Content-type explanations in HTTP requests and produce and consumes configuration in spring MVC annotations

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.
[HTML] view plain Copy type format: Type/subtype (;p arameter)? Type main type, any string, such as text, if the * symbol represents all; Subtype subtype, arbitrary string, such as HTML, if the * number represents all; parameter optional, some parameters, such as the Q parameter of the Accept request header, Content-typ     The charset parameter of E. 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

Media format type starting with application: application/xhtml+xml:xhtml format application/xml:xml data format Application/atom+xml:atom X ML aggregation format
Application/json:json data Format application/pdf:pdf format
Application/msword:word Document Format application/octet-stream: binary stream data (such as common file downloads) application/x-www-form-urlencoded: <f ORM enctype= "" > The default enctype,form form data is encoded in Key/value format sent to the server (form default submission data format)

Another common media format is 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:
[HTML]View Plain Copy @Target ({elementtype.method, elementtype.type}) @Retention (retentionpolicy.runtime) @Documented @Map         Ping public @interface requestmapping {string[] value () default {};         Requestmethod[] Method () default {};         String[] Params () default {};         String[] Headers () default {};         String[] Consumes () default {};   String[] produces () default {}; } 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
[HTML] view plain copy @RequestMapping (value = "/test", method = Requestmethod.get, headers= "referer=http://www . ifeng.com/") public void Testheaders (@PathVariable string ownerid, @PathVariable string petid) {//Impleme Ntation omitted} Here the headers inside can match all the information that can appear in the header, not limited to the referer information.

Example 2
[HTML] view plain copy @RequestMapping (value = "/response/contenttype", headers = "Accept=application/json") public void Response2 (HttpServletResponse response) throws IOException {//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         Decoding with Utf-8) Response.setcontenttype ("Application/json;charset=utf-8");         Write the response body content String Jsondata = "{\" username\ ": \" zhang\ ", \" password\ ": \" 123\ "}";     Response.getwriter (). write (Jsondata); 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