Quick to the point introduction to Spring Framework

The definition of bean contains the configuration metadata information which is needed for the container to know:

• How to create a bean
• Bean's lifecycle details
• Bean's dependencies

Spring Configuration Metadata:

To create Spring configuration metadata, this metadata tells Spring what beans “Java classes” you need to be instantiated in Spring container. From the format Spring IoC container is completely decoupled in which this metadata configuration is written. There are three methods to provide configuration metadata to the Spring Container:

• XML based configuration file.
• Annotation-based configuration
• Java-based configuration

XML Configuration:

Example: class FirstBean

package pack1;
 
public class FirstBean {
 
    private String cName;
 
    public String getName() {
        return cName;
    }
 
    public void setName(String cName) {
        this.cName = cName;
    }
 
    @Override
    public String toString() {
        return "FirstBean [Cutomer Name: " + cName + "]";
    }
} 

Create class SecondBean:

package pack1;
 
public class SecondBean {
 
    private FirstBean fBean;
 
    public FirstBean getFirstBean() {
        return fBean;
    }
 
    public void setFirstBean(FirstBean fBean) {
        this.fBean = fBean;
    }
 
    @Override
    public String toString() {
        return "SecondBean [fBean: " + fBean + "]";
    }   
}

Create the configuration xml file:

<?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="firstBean" class="pack1.FirstBean">
        <property name="name" value="Nimrit" />
    </bean>
 
    <bean id="secondBean" class="pack1.SecondBean">
                <property name="fBean" ref="fBean" />
        </bean>
</beans>

Create class SampleTest:

package pack1;
 
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
 
import pack1.FirstBean;
import pack1.SecondBean;
 
public class SampleTest 
{
    public static void main( String[] args )
    {
        ApplicationContext ctxXML = new ClassPathXmlApplicationContext("Bean.xml");
        SecondBean secondBean = (SecondBean) ctxXML.getBean("secondBean");
 
        System.out.println( secondBean);
    }
}

Now when you execute this test you will get below result

Result:

SecondBean [fBean=FirstBean [name=Suman]]

Annotation-Based Configuration:

Example: class FirstBean

• @Component(value=“fBean2″) : this method which enable Spring to find this bean when scanning and instantiate a bean named “fBean2“
• @Value(value=“AnnotationBean”) : this equal to fbean2.setName(“AnnotationBean”);

package pack1;
 
import org.springframework.beans.factory.annotation.Value;
import org.springframework.stereotype.Component;
 
@Component(value="fBean2")
public class FirstBean {
 
    private String cName;
 
    public String getName() {
        return cName;
    }
 
    @Value(value="Suman")
    public void setName(String cName) {
        this.name = cName;
    }
 
    @Override
    public String toString() {
        return "FirstBean [name=" + cName + "]";
    }
 }

Create class SecondBean:

• @Component(value=“secondBean”) : this method which enable Spring to find this bean when scanning and instantiate a bean named “secondBean”
• @Autowired @Qalifier(“fBean2″): this equal to secondBean.setFirstBean(fbean2)

package pack1;
 
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.stereotype.Component;
 
@Component(value="secondBean")
public class SecondBean {
 
    private FirstBean fBean;
 
    public FirstBean getFirstBean() {
        return fBean;
    }
 
    @Autowired
    @Qualifier("fBean2")
    public void setFirstBean(FirstBean fBean) {
        this.fBean = fBean;
    }
 
    @Override
    public String toString() {
        return "SecondBean [fBean=" + fBean + "]";
    }
 }

Create the configuration xml file as: BeanAnnotation.xml, to enable annotations:

<?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:context="http://www.springframework.org/schema/context"    
        xsi:schemaLocation="http://www.springframework.org/schema/beans
            http://www.springframework.org/schema/beans/spring-beans.xsd
            http://www.springframework.org/schema/context
            http://www.springframework.org/schema/context/spring-context.xsd">
      <context:component-scan base-package="pack1"/>
      <!-- The use of <context:component-scan> implicitly enables the functionality of <context:annotation-config> -->
 <bean id="firstBean" class="pack1.FirstBean">
        <property name="name" value="Nimrit" />
    </bean>
    <bean id="secondBean" class="pack1.SecondBean">
                <property name="fBean" ref="fBean" />
        </bean>
</beans>

Create class SampleTest:

package pack1;
 
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import pack1.SecondBean;
 
public class SampleTest 
{
    public static void main( String[] args )
    {
 
        ApplicationContext ctxAnnotation = new ClassPathXmlApplicationContext("BeanAnnotation.xml");
       SecondBean sBean  = (SecondBean) ctxAnnotation.getBean("sBean");
         System.out.println( sBean);
     }
}

When you execute above test, you will get the result as shown below

SecondBean [fBean=FirstBean [name=Nimrit]]

Java-Based Configuration:

Example: class FirstBean

package pack1;
 
import org.springframework.beans.factory.annotation.Value;
 
public class FirstBean {
 
    private String cName;
 
    public String getName() {
        return cName;
    }
 
    @Value(value="Nimrit")
    public void setName(String cName) {
        this.cName = cName;
    }
 
    @Override
    public String toString() {
        return "FirstBean [name=" + cName + "]";
    }
 }

Create class SecondBean:

package pack1;
 
import org.springframework.beans.factory.annotation.Autowired;
 
public class SecondBean {
 
    private FirstBean fBean;
 
    public FirstBean getFirstBean() {
        return fBean;
    }
 
    @Autowired
    public void setFirstBean(FirstBean fBean) {
        this.fBean = fBean;
    }
 
    @Override
    public String toString() {
        return "SecondBean [fBean=" + fBean + "]";
    }
 }

Create Java configuration file:

package pack1;
 
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import pack1.SecondBean;
import pack1.FirstBean;
 
@Configuration
public class ConfigFile {
 
    @Bean
    public FirstBean fBean(){
        return  new FirstBean();
    }
 
    @Bean(name = "config")
    public SecondBean sBean(){
        return new SecondBean();
    }
}

Create class SampleTest

package pack1;
 
import org.springframework.context.ApplicationContext;
import org.springframework.context.annotation.AnnotationConfigApplicationContext;
import pack1.SecondBean;
import pack1.ConfigFile;
 
public class App 
{
    public static void main( String[] args )
    {
 
ApplicationContext ctxJavaConfig = new AnnotationConfigApplicationContext(ConfigFile.class);
SecondBean sBean = (SecondBean) ctxJavaConfig.getBean("config");
System.out.println( sBean);
     }
}

When you execute above test case, we will get 

Result:

SecondBean [fBean=FirstBean [name=Nimrit]]