Document RESTful services by combining hand-written documentation with auto-generated snippets produced with Spring MVC Test.

Introduction

The aim of Spring REST Docs is to help you to produce documentation for your RESTful services that is accurate and readable.

Writing high-quality documentation is difficult. One way to ease that difficulty is to use tools that are well-suited to the job. To this end, Spring REST Docs uses Asciidoctor. Asciidoctor processes plain text and produces HTML styled and layed out to suit your needs.

Spring REST Docs makes use of snippets produced by tests written with Spring MVC Test. This test-driven approach helps to guarantee the accuracy of your service’s documentation. If a snippet is incorrect the test that produces it will fail.

Documenting a RESTful service is largely about describing its resources. Two key parts of each resource’s description are the details of the HTTP requests that it consumes and the HTTP responses that it produces. Spring REST Docs allows you to work with these resources and the HTTP requests and responses, shielding your documentation from the inner-details of your service’s implementation. This separation helps you to document your service’s API rather than its implementation. It also frees you to evolve the implementation without having to rework the documentation.

Getting started

This section describes how to get started with Spring REST docs.

Sample applications

If you want to jump straight in, there are two sample applications available. One sample uses Spring HATEOAS and the other uses Spring Data REST. Both samples use Spring REST Docs to produce a detailed API guide and a getting started walkthrough. You can use either Gradle or Maven to build them.

In each sample the source for the documentation can be found in src/main/asciidoc. api-guide.adoc produces an API guide for the service. getting-started-guide.adoc produces a getting started guide that provides an introductory walkthrough.

The code that produces the generated snippets can be found in src/test/java. ApiDocumentation.java produces the snippets for the API guide. GettingStartedDocumentation.java produces the snippets for the getting started guide.

Build configuration

The first step in using Spring REST Docs is to configure your project’s build.

Gradle build configuration

Both sample applications contain build.gradle files that you may wish to use as a reference. The key parts of the configuration are described below.

plugins { (1)
    id "org.asciidoctor.convert" version "1.5.2"
}

dependencies { (2)
    testCompile 'org.springframework.restdocs:spring-restdocs:1.0.0.M1'
}

ext { (3)
    snippetsDir = file('build/generated-snippets')
}

test { (4)
    systemProperty 'org.springframework.restdocs.outputDir', snippetsDir
    outputs.dir snippetsDir
}

asciidoctor { (5)
    attributes 'snippets': snippetsDir
    inputs.dir snippetsDir
    dependsOn test
}
1 Apply the Asciidoctor plugin
2 Add a dependency on spring-restdocs in the testCompile configuration:
3 Configure a property to define the output location for generated snippets:
4 Configure the test task with the org.springframework.restdocs.outputDir system property. This property controls the location into which Spring REST Docs will write the snippets that it generates.
5 Configure the asciidoctor task and define an attribute named snippets. You can then use this attribute when including the generated snippets in your documentation.

Packaging the documentation

You may want to package the generated documentation in your project’s jar file, for example to have it served as static content by Spring Boot. You can do so by configuring the jar task to depend on the asciidoctor task and to copy the generated documentation into the jar’s static directory:

jar {
    dependsOn asciidoctor
    from ("${asciidoctor.outputDir}/html5") {
        into 'static/docs'
    }
}

Maven build configuration

Both sample applications contain pom.xml files that you may wish to use as a reference. The key parts of the configuration are described below.

<dependency> (1)
    <groupId>org.springframework.restdocs</groupId>
    <artifactId>spring-restdocs</artifactId>
    <version>1.0.0.M1</version>
    <scope>test</scope>
</dependency>

<properties> (2)
    <snippetsDirectory>${project.build.directory}/generated-snippets</snippetsDirectory>
</properties>

<build>
    <plugins>
        <plugin> (3)
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-surefire-plugin</artifactId>
            <configuration>
                <includes>
                    <include>**/*Documentation.java</include>
                </includes>
                <systemPropertyVariables>
                    <org.springframework.restdocs.outputDir>
                        ${snippetsDirectory}
                    </org.springframework.restdocs.outputDir>
                </systemPropertyVariables>
            </configuration>
        </plugin>
        <plugin> (4)
            <groupId>org.asciidoctor</groupId>
            <artifactId>asciidoctor-maven-plugin</artifactId>
            <version>1.5.2</version>
            <executions>
                <execution>
                    <id>generate-docs</id>
                    <phase>package</phase> (5)
                    <goals>
                        <goal>process-asciidoc</goal>
                    </goals>
                    <configuration>
                        <backend>html</backend>
                        <doctype>book</doctype>
                        <attributes>
                            <snippets>${snippetsDirectory}</snippets>
                        </attributes>
                    </configuration>
                </execution>
            </executions>
        </plugin>
    </plugins>
</build>
1 Add a dependency on spring-restdocs in the test scope
2 Configure a property to define the output location for generated snippets
3 Configure the SureFire plugin with the org.springframework.restdocs.outputDir system property. This property controls the location into which Spring REST docs will write the snippets that it generates. The plugin is also configured to include files whose names end with Documentation.java:
4 Configure the Asciidoctor plugin and define an attribute named snippets. You can then use this attribute when including the generated snippets in your documentation.
5 If you want to package the documentation in your project’s jar you should use the prepare-package phase.

Packaging the documentation

You may want to package the generated documentation in your project’s jar file, for example to have it served as static content by Spring Boot.

First, configure the Asciidoctor plugin so that it runs in the prepare-package phase, as described above. Now configure Maven’s resources plugin to copy the generated documentation into a location where it’ll be included in the project’s jar:

<plugin> (1)
    <groupId>org.asciidoctor</groupId>
    <artifactId>asciidoctor-maven-plugin</artifactId>
    <!-- … -->
</plugin>
<plugin> (2)
    <artifactId>maven-resources-plugin</artifactId>
    <version>2.7</version>
    <executions>
        <execution>
            <id>copy-resources</id>
            <phase>prepare-package</phase>
            <goals>
                <goal>copy-resources</goal>
            </goals>
            <configuration>
                <outputDirectory>
                    ${project.build.outputDirectory}/static/docs
                </outputDirectory>
                <resources>
                    <resource>
                        <directory>
                            ${project.build.directory}/generated-docs
                        </directory>
                    </resource>
                </resources>
            </configuration>
        </execution>
    </executions>
</plugin>
1 The existing declaration for the Asciidoctor plugin
2 The resource plugin must be declared after the Asciidoctor plugin as they are bound to the same phase and the resource plugin must run after the Asciidoctor plugin.

Generating documentation snippets

Spring REST Docs uses Spring’s MVC Test framework to make requests to the service that you are documenting. It then produces documentation snippets for the result’s request and response.

Setting up Spring MVC test

The first step in generating documentation snippets is to provide an @Before method that creates a MockMvc instance:

@Autowired
private WebApplicationContext context;

private MockMvc mockMvc;

@Before
public void setUp() {
    this.mockMvc = MockMvcBuilders.webAppContextSetup(this.context)
            .apply(documentationConfiguration())
            .build();
}

The MockMvc instance is configured using a RestDocumentationConfigurer. An instance of this class can be obtained from the static documentationConfiguration() method on org.springframework.restdocs.RestDocumentation. RestDocumentationConfigurer applies sensible defaults and also provides an API for customizing the configuration. Refer to the Configuration section for more information.

Invoking the RESTful service

Now that a MockMvc instance has been created, it can be used to invoke the RESTful service and document the request and response.

this.mockMvc.perform(get("/").accept(MediaType.APPLICATION_JSON)) (1)
    .andExpect(status().isOk()) (2)
    .andDo(document("index")); (3)
1 Invoke the root (/) of the service an indicate that an application/json response is required
2 Assert that the service is produced the expected response
3 Document the call to the service, writing the snippets into a directory named index that will be located beneath the configured output directory. The snippets are written by a RestDocumentationResultHandler. An instance of this class can be obtained from the static document method on org.springframework.restdocs.RestDocumentation.

By default, three snippets a written:

  • <output-directory>/index/curl-request.adoc

  • <output-directory>/index/http-request.adoc

  • <output-directory>/index/http-response.adoc

Refer to Documenting your API for more information about these and other snippets that can be produced by Spring REST Docs.

Using the snippets

The generated snippets can be included in your documentation using the include macro. The snippets attribute specified in the build configuration can be used to reference the snippets output directory, for example:

include::{snippets}/index/curl-request.adoc[]

Documenting your API

This section provides more details about using Spring REST Docs to document your API.

Hypermedia

Spring REST Docs provides support for documenting the links in a Hypermedia-based API:

this.mockMvc.perform(get("/").accept(MediaType.APPLICATION_JSON))
    .andExpect(status().isOk())
    .andDo(document("index").withLinks( (1)
            linkWithRel("alpha").description("Link to the alpha resource"), (2)
            linkWithRel("bravo").description("Link to the bravo resource"))); (3)
1 withLinks is used to describe the expected links
2 Expects a link whose rel is alpha. Uses the static linkWithRel method on org.springframework.restdocs.hypermedia.HypermediaDocumentation.
3 Expects a link whose rel is bravo

The result is a snippet named links.adoc that contains a table describing the resource’s links.

When documenting links, the test will fail if an undocumented link is found in the response. Similarly, the test will also fail if a documented link is not found in the response and the link has not be marked as optional.

Two link formats are understood by default:

  • Atom – links are expected to be in an array named links. Used by default when the content type of the response is compatible with application/json.

  • HAL – links are expected to be in a map named _links. Used by default when the content type of the response is compatible with application/hal+json.

