Using Java with PSQL and Oracle Thanks to Drs. Raj and Liu for sharing some of these slides TRUDY: ALSO NEED SAMPLE PROGRAM

In this slide deck: Tips for using PSQL and Oracle Some “gotchas” for working with the Java database interface

psql You will need a separate psql account – see your instructor Server runs on reddwarf You need to provide your password each time you invoke psql

psql Full documentation and a tutorial are available online Default is a command line interface that isn’t very forgiving with typos or to reissue commands Several UI skins exist; some are open source – check around or write your own

psql passwords The psql interpreter will bypass the password prompt if it sees a.pgpass file in your home directory Enter a single line: localhost:*:*:Your_Username:Your_Password (host:port:db:username:password) IMPORTANT – SEE NEXT SLIDE

psql passwords Be sure to chmod 600 to set permissions on the file Our system admin has approved storing this plain-text password IF you do not use the same password as your CS account DO NOT USE THE SAME PASSWORD AS YOUR CS ACCOUNT!

Getting started with psql Assuming you use bash: Edit your.bashrc file to include the following: export path=/usr/lib/postgresql/9.1/bin/:$path You will also need this for the Java JDBC: export CLASSPATH=/home/student/abc1234/db/ postgresql jdbc4.jar:$CLASSPATH (all one line. Substitute “/home/student/abc1234” with your own path name

Integrating psql with Java You also need the.jar file in your working directory. See my website download page for the link. Review demo program Note that much of your understanding will be achieved through experimentation and studying the appropriate javadocs!

Continue to the next slides if using Oracle

Setting Java Environment for Oracle To use sqlplus and JDBC from a Java program – Ensure CLASSPATH is set up correctly – csh users can source the following file /usr/local/bin/coraenv Put it in your.cshrc file – bash users can source the following file /usr/local/bin/oraenv Put it in your.bashrc file Sample Java program – See course webpage under DBMS Docs You must modularize this program! Understand password privacy issues involved here!

Using the CS Department Connecting to Oracle directly – sqlplus – Use this primarily for running DDL scripts Connecting to a DBMS with a Java program – Use the Oracle JDBC driver – Read CRUD and the javadocs Demonstration

Java Classes/Interfaces: java.sql, javax.sql DriverManager – getConnection Connection – createStatement, prepareStatement, commit, setAutoCommit, close Statement – executeQuery, executeUpdate, close PreparedStatement – execute, commit, close, setint, setString ResultSet – next, getString, getInt Some useful classes and methods Some useful classes and methods

JDBC Introduction Useful to read the following SUN’s JDBC tutorial – java.sun.com/docs/books/tutorial/index.html Steps for Oracle (similar for any other DBMS) – Load the driver – Connect to the DBMS – Send SQL to the DBMS – Process the results of your queries – Cleanup

Load the Driver and Connect to Oracle Several steps rolled into one Class.forName( "oracle.jdbc.driver.OracleDriver"); String url = Connection con = DriverManager.getConnection( url, dbUser, dbPassword );

Send SQL to the DBMS Just send the SQL … stmt.executeUpdate("insert into A values(2009)" ); Expect some goodies back String query = "select name, salary, emp_no from employee"; ResultSet rs = stmt.executeQuery( query );

Process Query Results Get the result set ResultSet rs = stmt.executeQuery( query ); Process the result set, row by row while ( rs.next() ) { String emp_name = rs.getString( "name“ ); int emp_no = rs.getInt( "emp_no“ ); double salary = rs.getDouble( "salary“ ); System.out.println( emp_name + ", " + emp_no + “ makes $" + salary + “.“ ); }

Java and SQL: Type Mappings Data is represented in two places – In the database SQL type DB programmer responsibility – In Java program Java type Java programmer responsibility get??? calls Java method SQL Type getIntINTEGER getObject any type getLong BIG INT getFloatFLOAT getDoubleREAL getBignumDECIMAL getBooleanBIT getStringVARCHAR getStringCHAR getDateDATE getTimeTIME getTimestamp TIME STAMP

Cleanup Close out the statement and connection stmt.close( ); con.close( );