Introduction to JDBC• Standard framework for dealing with tabular and

generally, relational data• SQL (Structured Query Language) is standardized

language to interact with database• A database is essentially a smart container for

tables (file system).• A table is a container comprised of rows (file).• A row is (conceptually) a container comprised of

columns (record or structure). • A column is a single data item having a name,

type, and value (field or variable).

ODBC

• Open Database Connectivity

• C-based interface to SQL engines

• Individual vendors provide drivers or bridges to their database management system (dbms)

• Platform specific

JDBC

• java.sql or JDBC

• Portable version of ODBC

• JDBC Driver converts SQL requests for a particular database

Driver Types

• 1: JDBC-ODBC bridge plus ODBC driver: JDBC access via ODBC drivers

• 2: Native-API partly-Java driver: JDBC calls converted into dbms specific code

• 3: JDBC-Net pure Java Driver: JDBC calls to DBMS-independent net protocol. Server converts to DBMS protocol

• 4: Native-protocol pure Java driver: JDBC directly to network protocol used by DBMS

JDBC

• Java Database Connectivity

• JDBC 1.0 API compatible with jdk1.1 and jdk1.2

• JDBC 2.0 API compatible with jdk1.2 and greater

• Get JDBC API with respective JDK

JDBC 1.0• Driver • DriverManager • Connection • Statement • PreparedStatement • CallableStatement • ResultSet • DatabaseMetaData • ResultSetMetaData • Types

JDBC 2.0

• Core API

• JDBC 2.0 Optional package

• Performance and functionality enhancements

Steps

• Create the database

• Connect to database

• Create table

• Insert information into database

• Selectively retrieve information

• Example using J2SDKEE and Cloudscape database

Getting Started

• Install a driver for specific DBMS

• JDBC-ODBC Bridge driver more complicated. Comes with JDK, but ODBC needs some set up

• Install DBMS

Creating a Database

• DBMS-Specific

• Administrator Privledges

• Set database connection URL attribute that is passed to driver (create=true)

• Named database is created in DBMS default directory (J2EE_HOME/Cloudscpae)

Connecting to Database

• Load JDBC Driver:Class.forName( DriverClassName);Class.forName(DriverClassName).newInstance();

• From Command Line: java -Djdbc.drivers=DriverClassName AJavaAppCOM.cloudscape.core.RmiJdbcDriver

• Connect to Data sourceConnection con = DriverManager.getConnectio( URL, Username, Password );

• Database now created

Establish a Connection

• Load the Driver– Class.forName("sun.jdbc.odbc.JdbcOdbcDriver

");

– Class.forName("jdbc.DriverXYZ");

– Driver automatically loaded

• Establish Connection• Connection con = DriverManager.getConnection(url,

"myLogin", "myPassword");

• String url = "jdbc:odbc:Fred"; Connection con = DriverManager.getConnection(url, "Fernanda", "J8");

• Vendor specific subprotocol subs for “odbc”

• DriverManager manages all details of connection

• Driver class for Driver developers

Create a Table

• Get Statement object from connectionStatement stmt = con.createStatement();

• stmt.executeUpdate( "CREATE TABLE JJJJData (" +

• "Entry INTEGER NOT NULL, " +

• "Customer VARCHAR (20) NOT NULL, " +

• "DOW VARCHAR (3) NOT NULL, " +

• "Cups INTEGER NOT NULL, " +

• "Type VARCHAR (10) NOT NULL," +

• "PRIMARY KEY( Entry )" +

• ")" );

Insert Information

• Now that the table has been created, the data can be entered using the SQL INSERT statement:

• INSERT INTO JJJJData VALUES ( 1, 'John', 'Mon', 1, 'JustJoe' )

• INSERT INTO JJJJData VALUES ( 2, 'JS', 'Mon', 1, 'Cappuccino' )

• INSERT INTO JJJJData VALUES ( 3, 'Marie', 'Mon', 2, 'CaffeMocha' )

• ...

