Detailed explanation of HTTP request method

Request method

Request Methods are used in HTTP requests to specify the type of operation to be performed on the target resource. Each request needs to specify a request method that tells the server what to do.

Here are some common HTTP request methods and their main uses:

GET：

The GET method is one of the most common HTTP request methods. It sends a request to the server through a URL and returns the requested resource.
The main characteristics of the GET request are as follows:
1. retrieve data:
  - GET requests are used to obtain resources on the server, such as web pages, pictures, files, etc.
2. Parameter passing:
  - GET requests can carry parameters in the URL to pass the data required for the request to the server. These parameters appear in the URL's query string as key-value pairs, by using a question mark (?) to separate the URL and parameters.
3. Idempotence:
  - GET requests are idempotent, that is, multiple GET requests to the same URL will not affect the resource. The results of multiple GET requests should be the same.
  In computing, idempotence means that executing the same operation multiple times produces the same result as executing it only once. In other words, no matter how many times you perform an operation, the end result is the same.
4. Cacheable:
  - Due to the idempotence of GET requests, it can usually be cached. If the response returned by the server allows caching, then a GET request to the same URL can get the response directly from the cache without an actual request.
5. Request header:
  - GET requests can pass additional information through request headers (Headers), such as user agent, accepted content types, etc.
6. safety:
  - GET requests do not modify data on the server and are therefore considered safe. It is mainly used to obtain data, not modify data.
In programming, various programming languages and frameworks can be used to send GET requests, such as through HTTP libraries or network request libraries. By specifying the URL, request headers, parameters, etc., you can customize and send GET requests, and process the response data returned by the server. Some sensitive or security-related data should not be passed through GET requests because URLs and query strings can be recorded in browser history, log files, etc.

Example:

Let's say we have a home automation system and want to control and monitor some devices in the home through GET requests. We can create a web application that communicates with the home automation system through HTTP GET requests.

First, set up the network interface of the home automation system, define unique identifiers for each device, and provide corresponding APIs.

We can then use any programming language or tool to send HTTP GET requests to interact with the system. The following is a Python example using the requests library to send a GET request to obtain the status of a specified device in a home automation system:

import requests

device_id = "xyz123"  # 设备的唯一标识符
url = f"http://your-home-automation-api/devices/{
      
      device_id}"  # API的URL

response = requests.get(url)

if response.status_code == 200:
    device_status = response.json()["status"]  # 从响应中获取设备状态
    print(f"Device status: {
      
      device_status}")
else:
    print("Failed to retrieve device status")

In this example, we assume that the home automation system's API has the following characteristics:

All devices are http://your-home-automation-api/devices/{device_id}accessible through the URL where {device_id}is the device's unique identifier.
Use a GET request to obtain the status of the device from the URL, returning a JSON response containing the status of the device.

We need to replace the URL and device identifier in the code with the actual URL and device identifier, making sure it matches the API of the home automation system.

By sending a GET request and parsing the response, we can get the status of a specific device in the home automation system and take appropriate action as needed.

POST：

Used to submit data to the server and request the server to perform some operation on the target URI. The POST method is not idempotent, and each execution of a POST request may result in different results.
Some important characteristics of POST requests are as follows:
1. Submit data: POST request is used to submit data to the server, such as data entered in a form, uploaded files, etc.
2. Request body: A POST request sends data to the server as the request body, rather than as part of the URL like a GET request.
3. Security: Compared to GET requests, POST requests are more secure because the data is not exposed directly in the URL but is sent in an encrypted form through the request body.
4. Non-idempotent: POST requests are non-idempotent, that is, multiple POST requests to the same URL may produce different results or cause side effects.
5. Request headers: You can use request headers (Headers) to pass additional information, such as Content-Type, Authorization, etc.
6. Data length limit: POST requests usually have no clear limit on the data length of the request body, but the server may have configuration restrictions.
In programming, various programming languages and frameworks can be used to send POST requests, such as through HTTP libraries or network request libraries. By specifying the URL, request headers, request body, etc., you can customize and send POST requests, and process the response data returned by the server.

Here is a simple example of sending a POST request in Python:
```
import requests

url = "http://example.com/post"
payload = {
      
      'key1': 'value1', 'key2': 'value2'}  # 要发送的数据
response = requests.post(url, data=payload)

print(response.status_code)  # 打印响应状态码
print(response.text)  # 打印响应内容
```
The above code uses Python's requests library to send a POST request and prints the response status code and response content returned by the server. We can further process the returned response data as needed.

