Spring MVC Interceptors Tutorial

1- What is Spring Interceptor?

When you come to a company and want to meet the company's manager. You need to pass through interceptors which can be a gatekeeper, a receptionist,...

In Spring, when a request is sent to spring controller, it will have to pass through Interceptors (0 or more) before being processed by Controller.

Spring Interceptor is a concept that is rather similar to Servlet Filter.

Spring Interceptor is only applied to requests that are sending to a Controller.
You can use Interceptor to do some tasks such as writing log, adding or updating configurations before request is processed by Controller,...
One of the Spring MVCs using Interceptor as "Multilingual web application". You can see more about the application here:
Your Interceptor must implement org.springframework.web.servlet.HandlerInterceptor interface or extended from  org.springframework.web.servlet.handler.HandlerInterceptorAdapter class.
You need to implement three abstract methods:
  • public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler)
  • public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler,ModelAndView modelAndView)
  • public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex)
Note: The preHandle method returns true or false. If it returns true, it means request will continue to come to its destination (Is a Controller).
Each request may pass through a lot of Interceptors. The figure below illustrates that.

2- Create Maven Project

  • File/New/Other..
  • Group Id: org.o7planning
  • Artifact Id: SpringMVCInterceptor
  • Package: org.o7planning.springmvcinterceptor
Project is created.
Make sure that you use Java >=6.
Project Properties:

3- Declare Maven & web.xml

Using Servlet >= 3.
web.xml
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns="http://java.sun.com/xml/ns/javaee"
    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
    http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
    id="WebApp_ID" version="3.0">
   
    <display-name>SpringMVCInterceptor</display-name>
   
</web-app>
pom.xml
<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0
http://maven.apache.org/maven-v4_0_0.xsd">


<modelVersion>4.0.0</modelVersion>
<groupId>org.o7planning</groupId>
<artifactId>SpringMVCInterceptor</artifactId>
<packaging>war</packaging>
<version>0.0.1-SNAPSHOT</version>
<name>SpringMVCInterceptor Maven Webapp</name>
<url>http://maven.apache.org</url>


  <dependencies>
      <dependency>
          <groupId>junit</groupId>
          <artifactId>junit</artifactId>
          <version>3.8.1</version>
          <scope>test</scope>
      </dependency>


      <!-- Servlet API -->
      <!-- http://mvnrepository.com/artifact/javax.servlet/javax.servlet-api -->
      <dependency>
          <groupId>javax.servlet</groupId>
          <artifactId>javax.servlet-api</artifactId>
          <version>3.1.0</version>
          <scope>provided</scope>
      </dependency>


      <!-- Jstl for jsp page -->
      <!-- http://mvnrepository.com/artifact/javax.servlet/jstl -->
      <dependency>
          <groupId>javax.servlet</groupId>
          <artifactId>jstl</artifactId>
          <version>1.2</version>
      </dependency>


      <!-- JSP API -->
      <!-- http://mvnrepository.com/artifact/javax.servlet.jsp/jsp-api -->
      <dependency>
          <groupId>javax.servlet.jsp</groupId>
          <artifactId>jsp-api</artifactId>
          <version>2.2</version>
          <scope>provided</scope>
      </dependency>



      <!-- Spring dependencies -->
      <!-- http://mvnrepository.com/artifact/org.springframework/spring-core -->
      <dependency>
          <groupId>org.springframework</groupId>
          <artifactId>spring-core</artifactId>
          <version>4.3.3.RELEASE</version>
      </dependency>

      <!-- http://mvnrepository.com/artifact/org.springframework/spring-web -->
      <dependency>
          <groupId>org.springframework</groupId>
          <artifactId>spring-web</artifactId>
          <version>4.3.3.RELEASE</version>
      </dependency>

      <!-- http://mvnrepository.com/artifact/org.springframework/spring-webmvc -->
      <dependency>
          <groupId>org.springframework</groupId>
          <artifactId>spring-webmvc</artifactId>
          <version>4.3.3.RELEASE</version>
      </dependency>


