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Remote Database Access

User DatabaseClient APIDatabase

ServerDatabase

VC++,VB

Java programsODBC

or JDBCFor different databases, database client need not talk in different ways.

Database client talks through ODBC API or JDBC API and the API talks tothe database server.

Database Server listens to a port and responds only to SQL commandspassed by ODBC or JDBC.

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ODBC is a C language API, not a Java API. Java isobject oriented and C is not.C uses pointers and dangerous programmingconstructs that Java does not support.

ODBC drivers must be installed on client machines.i.e.,the Applet that has to access to databasesneeds a driver in the client side. If the driver is aODBC driver, the applet does not execute.

A Pure Java solution allows JDBC drivers to beautomatically installed along with the applet.

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There are four types of drivers: JDBC Type 1 Driver -- JDBC/ODBC Bridge drivers

ODBC (Open DataBase Connectivity) is a standardsoftware API designed to be independent of specificprogramming languagesSun provides a JDBC/ODBC implementation

JDBC Type 2 Driver -- use platform-specific APIsfor data access

JDBC Type 3 Driver -- 100% Java, use a net protocolto access a remote listener and map calls intovendor-specific calls

JDBC Type 4 Driver -- 100% JavaMost efficient of all driver types

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This driver uses Microsofts OD C driver to

communicate with Database servers.It is an attempt to use the existing ODBC drivers.It is implemented using C and Java and must bepreinstalled on a client computer before it can be

used.

DatabaseClient

JDBC ODBCBridge

OracleServer

DB2

SQL Server

ODBC

ODBC

ODBC JDBC

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These drivers talks to database servers using Call LevelInterface.There are certain C language libraries for connecting toOracle , DB2 or any other database.This driver will use those C language libraries for speakingwith the particular database.

These drivers are implemented in a combination of binarycode in Java and must be installed on a client machine.

DatabaseClient

Native partly Java

driverDatabase

Server

Vendor specific

protocol

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This driver translates JDBC calls into a DBMS- independent netprotocol HTTP) which is then translated to a DBMS protocol by aserver.This net server middleware is able to connect its pure Java clientsto many different databases.The specific protocol used depends on the vendor.

This is the best solution for applets which wants to talk todatabase directly without using servlets.

Database accessserver

Pure Java driver

DatabaseClient

OracleServer

DB2 server

SQL server

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This driver category consists of pure Javadriver.This Driver uses vendor specific databaseprotocol of the database server directly.

DatabaseClient

Pure Java

driver

Database

Server

Vendor specific

protocol

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JDBC

Type IBridge

Type IINative

Type III

Middleware

Type IVPure

ODBC ODBCDriver

CLI (.lib)

Middleware

Server

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import JDBC packages (java.sql.*)Load the JDBC drivers Class.forName (oracle.jdbc.driver.OracleDriver )

Connect to the database Connection conn =

DriverManager.getConnection(url,userid,passwd) jdbc:oracle:drivertype@database

Interact with DB using JDBCDisconnect from DB

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1. Loading the DriverClass.forName (sun.jdbc.odbc.JdbcOdbcDriver );

2. Constructing URL for the database.

String url = jdbc:odbc:dsn ;

3. Getting the Connection.Connection

con=DriverManager.getConnection(url,userid,pwd);

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4. Creating the statementStatement stmt=con.createStatement();

5. Execute the corresponding SQL statements.ResultSet rs=stmt.executeQuery (select * fromTable where empno =5);

6. Reading the values from the Resultset.while(rs.next()){String s=rs.getString (empname ); double sal=rs.getDouble (empsal );

}

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executeQuery()used to execute only SQL query statements (DQL)Returns a ResultSet object which can interact withResulted Buffer data in database.

executeUpdate() used to execute either insert, update or deletestatements(DML)Returns no of rows effected by the operation.

execute()

used to execute any type of statements likecreate, alter, drop (DDL)Returns true if command executed successfully,otherwise returns false.

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boolean hasresults=stmt.execute(selectstatement);

if(hasresults){ResultSet rs=stmt.getResultSet( );

String str=rs.getString(empnam); ..

}

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Registered Users Details

User NamePasswordEMail IDPhone Number

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while(rs.next()){

%>

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Retrieve Data about Result is done through ResultSetMetaData class object.We can creat it by calling getMetaData() method of ResultSet.

getColumnCount() returns no of columns in resultset according to the no ofcolumns selected in select query.getColumnName(int colnumber) returns the name of the columngetColumnType(int colnumber) returns the type of the column

Ex:ResultSet rs = st.executeQuery(select * from loginusers ); ResultSetMetaData rsmd = rs.getMetaData();int count = rsmd.getColumnCount();for( int i=0; i

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import java.sql.*;import javax.sql.*;import javax.sql.rowset.*;public class JDBCRowSetExample {

public static void main(String[] args) throws Exception {Class.forName (com.mysql.jdbc.Driver ); JdbcRowSet rs = new JdbcRowSetImpl();

rs.setUrl ( jdbc:mysql://localhost /test); rs.setUsername (root); rs.setPassword (root); rs.setCommand (select * from loginusers ); rs.execute();System.out.println (username \t password);

while (rs.next()) {System.out.print(rs.getString(1));System.out.println (\t" + rs.getString(2));

