@Requestparam use

1、 The difference between adding and not adding

@RequestMapping("/list1")
public String test1(int userId) {
　　return "list";
}
@RequestMapping("/list2")
public String test2(@RequestParam int userId) {
　　return "list";
}

（1） No addition @RequestParam The parameter name of the front end must be consistent with the variable name of the back-end controller to take effect

（2） No addition @RequestParam Parameters are not required , Add @RequestParam The writing parameter is required . but @RequestParam Can pass @RequestParam(required = false) Set to not required .

（3）@RequestParam Can pass @RequestParam(“userId”) perhaps @RequestParam(value = “userId”) Specify the passed in parameter name .

（4）@RequestParam Can pass @RequestParam(defaultValue = “0”) Specify parameter defaults

（5） If the interface has a back-end besides the front-end call RPC call , Cannot be omitted @RequestParam, otherwise RPC The parameter will not be found and an error will be reported

（6） During the interview ：

• No addition @RequestParam annotation ：url With or without parameters , Input localhost:8080/list1 as well as localhost:8080/list1userId=xxx Methods can execute
• Add @RequestParam annotation ：url Must have parameters . That is, you enter directly localhost:8080/list2 Will report a mistake , Method... Will not be executed . Input only localhost:8080/list2userId=xxx To execute the corresponding method