将XML请求主体转换为字符串

Question

我有一个简单的express应用程序，它接收POST请求的主体（以XML形式）并将其推送到Amazon S3存储桶上的文件中。

我的POST路由如下：

var port = process.env.PORT || 3000
    , express = require("express")
    , app = express()
    , aws = require('aws-sdk')
    , xmlParser = require("express-xml-bodyparser");

//App Config
app.set("view engine", "ejs");
app.use(express.static("public"));
app.use(xmlParser());

//Set up AWS S3 instance
aws.config.update({
    accessKeyId: "id"
    , secretAccessKey: "key"
});

var s3 = new aws.S3();

//Post route
app.post("/", function(req, res) {

    var params = {
        Bucket: 'bucket'
        , Key: req.get("Filename")
        , Body: req.body
        , ACL: "public-read"
    };

    s3.putObject(params, function(perr, pres) {
        if (perr) {
            res.writeHead(500, 'Unable to write to S3 bucket', {
                'Content-Type': 'text/plain'
            });
            res.end();
            console.log("Error uploading data: ", perr);
        } else {
            console.log("Successfully uploaded data to bucket/" + req.get("Filename"));
        }
    });

    res.writeHead(200, 'OK', {
        'Content-Type': 'text/plain'
    });
    res.end();
});

但是，由于params对象的Body变量需要为字符串，但由于作为对象而出现，因此出现错误。

如何将XML主体转换为可以保存到S3实例的XML字符串？