Spring Useful Resources

Custom Events in Spring

There are number of steps to be taken to write and publish your own custom events. Follow the instructions given in this chapter to write, publish and handle Custom Spring Events.

Steps	Description
1	Create a Maven project with a name spring, groupid com.tutorialspoint, artifactid spring and create a package com.tutorialspoint under the src folder in the created project.
2	Create an event class, CustomEvent by extending ApplicationEvent. This class must define a default constructor which should inherit constructor from ApplicationEvent class.
3	Once your event class is defined, you can publish it from any class, let us say EventClassPublisher which implements ApplicationEventPublisherAware. You will also need to declare this class in XML configuration file as a bean so that the container can identify the bean as an event publisher because it implements the ApplicationEventPublisherAware interface.
4	A published event can be handled in a class, let us say EventClassHandler which implements ApplicationListener interface and implements onApplicationEvent method for the custom event.
5	Create beans configuration file Beans.xml under the src folder and a MainApp class which will work as Spring application.
6	The final step is to create the content of all the Java files and Bean Configuration file and run the application as explained below.

CustomEvent.java

 package com.tutorialspoint; import org.springframework.context.ApplicationEvent; public class CustomEvent extends ApplicationEvent{ public CustomEvent(Object source) { super(source); } public String toString(){ return "My Custom Event"; } }

CustomEventPublisher.java

 package com.tutorialspoint; import org.springframework.context.ApplicationEventPublisher; import org.springframework.context.ApplicationEventPublisherAware; public class CustomEventPublisher implements ApplicationEventPublisherAware { private ApplicationEventPublisher publisher; public void setApplicationEventPublisher (ApplicationEventPublisher publisher) { this.publisher = publisher; } public void publish() { CustomEvent ce = new CustomEvent(this); publisher.publishEvent(ce); } }

CustomEventHandler.java

 package com.tutorialspoint; import org.springframework.context.ApplicationListener; public class CustomEventHandler implements ApplicationListener<CustomEvent> { public void onApplicationEvent(CustomEvent event) { System.out.println(event.toString()); } }

MainApp.java

 package com.tutorialspoint; import org.springframework.context.ConfigurableApplicationContext; import org.springframework.context.support.ClassPathXmlApplicationContext; public class MainApp { public static void main(String[] args) { ConfigurableApplicationContext context = new ClassPathXmlApplicationContext("Beans.xml"); CustomEventPublisher cvp = (CustomEventPublisher) context.getBean("customEventPublisher"); cvp.publish(); cvp.publish(); } }

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 = "customEventHandler" class = "com.tutorialspoint.CustomEventHandler"/> <bean id = "customEventPublisher" class = "com.tutorialspoint.CustomEventPublisher"/> </beans>

Output

Once you are done creating the source and bean configuration files, let us run the application. If everything is fine with your application, it will print the following message −

 My Custom Event My Custom Event

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