Spring Custom Scope Example
March 10, 2023
Scope interface to create custom scopes. The Scope interface is a strategy interface that allows for extending the standard scopes "singleton" and "prototype" of BeanFactory with custom further scopes, registered for a specific key. The Scope implementations are expected to be thread-safe.
In our example, we will create our custom scope as thread scope. Thread scope means a bean creation and destruction will be limited to a thread life cycle.
Create Custom Scope
Find the custom thread scope implementation class.CustomThreadScope.java
package com.concretepage;
import java.util.HashMap;
import java.util.Map;
import org.springframework.beans.factory.ObjectFactory;
import org.springframework.beans.factory.config.Scope;
public class CustomThreadScope implements Scope {
CustomThreadLocal customThreadLocal = new CustomThreadLocal();
@SuppressWarnings("rawtypes")
@Override
public Object get(String str, ObjectFactory objectFactory) {
System.out.println("getting object from scope.");
@SuppressWarnings("unchecked")
Map<String, Object> scope = (Map<String, Object>) customThreadLocal.get();
Object object = scope.get(str);
if (object == null) {
object = objectFactory.getObject();
scope.put(str, object);
}
return object;
}
@Override
public String getConversationId() {
return null;
}
@Override
public void registerDestructionCallback(String arg0, Runnable arg1) {
}
@Override
public Object remove(String str) {
Map<String, Object> scope = (Map<String, Object>) customThreadLocal.get();
return scope.remove(str);
}
@Override
public Object resolveContextualObject(String arg0) {
return null;
}
class CustomThreadLocal extends ThreadLocal {
protected Map<String, Object> initialValue() {
System.out.println("initialize ThreadLocal");
return new HashMap<String, Object>();
}
}
}
Register Custom Scope
We need to register our custom scope class with Spring container. We can do it in JavaConfig as well as in application XML.app-conf.xml
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:util="http://www.springframework.org/schema/util"
xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
http://www.springframework.org/schema/util http://www.springframework.org/schema/util/spring-util.xsd">
<bean class="org.springframework.beans.factory.config.CustomScopeConfigurer">
<property name="scopes">
<map>
<entry key="customThread">
<bean class="com.concretepage.CustomThreadScope"/>
</entry>
</map>
</property>
</bean>
<bean id="testA" class="com.concretepage.A" scope="customThread" />
</beans>
SpringTest.java
package com.concretepage;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
public class SpringTest {
public static void main(String[] args) {
ApplicationContext context = new ClassPathXmlApplicationContext("app-conf.xml");
context.getBean("testA");
}
}
getting object from scope. initialize ThreadLocal Bean A is initialized
ConfigurableBeanFactory beanFactory= new DefaultListableBeanFactory();
Scope threadScope= new CustomThreadScope();
beanFactory.registerScope("customThread", threadScope);
