Java Interview Questions On JDBC Conectivity Page7 - How to set a scroll type? | How to do a batch job?

Answer
Both Statements and PreparedStatements have an additional constructor that accepts a scroll type and an update type parameter. The scroll type value can be one of the following values:

ResultSet.TYPE_FORWARD_ONLY Default behavior in JDBC 1.0, application can only call next() on the result set.
ResultSet.SCROLL_SENSITIVE ResultSet is fully navigable and updates are reflected in the result set as they occur.

ResultSet.SCROLL_INSENSITIVE Result set is fully navigable, but updates are only visible after the result set is closed. You need to create a new result set to see the results.

27. How to do a batch job?

Answer:
By default, every JDBC statement is sent to the database individually. To send multiple statements at one time , use addBatch() method to append statements to the original statement and call executeBatch() method to submit entire statement.

Statement stmt = con.createStatement();
stmt.addBatch("update registration set balance=balance-5.00 where theuser="+theuser);
stmt.addBatch("insert into auctionitems(description, startprice) values("+description+","+startprice+")");
...
int[] results = stmt.executeBatch();

The return result of the addBatch() method is an array of row counts affected for each statement executed in the batch job. If a problem occurred, a java.sql.BatchUpdateException is thrown. An incomplete array of row counts can be obtained from BatchUpdateException by calling its getUpdateCounts() method.

28. How to store and retrieve an image?

Answer
To store an image, you may use the code:
int itemnumber=400456;
File file = new File(itemnumber+".jpg");
FileInputStream fis = new FileInputStream(file);
PreparedStatement pstmt = con.prepareStatement("update auctionitems set theimage=? where id= ?");
pstmt.setBinaryStream(1, fis, (int)file.length()):
pstmt.setInt(2, itemnumber);
pstmt.executeUpdate();
pstmt.close();
fis.close();

To retrieve an image:

int itemnumber=400456;
byte[] imageBytes;//hold an image bytes to pass to createImage().

PreparedStatement pstmt = con.prepareStatement("select theimage from auctionitems where id= ?");
pstmt.setInt(1, itemnumber);
ResultSet rs=pstmt.executeQuery();
if(rs.next()) {
imageBytes = rs.getBytes(1);
}
pstmt.close();
rs.close();
Image auctionimage = Toolkit.getDefaultToolkit().createImage(imageBytes);