Overview 1. What is JDBC? 2. The JDBC-ODBC Bridge 3. JDBC Pseudocode 4. simpJDBC.java

5. Meta Data 6. Books.mdb as an ODBC Data Source

What is JDBC? What is JDBC? JDBC provides a set of classes for Java with a standard SQL database access interface. JDBC provides a set of classes for Java with a standard SQL database access interface. Allow programs to access to a wide range of relational databases which follow the ANSI SQL-2 standard Allow programs to access to a wide range of relational databases which follow the ANSI SQL-2 standard Provides an API for database "drivers" to make actual connections and transactions to databases. Provides an API for database "drivers" to make actual connections and transactions to databases.

JDBC in Use Java program connectivity data processing utilities JDBC driver for Oracle driver For MySQL jdbc-odbc bridge odbc driver

The JDBC-ODBC Bridge ODBC (Open Database Connectivity) is a Microsoft standard from the mid 1990’s. ODBC (Open Database Connectivity) is a Microsoft standard from the mid 1990’s. It is an API that allows C/C++ programs to execute SQL inside databases It is an API that allows C/C++ programs to execute SQL inside databases ODBC is supported by many products. ODBC is supported by many products.

The JDBC-ODBC bridge allows Java code to use the C/C++ interface of ODBC The JDBC-ODBC bridge allows Java code to use the C/C++ interface of ODBC –it means that JDBC can access many different database products The layers of translation (Java --> C -- > SQL) can slow down execution. The layers of translation (Java --> C -- > SQL) can slow down execution.

The JDBC-ODBC bridge comes free with the JDK: The JDBC-ODBC bridge comes free with the JDK: –called sun.jdbc.odbc.JdbcOdbcDriver The ODBC driver for Microsoft Access comes with MS Office The ODBC driver for Microsoft Access comes with MS Office –so it is easy to connect Java and Access

JDBC Drivers list of drivers (freeware, shareware, and commercial) list of drivers (freeware, shareware, and commercial) Sun Microsystems JDBC home page Sun Microsystems JDBC home page –Java.sun.com/products/jdbc SQL materials SQL materials –

JDBC PseudoCode All JDBC programs do the following: All JDBC programs do the following: –1) load the JDBC driver –2) Specify the name and location of the database being used –3) Connect to the database with a Connection object Continued

–4) Execute a SQL query using a Statement object –5) Get the results in a ResultSet object –6) Finish by closing the ResultSet, Statement and Connection objects

Pseudocode Diagram DriveManagerConnectionStatementResultSet creates Driver SQL data make link to driver

DriveManager It is responsible for establishing the connection to the database through the driver. It is responsible for establishing the connection to the database through the driver. e.g. e.g. Class.forName( "sun.jdbc.odbc.JdbcOdbcDriver"); Connection conn = DriveManager.getConnection(url);

Name the Database The name and location of the database is given as a URL The name and location of the database is given as a URL –the details of the URL vary depending on the type of database that is being used

ODBC Database URL jdbc:odbc: //host.domain.com: 1511 /data/file The comms protocol The machine holding the database. The port used for the connection. The path to the database on the machine e.g. jdbc:odbc:Books

Statement Object The Statement object provides a ‘workspace’ where SQL queries can be created, executed, and results collected. The Statement object provides a ‘workspace’ where SQL queries can be created, executed, and results collected. e.g. e.g. Statement st = conn.createStatement(): ResultSet rs = st.executeQuery( “ select * from Students” ); : st.close();

ResultSet Object Stores the results of a SQL query. Stores the results of a SQL query. A ResultSet object is similar to a ‘table’ of answers, which can be examined by moving a ‘pointer’ (cursor). A ResultSet object is similar to a ‘table’ of answers, which can be examined by moving a ‘pointer’ (cursor). Continued

Cursor operations: Cursor operations: –first(), last(), next(), previous(), etc. Typical code: Typical code: while( rs.next() ) { // process the row; } John Mark Paul Peter cursor 3

Demo Set up Access Database Set up Access Database Set up ODBC source Set up ODBC source

Make a Access Database “JDBCStudent”

Add Data to Students Table

Press “Add’ to add a data source and select Microsoft Access Driver (*.mdb). Press “Finish”. Press “Add’ to add a data source and select Microsoft Access Driver (*.mdb). Press “Finish”. Add ODBC datasource ControlPanel: administrator tools. ODBC Data Sources Administrator

Type in a source name, description, and press “Select” to browse to set the path to the JDBCStduent.mdb file.

