Spring MVC - HandlerInterceptor Examples

Using HandlerInterceptorAdapter

import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.method.HandlerMethod;
import org.springframework.web.servlet.handler.HandlerInterceptorAdapter;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class LoginInterceptor extends HandlerInterceptorAdapter {
    @Override
    public boolean preHandle (HttpServletRequest request,
                              HttpServletResponse response,
                              Object handler) throws Exception {
        RequestMapping rm = ((HandlerMethod) handler).getMethodAnnotation(
                            RequestMapping.class);

        boolean alreadyLoggedIn = request.getSession()
                                         .getAttribute("user") != null;
        boolean loginPageRequested = rm != null && rm.value().length > 0 && "login".equals(
                            rm.value()[0]);


        if (alreadyLoggedIn && loginPageRequested) {
            response.sendRedirect(request.getContextPath() + "/app/main-age");
            return false;
        } else if (!alreadyLoggedIn && !loginPageRequested) {
            response.sendRedirect(request.getContextPath() + "/login");
            return false;
        }

        return true;
    }
}

Original Post

This HandlerInterceptor implementation tries to retrieve TimeZone from LocaleContextResolver, if it's null the request is redirected to a JavaScript page to get time zone information from the client.

package com.logicbig.example;

import org.springframework.web.servlet.handler.HandlerInterceptorAdapter;
import org.springframework.web.servlet.support.RequestContextUtils;

import javax.servlet.RequestDispatcher;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.util.TimeZone;

public class TzRedirectInterceptor extends HandlerInterceptorAdapter {

    @Override
    public boolean preHandle (HttpServletRequest request,
                              HttpServletResponse response,
                              Object handler) throws Exception {

        TimeZone tz = RequestContextUtils.getTimeZone(request);

        if (tz == null) {
            System.out.println("Forwarding to js to get timezone offset");
            request.setAttribute("requestedUrl", request.getRequestURI());
            RequestDispatcher dispatcher = request.getRequestDispatcher("/tzHandler");
            dispatcher.forward(request, response);
            return false;
        }

        return true;
    }
}

    @RequestMapping("/tzHandler")
    public String handle () {
        return "tzJsPage";
    }

src\main\webapp\WEB-INF\views\tzJsPage.jsp:

<%@ page language="java"
    contentType="text/html; charset=ISO-8859-1"
    pageEncoding="ISO-8859-1"%>

<html>
 <body>
    <form method="post" id="tzForm" action="/tzValueHandler">
      <input id="tzInput" type="hidden" name="timeZoneOffset"><br>
      <input type="hidden" name="requestedUrl" value="${requestedUrl}">
    </form>

    <script>
        var date = new Date();
        var offSet = date.getTimezoneOffset();
        document.getElementById("tzInput").value = offSet;
        document.getElementById("tzForm").submit();
    </script>

 </body>
</html>

Original Post

Spring MVC - HandlerInterceptor Examples

src\main\webapp\WEB-INF\views\tzJsPage.jsp:

See Also