Content-type explanations in HTTP requests and their application in spring MVC

Introduction: In HTTP requests, we use Content-type every day to specify different formats of request information, but few people have a thorough understanding of how many values are allowed in Content-type, and this will explain content-type available values, as well as the spring How they are used in MVC to map request information.

1. Content-type

MediaType, which is the Internet media type, the Internet medium, or the MIME type, in the HTTP protocol message header, uses Content-type to represent the media type information in the specific request.

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1. Type format: Type/subtype (;p arameter)? Type
2. The main type, arbitrary string, such as text, if the * number represents all;
3. Subtype subtype, arbitrary string, such as HTML, if the * number represents all;
4. Parameter optional, some parameters, such as the Q parameter of the Accept request header, Content-type the charset parameter.

For example: Content-type:text/html;charset:utf-8;

The common media format types are as follows:

• text/html:html format
• Text/plain: Plain Text Format
• Text/xml:xml format
• Image/gif:gif Picture Format
• Image/jpeg:jpg Picture Format
• Image/png:png Picture Format

Types of media formats that start with application:

• application/xhtml+xml:xhtml format
• Application/xml:xml data format
• Application/atom+xml:atom XML Aggregation format
• Application/json:json data format
• Application/pdf:pdf format
• Application/msword:word Document Format
• Application/octet-stream: binary stream data (e.g., common file downloads)
• application/x-www-form-urlencoded: <form enctype= "" > Default enctype,form form data is encoded as key/ The value format is sent to the server (the format of the form's default submission data)

Another common media format is used when uploading files:

• Multipart/form-data: When you need to upload a file in a form, you need to use that format

These are some of the content-type content formats that we often use in our daily development.

2. About the use of Content-type type information in Spring MVC

First, let's look at the class definition in requestmapping:

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2. @Target ({elementtype.method, elementtype.type})
4. @Retention (Retentionpolicy.runtime)
6. @Documented
8. @Mapping
10. Public @interface requestmapping {
12. String[] Value () default {};
14. Requestmethod[] Method () default {};
16. String[] Params () default {};
18. String[] Headers () default {};
20. String[] Consumes () default {};
22. String[] produces () default {};
24. }

Value: Specifies the actual address of the request, such as/action/info.
Method: Specifies the type of method requested, GET, POST, PUT, delete, etc.
Consumes: Specifies the type of submission to process the request (Content-type), such as Application/json, text/html;
Produces: Specifies the type of content returned, only if the type in the request header (Accept) contains the specified type to return
Params: Specifies that certain parameter values must be included in the request for the method to process
Headers: Specifies that certain header values must be included in the request in order for the method to process requests

Among them, consumes, produces use Content-typ information to filter information, headers can use Content-type to filter and judge.

3. Using the example

3.1 Headers

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1. @RequestMapping (value = "/test", method = requestmethod.get, headers="referer=http:// www.ifeng.com/")
2. public void Testheaders (@PathVariable string ownerid, @PathVariable string petid) {
3. Implementation omitted
4. }

The headers inside can match all the information that can appear in the header, not limited to the referer information.

Example 2

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2. @RequestMapping (value = "/response/contenttype", headers = "Accept=application/json")
4. public void Response2 (HttpServletResponse response) throws IOException {
6. The media type that represents the content area data for the response is in JSON format and is encoded as UTF-8 (the client should decode with Utf-8)
8. Response.setcontenttype ("Application/json;     charset=utf-8 ");
10. Write out the response body content
12. String jsondata = "{\"username\ ": \" zhang\ ", \" password\ ": \" 123\ "}";
14. Response.getwriter (). write (Jsondata);
16. }

The server produces JSON data based on the request header "Accept=application/json".

When you have the following accept header, you will follow the following rules to apply:
①accept:text/html,application/xml,application/json
The produces matching is performed in the following order ①text/html②application/xml③application/json
②accept:application/xml;q=0.5,application/json;q=0.9,text/html
The produces matching is performed in the following order ①text/html②application/json③application/xml
parameter is the mass factor of the media type, the higher the priority (from 0 to 1)
③accept:*/*,text/*,text/html
The produces matching is performed in the following order ①text/html②text/*③*/*

That is, the matching rule is: the most explicit priority match.