• In the example program, an array named SQLData contains the actual values, with each element in a form like this: "(1, 'John', 'Mon', 1, 'JustJoe')”

• The program code corresponding to the INSERT statements above is:

• stmt.executeUpdate(

• "INSERT INTO JJJJData VALUES " + SQLData[i] );

Entry Customer DOW CupsType

1 John Mon 1JustJ oe

2 JS Mon 1Cappuccino

3 Marie Mon 2CaffeMocha

4 Anne Tue 8Cappuccino

5 Holley Tue 2MoJava

6 jDuke Tue 3Cappuccino

7 Marie Wed 4Espresso

8 JS Wed 4Latte

9 Alex Thu 3Cappuccino

10 James Thu 1Cappuccino

11 jDuke Thu 4JustJ oe

12 JS Fri 9Espresso

import java.sql.*;

public class Create4JData{

static String[] SQLData = { "(1, 'John', 'Mon', 1, 'JustJoe')", "(2, 'JS', 'Mon', 1, 'Cappuccino')", "(3, 'Marie', 'Mon', 2, 'CaffeMocha')", "(4, 'Anne', 'Tue', 8, 'Cappuccino')", "(5, 'Holley', 'Tue', 2, 'MoJava')", "(6, 'jDuke', 'Tue', 3, 'Cappuccino')", "(7, 'Marie', 'Wed', 4, 'Espresso')", "(8, 'JS', 'Wed', 4, 'Latte')", "(9, 'Alex', 'Thu', 3, 'Cappuccino')", "(10, 'James', 'Thu', 1, 'Cappuccino')", "(11, 'jDuke', 'Thu', 4, 'JustJoe')", "(12, 'JS', 'Fri', 9, 'Espresso')", "(13, 'John', 'Fri', 3, 'Cappuccino')", "(14, 'Beth', 'Fri', 2, 'Cappuccino')", "(15, 'jDuke', 'Fri', 1, 'Latte')" };

public static void main(String[] args) {

Connection con = null; int iRowCount = 0; Statement stmt = null;

String sDriver = "COM.cloudscape.core.RmiJdbcDriver"; String sURL = "jdbc:cloudscape:rmi:jGuru;create=true"; String sUsername = "sa"; String sPassword = "admin";

try // Attempt to load the JDBC driver { // with newInstance by name Class.forName( sDriver ).newInstance(); } catch( Exception e ) // error { System.err.println( "Failed to load current driver."); return; } // end catch

try {

con = DriverManager.getConnection ( sURL, sUsername, sPassword); stmt = con.createStatement(); } catch ( Exception e) { System.err.println( "problems connecting to " + sURL + ":" ); System.err.println( e.getMessage() );

if( con != null) { try { con.close(); } catch( Exception e2 ) {} }

return; } // end catch

// to allow the program to be run more than once, // attempt to remove the table from the database try { stmt.executeUpdate( "DROP TABLE JJJJData" ); System.out.println( "Table JJJJData was removed."); } catch ( Exception e ) { /* don't care */ }

// execute SQL commands // to create table and insert data try { stmt.executeUpdate( "CREATE TABLE JJJJData (" + "Entry INTEGER NOT NULL, " + "Customer VARCHAR (20) NOT NULL, " + "DOW VARCHAR (3) NOT NULL, " + "Cups INTEGER NOT NULL, " + "Type VARCHAR (10) NOT NULL," + "PRIMARY KEY( Entry )" + ")" );

System.out.println( "Table JJJJData was created.");

for (int i = 0; i < SQLData.length; i++) { iRowCount += stmt.executeUpdate( "INSERT INTO JJJJData VALUES " + SQLData[i] ); }

System.out.println( iRowCount + " Rows inserted into JJJJData.");

