Build RESTful APIs with Spring MVC: Swagger

#Visualizes REST APIs with Swagger

Swagger is widely used for visualizing APIs, and with Swagger UI it provides online sandbox for frontend developers.

Visualizes REST APIs

SpringFox project provides Swagger support for Spring based REST APIs.

1. Add springfox to dependencies.

   <!-- SpringFox Swagger UI -->
    <dependency>
    	<groupId>io.springfox</groupId>
    	<artifactId>springfox-swagger2</artifactId>
    	<version>${springfox.version}</version>
    </dependency>
   
    <dependency>
    	<groupId>io.springfox</groupId>
    	<artifactId>springfox-swagger-ui</artifactId>
    	<version>${springfox.version}</version>
    </dependency>

   springfox-swagger-ui provides static Javascript UI for visualizing the Swagger schema definitions.

2. Add a @Configuration class to enable Swagger.

   @Configuration
    @EnableSwagger2
    public class SwaggerConfig {
   
    	[@Bean](http://my.oschina.net/bean)
    	public Docket postsApi() {
    		return new Docket(DocumentationType.SWAGGER_2)
    				.groupName("public-api")
    				.apiInfo(apiInfo())
    				.select()
    				.paths(postPaths())
    				.build();
    	}
   
    	private Predicate<String> postPaths() {
    		return or(
    				regex("/api/posts.*"),
    				regex("/api/comments.*")
    		);
    	}
   
    	private ApiInfo apiInfo() {
    		return new ApiInfoBuilder()
    				.title("SpringMVC Example API")
    				.description("SpringMVC Example API reference for developers")
    				.termsOfServiceUrl("http://hantsy.blogspot.com")
    				.contact("Hantsy Bai")
    				.license("Apache License Version 2.0")
    				.licenseUrl("https://github.com/springfox/springfox/blob/master/LICENSE")
    				.version("2.0")
    				.build();
    	}
   
    }

   When the application starts up, it will scan all Controllers and generate Swagger schema definition at runtime, Swagger UI will read definitions and render user friendly UI for REST APIs.

3. View REST APIs in swagger ui.

   Starts up this application via command line.

   mvn tomcat7:run //or mvn spring-boot:run

   Open browser and navigate http://localhost:8080/angularjs-springmvc-sample/swagger-ui.html.

   You will see the screen like the following.

Documents REST APIs

In the above steps, the Swagger schema definition is generated at runtime, you can get the content via link:http://localhost:8080/angularjs-springmvc-sample/v2/api-docs?group=public-api. You will see the complete Swagger schema definition.

You can save this page content as a json file and upload to http://editor.swagger.io and edit it online.

The Swagger schema definition generation will consume lots of system resourcs at runtime.

Combined with Springfox, Swagger2Markup project, and Spring RestDocs, the Swagger schema definition can be converted to asciidocs, and with asciidoctor-maven-plugin, the asciidocs can be generated into static HTML5 or PDF files.

1. Add swagger2-markup-maven-plugin into pom.xml file.

   <!-- First, use the swagger2markup plugin to generate asciidoc -->
    <plugin>
    	<groupId>io.github.swagger2markup</groupId>
    	<artifactId>swagger2markup-maven-plugin</artifactId>
    	<version>${swagger2markup.version}</version>
    	<dependencies>
    		<dependency>
    			<groupId>io.github.swagger2markup</groupId>
    			<artifactId>swagger2markup-import-files-ext</artifactId>
    			<version>${swagger2markup.version}</version>
    		</dependency>
    		<dependency>
    			<groupId>io.github.swagger2markup</groupId>
    			<artifactId>swagger2markup-spring-restdocs-ext</artifactId>
    			<version>${swagger2markup.version}</version>
    		</dependency>
    	</dependencies>
    	<configuration>
    		<swaggerInput>${swagger.input}</swaggerInput>
    		<outputDir>${generated.asciidoc.directory}</outputDir>
    		<config>
    			<swagger2markup.markupLanguage>ASCIIDOC</swagger2markup.markupLanguage>
    			<swagger2markup.pathsGroupedBy>TAGS</swagger2markup.pathsGroupedBy>
   
    			<swagger2markup.extensions.dynamicOverview.contentPath>${project.basedir}/src/docs/asciidoc/extensions/overview</swagger2markup.extensions.dynamicOverview.contentPath>
    			<swagger2markup.extensions.dynamicDefinitions.contentPath>${project.basedir}/src/docs/asciidoc/extensions/definitions</swagger2markup.extensions.dynamicDefinitions.contentPath>
    			<swagger2markup.extensions.dynamicPaths.contentPath>${project.basedir}/src/docs/asciidoc/extensions/paths</swagger2markup.extensions.dynamicPaths.contentPath>
    			<swagger2markup.extensions.dynamicSecurity.contentPath>${project.basedir}src/docs/asciidoc/extensions/security/</swagger2markup.extensions.dynamicSecurity.contentPath>
   
    			<swagger2markup.extensions.springRestDocs.snippetBaseUri>${swagger.snippetOutput.dir}</swagger2markup.extensions.springRestDocs.snippetBaseUri>
    			<swagger2markup.extensions.springRestDocs.defaultSnippets>true</swagger2markup.extensions.springRestDocs.defaultSnippets>
    		</config>
    	</configuration>
    	<executions>
    		<execution>
    			<phase>test</phase>
    			<goals>
    				<goal>convertSwagger2markup</goal>
    			</goals>
    		</execution>
    	</executions>
    </plugin>

   The convertSwagger2markup goal will convert Swagger schema definition into asciidocs.

2. Add asciidoctor-maven-plugin into pom.xml file.

   <!-- Run the generated asciidoc through Asciidoctor to generate
    other documentation types, such as PDFs or HTML5 -->
    <plugin>
    	<groupId>org.asciidoctor</groupId>
    	<artifactId>asciidoctor-maven-plugin</artifactId>
    	<version>1.5.3</version>
    	<!-- Include Asciidoctor PDF for pdf generation -->
    	<dependencies>
    		<dependency>
    			<groupId>org.jruby</groupId>
    			<artifactId>jruby-complete</artifactId>
    			<version>${jruby.version}</version>
    		</dependency>
    		<dependency>
    			<groupId>org.asciidoctor</groupId>
    			<artifactId>asciidoctorj-pdf</artifactId>
    			<version>${asciidoctorj-pdf.version}</version>
    		</dependency>
    	</dependencies>
    	<!-- Configure generic document generation settings -->
    	<configuration>
    		<sourceDirectory>${asciidoctor.input.directory}</sourceDirectory>
    		<sourceDocumentName>index.adoc</sourceDocumentName>
   
    		<sourceHighlighter>coderay</sourceHighlighter>
    		<attributes>
    			<doctype>book</doctype>
    			<toc>left</toc>
    			<toclevels>3</toclevels>
    			<numbered></numbered>
    			<hardbreaks></hardbreaks>
    			<sectlinks></sectlinks>
    			<sectanchors></sectanchors>
    			<generated>${generated.asciidoc.directory}</generated>
    		</attributes>
    	</configuration>
    	<!-- Since each execution can only handle one backend, run
    	separate executions for each desired output type -->
    	<executions>
    		<execution>
    			<id>output-html</id>
    			<phase>test</phase>
    			<goals>
    				<goal>process-asciidoc</goal>
    			</goals>
    			<configuration>
    				<backend>html5</backend>
    				<outputDirectory>${asciidoctor.html.output.directory}</outputDirectory>
    			</configuration>
    		</execution>
   
    		<execution>
    			<id>output-pdf</id>
    			<phase>test</phase>
    			<goals>
    				<goal>process-asciidoc</goal>
    			</goals>
    			<configuration>
    				<backend>pdf</backend>
    				<outputDirectory>${asciidoctor.pdf.output.directory}</outputDirectory>
    			</configuration>
    		</execution>              
    	</executions>
    </plugin>

   asciidoctor-maven-plugin will generate the asciidocs into HTML5 and PDF files.

3. Add spring-restdocs support.

   spring-restdocs will generate the sample code snippets from test, which can be combined into the final docs.

   Add related dependencies into pom.xml file.

   <dependency>
        <groupId>io.github.swagger2markup</groupId>
        <artifactId>swagger2markup-spring-restdocs-ext</artifactId> 
        <version>${swagger2markup.version}</version>
        <scope>test</scope>
    </dependency>
   
    <dependency>
        <groupId>org.springframework.restdocs</groupId>
        <artifactId>spring-restdocs-mockmvc</artifactId>
        <scope>test</scope>
    </dependency>

   Write test codes to generate sample code snippets.

