ViewResolver in Spring MVC

Spring MVC is a powerful Web MVC Framework for building web applications. It provides a structured way to develop web applications by separating concerns into Model, View, and Controller. One of the key features of Spring MVC is the ViewResolver, which enables you to render models in the browser without tying the implementation to a specific view technology.

In this article, we will discuss an example project in Spring Tool Suite (STS) to understand how ViewResolver works.

Spring MVC Components

The Spring MVC framework is comprised of the following components:

• Model: Represents the data of the application. It can be a single object or a collection of objects.
• View: Responsible for displaying information to the user in a specific format. Spring supports various view technologies like JSP, Thymeleaf, Freemarker, and Velocity.
• Controller: Contains the application’s business logic. Classes marked with the @Controller annotation act as controllers.
• Front Controller: Manages the flow of the web application. In Spring MVC, the DispatcherServlet acts as the front controller.

Prerequisites:

Prior to it, certain requirements are needed that are as follows:  

1. Eclipse (EE version)/STS IDE
2. Spring JAR Files
3. Tomcat Apache latest version

Note: We are going to use Spring Tool Suite 4 IDE for this project. Please refer to this article to install STS in your local machine How to Download and Install Spring Tool Suite (Spring Tools 4 for Eclipse) IDE? 

Step-by-Step Implementation

Step 1: Create a Dynamic Web Project in STS

Create a Dynamic Web Project in your STS IDE for which one should be well versed in how to create a Dynamic Web Project in Spring Tool Suite?

Step 2: Add Spring JAR Files

Download the spring JARs file and place them in the src > main > webapp > WEB-INF > lib folder.

Step 3: Configure Apache Tomcat Server

Configure the Apache Tomcat Server and link it to the application.

Step 4: Configure Dispatcher Servlet

The DispatcherServlet is a critical component in Spring MVC. It acts as the front controller and manages the flow of requests. Now we are going to configure Dispatcher Servlet with our Spring MVC application, Go to the src > main > webapp > WEB-INF > web.xml file.

web.xml:

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xmlns="http://xmlns.jcp.org/xml/ns/javaee"
         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee 
                             http://xmlns.jcp.org/xml/ns/javaee/web-app_4_0.xsd"
         id="WebApp_ID" version="4.0">
    <display-name>springmvc-view-resolver</display-name>
    <welcome-file-list>
        <welcome-file>index.html</welcome-file>
        <welcome-file>index.jsp</welcome-file>
        <welcome-file>index.htm</welcome-file>
        <welcome-file>default.html</welcome-file>
        <welcome-file>default.jsp</welcome-file>
        <welcome-file>default.htm</welcome-file>
    </welcome-file-list>

    <servlet>
        <!-- Provide a Servlet Name -->
        <servlet-name>viewresolver-dispatcher</servlet-name>
        <!-- Provide a fully qualified path to the DispatcherServlet class -->
        <servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
        <load-on-startup>1</load-on-startup>
    </servlet>

    <servlet-mapping>
        <!-- Provide a Servlet Name that you want to map -->
        <servlet-name>viewresolver-dispatcher</servlet-name>
        <!-- Provide a URL pattern -->
        <url-pattern>/</url-pattern>
    </servlet-mapping>
</web-app>

Step 5: Create Spring Configuration File

Now go to the  src > main > webapp > WEB-INF and create an XML file. Actually, this is a Spring Configuration file like the beans.xml file. And the name of the file must be in this format.

YourServletName-servlet.xml

For example, for this project, the name of the file must be

viewresolver-dispatcher-servlet.xml

So either you can create a Spring Configuration File or you can just create a simple XML file and add the below lines of code inside that file.

viewresolver-dispatcher-servlet.xml:

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.geeksforgeeks.org/2001/XMLSchema-instance"
       xmlns:context="http://www.springframework.org/schema/context"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
        https://www.springframework.org/schema/beans/spring-beans.xsd
        http://www.springframework.org/schema/context
        https://www.springframework.org/schema/context/spring-context.xsd">
  
  <!-- This Line is used for scanning all the packages that have controller classes -->
  <context:component-scan base-package="com.demo.controllers"></context:component-scan>

</beans>

Step 6: Creating Spring MVC Controller

Now, let’s create some controllers. Go to the src/main/java and create a new controllers package (For ex. com.demo.controllers) as per your choice. And inside that create a Java class and name the class as DemoController. Now how to tell the Spring that this is our controller class. So the way we are going to tell the Spring is by marking it with a @Controller annotation.

@Controller

public class DemoController {}

Note: Spring will automatically initialize the class having a @Controller annotation and register that class with the spring container.

Now let us create a simple method inside the Controller class and use the @RequestMapping annotation before the method something like this.

