Spring Boot - Enabling Swagger2

Swagger2 is an open source project used to generate the REST API documents for RESTful web services. It provides a user interface to access our RESTful web services via the web browser.

To enable the Swagger2 in Spring Boot application, you need to add the following dependencies in our build configurations file.

<dependency>
   <groupId>io.springfox</groupId>
   <artifactId>springfox-swagger2</artifactId>
   <version>2.7.0</version>
</dependency>
<dependency>
   <groupId>io.springfox</groupId>
   <artifactId>springfox-swagger-ui</artifactId>
   <version>2.7.0</version>
</dependency>

For Gradle users, add the following dependencies in your build.gradle file.

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

Now, add the @EnableSwagger2 annotation in your main Spring Boot application. The @EnableSwagger2 annotation is used to enable the Swagger2 for your Spring Boot application.

The code for main Spring Boot application is shown below −

package com.maixuanviet.swaggerdemo;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import springfox.documentation.swagger2.annotations.EnableSwagger2;

@SpringBootApplication
@EnableSwagger2
public class SwaggerDemoApplication {
   public static void main(String[] args) {
      SpringApplication.run(SwaggerDemoApplication.class, args);
   }
}

Next, create Docket Bean to configure Swagger2 for your Spring Boot application. We need to define the base package to configure REST API(s) for Swagger2.

   @Bean
   public Docket productApi() {
      return new Docket(DocumentationType.SWAGGER_2).select()
         .apis(RequestHandlerSelectors.basePackage("com.maixuanviet.swaggerdemo")).build();
   }

Now, add this bean in main Spring Boot application class file itself and your main Spring Boot application class will look as shown below −

package com.maixuanviet.swaggerdemo;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.annotation.Bean;

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

Now, add the below Spring Boot Starter Web dependency in your build configuration file to write a REST Endpoints as shown below −

Maven users can add the following dependency in your pom.xml file −

<dependency>
   <groupId>org.springframework.boot</groupId>
   <artifactId>spring-boot-starter-web</artifactId>
</dependency>

Gradle users can add the following dependency in build.gradle file −

compile('org.springframework.boot:spring-boot-starter-web')

Now, the code to build two simple RESTful web services GET and POST in Rest Controller file is shown here −

package com.maixuanviet.swaggerdemo;

import java.util.ArrayList;
import java.util.List;

import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RestController;

@RestController
public class SwaggerAPIController {
   @RequestMapping(value = "/products", method = RequestMethod.GET)
   public List<String> getProducts() {
      List<String> productsList = new ArrayList<>();
      productsList.add("Honey");
      productsList.add("Almond");
      return productsList;
   }
   @RequestMapping(value = "/products", method = RequestMethod.POST)
   public String createProduct() {
      return "Product is saved successfully";
   }
}

The complete build configuration file is given below −

Maven – 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 
   http://maven.apache.org/xsd/maven-4.0.0.xsd">
   <modelVersion>4.0.0</modelVersion>

   <groupId>com.maixuanviet</groupId>
   <artifactId>swagger-demo</artifactId>
   <version>0.0.1-SNAPSHOT</version>
   <packaging>jar</packaging>
   <name>swagger-demo</name>
   <description>Demo project for Spring Boot</description>

   <parent>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-parent</artifactId>
      <version>1.5.9.RELEASE</version>
      <relativePath /> <!-- lookup parent from repository -->
   </parent>

   <properties>
      <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
      <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
      <java.version>1.8</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>
      
      <dependency>
         <groupId>io.springfox</groupId>
         <artifactId>springfox-swagger2</artifactId>
         <version>2.7.0</version>
      </dependency>

      <dependency>
         <groupId>io.springfox</groupId>
         <artifactId>springfox-swagger-ui</artifactId>
         <version>2.7.0</version>
      </dependency>
   </dependencies>

   <build>
      <plugins>
         <plugin>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-maven-plugin</artifactId>
         </plugin>
      </plugins>
   </build>
   
</project>

Gradle – build.gradle

buildscript {
   ext {
      springBootVersion = '1.5.9.RELEASE'
   }
   repositories {
      mavenCentral()
   }
   dependencies {
      classpath("org.springframework.boot:spring-boot-gradle-plugin:${springBootVersion}")
   }
}
apply plugin: 'java'
apply plugin: 'eclipse'
apply plugin: 'org.springframework.boot'

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

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

You can create an executable JAR file, and run the Spring Boot application by using the following Maven or Gradle commands.

For Maven, you can use the command shown here −