Username & Password The database’s link to the outside (e.g. its ODBC interface) must be configured to have a login and password The database’s link to the outside (e.g. its ODBC interface) must be configured to have a login and password

ClicK Advanced ClicK Advanced Type in a username and password (guest). Click “Ok” Type in a username and password (guest). Click “Ok”

simpJDBC.java // simpJDBC.java import java.sql.*; public class JdbcSimple { private java.sql.Connection connection; public JdbcSimple(){ String url = "jdbc:odbc:cs483"; String username = "anonymous"; String password = "guest";

try { // load the JDBC-ODBC Bridge driver Class.forName("sun.jdbc.odbc.JdbcOdbcDriver"); // connect to db using DriverManager Connection conn = DriverManager.getConnection( url, username, password ); // Create a statement object Statement statement = conn.createStatement(); // Execute the SQL query ResultSet rs = statement.executeQuery( "SELECT lastName, firstName FROM Authors" ); :

// Print the result set while( rs.next() ) System.out.println( rs.getString("lastName") + ", " + rs.getString("firstName") ); // Close down statement.close(); conn.close(); } :

catch ( ClassNotFoundException cnfex ) { System.err.println( "Failed to load JDBC/ODBC driver." ); cnfex.printStackTrace(); System.exit( 1 ); // terminate program } catch ( SQLException sqlex ) { System.err.println( sqlex ); sqlex.printStackTrace(); } } // end of main() } // end of simpJDBC class

Accessing a ResultSet The ResultSet class contains many methods for accessing the value of a column of the current row The ResultSet class contains many methods for accessing the value of a column of the current row –can use the column name or position –e.g. get the value in the lastName column: rs.getString("lastName") Continued

The ‘tricky’ aspect is that the values are SQL data, and so must be converted to Java types/objects. The ‘tricky’ aspect is that the values are SQL data, and so must be converted to Java types/objects. There are many methods for accessing/converting the data, e.g. There are many methods for accessing/converting the data, e.g. –getString(), getDate(), getInt(), getFloat(), getObject()

Meta Data Meta data is the information about the database: Meta data is the information about the database: –e.g. the number of columns, the types of the columns –meta data is the schema information IDNameCourseMark 007JamesCS JetMath10080 meta data

Accessing Meta Data The getMetaData() method can be used on a ResultSet object to create its meta data object. The getMetaData() method can be used on a ResultSet object to create its meta data object. e.g. e.g. ResultSetMetaData md = rs.getMetaData();

Using Meta Data int numCols = md.getColumnCount(); for (int i = 0; i <= numCols; i++) { if (md.getColumnType(i) == Types.CHAR) System.out.println( md.getColumnName(i) ) }

More Meta Data Methods getTableName() getTableName() getPrecision() getPrecision() –number of decimal digits in the column isSigned() isSigned() –returns true if column has signed numbers isCurrency() isCurrency() etc. etc.

Summary: Setting up the Data Source Create a new Database Create a new Database –AddressBookDB ID, firstName, lastName,... ID, firstName, lastName,... Create a DSN for the Database Create a DSN for the Database –DSN: Data Source Name tells your program which database to use! tells your program which database to use! Done in the ODBC control panel Done in the ODBC control panel the DSN is what will be required in the URL to the Database for ODBC!! the DSN is what will be required in the URL to the Database for ODBC!!

