負(fù)載服務(wù)器Z，應(yīng)用服務(wù)器A 和B ，從A上傳的附件，如何在B上下載下來(lái)？

這個(gè)問題我的解決思路如下（后來(lái)被一個(gè)裝逼的面試官給批評(píng)了這種做法，不過(guò)我瞧不起他）

服務(wù)器A、B 上傳附件的時(shí)候，將這個(gè)附件備份到服務(wù)器Z ，當(dāng)A、B下載文件的時(shí)候，首先會(huì)在自己服務(wù)器的目錄下尋找，如果找不到，就會(huì)從服務(wù)器Z 上下載一份到當(dāng)前服務(wù)器。

服務(wù)器之間的文件備份通過(guò)sftp，參考：https://www.jb51.net/article/196008.htm（下文中的SftpCustom 類就是這個(gè)鏈接里的 “SFTP上傳下載文件例子” 中的類）

這里主要介紹一下重寫上傳、下載的方法時(shí)應(yīng)該添加的代碼

上傳文件，異步操作

new Thread(() -> {SftpCustom fu = new SftpCustom();fu.upload(file.getAbsolutePath(), getFileName(fileDescr));fu.closeChannel();}).start();

下載文件，先從當(dāng)前服務(wù)器尋找

String tmpPath = roots[0].getPath() + ’/’ + getFileName(fileDescr);File file2 = new File(tmpPath);if (file2.exists()) {return FileUtils.openInputStream(file2);}SftpCustom fu = new SftpCustom();fu.download(getFileName(fileDescr), tmpPath);file2 = new File(tmpPath);inputStream = FileUtils.openInputStream(file2);fu.closeChannel();return inputStream;