If you are using Atom or HAL-format links but with a different content type you can provide one of the built-in LinkExtractor implementations to withLinks. For example:

.andDo(document("index").withLinks(halLinks(), (1)
        linkWithRel("alpha").description("Link to the alpha resource"),
        linkWithRel("bravo").description("Link to the bravo resource")));
1 Indicate that the links are in HAL format using the halLinks static method on org.springframework.restdocs.hypermedia.LinkExtractors.

If your API represents its links in a format other than Atom or HAL you can provide your own implementation of the LinkExtractor interface to extract the links from the response.

Request and response payloads

In addition to the Hypermedia-specific support described above, support for general documentation of request and response payloads is also provided:

this.mockMvc.perform(get("/user/5").accept(MediaType.APPLICATION_JSON))
    .andExpect(status().isOk())
    .andDo(document("index").withResponseFields( (1)
            fieldWithPath("contact").description("The user's contact details"), (2)
            fieldWithPath("contact.email").description("The user's email address"))); (3)
1 withResponseFields is used to describe the expected fields in the response payload. To document a request withRequestFields can be used.
2 Expects a field with the path contact. Uses the static fieldWithPath method on org.springframework.restdocs.payload.PayloadDocumentation.
3 Expects a field with the path contact.email

The result is a snippet that contains a table describing the fields. For requests this snippet is named request-fields.adoc. For responses this snippet is named response-fields.adoc.

When documenting fields, the test will fail if an undocumented field is found in the payload. Similarly, the test will also fail if a documented field is not found in the payload and the field has not be marked as optional. For payloads with a hierarchical structure, when a point in the hierarchy is documented any fields beneath that point are also deemed to have been documented. This means that you do not have to document the entire hierarchy, but you may do so if you wish.

Field paths

When documenting request and response payloads, fields are identified using a path. Paths use . to descend into a child object and [] to identify an array. For example, with this JSON payload:

{
    "a":{
        "b":[
            {
                "c":"one"
            },
            {
                "c":"two"
            },
            {
                "d":"three"
            }
        ]
    }
}

The following paths are all present:

Path Value

a

An object containing b

a.b

An array containing three objects

a.b[]

An array containing three objects

a.b[].c

An array containing the strings one and two

a.b[].d

The string three

Field types

When a field is documented, Spring REST docs will attempt to determine its type by examining the payload. Seven different types are supported:

Type Description

array

The value of each occurrence of the field is an array

boolean

The value of each occurrence of the field is a boolean (true or false)

object

The value of each occurrence of the field is an object

number

The value of each occurrence of the field is a number

null

The value of each occurrence of the field is null

string

The value of each occurrence of the field is a string

varies

The field occurs multiple times in the payload with a variety of different types

The type can also be set explicitly using the type(FieldType) method on FieldDescriptor:

.andDo(document("index").withResponseFields(
        fieldWithPath("contact.email")
                .type(FieldType.STRING) (1)
                .optional()
                .description("The user's email address")));
1 Set the field’s type to string.

Query parameters

A request’s query parameters can be documented using withQueryParameters

this.mockMvc.perform(get("/users?page=2&per_page=100"))
    .andExpect(status().isOk())
    .andDo(document("users").withQueryParameters( (1)
            parameterWithName("page").description("The page to retrieve"), (2)
            parameterWithName("per_page").description("Entries per page") (3)
    ));
1 withQueryParameters is used to describe the query parameters
2 Documents a parameter named page. Uses the static parameterWithName method on org.springframework.restdocs.request.RequestDocumentation.
3 Documents a parameter named per_page

The result is a snippet named query-parameters.adoc that contains a table describing the query parameters that are supported by the resource.

When documenting query parameters, the test will fail if an undocumented query parameter is used in the request. Similarly, the test will also fail if a documented query parameter is not found in the request.

Default snippets

A number of snippets are produced automatically when you document a call to MockMvc.perform:

Snippet Description

curl-request.adoc

Contains the curl command that is equivalent to the MockMvc call that is being documented

http-request.adoc

Contains the HTTP request that is equivalent to the MockMvc call that is being documented

http-response.adoc

Contains the HTTP response that was returned

Using parameterized output directories

The output directory used by document can be parameterized. The following parameters are supported:

Parameter Description

{methodName}

The name of the test method, formatted using camelCase

{method-name}

The name of the test method, formatted using kebab-case

{method_name}

The name of the test method, formatted using snake_case

{step}

The count of calls to MockMvc.perform in the current test

For example, document("{method-name}") in a test method named creatingANote will write snippets into a directory named creating-a-note.

