Example of error handling for Java web applications

error-web.xml

<servlet>
        <servlet-name>NotFoundErrorHandler</servlet-name>
        <servlet-class>NotFoundErrorHandler</servlet-class>
</servlet>
<servlet>
        <servlet-name>ErrorHandler</servlet-name>
        <servlet-class>ErrorHandler</servlet-class>
</servlet>
<!-- servlet mappings -->
<servlet-mapping>
        <servlet-name>NotFoundErrorHandler</servlet-name>
        <url-pattern>/notfound</url-pattern>
</servlet-mapping>
<servlet-mapping>
        <servlet-name>ErrorHandler</servlet-name>
        <url-pattern>/error</url-pattern>
</servlet-mapping>
<!-- error pages -->
<error-page>
        <error-code>500</error-code>
        <location>/error</location>
</error-page>
<error-page>
        <exception-type>java.lang.Exception</exception-type>
        <location>/error</location>
</error-page>
<error-page>
        <error-code>404</error-code>
        <location>/notfound</location>
</error-page>

ErrorHandler.java

@WebServlet("/error")
public class ErrorHandler extends HttpServlet {
    private static final long serialVersionUID = 1L;
 
    protected void doGet(HttpServletRequest request,
            HttpServletResponse response) throws ServletException, IOException {
        processError(request, response);
    }
 
    protected void doPost(HttpServletRequest request,
            HttpServletResponse response) throws ServletException, IOException {
        processError(request, response);
    }
 
    private void processError(HttpServletRequest request,
            HttpServletResponse response) throws IOException {
        // do something with your error and show the error page
    }
}