  </dependencies>
 
 
  <build>
      <finalName>SpringMVCInterceptor</finalName>
      <plugins>

          <!-- Config: Maven Tomcat Plugin -->
          <!-- http://mvnrepository.com/artifact/org.apache.tomcat.maven/tomcat7-maven-plugin -->
          <plugin>
              <groupId>org.apache.tomcat.maven</groupId>
              <artifactId>tomcat7-maven-plugin</artifactId>
              <version>2.2</version>
            
              <!-- Config: contextPath and Port (Default - /SpringMVCInterceptor : 8080) -->
            
              <!--
              <configuration>
                  <path>/</path>
                  <port>8899</port>
              </configuration>
              -->
          </plugin>
      </plugins>
  </build>
 
</project>

4- Configuring Spring MVC

SpringWebAppInitializer.java
package org.o7planning.springmvcinterceptor.config;

import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.ServletRegistration;

import org.springframework.web.WebApplicationInitializer;
import org.springframework.web.context.support.AnnotationConfigWebApplicationContext;
import org.springframework.web.servlet.DispatcherServlet;

public class SpringWebAppInitializer implements WebApplicationInitializer {

    @Override
    public void onStartup(ServletContext servletContext) throws ServletException {
        AnnotationConfigWebApplicationContext appContext = new AnnotationConfigWebApplicationContext();
        appContext.register(ApplicationContextConfig.class);

        ServletRegistration.Dynamic dispatcher = servletContext.addServlet("SpringDispatcher",
                new DispatcherServlet(appContext));
        dispatcher.setLoadOnStartup(1);
        dispatcher.addMapping("/");
    }

}
ApplicationContextConfig.java
package org.o7planning.springmvcinterceptor.config;

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.view.InternalResourceViewResolver;

@Configuration

@ComponentScan("org.o7planning.springmvcinterceptor.*")
public class ApplicationContextConfig {

    @Bean(name = "viewResolver")
    public InternalResourceViewResolver getViewResolver() {
        InternalResourceViewResolver viewResolver = new InternalResourceViewResolver();

        viewResolver.setPrefix("/WEB-INF/pages/");
        viewResolver.setSuffix(".jsp");

        return viewResolver;
    }
 
}
Interceptors will be registered with the application by WebMvcConfig.
WebMvcConfig.java
package org.o7planning.springmvcinterceptor.config;

import org.o7planning.springmvcinterceptor.interceptor.AdminInterceptor;
import org.o7planning.springmvcinterceptor.interceptor.LogInterceptor;
import org.o7planning.springmvcinterceptor.interceptor.OldLoginInterceptor;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.DefaultServletHandlerConfigurer;
import org.springframework.web.servlet.config.annotation.EnableWebMvc;
import org.springframework.web.servlet.config.annotation.InterceptorRegistry;
import org.springframework.web.servlet.config.annotation.ResourceHandlerRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurerAdapter;

@Configuration
@EnableWebMvc
public class WebMvcConfig extends WebMvcConfigurerAdapter {

    // Static Resource Config
    @Override
    public void addResourceHandlers(ResourceHandlerRegistry registry) {

    }

    @Override
    public void configureDefaultServletHandling(DefaultServletHandlerConfigurer configurer) {
        configurer.enable();
    }

    //
    @Override
    public void addInterceptors(InterceptorRegistry registry) {
        // LogInterceptor apply to all URLs.
        registry.addInterceptor(new LogInterceptor());

        // This URL is old, It no longer use.
        // Using OldURLInterceptor to redirecto to new URL.
        registry.addInterceptor(new OldLoginInterceptor())//
                .addPathPatterns("/admin/oldLogin");

        // This interceptor apply to URL like /admin/*
        // Exclude /admin/oldLogin
 
        registry.addInterceptor(new AdminInterceptor())//
                .addPathPatterns("/admin/*")//
                .excludePathPatterns("/admin/oldLogin");
    }

}

5- Interceptor classes

LogInterceptor is applied to all requests coming to a Controller. (See the configure in WebMvcConfig).
LogInterceptor.java
package org.o7planning.springmvcinterceptor.interceptor;