Summary: Steps in using JDBC Load the appropriate JDBC driver Load the appropriate JDBC driver –Done using dynamic class loading in Java Open a Connection to the Database Open a Connection to the Database Create a new query as an SQL Statement Create a new query as an SQL Statement Execute the query Execute the query Process the ResultSet Process the ResultSet –for database meta-data and the records Close the Statement Close the Statement Close the ResultSet Close the ResultSet Close the database connection Close the database connection

Creating JDBC statements A statement object is what sends your SQL statement to DBMS. You create a statement object and execute it. The method to use is executeQuery or executeUpdate. A statement object is what sends your SQL statement to DBMS. You create a statement object and execute it. The method to use is executeQuery or executeUpdate. – Statement stmt = dbConnection.createStatement(); – String sqlState = new String ( "SELECT FirstName, LastName FROM ATable"); – ResultSet myResults = stmt.executeQuery( sqlState );

Statement Statement stmt = connection.createStatement(); Statement stmt = connection.createStatement(); stmt.executeQuery(String); stmt.executeQuery(String); stmt.executeUpdate(String); stmt.executeUpdate(String);

PreparedStatement Better performance Better performance String sql = "select ? from atable"; String sql = "select ? from atable"; PreparedStatement stmt = PreparedStatement stmt = connection.prepareStatement(sql); connection.prepareStatement(sql); stmt.setString(1, ”acolumn"); stmt.setString(1, ”acolumn"); ResultSet rs = stmt.execute(); ResultSet rs = stmt.execute(); The "1" replaces the first "?" in the statement The "1" replaces the first "?" in the statement A "2" would replace the second "?" in the statement A "2" would replace the second "?" in the statement

ResultSet Queries return results in a ResultSet Queries return results in a ResultSet Provides row-by-row access to results Provides row-by-row access to results Must call next() before getting data Must call next() before getting data Can get data out by data type Can get data out by data type Can refer to columns by index or by name Can refer to columns by index or by name

Getting and processing the results while( myResults.next()) while( myResults.next()) { System.out.println(myResults.getString(1) + " " + myResults.getString(2)); System.out.println(myResults.getString(1) + " " + myResults.getString(2)); }

Example: getTable try { String query = "SELECT * FROM Authors"; statement = connection.createStatement(); resultSet = statement.executeQuery( query ); displayResultSet( resultSet ); statement.close(); } catch ( SQLException sqlex ) { sqlex.printStackTrace(); }

Display Table // position to first record boolean moreRecords = rs.next(); if ( ! moreRecords ) { return; } // get column heads ResultSetMetaData rsmd = rs.getMetaData(); for ( int i = 1; i <= rsmd.getColumnCount(); ++i ) columnHeads.addElement( rsmd.getColumnName( i ) ); // get row data do { rows.addElement( getNextRow( rs, rsmd ) ); } while ( rs.next() );

Get a row Vector currentRow = new Vector(); for ( int i = 1; i <= rsmd.getColumnCount(); ++i ) switch( rsmd.getColumnType( i ) ) { case Types.VARCHAR: currentRow.addElement( rs.getString( i ) ); break; case Types.INTEGER: currentRow.addElement( new Long( rs.getLong( i ) ) ); break; default: System.out.println( "Type was: " + rsmd.getColumnTypeName( i ) ); }

ResultSetMetaData ResultSetMetaData md = rs.getMetaData(); ResultSetMetaData md = rs.getMetaData(); md.getColumnName(int); md.getColumnName(int); md.getColumnType(int); md.getColumnType(int); md.getColumnCount(); md.getColumnCount();

Find in a Table Statement statement =connection.createStatement(); String query = "SELECT * FROM addresses " + String query = "SELECT * FROM addresses " + "WHERE lastname = '" + "WHERE lastname = '" + fields.last.getText() + "'"; fields.last.getText() + "'"; ResultSet rs = statement.executeQuery( query ); ResultSet rs = statement.executeQuery( query ); display( rs ); display( rs );

Update a Table Statement statement = connection.createStatement(); if ( ! fields.id.getText().equals( "" ) ) { String query = "UPDATE addresses SET " + "firstname='" + fields.first.getText() + "', lastname='" + fields.last.getText() + "' WHERE id=" + fields.id.getText(); int result = statement.executeUpdate( query ); if ( result == 1 ) output.append( "\nUpdate successful\n" ); else { output.append( "\nUpdate failed\n" ); }

Another Database Books.mdb Publishers PublisherID PublisherName Titles ISBN Title EditionNumber YearPublished Description PublisherID AuthorISBN ISBN AuthorID Authors AuthorID FirstName LastName YearBorn

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