   @WebAppConfiguration
    @RunWith(SpringRunner.class)
    @SpringBootTest(classes = {Application.class, SwaggerConfig.class})
    public class MockMvcApplicationTest {
   
    	String outputDir = System.getProperty("io.springfox.staticdocs.outputDir");
    	String snippetsDir = System.getProperty("io.springfox.staticdocs.snippetsOutputDir");
    	String asciidocOutputDir = System.getProperty("generated.asciidoc.directory");
   
    	@Rule
    	public final JUnitRestDocumentation restDocumentation = new JUnitRestDocumentation(System.getProperty("io.springfox.staticdocs.snippetsOutputDir"));
   
    	@Inject
    	private WebApplicationContext context;
   
    	@Inject
    	private ObjectMapper objectMapper;
   
    	@Inject
    	private PostRepository postRepository;
   
    	private MockMvc mockMvc;
   
    	private Post savedIdentity;
   
    	@Before
    	public void setUp() {
    		this.mockMvc = webAppContextSetup(this.context)
    				.apply(documentationConfiguration(this.restDocumentation))
    				.alwaysDo(document("{method-name}",
    						preprocessRequest(prettyPrint()),
    						preprocessResponse(prettyPrint())))
    				.build();
   
    		savedIdentity = postRepository.save(newEntity());
    	}
   
    	@Test
    	public void createSpringfoxSwaggerJson() throws Exception {
    		//String designFirstSwaggerLocation = Swagger2MarkupTest.class.getResource("/swagger.yaml").getPath();
   
    		MvcResult mvcResult = this.mockMvc.perform(get("/v2/api-docs")
    				.accept(MediaType.APPLICATION_JSON))
    				.andDo(
    						SwaggerResultHandler.outputDirectory(outputDir)
    						.build()
    				)
    				.andExpect(status().isOk())
    				.andReturn();
   
    		//String springfoxSwaggerJson = mvcResult.getResponse().getContentAsString();
    		//SwaggerAssertions.assertThat(Swagger20Parser.parse(springfoxSwaggerJson)).isEqualTo(designFirstSwaggerLocation);
    	}
   
    	//    @Test
    	//    public void convertToAsciiDoc() throws Exception {
    	//        this.mockMvc.perform(get("/v2/api-docs")
    	//                .accept(MediaType.APPLICATION_JSON))
    	//                .andDo(
    	//                        Swagger2MarkupResultHandler.outputDirectory("src/docs/asciidoc")
    	//                        .withExamples(snippetsDir).build())
    	//                .andExpect(status().isOk());
    	//    }
   
    	@Test
    	public void getAllPosts() throws Exception {
    		this.mockMvc
    				.perform(
    						get("/api/posts/{id}", savedIdentity.getId())
    						.accept(MediaType.APPLICATION_JSON)
    				)
    				//.andDo(document("get_a_post", preprocessResponse(prettyPrint())))
    				.andExpect(status().isOk());
    	}
   
    	@Test
    	public void getAllIdentities() throws Exception {
    		this.mockMvc
    				.perform(
    						get("/api/posts")
    						.accept(MediaType.ALL)
    				)
    				//.andDo(document("get_all_posts"))
    				.andExpect(status().isOk());
    	}
   
    	@Test
    	public void createPost() throws Exception {
    		this.mockMvc
    				.perform(
    						post("/api/posts")
    						.contentType(MediaType.APPLICATION_JSON)
    						.content(newEntityAsJson())
    				)
    				//.andDo(document("create_a_new_post"))
    				.andExpect(status().isCreated());
    	}
   
    	@Test
    	public void updatePost() throws Exception {
    		this.mockMvc
    				.perform(
    						put("/api/posts/{id}", savedIdentity.getId())
    						.contentType(MediaType.APPLICATION_JSON)
    						.content(newEntityAsJson())
    				)
    				//.andDo(document("update_an_existing_post"))
    				.andExpect(status().isNoContent());
    	}
   
    	@Test
    	public void deletePost() throws Exception {
    		this.mockMvc
    				.perform(
    						delete("/api/posts/{id}", savedIdentity.getId())
    						.contentType(MediaType.APPLICATION_JSON)
    				)
    				//.andDo(document("delete_an_existing_post"))
    				.andExpect(status().isNoContent());
    	}
   
    	private Post newEntity() {
    		Post post = new Post();
    		post.setTitle("test title");
    		post.setContent("test content");
   
    		return post;
    	}
   
    	private String newEntityAsJson() throws JsonProcessingException {
    		return objectMapper.writeValueAsString(newEntity());
    	}
   
    }

4. Run mvn clean verify to execute all tests and generate HTML5 and PDF file for the REST APIs.

   Open \target\asciidoc\html\index.html in browser, it looks like.

   Open \target\asciidoc\pdf\index.pdf in Pdf viewer, it looks like.

##Source Code

Check out sample codes from my github account.

git clone https://github.com/hantsy/angularjs-springmvc-sample

Or the Spring Boot version:

git clone https://github.com/hantsy/angularjs-springmvc-sample-boot

Read the live version of thess posts from Gitbook:Building RESTful APIs with Spring MVC.