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Reading and writing blob from the oracle database.

5595Jul 17 2002
Hi all,

I am using Oracle 8.1.5 on WinNT. I have written a code for inserting a file in the table which has a column defined as blob. I have classes111.zip in the classpath. Following are the important snippets from the code:

......
static final String driver_class = "oracle.jdbc.driver.OracleDriver";
static final String connect_string = "jdbc:oracle:thin:scott/tiger@ibm-hard:1521:orabt";
....
Class.forName (driver_class);
conn = DriverManager.getConnection (connect_string);
conn.setAutoCommit(false);
....
String sqlStmt = "INSERT INTO TEST_BLOB VALUES ('object1', empty_blob())";
stat = conn.createStatement();
stat.executeQuery(sqlStmt);
String updateSQL = "select report_doc from test_blob where report_name='object1' for update";
rs = stat.executeQuery(updateSQL);
rs.next();
BLOB blob = ((OracleResultSet)rs).getBLOB("report_doc");
OutputStream os = blob.getBinaryOutputStream();
File f = new File("D:\\Project\\molsa\\social_schema.txt");
InputStream is = new FileInputStream(f);
int fileLength = (int)f.length();
final byte[] buffer = new byte[(int)fileLength];
System.out.println("File length is " + fileLength);
int bytesRead = 0;
int totalBytesRead = 0;
while((bytesRead = is.read(buffer)) != -1) {
totalBytesRead += bytesRead;
System.out.println(totalBytesRead);
os.write(buffer, 0, bytesRead);
}
...........


When I run this program everything seems to have run fine. But when I am trying to read the same blob using the following code:

------------------------------------------------------------------
String getDocSQL = "select * from test_blob";
stat = conn.createStatement();
rs = stat.executeQuery(getDocSQL);
while(rs.next()) {
BLOB blobData = ((OracleResultSet)rs).getBLOB("report_doc");
InputStream is = blobData.getBinaryStream();
FileOutputStream fos = new FileOutputStream(new File("D:\\Project\\molsa\\social_schema1.txt"));
int totalBytesRead = 0;
final int bufferSize = (int) blobData.length();
byte[] buffer = new byte[bufferSize];
System.out.println("Length of data " + bufferSize);
int bytesRead = 0;
while ((bytesRead = is.read(buffer, 0, bufferSize)) != -1) {
fos.write(buffer, 0, bytesRead);
}
}
------------------------------------------------------------------

I am having two problems:
1. the size of the file is shown as a bit less than that of the file which I wrote initially.
2. and I am getting an exception

java.io.IOException: ORA-21560: argument 2 is null, invalid, or out of range
ORA-06512: at "SYS.DBMS_LOB", line 640
ORA-06512: at line 1

at oracle.jdbc.dbaccess.DBError.SQLToIOException(DBError.java:774)
at oracle.jdbc.driver.OracleBlobInputStream.needBytes(OracleBlobInputStream.java:141)
at oracle.jdbc.driver.OracleBufferedStream.read(OracleBufferedStream.java:107)
at ThinClient.main(ThinClient.java:83)



Thanks in advance
Vivek Singh

Comments

66232
Hi,
attached two functions one for dumping the other for loading ...

public class Test {
private File fHandle = null;
private static String PATH = null ;
private BLOB bHandle = null;
private String fileName = null ;

protected void dumpBlobToFile() throws SQLException
{

FileOutputStream outstream = null;
InputStream instream = null;

try {
getFileHandle(); // Gets a new file handle.
if (bHandle != null)
instream = bHandle.getBinaryStream(); // Get the blob input stream
else
return ;

if (outstream == null)
outstream = new FileOutputStream(fHandle); // Get the file output stream.


// Read the input stream and write the output stream by chunks.
byte[] chunk = new byte[bHandle.getChunkSize()];
int i = -1;

while ((i = instream.read(chunk)) != -1) {
outstream.write(chunk, 0, i);
}
outstream.flush();
} catch (IOException e) {
e.printStackTrace();
} finally {
try {

// Close the input and output stream.
if (instream != null) {
instream.close();
instream = null ;
}

if (outstream != null) {
outstream.close();
outstream = null ;
}

} catch (IOException e) {
e.printStackTrace();
}
}
}
protected void dumpFileToBlob() throws SQLException
{

FileInputStream instream = null;
OutputStream outstream = null;

try {
getFileHandle(); // Gets a new file handle.

if (bHandle != null) // Get the clob output stream
outstream = bHandle.getBinaryOutputStream();
else
return ;

if (instream == null)
instream = new FileInputStream(fHandle); // Get the file input stream.


// Read the input stream and write the output stream by chunks.
byte[] chunk = new byte[bHandle.getChunkSize()];
int i = -1;

while ((i = instream.read(chunk)) != -1) {
outstream.write(chunk, 0, i);
}
} catch (IOException e) {
e.printStackTrace();
} finally {
try {

// Close the input and output stream.
if (instream != null) {
instream.close();
instream = null ;
}

if (outstream != null) {
outstream.close();
outstream = null ;
}

} catch (IOException e) {
e.printStackTrace();
}
}
}

public void setPath(String path)
{
this.PATH = path ;
}
/**
* Get a file handle
*/
private void getFileHandle()
{
fHandle = new File(PATH + fileName);
}
}

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Post Details

Locked on Aug 15 2002
Added on Jul 17 2002
#java-database-connectivity-jdbc
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