SpringMVC+JSP中关于JQuery ajax提交的Content-Type参数设置application/json和application/x-www-form-urlencoded区别

页面是用的JSP，后台用的Spring MVC

使用JQuery的ajax需要设置Content-Type，Content-Type的设置有以下几种常用的

"Content-Type": "application/x-www-form-urlencoded"    //适用于大部分情况
"Content-Type": "application/json"    //适用于复杂JSON数据的提交
"Content-Type": "multipart/form-data"    //适用于文件上传

application/x-www-form-urlencoded

application/x-www-form-urlencoded是JQuery ajax默认的提交方式，当不写contentType时即是此种方式，代表使用表单形式提交。

JSP：

$.ajax({
  type: "POST",
  url: "${basePath}/comment",
  contentType: "application/x-www-form-urlencoded", 
  dataType: "json", //表示返回值类型，不必须
  data: {comment: 'appblog.cn'},
  success: function (result) {
    alert(result);
  }
});

后台：

@RequestMapping(value = "/order/{orderId}", method = RequestMethod.POST)
@ResponseBody
public Result reviewOrder(@PathVariable("orderId") Long orderId, HttpServletRequest request) {
    String comment = request.getParameter("comment");

}

application/json

使用application/x-www-form-urlencoded只能提交简单类型的json数据，当json数据很复杂时就须要使用application/json

JSP：

$.ajax({
  type: "POST",
  url: "${basePath}/comment",
  contentType: "application/json", //必须有
  dataType: "json", //表示返回值类型，不必须
  data: JSON.stringify({'comment': 'appblog.cn'}),
  success: function (result) {
    alert(result);
  }
});

后台

@RequestMapping(value = "/order/{orderId}", method = RequestMethod.POST)
@ResponseBody
public Result reviewOrder(@PathVariable("orderId") Long orderId, @RequestBody Review review, HttpServletRequest request) {
    String comment1 = request.getParameter("ids");    //输出null
    String comment2 = review.getComment();
}

public class Review {
    String comment;

    public String getComment() {
        return comment;
    }

    public void setComment(String comment) {
        this.comment = comment;
    }
}

也可以使用JSONObject

@RequestMapping(value = "/order/{orderId}", method = RequestMethod.POST)
@ResponseBody
public Result reviewOrder(@PathVariable("orderId") Long orderId, @RequestBody JSONObject object, HttpServletRequest request) {
    String comment = object.getString("comment");
}

总结：当使用application/x-www-form-urlencoded时其实JSP会默认把json数据认为是一个对象，而使用application/json时需要向后台传入一个JSON字符串，所以要用JSON.stringify函数把JSON对象转成json字符串。