// Annotation

@RequestMapping(“/hello”)

// Method

public String helloWorld()

{

return “”;

}

Now in the return statement, we have to return some views (web pages), so whenever the endpoint ‘/hello’ is invoked we can see our result on the web page. So let’s create our first View.

Step 7: Creating View

Go to the src > main > webapp > WEB-INF > right-click > New > Folder and name the folder as views. Then views > right-click > New > JSP File and name your first view. Here we have named it a demo.jsp file. Below is the code for the demo.jsp file. We have created a simple web page inside that file. 

demo.jsp:

<!DOCTYPE html>
<html>
<body bgcolor="green">
    <h1>Hello GeeksforGeeks!</h1>
</body>
</html>

Now go to the DemoController class and inside the helloWorld() method we have to return a value something like this.

return “/WEB-INF/views/demo.jsp”;

We have just been given the path for our view.

DemoController.java:

// Java Program to Illustrate DemoController Class

package com.demo.controllers;

// Importing required classes
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;

// Class
@Controller
public class DemoController {

    // Method
    @RequestMapping("/hello") public String helloWorld()
    {
        return "/WEB-INF/views/demo.jsp";
    }
}

Step 8: Running Spring MVC Application

To run our Spring MVC Application right-click on your project > Run As > Run on Server. And run your application as shown in the below image as depicted below as follows:  

After that use the following URL to run your controller

http://localhost:8080/springmvc-view-resolver/demo.com/hello

Output:

Understanding the Problem with Hardcoded Paths

So what’s the problem with the above project? Just go to the DemoController.java file again and the problem lies in this line of code:

return “/WEB-INF/views/demo.jsp”;

So the scenario is, suppose someone tells us to create or move this demo.jsp file inside another directory and here we have to change the path again which is not a standard coding practice. The problem here is, that we have provided a fully qualified path in our controller handler method which makes our application tightly coupled and the solution for this problem is ViewResolver. For changing the path many times you should go to your spring configuration file (here is: viewresolver-dispatcher-servlet.xml) and there you can modify these things. Now let’s understand how ViewResolver solves this problem.  

Here is this line, /WEB-INF/views/demo.jsp, sometimes a scenario exists, when somebody wants to change either WEB-INF/views (the path) or .jsp (the extension like .html), the name must be the same. 

And we call them prefixes and suffixes accordingly. Now let’s understand this thing in the following code but before that let’s learn about ViewResolver a little bit. In the Spring framework, there is plenty of ViewResolver available. But in this project, we are going to use InternalResourceViewResolver. Now let us jump to the coding part. 

Step 9: Update DemoController.java 

Go to the DemoController.java file and modify the code as shown in the below snippet. 

Modified DemoController.java:

// Java Program to Illustrate DemoController Class

package com.demo.controllers;

// Importing required classes
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.RequestMapping;

// Class
@Controller
public class DemoController {

    // Method
    @RequestMapping("/hello") public String helloWorld()
    {

        // Just return the page name
        // No Path, no extension
        return "demo";
    }
}

Here we have only returned the page name, nothing else. 

Note: The return file name and the View name must be same because we are returning that web page from the controller handler method. 

Configure ViewResolver inside the Spring Configuration File (i.e. viewresolver-dispatcher-servlet.xml)

Step 10: Modify the viewresolver-dispatcher-servlet.xml

Add the below lines of code as follows: 

<bean id = ‘viewResolver’ class = “org.springframework.web.servlet.view.InternalResourceViewResolver”>

<property name=”prefix” value=”/WEB-INF/views/”/>

<property name=”suffix” value=”.jsp”/>

</bean>

This is the thing we have discussed above and it’s completely the concept of Setter Based Dependency Injection in the spring framework.

viewresolver-dispatcher-servlet.xml:

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.geeksforgeeks.org/2001/XMLSchema-instance"
       xmlns:context="http://www.springframework.org/schema/context"
       xsi:schemaLocation="http://www.springframework.org/schema/beans
        https://www.springframework.org/schema/beans/spring-beans.xsd
        http://www.springframework.org/schema/context
        https://www.springframework.org/schema/context/spring-context.xsd">
  
  <!-- This Line is used for scanning all the packages that have controller classes -->
  <context:component-scan base-package="com.demo.controllers"></context:component-scan>
  
  <!-- Configure ViewResolver -->
  <bean id = 'viewResolver' class = "org.springframework.web.servlet.view.InternalResourceViewResolver">
    <property name="prefix" value="/WEB-INF/views/"/>
    <property name="suffix" value=".jsp"/>
  </bean>

</beans>

Now inside this “value” property, you can change according to the requirements as many times as you want. Now run your spring application and the output will be as follows.

Output: