Preparation: Import the maven jar package
<dependency>
<groupId>org.webjars.npm</groupId>
<artifactId>axios</artifactId>
<version>1.5.1</version>
</dependency>
Step 1: Write the front-end page
<!doctype html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport"
content="width=device-width, user-scalable=no, initial-scale=1.0, maximum-scale=1.0, minimum-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>Download Center</title>
<style>
.txt {
color: green;
}
</style>
</head>
<body>
<div id="app">
<h1>Download Center</h1>
<ol>
<li><span class="txt">WeChat Mini Program Project</span> <a href="javascript:void(0)" onclick="sendDownloadAsync('WeChat Mini Program Project.zip','d5cbcd2a-7e08-11ee-bf9c -54e1ad104b87')">Download</a></li>
<li><span class="txt">Java Engineer Resume Template</span> <a href="javascript:;" onclick="sendDownloadAsync('Java Engineer Resume Template.docx','cbae974f-7e08-11ee-bf9c-54e1ad104b87' )">Download</a></li>
</ol>
</div>
<script src="/webjars/axios/1.5.1/dist/axios.js"></script>
<script>
// Function: Download file
function fileDownload(res) {
//headers:"attachment;filename=WeChat Mini Program Project.zip"
//Indicates getting the file name from the response header
const fileName = decodeURI(res.headers['content-disposition']).replace(/\w + ;filename=(.*)/, '$1')
console.log("The parsed file name is ",fileName)
//const blob = new Blob([data], {type: headers['content-type']})
const blob = new Blob([res.data], { type: "application/octet-stream"});
const fileUrl = window.URL.createObjectURL(blob)
let link = document.createElement('a') //Create an a tag element
link.href = fileUrl //Set the href attribute of the a tag
link.download = decodeURI(fileName) //Set the downloaded file name
link.style.display = 'none' //Set to not display
document.body.appendChild(link) //Add the a tag element to the page
link.click() //Automatically trigger click event
document.body.removeChild(link);//Remove element after download is complete
window.URL.revokeObjectURL(fileUrl); // Release the blob object
}
// Function: Initiate an asynchronous file download request
function sendDownloadAsync(fileName,apiKey){
axios({
method: 'POST',
url: '/api/download/file',
data: {
fileName,
apiKey
},
headers: {
//"Authorization": localStorage.getItem("token")
"Content-Type": "application/x-www-form-urlencoded"
},
responseType: 'blob'
}).then(res => {
const data = res.data;
const fileReader = new FileReader();
// Carry out object replacement to avoid downloading the error message returned by the back-end interface as a file.
fileReader.onload = (event) => {
try {
const data = JSON.parse(event.target.result);
if (data.code !== 0) {
// Failed to parse into an object, indicating that it is ordinary object data
console.log(`Download prompt: ${data.msg}`);
alert(`Download prompt: ${data.msg}`)
}
} catch (err) {
// Failed to parse into an object, indicating that it is a normal file stream and can be downloaded
//Download file normally
fileDownload(res)
}
};
fileReader.readAsText(data);
})
}
</script>
</body>
</html>
Step 2: Write the download controller
@RestController
@RequestMapping("/api/download")
public class DownloadController {
@Autowired
private UploadProperties uploadProperties;
// Redis
private static final List<String> APIKEY_LIST = new ArrayList<>(
Arrays.asList(
"d5cbcd2a-7e08-11ee-bf9c-54e1ad104b87",
"cbae974f-7e08-11ee-bf9c-54e1ad104b87"
)
);
/**
* download file
*
* @param fileName Download file name
* @param apiKey apiKey
*/
@PostMapping("/file")
public void downloadFile(@RequestParam("fileName") String fileName,
@RequestParam("apiKey") String apiKey,
HttpServletResponse response) throws UnsupportedEncodingException, FileNotFoundException, BizException {
final String savePath = uploadProperties.getSavePath();
if (StringUtils.isBlank(fileName)) {
throw new BizException(400, "The downloaded file cannot be empty!");
}
if (StringUtils.isBlank(apiKey)) {
throw new BizException(400, "apiKey cannot be empty!");
}
if (!APIKEY_LIST.contains(apiKey)) {
throw new BizException(400, "apiKey is invalid, file downloading is prohibited!");
}
File downloadFile = new File(savePath, fileName);
if (!downloadFile.exists()) {
throw new BizException(400, "The file to be downloaded was not found!");
}
File path = new File(ResourceUtils.getURL("classpath:").getPath());
System.out.println("path?>?>>>>>>>>>>>>>>>>>>>>>>>>" + path);
response.setHeader("Content-Disposition", "attachment;filename=" + URLEncoder.encode(fileName, StandardCharsets.UTF_8.name()));
response.setContentType("application/octet-stream");
response.addHeader("Content-Length", downloadFile.length() + "");
// Disable browser caching
/*
Cache-Control: no-cache, no-store, must-revalidate
Pragma: no-cache
Expires: 0
Among them, Cache-Control is used for HTTP1.1 (including 1.1) and above; Pragma is used for HTTP1.0; Expires is used for proxy server caching.
