Java大文件被保存在數據庫中 - 對象設計

Question

我想弄清楚使用hibernate在數據庫中實現大文件（〜600 MB）存儲庫的對象設計。 請建議正確的方法/設計？

class ModelClass{ 

String name; //meta data 
... 

Option 1. 
    byte[] file; // dont want to load the content of the entire file 
          // in memory by using this but hibernate recognizes 
          // this datatype 
Option 2. 
    InputStream inputStream; 
    OutputStream outputStream; 
    // I can have the methods to provide the input or output stream 
       // but i dont think its a clean approach. I am not sure how 
       // I will be able to work with hibernate with streams 
Option 3. 
    File fileHandle; 
} 

任何其他選項??

我想調用hibernateTemplate的save（Object）方法將對象保存到數據庫中。不知道我是否應該只有班級中的元數據，並單獨處理文件保存和檢索。

在此先感謝。

另一個可行的解決方案是使用「工作」接口。目的是避免將文件內容加載到內存中。

session.doWork(new Work(){ 
    @Override 
    public void execute(Connection conn) { 
     //direct sql queries go here 
    } 

}); 

Answer 1

我已經寫了一個SerializableFile類來保存文件中的數據。讀取對象時，會創建一個臨時文件。 這就是：

public class SerializableFile implements Serializable { 
    private static final File TEMP_DIR = getTempDir(); 

    private transient boolean temporary; 
    private transient String name; 
    private transient File file; 

    public SerializableFile() { 
    } 

    public SerializableFile(File file) { 
     this.file = file; 
     this.name = file.getName(); 
     this.temporary = false; 
    } 

    @Override 
    protected void finalize() throws Throwable { 
     dispose(); 
     super.finalize(); 
    } 

    public void dispose() { 
     if (temporary && file != null) { 
      file.delete(); 
      file = null; 
     } 
    } 

    public File keep(String name) throws IOException { 
     if (temporary) { 
      temporary = false; 
     } else { 
      File newFile = new File(TEMP_DIR, name); 
      keepAs(newFile); 
      file = newFile; 
     } 
     return file; 
    } 

    public void keepAs(File outFile) throws IOException { 
     if ((temporary || file.equals(outFile)) && file.renameTo(outFile)) { 
      temporary = false; 
      file = outFile; 
     } else { 
      InputStream in = new FileInputStream(file); 
      try { 
       OutputStream out = new FileOutputStream(outFile); 
       try { 
        byte buf[] = new byte[4096]; 
        for (int n = in.read(buf); n > 0; n = in.read(buf)) { 
         out.write(buf, 0, n); 
        } 
       } finally { 
        out.close(); 
       } 
      } finally { 
       in.close(); 
      } 
      outFile.setLastModified(file.lastModified()); 
     } 
    } 

    public String getName() { 
     return name; 
    } 

    public File getFile() { 
     return file; 
    } 

    public long lastModified() { 
     return file.lastModified(); 
    } 

    private void writeObject(ObjectOutputStream out) throws IOException { 
     int size = (int)file.length(); 
     long date = file.lastModified(); 
     out.writeUTF(name); 
     out.writeInt(size); 
     out.writeLong(date); 
     InputStream in = new FileInputStream(file); 
     try { 
      byte buf[] = new byte[4096]; 
      while (size > 0) { 
       int n = in.read(buf); 
       if (n <= 0 || n > size) { 
        throw new IOException("Unexpected file size"); 
       } 
       out.write(buf, 0, n); 
       size -= n; 
      } 
     } finally { 
      in.close(); 
     } 
    } 

    private void readObject(ObjectInputStream in) throws IOException { 
     name = in.readUTF(); 
     int size = in.readInt(); 
     long date = in.readLong(); 
     file = File.createTempFile("tmp", ".tmp", TEMP_DIR); 
     OutputStream out = new FileOutputStream(file); 
     try { 
      byte buf[] = new byte[4096]; 
      while (size > 0) { 
       int n = in.read(buf, 0, size <= buf.length ? size : buf.length); 
       if (n <= 0 || n > size) { 
        throw new IOException("Unexpected file size"); 
       } 
       out.write(buf, 0, n); 
       size -= n; 
      } 
     } finally { 
      out.close(); 
     } 
     file.setLastModified(date); 
     temporary = true; 
    } 

    private static File getTempDir() { 
     File dir; 
     String temp = System.getProperty("com.lagalerie.live.temp-dir"); 
     if (temp != null) { 
      dir = new File(temp); 
     } else { 
      String home = System.getProperty("user.home"); 
      dir = new File(home, "temp"); 
     } 
     if (!dir.isDirectory() && !dir.mkdirs()) { 
      throw new RuntimeException("Could not create temp dir " + dir); 
     } 
     return dir; 
    } 
} 

Answer 2

打開JPA支持與some databases一個@Persistent註釋：

• MySQL的
• 甲骨文
• PostgreSQL的
• SQL服務器
• DB2

Answer 3

即使你還在使用RDBMS作爲數據存儲，你應該考慮將這個二進制數據到一個文件系統，並保存路徑的目錄/位置到數據庫中，而不是將其作爲BLOB或CLOB存儲到數據庫中。