Question

My question is : from basic which are the necessary jars that should required in Spring and how could we configure Spring project ?

Answer 1

Go to Spring home page and download Spring (Here, i am using 2.5.x version)

After installing, put the following jar in your classpath

<SPRING_HOME>/dist/spring.jar

Here goes a single bean

package br.com.introducing.Hello;

public class Hello {

    private String message;

    // getter's and setter's

}

…

Write a single xml to configure your beans as follows

// app.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-2.5.xsd">
    <bean id="hello" class="br.com.introducing.Hello">
        <property name="message" value="What do you want ?"/>
    </bean>
</beans>

Put your app.xml in root classpath

And your psvm

public static void main(String [] args) {
    ApplicationContext appContext = new ClassPathXmlApplicationContext("app.xml");

    Hello hello = (Hello) appContext.getBean("hello");

    hello.getMessage(); // outputs What do you want ?
}

UPDATE

What is the role of the applicationContext.xml

When using getBean method, it behaves like a Factory pattern. Something like

public class ApplicationContext {

    Map wiredBeans = new HashMap();

    public static Object getBean(String beanName) {
        return wiredBeans.get(beanName);
    }

}

As said by Spring in Action book

It is a general-purpose factory, creating and dipensing many types of bean.

But, There is more

• Allows you load files
• You can publish events
• It supports i18n (i18n stands for internationalization)

Suppose here goes messages.properties (root of the classpath)

// messages.properties

messsageCode=What do you want ?

To enable i18n, You must define a bean called messageSource to get advantage of our resource, as follows

<?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-2.5.xsd">
    <bean id="messageSource" class="org.springframework.context.support.ResourceBundleMessageSource">
        <property name="basename" value="messages"/>
    </bean>
</beans>

Now, you can use it

appContext.getMessage("messsageCode", null, null); // outputs What do you want ?

Usually, we do not need to define all of our beans in xml file. You can use annotations (Additional settings needed to enable component scanning) instead of xml, Something like

package br.com.introducing.Hello;

@Component
public class Hello {

    private String message;

    // getter's and setter's

}

Component annotation says:

Spring, i am a general-purpose bean which can be retrieved through application context

A good resource about Spring is either Spring in Action book or Spring documentation

Advice: read carefully