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

最近在做項目交互的時候，剛開始向後臺傳遞數據返回415，後來百度添加了 contentType：“application/json“之後返回400，然後把傳輸的數據格式改爲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“之後，向後臺發送數據的格式必須爲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“的時候可以向後臺發送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，當向後臺傳遞複雜json的時候，同樣需要添加 contentType：“application/json“，然後將數據轉化爲字符串

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)
    }
})