Using Oracle JDBC How to Run JDBC on Your Account Communication Mechanism Using Metadata Building a Database Auto Commit v.s Atomic Transaction

# environment variables for Oracle setenv ORACLE_TERM vt100 setenv ORACLE_SID CIS setenv ORACLE_BASE /u01/home/dba/oracle setenv ORACLE_HOME /u01/home/dba/oracle/product/7.1.4 setenv NLS_LANG AMERICAN_AMERICA.US7ASCII set path=($ORACLE_HOME/bin $path) # environment variables for Java class files setenv CLASSPATH./:/pkg/java1.1.6/lib/classes.zip: /pkg/cis550/JDBC/lib/classes111.zip # path to find the Java compiler and VM set path=(/pkg/java-1.1.6/bin. $path ) # path to find libraries for Oracle JDBC drivers setenv LD_LIBRARY_PATH /pkg/cis550/JDBC/lib setenv EPC_DISABLED TRUE

class JdbcTest { public static void main (String args []) throws SQLException, IOException { try { Class.forName ("oracle.jdbc.driver.OracleDriver"); } catch (/*ClassNotFound*/ Exception e) { e.printStackTrace (); } Connection conn = Statement stmt = conn.createStatement (); ResultSet rset = stmt.executeQuery ("select table_name from tabs"); while (rset.next ()) { System.out.println (rset.getString (1)); }; stmt.close(); conn.close();} }

Database Accessing Mechanism Registering a database driver. Using DriverManager to obtain a Connection that represents a database connection. Sending a SQL statement to the database using Statement. Retrieving the query result with a ResultSet.

Using Metadata Class.forName ("oracle.jdbc.driver.OracleDriver"); Connection conn= Statement stmt = conn.createStatement (); ResultSet rset = stmt.executeQuery(sql_query_string); ResultSetMetaData metadata = rset.getMetaData(); int numcols = metadata.getColumnCount(); // how many columns String labl1 = metadata.getColumnLabel(1); // get the first label int size = metadata.getColumnDisplaySize(1); // get the column width Look into the database itself and its contents.

Building a Database Repeatedly use INSERT INTO Increase the efficiency by providing PreparedStatement: database interprets the prepared statement and creates its template just once. insertSailor = conn.prepareStatement(“INSERT INTO Sailor VALUES(?, ?, ?); //sailor_name, sailor_rating, sailor_age

Atomic Transactions A newly-created Connection is “auto commit” Each update is as a separate transaction and automatically committed to the database. How to “group” several updates into a single “atomic” transaction? –Take Connection out of “auto commit” mode. –Explicitly call commit() to a batch of transactions –call rollback() to abort a batch of transactions.

Class.forName ("oracle.jdbc.driver.OracleDriver"); Connection conn= conn.setAutoCommit(FALSE); conn.setTransactionIsolation(Connection.TRANSACTION_READ _COMMITTED); Statement stmt = conn.createStatement (); try{ stmt.executeUpdate(sql_str_Insert_Account_Table); stmt.executeUpdate(sql_str_Create_History_Table); stmt.executeUpdate(sql_str_Insert_History_Table); conn.commit(); // commit the updates } catch(SQLException e) { conn.rollback(); // removes all updates from the database }