15. Spring 核心注解之 @RequestMapping

@请求映射是应用最广泛的SpringMVC注解。org.springframework.web.bind.annotation.RequestMapping annotation is used to map web requests onto specific handler classes and/or handler methods.

@RequestMapping can be applied to the controller class as well as methods. Today we will look into various usage of this annotation with example and other annotations @PathVariable and @RequestParam.

Spring@RequestMapping

1. @类的请求映射：我们可以将它与类定义一起使用，以创建基URI。例如：

   
   @Controller
   @RequestMapping("/home")
   public class HomeController {
   
   }
   

   现在/home是这个控制器将用于的URI。这个概念非常类似于web应用程序的servlet上下文。

2. @方法的请求映射：我们可以将它与方法一起使用，以提供将使用处理程序方法的URI模式。例如：

   
   @RequestMapping(value="/method0")
   @ResponseBody
   public String method0(){
   	return "method0";
   }
   

   上述注解也可以写成@RequestMapping("/method0"). On a side note, I am using @ResponseBody to send the String response for this web request, this is done to keep the example simple. Like I always do, I will use these methods in Spring MVC application and test them with a simple program or script.

3. @具有多个URI的请求映射：我们可以使用单个方法来处理多个uri，例如：

   
   @RequestMapping(value={"/method1","/method1/second"})
   @ResponseBody
   public String method1(){
   	return "method1";
   }
   

   如果你看看RequestMapping注解，您将看到它的所有变量都是数组。我们可以为处理程序方法的URI映射创建字符串数组。

4. @HTTP方法的请求映射：有时我们希望根据所使用的HTTP方法执行不同的操作，即使请求URI保持不变。我们可以使用@RequestMapping方法变量来缩小调用此方法的HTTP方法的范围。例如：

   
   @RequestMapping(value="/method2", method=RequestMethod.POST)
   @ResponseBody
   public String method2(){
   	return "method2";
   }
   	
   @RequestMapping(value="/method3", method={RequestMethod.POST,RequestMethod.GET})
   @ResponseBody
   public String method3(){
   	return "method3";
   }
   

5. @带头的请求映射：我们可以指定调用处理程序方法时应该出现的头。例如：

   
   @RequestMapping(value="/method4", headers="name=pankaj")
   @ResponseBody
   public String method4(){
   	return "method4";
   }
   	
   @RequestMapping(value="/method5", headers={"name=pankaj", "id=1"})
   @ResponseBody
   public String method5(){
   	return "method5";
   }
   

6. @带有生产和消费的请求映射：我们可以使用标题Content-Type and Accept to find out request contents and what is the mime message it wants in response. For clarity, @RequestMapping provides 生产和消费变量，其中我们可以指定将为其调用方法的请求内容类型和响应内容类型。例如：

   
   @RequestMapping(value="/method6", produces={"application/json","application/xml"}, consumes="text/html")
   @ResponseBody
   public String method6(){
   	return "method6";
   }
   

   以上方法只能使用内容类型为text/html并且能够生成类型的消息应用程序/json和应用程序/xml.

Spring@路径变量

7. @使用@PathVariable进行请求映射：RequestMapping注解可用于处理动态URI，其中一个或多个URI值用作参数。我们甚至可以指定正则表达式使URI动态参数只接受特定类型的输入。它与@路径变量注解通过它我们可以将URI变量映射到其中一个方法参数。例如：

   
   @RequestMapping(value="/method7/{id}")
   @ResponseBody
   public String method7(@PathVariable("id") int id){
   	return "method7 with id="+id;
   }
   	
   @RequestMapping(value="/method8/{id:[d]+}/{name}")
   @ResponseBody
   public String method8(@PathVariable("id") long id, @PathVariable("name") String name){
   	return "method8 with id= "+id+" and name="+name;
   }
   

