Getting started with microservices – API documentation

Use Spring REST Docs to document your services. It’s a powerful framework which makes sure that the Service logic is always inline with the documentation. In order to do so, you would have to write integration tests for your services.

If there is any mismatch in the documentation & service behavior, the tests will fail.

Here is a sample example for generating the docs for a maven project.

Add this dependency in your pom:

<dependency>
    <groupId>org.springframework.data</groupId>
    <artifactId>spring-data-rest-webmvc</artifactId>
    <version>2.6.6.RELEASE</version>
</dependency>

and add the asciidoc plugin under build.plugins tag:

<plugin> 
        <groupId>org.asciidoctor</groupId>
        <artifactId>asciidoctor-maven-plugin</artifactId>
        <version>1.5.3</version>
        <executions>
            <execution>
                <id>generate-docs</id>
                <phase>prepare-package</phase> 
                <goals>
                    <goal>process-asciidoc</goal>
                </goals>
                <configuration>
                    <backend>html</backend>
                    <doctype>book</doctype>
                </configuration>
            </execution>
        </executions>
        <dependencies>
            <dependency> 
                <groupId>org.springframework.restdocs</groupId>
                <artifactId>spring-restdocs-asciidoctor</artifactId>
                <version>1.2.0.RELEASE</version>
            </dependency>
        </dependencies>
    </plugin>    

Now let’s take a sample controller which we want to document:

package com.hospital.user.service.controller;

import org.springframework.hateoas.Resource;
import org.springframework.http.HttpStatus;
import org.springframework.http.MediaType;
import org.springframework.http.ResponseEntity;
import org.springframework.security.crypto.bcrypt.BCryptPasswordEncoder;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;

import com.hospital.user.service.entity.User;
import com.hospital.user.service.exception.UserNotFoundException;
import com.hospital.user.service.repository.UserCrudRepository;
import com.hospital.user.service.resource.assembler.UserResourceAssembler;

@Controller
@RequestMapping("/api/user")
public class SampleController {


final UserCrudRepository userRepository;


final UserResourceAssembler userResourceAssembler;

final BCryptPasswordEncoder  passwordEncoder;

public SampleController(UserCrudRepository userCrudRepository, UserResourceAssembler userResourceAssembler, BCryptPasswordEncoder passwordEncoder){
    this.userRepository = userCrudRepository;
    this.userResourceAssembler = userResourceAssembler;
    this.passwordEncoder = passwordEncoder;
}

@RequestMapping(method = RequestMethod.GET, value = "/{userId}", produces = { MediaType.APPLICATION_JSON_VALUE})
ResponseEntity<Resource<User>> getUser(@PathVariable String userId){
    User user = (User) this.userRepository.findOne(userId);
    if(user==null){
        throw new UserNotFoundException("No record found for userid"+ userId);
    }
    Resource<User> resource = this.userResourceAssembler.toResource(user);
    return new ResponseEntity<Resource<User>>(resource, HttpStatus.OK);
 }
}

Now write a test case for the service:

package com.hospital.user.service;

import org.junit.Before;
import org.junit.Rule;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.context.annotation.ComponentScan;
import org.springframework.restdocs.JUnitRestDocumentation;
import org.springframework.restdocs.mockmvc.RestDocumentationResultHandler;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
import org.springframework.test.context.web.WebAppConfiguration;
import org.springframework.test.web.servlet.MockMvc;
import org.springframework.test.web.servlet.setup.MockMvcBuilders;
import org.springframework.web.context.WebApplicationContext;
import org.springframework.web.servlet.config.annotation.EnableWebMvc;


import static org.springframework.restdocs.operation.preprocess.Preprocessors.prettyPrint;
import static org.springframework.restdocs.operation.preprocess.Preprocessors.preprocessRequest;

import static org.springframework.restdocs.operation.preprocess.Preprocessors.preprocessResponse;

import static org.springframework.restdocs.mockmvc.MockMvcRestDocumentation.document;
import static org.springframework.restdocs.mockmvc.MockMvcRestDocumentation.documentationConfiguration;

import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.status;

import static org.springframework.restdocs.mockmvc.RestDocumentationRequestBuilders.get;

import static org.springframework.restdocs.headers.HeaderDocumentation.headerWithName;
import static org.springframework.restdocs.headers.HeaderDocumentation.responseHeaders;

import static org.springframework.restdocs.payload.PayloadDocumentation.fieldWithPath;
import static org.springframework.restdocs.payload.PayloadDocumentation.responseFields;

@RunWith(SpringJUnit4ClassRunner.class)
@WebAppConfiguration
@EnableWebMvc
@ComponentScan( basePackages = { "com.hospital.user.service" } )
@SpringBootTest
public class SampleControllerTest {

private RestDocumentationResultHandler documentationHandler;

@Rule public final JUnitRestDocumentation restDocumentation = new JUnitRestDocumentation("target/generated-snippets");

 @Autowired private WebApplicationContext context;
    private MockMvc mockMvc;
    
    @Before
    public void setUp(){
        
        this.documentationHandler = document("{method-name}", //this will create files with the test method name
                preprocessRequest(prettyPrint()), // to print the request 
                preprocessResponse(prettyPrint()));

            this.mockMvc = MockMvcBuilders.webAppContextSetup(this.context)
                .apply(documentationConfiguration(this.restDocumentation)
                        .uris()
                        //.withScheme("https") Specify this for https
                        .withHost("recruitforceuserservice") //Define the host name
                        .withPort(8443)
                    )
                .alwaysDo(this.documentationHandler)
                .build();
    }
    
    @Test
    public void getUser() throws Exception {
            // tag::links[]
            this.mockMvc.perform(get("/api/user/"+"591310c3d5eb3a37183ab0d3").header("Authorization",
                    "Bearer eyJhbGciOiJIUzUxMiJ9.eyJzdWIiOiJiaGFyZHdhai5uaXRpc2gxOSIsInJvbGVzIjpbIkFETUlOIl0sImlzcyI6Imh0dHA6Ly9ob3NwaXRhbC1jbG91ZC5jb20iLCJpYXQiOjE1MDExNTA3NDcsImV4cCI6MTUwMTE1MTY0N30.NPumYw9mslHdJjaaodsIzKX4y0Udbf2Co1kVOXBEaqNdEUIUSwgwQZn23TMWVsehudlwTu4KgCU2ZHXXccCDIQ"))
                .andExpect(status().isOk())
                .andDo(this.documentationHandler.document(
                        
                        responseHeaders(
                                headerWithName("Content-Type").description("The Content-Type of the payload: `application/json`") // Asserts that the response should have this header.
                                ),
                        
                        responseFields(
                                fieldWithPath("username").description("Unique name for the record"), // Asserts that the response should have this field
                                fieldWithPath("password").description("password of the user"),
                                fieldWithPath("securityAnswer").description("Security answer which would be used to validate the user while the password is reset."),
                                fieldWithPath("securityQuestion").description("Security question to reset the password"),
                                fieldWithPath("email").description("Email of the user"),
                                fieldWithPath("roles").description("Assigned roles of the user"),
                                fieldWithPath("id").description("Unique identifier of an user"),
                                fieldWithPath("_links").ignored()
                        )
                        )); 
    }

}

Please follow this reference for more details:
http://docs.spring.io/spring-restdocs/docs/current/reference/html5/

if you want to reproduce, please indicate the source:
Getting started with microservices – API documentation - CodeDay