@Detailed explanation of requestmapping

Hello everyone , I am a ~

Today's main introduction is Dora a One of the magic weapons of dreams —— Random door , We know that any door can lead to the place we want to reach , It's just a door , Open it and go to another place , It's amazing .
And in our Java web There is an equally magical magic weapon in development , It can save us a lot of time and code , So as to realize the mapping between browser and server , It is ——RequestMapping annotation , Now let's take a look .

List of articles

• • Preface
  • @RequestMapping
  • [email protected] Where to mark
  • • 1.1 Mark on the method
    • 1.2 Label on classes and methods
  • 2. @RequestMapping Properties of
  • • 2.1 @RequestMapping Of value attribute *
    • 2.2 @RequestMapping Of method attribute *
    • 2.3 @RequestMapping Of params attribute
    • 2.4 @RequestMapping Of headers attribute

@RequestMapping

Preface

We are in the actual development , There is not necessarily only one method in a controller , And these methods are used to process requests , So how can we match the request to the processing method one by one , Of course through RequestMapping Annotation to handle these mapping requests , It is used to specify what the controller can handle URL request .

@RequestMapping

@RequestMapping An annotation is an annotation used to handle the address mapping of a request , Can be used to map a request or a method , Can be used on classes or methods .

[email protected] Where to mark

1.1 Mark on the method

• For the method , Indicates that adding the address in the annotation on the method under the parent path of the class will access
  The method

  @Controller
  public class RequestMappingController {

  @RequestMapping("/testRequest")
  public String testRequest(){
      return "success";
  }
  

  }

At this time, the request path of the request mapped by the request mapping is ：http://http://localhost:8080/springmvc_study02/testRequest

Be careful ：springmvc_study02 Is the project name

1.2 Label on classes and methods

• For classes , This address is the parent path of all methods in the class that respond to requests .

  @Controller
  @RequestMapping(“/hello”)
  public class RequestMappingController {

  @RequestMapping("/testRequest")
  public String testRequest(){
      return "success";
  }
  

  }

At this time, the request path of the request mapped by the request mapping is ：http://localhost:8080/springmvc_study02/hello/testRequest

Be careful ： When you add... To a class RequestMapping After the note , If you want to request a mapping , This means that the request must first be mapped to the location of the annotation class , Then map to the method of this class . If not, the following errors will appear

2. @RequestMapping Properties of

• We can check the source code first ： Hold down Ctrl key , Mouse click RequestMapping Annotation, you can see the following interface
  
• In the source code, we can see @RequestMapping All attributes of , Then let's take a look at these properties

2.1 @RequestMapping Of value attribute *

• @RequestMapping Of value Property must be set to a value ;
• @RequestMapping Of value Property matches the request by the request address of the current request ;
• You can see from the source code above value Property is an array of string types , Therefore, it shows that multiple requests can be mapped to one method , Only need to value To specify an array containing multiple paths .

Set up value The value of the property ：

@Controller
public class RequestMappingController {

    @RequestMapping(value = {"/testRequest","/test"})
    public String testRequest(){
        return "success";
    }
}

Enter the following path in the browser to test ：


Be careful ： From the above two pictures, we can see , At this time, the request path of the request mapped by the request mapping is select value Any one of the arrays can .

2.2 @RequestMapping Of method attribute *

• @RequestMapping Of method Attribute is to match the request by the request mode of the current request ;
• Browser sends request to server , There are many ways to request GET、HEAD、POST、PUT、PATCH、DELETE、OPTIONS、TRACE. have access to method Property to constrain the request method .

Set request mode to get：

@Controller
public class RequestMappingController {

    @RequestMapping(value = "/testRequest",method = RequestMethod.GET)
    public String testRequest(){
        return "success";
    }
}

With post Mode request ：

<form th:action="@{/testRequest}" method="post">
    <input type="submit">
</form>

Request the results ：

Be careful ： We are @RequestMapping Add a method to the annotation to limit ：method = RequestMethod.GET, Then the request must be get Of , Otherwise, the above error will occur .

The mapping method clearly requires that the request method is get, therefore post The method is not allowed , Only modify to get, To be able to request success , If you want to support both ways , Just in @RequestMapping Annotated method Add another method to the property , Separated by commas .

Expand ：

• @GetMapping： Handle get Method requested mapping

• @PostMapping： Handle post Method requested mapping

• @PutMapping： Handle put Method requested mapping

• @DeleteMapping： Handle delete Method requested mapping

  @GetMapping Equivalent to @RequestMapping(method=RequestMethod.GET), It will be get Map to a specific method .

Usage mode ：@GetMapping(value = "/testRequest")

2.3 @RequestMapping Of params attribute

@RequestMapping Of params Attribute is to match the request parameters of the current request ;
@RequestMapping Of params Property is an array of string types , You can set the matching relationship through the following four expressions

• “param”： The request that requires a request mapping must be one that contains param Request parameters for
• “!param”： Requests that require mapping cannot contain param Request parameters for
• “param=value”： Requests that require request mapping must contain param Request parameters for , And param The value of the parameter must be value
• “param!=value”： Requests that require request mapping must contain param Request parameters for , Its value cannot be value.

Set up params The property value of is username：

@RequestMapping(value = "/test",params = "username")
    public String test(){
        return "success";
    }

Request the results ：

Be careful ： We set it up params attribute , This means that the request mapped to the request must contain username To be able to request success .

When we pass in parameters, we use http://localhost:8080/springmvc_study02/test?username Path to visit , Let's see the results ：

When params Property when setting multiple property values , It must be satisfied at the same time to request success , Otherwise, the following error will appear

2.4 @RequestMapping Of headers attribute

@RequestMapping Of headers Property is to match the request through the request header information of the current request ;
@RequestMapping Of headers Property is an array of string types , You can set the matching relationship through the following four expressions

• “header”： The request that requires a request mapping must be one that contains header Request header information for
• “!header”： Requests that require request mapping must be requests that do not contain header Request header information for
• “header=value”： The request that requires a request mapping must be one that contains header Request header information for , also header The value of must be value
• “header!=value”： The request that requires a request mapping must be one that contains header Request header information for , also header The value of must not be value

Set the request header information ：

 @RequestMapping(value = "/test",headers = "Host = localhost:8081")
    public String test(){
        return "success";
    }

Request the results ：

Be careful ： If the current request is not satisfied headers attribute , The page will show 404 error , That is, the resource was not found .

After learning this magic weapon , Does it feel very interesting , Well, let's go and have a try .