java nio 追加写文件_Java NIO在文件末尾追加数据
[java]代碼庫import java.io.File;
import java.io.IOException;
import java.io.RandomAccessFile;
import java.nio.MappedByteBuffer;
import java.nio.channels.FileChannel;
public class MappedFile {
// 文件名
private String fileName;
// 文件所在目錄路徑
private String fileDirPath;
// 文件對象
private File file;
private MappedByteBuffer mappedByteBuffer;
private FileChannel fileChannel;
private boolean boundSuccess = false;
// 文件最大只能為50MB
private final static long MAX_FILE_SIZE = 1024 * 1024 * 50;
// 最大的臟數(shù)據(jù)量512KB,系統(tǒng)必須觸發(fā)一次強制刷
private long MAX_FLUSH_DATA_SIZE = 1024 * 512;
// 最大的刷間隔,系統(tǒng)必須觸發(fā)一次強制刷
private long MAX_FLUSH_TIME_GAP = 1000;
// 文件寫入位置
private long writePosition = 0;
// 最后一次刷數(shù)據(jù)的時候
private long lastFlushTime;
// 上一次刷的文件位置
private long lastFlushFilePosition = 0;
public MappedFile(String fileName, String fileDirPath) {
super();
this.fileName = fileName;
this.fileDirPath = fileDirPath;
this.file = new File(fileDirPath + "/" + fileName);
if (!file.exists()) {
try {
file.createNewFile();
} catch (IOException e) {
e.printStackTrace();
}
}
}
/**
*
* 內(nèi)存映照文件綁定
* @return
*/
public synchronized boolean boundChannelToByteBuffer() {
try {
RandomAccessFile raf = new RandomAccessFile(file, "rw");
this.fileChannel = raf.getChannel();
} catch (Exception e) {
e.printStackTrace();
this.boundSuccess = false;
return false;
}
try {
this.mappedByteBuffer = this.fileChannel
.map(FileChannel.MapMode.READ_WRITE, 0, MAX_FILE_SIZE);
} catch (IOException e) {
e.printStackTrace();
this.boundSuccess = false;
return false;
}
this.boundSuccess = true;
return true;
}
/**
* 寫數(shù)據(jù)：先將之前的文件刪除然后重新
* @param data
* @return
*/
public synchronized boolean writeData(byte[] data) {
return false;
}
/**
* 在文件末尾追加數(shù)據(jù)
* @param data
* @return
* @throws Exception
*/
public synchronized boolean appendData(byte[] data) throws Exception {
if (!boundSuccess) {
boundChannelToByteBuffer();
}
writePosition = writePosition + data.length;
if (writePosition >= MAX_FILE_SIZE) { // 如果寫入data會超出文件大小限制，不寫入
flush();
writePosition = writePosition - data.length;
System.out.println("File="
+ file.toURI().toString()
+ " is written full.");
System.out.println("already write data length:"
+ writePosition
+ ", max file size=" + MAX_FILE_SIZE);
return false;
}
this.mappedByteBuffer.put(data);
// 檢查是否需要把內(nèi)存緩沖刷到磁盤
if ( (writePosition - lastFlushFilePosition > this.MAX_FLUSH_DATA_SIZE)
||
(System.currentTimeMillis() - lastFlushTime > this.MAX_FLUSH_TIME_GAP
&& writePosition > lastFlushFilePosition) ) {
flush(); // 刷到磁盤
}
return true;
}
public synchronized void flush() {
this.mappedByteBuffer.force();
this.lastFlushTime = System.currentTimeMillis();
this.lastFlushFilePosition = writePosition;
}
public long getLastFlushTime() {
return lastFlushTime;
}
public String getFileName() {
return fileName;
}
public String getFileDirPath() {
return fileDirPath;
}
public boolean isBundSuccess() {
return boundSuccess;
}
public File getFile() {
return file;
}
public static long getMaxFileSize() {
return MAX_FILE_SIZE;
}
public long getWritePosition() {
return writePosition;
}
public long getLastFlushFilePosition() {
return lastFlushFilePosition;
}
public long getMAX_FLUSH_DATA_SIZE() {
return MAX_FLUSH_DATA_SIZE;
}
public long getMAX_FLUSH_TIME_GAP() {
return MAX_FLUSH_TIME_GAP;
}
}//源代碼片段來自云代碼http://yuncode.net
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