Getting Started: Serving Web Content

Serving Web Content with Spring MVC

This guide walks you through the process of creating a “Hello, World” web site with Spring.

What You Will Build

You will build an application that has a static home page and that will also accept HTTP GET requests at: http://localhost:8080/greeting .

It will respond with a web page that displays HTML. The body of the HTML will contain a greeting: “Hello, World!”

You can customize the greeting with an optional name parameter in the query string. The URL might then be http://localhost:8080/greeting?name=User .

The name parameter value overrides the default value of World and is reflected in the response by the content changing to “Hello, User!”

What You Need

• About 15 minutes
• A favorite text editor or IDE
• Java 17 or later
• Gradle 7.5+ or Maven 3.5+
• You can also import the code straight into your IDE:

How to complete this guide

Like most Spring Getting Started guides, you can start from scratch and complete each step or you can bypass basic setup steps that are already familiar to you. Either way, you end up with working code.

To start from scratch, move on to Starting with Spring Initializr.

To skip the basics, do the following:

• Download and unzip the source repository for this guide, or clone it using Git: git clone https://github.com/spring-guides/gs-serving-web-content.git
• cd into gs-serving-web-content/initial
• Jump ahead to Create a Web Controller.

When you finish, you can check your results against the code in gs-serving-web-content/complete .

Starting with Spring Initializr

You can use this pre-initialized project and click Generate to download a ZIP file. This project is configured to fit the examples in this tutorial.

To manually initialize the project:

1. Navigate to https://start.spring.io. This service pulls in all the dependencies you need for an application and does most of the setup for you.
2. Choose either Gradle or Maven and the language you want to use. This guide assumes that you chose Java.
3. Click Dependencies and select Spring Web, Thymeleaf, and Spring Boot DevTools.
4. Click Generate.
5. Download the resulting ZIP file, which is an archive of a web application that is configured with your choices.

Create a Web Controller

In Spring’s approach to building web sites, HTTP requests are handled by a controller. You can easily identify the controller by the @Controller annotation. In the following example, GreetingController handles GET requests for /greeting by returning the name of a View (in this case, greeting ). A View is responsible for rendering the HTML content. The following listing (from src/main/java/com/example/servingwebcontent/GreetingController.java ) shows the controller:

package com.example.servingwebcontent; import org.springframework.stereotype.Controller; import org.springframework.ui.Model; import org.springframework.web.bind.annotation.GetMapping; import org.springframework.web.bind.annotation.RequestParam; @Controller public class GreetingController < @GetMapping("/greeting") public String greeting(@RequestParam(name="name", required=false, defaultValue="World") String name, Model model) < model.addAttribute("name", name); return "greeting"; >>

This controller is concise and simple, but there is plenty going on. We break it down step by step.

The @GetMapping annotation ensures that HTTP GET requests to /greeting are mapped to the greeting() method.

@RequestParam binds the value of the query string parameter name into the name parameter of the greeting() method. This query string parameter is not required . If it is absent in the request, the defaultValue of World is used. The value of the name parameter is added to a Model object, ultimately making it accessible to the view template.

The implementation of the method body relies on a view technology (in this case, Thymeleaf) to perform server-side rendering of the HTML. Thymeleaf parses the greeting.html template and evaluates the th:text expression to render the value of the $ parameter that was set in the controller.The following listing (from src/main/resources/templates/greeting.html ) shows the greeting.html template:

      + '!'" /> 

Make sure you have Thymeleaf on your classpath (artifact co-ordinates: org.springframework.boot:spring-boot-starter-thymeleaf ). It is already there in the «initial» and «complete» samples in Github.

Spring Boot Devtools

A common feature of developing web applications is coding a change, restarting your application, and refreshing the browser to view the change. This entire process can eat up a lot of time. To speed up this refresh cycle, Spring Boot offers with a handy module known as spring-boot-devtools. Spring Boot Devtools:

• Enables hot swapping.
• Switches template engines to disable caching.
• Enables LiveReload to automatically refresh the browser.
• Other reasonable defaults based on development instead of production.

Run the Application

The Spring Initializr creates an application class for you. In this case, you need not further modify the class provided by the Spring Initializr. The following listing (from src/main/java/com/example/servingwebcontent/ServingWebContentApplication.java ) shows the application class:

package com.example.servingwebcontent; import org.springframework.boot.SpringApplication; import org.springframework.boot.autoconfigure.SpringBootApplication; @SpringBootApplication public class ServingWebContentApplication < public static void main(String[] args) < SpringApplication.run(ServingWebContentApplication.class, args); >>

@SpringBootApplication is a convenience annotation that adds all of the following:

• @Configuration : Tags the class as a source of bean definitions for the application context.
• @EnableAutoConfiguration : Tells Spring Boot to start adding beans based on classpath settings, other beans, and various property settings. For example, if spring-webmvc is on the classpath, this annotation flags the application as a web application and activates key behaviors, such as setting up a DispatcherServlet .
• @ComponentScan : Tells Spring to look for other components, configurations, and services in the com/example package, letting it find the controllers.

