Building a RESTful Service with Spring Boot 3
June 20, 2024 ・0comments ・Topic： Java Maven Microservices Spring
This blog post is an upgraded version of my 2017 guide on building RESTful services using Spring Boot. It includes updates for the latest Spring Boot version, best practices, and enhanced code examples.
Creating Spring boot project is straightforward, You can create the structure of your project using "Spring Initialiser," an online tool where you can add all the desired dependencies to your project's POM file. Since I am a big fan of Maven, I generated a Maven project.
In the Spring Initializer UI, you can choose the Language, Spring Boot Version, Project Group ID, artifact name, etc. Please refer below screenshot for information I have provided while generating the project.
When clicking on "Generate Project", it will download zipped maven project into your computer. Unzip it and import into an IDE. The initial project structure is like below.
In my HelloWorld REST service implementation, it accepts user's name as a path parameter(or URL parameter) and returns a greeting JSON payload(response). So I am expecting to invoke my REST service by calling below URL: APP_NAME/api/hello/chandana.
The @RestController is a way to implement RESTFul service using Spring. So, this new controller class is going to name as HelloWorldController. @RequestMapping annotation maps HTTP requests to the handler. This @RequestMapping annotation can be used in class-level and/or method-level as well. If you have multiple request mappings for a method or class, you can add one @RequestMapping annotation with a list of values. So my HelloWorldController class looks like below.
package com.chandana.helloworld;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
@RestController
@RequestMapping("/api")
public class HelloWorldController {
@RequestMapping("/")
public String welcome() {// Welcome page, non-rest
return "Welcome to RestTemplate Example.";
}
@RequestMapping("/hello/{name}")
public Greeting message(@PathVariable String name) {
Greeting msg = new Greeting(name, "Hello " + name);
return msg;
}
@GetMapping("/greeting/{name}/{message}")
public Greeting message(@PathVariable String name, @PathVariable String message) {
Greeting msg = new Greeting(name, message);
return msg;
}
}
You can use @GetMapping, @PostMapping, @PutMapping, @DeleteMapping, @PatchMapping annotations as well, these are variation of @RequestMapping to support each HTTP methods.
So everything is in place. you can build and run Spring Boot project using below maven command. It will compile the project and run it.
mvn spring-boot:run
Once the Spring Boot DispatcherServlet is started, you can invoke the following API URLs:
http://localhost:8080/api/hello/Alex - This API supports all HTTP methods.
http://localhost:8080/api/greeting/Alex/WelCome - This API only supports the HTTP GET method.
Final Project Structure:
Greeting POJO class:
package com.chandana.helloworld;
public class Greeting {
private String player;
private String message;
public Greeting(String player, String message) {
this.player = player;
this.message = message;
}
public String getPlayer() {
return player;
}
public void setPlayer(String player) {
this.player = player;
}
public String getMessage() {
return message;
}
public void setMessage(String message) {
this.message = message;
}
}
POM XML:
<?xml version="1.0" encoding="UTF-8"?>
<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 https://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<parent>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-parent</artifactId>
<version>3.3.0</version>
<relativePath/>
<!-- lookup parent from repository -->
</parent>
<groupId>com.chandana</groupId>
<artifactId>helloworld</artifactId>
<version>0.0.1-SNAPSHOT</version>
<name>Hello World</name>
<description>Demo project for Spring Boot</description>
<url/>
<licenses>
<license/>
</licenses>
<developers>
<developer/>
</developers>
<scm>
<connection/>
<developerConnection/>
<tag/>
<url/>
</scm>
<properties>
<java.version>17</java.version>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-maven-plugin</artifactId>
</plugin>
</plugins>
</build>
</project>
HelloWorldController class:
package com.chandana.helloworld;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
@RestController
@RequestMapping("/api")
public class HelloWorldController {
@RequestMapping("/")
public String welcome() {// Welcome page, non-rest
return "Welcome to RestTemplate Example.";
}
@RequestMapping("/hello/{name}")
public Greeting message(@PathVariable String name) {
Greeting msg = new Greeting(name, "Hello " + name);
return msg;
}
@GetMapping("/greeting/{name}/{message}")
public Greeting message(@PathVariable String name, @PathVariable String message) {
Greeting msg = new Greeting(name, message);
return msg;
}
}
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