Programming for beginners: Spring mvc: Mapping urls to interceptors

This is continuation to my previous post. In my previous post, I explained how to intercept a request. In this post, I am going to show you how to map a url to an interceptor.

It is very simple, add below lines in dispatcher servlet.

<mvc:interceptors>

<mvc:interceptor>

<mvc:mapping path="/welcome" />

</mvc:interceptor>

</mvc:interceptors>

As you see above snippet, I mapped the url /welcome to PerformanceReportInterceptor. PerformanceReportInterceptor is not been invoked for any other requests.

Find the below working application.

HelloWorldController.java

package com.sample.myApp.controllers;

import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.servlet.ModelAndView;

@Controller
public class HelloWorldController {

 @RequestMapping("/welcome")
 public ModelAndView getHelloMessage() {

  ModelAndView modelAndView = new ModelAndView("welcome");

  modelAndView.addObject("message", "Dear User, Good Morning");

  return modelAndView;
 }

}

I defined an interceptor that is used to calculate the exection time of the request.

PerformanceReportInterceptor.java

package com.sample.myApp.interceptors;

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

import org.springframework.lang.Nullable;
import org.springframework.web.servlet.HandlerInterceptor;
import org.springframework.web.servlet.ModelAndView;

public class PerformanceReportInterceptor implements HandlerInterceptor {

 private long startTime;

 public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler)
   throws Exception {
  startTime = System.nanoTime();
  return true;

 }

 public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler,
   @Nullable ModelAndView modelAndView) throws Exception {
  long executionTime = System.nanoTime() - startTime;
  modelAndView.addObject("executionTime", executionTime);
 }
}

Create welcome.jsp file under WEB-INF/jsp folder.

welcome.jsp

<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
 pageEncoding="ISO-8859-1"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>Hello World Spring Web MVC</title>
</head>
<body>
 <h1>${message}</h1>

 <h3>
  ${message} <br /> 
  Execution Time : ${executionTime} nanoseconds<br />
 </h3>
</body>
</html>

Create web.xml, HelloWorld-servlet.xml files under WEB-INF folder.

web.xml

<web-app id="WebApp_ID" version="2.4"
 xmlns="http://java.sun.com/xml/ns/j2ee"
 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee 
   http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">

 <display-name>Spring MVC Hello WorldApplication</display-name>

 <servlet>
  <servlet-name>HelloWorld</servlet-name>
  <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
  <load-on-startup>1</load-on-startup>
 </servlet>

 <servlet-mapping>
  <servlet-name>HelloWorld</servlet-name>
  <url-pattern>/</url-pattern>
 </servlet-mapping>

</web-app>

HelloWorld-servlet.xml

<beans xmlns="http://www.springframework.org/schema/beans"
 xmlns:context="http://www.springframework.org/schema/context"
 xmlns:mvc="http://www.springframework.org/schema/mvc"
 xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
 xsi:schemaLocation="
        http://www.springframework.org/schema/beans     
        http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
        http://www.springframework.org/schema/context 
        http://www.springframework.org/schema/context/spring-context-3.0.xsd
        http://www.springframework.org/schema/mvc
        http://www.springframework.org/schema/mvc/spring-mvc-3.0.xsd">

 <mvc:annotation-driven />

 <context:component-scan
  base-package="com.sample.myApp" />

 <bean
  class="org.springframework.web.servlet.view.InternalResourceViewResolver">
  <property name="prefix" value="/WEB-INF/jsp/" />
  <property name="suffix" value=".jsp" />
 </bean>

 <mvc:interceptors>
  <mvc:interceptor>
   <mvc:mapping path="/welcome" />
   <bean class="com.sample.myApp.interceptors.PerformanceReportInterceptor" />
  </mvc:interceptor>
 </mvc:interceptors>

</beans>

Create index.jsp file under webapp folder.

index.jsp

<%@taglib prefix="form" uri="http://www.springframework.org/tags/form"%>
<html>
<head>
<title>Welcome Page</title>
</head>

<body>
 <h2>Click on below button to get welcome page</h2>
 <form method="post" action="/springdemo/welcome" id="f1">
  <input type="submit" name="submit" value="submit"
   style="font-size: 18px;" />
 </form>
</body>
</html>

Project structure looks like below.

Run the application on server. You can able to see below screen.

Click on submit button, you can able to see below screen.

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Programming for beginners

Saturday 1 December 2018

Spring mvc: Mapping urls to interceptors

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