The main() method uses Spring Boot’s SpringApplication.run() method to launch an application. Did you notice that there was not a single line of XML? There is no web.xml file, either. This web application is 100% pure Java and you did not have to deal with configuring any plumbing or infrastructure.

Build an executable JAR

You can run the application from the command line with Gradle or Maven. You can also build a single executable JAR file that contains all the necessary dependencies, classes, and resources and run that. Building an executable jar makes it easy to ship, version, and deploy the service as an application throughout the development lifecycle, across different environments, and so forth.

If you use Gradle, you can run the application by using ./gradlew bootRun . Alternatively, you can build the JAR file by using ./gradlew build and then run the JAR file, as follows:

java -jar build/libs/gs-serving-web-content-0.1.0.jar

If you use Maven, you can run the application by using ./mvnw spring-boot:run . Alternatively, you can build the JAR file with ./mvnw clean package and then run the JAR file, as follows:

java -jar target/gs-serving-web-content-0.1.0.jar

Logging output is displayed. The application should be up and running within a few seconds.

Test the Application

Now that the web site is running, visit http://localhost:8080/greeting , where you should see “Hello, World!”

Provide a name query string parameter by visiting http://localhost:8080/greeting?name=User . Notice how the message changes from “Hello, World!” to “Hello, User!”:

This change demonstrates that the @RequestParam arrangement in GreetingController is working as expected. The name parameter has been given a default value of World , but it can be explicitly overridden through the query string.

Add a Home Page

Static resources, including HTML and JavaScript and CSS, can be served from your Spring Boot application by dropping them into the right place in the source code. By default, Spring Boot serves static content from resources in the classpath at /static (or /public ). The index.html resource is special because, if it exists, it is used as a «`welcome page, «serving-web-content/ which means it is served up as the root resource (that is, at `http://localhost:8080/ ). As a result, you need to create the following file (which you can find in src/main/resources/static/index.html ):

     
Get your greeting here
  

When you restart the application, you will see the HTML at http://localhost:8080/ .

Summary

Congratulations! You have just developed a web page by using Spring.

See Also

The following guides may also be helpful:

Want to write a new guide or contribute to an existing one? Check out our contribution guidelines.

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HTML 5 Forms Validation in Spring MVC

Create new package, named com.demo.entities. In this package, create entities class as below:

Account Entity

Create new java class, named Account.java

package com.demo.entities; public class Account < private String username; private String password; private int age; private String email; private String website; public String getUsername() < return username; >public void setUsername(String username) < this.username = username; >public String getPassword() < return password; >public void setPassword(String password) < this.password = password; >public int getAge() < return age; >public void setAge(int age) < this.age = age; >public String getEmail() < return email; >public void setEmail(String email) < this.email = email; >public String getWebsite() < return website; >public void setWebsite(String website) < this.website = website; >> 

Create Controller

Create new package named com.demo.controllers. In this package, create new controller name AccountController as below:

package com.demo.controllers; import org.springframework.stereotype.Controller; import org.springframework.ui.ModelMap; import org.springframework.web.bind.annotation.ModelAttribute; import org.springframework.web.bind.annotation.RequestMapping; import org.springframework.web.bind.annotation.RequestMethod; import com.demo.entities.Account; @Controller @RequestMapping(value = "account") public class AccountController < @RequestMapping(method = RequestMethod.GET) public String index(ModelMap modelMap) < modelMap.put("account", new Account()); return "account/index"; >@RequestMapping(value = "save", method = RequestMethod.POST) public String save(@ModelAttribute("account") Account account, ModelMap modelMap) < modelMap.put("account", account); return "account/success"; >> 

Create View

Create new folders with path webapp\WEB-INF\views in src\main. In views folder, create new folder named account. In account folder, create new JSP Pages as below:

Index View

Create new jsp file named index.jsp. This view use HTML5 attributes validate data in form

       
Account Register
  
 
Username
 
 
 
Password
 
" title="Must contain at least one number and one uppercase and lowercase letter, and at least 8 or more characters" path="password" />
 
 
Age
 
 
 
Email
 
 
 
Website
 
 
 
 
 
 
 
    

Success View

Create new jsp file named success.jsp

       
Account Info
 
 
Username
 
$
 
Password
 
$
 
Age
 
$
 
Email
 
$
 
Website
 
$
 
   

Structure of Spring MVC Project

Run Application

Select LearnSpringMVCWithRealAppsApplication.java file in com.demo package, right click and select Run As/Spring Boot App menu

Access index method in account controller with following url: http://localhost:9596/account

Click Save button submit form to save method in account controller with some instances of invalid data as below:

Click Save button submit form to save method in account controller with valid data

References

I recommend you refer to the books below to learn more about the knowledge in this article:

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