JDBC

CS-328

JDBC

• Java API for accessing RDBMS

• Allows use of SQL for RDBMS programming

• Can be used for:– embedded SQL– execution of stored queries

SQL Statement Execution

• Four primary classes used to– load a driver

• (java.sql.DriverManager)

– connect to the DB • (java.sql.Connection)

– create a SQL statement• (java.sql.Statement)

– execute a SQL statement• (java.sql.ResultSet)

Example

try {try {

Class.forName (“sun.jdbc.odbc.JdbcOdbcDriver”);

String url = “jdbc:odbc:msaccessdb”;

Connection con = DriverManager.getConnection(url,””,””);

// create sql statement

String qs = “select * from loadtest”;

Statement stmt = con.createStatement();

// execute the statement

ResultSet rs = stmt.executeQuery(qs);

// process the result set

boolean more = rs.next;

while (more) {

System.out.println ............}}

Driver Manager Object

• Loads the proper driver into your java object– multiple drivers may be loaded to allow

connections to multiple databases

• Provides a common interface to RDBMSs for JDBC Drivers

Driver Manager Object

JAVA ApplicationJAVA Application

Driver ManagerDriver Manager

Driver ‘A’Driver ‘A’ Driver ‘B’Driver ‘B’

ConnectionConnection

StatementStatement

Result SetResult Set

ConnectionConnection

StatementStatement

Result SetResult Set

Driver Manager Class Methods

• getConnection(String url)• getDriver• registerDriver• deregisterDriver• getDrivers• setLoginTimeout• getLoginTimeout• setLogStream• getLogStream

Connection Object

• Establish link between the JAVA application and RDBMS

• allows application to select proper driver when it needs to

• uses the database URL to make the connection– jdbc:<subprotocol>:<subname)

• jdbc:odbc:Mydatabase

• jdbc:db2:157.287.43.11/Mydatabse

Connection Class Methods

• createStatement

• prepareStatement

• prepareCall

• NativeSQL

• setAutoCommit

• GetAutoCommit

• commit

• rollback

• close

• isclosed

Statement Object

• Wrapper of a string containing a SQL statement

• allows JDBC to decompose the SQL into a set of steps to present to the database via the driver

• the connection object forwards the statement object to the database to obtain a results set object

Statement Class Methods

• executeQuery

• executeUpdate– insert, update, delete

• close

• getResultSet

ResultSet Object

• A container for the rows and columns (a table) acquired as a result of presenting a statement object to the RDBMs using the “executeQuery” statement method

ResultSet Class Methods

• next

• close

• wasNull

• getString

• getBoolean

• getByte

• getShort

ResultSet Class Methods(cont.)

• getInt

• getLong

• getFloat

• getDouble

• getNumeric

• getBytes

• getDate

ResultSet Class Methods (cont.)

• getTime

• getTimeStamp

• getAsciiStream

• getUnicodeStream

• getBinaryStream

• getMetaData

• etc...

JDBC Type Mapping

• Char - String• Varchar - String• Longvarchar - String• Numeric -

java.sql.Numeric• Decimal -

java.sql.Numeric• Bit - boolean

• Tinyint - byte• Smallint = short• Integer - int• Bigint - long• Real - float• Float - double• Double - double• Binary - byte[ ]

JDBC Type Mapping (cont.)

• Varbinary - byte[ ]• Longvarbinary - byte[ ]• Date - java.sql.Date• Time - java.sql.Time• Timestamp -

java.sql.Timestamp