使用 java 進行文件拷貝 相信很多人都會用,,不過效率上是否最好呢?
最近看了看NIO決定試一試 java NIO 到底有什麼性能的提升.
第一種方法:古老的方式
long time=new Date().getTime();
int length=2097152;
FileInputStream in=new FileInputStream(f1);
FileOutputStream out=new FileOutputStream(f2);
byte[] buffer=new byte[length];
while(true){
int ins=in.read(buffer);
if(ins==-1){
in.close();
out.flush();
out.close();
return new Date().getTime()-time;
}else
out.write(buffer,0,ins);
}
}
方法的2參數分別是原始文件,和拷貝的目的文件.這裏不做過多介紹.
實現方法很簡單,分別對2個文件構建輸入輸出流,並且使用一個字節數組作爲我們內存的緩存器, 然後使用流從f1 中讀出數據到緩存裏,在將緩存數據寫到f2裏面去.這裏的緩存是2MB的字節數組
第2種方法:使用NIO中的管道到管道傳輸
long time=new Date().getTime();
int length=2097152;
FileInputStream in=new FileInputStream(f1);
FileOutputStream out=new FileOutputStream(f2);
FileChannel inC=in.getChannel();
FileChannel outC=out.getChannel();
int i=0;
while(true){
if(inC.position()==inC.size()){
inC.close();
outC.close();
return new Date().getTime()-time;
}
if((inC.size()-inC.position())<20971520)
length=(int)(inC.size()-inC.position());
else
length=20971520;
inC.transferTo(inC.position(),length,outC);
inC.position(inC.position()+length);
i++;
}
}
實現方法:在第一種實現方法基礎上對輸入輸出流獲得其管道,然後分批次的從f1的管道中像f2的管道中輸入數據每次輸入的數據最大爲2MB
方法3:內存文件景象寫(讀文件沒有使用文件景象,有興趣的可以回去試試,,我就不試了,估計會更快)
long time=new Date().getTime();
int length=2097152;
FileInputStream in=new FileInputStream(f1);
RandomAccessFile out=new RandomAccessFile(f2,"rw");
FileChannel inC=in.getChannel();
MappedByteBuffer outC=null;
MappedByteBuffer inbuffer=null;
byte[] b=new byte[length];
while(true){
if(inC.position()==inC.size()){
inC.close();
outC.force();
out.close();
return new Date().getTime()-time;
}
if((inC.size()-inC.position())<length){
length=(int)(inC.size()-inC.position());
}else{
length=20971520;
}
b=new byte[length];
inbuffer=inC.map(MapMode.READ_ONLY,inC.position(),length);
inbuffer.load();
inbuffer.get(b);
outC=out.getChannel().map(MapMode.READ_WRITE,inC.position(),length);
inC.position(b.length+inC.position());
outC.put(b);
outC.force();
}
}
實現方法:跟傷2個例子不一樣,這裏寫文件流沒有使用管道而是使用內存文件映射(假設文件f2在內存中).在循環中從f1的管道中讀取數據到字節數組裏,然後在像內存映射的f2文件中寫數據.
第4種方法:管道對管道
long time=new Date().getTime();
int length=2097152;
FileInputStream in=new FileInputStream(f1);
FileOutputStream out=new FileOutputStream(f2);
FileChannel inC=in.getChannel();
FileChannel outC=out.getChannel();
ByteBuffer b=null;
while(true){
if(inC.position()==inC.size()){
inC.close();
outC.close();
return new Date().getTime()-time;
}
if((inC.size()-inC.position())<length){
length=(int)(inC.size()-inC.position());
}else
length=2097152;
b=ByteBuffer.allocateDirect(length);
inC.read(b);
b.flip();
outC.write(b);
outC.force(false);
}
}
這裏實現方式與第3種實現方式很類似,不過沒有使用內存影射.
