CODEWITHSUNDEEP
javaspringtomcat
AfterWorkGuinness
AfterWorkGuinness

Reputation: 1850

Tomcat to run a service not web application

I want to use Tomcat to simply start a service, not a servlet.

I know Tomcat is a servlet container and not an application server, but this is the platform the architect has set for us to use.

I want to have a Java class executed as soon as Tomcat starts up which will load a class from the Spring context and call some method on it.

I'm thinking the best way to do this is to create a Listener which will load my bean from the Spring context using a ClassPathXmlApplicationContext and call the desired method on it.

Is there a better way of doing this ?

Upvotes: 1

Views: 624

Answers (2)

Luiggi Mendoza
Luiggi Mendoza

Reputation: 85779

You can take advantage of @PostConstruct annotation. This will execute a method after the bean is created and all the necessary resources have been injected in the bean. This is a sample:

@Service
public class MyBean {
    @PostConstruct
    public void init() {
        //construction logic here...
        //printing a message for demonstration purposes
        System.out.println("Bean is already created and resources have been injected!");
    }
}

To use @PostConstruct, take into account:

  • The bean must be instantiated by the container. This is: Spring, EJB, CDI, etc.
  • There must be only one method decorated by @PostConstruct.
  • This method must be public, return a void and have no arguments.

Using this approach, you don't need additional listeners in your application.

Upvotes: 1

Tom
Tom

Reputation: 3166

A lifecycle listener is the standard way to trigger application events based on some Tomcat action (usually Tomcat startup or shutdown). Since your goal is to have a class method invoked on Tomcat startup then it makes the most sense to put this invocation inside a listener. Whether that listener invokes a Spring bean or a simple POJO is arbitrary in terms of which method is better; the answer to that question should be determined by the needs of your application, e.g. will you need the Spring context to make other parts of you application easier to build?

To invoke a Spring bean within a listener you can use the following definitions in your web.xml:

<!-- The definition of the Root Spring Container shared by all Servlets and Filters -->
<context-param>
    <param-name>contextConfigLocation</param-name>
    <param-value>/WEB-INF/spring/applicationContext.xml</param-value>
</context-param>

<!-- Creates the Spring Container shared by all Servlets and Filters -->
<listener>
    <listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
</listener>

Upvotes: 1

Related Questions