@RequestMapping is one of the most widely used Spring MVC annotation. 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
.
@RequestMapping with Class: We can use it with class definition to create the base URI. For example:
@Controller
@RequestMapping("/home")
public class HomeController {
}
Now /home is the URI for which this controller will be used. This concept is very similar to servlet context of a web application.
@RequestMapping with Method: We can use it with method to provide the URI pattern for which handler method will be used. For example:
@RequestMapping(value="/method0")
@ResponseBody
public String method0(){
return "method0";
}
Above annotation can also be written as @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.
@RequestMapping with Multiple URI: We can use a single method for handling multiple URIs, for example:
@RequestMapping(value={"/method1","/method1/second"})
@ResponseBody
public String method1(){
return "method1";
}
If you will look at the source code of RequestMapping annotation, you will see that all of it’s variables are arrays. We can create String array for the URI mappings for the handler method.
@RequestMapping with HTTP Method: Sometimes we want to perform different operations based on the HTTP method used, even though request URI remains same. We can use @RequestMapping method variable to narrow down the HTTP methods for which this method will be invoked. For example:
@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";
}
@RequestMapping with Headers: We can specify the headers that should be present to invoke the handler method. For example:
@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";
}
@RequestMapping with Produces and Consumes: We can use header Content-Type
and Accept
to find out request contents and what is the mime message it wants in response. For clarity, @RequestMapping provides produces and consumes variables where we can specify the request content-type for which method will be invoked and the response content type. For example:
@RequestMapping(value="/method6", produces={"application/json","application/xml"}, consumes="text/html")
@ResponseBody
public String method6(){
return "method6";
}
Above method can consume message only with Content-Type as text/html and is able to produce messages of type application/json and application/xml.
@RequestMapping with @PathVariable: RequestMapping annotation can be used to handle dynamic URIs where one or more of the URI value works as a parameter. We can even specify Regular Expression for URI dynamic parameter to accept only specific type of input. It works with @PathVariable annotation through which we can map the URI variable to one of the method arguments. For example:
@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;
}
```
@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.
```
@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.
```
@RequestMapping("*")
@ResponseBody
public String fallbackMethod(){
return "fallback method";
}
```
We can use Spring RestTemplate to test the different methods above, but today I will use cURL commands to test these methods because these are simple and there are not much data flowing around. I have created a simple shell script springTest.sh to invoke all the above methods and print their output. It looks like below.
#!/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";
Note that I have deployed my web application on Tomcat-7 and it’s running on port 9090. SpringRequestMappingExample is the servlet context of the application. Now when I execute this script through command line, I get following output.
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$
Most of these are self understood, although you might want to check default and fallback methods. That’s all for Spring RequestMapping Example, I hope it will help you in understanding this annotation and it’s various features. You should download the sample project from below link and try different scenarios to explore it further.
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Hi Pankaj, if we have placed multiple request mapping in our class with a fallback then request will be handled by which of the request mapping/method handler, fallback or matching handler. Given below 2 sequences - 1. @RequestMapping(*) @ResponseBody public String fallbackMethod(){} @RequestMapping(“/home”) @ResponseBody public String home(){} 2. @RequestMapping(“/home”) @ResponseBody public String home(){} @RequestMapping(*) @ResponseBody public String fallbackMethod(){} Please let me know in both cases which method will run for “/home” and why? Thanks
- RAMAM
Hi Pankaj, Its Really helpful in understanding basics
- Thiyagarajan
Hi Pankaj, Thanks for explaining it from basic and providing enough explanatory examples.
- Rohit
Well Explained, Thanks.!
- Arif Heer
Hi, I have request URL as
https://localhost:8080/api?arg=10
when I am trying to get arg using @RequestParam I am getting a null value. How to get XML contention as String?- Hari
can some please help me answering how is a url template with integer value generated: “https://localhost:8080/springmvc/hello/101” It is about @PathVariable. How to pass integer value along with url in the above form? How does this happen dynamically? Thanks
- arun singh
How to make the requestParam key as case insensitive? For Example : public String welcome(@RequestParam(“orgID”) String orgID, ModelMap model) The request parameter “orgID” should be case insensitive. How to do this ?. I should be able to give the query-string as “orgid” or “orgId”. The parameter should be completely case-insensitive.
- Sheela
thanks
- arun singh
Thanking you
- Prakash
Thank you sir very nice explanation on each annotations
- NAVEENSNH