cuba 框架中重寫上傳文件類FileStorage.java 的代碼如下：

package com.haulmont.cuba.core.app.custom;import com.google.common.util.concurrent.ThreadFactoryBuilder;import com.haulmont.cuba.core.app.FileStorageAPI;import com.haulmont.cuba.core.app.ServerConfig;import com.haulmont.cuba.core.entity.FileDescriptor;import com.haulmont.cuba.core.global.*;import com.haulmont.cuba.core.sys.AppContext;import com.haulmont.cuba.core.sys.SecurityContext;import org.apache.commons.io.FileUtils;import org.apache.commons.io.IOUtils;import org.apache.commons.lang.StringUtils;import org.slf4j.Logger;import org.slf4j.LoggerFactory;import javax.annotation.PostConstruct;import javax.annotation.PreDestroy;import javax.inject.Inject;import java.io.*;import java.nio.charset.StandardCharsets;import java.text.SimpleDateFormat;import java.util.ArrayList;import java.util.Calendar;import java.util.List;import java.util.concurrent.ExecutorService;import java.util.concurrent.Executors;import static com.haulmont.bali.util.Preconditions.checkNotNullArgument;public class FileStorage implements FileStorageAPI { private final Logger log = LoggerFactory.getLogger(FileStorage.class); @Inject protected UserSessionSource userSessionSource; @Inject protected TimeSource timeSource; @Inject protected Configuration configuration; protected boolean isImmutableFileStorage; protected ExecutorService writeExecutor = Executors.newFixedThreadPool(5, new ThreadFactoryBuilder().setNameFormat('FileStorageWriter-%d').build()); protected volatile File[] storageRoots; @PostConstruct public void init() { this.isImmutableFileStorage = configuration.getConfig(ServerConfig.class).getImmutableFileStorage(); } /** * INTERNAL. Don’t use in application code. */ public File[] getStorageRoots() { if (storageRoots == null) { String conf = configuration.getConfig(ServerConfig.class).getFileStorageDir(); if (StringUtils.isBlank(conf)) {String dataDir = configuration.getConfig(GlobalConfig.class).getDataDir();File dir = new File(dataDir, 'filestorage');dir.mkdirs();storageRoots = new File[]{dir}; } else {List<File> list = new ArrayList<>();for (String str : conf.split(',')) { str = str.trim(); if (!StringUtils.isEmpty(str)) { File file = new File(str); if (!list.contains(file)) list.add(file); }}storageRoots = list.toArray(new File[list.size()]); } } return storageRoots; } @Override public long saveStream(final FileDescriptor fileDescr, final InputStream inputStream) throws FileStorageException { checkFileDescriptor(fileDescr); File[] roots = getStorageRoots(); // Store to primary storage checkStorageDefined(roots, fileDescr); checkPrimaryStorageAccessible(roots, fileDescr); File dir = getStorageDir(roots[0], fileDescr); dir.mkdirs(); checkDirectoryExists(dir); final File file = new File(dir, getFileName(fileDescr)); checkFileExists(file); long size = 0; OutputStream os = null; try { os = FileUtils.openOutputStream(file); size = IOUtils.copyLarge(inputStream, os); os.flush(); writeLog(file, false); new Thread(() -> {SftpCustom fu = new SftpCustom();fu.upload(file.getAbsolutePath(), getFileName(fileDescr));fu.closeChannel(); }).start(); } catch (IOException e) { IOUtils.closeQuietly(os); FileUtils.deleteQuietly(file); throw new FileStorageException(FileStorageException.Type.IO_EXCEPTION, file.getAbsolutePath(), e); } finally { IOUtils.closeQuietly(os); } // Copy file to secondary storages asynchronously final SecurityContext securityContext = AppContext.getSecurityContext(); for (int i = 1; i < roots.length; i++) { if (!roots[i].exists()) {log.error('Error saving {} into {} : directory doesn’t exist', fileDescr, roots[i]);continue; } File copyDir = getStorageDir(roots[i], fileDescr); final File fileCopy = new File(copyDir, getFileName(fileDescr)); writeExecutor.submit(new Runnable() {@Overridepublic void run() { try { AppContext.setSecurityContext(securityContext); FileUtils.copyFile(file, fileCopy, true); writeLog(fileCopy, false); } catch (Exception e) { log.error('Error saving {} into {} : {}', fileDescr, fileCopy.getAbsolutePath(), e.getMessage()); } finally { AppContext.setSecurityContext(null); }} }); } return size; } protected void checkFileExists(File file) throws FileStorageException { if (file.exists() && isImmutableFileStorage) throw new FileStorageException(FileStorageException.Type.FILE_ALREADY_EXISTS, file.getAbsolutePath()); } protected void checkDirectoryExists(File dir) throws FileStorageException { if (!dir.exists()) throw new FileStorageException(FileStorageException.Type.STORAGE_INACCESSIBLE, dir.getAbsolutePath()); } protected void checkPrimaryStorageAccessible(File[] roots, FileDescriptor fileDescr) throws FileStorageException { if (!roots[0].exists()) { log.error('Inaccessible primary storage at {}', roots[0]); throw new FileStorageException(FileStorageException.Type.STORAGE_INACCESSIBLE, fileDescr.getId().toString()); } } protected void checkStorageDefined(File[] roots, FileDescriptor