首先，在pom.xml中添加依赖：

<dependencies>
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
    </dependency>
    <dependency>
        <groupId>io.springfox</groupId>
        <artifactId>springfox-boot-starter</artifactId>
        <version>3.0.0</version>
    </dependency>
</dependencies>

创建一个配置类SwaggerConfig.java：

package org.example.testdoc.config;

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import springfox.documentation.builders.ApiInfoBuilder;
import springfox.documentation.builders.PathSelectors;
import springfox.documentation.builders.RequestHandlerSelectors;
import springfox.documentation.service.ApiInfo;
import springfox.documentation.spi.DocumentationType;
import springfox.documentation.spring.web.plugins.Docket;

@Configuration
public class SwaggerConfig {
    @Bean
    public Docket api() {
        return new Docket(DocumentationType.SWAGGER_2)
                .apiInfo(apiInfo())
                .select()
                .apis(RequestHandlerSelectors.basePackage("org.example.testdoc.controller"))
                .paths(PathSelectors.any())
                .build();
    }

    private ApiInfo apiInfo() {
        return new ApiInfoBuilder()
                .title("Springfox Swagger3 Example")
                .description("This is an example of using Springfox Swagger3 to generate API documentation.")
                .version("1.0")
                .build();
    }
}

创建一个控制器类HelloController.java：

package com.example.demo.controller;

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

@RestController
public class HelloController {
    @GetMapping("/hello")
    public String hello() {
        return "Hello, Spring Boot!";
    }
}

ExampleController类

package org.example.testdoc.controller;

import io.swagger.annotations.Api;
import io.swagger.annotations.ApiOperation;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;

@Api(value = "Example Controller", tags = "example")
@RestController
public class ExampleController {
    @ApiOperation(value = "Get example data", notes = "This API returns example data.")
    @GetMapping("/example")
    public String getExampleData() {
        return "Hello, World!";
    }
}

主类：

package org.example.testdoc;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import springfox.documentation.oas.annotations.EnableOpenApi;

@SpringBootApplication
@EnableOpenApi
public class TestdocApplication {

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

}

查看结果：访问Swagger UI

http://localhost:8080/swagger-ui/index.html