Singleton Bean Scope

The singleton bean is termed as a stateless bean i.e. it doesn't carry any state with it. Only one instance of the object is created which is defined by this type of bean. One instance is created per container.All the other beans refer to this single instance of the bean. The scope of any bean is singleton by default but still if you want a single instance always , then you can define the scope property in the configuration file.

Syntax:

<!-- Defining singleton scope -->
<bean id="[bean-id]" class="[Class-name]" scope="singleton">
    <!-- Other configuration-->
</bean>

Example:

Welcome.java

public class Welcome {
   private String message;

   public void setMessage(String message){
      this.message  = message;
   }
   public void getMessage(){
      System.out.println("The message for you is: " + message);
   }
}

MainDemo.java

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class MainDemo {
   public static void main(String[] args) {
      ApplicationContext context = new ClassPathXmlApplicationContext("Beans.xml");

      Welcome ob1 = (Welcome) context.getBean("welcome");

      ob1.setMessage("Welcome in first object");
      ob1.getMessage();

      Welcome ob2 = (Welcome) context.getBean("welcome");
      ob2.getMessage();
   }
}

Beans.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-3.0.xsd">

   <bean id="welcome" class="Welcome" scope="singleton">
   </bean>
</beans>

When you try running this, the output will be as:

The message for you is: Welcome in first object
The message for you is: Welcome in first object

Prototype Bean Scope

The prototype bean is termed as a statefull bean i.e. it carries state with it. i.e the object members. You can create as many instances of this bean and with every new request associated with the bean a new instance is created. You can define the scope in the configuration file as prototype.

Syntax:

<!-- Defining singleton scope -->
<bean id="[bean-id]" class="[Class-name]" scope="prototype">
    <!-- Other configuration-->
</bean>

Example:

Welcome.java

public class Welcome {
   private String message;

   public void setMessage(String message){
      this.message  = message;
   }
   public void getMessage(){
      System.out.println("The message for you is: " + message);
   }
}

MainDemo.java

import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class MainDemo {
   public static void main(String[] args) {
      ApplicationContext context = new ClassPathXmlApplicationContext("Beans.xml");

      Welcome ob1 = (Welcome) context.getBean("welcome");

      ob1.setMessage("Welcome in first object");
      ob1.getMessage();

      Welcome ob2 = (Welcome) context.getBean("welcome");
      ob2.getMessage();
   }
}

Beans.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-3.0.xsd">

   <bean id="welcome" class="Welcome" scope="prototype">
   </bean>
</beans>

When you try running this, the output will be as:
The message for you is: Welcome in first object
null

This is because we pass the parameters for the second instance created for the bean.