jquery's Ajax default contenttype and data format

$.ajax of jquery (Url,[settings])
1. The default contenttype value is: application/x-www-form-urlencoded; Charset=utf-8
This format is the form submission format, the data is key1=value1&key2=value2 format
2. Although the Data property value of Ajax is in the format: {key1:value1,key2:value2}, it will eventually be submitted to the background in key1=value1&key2=value2 format
3. If Ajax is to interact with SPRINGMVC, the key1=value1&key2=value2 format, the background SPRINGMVC only need to define the object or parameters on the line, will be automatically mapped.
4. If the SPRINGMVC parameter has @requestbody annotations (receive json** String * * Format data), Ajax must convert the Date property value to a JSON string, not a JSON object (JS object, which will automatically be converted to Key=value form). Also, the value of the modified contenttype is: Application/json; Charset=utf-8, this adds the properties of the @requestbody annotation to customize the mapping to the value