Spring Boot @RequestParam
Spring Boot @RequestParam tutorial shows how to read a request parameter with @RequestParam annotation in a Spring Boot application.
Spring Boot @RequestParam
last modified July 16, 2023
In this article we are going to use the @RequestParam annotation in a controller to read request parameters.
Spring is a popular Java application framework and Spring Boot is an evolution of Spring which helps create stand-alone, production-grade Spring based applications easily.
Spring @RequestParam
@RequestParam is a Spring annotation used to bind a web request parameter to a method parameter.
It has the following optional elements:
-
defaultValue - used as a fallback when the request parameter is not provided or has an empty value
-
name - name of the request parameter to bind to
-
required - tells whether the parameter is required
-
value - alias for name
Spring @RequestParam example
The following example creates a Spring Boot web application which uses @RequestParam. We have an HTML form with two tags: text input and check box. These two tags create request parameters that are read in the controller with @RequestParam.
build.gradle … src ├── main │ ├── java │ │ └── com │ │ └── zetcode │ │ ├── Application.java │ │ └── controller │ │ └── MyController.java │ └── resources │ └── static │ └── index.html └── test ├── java └── resources
This is the project structure of the Spring Boot application.
build.gradle
plugins { id ‘org.springframework.boot’ version ‘3.1.1’ id ‘io.spring.dependency-management’ version ‘1.1.0’ id ‘java’ }
group = ‘com.zetcode’ version = ‘0.0.1-SNAPSHOT’ sourceCompatibility = ‘17’
repositories { mavenCentral() }
dependencies { implementation ‘org.springframework.boot:spring-boot-starter-web’ implementation ‘org.springframework.boot:spring-boot-devtools’ }
In the the Gradle build file we have the spring-boot-starter-web, which is a starter for building web applications using Spring MVC. It uses Tomcat as the default embedded container. The spring-boot-devtools is an artifact useful when developing Spring Boot applications; it allows automatic restart or live reload of applications. The application is packaged into a JAR file.
com/zetcode/controller/MyController.java
package com.zetcode.controller;
import org.springframework.http.MediaType; import org.springframework.stereotype.Controller; import org.springframework.web.bind.annotation.RequestMapping; import org.springframework.web.bind.annotation.RequestParam; import org.springframework.web.bind.annotation.ResponseBody;
@Controller public class MyController {
@RequestMapping(path="/message", produces=MediaType.TEXT_PLAIN_VALUE)
@ResponseBody
public String processForm(@RequestParam(defaultValue="Guest") String name,
@RequestParam(required = false) String adult) {
var greet = "on".equals(adult) ? "Good morning" : "Hi";
return String.format("%s %s!", greet, name);
}
}
The controller processes the HTML form. It reads two parameters from the request.
@Controller public class MyController {
A controller class is annotated with the @Controller annotation in Spring.
@RequestMapping(path="/message", produces=MediaType.TEXT_PLAIN_VALUE) @ResponseBody
The processForm method is mapped to the /message path and returns plain text. The @ResponseBody annotation indicates that the method return value is bound to the web response body.
public String processForm(@RequestParam(defaultValue=“Guest”) String name, @RequestParam(required = false) String adult) {
With the @RequestParam annotation, we bind the request parameter to the method variable. The defaultValue option gives a default value if the parameter is not available (the text input was left empty). The required option tells that the parameter is required. The method retuns a string.
var greet = “on”.equals(adult) ? “Good morning” : “Hi”;
return String.format("%s %s!", greet, name);
We build the message and return it.
resources/static/index.html
<!DOCTYPE html> <html lang=“en”> <head> <title>Home page</title> <meta charset=“UTF-8”/> <meta name=“viewport” content=“width=device-width, initial-scale=1.0”/> </head> <body>
<form action="message">
<div>
<label>Name:</label>
<input type="text" name="name">
</div>
<div>
<label><input type="checkbox" name="adult">Adult</label>
</div>
<button type="submit">Submit</button>
</form>
</body>
</html>
The index.html file is the home page. The file is located in the src/main/resources/static directory, where Spring Boot expects static resources such as HTML or CSS files. We have a simple HTML form with input text and check box tags.
<form action=“message”>
The action option contains a string that is used in controller method mapping.
com/zetcode/Application.java
package com.zetcode;
import org.springframework.boot.SpringApplication; import org.springframework.boot.autoconfigure.SpringBootApplication;
@SpringBootApplication public class Application {
public static void main(String[] args) {
SpringApplication.run(Application.class, args);
}
}
Application is the entry point which sets up Spring Boot application. The @SpringBootApplication annotation enables auto-configuration and component scanning.
$ ./gradlew bootRun
After the application is run, we can navigate to localhost:8080.
In this article we have created web application with Spring Boot framework. We have demonstrated the usage of @RequestParam.
Author
My name is Jan Bodnar, and I am a passionate programmer with extensive programming experience. I have been writing programming articles since 2007. To date, I have authored over 1,400 articles and 8 e-books. I possess more than ten years of experience in teaching programming.
