Spring MVC @RequestMapping 注解示例，包括控制器、方法、标题、参数、@RequestParam、@PathVariable

@RequestMapping是最常用的Spring MVC注解之一。org.springframework.web.bind.annotation.RequestMapping注解用于将Web请求映射到特定的处理器类和/或处理器方法上。 @RequestMapping可以应用于控制器类和方法。今天我们将通过示例和其他注解@PathVariable和@RequestParam来详细介绍该注解的各种用法。

Spring @RequestMapping

1. @RequestMapping与类一起使用：我们可以将其与类定义一起使用，以创建基本URI。例如：

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

   现在，/home是将使用此控制器的URI。这个概念与Web应用程序的servlet上下文非常相似。

2. @RequestMapping與方法一起使用：我們可以在方法中使用它來提供處理程序方法將被使用的URI模式。例如：

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

   上面的註釋也可以寫成@RequestMapping("/method0")。另外一個注意事項是，我正在使用@ResponseBody來發送String型態的回應給這個網路請求，這是為了讓範例簡單。和我以往一樣，我將在Spring MVC應用程式中使用這些方法並使用一個簡單的程式或腳本來測試它們。

3. @RequestMapping處理多個URI：我們可以使用單一方法來處理多個URI，例如：

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

   如果您查看RequestMapping註解的原始碼，您會看到它的所有變數都是陣列。我們可以為處理方法的URI映射建立字串陣列。

4. @RequestMapping與HTTP方法：有時我們希望根據使用的HTTP方法執行不同的操作，即使請求URI保持不變。我們可以使用@RequestMapping方法變量來縮小此方法將被調用的HTTP方法範圍。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. @RequestMapping與標頭：我們可以指定應該存在的標頭以調用處理程序方法。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. @RequestMapping with Produces and Consumes: 我们可以使用标头Content-Type和Accept来确定请求的内容和所需的响应的MIME类型。为了清晰起见，@RequestMapping提供了produces和consumes变量，可以在其中指定调用的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";
   }
   

   上述方法只能接受Content-Type为text/html的消息，并能够生成类型为application/json和application/xml的消息。

Spring @PathVariable

8. @RequestMapping和@PathVariable：RequestMapping注解可以用于处理动态的URI，其中一个或多个URI值可以作为参数。我们甚至可以为URI动态参数指定正则表达式，以接受特定类型的输入。它与@PathVariable注解一起使用，通过它我们可以将URI变量映射到方法参数之一。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

10. @RequestMapping與@RequestParam用於URL參數：有時我們在請求URL中獲取參數，主要是在GET請求中。我們可以使用@RequestMapping與@RequestParam註釋來檢索URL參數並將其映射到方法參數。例如：

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

For this method to work, the parameter name should be "id" and it should be of type int.

11. @RequestMapping默認方法：如果方法的值為空，則該方法作為控制器類的默認方法。例如：

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

As you have seen above that we have mapped `/home` to `HomeController`, this method will be used for the default URI requests.

12. @RequestMapping回退方法：我們可以為控制器類創建一個回退方法，以確保捕獲所有客戶端請求，即使沒有匹配的處理程序方法。當沒有處理程序方法處理請求時，這對於向用戶發送自定義404響應頁面非常有用。

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

Spring RestMapping測試程序

我們可以使用Spring RestTemplate來測試上述不同的方法，但今天我將使用cURL命令來測試這些方法，因為它們簡單且沒有太多數據流動。我已經創建了一個簡單的shell腳本springTest.sh來調用上述所有方法並打印它們的輸出。它看起來如下。

#!/bin/bash

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

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

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

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

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

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

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

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

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

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 "\n\n*****\n\n";

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 "\n\n*****\n\n";

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

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 "\n\n*****\n\n";

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 "\n\n*****\n\n";

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

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

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

請注意，我已經將我的Web應用程序部署在Tomcat-7上，它運行在9090端口上。 SpringRequestMappingExample是應用程序的Servlet上下文。現在，當我通過命令行執行此腳本時，我獲得以下輸出。

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: Apache-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: Apache-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$ 

大部分都是自我理解的，不过你可能想要检查默认和回退方法。以上是有关Spring RequestMapping示例的全部内容，希望能帮助你理解这个注解及其各种特性。你可以从下方链接下载示例项目，并尝试不同的场景来进一步探索。

下载Spring MVC RequestMapping项目