Swagger - 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.javahubpoint.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.javahubpoint.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.javahubpoint.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.javahubpoint.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.javahubpoint.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.javahubpoint</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.javahubpoint'
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 −

mvn clean install

After “BUILD SUCCESS”, you can find the JAR file under the target directory.

For Gradle, you can use the command as shown here −

gradle clean build

After “BUILD SUCCESSFUL”, you can find the JAR file under the build/libs directory.

Now, run the JAR file by using the command shown here −

java –jar <JARFILE> 

Now, the application will start on the Tomcat port 8080 as shown −

Started Application on Tomcat Port 8080

Now, hit the URL in your web browser and see the Swagger API functionalities.

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