1. Overview
In this quick tutorial, we’ll focus on a common error, ‘Request Method not Supported – 405’, that developers face while exposing their APIs for specific HTTP verbs with Spring MVC.
Naturally, we’ll also discuss the common causes of this error.
2. Request Method Basics
If we’re just starting to learn about Spring MVC, here’s a good intro article we can start with.
We’ll also have a very quick look at the basics to understand the request methods supported by Spring, and some of the common classes of interest here.
In a highly simplified way, MVC HTTP methods are basic operations that a request can trigger on the server. For example, some methods fetch the data from the server, some submit data to the server, some might delete the data, etc.
The @RequestMapping annotation specifies the supported methods for the request.
Spring declares all the supported request methods under an enum, RequestMethod, which specifies the standard GET, HEAD, POST, PUT, PATCH, DELETE, OPTIONS, and TRACE verbs.
The Spring DispatcherServlet supports all of them by default, except OPTIONS and TRACE. @RequestMapping uses the RequestMethod enum to specify which methods are supported.
3. Simple MVC Scenario
Now let’s have a look at a code example that maps all HTTP methods:
@RestController
@RequestMapping(value="/api")
public class RequestMethodController {
@Autowired
private EmployeeService service;
@RequestMapping(value = "/employees", produces = "application/json")
public List<Employee> findEmployees()
throws InvalidRequestException {
return service.getEmployeeList();
}
}
Notice how the example declares the findEmployee() method. It doesn’t specify any specific request method, which means this URL supports all default methods.
We can request the API using different supported methods, such as curl:
$ curl --request POST http://localhost:8080/api/employees
[{"id":100,"name":"Steve Martin","contactNumber":"333-777-999"},
{"id":200,"name":"Adam Schawn","contactNumber":"444-111-777"}]
Naturally, we can send the request in multiple ways: a simple curl command, Postman, AJAX, etc.
And, of course, we expect to get the 200 OK response if the request is correctly mapped and successful.
4. Problem Scenario – the HTTP 405
But what we’re discussing here is the scenarios where the request isn’t successful.
‘405 Method Not Allowed’ is one of the most common errors we observe while working with Spring requests.
Let’s have a look at what happens if we specifically define and handle GET requests in Spring MVC:
@RequestMapping(
value = "/employees",
produces = "application/json",
method = RequestMethod.GET)
public List<Employee> findEmployees() {
...
}
// send the PUT request using CURL
$ curl --request PUT http://localhost:8080/api/employees
{"timestamp":1539720588712,"status":405,"error":"Method Not Allowed",
"exception":"org.springframework.web.HttpRequestMethodNotSupportedException",
"message":"Request method 'PUT' not supported","path":"/api/employees"}
5. 405 Not Support – Reason, Solution
What we’re getting in the previous scenario is an HTTP response with the 405 Status Code, which is a client error indicating that the server doesn’t support the method/verb sent in the request.
As the name here suggests, the reason for this error is sending the request with a non-supported method.
As we can expect, we can solve this by defining an explicit mapping for PUT in the existing method mapping:
@RequestMapping(
value = "/employees",
produces = "application/json",
method = {RequestMethod.GET, RequestMethod.PUT}) ...
Alternatively, we can define the new method/mapping separately:
@RequestMapping(value = "/employees",
produces = "application/json",
method=RequestMethod.PUT)
public List<Employee> postEmployees() ...
6. Conclusion
The request method/verb is a critical aspect in HTTP communication. We need to be careful with the exact semantics of the operations we define on the server side, and the exact requests we send in.
As always, the examples shown in this article are available on over on GitHub.