A BLOB (Binary Large OBject) is essentially an array of bytes (byte[]), stored in the database. You
extract the data in two steps:
1. Call the getBlob method of the Statement class to retrieve a java.sql.Blob object
2. Call either getBinaryStream or getBytes in the extracted Blob object to retrieve the java byte[] which
is the Blob object.
Note that a Blob is essentially a pointer to a byte array (called LOCATOR in database-talk), so the
java.sql.Blob object essentially wraps a byte pointer. Thus, you must extract all data from the database
blob before calling commit or
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private void runGetBLOB()
{ try
{ // Prepare a Statement:
PreparedStatement stmnt = conn.prepareStatement("select aBlob from BlobTable");
// Execute
ResultSet rs = stmnt.executeQuery();
while(rs.next())
{ try
{ // Get as a BLOB
Blob aBlob = rs.getBlob(1);
byte[] allBytesInBlob = aBlob.getBytes(1, (int) aBlob.length());
} catch(Exception ex)
{ // The driver could not handle this as a
BLOB...
// Fallback to default (and slower) byte[] handling
byte[] bytes = rs.getBytes(1);
}}
// Close resources
rs.close();
stmnt.close();
} catch(Exception ex)
{ this.log("Error when trying to read BLOB: "
+
ex);
}}
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