Spring@RequestParam

8. @使用@RequestParam对URL参数进行RequestMapping：有时我们在请求URL中获取参数，主要是在get请求中。我们可以使用@RequestMapping@RequestParam注解检索URL参数并将其映射到方法参数。例如：

   
   @RequestMapping(value="/method9")
   @ResponseBody
   public String method9(@RequestParam("id") int id){
   	return "method9 with id= "+id;
   }
   

   要使此方法正常工作，参数名应为“；id”；，并且应为int类型。

9. @RequestMapping默认方法：如果某个方法的值为空，则它将作为控制器类的默认方法。例如：

   
   @RequestMapping()
   @ResponseBody
   public String defaultMethod(){
   	return "default method";
   }
   

   正如你在上面看到的，我们已经绘制了地图/home to HomeController, this method will be used for the default URI requests.

10. @请求映射回退方法：我们可以为控制器类创建一个回退方法，以确保即使没有匹配的处理程序方法，也能捕获所有客户端请求。当请求没有处理程序方法时，向用户发送自定义404响应页非常有用。

    
    @RequestMapping("*")
    @ResponseBody
    public String fallbackMethod(){
    	return "fallback method";
    }
    

Spring RestMapping测试程序

我们可以利用Spring RestTemplate为了测试上面的不同方法，但是今天我将使用cURL命令来测试这些方法，因为这些方法很简单，并且没有太多的数据流动。

我创建了一个简单的shell脚本springTest.sh版调用上述所有方法并打印其输出。它看起来像下面。

#!/bin/bash

echo "curl https://localhost:9090/SpringRequestMappingExample/home/method0";
curl https://localhost:9090/SpringRequestMappingExample/home/method0;
printf "

*****

";

echo "curl https://localhost:9090/SpringRequestMappingExample/home";
curl https://localhost:9090/SpringRequestMappingExample/home;
printf "

*****

";

echo "curl https://localhost:9090/SpringRequestMappingExample/home/xyz";
curl https://localhost:9090/SpringRequestMappingExample/home/xyz;
printf "

*****

";

echo "curl https://localhost:9090/SpringRequestMappingExample/home/method1";
curl https://localhost:9090/SpringRequestMappingExample/home/method1;
printf "

*****

";

echo "curl https://localhost:9090/SpringRequestMappingExample/home/method1/second";
curl https://localhost:9090/SpringRequestMappingExample/home/method1/second;
printf "

*****

";

echo "curl -X POST https://localhost:9090/SpringRequestMappingExample/home/method2";
curl -X POST https://localhost:9090/SpringRequestMappingExample/home/method2;
printf "

*****

";

echo "curl -X POST https://localhost:9090/SpringRequestMappingExample/home/method3";
curl -X POST https://localhost:9090/SpringRequestMappingExample/home/method3;
printf "

*****

";

echo "curl -X GET https://localhost:9090/SpringRequestMappingExample/home/method3";
curl -X GET https://localhost:9090/SpringRequestMappingExample/home/method3;
printf "

*****

";

echo "curl -H "name:pankaj" https://localhost:9090/SpringRequestMappingExample/home/method4";
curl -H "name:pankaj" https://localhost:9090/SpringRequestMappingExample/home/method4;
printf "

*****

";

echo "curl -H "name:pankaj" -H "id:1" https://localhost:9090/SpringRequestMappingExample/home/method5";
curl -H "name:pankaj" -H "id:1" https://localhost:9090/SpringRequestMappingExample/home/method5;
printf "

*****

";

echo "curl -H "Content-Type:text/html" https://localhost:9090/SpringRequestMappingExample/home/method6";
curl -H "Content-Type:text/html" https://localhost:9090/SpringRequestMappingExample/home/method6;
printf "

*****

";

echo "curl https://localhost:9090/SpringRequestMappingExample/home/method6";
curl https://localhost:9090/SpringRequestMappingExample/home/method6;
printf "

