In any RESTful API, query parameters and headers play a crucial role in requesting and manipulating resources. Properly documenting these parameters and headers not only helps developers understand how to interact with the API but also improves the API’s discoverability. In this blog post, we will explore how to document query parameters and headers using Java Spring REST Docs.

What is Java Spring REST Docs?

Java Spring REST Docs is a testing and documentation library that works hand-in-hand with Spring MVC and Spring Boot applications. It allows developers to generate concise and easily maintainable documentation for their APIs by writing tests.

Documenting Query Parameters

Query parameters are additional data appended to the URL after a question mark (?). These parameters help clients filter, sort, or limit the response from the API. To document query parameters using Java Spring REST Docs, we can follow these steps:

1. Define a test method using JUnit and annotate it with @Test and @RequestMapping:

   @Test
   @RequestMapping(value = "/employees", method = RequestMethod.GET)
   public void getEmployees() {
    // ...
   }
   

2. Use Spring REST Docs’ RequestDocumentation.requestParameters method to document the query parameters:

import static org.springframework.restdocs.request.RequestDocumentation.*;
import static org.springframework.restdocs.mockmvc.RestDocumentationRequestBuilders.*;

@Test
public void getEmployees() throws Exception {
    this.mockMvc.perform(get("/employees")
            .param("name", "John")
            .param("department", "IT"))
            .andExpect(status().isOk())
            .andDo(document("get-employees",
                    requestParameters(
                            parameterWithName("name").description("Employee name"),
                            parameterWithName("department").description("Employee department")
                    )));
}

1. Run the test, and Java Spring REST Docs will generate the documentation, including the request parameters, in the desired format (HTML, PDF, etc.).

Documenting Headers

Headers contain additional information about a request or response. They can provide crucial details, such as authentication tokens or content types. To document headers using Java Spring REST Docs, we can follow these steps:

1. Add the RequestHeader annotation to the controller method parameter to explicitly declare the expected headers:

@GetMapping("/employees")
public ResponseEntity<List<Employee>> getEmployees(@RequestHeader("Authorization") String token) {
    // ...
}

1. Use Spring REST Docs’ RequestDocumentation.requestHeaders method to document the headers:

import static org.springframework.restdocs.request.RequestDocumentation.*;

@Test
public void getEmployees() throws Exception {
    this.mockMvc.perform(get("/employees")
            .header("Authorization", "Bearer myBearerToken"))
            .andExpect(status().isOk())
            .andDo(document("get-employees",
                    requestHeaders(
                            headerWithName("Authorization").description("Authentication token")
                    )));
}

1. Run the test, and Java Spring REST Docs will generate the documentation, including the request headers, in the desired format (HTML, PDF, etc.).

Conclusion

Properly documenting query parameters and headers in your Java Spring REST API using Java Spring REST Docs improves the overall clarity and usability of your API. By following the steps outlined in this blog post, you can generate comprehensive and easily maintainable API documentation. Remember, clear documentation not only benefits developers but also enhances the discoverability of your API.

#javaspring #restapi