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

import org.springframework.web.servlet.ModelAndView;
import org.springframework.web.servlet.handler.HandlerInterceptorAdapter;

public class LogInterceptor extends HandlerInterceptorAdapter {

    @Override
    public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler)
            throws Exception {
        long startTime = System.currentTimeMillis();
        System.out.println("\n-------- LogInterception.preHandle --- ");
        System.out.println("Request URL: " + request.getRequestURL());
        System.out.println("Start Time: " + System.currentTimeMillis());

        request.setAttribute("startTime", startTime);
         
        return true;
    }

    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler,
            ModelAndView modelAndView) throws Exception {
        System.out.println("\n-------- LogInterception.postHandle --- ");
        System.out.println("Request URL: " + request.getRequestURL());

        // You can add attributes in the modelAndView
        // and use that in the view page
    }

    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex)
            throws Exception {
        System.out.println("\n-------- LogInterception.afterCompletion --- ");

        long startTime = (Long) request.getAttribute("startTime");
        long endTime = System.currentTimeMillis();
        System.out.println("Request URL: " + request.getRequestURL());
        System.out.println("End Time: " + endTime);

        System.out.println("Time Taken: " + (endTime - startTime));
    }

}
OldLoginInterceptor is an interceptor, if user enters the link   "/admin/oldLogin", it will redirect to the new one "/admin/login".
OldLoginInterceptor.java
package org.o7planning.springmvcinterceptor.interceptor;

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

import org.springframework.web.servlet.ModelAndView;
import org.springframework.web.servlet.handler.HandlerInterceptorAdapter;

public class OldLoginInterceptor extends HandlerInterceptorAdapter {

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

       System.out.println("\n-------- OldLoginInterceptor.preHandle --- ");
       System.out.println("Request URL: " + request.getRequestURL());
       System.out.println("Sorry! This URL is no longer used, Redirect to /admin/login");
 
       response.sendRedirect(request.getContextPath()+"/admin/login");
       return false;
   }

   @Override
   public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler,
           ModelAndView modelAndView) throws Exception {
     
       // This code will never be run.
       System.out.println("\n-------- OldLoginInterceptor.postHandle --- ");
   }

   @Override
   public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex)
           throws Exception {
       // This code will never be run.
       System.out.println("\n-------- QueryStringInterceptor.afterCompletion --- ");
   }

}
AdminInterceptor.java
package org.o7planning.springmvcinterceptor.interceptor;

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

import org.springframework.web.servlet.ModelAndView;
import org.springframework.web.servlet.handler.HandlerInterceptorAdapter;

public class AdminInterceptor extends HandlerInterceptorAdapter {

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

        System.out.println("\n-------- AdminInterceptor.preHandle --- ");
        return true;
    }

    @Override
    public void postHandle(HttpServletRequest request, HttpServletResponse response, Object handler,
            ModelAndView modelAndView) throws Exception {
        System.out.println("\n-------- AdminInterceptor.postHandle --- ");
    }

    @Override
    public void afterCompletion(HttpServletRequest request, HttpServletResponse response, Object handler, Exception ex)
            throws Exception {
        System.out.println("\n-------- AdminInterceptor.afterCompletion --- ");
    }

}

6- Controllers

MainController.java
package org.o7planning.springmvcinterceptor.controller;

import org.springframework.stereotype.Controller;
import org.springframework.ui.Model;
import org.springframework.web.bind.annotation.RequestMapping;

@Controller
public class MainController {

   @RequestMapping(value = { "/", "/test" })
   public String test(Model model) {

       System.out.println("\n-------- MainController.test --- ");

       System.out.println(" ** You are in Controller ** ");

       return "test";
   }

   // This path is no longer used.
   // It will be redirected by OldLoginInterceptor or
   @Deprecated
   @RequestMapping(value = { "/admin/oldLogin" })
   public String oldLogin(Model model) {
       // Code here never run.
       return "oldLogin";
   }

   @RequestMapping(value = { "/admin/login" })
   public String login(Model model) {

       System.out.println("\n-------- MainController.login --- ");

       System.out.println(" ** You are in Controller ** ");

       return "login";
   }

}

7- Running Apps

Run URL:
And here is Log viewed on Console screen:
Run URL:
View Log: