负载服务器Z，应用服务器A 和B ，从A上传的附件，如何在B上下载下来？

这个问题我的解决思路如下(后来被一个装逼的面试官给批评了这种做法，不过我瞧不起他)

服务器A、B 上传附件的时候，将这个附件备份到服务器Z ，当A、B下载文件的时候，首先会在自己服务器的目录下寻找，如果找不到，就会从服务器Z 上下载一份到当前服务器。

服务器之间的文件备份通过sftp，参考：https://www.jb51.net/article/196008.htm(下文中的SftpCustom 类就是这个链接里的 “SFTP上传下载文件例子” 中的类)

这里主要介绍一下重写上传、下载的方法时应该添加的代码

上传文件，异步操作

new Thread(() -> {

SftpCustom fu = new SftpCustom();

fu.upload(file.getAbsolutePath(), getFileName(fileDescr));

fu.closeChannel();

}).start();

下载文件，先从当前服务器寻找

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 框架中重写上传文件类FileStorage.java 的代码如下：

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 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() {

@Override

public 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内容，希望对大家的学习有所帮助，也希望大家多多支持脚本之家。