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This article mainly introduces what is the difference between @ RequestBody,@RequestParam and @ Param. It has a certain reference value. Interested friends can refer to it. I hope you will gain a lot after reading this article. Let's take a look at it.

The difference between @ RequestBody,@RequestParam and @ Param @ Param

@ Param is an annotation in mybatis. When using annotations to simplify xml configuration, @ Param annotations are used to name parameters. After parameter naming, you can get parameter values according to their names, and correctly pass parameters into the sql statement. Take a look at the following example:

Public interface Mapper {@ Select ("select s_id id,s_name name,class_id classid from student where sprinter name = # {aaaa} and class_id = # {bbbb}") public Student select (@ Param ("aaaa") String name,@Param ("bbbb") int class_id); @ Delete. @ Insert. } @ RequestBody

The @ requestBody annotation is often used to deal with content that content-type is not the default application/x-www-form-urlcoded encoding, such as application/json or application/xml. In general, it is often used to deal with application/json types.

With @ requestBody, you can bind the JSON string in the request body to the corresponding bean, or you can bind them to the corresponding string respectively.

For example, the following situations:

Ajax ({url: "/ login", type: "POST", data:' {"userName": "admin", "pwd", "admin123"}', content-type: "application/json charset=utf-8", success:function (data) {alert ("request success!");}}); @ requestMapping ("/ login") public void login (@ requestBody String userName,@requestBody String pwd) {System.out.println (userName+ ":" + pwd);}

In this case, the values of two variables in the JSON string are assigned to two strings, but suppose I have a User class with the following fields:

String userName;String pwd

Then the above parameters can be changed to the following form: the form @ requestBody User user assigns the value in the JSON string to the corresponding attribute in the user

It is important to note that the key in the JSON string must correspond to the attribute name in the user, otherwise the request will not pass.

Processing data passed by HttpEntity is generally used to deal with data in a non-Content-Type: application/x-www-form-urlencoded encoding format.

In the GET request, @ RequestBody is not applicable because there is no HttpEntity.

In a POST request, the parameters passed through HttpEntity must declare the type of data in the request header Content-Type,SpringMVC parses the data in the HttpEntity by using the HttpMessageConverters configured by HandlerAdapter, and then binds to the corresponding bean.

@ RequestParam

Used to process Content-Type: content encoded for application/x-www-form-urlencoded. (in Http protocol, if Content-Type is not specified, the parameter passed by default is application/x-www-form-urlencoded type)

RequestParam can accept attributes of simple types as well as object types.

The essence is to convert the Key-Value parameter Map in Request.getParameter () into parameter receiving objects or fields by using the transformation mechanism ConversionService of Spring.

In the request of Content-Type: application/x-www-form-urlencoded, the value of queryString in get mode and the value of body data in post mode are accepted by Servlet and converted to the parameter set of Request.getParameter (), so @ RequestParam can get them.

@ RequestParam usage precautions

RequestParam: bind the request parameter to the method parameter of your controller

There is an attribute required in the annotation indicating whether the parameter is included. The default is true, which means that the request path must contain the parameter. If not, an error will be reported.

But don't make any mistakes when using it. Required=true can verify whether the parameter is included in the request, but cannot verify whether the parameter value is empty.

For example, the following interface

Http://127.0.0.1:9802/api/order/vr/testRequestParam can be intercepted like this, because the parameter param1 does not exist in the request parameter.

But http://127.0.0.1:9802/api/order/vr/testRequestParam?param1 can request success.

In order to intercept requests with empty parameters

You also need to add @ Valid @ NotBlank to the parameters

As follows:

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