It should be noted that POST requests should be used to create, modify or store resources. In addition, some special POST requests can also be used to query or obtain data, but these do not comply with HTTP semantics and should be used with caution.

PUT：

Used to create or update the resource at the specified URI on the server. A PUT request replaces the entire target resource or updates it based on the content in the request.
Some important characteristics of PUT requests are as follows:
1. Update resources: The PUT request is used to replace the resource under the specified URL path, or create a new resource if the resource does not exist.
2. Request body: A PUT request sends data to the server as the request body, rather than as part of the URL like a GET request.
3. Idempotence: PUT requests are idempotent, that is, multiple PUT requests to the same URL should have the same impact on resources without side effects.
4. Security: Compared to GET requests, PUT requests are more secure because the data is not exposed directly in the URL but is sent in an encrypted form through the request body.
5. Request headers: You can use request headers (Headers) to pass additional information, such as Content-Type, Authorization, etc.
6. Data length limit: PUT requests usually have no clear limit on the data length of the request body, but the server may have configuration restrictions.
In programming, various programming languages and frameworks can be used to send PUT requests, such as through HTTP libraries or network request libraries. By specifying the URL, request header, request body, etc., you can customize and send PUT requests, and process the response data returned by the server.

Here is a simple example of sending a PUT request in Python:
```
import requests

url = "http://example.com/put"
payload = {
      
      'key1': 'value1', 'key2': 'value2'}  # 要发送的数据
response = requests.put(url, data=payload)

print(response.status_code)  # 打印响应状态码
print(response.text)  # 打印响应内容
```
The above code uses Python's requests library to send a PUT request, and prints the response status code and response content returned by the server. We can further process the returned response data as needed.

It should be noted that PUT requests should be used to create or replace resources, not to query or obtain data. In addition, some servers may not support PUT requests, please confirm whether the server supports this request method.

DELETE：

Used to delete the resource at the specified URI on the server.
Some important features of DELETE requests are as follows:
1. Delete resources: The DELETE request is used to notify the server to delete resources under the specified URL path.
2. Idempotence: DELETE requests are idempotent, that is, multiple DELETE requests to the same URL should have the same impact on resources without side effects.
3. Security: DELETE request is more secure than GET request as it does not expose sensitive data in the URL.
4. Request headers: You can use request headers to pass additional information, such as Authorization, etc.
5. Data length limit: DELETE requests usually do not require a request body, so there is no explicit data length limit.
In programming, various programming languages and frameworks can be used to send DELETE requests, such as through HTTP libraries or network request libraries. By specifying the URL and possible request headers, you can customize and send DELETE requests and process the response data returned by the server.

Here is a simple example of sending a DELETE request using Python:
```
import requests

url = "http://example.com/delete"
response = requests.delete(url)

print(response.status_code)  # 打印响应状态码
print(response.text)  # 打印响应内容
```
The above code uses Python's requests library to send a DELETE request and prints the response status code and response content returned by the server. We can further process the returned response data as needed.

It should be noted that when using DELETE requests to operate resources, you should carefully confirm the target and impact scope of the operation. Deletion operations are irreversible and may result in data loss, so you should be careful when using DELETE requests.

HEAD：

Similar to the GET method, but only response headers are returned, not the response body. The HEAD method can be used to obtain meta-information about a resource, such as response status code, content type, etc., without obtaining the entire response content.
Some important characteristics of the HEAD request are as follows:
1. Metadata acquisition: The HEAD request is used to only obtain the response header information of the target resource without transmitting the actual content. This is useful for getting metadata about a resource (such as content length, modification time, etc.) without transferring the entire resource.
2. Idempotence: Like GET requests, HEAD requests are also idempotent, and multiple HEAD requests for the same URL will not have side effects.
3. Request headers: You can use request headers to pass additional information, such as Authorization, etc.
4. Data length limit: Because HEAD requests do not return actual content and generally do not require a request body, there is no explicit data length limit.
In programming, various programming languages and frameworks can be used to send HEAD requests, such as through HTTP libraries or network request libraries. By specifying the URL and possible request headers, you can customize and send HEAD requests and process the response data returned by the server.

