1. Application scenarios
Document management module, list of records displayed daily file upload saved records. Each data field stores the storage address of the file on the file server
Now you need to batch download the list data, download multiple files together and put them together as a zip package to download to the browser
2. Development ideas
Because some need to be classified according to a save and download, because there may be multiple folders, all can’t go directly after each file of flow form to package it, so here with the method of first download, will network file according to the given rules to create folders on the local temporary directory, and then to read and write files into a compressed stream to download.
According to their actual business, due to the need to batch download the file together more than 300 MB, so the use of two split service, first request download interface, use multithreading download to the server temporary directory, and then intervals a period of time to request download services
2.1 Download Files in batches to temporary Directories
The controller layer
@GetMapping("step/imgs/download/{id}")
@apiOperation (value = "Download the image of the specified inspection task to the local directory ")
public ResponseEntity uploadToLocal(@PathVariable("id") Integer id) {
// This step gets the download information set based on the individual's business
Map<String, List<PatrolTaskPointStepImgVO>> imgMap = exportService.getImgMap(id);
exportService.imgTolocal(imgMap);
return ResponseEntity.ok(Please visit /step/imgs/download in 5 minutes. Id =, download file");
}
Copy the codeimgMapData structure description:
- Key: indicates the folder name
- Value: stores the file data table
Fields are as follows
@APIModelProperty (value = "ID ") private Integer ID; @APIModelProperty (value = "Inspection Task Step table ID ") private Integer taskPointStepId; @APIModelProperty (value = "imgUrl ") private String imgUrl; @APIModelProperty (value = "thumbnail URL ") private String imgThumbnailUrl; @APIModelProperty (value = "type 0: image, 1: video ") private Integer type; private String pointName; private String stepName;Copy the codeservicelayer
void imgTolocal(Map<String, List<PatrolTaskPointStepImgVO>> res);
Copy the codeserviceThe implementation class
@Override
public void imgTolocal(Map<String, List<PatrolTaskPointStepImgVO>> res) {
index = 0;
if(res == null || res.isEmpty()){
throw new BadRequestAlertException("has_not_imgList" ,this.getClass().getSimpleName(),"has_not_imgList");
}
// Obtain the system temporary storage address
Path path = Paths.get(System.getProperty("java.io.tmpdir"),this.TaskName);
File file = new File(String.valueOf(path));
if(! file.exists()){ file.mkdirs(); }try {
log.info("Start downloading file :{}", sdf.format(new Date()));
res.forEach((k,v) -> {
new Thread (() -> {
index++;
log.info("Start executing download thread {}", index);
File fl = new File(String.valueOf(path) + File.separator + k);
if(! fl.exists()) { fl.mkdirs(); }if(! CollectionUtils.isEmpty(v)) { v.stream().forEach(e -> {try {
log.info("Start downloading image resource ID {}", e.getImgUrl());
download(e.getImgUrl(), e.getStepName() + e.getId(), fl.getPath());
} catch(Exception e1) { e1.printStackTrace(); }}); } }).start(); }); }catch (Exception e) {
e.printStackTrace();
} finally {
log.info("All files downloaded completed" ,sdf.format(newDate())); }}private void download(String urlString, String filename,String savePath) throws Exception {
URL url = new URL(urlString);
URLConnection con = url.openConnection();
// Set the request timeout to 5s
con.setConnectTimeout(5*1000);
/ / input stream
InputStream is = con.getInputStream();
// 1K data buffer
byte[] bs = new byte[1024];
// The length of the data read
int len;
// Output file stream
File sf=new File(savePath);
if(! sf.exists()){ sf.mkdirs(); } String extensionName = urlString.substring(urlString.lastIndexOf("."));
String newFileName = filename + extensionName;
OutputStream os = new FileOutputStream(sf.getPath()+ File.separator +newFileName);
// Start reading
while((len = is.read(bs)) ! = -1) {
os.write(bs, 0, len);
}
os.close();
is.close();
}
Copy the code2.2 Converting Files from the System Temporary Directory and downloading them from the Browser (Temporary files are automatically deleted when you create a scheduled task)
controller层
@GetMapping("/step/imgs/download")
@ApiOperation(value = "Download the specified inspection resources into a compressed package in the browser ")