The {step} parameter is particularly useful in combination with Spring MVC Test’s alwaysDo functionality. It allows documentation to be configured once in a setup method:

@Before
public void setUp() {
    this.mockMvc = MockMvcBuilders.webAppContextSetup(this.context)
            .apply(documentationConfiguration())
            .alwaysDo(document("{method-name}/{step}/"))
            .build();
}

With this configuration in place, every call to MockMvc.perform will produce the default snippets without any further configuration. Take a look at the GettingStartedDocumentation classes in each of the sample applications to see this functionality in action.

Customizing responses

There may be situations where you do not want to document a response exactly as received. Spring REST Docs provides a number of response post processors that can be used to modify a response after it is received but before it’s documented.

Response modification is configured using a ResponseModifier. An instance can be obtained using the static modifyResponseTo method on RestDocumentation. Once the response modifications have been provided, documentation can be configured as usual via the andDocument method:

this.mockMvc.perform(get("/"))
    .andExpect(status().isOk())
    .andDo(modifyResponseTo(/* ... */) (1)
            .andDocument("index")); (2)
1 Call modifyResponseTo to configure response modifications, passing in one or more ResponsePostProcessor implementations.
2 Proceed with documenting the call

Pretty printing

prettyPrintContent on ResponsePostProcessors formats the body of the response to make it easier to read.

If you’re documenting a Hypermedia-based API, you may want to encourage clients to navigate the API using links rather than through the use of hard coded URIs. One way to do this is to limit the use of URIs in the documentation. maskLinks on ResponsePostProcessors replaces the href of any links in the response with …​. A different replacement can also be specified if you wish.

Removing headers

removeHeaders on ResponsePostProcessors removes any occurrences of the named headers from the response.

Replacing patterns

replacePattern on ResponsePostProcessors provides a general purpose mechanism for replacing content in a response. Any occurrences of a regular expression are replaced.

Configuration

Documented URIs

The default configuration for URIs documented by Spring REST docs is:

Setting Default

Scheme

http

Host

localhost

Port

8080

Context path

Empty string

This configuration is applied by RestDocumentationConfigurer. You can use its API to change one or more of the defaults to suit your needs:

this.mockMvc = MockMvcBuilders.webAppContextSetup(this.context)
        .apply(documentationConfiguration().uris()
                .withScheme("https")
                .withHost("example.com")
                .withPort(443)
                .withContextPath("/api"))
        .build();

Snippet encoding

The default encoding used by Asciidoc is UTF-8. Spring REST docs adopts the same default for the snippets that it generated. If you require an encoding other than UTF-8, use RestDocumentationConfigurer to configure it:

this.mockMvc = MockMvcBuilders.webAppContextSetup(this.context)
        .apply(documentationConfiguration().snippets()
                .withEncoding("ISO-8859-1"))
        .build();

Snippet output directory

As described in Build configuration the snippet output directory is configured in your pom.xml or build.gradle file. This configuration applies to builds on the command line, but it may not apply when running your tests in your IDE. In the absence of the property, Spring REST Docs will write the generated snippets to standard out.

If you’d prefer that your IDE writes the snippets to disk you can use a file in src/test/resources named documentation.properties to specify the output directory that should be used:

org.springframework.restdocs.outputDir: target/generated-snippets

Working with Asciidoctor

This section describes any aspects of working with Asciidoctor that are particularly relevant to Spring REST Docs.

Resources

Including snippets

The include macro is used to include generated snippets in your documentation. The snippets attribute specified in the build configuration can be used to reference the snippets output directory, for example:

include::{snippets}/index/curl-request.adoc[]

Customizing tables

Many of the snippets contain a table in its default configuration. The appearance of the table can be customized by providing some additional configuration when the snippet is included.

Formatting columns

Asciidoctor has rich support for formatting a table’s columns. For example, the widths of a table’s columns can be specified using the cols attribute:

[cols=1,3] (1)
include::{snippets}index/links.adoc[]
1 The table’s width will be split across its two columns with the second column being three times as wide as the first.

Configuring the title

The title of a table can be specified using a line prefixed by a .:

.Links (1)
include::{snippets}index/links.adoc[]
1 The table’s title will be Links.

Further reading

Refer to the Tables section of the Asciidoctor user manual for more information about customizing tables.

Contributing

Spring REST Docs is intended to make is easy for you to produce high-quality documentation for your RESTful services. However, we can’t achieve that goal without your contributions.

Questions

You can ask questions about Spring REST Docs on StackOverflow using the spring-restdocs tag. Similarly, we encourage you to help your fellow Spring REST Docs users by answering questions.

Bugs

If you believe you have found a bug, please take a moment to search the existing issues. If no one else has reported the problem, please open a new issue that describes the problem in detail and, ideally, includes a test that reproduces it.

Enhancements

If you’d like an enhancement to be made to Spring REST Docs, pull requests are most welcome. The source code is on GitHub. You may want to search the existing issues and pull requests to see if the enhancement is already being worked on. You may also want to open a new issue to discuss a possible enhancement before work on it begins.