从 Java 中 blob 的内容创建文件的代码段
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Snippet to create a file from the contents of a blob in Java
提问by OscarRyz
I have some files stored in a database blob column in Oracle 9.
我有一些文件存储在 Oracle 9 的数据库 blob 列中。
I would like to have those files stored in the file system.
我想将这些文件存储在文件系统中。
This should be pretty easy, but I don't find the right snipped.
这应该很容易，但我没有找到正确的剪断。
How can I do this in java?
我怎么能在java中做到这一点？
PreparedStatement ptmst = ...
ResutlSet rs = pstmt.executeQuery();
rs.getBlob();
// mistery
FileOutputStream out = new FileOutputStream();
out.write(); // etc et c
I know it should be something like that... what I don't know is what is commented as mistery
我知道它应该是这样的......我不知道被评论为神秘的东西
Thanks
谢谢
EDIT
编辑
I finally got this derived from David's question.
我终于从大卫的问题中得到了这个。
This is my lazy implementation:
这是我的懒惰实现：
PreparedStatement pstmt = connection.prepareStatement("select BINARY from MYTABLE");
ResultSet rs = pstmt.executeQuery();
while( rs.next() ) {
Blob blob = rs.getBlob("BINARY");
System.out.println("Read "+ blob.length() + " bytes ");
byte [] array = blob.getBytes( 1, ( int ) blob.length() );
File file = File.createTempFile("something-", ".binary", new File("."));
FileOutputStream out = new FileOutputStream( file );
out.write( array );
out.close();
}
采纳答案by David Winslow
You'd want to get the blob as an inputstream and dump its contents to the outputstream. So 'misery' should be something like:
您希望将 blob 作为输入流并将其内容转储到输出流。所以“痛苦”应该是这样的：
Blob blob = rs.getBlob(column);
InputStream in = blob.getBinaryStream();
OutputStream out = new FileOutputStream(someFile);
byte[] buff = new byte[4096]; // how much of the blob to read/write at a time
int len = 0;
while ((len = in.read(buff)) != -1) {
out.write(buff, 0, len);
}
If you find yourself doing a lot of IO work like this, you might look into using Apache Commons IOto take care of the details. Then everything after setting up the streams would just be:
如果您发现自己做了很多这样的 IO 工作，您可能会考虑使用Apache Commons IO来处理细节。然后设置流后的一切都将是：
IOUtils.copy(in, out);
回答by GiantSteps
There is another way of doing the same operation faster. Actually the answer above works fine but like IOUtils.copy(in,out)it takes a lot of time for big documents. The reason is you are trying to write your blob by 4KB iteration. Simplier solution :
还有另一种方法可以更快地执行相同的操作。实际上，上面的答案效果很好，但是IOUtils.copy(in,out)对于大文档来说需要花费很多时间。原因是您试图通过 4KB 迭代来编写 blob。更简单的解决方案：
Blob blob = rs.getBlob(column);
InputStream in = blob.getBinaryStream();
OutputStream out = new FileOutputStream(someFile);
byte[] buff = blob.getBytes(1,(int)blob.getLength());
out.write(buff);
out.close();
Your outputStream will write the blob in one shot.
您的 outputStream 将一次性写入 blob。
Edit
编辑
Sorry didn't see the Edit section on the intial Post.
抱歉没有看到初始帖子的编辑部分。