下面是對49.3MB的文件進行拷貝的測試時間(毫秒)
Start Copy File... file size:50290KB
CopyFile:b1.rmvb mode:forChannel RunTime:3203
CopyFile:b1.rmvb mode:forImage RunTime:3328
CopyFile:b1.rmvb mode:forJava RunTime:2172
CopyFile:b1.rmvb mode:forTransfer RunTime:1406
End Copy File!
PS:這個一個上傳方法 用的uploadify插件
public ReturnObject uploadFile(String deleteFileName,
HttpServletRequest request,HttpServletResponse response)
throws IOException{
System.out.println("附件上傳sessionInfo:"
+ ContextUtils.getSession().getId());
String basePath = Global.BASE_UPLOAD_FOLDER; // 獲取基礎路徑
String TemporaryFile=Global.BASE_UPLOAD_TEMPORARYFILE;//獲取臨時文件夾
MultipartHttpServletRequest multipartRequest = (MultipartHttpServletRequest)request;
Map<String,MultipartFile> fileMap = multipartRequest.getFileMap();
SimpleDateFormat sdf = new SimpleDateFormat("yyyyMMddhhmmss");
SimpleDateFormat sp = new SimpleDateFormat("yyyyMMdd");
// TODO multi-tenant.id 目前租戶ID都是707 待以後完善後multi-tenant.id 就是租戶ID
String ctxPath = basePath + File.separator + 707 + File.separator
+ ContextUtils.getCurrentSecurityUser().getUsername()
+ File.separator+TemporaryFile+File.separator;// 完整路徑
String ctxPathView = sp.format(new Date()) + "/";// 用於在數據庫存儲的路徑-從文件夾開始
String ymd = sdf.format(new Date());
// 如果不存在,創建文件夾
File file = new File(ctxPath);
if (!file.exists()){
file.mkdirs();
}
ReturnObject ro = new ReturnObject();
String fileNames = "";
for (Map.Entry<String,MultipartFile> entity : fileMap.entrySet()){
MultipartFile mf = entity.getValue();
String fileFullname = mf.getOriginalFilename();
// String fileName = mf.getOriginalFilename();
String fileName = ymd + "_" + fileFullname;
File uploadFile = new File(ctxPath + fileName);
try{
FileCopyUtils.copy(mf.getBytes(),uploadFile); //可以利用此方法進行文件移動,通過流直接移動
// copy成功之後保存上傳數據記錄
UploadFile uploadBean = new UploadFile();
uploadBean.setUpdUser(ContextUtils.getCurrentSecurityUser()
.getUsername());
uploadBean.setOriginName(fileFullname);
uploadBean.setFileName(fileName);
uploadBean.setUpdTime(new Date());
uploadBean.setIsFunction("other");
if (uploadBean != null){
uploadFileService.save(uploadBean);
}
fileNames += fileName + ",";
}
catch (IOException e){
e.printStackTrace();
ro.setSuccess(false);
ro.setMsg(e.getMessage());
return ro;
}
}
if (fileNames.endsWith(",")){
fileNames = fileNames.substring(0,fileNames.length() - 1);
}
ro.setSuccess(true);
ro.setMsg("上傳文件成功");
HashMap<String,Object> hsfiled = new HashMap<String,Object>();
hsfiled.put("fileNames",fileNames);
hsfiled.put("filepatch",ctxPathView);// 數據庫保存路徑(從時間開始截取的)
ro.setObj(hsfiled);
// 清空不需要的歷史文件
try{
log.info("刪除不需要的文件:" + deleteFileName);
String ctPath = basePath + File.separator + File.separator
+ deleteFileName;
// 如果不存在,創建文件夾
if (deleteFileName != null){
File fileTobeDelete = new File(ctPath);
if (fileTobeDelete.exists()){
fileTobeDelete.delete();
}
}
}
catch (Exception e){
log.error("刪除歷史文件出錯:" + e.getMessage());
}
return ro;
}