JAVA EE: Spring Prototype scope

Tuesday, 7 August 2018

Spring Prototype scope

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Introduction

In the Spring Framework, bean scope defines how the Spring IoC container creates, manages, and provides instances of beans. While Spring defaults to singleton scope (where one shared instance is reused), the prototype scope ensures that every single request for a bean produces a completely new, independent bean instance.

The Core Essence of Prototype Scope

Fresh Instance Per Request: Every call to context.getBean() or every injection into another bean creates a brand-new object with its own state.
Ideal for Stateful Beans: When objects hold user-specific data, shopping carts, or transaction session data, prototype prevents state leakage across threads.
Lifecycle Responsibility: Spring creates, configures, and assembles prototype beans, but does not manage their full destruction lifecycle. The client code is responsible for cleaning up resources.

Step-by-Step Configuration in Spring XML

Setting up a prototype bean in XML is done simply by configuring the scope="prototype" attribute on the <bean> tag:

1. Bean Definition in applicationContext.xml

<bean id="customerService" 
      class="com.ram.service.CustomerService" 
      scope="prototype">
    <property name="message" value="Hello Prototype!" />
</bean>

2. Verifying Independent Instances in Java

ApplicationContext context = new ClassPathXmlApplicationContext("applicationContext.xml");

CustomerService obj1 = (CustomerService) context.getBean("customerService");
CustomerService obj2 = (CustomerService) context.getBean("customerService");

// Output will be false: two distinct memory references
System.out.println("Are beans identical? " + (obj1 == obj2));

Key Takeaway

Use prototype scope when your beans hold state that cannot be safely shared across concurrent execution threads. Remember that Spring hands over the prototype instance to the caller, meaning your code must handle any necessary resource disposal or cleanup.

Recommended Spring Scope Tutorials from Ram N Java

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Spring Prototype scope

pom.xml

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0%20http://maven.apache.org/maven-v4_0_0.xsd">

    <modelVersion>4.0.0</modelVersion>

    <groupId>com.ram.core</groupId>

    <artifactId>SpringDemo</artifactId>

    <packaging>jar</packaging>

    <version>1.0-SNAPSHOT</version>

    <name>SpringDemo</name>

    <url>http://maven.apache.org</url>

    <properties>

        <spring.version>5.0.2.RELEASE</spring.version>

    </properties>

    <dependencies>

        <dependency>

            <groupId>junit</groupId>

            <artifactId>junit</artifactId>

            <version>3.8.1</version>

            <scope>test</scope>

        </dependency>

        <!-- Spring 5 dependencies -->

        <dependency>

            <groupId>org.springframework</groupId>

            <artifactId>spring-core</artifactId>

            <version>${spring.version}</version>

        </dependency>

        <dependency>

            <groupId>org.springframework</groupId>

            <artifactId>spring-context</artifactId>

            <version>${spring.version}</version>

        </dependency>

    </dependencies>

</project>

Employee.java

package com.ram.model;

public class Employee

{

    private String name;

    public String getName()

    {

        return name;

    }

    public void setName(String name)

    {

        this.name = name;

    }

    @Override

    public String toString()

    {

        return "Employee [name=" + name + "]";

    }

}

applicationContext.xml

<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-4.3.xsd">

    <bean id="employee" class="com.ram.model.Employee" scope="prototype">

    </bean>

</beans>

App.java

package com.ram.core;

import org.springframework.context.ApplicationContext;

import org.springframework.context.support.ClassPathXmlApplicationContext;

import com.ram.model.Employee;

public class App

{

    public static void main(String[] args)

    {

        ApplicationContext context = new ClassPathXmlApplicationContext(

                "applicationContext.xml");

        System.out.println("-------------------------------------------");

        Employee employee1 = (Employee) context.getBean("employee");

        employee1.setName("John");

        System.out.println(

                "Got employee object from the ApplicationContext(Spring Container)");

        System.out.println(employee1);

        System.out.println("-------------------------------------------");

        Employee employee2 = (Employee) context.getBean("employee");

        System.out.println(

                "Got employee object from the ApplicationContext(Spring Container)");

        System.out.println(employee2);

    }

}

Output

Jul 21, 2018 9:02:35 AM org.springframework.context.support.AbstractApplicationContext prepareRefresh

INFO: Refreshing org.springframework.context.support.ClassPathXmlApplicationContext@5b37e0d2: startup date [Sat Jul 21 09:02:35 IST 2018]; root of context hierarchy

Jul 21, 2018 9:02:35 AM org.springframework.beans.factory.xml.XmlBeanDefinitionReader loadBeanDefinitions

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

-------------------------------------------

Got employee object from the ApplicationContext(Spring Container)

Employee [name=John]

-------------------------------------------

Got employee object from the ApplicationContext(Spring Container)

Employee [name=null]