} catch ( Exception e ) { System.err.println( "problem with SQL sent to " + sURL + ":" ); System.err.println( e.getMessage() ); }

finally { try { stmt.close(); } catch( Exception e ) {}

try { con.close(); } catch( Exception e ) {} } // end finally clause

} // end main

} // end class Create4JData

Retrieving Information

• Get maximum cups of coffee consumed by returning data in decreasing order by number of cups, and then get first row:

• ResultSet result = stmt.executeQuery(• "SELECT Entry, Customer, DOW, Cups, Type " +• "FROM JJJJData " +• "ORDER BY Cups DESC");• if( result.next() ) // get first row • { // if data was returned• sCustomer = result.getString("Customer");• iCups = result.getInt("Cups");• System.out.println(• "On " + result.getString("DOW") +• " 4J Customer " + sCustomer + • " consumed the most coffee." +

Data Navigation• while(result.next()) // for each row of data• {• iEntry = result.getInt("Entry");• sCustomer = result.getString("Customer");• sDOW = result.getString("DOW");• iCups = result.getInt("Cups");• iTotalCups += iCups; // increment total• sType = result.getString("Type");

• // Report each Customer• System.out.println( iEntry + ",\t" +• sCustomer + ",\t" +• sDOW + ",\t" +• iCups + ",\t" +• sType );• }

Data Extraction

• Once at a row, get data column at a time:

• iEntry = result.getInt("Entry");

• Customer = result.getString("Customer");

• DOW = result.getString("DOW");

• Cups = result.getInt("Cups");

• TotalCups += Cups; // increment total

• Type = result.getString("Type");

import java.sql.*;

public class Report4J{ public static void main (String args[]) { Connection con = null; int iCups, iTotalCups, iEntry; Statement stmt = null;

String sDriver = "COM.cloudscape.core.RmiJdbcDriver"; String sURL = "jdbc:cloudscape:rmi:jGuru";// "jdbc:rmi:jdbc:cloudscape:jGuru;create=true"; String sUsername = "sa"; String sPassword = "admin";

String sCustomer = null, sDOW = null, sType = null;

try // Attempt to load the JDBC driver { // with newInstance Class.forName( sDriver ).newInstance(); } catch( Exception e ) // error { System.err.println( "Failed to load current driver."); return; } // end catch

try { con = DriverManager.getConnection ( sURL, sUsername, sPassword); stmt = con.createStatement(); } catch ( Exception e) { System.err.println( "problems connecting to " + sURL + ":" ); System.err.println( e.getMessage() );

if( con != null) { try { con.close(); } catch( Exception e2 ) {} }

return; } // end catch

try { ResultSet result = stmt.executeQuery( "SELECT Entry, Customer, DOW, Cups, Type " + "FROM JJJJData " + "ORDER BY Cups DESC");

if( result.next() ) // get first row { // if data was returned sCustomer = result.getString("Customer"); iCups = result.getInt("Cups"); System.out.println( "On " + result.getString("DOW") + " 4J Customer " + sCustomer + " consumed the most coffee." +

" Cups: " + iCups + ", Type: " + result.getString("Type") + ".\n");

iTotalCups = iCups; // increment total

while(result.next()) // for each row of data { iEntry = result.getInt("Entry"); sCustomer = result.getString("Customer"); sDOW = result.getString("DOW"); iCups = result.getInt("Cups"); iTotalCups += iCups; // increment total sType = result.getString("Type");

// Report each Customer System.out.println( iEntry + ",\t" + sCustomer + ",\t" + sDOW + ",\t" + iCups + ",\t" + sType ); }

// Report total System.out.println( "\n4J Cafe Total Weekly Sales: " + iTotalCups + " cups of coffee.");

} // end if( result.next() )

} // end try catch (Exception e) { e.printStackTrace(); } finally { try { stmt.close(); } catch( Exception e ) {}

try { con.close(); } catch( Exception e ) {} } // end finally clause

} // end main

} // end class Report4J