public void uploadStepImg (
@APIParam (value = "Inspection task ID", Required = true) @RequestParam(value = "id") Integer id,
HttpServletResponse response
){
Map<String, List<PatrolTaskPointStepImgVO>> imgMap = exportService.getImgMap(id);
exportService.imgToZip(imgMap ,response);
}
Copy the codeservice层
void imgToZip(Map<String, List<PatrolTaskPointStepImgVO>> res , HttpServletResponse response);
Copy the code3. Service realization
@Override
public void imgToZip(Map<String, List<PatrolTaskPointStepImgVO>> res , HttpServletResponse response) {
// Obtain the system temporary storage address
if(res == null || res.isEmpty()){
throw new BadRequestAlertException("has_not_imgList" ,this.getClass().getSimpleName(),"has_not_imgList");
}
Path path = Paths.get(System.getProperty("java.io.tmpdir"),this.TaskName);
File file = new File(String.valueOf(path));
if(! file.exists()){throw new BadRequestAlertException("No relevant documents found.".this.getClass().getSimpleName(),"No relevant documents found.");
}
chenkFile(file ,String.valueOf(path));
zip(String.valueOf(path) ,response);
}
public void chenkFile(File file,String path){
try {
if (file.exists()){
// If the file does not exist
if (!file.isDirectory()){
file.createNewFile();
}
}else {
// If the directory does not exist
// Create the specified directory file object
File file1 = new File(path);
file1.mkdirs();// Create directory
file.createNewFile();// Create a file}}catch(IOException e) { log.error(e.getMessage(),e); }}public void zip(String sourceFileName, HttpServletResponse response){
ZipOutputStream out = null;
BufferedOutputStream bos = null;
log.info("Start compression :{}", sdf.format(new Date()));
File sourceFile = new File(sourceFileName);
try {
// Outputs the zip as a stream to the foreground
response.setHeader("content-type"."application/octet-stream");
response.setCharacterEncoding("utf-8");
// Set content-disposition for the browser response header
TestZip indicates the file name of the compressed package, and. Zip indicates the file suffix
response.setHeader("Content-disposition"."attachment; filename=" + new String(this.TaskName.getBytes("gbk"), "iso8859-1") +".zip");
// Create zip output stream
out = new ZipOutputStream(response.getOutputStream());
// Create a buffered output stream
bos = new BufferedOutputStream(out);
// Call compression
compress(out, bos, sourceFile, sourceFile.getName());
out.flush();
log.info("Compression done :{}" ,sdf.format(new Date()));
} catch (Exception e) {
log.error("Abnormal ZIP compression:"+e.getMessage(),e);
} finally {
try {
if(bos ! =null) {
bos.close();
}
if( out ! =null) { out.close(); }}catch (IOException e) {
e.printStackTrace();
}
Timer After the Timer task is completed, the thread is not actively closed but waits for gc collection
new Thread( () -> {
try {
Thread.sleep(1000*60*30);
deleteFile(sourceFile);
} catch(InterruptedException e) { e.printStackTrace(); }}); }}public static void compress(ZipOutputStream out, BufferedOutputStream bos, File sourceFile, String base){
FileInputStream fos = null;
BufferedInputStream bis = null;
try {
// If the path is a directory (folder)
if (sourceFile.isDirectory()) {
// Retrieve files from folders (or subfolders)
File[] flist = sourceFile.listFiles();
// If the folder is empty, just write a directory entry point in the destination ZIP file
if (flist.length == 0) {
out.putNextEntry(new ZipEntry(base + File.separator));
} else {
// If the folder is not empty, compress is recursively called and every file (or folder) in the folder is compressed
for (int i = 0; i < flist.length; i++) { compress(out, bos, flist[i], base + File.separator + flist[i].getName()); }}}else {
// If it is not a directory (folder), that is, a file, the directory entry point is written first, then the file is written to the zip file
out.putNextEntry(new ZipEntry(base));
fos = new FileInputStream(sourceFile);
bis = new BufferedInputStream(fos);
byte [] buffer = new byte[1024];
int tag;
// Write the source file to the zip file
while((tag = bis.read(buffer)) ! = -1) {
out.write(buffer, 0,tag); }}}catch (Exception e) {
e.printStackTrace();
} finally{}}private void deleteFile(File file) {
if (file.exists()) {
if (file.isFile()) {
file.delete();
log.info("Deleting file {}" ,file.getName());
} else if (file.isDirectory()) {
File[] files = file.listFiles();
for (int i = 0; i < files.length; i++) {
this.deleteFile(files[i]);
}
file.delete();
log.info("Deleting file {}",file.getName()); }}else {
System.out.println("Deleted file does not exist"); }}Copy the code