace\Java Library\Spring Core 3.0.1\org.springframework.core-3.0.1.RELEASE-A.jar;D:\Workspace\Java Library\Spring Core 3.0.1\com.springsource.org.apache.commons.logging-1.1.1.jar" Test

• Oct 01, 2018 11:21:34 PM org.springframework.beans.factory.xml.XmlBeanDefinitionReader loadBeanDefinitions

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

• Hello: Vimal Jaiswal

6) Setting up this code in Eclipse

a) Create a normal Java project.

b) Include the JARs in the 'build path'.

c) Create the code files (.java and applicationContext.xml)

d) Run the 'Test.java' file as 'Java Application' from the context menu.

Shown below is the directory structure, code and output in Eclipse:

References: 

• https://www.javatpoint.com/steps-to-create-spring-application