ajax中設置contentType: “application/json”的作用

最近在做項目交互的時候，剛開始向后台傳遞數據返回415，后來百度添加了 contentType："application/json" 之后返回400，然后把傳輸的數據格式改為json字符串就傳輸成功了，現在我們來看看 contentType：“application/json“的作用：

添加 contentType：“application/json“之后，向后台發送數據的格式必須為json字符串

$.ajax({
    type: "post",
    url:  "mobile/notice/addMessageInfo.jspx",
    contentType: "application/json",
    data:"{'name':'zhangsan','age':'15'}",
    dataType: "json",
    success: function(data) {
        console.log(data);
    },
    error: function(msg) {
        console.log(msg)
    }
})

不添加 contentType：“application/json“的時候可以向后台發送json對象形式

$.ajax({
    type: "post",
    url:  "mobile/notice/addMessageInfo.jspx",
    data:{name:'zhangsan',age:'15'},
    dataType: "json",
    success: function(data) {
        console.log(data);
    },
    error: function(msg) {
        console.log(msg)
    }
})

另外，當向后台傳遞復雜json的時候，同樣需要添加 contentType：“application/json“，然后將數據轉化為字符串

var data = {
    uploadarray: uploadarray,
    messageInfo: {
        messageTitle: messageTitle,
        messageContent: messageContent,
        publisher: publisher
    },
    userId: userId
}

$.ajax({  
    type: 'post',
    url: "mobile/notice/addMessageInfo.jspx",
    contentType: 'application/json', data: JSON.stringify(data),
    dataType: "json",
    success: function(data) {
        console.log(data);
    },
    error: function(msg) {
        console.log(msg)
    }
})