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

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

About the Author:

Nam Ha Minh is certified Java programmer (SCJP and SCWCD). He began programming with Java back in the days of Java 1.4 and has been passionate about it ever since. You can connect with him on Facebook and watch his Java videos on YouTube.