What is the usage of request body in Spring?

In Spring, the @RequestBody annotation is used to map the request body of an HTTP request to a method parameter. This allows for the conversion of the request body to an object or other data type for further processing in the method.

When using the @RequestBody annotation, Spring automatically chooses the appropriate HttpMessageConverter based on the Content-Type header of the request to convert the request body into the parameter type. Common converters include those that convert JSON, XML, form data, etc. into Java objects.

The steps for using @RequestBody are as follows:

1. Add the @RequestBody annotation before the parameters that will be receiving the request body in the handling method of the Controller.

@PostMapping("/example")
public void exampleMethod(@RequestBody User user) {
    // 处理接收到的请求体
}

1. Ensure that the Content-Type header of the request matches the data type being converted. For example, if the request body is in JSON format, the Content-Type should be application/json.
2. Spring will select the appropriate HttpMessageConverter based on the Content-Type header information to convert the request body into the parameter type.

It is important to note that when using the @RequestBody annotation, the data in the request body should match the data structure of the parameter type, otherwise the conversion process may fail.

Additionally, the @RequestBody annotation can also be used on the return value of a method to convert the method’s return value into a response body. In this case, Spring will choose an appropriate HttpMessageConverter based on the return value type to convert the return value into the response body.