使用JDBC处理二进制数据
/*Database Programming with JDBC and Java, Second Edition
By George Reese
ISBN: 1-56592-616-1
Publisher: O'Reilly
*/
import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.sql.Blob;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
/**
* Example 4.2.
*/
public class Blobs {
public static void main(String args[]) {
if (args.length != 1) {
System.err.println("Syntax: <java Blobs "
+ " ");
return;
}
try {
Class.forName(args).newInstance();
Connection con = DriverManager.getConnection(args, args,
args);
File f = new File(args);
PreparedStatement stmt;
if (!f.exists()) {
// if the file does not exist
// retrieve it from the database and write it to the named file
ResultSet rs;
stmt = con.prepareStatement("SELECT blobData "
+ "FROM BlobTest " + "WHERE fileName = ?");
stmt.setString(1, args);
rs = stmt.executeQuery();
if (!rs.next()) {
System.out.println("No such file stored.");
} else {
Blob b = rs.getBlob(1);
BufferedOutputStream os;
os = new BufferedOutputStream(new FileOutputStream(f));
os.write(b.getBytes(0, (int) b.length()), 0, (int) b
.length());
os.flush();
os.close();
}
} else {
// otherwise read it and save it to the database
FileInputStream fis = new FileInputStream(f);
byte[] tmp = new byte;
byte[] data = null;
int sz, len = 0;
while ((sz = fis.read(tmp)) != -1) {
if (data == null) {
len = sz;
data = tmp;
} else {
byte[] narr;
int nlen;
nlen = len + sz;
narr = new byte;
System.arraycopy(data, 0, narr, 0, len);
System.arraycopy(tmp, 0, narr, len, sz);
data = narr;
len = nlen;
}
}
if (len != data.length) {
byte[] narr = new byte;
System.arraycopy(data, 0, narr, 0, len);
data = narr;
}
stmt = con.prepareStatement("INSERT INTO BlobTest(fileName, "
+ "blobData) VALUES(?, ?)");
stmt.setString(1, args);
stmt.setObject(2, data);
stmt.executeUpdate();
f.delete();
}
con.close();
} catch (Exception e) {
e.printStackTrace();
}
}
}
页:
[1]