Requests part

Header	explain	Example
Accept	Specify what types of content clients can receive	Accept:text/plain, text/html
Accept-charset	The set of character encodings that the browser can accept.	Accept-charset:iso-8859-5
Accept-encoding	Specifies that the Web server that the browser can support returns the content compression encoding type.	Accept-encoding:compress, gzip
Accept-language	Browser-acceptable language	Accept-language:en,zh
Accept-ranges	You can request one or more child range fields for a Web page entity	Accept-ranges:bytes
Authorization	Authorization Certificate for HTTP Authorization	Authorization:basic qwxhzgrpbjpvcgvuihnlc2ftzq==
Cache-control	Specify the caching mechanism that requests and responses follow	Cache-control:no-cache
Connection	Indicates whether a persistent connection is required. (HTTP 1.1 defaults to persistent connection)	Connection:close
Cookies	When an HTTP request is sent, all cookie values stored under that request domain are sent to the Web server.	Cookie: $Version = 1; Skin=new;
Content-length	The requested content length	content-length:348
Content-type	The requested MIME information corresponding to the entity	content-type:application/x-www-form-urlencoded
Date	Date and time the request was sent	Date:tue, 08:12:31 GMT
Expect	The specific server behavior of the request	Expect:100-continue
From	Email from the user who made the request	From: [Email protected]
Host	Specify the domain name and port number of the requested server	Host:www.zcmhi.com
If-match	Only valid if the request content matches the entity	If-match: "737060cd8c284d8af7ad3082f209582d"
If-modified-since	If the requested part is modified after the specified time, the request succeeds, and the 304 code is returned without modification	If-modified-since:sat, Oct 19:43:31 GMT
If-none-match	If the content does not change the return 304 code, the parameter is the server's previously sent ETag, and the server responded to the ETag comparison to determine whether the change	If-none-match: "737060cd8c284d8af7ad3082f209582d"
If-range	If the entity does not change, the server sends the missing portion of the client, otherwise the entire entity is sent. The parameters are also ETag	If-range: "737060cd8c284d8af7ad3082f209582d"
If-unmodified-since	Request succeeds only if the entity has not been modified since the specified time	If-unmodified-since:sat, Oct 19:43:31 GMT
Max-forwards	Limit the time that information is transmitted through agents and gateways	Max-forwards:10
Pragma	Used to include implementation-specific instructions	Pragma:no-cache
Proxy-authorization	Connect to an authorization certificate for the agent	Proxy-authorization:basic qwxhzgrpbjpvcgvuihnlc2ftzq==
Range	Request only part of an entity, specify a range	range:bytes=500-999
Referer	The address of the previous page, which is immediately followed by the current request page,	Referer:http://www.zcmhi.com/archives/71.html
TE	The client is willing to accept the transfer encoding and notifies the server to accept the trailing header information	te:trailers,deflate;q=0.5
Upgrade	Specify some kind of transport protocol to the server for the server to convert (if supported)	upgrade:http/2.0, shttp/1.3, irc/6.9, rta/x11
User-agent	The content of the user-agent contains the user information that made the request	user-agent:mozilla/5.0 (Linux; X11)
Via	Notifies the intermediary gateway or proxy server address, communication protocol	via:1.0 Fred, 1.1 nowhere.com (apache/1.1)
Warning	About warning messages for message entities	warn:199 Miscellaneous Warning

Responses part

Header	explain	Example
Accept-ranges	Indicates whether the server supports the specified range request and what kind of staging request	Accept-ranges:bytes
Age	Estimated time (in seconds, non-negative) from the original server to the proxy cache	Age:12
Allow	A valid request behavior for a network resource is not allowed to return 405	Allow:get, HEAD
Cache-control	Tell if all caching mechanisms can be cached and which type	Cache-control:no-cache
Content-encoding	The type of return content compression encoding supported by the Web server.	Content-encoding:gzip
Content-language	The language of the response body	Content-language:en,zh
Content-length	The length of the response body	content-length:348
Content-location	Alternate alternative address to request resource substitution	Content-location:/index.htm
Content-md5	Returns the MD5 checksum value of a resource	content-md5:q2hly2sgsw50zwdyaxr5iq==
Content-range	The byte position of this section in the entire return body	Content-range:bytes 21010-47021/47022
Content-type	Returns the MIME type of the content	content-type:text/html; Charset=utf-8
Date	Time the original server message was issued	Date:tue, 08:12:31 GMT
ETag	The current value of the entity label of the request variable	ETag: "737060cd8c284d8af7ad3082f209582d"
Expires	Date and time when the response expires	Expires:thu, 16:00:00 GMT
Last-modified	Requested last modified time for resource	Last-modified:tue, 12:45:26 GMT
Location	Used to redirect the receiver to the location of the non-request URL to complete the request or identify the new resource	Location:http://www.zcmhi.com/archives/94.html
Pragma	Includes implementing a specific instruction that can be applied to any receiver on the response chain	Pragma:no-cache
Proxy-authenticate	It indicates the authentication scheme and the parameters on the URL that can be applied to the proxy	Proxy-authenticate:basic
Refresh	Applied to redirect or a new resource was created, redirected after 5 seconds (proposed by Netscape, supported by most browsers)	Refresh:5; Url=http://www.zcmhi.com/archives/94.html
Retry-after	Notifies the client to try again after a specified time if the entity is temporarily undesirable	retry-after:120
Server	Web Server Software Name	server:apache/1.3.27 (Unix) (Red-hat/linux)
Set-cookie	Set HTTP Cookies	Set-cookie:userid=johndoe; max-age=3600; Version=1
Trailer	Indicates that the header domain is present at the end of the chunked transfer code	Trailer:max-forwards
Transfer-encoding	File transfer encoding	Transfer-encoding:chunked
Vary	Tells the downstream agent whether to use the cache response or request from the original server	Vary: *
Via	Tells the proxy client where the response was sent by	via:1.0 Fred, 1.1 nowhere.com (apache/1.1)
Warning	Warning about possible issues with the entity	warning:199 Miscellaneous Warning
Www-authenticate	Indicates the authorization scheme that the client request entity should use	Www-authenticate:basic

Example of 3.2 params

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1. @RequestMapping (value = "/test/{userid}", method = requestmethod.get, params="myparam= MyValue ")
2. public void Finduser (@PathVariable String userId) {
3. Implementation omitted
4. }

A request with the name "Myparam" and a value of "MyValue" is included in the processing request, which acts as a filter.

3.3 Consumes/produces

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2. @Controller
4. @RequestMapping (value = "/users", method = requestmethod.post, consumes="Application/json", produces="Application/json")
6. @ResponseBody
8. Public List<user> AddUser (@RequestBody user userl) {
10. Implementation omitted
12. return List<User> users;
14. }

The Content-type method only processes requests with the request "Application/json" type. The produces identity ==> handles the request that contains "Application/json" in the Accept header of the request, and implies that the returned content type is Application/json;

4. Summary

In this article, we first introduced the main supported format content of Content-type, and then introduced the main use method based on the content of @requestmapping annotation, in which, headers, consumes,produces, Is the use of content-type in the various media format content, can be based on this format content for access control and filtering.

Content-type explanations in HTTP requests and their application in spring MVC