HTTP status code 405 analysis: understand why the request method is not allowed

HTTP status code 405 analysis: understand the reason why the request method is not allowed

HTTP (Hypertext Transfer Protocol) is a protocol used to transmit hypertext. Defines the communication rules between client and server. In the HTTP protocol, the client sends a request to the server, and the server responds accordingly according to the request.

HTTP status code is used to identify the processing result of the request. The 405 status code indicates that the server does not allow the use of the method specified in the request. This article will analyze the 405 status code so that we can better understand why the request method is not allowed.

The definition of the 405 status code is defined by the HTTP protocol specification, which compares the disallowance of the request method with the HTTP protocol specification and gives the reasons why it is not allowed. According to the HTTP protocol specification, the request method is usually specified by the client in the request line, such as GET, POST, PUT, DELETE, etc. These methods have their own functions and semantics, and the server can perform corresponding operations based on these methods.

When the client sends a request to the server, the server will first check the method in the request. If the server does not support this method, a 405 status code will be returned to the client. This means that the client used a request method that is not allowed by the server.

After the client receives the 405 status code, it should obtain the list of methods supported by the server based on the Allow header field in the response. Based on the Allow header field, the client can choose to resend the request using a method supported by the server.

There are several common situations that cause the server to return a 405 status code.

1. Security restrictions: Some request methods are prohibited by the server to ensure security. For example, the server may not allow clients to use the DELETE method to delete resources to prevent data loss caused by misoperation.
2. Illegal request method: Some servers only allow specific request methods. If the client sends a method that the server does not support, the server will return a 405 status code. For example, an API only allows the use of the GET method to obtain resources. If the client uses the POST method to send a request, the server will return a 405 status code.
3. URL routing restrictions: URL routing is the process of mapping URL requests to server-side handlers. If the server-side URL routing rules do not allow a certain request method, the server will return a 405 status code. This is usually done to restrict access to specific resources.

For the client, receiving a 405 status code is not necessarily an error. It reminds the client that the request method is not allowed by the server and needs to be adjusted. The client can resend the request based on the Allow header field in the 405 status code.

For the server side, returning the 405 status code is to ensure that the received request is processed correctly. The server needs to restrict request methods according to its own policies to ensure the security and stability of the system.

To summarize, HTTP status code 405 means that the request method is not allowed by the server. The reason why the server returns a 405 status code may be due to security restrictions, illegal request methods, or URL routing restrictions. After receiving the 405 status code, the client should resend the request based on the Allow header field. The server restricts request methods according to its own policies to ensure the security and stability of the system. Understanding the meaning and causes of the 405 status code can help us better handle HTTP requests and responses.

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