英文:
How to access contents posted and received to backend
问题
前端代码部分:
如下所示，对于前端部分，我调用了`getTIFFForSubsetAsNIRRange/`的webservice，并希望发送`body`中显示的内容。该webservice成功调用，但无法获取到发送给它的`body`内容。
如下所示，在后端部分，我使用了`req.data`，但它返回`undefined`。
请告诉我如何访问发送到后端的内容。
尝试解决方法：
```lang-js
let data = req.body;
res.send('Data Received: ' + JSON.stringify(data));
但它会导致错误：
UnhandledPromiseRejectionWarning: Error [ERR_HTTP_HEADERS_SENT]: Cannot set headers after they are sent to the client
前端代码：
```lang-js
drawEvt.on('drawend', e => {
let feature = e.feature;
let geom = feature.getGeometry();
let wktformat = new WKT();
let geoJSONformat = new GeoJSON();
let wktRepresenation = wktformat.writeGeometry(geom);
let geoJSONRepresentation = geoJSONformat.writeGeometry(geom);
this.wktRepresenation = wktRepresenation;
this.geoJSONRepresentation = geoJSONRepresentation;
console.info(debugTag, 'drawEvt.on' + 'wktRepresenation:', this.wktRepresenation);
console.info(debugTag, 'drawEvt.on' + 'geoJSONRepresentation:', this.geoJSONRepresentation);
const requestOptions = {
method: 'POST',
headers: { 'Content-Type': 'application/json' },
body: JSON.stringify({ wktRepresenation: this.wktRepresenation }),
};
fetch('http://localhost:4000/getTIFFForSubsetAsNIRRange/', requestOptions)
.then(response => response.json())
.then(data => (this.postId = data.id));
});
后端代码：
app.post('/getTIFFForSubsetAsNIRRange/', async (req, res, next) => {
console.log(res.send(req.body))
return 'OK';
});
app.listen(port, () => {
console.log('listening to port', port);
});
请注意，前端部分的代码中有一个逗号，可能是多余的，可以去掉。
英文:
as shown in the code posted below, for the front-end part, I invoking the webservice getTIFFForSubsetAsNIRRange/ and I want to send the contents shown in body the webservice is invoked successfully but i can not get the body posted to it.
As shown below in the back-end side, I used req.data but it returns undefined
Please let me know how to have access to the contents sent to the backend
attempts to solve it
let data = req.body;
res.send('Data Received: ' + JSON.stringify(data));
but it results in an error:
UnhandledPromiseRejectionWarning: Error [ERR_HTTP_HEADERS_SENT]: Cannot set headers after they are sent to the client
front-end:
drawEvt.on('drawend', e => {
let feature = e.feature;
let geom = feature.getGeometry();
let wktformat = new WKT();
let geoJSONformat = new GeoJSON();
let wktRepresenation = wktformat.writeGeometry(geom);
let geoJSONRepresentation = geoJSONformat.writeGeometry(geom);
this.wktRepresenation = wktRepresenation;
this.geoJSONRepresentation = geoJSONRepresentation;
console.info(debugTag, 'drawEvt.on' + 'wktRepresenation:', this.wktRepresenation);
console.info(debugTag, 'drawEvt.on' + 'geoJSONRepresentation:', this.geoJSONRepresentation);
const requestOptions = {
method: 'POST',
headers: { 'Content-Type': 'application/json' },
body: JSON.stringify({ wktRepresenation: this.wktRepresenation }),
,
};
fetch('http://localhost:4000/getTIFFForSubsetAsNIRRange/', requestOptions)
.then(response => response.json())
.then(data => (this.postId = data.id));
});
back-end
app.post('/getTIFFForSubsetAsNIRRange/', async (req, res, next) => {
console.log(res.send(req.body))
return 'OK'
});
app.listen(port, () => {
console.log('listening to port', port);
});
答案1
得分: 1
使用res.json发送JSON数据：
app.post('/getTIFFForSubsetAsNIRRange/', async (req, res, next) => {
console.log('posted wktRepresenation is:\n', req.body.wktRepresenation);
// 处理req.body.wktRepresenation的操作
// 发送一些JSON数据
res.json({ myProperty: 'myProperty value' }); // 应该显示在response.json()中
});
总结一下，你需要：
- 使用
fetch来发送JSON请求 - 在服务器上设置JSON解析器来处理发送的JSON数据
- 使用
req.body来访问发送的数据 - 使用
res.json来发送一些JSON数据
英文:
Use res.json to send back JSON data:
app.post('/getTIFFForSubsetAsNIRRange/', async (req, res, next) => {
console.log('posted wktRepresenation is:\n', req.body.wktRepresenation);
// do something with req.body.wktRepresenation
// send back some json
res.json({myProperty:'myProperty value'}); // should show in response.json()
});
To summarize, you need to:
- post JSON request with
fetch - setup JSON parser on the server to process posted JSON
- use
req.bodyto access posted data - use
res.jsonto send back some JSON data
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