Chapter 2 JDBC

8/11/2019 Chapter 2 JDBC

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JDBC


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The JDBC (Java Database Connectivity) interface is a

pure Java API used to execute SQL Statements.

It provides a set of classes & interfaces that can be

used by developers to write a database applications in

Java.


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Two Tier Access Models

Application Space

Java Application

JDBC DRIVER

SQL stmts Result Set

DATABASE

Your Java Application talks directly to the DB. This is accomplished through

the Use of JDBC DRIVER, which sends commands directly to DB. The results

are sent back from the DB directly to the application.


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Three Tier Access Models

Application Space

Java Application

JDBC DRIVER

SQL stmts Result Set

APPLICATION SERVER

(MIDDLE TIER)

Proprietary Protocol

DATABASE

Your JDBC DRIVER sends commands to a Middle Tier, which in turn sends

commands to the DB. The results of these commands are sent back to

middle tier, which sends them back to the application.


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For Example

Located@ Any PC

HTTPRequests

MicrosoftInternetExplorer

HTML

Located@ Your PC

Apache Tomcat Java ServeletsApp Server

JDBCTuples

Requests

Located Oracle@ DBLab DB Server


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Basic Components of JDBC:

1.JDBC API

2.Driver Manager

3. JDBC Test Suite

4. JDBC-ODBC Bridge


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Type 1 : JDBC-ODBC Bridge , plus ODBC Driver

It provides JDBC access to DB through Open Database Connectivity Drivers (ODBC)

Application Space

Java Application

JDBC - ODBC BRIDGE

SQL COMMANDS Result Set

ODBC DRIVER


DATABASE


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The JDBC type 1 driver, also known as the JDBC-ODBC bridge is a

database driver implementation that employs the ODBC driver to

connect to the database

The driver converts JDBC method calls into ODBC function calls. The

bridge is usually used when there is no pure-Java driver available for a

particular database.

The driver is implemented in the sun.jdbc.odbc.JdbcOdbcDriver classand comes with the Java 2 SDK, Standard Edition.


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Functions

1.Translates query obtained by JDBC into corresponding ODBCquery, which is then handled by the ODBC driver.

2. Sun provides a JDBC-ODBC Bridge driver.

sun.jdbc.odbc.JdbcOdbcDriver. This driver is native code and not

Java, and is closed source.

3. Client -> JDBC Driver -> ODBC Driver -> Database

4. There is some overhead associated with the translation work to

go from JDBC to ODBC.


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Advantages:1. Almost any database for which ODBC driver is installed, can be

accessed.

Disadvantages:1. Performance overhead since the calls have to go through the

JDBC overhead bridge to the ODBC driver, then to the native

database connectivity interface.

2. The ODBC driver needs to be installed on the client machine.

3. Considering the client-side software needed, this might not be

suitable for applets.


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Type 2 : Native API , Partly Java Driver

It converts JDBC commands into DBMS specific calls.

Here Client must have some binary code loaded on its machine.

Application Space

Java Application

Type 2 JDBC DRIVER

SQL COMMANDS Result Set

Native Database Library


DATABASE


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The JDBC type 2 driver, also known as the

Native-API driver is a database driverimplementation that uses the client-side

libraries of the database.

The driver converts JDBC method calls intonative calls of the database API.


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Functions:

1. This type of driver converts JDBC calls into calls to the client

API for that database.

2. Client -> JDBC Driver -> Vendor Client DB Library ->

Database


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Advantage

Better performance than Type 1 since no jdbc to odbc translation is

needed.

Disadvantages

1. The vendor client library needs to be installed on the clientmachine.

2. Cannot be used in internet due the client side software needed.

3. Not all databases give the client side library


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Type 3 : JDBC-Net , Pure Java Driver

These drivers are used for 3-tier solutions. It translates JDBC calls into DB

independent n/w protocol that is sent to a middleware server.

This server translates this DB independent protocol into a DB Specific protocol,

which is sent to a particular DB.

