java - Difference between two @RequestMapping annotations

Question

I am pretty new in Spring MVC and I have the following doubt.

In a controller, I have a method annotated in this way:

@Controller
@RequestMapping(value = "/users")
public class UserController {

    @RequestMapping(params = "register")
    public String createForm(Model model) {
        model.addAttribute("user", new Customer());
        return "user/register";
    } 

}

So this method handle HTTP Request toward the URL /users?register where register is a parameter (because the entire class handle request toward /users resource).

Is it the same thing if, instead using the params = "register" I use the following syntaxt:

@Controller
public class UserController {

    @RequestMapping("/users/{register}")
    public String createForm(Model model) {
        model.addAttribute("user", new Customer());
        return "user/register";
    } 

}

I have deleted the mapping at class level and I use @RequestMapping("/users/{register}").

Is it the same meaning of the first example?

Answer 1

不，它们是完全不同的构造：

代码 1

@Controller
@RequestMapping(value = "/users")
public class UserController {

    @RequestMapping(params = "register")
    public String createForm(Model model) {
        model.addAttribute("user", new Customer());
        return "user/register";
    } 

}

在这种情况下，createForm将在 URL 发出 HTTP 请求时调用方法/users?register。引用Spring Javadocregister ，这意味着无论HTTP 参数的值如何，都会调用此方法；它必须存在。

还支持“myParam”样式表达式，此类参数必须存在于请求中（允许具有任何值）。

代码 2

@Controller
public class UserController {

    @RequestMapping("/users/{register}")
    public String createForm(Model model) {
        model.addAttribute("user", new Customer());
        return "user/register";
    } 

}

在这种情况下，@RequestMapping声明register为PathVariable. createForm如果在 URL 发出 HTTP 请求，则将调用该方法/users/something，无论something. 您实际上可以something像这样检索它：

@RequestMapping("/users/{register}")
public String createForm(@PathVariable("register") String register, Model model) {
    // here "register" will have value "something".
    model.addAttribute("user", new Customer());
    return "user/register";
}