[JAVA] I tried to get started with Swagger using Spring Boot

You will be in charge of the back end and front end within the team, I will be in charge of the front side.

I wanted you to prepare only the API first, so when I tried using Swagger, it was a lot easier.

After investigating how to use it, it seems that there are many ways to do it. I decided to write it down, including the arrangement. This time, I will use Spring Boot to transcribe the design document with a bottom-up approach.

Bottom-up approach: transcribing from source code

The bottom-up approach is to create a Swagger based on the source code. The following two points are good about the bottom-up approach.

--Since the design document is completed based on the source code, it becomes difficult for the document and the code to deviate from each other. --Eliminate the hassle of writing the source code after creating the design document

There is a story like "Isn't it a problem if a rework occurs?" Since only the API mouth is defined first, I think that the work time is not much different from making it as a document.

When I checked this time, it seems that most things can be done with Spring Boot and Swagger, so I wanted to use it positively in the future.

The code created this time can be found at here.

Spring Boot settings

Introducing Spring Fox

By using Spring Fox, the API design document is transcribed from the source code.

To install Spring Fox, it is OK if you solve the following dependencies.


repositories {

dependencies {
    compile "io.springfox:springfox-swagger2:2.9.2"
    compile 'io.springfox:springfox-swagger-ui:2.9.2'  //To use Swagger UI

Enable Spring Fox in Spring Boot


package com.example.springbootswagger;

//import statement omitted

public class SpringBootSwaggerApplication {

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

    //Docket is an API provided by Spring Fox. Requires settings to transcribe with Swagger
    public Docket petApi() {
        return new Docket(DocumentationType.SWAGGER_2)
                .select() // ApiSelector :Select the API to transcribe with Swagger.
                    .paths(PathSelectors.ant("/pets/**")) //Swagger will only wake up anything that matches the specified path
                    .build() //Create ApiSelector
                .useDefaultResponseMessages(false) //It automatically assigns an undefined status code. This time, turn off automatic grant
                .apiInfo(apiInfo()); //Set API information

    private ApiInfo apiInfo() {
        return new ApiInfoBuilder()
                .title("Pet Service")
                .description("This is a pet service api")

If you look at the official guide, here are other settings that return a common response message, You can make security-related settings. This time, the volume will be large, so I will omit it.

When making it into production, it is necessary to set viewing restrictions. How do you do it? Let's check it out next time.


Now that the settings for Spring Boot and Spring Fox have been completed, let Swagger actually transcribe them. Annotate various resources.

If you write as follows in the simplest state, you can see the specifications for the time being.


package com.example.springbootswagger;
//import statement omitted

public class PetResource {

    public List<Map<String, String>> pets() {
        return new ArrayList<>();

    public Map<String, String> pet(@PathVariable String id) {
        return new HashMap<>();

    public void updatePet(@PathVariable String id) {

    public int insertPet() {
        return 1;

    public void deletePet() {

Normally, if you add annotations to each resource of the API, It just transcribes it into Swagger. It's amazing.

How to check Swagger UI

When you start the application and access http: //localhost:8080/swagger-ui.html The following screen will be displayed.


By the way, even if you don't define swagger-ui.html If gradle resolves the dependency of ʻio.springfox: springfox-swagger-ui: 2.9.2` It seems that it will be generated without permission.

Define Swagger in more detail

If it is the annotation of the Controller layer provided by Spring, It will be reflected in Swagger accordingly. For example, if you add @PathVariable, it will be reflected as follows.


There are also essential items. In addition, if you add an annotation provided by Swagger instead of Spring, You will have a more friendly API design document.

Give an overview of each resource


//import statement omitted

public class PetResource {

    // @Set resource overview with ApiOperation
    @ApiOperation(value = "This Resource fetch all reserved pets")
    @GetMapping(produces = MediaType.APPLICATION_JSON_UTF8_VALUE)
    public List<PetDto> pets() {
        return new ArrayList<>();


Add a response pattern


//import statement omitted

public class PetResource {

    @ApiOperation(value = "This Resource fetch a pet by id")
    //You can define multiple responses with ApiResponses. Required items for code and message.
    @ApiResponses(value = {@ApiResponse(code = 400, message = "Invalid Id supplied", response = ErrorDto.class), @ApiResponse(code = 404, message = "Pet not found")})
    @GetMapping(value = "{id}", produces = MediaType.APPLICATION_JSON_UTF8_VALUE)
    public PetDto pet(@PathVariable String id) {
        return new PetDto();



This time, I omitted the security related items due to the volume. I think I'll summarize it in another article. After that, as I wrote in the middle, it is necessary to devise something that can not be shown in production. I'm curious about how to do it.

I'm using SpringBoot, so should I do something with Spring Security?


** Click here for various settings when installing. ** ** http://springfox.github.io/springfox/docs/current/#getting-started

** Click here for Swagger annotations. ** ** https://github.com/swagger-api/swagger-core/wiki/annotations

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