*****

";

echo "curl -H "Content-Type:text/html" -H "Accept:application/json" -i https://localhost:9090/SpringRequestMappingExample/home/method6";
curl -H "Content-Type:text/html" -H "Accept:application/json" -i https://localhost:9090/SpringRequestMappingExample/home/method6;
printf "

*****

";

echo "curl -H "Content-Type:text/html" -H "Accept:application/xml" -i https://localhost:9090/SpringRequestMappingExample/home/method6";
curl -H "Content-Type:text/html" -H "Accept:application/xml" -i https://localhost:9090/SpringRequestMappingExample/home/method6;
printf "

*****

";

echo "curl https://localhost:9090/SpringRequestMappingExample/home/method7/1";
curl https://localhost:9090/SpringRequestMappingExample/home/method7/1;
printf "

*****

";

echo "curl https://localhost:9090/SpringRequestMappingExample/home/method8/10/Lisa";
curl https://localhost:9090/SpringRequestMappingExample/home/method8/10/Lisa;
printf "

*****

";

echo "curl https://localhost:9090/SpringRequestMappingExample/home/method9?id=20";
curl https://localhost:9090/SpringRequestMappingExample/home/method9?id=20;
printf "

*****DONE*****

";

请注意，我已经在Tomcat-7上部署了web应用程序，它运行在端口9090上。SpringRequestMapping示例是应用程序的servlet上下文。现在，当我通过命令行执行这个脚本时，我得到以下输出。

pankaj:~ pankaj$ ./springTest.sh 
curl https://localhost:9090/SpringRequestMappingExample/home/method0
method0

*****

curl https://localhost:9090/SpringRequestMappingExample/home
default method

*****

curl https://localhost:9090/SpringRequestMappingExample/home/xyz
fallback method

*****

curl https://localhost:9090/SpringRequestMappingExample/home/method1
method1

*****

curl https://localhost:9090/SpringRequestMappingExample/home/method1/second
method1

*****

curl -X POST https://localhost:9090/SpringRequestMappingExample/home/method2
method2

*****

curl -X POST https://localhost:9090/SpringRequestMappingExample/home/method3
method3

*****

curl -X GET https://localhost:9090/SpringRequestMappingExample/home/method3
method3

*****

curl -H name:pankaj https://localhost:9090/SpringRequestMappingExample/home/method4
method4

*****

curl -H name:pankaj -H id:1 https://localhost:9090/SpringRequestMappingExample/home/method5
method5

*****

curl -H Content-Type:text/html https://localhost:9090/SpringRequestMappingExample/home/method6
method6

*****

curl https://localhost:9090/SpringRequestMappingExample/home/method6
fallback method

*****

curl -H Content-Type:text/html -H Accept:application/json -i https://localhost:9090/SpringRequestMappingExample/home/method6
HTTP/1.1 200 OK
Server: 阿帕奇-Coyote/1.1
Content-Type: application/json
Content-Length: 7
Date: Thu, 03 Jul 2014 18:14:10 GMT

method6

*****

curl -H Content-Type:text/html -H Accept:application/xml -i https://localhost:9090/SpringRequestMappingExample/home/method6
HTTP/1.1 200 OK
Server: 阿帕奇-Coyote/1.1
Content-Type: application/xml
Content-Length: 7
Date: Thu, 03 Jul 2014 18:14:10 GMT

method6

*****

curl https://localhost:9090/SpringRequestMappingExample/home/method7/1
method7 with id=1

*****

curl https://localhost:9090/SpringRequestMappingExample/home/method8/10/Lisa
method8 with id= 10 and name=Lisa

*****

curl https://localhost:9090/SpringRequestMappingExample/home/method9?id=20
method9 with id= 20

*****DONE*****

pankaj:~ pankaj$ 

尽管您可能需要检查default和fallback方法，但大多数都是可以自行理解的。那是为了Spring请求映射示例，我希望它能帮助您理解这个注解以及它的各种特性。您应该从下面的链接下载示例项目，并尝试不同的场景来进一步研究它。