HBuilder plus.uploader.createUpload 上传图片

task.addFile();里面的参数代表什么意思呀???
这样传图片到后台,用servlet接收代码应该怎么去写呢,各位帮帮忙找找示例的代码,,,

var wt = plus.nativeUI.showWaiting();
var task = plus.uploader.createUpload("servlet/Recognition", {method: "POST"
},
function(t, status) {
if(status == 200) {
console.log("上传成功:" + t.responseText);
wt.close();
} else {
console.log("上传失败:" + status);
wt.close();
}
}
);
task.addFile(pictureUrl, {key: name});
task.start();

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