JDBC

In establishing a connection is to have the appropriate driver connect to the DBMS. The following line of code illustrates the general idea:

E.g.

String url = “jdbc:odbc:Fred”;

Connection con = DriverManager.getConnection(url, “Fernanda”, “J8”);

It is used to create an instance of a driver and register it with the DriverManager. When you have loaded a driver, it is available for making a connection with a DBMS.

Loading the driver or drivers you want to use is very simple and involves just one line of code. If, for example, you want to use the JDBC-ODBC Bridge driver, the following code will load it:

Eg.

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

Your driver documentation will give you the class name to use. For instance, if the class name is jdbc.DriverXYZ , you would load the driver with the following line of code:

E.g.

Class.forName(”jdbc.DriverXYZ”);

This involves two steps:

(1) loading the driver and

(2) making the connection.

A URL string

–>getConnection

–>DriverManager

–>Driver

–>Connection

–>Statement

–>executeQuery

–>ResultSet.

There are 8 packages: java.sql.Driver, Connection,Statement, PreparedStatement, CallableStatement, ResultSet, ResultSetMetaData, DatabaseMetaData.

1.Create an instance of a JDBC driver or load JDBC drivers through jdbc.drivers;

2. Register a driver;

3. Specify a database;

4. Open a database connection;

5. Submit a query;

6. Receive results.

The JDBC Driver interface provides vendor-specific implementations of the abstract classes provided by the JDBC API. Each vendors driver must provide implementations of the java.sql.Connection,Statement,PreparedStatement, CallableStatement, ResultSet and Driver.

One implementation interface for database manufacturers, the other implementation interface for application and applet writers.

Serialization is the process of writing the state of an object to a byte stream.

Deserialization is the process of restoring these objects.

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Another new feature in the JDBC 2.0 API is the ability to update rows in a result set using methods in the Java programming language rather than having to send an SQL command. But before you can take advantage of this capability, you need to create a ResultSet object that is updatable. In order to do this, you supply the ResultSet constant CONCUR_UPDATABLE to the createStatement method.

E.g.

Connection con = DriverManager.getConnection(”jdbc:mySubprotocol:mySubName”);

Statement stmt = con.createStatement(ResultSet.TYPE_SCROLL_SENSITIVE,

ResultSet.CONCUR_UPDATABLE);

ResultSet uprs = (”SELECT COF_NAME, PRICE FROM COFFEES”);

JDBC is a layer of abstraction that allows users to choose between databases. It allows you to change to a different database engine and to write to a single API. JDBC allows you to write database applications in Java without having to concern yourself with the underlying details of a particular database.

The first step is to create a CallableStatement object. As with Statement an and PreparedStatement objects, this is done with an open Connection object. A CallableStatement object contains a call to a stored procedure;

E.g.

CallableStatement cs = con.prepareCall(”{call SHOW_SUPPLIERS}”);

ResultSet rs = cs.executeQuery();

1.Statement (use createStatement method)

2. Prepared Statement (Use prepareStatement method) and

3. Callable Statement (Use prepareCall)

A Statement object is what sends your SQL statement to the DBMS. You simply create a Statement object and then execute it, supplying the appropriate execute method with the SQL statement you want to send. For a SELECT statement, the method to use is executeQuery. For statements that create or modify tables, the method to use is executeUpdate. E.g. It takes an instance of an active connection to create a Statement object. In the following example, we use our Connection object con to create the Statement object stmt :

Statement stmt = con.createStatement();

First JDBC returns results in a ResultSet object, so we need to declare an instance of the class ResultSet to hold our results. The following code demonstrates declaring the ResultSet object rs.

E.g.

ResultSet rs = stmt.executeQuery(”SELECT COF_NAME, PRICE FROM COFFEES”);

Second:

String s = rs.getString(”COF_NAME”);

The method getString is invoked on the ResultSet object rs , so getString will retrieve (get) the value stored in the column COF_NAME in the current row of rs