*/
response.addHeader("Cache-Control", "no-cache, no-store, must-revalidate");
response.addHeader("Pragma", "no-cache");
response.addHeader("Expires", "0");
byte[] buffer = new byte[8 * 1024]; // 8kb
int readBytes = 0;
try (
BufferedInputStream bis = new BufferedInputStream(new FileInputStream(downloadFile));
BufferedOutputStream bos = new BufferedOutputStream(response.getOutputStream());
) {
while ((readBytes = bis.read(buffer)) != -1) {
bos.write(buffer, 0, readBytes);
bos.flush();
}
response.flushBuffer();
APIKEY_LIST.remove(apiKey);
} catch (Exception ex) {
throw new BizException(500, "File download failed");
}
}
}
Step 3: Unify JSON results
@ApiModel("Unified response result")
public class CommonResult<T> {
@ApiModelProperty("Response status code")
private int code;
@ApiModelProperty("Response prompt information")
private String msg;
@ApiModelProperty("Response data")
private T data;
public CommonResult(int code, String msg) {
this.code = code;
this.msg = msg;
}
public CommonResult(ResultCode resultCode) {
this.code = resultCode.getCode();
this.msg = resultCode.getMsg();
}
public CommonResult(int code, String msg, T data) {
this.code = code;
this.msg = msg;
this.data = data;
}
public static <T> CommonResult<T> success(T data) {
return new CommonResult<T>(ResultCode.SUCCESS.getCode(), ResultCode.SUCCESS.getMsg(), data);
}
public static <T> CommonResult<T> success(String msg) {
return new CommonResult<T>(0,msg);
}
public static <T> CommonResult<T> fail(ResultCode resultCode) {
return new CommonResult<T>(resultCode.getCode(), resultCode.getMsg());
}
public static <T> CommonResult<T> fail(int code, String msg) {
return new CommonResult<T>(code,msg);
}
public static <T> CommonResult<T> error() {
return new CommonResult<T>(ResultCode.SYSTEM_ERROR);
}
public static <T> CommonResult<T> error(int code,String msg) {
return new CommonResult<T>(code,msg);
}
public int getCode() {
return code;
}
public void setCode(int code) {
this.code = code;
}
public String getMsg() {
return msg;
}
public void setMsg(String msg) {
this.msg = msg;
}
public T getData() {
return data;
}
public void setData(T data) {
this.data = data;
}
}
Step 3: Unify JSON results: write enumeration class to return code and msg
public enum ResultCode {
SUCCESS(0, "Operation successful"),
FAILURE(1,"Operation failed"),
PARAM_VALID_ERROR(400, "Parameter verification error"),
UNAUTHORIZED(401, "Uncertified"),
FORBIDDEN(403, "No permission"),
SYSTEM_ERROR(500, "The system is busy, please try again later!")
;
private int code;
private String msg;
ResultCode(int code, String msg) {
this.code = code;
this.msg = msg;
}
public int getCode() {
return code;
}
public String getMsg() {
return msg;
}
}
Step 4: Global exception handler
public class BizException extends Exception{
private int code;
private String message;
public BizException(ResultCode resultCode) {
super(resultCode.getMsg());
this.code = resultCode.getCode();
this.message = resultCode.getMsg();
}
public BizException(int code,String message) {
super(message);
this.code = code;
this.message = message;
}
public BizException(int code,String message, Throwable cause) {
super(message, cause);
this.code = code;
this.message = message;
}
public int getCode() {
return code;
}
@Override
public String getMessage() {
return message;
}
}
/**
* Global exception handler
*/
@RestControllerAdvice
//@ControllerAdvice
//@ResponseBody
@Slf4j
public class GlobalExceptionHandler {
/**
* Handle missing request parameter exception
* @param ex HttpMessageNotReadableException
* @return
*/
@ExceptionHandler(MissingServletRequestParameterException.class)
@ResponseStatus(value = HttpStatus.BAD_REQUEST)
public CommonResult handleMissingException(
MissingServletRequestParameterException ex) {
log.error("Missing request parameters, {}", ex.getMessage());
return new CommonResult(400, "Missing necessary request parameters");
}
/**
* Handle missing request parameter exception
* @param ex HttpMessageNotReadableException
* @return
*/
@ExceptionHandler(MaxUploadSizeExceededException.class)
@ResponseStatus(value = HttpStatus.BAD_REQUEST)
public CommonResult handleUploadSizeException(
MaxUploadSizeExceededException ex) {
log.error("The maximum allowed file upload size exceeds {} bytes.,", ex.getMaxUploadSize());
return new CommonResult(400, "The uploaded file size exceeds" + ex.getMaxUploadSize() + "B");
}
/**
* Handle request parameter verification exceptions
*/
@ExceptionHandler(value = MethodArgumentNotValidException.class)
public CommonResult handleBindException(MethodArgumentNotValidException ex){
log.error("There is a problem with request parameter verification: {}, exception type: {}", ex.getMessage(), ex.getClass()); // for debug
String message = ex.getBindingResult().getFieldError().getDefaultMessage();
return CommonResult.error(400,message);
}
/**
* Handle customized business exceptions
*/
@ExceptionHandler(value = BizException.class)
public CommonResult handleBizException(BizException ex){
log.error("Business operation problem: {}, exception type: {}", ex.getMessage(), ex.getClass()); // for debug
return CommonResult.error(ex.getCode(),ex.getMessage());
}
/**
* Handle system exceptions
*/
@ExceptionHandler(value = Exception.class)
public CommonResult handleException(Exception ex){
log.error("System problem: {}, exception type: {}", ex.getMessage(), ex.getClass()); // for debug
return CommonResult.error();
}
}
The knowledge points of the article match the official knowledge files, and you can further learn relevant knowledge. Cloud native entry-level skills treeHomepageOverview 16993 people are learning the system