react can't get restController response - spring

Question

I have tried to use restController generate file byte array but when i return it to react , react didn't get the byte array. front-end is using react , back-end is using spring restController and i use Http to communication both front and back. is it any wrong in my code? Thank you for your helping.
restController:
String fileName = DateUtility.dateToStr(new Date(), DateUtility.YYYYMMDD_HHMMSS) + " - "
+ reportNmaeByType.get(exportParam.getReportType()) + ".xls";
HttpHeaders headers = new HttpHeaders();
headers.setContentDispositionFormData("attachment", fileName);
headers.setContentType(MediaType.APPLICATION_OCTET_STREAM);
return new ResponseEntity<>(excelByte, HttpStatus.OK);
react:
createExcelFile(){
var params = {
reportResultList: this.state.reportResult,
reportType: getReportSelector().state.selectedReportType,
selectColumnMap: this.state.selectColumn,
selectCusColumnMap: this.state.selectCusColumn
}
fetch("http://localhost:8080/mark-web/file/createExcel", {
method: 'POST',
headers: {
'Content-Type': 'application/json',
},
body: JSON.stringify(params)
}).then(res => {
if (res.ok) {
console.log(res)
console.log(this)
console.log('create excel success!!')
} else {
console.log('create excel Fail!!')
}
})
}
response:
enter image description here
Update 2018/09/16:
I have added some code in react function and it finally could download excel file but the file is broken. i have checked the blob object in response. it shows blob is json object. is it because i didn't decode to the blob object?
React:
}).then(res => {
if(!res.ok){
console.log("Failed To Download File")
}else{
return res.blob()
}
}).then(blob => {
console.log(blob)
let url = URL.createObjectURL(blob)
console.log(url)
var downloadAnchorNode = document.createElement('a')
downloadAnchorNode.setAttribute("href", url)
downloadAnchorNode.setAttribute("download", "excel" + ".xls")
downloadAnchorNode.click()
downloadAnchorNode.remove()
})
response:
enter image description here

Answer 1

So, from your network graph, it looks like your request is completing as expected, but you are just unable to derive the ByteArray from the response.
With normal requests which return a JSON or XML for e.x. you can read them in one go, as they are part of the body. In your case however, your body contains a Stream. You will thus have to handle reading that stream on your own.
You can do that with response.blob() :
The blob() method reads the stream to completion and returns a Blob object. You can then use this blob object to embed an image or download the file. For all intent and purposes, I would recommend using this. Unless you are dealing with huge files (>500 MB), it should suffice your needs.
For example:
fetch("http://localhost:8080/mark-web/file/createExcel", {
method: 'POST',
headers: {
'Content-Type': 'application/json',
},
body: JSON.stringify(params)
}).then(res => {
if (!res.ok) {
throw new Error(res.statusText);
} else {
return res.blob()
}
}).then(blob => {// do your thing})
.catch(err => console.log(error))
Or
You can use the experimental ReadableStream interface for a more granular control over what you want to do with it.