Spring boot REST: @RequestParam: Access request or query parameters

Using @RequestParam annotation, you can map request parameters to controller method parameters.

Example

@RequestMapping("/")
public String home(@RequestParam(name = "name", defaultValue = "user") String userName, @RequestParam(name = "gender", defaultValue = "m") String gender) {
    
    ......
    ......

}

For the uri http://localhost:8080/?name=sailu&gender=f, userName mapped to sailu and gender mapped to f.

Find the below working application.

App.java

package com.sample.app;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;

@SpringBootApplication
public class App {
    public static void main(String[] args) {

        SpringApplication.run(App.class, args);

    }
}

HomeController.java

package com.sample.app.cotroller;

import java.util.Enumeration;

import javax.servlet.http.HttpServletRequest;

import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.RequestHeader;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class HomeController {

    @RequestMapping("/")
    public String home(@RequestParam(name = "name", defaultValue = "user") String userName, @RequestParam(name = "gender", defaultValue = "m") String gender) {
        StringBuilder builder = new StringBuilder();
        
        builder.append("Hello, ");
        
        if("f".equalsIgnoreCase(gender)) {
            builder.append(" Madam ");
        }else {
            builder.append("Mr. ");
        }
        
        builder.append(userName).append(". Have a great day!!!!!!");
        
        return builder.toString();
    }

    @RequestMapping("/headers")
    public String headers(HttpServletRequest request) {

        Enumeration<String> headerNames = request.getHeaderNames();

        StringBuilder builder = new StringBuilder();

        while (headerNames.hasMoreElements()) {
            String headerName = headerNames.nextElement();
            String headerValue = request.getHeader(headerName);

            builder.append(headerName).append(" : ").append(headerValue).append("<br />");

        }

        return builder.toString();
    }

    @RequestMapping("/userAgent")
    public ResponseEntity<String> getData(@RequestHeader(value = "user-agent") String userAgent) {
        return ResponseEntity.ok(userAgent);

    }

}

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/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <groupId>springRest</groupId>
    <artifactId>springRest</artifactId>
    <version>1</version>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.1.6.RELEASE</version>
    </parent>

    <name>springbootApp</name>
    <url>http://maven.apache.org</url>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    </properties>

    <dependencies>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

Total project structure looks like below.

Run App.java.

Open the url 'http://localhost:8080/?name=sailu&gender=f' in browser, you can see below welcome screen.

You can download complete working application from this link.

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