javascript无法将Json数据从Ajax发送到Servlet

Question

我试图使用Ajax将JSON数据从JavaScript函数发送到Servlet

客户端：

function addObject() {
    var data = {
        aa: "aa",
        bb: "bb"
    }
    var string = JSON.stringify(data);
    var xhttp = new XMLHttpRequest();
    xhttp.open("POST", "GalleryAdd", true);
    xhttp.setRequestHeader("Content-Type", "application/json");
    xhttp.onreadystatechange = function () {
        if (this.readyState == 4 && this.status == 200) {
            console.log("Done");
        }
    };
    console.log(string);
    xhttp.send(string);
}

stringyfied数据的输出是{"aa":"aa","bb":"bb"}

Servlet：

protected void doPost(HttpServletRequest request, HttpServletResponse response) {
    log(request.getParameter("aa"));
    log(request.getParameter("bb"));
}

记录器中的输出是null和null

看起来JavaScript不会向servlet发送数据，如果字符串化正确的话。有人吗

Answer 1

Json对象位于请求体中，因此需要解析InputStream。试试这个

protected void doPost(HttpServletRequest req, HttpServletResponse resp) {
    JsonObject object = Json.createReader(req.getInputStream()).readObject();

    log(object.getString("aa"));
    log(object.getString("bb"));
}