Here we will see how to enable swagger in spring boot application.

Technologies:

• Spring Boot Starter 2.2.5
• Swagger 2.7.0
• Swagger UI 2.7.0
• Gradle

Enable Swagger in Spring Boot:

Enabling swagger in spring boot gives us better accessibility of rest endpoints, we can group all rest points at a single dashboard and access them with default JSON templates.

Application Structure:

Dependencies:

compile group: 'io.springfox', name: 'springfox-swagger2', version: '2.7.0'
compile group: 'io.springfox', name: 'springfox-swagger-ui', version: '2.7.0'

<dependency>
    <groupId>io.springfox</groupId>
    <artifactId>springfox-swagger2</artifactId>
</dependency>
<dependency>
    <groupId>io.springfox</groupId>
    <artifactId>springfox-swagger-ui</artifactId>
</dependency>

plugins {
  id 'org.springframework.boot' version '2.2.5.RELEASE'
  id 'io.spring.dependency-management' version '1.0.9.RELEASE'
  id 'java'
}

group = 'com.onlinetutorialspoint'
version = '0.0.1-SNAPSHOT'
sourceCompatibility = '1.8'

repositories {
  mavenCentral()
}

dependencies {
  implementation 'org.springframework.boot:spring-boot-starter-web'
  testCompile('org.springframework.boot:spring-boot-starter-test')
  testCompile 'junit:junit:4.12'
  compile group: 'io.springfox', name: 'springfox-swagger2', version: '2.7.0'
  compile group: 'io.springfox', name: 'springfox-swagger-ui', version: '2.7.0'
}

Create a sample controller which will reverse the string, which we have passed.

package com.onlinetutorialspoint.controller;

import com.onlinetutorialspoint.domains.Response;
import com.onlinetutorialspoint.service.HelloService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.util.Assert;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.ResponseBody;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class HelloController {

    @Autowired
    HelloService helloService;

    @GetMapping("/api/{message}")
    @ResponseBody
    public ResponseEntity<Response> reverse(@PathVariable("message") String message) {
        Assert.notNull(message, "The message should not be null!");
        Response response= helloService.reverse(message);
        return new ResponseEntity<Response>(response, HttpStatus.OK);
    }
}

Create HelloService class, it will do actual reverse operation.

package com.onlinetutorialspoint.service;

import com.onlinetutorialspoint.domains.Response;
import org.springframework.stereotype.Service;
import org.springframework.util.Assert;

import java.util.List;
import java.util.regex.Pattern;
import java.util.stream.Collectors;

@Service
public class HelloService {
    public Response reverse(String message){
       return Pattern.compile("\\s").splitAsStream(message).reduce((w1, w2) -> w2 + " " + w1).
                map(data->new Response(data)).get();
    }
}

Create domain class; which will act as a response JSON.

package com.onlinetutorialspoint.domains;

import org.springframework.stereotype.Component;

@Component
public class Response {
    private String reversed;

    public Response() {
    }

    public Response(String reversed) {
        this.reversed = reversed;
    }

    public String getReversed() {
        return reversed;
    }
}

Create Spring Boot started class

package com.onlinetutorialspoint;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import springfox.documentation.builders.RequestHandlerSelectors;
import springfox.documentation.spi.DocumentationType;
import springfox.documentation.spring.web.plugins.Docket;
import springfox.documentation.swagger2.annotations.EnableSwagger2;

@SpringBootApplication
@EnableSwagger2
@Configuration
public class SpringBootService {

  public static void main(String[] args) {
    SpringApplication.run(SpringBootService.class, args);
  }
  @Bean
  public Docket productApi() {
    return new Docket(DocumentationType.SWAGGER_2).select()
        .apis(RequestHandlerSelectors.basePackage("com.onlinetutorialspoint")).build();
  }
}

Build and Run:

gradlew build

> Task :test
09:19:49.283 [SpringContextShutdownHook] DEBUG org.springframework.context.support.GenericApplicationContext - Closing org.springframework.context.support.GenericApplicationContext@1c5f2
61f, started on Wed Mar 25 09:19:46 IST 2020

Deprecated Gradle features were used in this build, making it incompatible with Gradle 7.0.
Use '--warning-mode all' to show the individual deprecation warnings.
See https://docs.gradle.org/6.2.2/userguide/command_line_interface.html#sec:command_line_warnings

BUILD SUCCESSFUL in 20s
5 actionable tasks: 4 executed, 1 up-to-date

Run:

gradlew bootRun

> Task :bootRun

  .   ____          _            __ _ _
 /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
 \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
  '  |____| .__|_| |_|_| |_\__, | / / / /
 =========|_|==============|___/=/_/_/_/
 :: Spring Boot ::        (v2.2.5.RELEASE)

2020-03-25 09:23:54.281  INFO 18108 --- [           main] c.o.SpringBootService                    : Starting SpringBootService on DESKTOP-RN4SMHT with PID 18108 (D:\work\sample-spring-a
pplication\build\classes\java\main started by Lenovo in D:\work\sample-spring-application)
2020-03-25 09:23:54.286  INFO 18108 --- [           main] c.o.SpringBootService                    : No active profile set, falling back to default profiles: default
2020-03-25 09:23:56.344  INFO 18108 --- [           main] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat initialized with port(s): 8080 (http)
2020-03-25 09:23:56.359  INFO 18108 --- [           main] o.apache.catalina.core.StandardService   : Starting service [Tomcat]
2020-03-25 09:23:56.360  INFO 18108 --- [           main] org.apache.catalina.core.StandardEngine  : Starting Servlet engine: [Apache Tomcat/9.0.31]
2020-03-25 09:23:56.568  INFO 18108 --- [           main] o.a.c.c.C.[Tomcat].[localhost].[/]       : Initializing Spring embedded WebApplicationContext
2020-03-25 09:23:56.568  INFO 18108 --- [           main] o.s.web.context.ContextLoader            : Root WebApplicationContext: initialization completed in 2196 ms
2020-03-25 09:23:57.274  INFO 18108 --- [           main] pertySourcedRequestMappingHandlerMapping : Mapped URL path [/v2/api-docs] onto method [springfox.documentation.swagger2.web.Swag
ger2Controller#getDocumentation(String, HttpServletRequest)]
2020-03-25 09:23:57.554  INFO 18108 --- [           main] o.s.s.concurrent.ThreadPoolTaskExecutor  : Initializing ExecutorService 'applicationTaskExecutor'
2020-03-25 09:23:57.826  INFO 18108 --- [           main] d.s.w.p.DocumentationPluginsBootstrapper : Context refreshed
2020-03-25 09:23:57.850  INFO 18108 --- [           main] d.s.w.p.DocumentationPluginsBootstrapper : Found 1 custom documentation plugin(s)
2020-03-25 09:23:57.919  INFO 18108 --- [           main] s.d.s.w.s.ApiListingReferenceScanner     : Scanning for api listing references
2020-03-25 09:23:58.119  INFO 18108 --- [           main] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat started on port(s): 8080 (http) with context path ''
2020-03-25 09:23:58.123  INFO 18108 --- [           main] c.o.SpringBootService                    : Started SpringBootService in 4.505 seconds (JVM running for 5.189)
<=========----> 75% EXECUTING [2m 11s]

Access the application with swagger UI endpoint :

http://localhost:8080/swagger-ui.htm

Click on the hello-controller endpoint and you can see the below API details.

References:

• Spring Boot Rest Web Services Example
• Swagger Documentation

Happy Learning 🙂