The key to calling the REST API is to master four core steps: determining the request method and interface address, setting the request header, constructing the request body, and processing the response result. 1. First select the GET, POST, PUT or DELETE methods according to the operation type, and confirm the interface URL, pay attention to the use of path parameters and query parameters; 2. Set Headers to specify content type and authentication information, such as Content-Type: application/json and Authorization: Bearer token; 3. For POST and PUT requests, send data in the Body in format, such as JSON or form format, while GET and DELETE usually do not have Body; 4. Check the response status code after the call (such as 200 means success, 400/401/404/500 is a common error), and checksum and exception handling of the returned data to ensure safe use.

Calling the REST API is actually not difficult, but you have to figure out a few key points: how to send a request, what parameters to pass, and how to handle and return the result. As long as you master these, you can successfully deal with back-end services.

1. Determine the request method and interface address

Common request methods for REST API are GET, POST, PUT, and DELETE, which correspond to the search, addition, modification and deletion operations. for example:

• Get user list → GET /api/users
• Create a user → POST /api/users
• Modify a user → PUT /api/users/1
• Delete a user → DELETE /api/users/1

First look at the documentation to confirm which interface you want to adjust and which method you use. The URL may contain path parameters (such as 1 above), or query parameters may be required, such as GET /api/users?role=admin.

2. Set request headers

Headers are usually used to specify content types, authentication information, etc. The most common ones are:

• Content-Type : Tell the server what format the data you send is, such as application/json or application/x-www-form-urlencoded.
• Authorization : Used for authentication, such as Bearer Token or Basic Auth.

For example, if you want to use Token authentication, the header might be:

 Authorization: Bearer your_token_here
Content-Type: application/json

Don't forget to set the correct headers according to the interface requirements, otherwise you may encounter permission issues or parsing errors.

3. Construct the request body (Body)

For POST and PUT requests, data is usually required to be transmitted in the Body. The format must correspond to Content-Type:

• JSON format: {"name": "Alice", "age": 25}
• Form format: name=Alice&age=25

GET and DELETE generally do not require a Body, and parameters are passed through URL or Query String.

4. Process the response results

After the call, the API returns a response, usually in JSON format. You need to check whether the status code is 200 (OK), 201 (Created), etc., and pay attention to possible error codes, such as:

• 400 Bad Request: The parameters are incorrect
• 401 Unauthorized: No permission
• 404 Not Found: The interface does not exist
• 500 Server Error: Server error

After getting the data, remember to do basic checksum exception handling, and don't just use it.

Basically that's it. By mastering these steps, most REST interfaces can handle it. During development, you can use tools, such as Postman testing interface, or use Axios, Fetch, jQuery.ajax and other libraries to actually call.

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