Application Space

Java Application

Type 3 JDBC DRIVER

SQL COMMAND Result Set

MIDDLEWARE

JDBC DRIVER


DATABASE


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The JDBC type 3 driver, also known as the network-protocol

driver is a database driver implementation which makes use

of a middle-tier between the calling program and the

database.

The middle-tier (application server) converts JDBC calls

directly or indirectly into the vendor-specific database

protocol.


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Functions:

1.Follows a three tier communication approach.

2. Can interface to multiple databases - Not vendor specific.

3. The JDBC Client driver written in java communicates with a

middleware-net-server using a database independent protocol, and thenthis net server translates this request into database commands for that

database.

4. Thus the client driver to middleware communication is database

independent.

5. Client -> JDBC Driver -> Middleware-Net Server -> Any Database


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Advantages1. Since the communication between client and the middleware

server is database independent, there is no need for the vendor db

library on the client machine. Also the client to middleware need'nt

be changed for a new database.

2. The Middleware Server (Can be a full fledged J2EE Application

server) can provide typical middleware services like caching

(connections, query results, and so on), load balancing, logging,

auditing etc..

3. eg. for the above include jdbc driver features in Weblogic.

4. Can be used in internet since there is no client side software

needed.

5. At client side a single driver can handle any database.(It worksprovided the middlware supports that database!!)


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Disadvantages

1.Requires database-specific coding to be done in the middle tier.

2. An extra layer added may result in a time-bottleneck. But

typically this is overcome by providing efficient middleware

services described above.


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Type 4 : Native Protocol , Pure Java Driver

It Communicates directly with the DB.

They do this by converting JDBC commands directly into the DB Engines Native

Protocol.

Application Space

Java Application

Type 4 JDBC DRIVER

SQL COMMAND Result Set

Using Proprietary Protocol Using Proprietary Protocol

DATABASE


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The JDBC type 4 driver, also known as the native-protocol driver

is a database driver implementation that converts JDBC calls

directly into the vendor-specific database protocol.


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Functions

1. Type 4 drivers are entirely written in Java that communicates directly

with a vendor's database through socket connections. No

translation or middleware layers, are required, improving performance.

2. The driver converts JDBC calls into the vendor-specific database

protocol so that client applications can communicate directly with thedatabase server.

3. Completely implemented in Java to achieve platform independence.

4. e.g include the widely used Oracle thin driver - oracle.jdbc.driver.OracleDriver which connect to jdbc:oracle:thin URL format.

5. Client Machine -> Native protocol JDBC Driver -> Database server


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Advantages

These drivers don't translate the requests into db request toODBC or pass it to client api for the db, nor do they need a

middleware layer for request indirection.

Thus the performance is considerably improved.

DisadvantageAt client side, a separate driver is needed for each database.


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Java

applicationJDBC-API

JDBC-

Driver manager

Native JDBC-

Protocol driver Net-driver

DB-

Middleware

JDBC-ODBC Native

bridge API-driver

ODBC Client library

Client library

JDBC Drivers


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1. Establish a connection

import java.sql.*;

Load the specific driver

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

Dynamically loads a driver class & registers it to aDriverManager

Make the connection

Connection con = DriverManager.getConnection("jdbc:odbc:dsn", username, passwd);

Establishes connection to database by obtaininga Connectionobject


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2.Create JDBC Statement

Statement stmt = con.createStatement() ; Creates a Statement object for sending SQL statements to

the database


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3. Executes SQL Commands

String tbl = "Create table user (Name VARCHAR(32),Age Integer)";

stmt.executeUpdate(tbl);

String intbl = "Insert into user values(abc,30)";

stmt.executeUpdate(intbl);


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4. Process Results

String query = "select * from user";

ResultSetrs = Stmt.executeQuery(query);

while (rs.next()) {

String name = rs.getString("NAME");

int marks = rs.getInt(Age");

}


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5. Close Connections

Stmt.close()

Con.close()

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Chapter 2 JDBC