fileDescr) throws FileStorageException { if (roots.length == 0) { log.error('No storage directories defined'); throw new FileStorageException(FileStorageException.Type.STORAGE_INACCESSIBLE, fileDescr.getId().toString()); } } @Override public void saveFile(final FileDescriptor fileDescr, final byte[] data) throws FileStorageException { checkNotNullArgument(data, 'File content is null'); saveStream(fileDescr, new ByteArrayInputStream(data)); } protected synchronized void writeLog(File file, boolean remove) { SimpleDateFormat df = new SimpleDateFormat('yyyy-MM-dd HH:mm:ss.SSS'); StringBuilder sb = new StringBuilder(); sb.append(df.format(timeSource.currentTimestamp())).append(' '); sb.append('[').append(userSessionSource.getUserSession().getUser()).append('] '); sb.append(remove ? 'REMOVE' : 'CREATE').append(' '); sb.append(''').append(file.getAbsolutePath()).append(''n'); File rootDir; try { rootDir = file.getParentFile().getParentFile().getParentFile().getParentFile(); } catch (NullPointerException e) { log.error('Unable to write log: invalid file storage structure', e); return; } File logFile = new File(rootDir, 'storage.log'); try { try (FileOutputStream fos = new FileOutputStream(logFile, true)) {IOUtils.write(sb.toString(), fos, StandardCharsets.UTF_8.name()); } } catch (IOException e) { log.error('Unable to write log', e); } } @Override public void removeFile(FileDescriptor fileDescr) throws FileStorageException { checkFileDescriptor(fileDescr); File[] roots = getStorageRoots(); if (roots.length == 0) { log.error('No storage directories defined'); return; } for (File root : roots) { File dir = getStorageDir(root, fileDescr); File file = new File(dir, getFileName(fileDescr)); if (file.exists()) {if (!file.delete()) { throw new FileStorageException(FileStorageException.Type.IO_EXCEPTION, 'Unable to delete file ' + file.getAbsolutePath());} else { writeLog(file, true);} } } } protected void checkFileDescriptor(FileDescriptor fd) { if (fd == null || fd.getCreateDate() == null) { throw new IllegalArgumentException('A FileDescriptor instance with populated ’createDate’ attribute must be provided'); } } @Override public InputStream openStream(FileDescriptor fileDescr) throws FileStorageException { checkFileDescriptor(fileDescr); File[] roots = getStorageRoots(); if (roots.length == 0) { log.error('No storage directories available'); throw new FileStorageException(FileStorageException.Type.FILE_NOT_FOUND, fileDescr.getId().toString()); } InputStream inputStream = null; for (File root : roots) { File dir = getStorageDir(root, fileDescr); File file = new File(dir, getFileName(fileDescr)); if (!file.exists()) {log.error('File ' + file + ' not found');continue; } try {inputStream = FileUtils.openInputStream(file);break; } catch (IOException e) {log.error('Error opening input stream for ' + file, e); } } if (inputStream != null) { return inputStream; } else { try {String tmpPath = roots[0].getPath() + ’/’ + getFileName(fileDescr);File file2 = new File(tmpPath);if (file2.exists()) { return FileUtils.openInputStream(file2);}SftpCustom fu = new SftpCustom();fu.download(getFileName(fileDescr), tmpPath);file2 = new File(tmpPath);inputStream = FileUtils.openInputStream(file2);fu.closeChannel();return inputStream; } catch (Exception e) {throw new FileStorageException(FileStorageException.Type.FILE_NOT_FOUND, fileDescr.getId().toString()); } } } @Override public byte[] loadFile(FileDescriptor fileDescr) throws FileStorageException { InputStream inputStream = openStream(fileDescr); try { return IOUtils.toByteArray(inputStream); } catch (IOException e) { throw new FileStorageException(FileStorageException.Type.IO_EXCEPTION, fileDescr.getId().toString(), e); } finally { IOUtils.closeQuietly(inputStream); } } @Override public boolean fileExists(FileDescriptor fileDescr) { checkFileDescriptor(fileDescr); File[] roots = getStorageRoots(); for (File root : roots) { File dir = getStorageDir(root, fileDescr); File file = new File(dir, getFileName(fileDescr)); if (file.exists()) {return true; } } return false; } /** * INTERNAL. Don’t use in application code. */ public File getStorageDir(File rootDir, FileDescriptor fileDescriptor) { checkNotNullArgument(rootDir); checkNotNullArgument(fileDescriptor); Calendar cal = Calendar.getInstance(); cal.setTime(fileDescriptor.getCreateDate()); int year = cal.get(Calendar.YEAR); int month = cal.get(Calendar.MONTH) + 1; int day = cal.get(Calendar.DAY_OF_MONTH); return new File(rootDir, year + '/'+ StringUtils.leftPad(String.valueOf(month), 2, ’0’) + '/'+ StringUtils.leftPad(String.valueOf(day), 2, ’0’)); } public static String getFileName(FileDescriptor fileDescriptor) { return fileDescriptor.getId().toString() + '.' + fileDescriptor.getExtension(); } @PreDestroy protected void stopWriteExecutor() { writeExecutor.shutdown(); }}

以上就是本文的全部?jī)?nèi)容，希望對(duì)大家的學(xué)習(xí)有所幫助，也希望大家多多支持好吧啦網(wǎng)。