JDBC.ppt

JDBC

2

JDBC

• Lets programmers connect to a database, query it or update through a Java application.

• JDBC library is implemented in java.sql package.

Java Database Connectivity (JDBC)

DatabaseDatabaseJDBCdriver

Java app Database

JDBC calls

Database commands

JDBCdriver

JDBCdriver

• JDBC loads a driver

• Driver talks to a particular database• An application can work with several databases by using all

corresponding drivers

A driver is a program that converts the Java method calls to the

corresponding method calls understandable by the database in use.

JDBC Driver

• A driver is a program that converts the Java method

calls to the corresponding method calls understandable

by the database in use.

JDBC Architecture

Database

JDBC Driver Manager

Java Application

JDBC API

JDBC Driver API

Vendor Specific JDBC Driver

Vendor SpecificODBC Driver

JDBC-ODBCBridge

Database

6

JDBC vendor specific Architecture

Java Application

JDBC

Oracle

DB2

MySQL

Oracle Driver

DB2Driver

MySQL Driver

Network

7

Types of JDBC(Drivers)

• JDBC-ODBC Bridge (Type 1= Bridge)

• Native-API partly Java Driver (Type 2= Native)

• Net-Protocol All-Java Driver (Type 3= Middleware )

• Native Protocol All-Java Driver (Type 4= Pure)

Type 1 JDBC Driver

JDBC-ODBC Bridge driver

• ODBC API is written C language & makes use of pointers and

the constructs that java does not support, java program can not

directly communicate with ODBCAPI.

• The Type 1 driver translates all JDBC calls into ODBC calls

and sends them to the ODBC driver.

Type 1 JDBC Driver

Advantage

• Access to almost any database, since the

database's ODBC drivers are already

available.

Disadvantages

1.Since the Bridge driver is not written fully

in Java, Type 1 drivers are not portable.

2.Due to bridge, slowest of all driver types.

3.Not good for the Web.

Type 2 JDBC Driver

Native-API/partly Java driver

• Converts JDBC calls into database-specific calls.

• This driver is specific to a particular database.

• Example: Oracle will have oracle native api.

Type 2 JDBC Driver• Advantage

1. Better performance than the JDBC-ODBC Bridge

2. it uses Native api which is Database specific.

• Disadvantage

1. Native API must be installed in the Client System hence cannot be used for the

Internet.

2. It’s not written in Java Language which forms a portability issue.

3. If we change the Database we have to change the native api as it is specific to a

database

Type 3 JDBC Driver

All Java/Net-protocol driver

• Type 3 database requests are

passed through the network to

the middle-tier server.

• The middle-tier then translates

the request to the database.

Type 3 JDBC Driver• Advantage

1. This driver is server-based, so there is no need for any vendor

database library to be present on client machines.

2. Fully written in Java and hence Portable.

3. It is suitable for the web.

4. The net protocol can be designed to make the client JDBC

driver very small and fast to load.

Disadvantage

• It requires another server application to install and maintain.

Type 4 JDBC Driver

Native-protocol/all-Java driver

The Type 4 uses java networking libraries to communicate

directly with the database server.

Type 4 JDBC Driver• Advantage

1. 1. Completely written in Java to achieve platform independence

2. It is most suitable for the web.

3. Number of translation layers is very less i.e. they don't have to translate

database requests to ODBC or a native connectivity interface or to pass

the request on to another server.

Disadvantage

With type 4 drivers, the user needs a different driver for each database.

Seven Basic Steps in Using JDBC

1. Load the driver

2. Define the Connection URL

3. Establish the Connection

4. Create a Statement object

5. Execute a query

6. Process the results

7. Close the connection

JDBC: Details of Process: Step 11. Loading the driverpublic static Class forName (String className)

throws ClassNotFoundException Example:try { Class.forName("sun.jdbc.odbc.JdbcOdbcDriver"); //Class.forName("oracle.jdbc.driver.OracleDriver");

}catch(ClassNotFoundException e) { }

JDBC: Details of Process : Step 2

2. Define the Connection URL

String URL= "jdbc:odbc:test“ (test is DSN)

