In this article, you will learn about the @WebFilter annotation used Java web programming, with syntax, description and code examples.

The @WebFilter  annotation is used to declare a filter in a web application. The annotated class must extend the javax.servlet.Filter interface.

 

1. Syntax of @WebFilter annotation

@WebFilter(
    attribute1=value1,
    attribute2=value2,
    ...
)
public class TheFilter implements javax.servlet.Filter {
    // implements Filter's methods: init(), doFilter() and destroy()
}

 

2. Attributes of @WebFilter annotation

Name	Type	Required	Description
filterName	String	Optional	Name of the filter.
value or urlPatterns	String[]	Required	Specify one or more URL patterns to which the filter applies. Either of attribute can be used, but not both.
dispatcherTypes	DispatcherType[]	Optional	Specify types of dispatcher to which the filter applies. Default is javax.servlet.DispatcherType.REQUEST
servletNames	String[]	Optional	Specify names of servlets to which the filter applies.
displayName	String	Optional	Display name of the filter.
description	String	Optional	Description of the filter.
asyncSupported	boolean	Optional	Specify whether the filter supports asynchronous operation mode. Default is false.
initParams	WebInitParam[]	Optional	Specify one or more initialization parameters of the filter. Each parameter is specified by @WebInitParam annotation type.
smallIcon	String	Optional	Specify name of the small icon of the filter.
largeIcon	String	Optional	Specify name of the large icon of the filter.

 

3. Some @WebFilter Examples

The following example registers a filter for the URL pattern /admin: 

@WebFilter("/admin")
public class MyFilter implements Filter {

	@Override
	public void init(FilterConfig filterConfig) throws ServletException {
	}

	@Override
	public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
			throws IOException, ServletException {
	}
	
	@Override
	public void destroy() {
		
	}    
}

 

Apply a filter for all URLs: 

@WebFilter("/*")
public class MyFilter implements Filter {
    // implements Filter's methods here...
} 

 

Register a filter for a specific servlet:

@WebFilter(servletNames = "MyOwnServlet")
public class MyFilter implements Filter {
    // implements Filter's methods here...
} 

 

Register a filter for multiple servlets:

@WebFilter(servletNames = {"MyOwnServlet", "UploadServlet"})
public class MyFilter implements Filter {
    // implements Filter's methods here...
} 

 

Specify initialization parameters for the filter:

@WebFilter(
        urlPatterns = "/uploadFilter",
        initParams = @WebInitParam(name = "fileTypes", value = "doc;xls;zip;txt;jpg;png;gif")        
)
public class UploadFilter implements Filter {
    // implements Filter's methods here...
} 

 

Specify additional information for the filter:

@WebFilter(
        urlPatterns = "/admin/*",
        filterName = "AdminFilter",
        description = "Filter all admin URLs"        
)
public class MyFilter implements Filter {
    // implements Filter's methods here...
} 

 

Specify dispatcher types:

@WebFilter(
        urlPatterns = "/admin",
        dispatcherTypes = {DispatcherType.REQUEST, DispatcherType.FORWARD}
)
public class MyFilter implements Filter {
    // implements Filter's methods here...
}

That's how to use the @WebFilter annotation. I recommend you to read the book Head First Servlet and JSP to fully learn about Java servlet programming.

 

References:

• Annotation Type WebFilter (Javadoc)
• Interface Filter (Javadoc)

 

Related Java Filter Tutorials:

• @WebServlet annotation examples
• How to Create Java Servlet Filter
• How to modify HTTP response using Java Filter
• How to implement authentication filter for Java web application

 

Related Java Servlet Annotations:

• @WebServlet annotation
• @WebListener annotation
• @WebInitParam annotation
• @HandlesTypes annotation
• @MultipartConfig annotation
• @ServletSecurity, @HttpMethodContraint and @HttpConstraint annotations

 

Other Java Servlet Tutorials:

• Java Servlet Quick Start for beginners (XML)
• Java Servlet for beginners (annotations)
• Java Servlet and JSP Hello World Tutorial with Eclipse, Maven and Apache Tomcat
• Handling HTML form data with Java Servlet
• Java File Download Servlet Example