}

}

}

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JDBC24

JDBC Type Java Type BIT boolean TINYINT byte SMALLINT short INTEGER int BIGINT long REAL float FLOAT double DOUBLE BINARY byte[] VARBINARY LONGVARBINARY

CHAR String VARCHAR LONGVARCHAR

JDBC Type Java Type NUMERIC BigDecimal DECIMAL DATE java.sql.Date TIME java.sql.Timestamp TIMESTAMP CLOB Clob * BLOB Blob * ARRAY Array * DISTINCT mapping of underlying type STRUCT Struct * REF Ref * JAVA_OBJECT underlying Java class

*SQL3 data type supported in JDBC 2.0

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Frameworks: Provides abstraction of a particular concept Defines how these abstractions work together to

solve a problem Framework components are reusable Organizes patterns at higher level Provides generic behaviour (many different

applications can be built with the use of the same

application)

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View

Model

Controller

Change notification

Query state

View selection

User input

Change state

events

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Web Browser

JSP

JavaBeanServlet

Demo Model 2 example

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Created in 2000 by Craig R. McClanahan Donated to ASF in 2000 Most popular release: 1.3.8 Latest stable release is 2.3.4.1 1.x will be around - there is newdevelopment, great community, many applications are developed in 1.x

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The Apache Struts web framework is for creating Java webapplications.

Web applications based on JSP Pages sometimes commingledatabase code, page design code, and control flow code.In practice, we find that unless these concerns are separated,larger applications become difficult to maintain.One way to separate the logics is to use a Model-View-Controller (MVC) architecture.The Model represents the business or database code,The View represents the page design code.The Controller represents the navigational code.The Struts framework is designed to help developers createweb applications that utilize a MVC architecture.

The framework provides three key components: A "request" handler provided by the application developer that ismapped to a standard URI.

A "response" handler that transfers control to another resource whichcompletes the response.

A tag library that helps developers create interactive form-basedapplications with server pages.

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The controller servlet recieves all the requests.It searches the properties file for appropriate requesthandler, depending upon the request URL.Invokes the request handler returned by step2 andpasses control to it.The request handler handles the request, includingbusiness logic methods invocation, form validationetc.,The request handler returns the name of the view tobe displayed.The controller servlet dispatches the request to theview returned by the request handler.View is sent as a response to the user.

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Model-View-Controller (MVC) frameworkUsed for constructing web applications basedServlets and JSP technologies Struts application is a genuine Web application that

should be able to run on any Sevlet containerincluding all J2EE compliant App serversPattern oriented Singleton, composition view, delegate Easy to use and learnIncludes custom tag libraries

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Takes much of the complexity out of building yourown MVC frameworkEncourages good design practice and modelingEasy to learn and use

Feature-ricMany supported 3rd-party toolsFlexible and extensibleLarge user communityStable and matureOpen source

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Integrates well with J2EEGood custom tags supportEasy to retain input form state

Unified error handling programmatically anddeclarativelyIntegration with Tiles frameworkClear delineation of responsibility makes long

term maintenance easier (more modular)

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Central controller (ActionServlet) mediatesapplication flow and delegates to appropriatehandler called ActionAction Handlers can use model componentsModel encapsulates business logic or stateControl forwarded back through theController to the appropriate View

The forwarding can be determined by consulting aset of mappings in configuration file

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3 Major Components in Struts Servlet controller (Controller) Java Server Pages or any other presentation

technology (View) Application Business Logic in the form of whatever

suits the application (Model)Struts is focused on Controller Struts is Model and View independent

Struts can use any Model and View technologies

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A) The web application is deployed. The server readsthe deployment descriptor file(web.xml). Loads theActionServlet class on start.B) creates an object of ActionServlet.C) set the init- parameter config with its parameter. D) user gives request to the web application on webbrowser. Browser tries to load register.jspE) user enters username and password and press thesubmit button.

F) form invokes the action-URL and send request toserver with the action / reg.do . G) control transfer to the servlet-mapping tag inweb.xml and ActionServlet traps the request-data.

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H) ActionServlet reads the entries of struts-config.xml file.I) It locates the action / reg in actionmappingtag.

J) It reads name of Action Form.K) from form-beans tag it locates the form-beanclass and loads that class.L) object of form bean is populated and theproperty values in register.jsp transferred andstored in form bean object using setter methods.M) ActionServlet reads the Action sub class namein struts-config.xml and loads the sub class.

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N) the object of Action sub class and itsexecute() method is called and executed.O) according the values filled in jsp it desides O-a) ActionForward object is created with ok

parameter. O-b) ActionForward object is created with fail

parameter.P) ActionServlet reads the forward tags in actiontag and find the filename to forward the control.Q) either success.jsp/failure.jsp is displayed as aresult.