Question

I have come across a scenario as below:

MyBean – Defined in XML Configuration.

I need to inject MyBean into multiple threads.
But my requirements is:
1) The reference retrieved in two different threads should be different
2) But I should get the same reference irrespective how many times I retrieve bean from single thread.

Eg :

Thread1 {

    run() {
        MyBean obj1 = ctx.getBean("MyBean");
        ......
        ......
        MyBean obj2 = ctx.getBean("MyBean");
    }
}

Thread2 {

    run(){
        MyBean obj3 = ctx.getBean("MyBean");
    }
}

So Basically obj1 == obj2 but obj1 != obj3

Answer 1

You can use the custom scope named SimpleThreadScope.

From the Spring documentation :

As of Spring 3.0, a thread scope is available, but is not registered
by default. For more information, see the documentation for
SimpleThreadScope. For instructions on how to register this or
any other custom scope, see Section 3.5.5.2, “Using a custom
scope”.

Here an example of how to register the SimpleThreadScope scope :

Scope threadScope = new SimpleThreadScope();
beanFactory.registerScope("thread", threadScope);

Then, you’ll be able to use it in your bean’s definition :

<bean id="foo" class="foo.Bar" scope="thread">

You can also do the Scope registration declaratively :

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

    <bean class="org.springframework.beans.factory.config.CustomScopeConfigurer">
        <property name="scopes">
            <map>
                <entry key="thread">
                    <bean class="org.springframework.context.support.SimpleThreadScope"/>
                </entry>
            </map>
        </property>
    </bean>

    <bean id="foo" class="foo.Bar" scope="thread">
        <property name="name" value="bar"/>
    </bean>

</beans>