Java Servlet @HandlesTypes Annotation Example

Details: Written by Nam Ha Minh; Last Updated on 26 June 2019 | Print Email

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This post helps you understand how to use the @HandlesTypes annotation in the Java Servlet API.

You know, the @HandlesTypes annotation is used to annotate a class that implements javax.servlet.ServletContainerInitializer interface. It declares the class types in which an implementation of ServletContainerInitializer is interested.

Syntax of @HandlesTypes annotation:

@HandlesTypes({Class1, Class2, Class3, ...})
public class AnInitializer implements ServletContainerInitializer {

	public void onStartup(Set<Class<?>> classes, ServletContext context)
			throws ServletException {
		// initialization code...
	}
}

The Servlet container will find and pass a Set of application classes that extend, implement, or have been annotated with the class types listed by the @HandlesTypes annotation as the first argument of the onStartup() method. If the container did not find any matching classes, it will pass null.

Attributes of @HandlesTypes annotation:

Name	Type	Required	Description
value	java.lang.Class[]	Required	An array of class types in which the implementation of ServletContainerInitializer is interested.

Examples of @HandlesTypes annotation:

The following code example shows a typical usage of the @HandlesTypes annotation:

@HandlesTypes({
	javax.servlet.http.HttpServlet.class,
	javax.servlet.Filter.class
})
public class AppInitializer implements ServletContainerInitializer {

	@Override
	public void onStartup(Set<Class<?>> classes, ServletContext context)
			throws ServletException {
		// initialization code...
	}
}

In the above code, we specify two class types: javax.servlet.http.HttpServlet and javax.servlet.Filter. The Servlet container will pass a Set containing implementation classes of the listed types to the method onStartup().

Related Java Servlet Annotations:

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