Here is a simplified example of sending a HEAD request using Python:
```
import requests

url = "http://example.com"
response = requests.head(url)

print(response.status_code)  # 打印响应状态码
print(response.headers)  # 打印响应头信息
```
The above code uses Python's requests library to send a HEAD request and prints the response status code and response header information returned by the server. We can further process the returned response data as needed.

It should be noted that when using a HEAD request, the server should return the same response header information as a GET request, but will not return the actual response body content.

OPTIONS：

Used to obtain the request methods and available resource options supported by the server.
Some important characteristics of OPTIONS requests are as follows:
1. Query supported options: The OPTIONS request is used to query the request methods supported by a specific URL path on the server, allowed request headers and other information.
2. Metadata acquisition: The response returned by the OPTIONS request usually contains metadata about the options and functions supported by the server, but does not contain the actual resource content.
3. Idempotence: OPTIONS requests are idempotent, and multiple OPTIONS requests for the same URL will not have side effects.
4. Request headers: You can use request headers to pass additional information, such as Authorization, etc.
In programming, various programming languages and frameworks can be used to send OPTIONS requests, such as through HTTP libraries or network request libraries. By specifying the URL and possible request headers, you can customize and send OPTIONS requests and process the response data returned by the server.

Here is a simplified example of sending an OPTIONS request using Python:
```
import requests

url = "http://example.com"
response = requests.options(url)

print(response.status_code)  # 打印响应状态码
print(response.headers)  # 打印响应头信息
```
The above code uses Python's requests library to send OPTIONS requests, and prints the response status code and response header information returned by the server. We can further process the returned response data as needed.

It should be noted that when using the OPTIONS request, the server should return information about the options and functions related to the target resource so that the client can understand the server's support for the resource.

TRACE：

Used for echo requests. After receiving the TRACE request, the server returns the request content to the client as the response body for testing and diagnosis.
Some important features of TRACE requests are as follows:
1. Tracking requests: The TRACE request allows the client to view changes to the request message, including request headers and request bodies, by the transit server during the delivery process.
2. Debugging and troubleshooting: TRACE requests are often used to debug and troubleshoot network request problems, such as understanding whether the request has been modified, changes during transmission through the proxy server, etc.
3. Security issues: Due to the characteristics of the TRACE request, there may be security risks, because it can completely transmit the request message back to the client, which may leak sensitive information.
In actual development, it is generally not recommended to allow TRACE requests in the production environment to avoid potential security risks.

Here is a simplified example of sending a TRACE request using Python:
```
import requests

url = "http://example.com"
response = requests.request("TRACE", url)

print(response.status_code)  # 打印响应状态码
print(response.text)  # 打印响应内容
```
The above code uses Python's requests library to send a TRACE request and prints the response status code and response content returned by the server. We can further process the returned response data as needed.

It should be noted that the return of the TRACE request should contain exactly the same content as the request, so that the client understands the changes in the request during delivery.

Again, it is generally not recommended to allow TRACE requests in production environments to avoid potential security risks.

PATCH：

Used to partially update resources on the server. A PATCH request updates only a portion of a resource, not the entire resource.
Some important characteristics of PATCH requests are as follows:
1. Partial update: PATCH request is used to make partial modifications to existing resources. Only a part of the resource is updated without replacing the entire resource.
2. Request body: The PATCH request includes the modification information to be applied to the resource in the request body, instead of replacing the entire resource like the PUT request.
3. Idempotence: The PATCH request is idempotent, that is, multiple PATCH requests for the same URL will produce the same result.
4. Request headers: You can use request headers (Headers) to pass additional information, such as Content-Type, Authorization, etc.
5. Data length limit: Because the PATCH request only needs to transmit the part to be modified, there is usually no explicit data length limit.
In programming, various programming languages and frameworks can be used to send PATCH requests, such as through HTTP libraries or network request libraries. By specifying the URL, request headers and request body, you can customize and send PATCH requests, and process the response data returned by the server.

Here is a simplified example of sending a PATCH request using Python:
```
import requests
import json

url = "http://example.com/patch"
payload = {
      
      'key1': 'new value'}  # 要修改的数据
headers = {
      
      'Content-Type': 'application/json'}  # 设置请求头
response = requests.patch(url, data=json.dumps(payload), headers=headers)

print(response.status_code)  # 打印响应状态码
print(response.text)  # 打印响应内容
```
The above code uses Python's requests library to send a PATCH request and prints the response status code and response content returned by the server. We can further process the returned response data as needed.