When building an API with Java Spring, it’s important to properly document the authentication and authorization mechanisms for your endpoints. This helps other developers understand how to interact with your API securely. One way to achieve this is by using Java Spring REST Docs to generate documentation.

What is Java Spring REST Docs?

Java Spring REST Docs is a powerful library that allows you to generate documentation for your RESTful APIs. It integrates with the Java Spring framework and provides tools for documenting request and response payloads, response codes, and even authentication and authorization mechanisms.

Documenting Authentication Mechanisms

To document the authentication mechanisms used in your API, you can use Java Spring REST Docs along with annotations from the Spring Security framework.

1. Start by configuring your Spring Security authentication mechanism. This could be basic authentication, OAuth 2.0, JWT, or any other authentication scheme supported by Spring Security.

@Configuration
@EnableWebSecurity
public class SecurityConfig extends WebSecurityConfigurerAdapter {
    
    @Override
    protected void configure(HttpSecurity http) throws Exception {
        // Configure authentication mechanism
    }
}

1. Once your authentication mechanism is set up, you can use Java Spring REST Docs to document it. Create a test class that extends org.springframework.restdocs.RestDocumentationExtension and annotate it with @AutoConfigureRestDocs. This will enable the generation of REST documentation.

@RunWith(SpringRunner.class)
@SpringBootTest
@AutoConfigureRestDocs
public class AuthenticationDocumentationTests extends RestDocumentationExtension {
    
    @Autowired
    private MockMvc mockMvc;
    
    @BeforeEach
    public void setUp() {
        this.mockMvc = MockMvcBuilders.webAppContextSetup(this.context)
            .apply(documentationConfiguration(this.restDocumentation))
            .build();
    }
    
    @Test
    public void documentAuthenticationMechanism() throws Exception {
        this.mockMvc.perform(get("/api/users").header("Authorization", "Bearer token"))
            .andExpect(status().isOk())
            .andDo(document("authentication-mechanism",
                requestHeaders(headerWithName("Authorization").description("Authentication token")))
            );
    }
}

1. In the test method, use the perform method of MockMvc to simulate a request to an endpoint that requires authentication. Include the necessary headers or parameters for authentication.

2. Use the andExpect method to check the response status or other conditions as required.

3. Finally, use the andDo method along with the document method to document the authentication mechanism. In this example, we document the Authorization header with a description of “Authentication token”.

4. Run the test, and Java Spring REST Docs will generate the documentation based on the annotations and executed test.

Documenting Authorization Mechanisms

To document the authorization mechanisms used in your API, you can follow a similar approach using Java Spring REST Docs.

1. Configure your Spring Security authorization mechanism, such as role-based access control or custom authorization rules.

2. Create a test class that extends RestDocumentationExtension and annotate it with @AutoConfigureRestDocs.

3. In the test method, simulate a request to an endpoint that requires authorization. Ensure that the user has the necessary credentials or permissions for authorization.

4. Use the document method to document the authorization mechanism. This could include documenting the required roles or permissions for accessing the endpoint.

@Test
public void documentAuthorizationMechanism() throws Exception {
    this.mockMvc.perform(get("/api/admin/users").header("Authorization", "Bearer token"))
        .andExpect(status().isOk())
        .andDo(document("authorization-mechanism",
            requestHeaders(headerWithName("Authorization").description("Authentication token")),
            responseFields(...)
        ));
}

1. Document the required roles or permissions in the appropriate request or response field descriptors.

2. Run the test, and Java Spring REST Docs will generate the documentation for the authorization mechanism.

Conclusion

With Java Spring REST Docs, you can easily document the authentication and authorization mechanisms used in your API. By following these steps, you can provide comprehensive documentation that helps other developers understand how to securely interact with your endpoints.