Spring Boot Hello World REST API

目标

创建一个最简单的 Spring Boot REST API，返回 "Hello, World!" JSON 响应。

完整代码

1. 主应用类 DemoApplication.java

package com.example.demo;

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

@SpringBootApplication
public class DemoApplication {

    public static void main(String[] args) {
        SpringApplication.run(DemoApplication.class, args);
    }
}

2. REST 控制器 HelloController.java

package com.example.demo.controller;

import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestParam;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class HelloController {

    @GetMapping("/hello")
    public String hello() {
        return "Hello, World!";
    }

    @GetMapping("/hello/json")
    public Greeting greeting(@RequestParam(defaultValue = "World") String name) {
        return new Greeting("Hello, " + name + "!");
    }
}

class Greeting {
    private String message;

    public Greeting(String message) {
        this.message = message;
    }

    public String getMessage() {
        return message;
    }
}

3. 配置文件 application.properties

server.port=8080
spring.application.name=demo

运行步骤

# Maven
./mvnw spring-boot:run

# Gradle
./gradlew bootRun

# 或打包运行
./mvnw clean package -DskipTests
java -jar target/demo-0.0.1-SNAPSHOT.jar

测试

# 测试纯文本
curl http://localhost:8080/hello
# 输出: Hello, World!

# 测试 JSON
curl http://localhost:8080/hello/json?name=SpringBoot
# 输出: {"message":"Hello, SpringBoot!"}

预期输出

启动日志关键行：

Started DemoApplication in 1.234 seconds (process running for 1.5)

访问接口返回 200 OK，响应体为 Hello, World!。