JDBC: Details of Process : Step 3

3. Establish the Connection

public static Connection getConnection (String url,

String user, String password) throws SQLException

Connection con =

DriverManager.getConnection(URL);

JDBC: Details of Process : Step 4

4. Create a Statementpublic Statement createStatement() throws

SQLException

Statement stat = con.createStatement();

JDBC: Details of Process : Step 5

5. Execute a Query

public ResultSet executeQuery (String sql) throws

SQLException

String query = "SELECT * FROM sometable";

ResultSet rs= stat.executeQuery(query);

JDBC: Details of Process : Step 6

6. Process the Resultwhile (rs.next()) { s.o.p(rs.getString(2); }

– Values of second column are retrieved using getString()

method.

JDBC: Details of Process : Step 7

7. Close the Connection

con.close();

JDBC Class Usage

DriverManager

Driver

Connection

Statement

ResultSet

The Driver Manager

• The driver manager sits between the JDBC application and one

or more JDBC drivers.

• DriverManager establishes connection & returns connection

object.

• Connection con = DriverManager.getConnection(URL);

Making a Connection

• There are several getConnection() methods on DriverManager with

different argument lists.

• One of them is:

static Connection getConnection(String url)

• If you are using a non-default DB account and password, use instead:

static Connection getConnection(String url,

String username, String password)

Statement

• A Statement object is used for executing a SQL

statement and obtaining the results produced by it.

Statement Methods

ResultSet executeQuery(String) – Execute a SQL statement that returns a single ResultSet.

int executeUpdate(String) – Execute a SQL INSERT, UPDATE or DELETE

statement.

– Returns the number of rows changed.

boolean execute(String) – Execute a SQL statement that may return multiple

results.

ResultSet

• A ResultSet provides access to a table of data generated by

executing a Statement.

• Only one ResultSet per Statement can be open at once.

• The table rows are retrieved in sequence.

• A ResultSet maintains a cursor pointing to its current row of

data.

• The 'next' method moves the cursor to the next row.

ResultSet Methods

• boolean next() – activates the next row

– the first call to next() activates the first row

– returns false if there are no more rows

• void close() – disposes of the ResultSet

ResultSet Methods

• Type getType(int columnIndex)

– returns the given field as the given type

– fields indexed starting at 1 (not 0)

• Type getType(String columnName)

– same, but uses name of field

• int findColumn(String columnName)

– looks up column index given column name

ResultSet Methods

• String getString(int columnIndex)

• boolean getBoolean(int columnIndex)

• byte getByte(int columnIndex)

• short getShort(int columnIndex)

• int getInt(int columnIndex)

• long getLong(int columnIndex)

• float getFloat(int columnIndex)

• double getDouble(int columnIndex)

ResultSet Methods

• String getString(String columnName)

• boolean getBoolean(String columnName)

• byte getByte(String columnName)

• short getShort(String columnName)

• int getInt(String columnName)

• long getLong(String columnName)

• float getFloat(String columnName)

• double getDouble(String columnName)

PreparedStatement

• It has set of methods that can be used for sending queries with

input parameters.

• PreparedStatement stat = con. PreparedStatement(“ Select

* from publication where pub_id=?”)

• The symbol “ ? ” is replaced by input parameter at run time.

Simple JDBC exampleimport java.sql.*;public class JdbcExample{public static void main(String[] args){ int i; Connection con = null; // register jdbc driver try { Class.forName("sun.jdbc.odbc.JdbcOdbcDriver"); } catch(ClassNotFoundException e) { System.out.println(e); }

// connect to DB

try{

con = DriverManager.getConnection("jdbc:odbc:my_database");

} catch(SQLException se) {

System.out.println(se);

}

System.out.println("connection is successful!!!");

try{

String selectSQL = "select ID, NAME, ADDRESS from

tb_address";

Statement stat = conn.createStatement();

ResultSet rs = stmt.executeQuery(selectSQL);

while(rs.next()){

System.out.println("ID: " + rs.getString(1) + " NAME: " +

rs.getString(2) + " ADDRESS:" +rs.getString(3));

}

stat.close();

} catch(SQLException se) {

System.out.println(se);

}

}

}