在一些web应用项目实施过程，会碰到这么一个问题，例如：项目中有功能需要上传图片、文件等附件，这些附件在存储时常规的情况下是存储在一个固定的目录下，在部署多个相同的Tomcat实例集群的时候，往往需要考虑这些附件的同步问题，因此采用 FastDFS来对附件进行存储管理。
FastDFS 是一个开源的分布式文件系统，她对文件进行管理，功能包括：文件存储、文件同步、文件访问（文件上传、文件下载）等，解决了大容量存储和负载均衡的问题。FastDFS的工作原理以及相关安装流程就不做过多赘述，可以搜索相关资料了解，下面就来给大家介绍一下Java如何实现通过FastDFS上传、下载、删除附件。
首先需要在项目中导入FastDFS依赖相关的Jar包，我们使用maven的情况下，如下配置：
<dependency>
<groupId>commons-io</groupId>
<artifactId>commons-io</artifactId>
<version>2.6</version>
</dependency>
<dependency>
<groupId>commons-fileupload</groupId>
<artifactId>commons-fileupload</artifactId>
<version>1.3.1</version>
</dependency>
<dependency>
<groupId></groupId>
<artifactId>fastdfs-client-java</artifactId>
<version>1.29-SNAPSHOT</version>
</dependency>
第二步，在springboot项目中创建配置文件fdfs_client.conf
#默认值为30s
connect_timeout = 10
#默认值为30s
network_timeout = 30
charset = UTF-8
http.tracker_http_port = 8080
# token 防盗链功能
http.anti_steal_token = true
#防盗链key
http.secret_key = ZFnWLBqrX3
#服务器
tracker_server = 127.0.0.1:22122第三步，创建一个实体类，定义附件相关的对象
public class FastDFSFile {
private String name;//文件名
private byte[] content; //文件的内容，字节数组
private String ext; //文件扩展名，不包含（.）
private String md5; //加密
public FastDFSFile() {
}
public FastDFSFile(String name, byte[] content, String ext) {
= name;
= content;
= ext;
}
public String getName() {
return name;
}
public void setName(String name) {
= name;
}
public byte[] getContent() {
return content;
}
public void setContent(byte[] content) {
= content;
}
public String getExt() {
return ext;
}
public void setExt(String ext) {
= ext;
}
public String getMd5() {
return md5;
}
public void setMd5(String md5) {
this.md5 = md5;
}
public String getAuthor() {
return author;
}
public void setAuthor(String author) {
= author;
}
}
第四步，创建工具类，写入相关方法
public class FastDFSClient {
private final static Logger logger = ();
//初始化
static {
try {
String filePath = new ClassPathResource("fdfs_client.conf").getFile().getAbsolutePath();
IniFileReader iniReader = new IniFileReader(filePath);
String[] szTrackerServers = ("tracker_server");
(filePath);
} catch (Exception e) {
throw new MyException(ResultEnum.FAST_DFS_ERROR);
}
}
//上传
public static String upload(FastDFSFile file){
NameValuePair[] meta_list = new NameValuePair[1];
meta_list[0] = new NameValuePair("author", ());
long startTime = ();
String[] uploadResults = null;
StorageClient storageClient=null;
try {
storageClient = getTrackerClient();
//upload_file()三个参数：@param fileContent ①：文件的内容，字节数组 ②：文件扩展名 ③文件扩展信息 数组
uploadResults = storageClient.upload_file((), (), meta_list);
}catch (Exception e){
();
throw new MyException(ResultEnum.FAST_DFS_ERROR);
}
if (uploadResults == null && storageClient!=null) {
("upload file fail, error code:" + ());
}
("upload_file time used:" + (() - startTime) + " ms");
String groupName = uploadResults[0];
String remoteFileName = uploadResults[1];
return groupName+"/"+remoteFileName;
}
//下载文件
public static boolean downloadFile(String localFilename, String groupName, String remoteFilename) {
//localFilename 本地文件名
//groupName 文件在FastDFS中的组名
//remoteFilename 文件在FastDFS中的名称
File file = new File(localFilename);
if(!()) {
if(!().exists()){
().mkdirs();
}
try {
();
} catch (IOException e) {
();
}
}else if(()>0){
("()="+());
return true;
}
TrackerServer trackerServer;
TrackerClient trackerClient=new TrackerClient();
StorageServer storageServer=null;
StorageClient storageClient=null;
try (BufferedOutputStream bos = new BufferedOutputStream(new FileOutputStream(file))) {
trackerServer = ();
storageServer=(trackerServer);
storageClient= new StorageClient(trackerServer, storageServer);
byte[] content = storageClient.download_file(groupName, remoteFilename);
if (content == null || == 0) {
boolean flag = ();
return false;
}
(content);
return true;
} catch (IOException | MyException e) {
();
return false;
}catch (Exception e){
();
return false;
}
}
//删除
public static int deleteFile(String groupName, String remoteFileName) throws Exception {
//remoteFileName--文件路径 例如：M00/00/00/
//groupName --文件路径，例如：group1/M00/00/00/中的group1
StorageClient storageClient = getTrackerClient();
return storageClient.delete_file(groupName, remoteFileName);
}
//查询文件信息
public static FileInfo getFile(String groupName, String remoteFileName) {
try {
StorageClient storageClient = getTrackerClient();
return storageClient.get_file_info(groupName, remoteFileName);
} catch (IOException e) {
("IO Exception: Get File from Fast DFS failed", e);
} catch (Exception e) {
("Non IO Exception: Get File from Fast DFS failed", e);
}
return null;
}
}
第五步，调用示例
public class UploadDFS {
//上传文件
public static String saveFile(MultipartFile multipartFile) throws IOException {
String fileName=();
String ext = ((".") + 1);
byte[] file_buff = null;
InputStream inputStream=();
if(inputStream!=null){
int len1 = ();
file_buff = new byte[len1];
(file_buff);
}
();
FastDFSFile file = new FastDFSFile(fileName, file_buff, ext);
return (file);
}
//下载
public static boolean downFile(String localFilename, String groupName, String remoteFilename){
//下载完成后到存储路径找下载的文件 localFilename
return (localFilename,groupName,remoteFilename);
}
//删除
public static void deleteFile(String groupName, String remoteFileName){
try {
int res= (groupName,remoteFileName);
} catch (Exception e) {
throw new RuntimeException(e);
}
}
}