18CSC311J Web Design and Development UNIT-3

Web Design and Development,
UNIT-3,
SRM University,
VI Semester,
Regulation 2018

1. 18CSC311J WEB DESIGN AND DEVELOPMENT 2023-24 EVEN SEMESTER REGULATION 2018 Prepared by Dr.M.Sivakumar AP,NWC, SRMIST, KTR DEPARTMENT OF NETWORKING AND COMMUNICATIONS Prepared by Dr.M.Sivakumar 1

2. 18CSC311J WEB DESIGN AND DEVELOPMENT UNIT III Overview of JSP Servlets: Java Servlet Architecture- Servlet Life Cycle- GET and POST Method Creating Dynamic Web pages using JSP JSP Standard Tag Library (JSTL) Introduction to MySQL JDBC Drivers Understanding JDBC-ODBC Management Resultset , Statements Prepared Statement, Callable Statement

3. Installing and Configuring Apache Tomcat Web Server Install JDK Download from http://tomcat.apache.org/ Run the installation file Remember port Check the installation by typing http://localhost:8080/ in the browser Move web pages to D:\Program Files\Apache Software Foundation\Tomcat 7.0\ webapps \ folder

4. Servlets Java Servlet Architecture Servlet Life Cycle Form GET and POST actions Session Handling Understanding Cookies

5. Servlets Servlet is a Java Class File or a Java Program that runs on a Web server Servlets are used for creating dynamic web applications by extending the capability of a server The   javax.servlet  and  javax.servlet.http   are packages which provides interfaces and classes for creating servlets  All the servlets must implement the  Servlet  interface, which defines life-cycle methods

6. Java Servlet Architecture

7. Servlet Life Cycle Servlet lifecycle describes how the servlet container manages the servlet object init ()  :- Initialization of servlet instance using the init() method. service()  :- Servicing a client request using the service() method. destroy()  :- Destroying a servlet instance using the destroy() method. 7

8. Servlet Life Cycle

9. Servlet Syntax public class ServletDemo extends HttpServlet { public void init () { /* used to initialize resources */ } public void service() { /* used to fulfill client request */ } public void destroy() { /* Release the resources */ } }

10. Servlet Example1 public class HelloWorld extends GenericServlet { public void service ( ServletRequest request, ServletResponse response ) throws IOException { response.setContentType ("text/html"); PrintWriter out = response.getWriter (); out.println ("<h1> Hello World </h1>"); out.close (); } }

11. Servlet Example2 public class HelloWorld extends HttpServlet { public void doGet ( HttpServletRequest request, HttpServletResponse response ) throws IOException { response.setContentType ("text/html"); PrintWriter out = response.getWriter (); out.println ("<h1> Hello World </h1>"); out.close (); } }

12. Servlet Container It is known as servlet engine which manages Java Servlet components on top of a web server to the request send by the client. Servlet Container provides the following services : It manages the servlet life cycle The resources like servlets, JSP pages and HTML files are managed by servlet container It appends session ID to the URL path to maintain session . Provides security service It loads a servlet class from network services, file systems like remote file system and local file system

13. How web container handles the servlet request ? M aps the request with the servlet in the web.xm l file C reates request and response objects for this request C alls the service method on the thread The public service method internally calls the protected service method The protected service method calls the doGet method depending on the type of request. The doGet method generates the response and it is passed to the client. After sending the response, the web container deletes the request and response objects. The thread is contained in the thread pool or deleted depends on the server implementation.

14. How Servlet Works?

15. How Servlet Works? When the web server (e.g. Apache Tomcat) starts up, the servlet container deploy and loads all the servlets Once the servlet is loaded, the servlet container creates the instance of servlet class. For each instantiated servlet, its init () method is invoked . Client (user browser) sends an Http request to web server on a certain port. Each time the web server receives a request, the servlet container creates HttpServletRequest and HttpServletResponse objects . When servlet container shuts down, it unloads all the servlets and calls destroy() method for each initialized servlets.

16. H ierarchy of Packages java.lang.Object |_ extended by javax.servlet .GenericServlet |_ extended by javax.servlet.http .HttpServlet

17. Interfaces in javax.servlet package Servlet ServletRequest ServletResponse ServletConfig ServletContext SingleThreadModel RequestDispatcher ServletRequestListener ServletRequestAttributeListener ServletContextListener ServletContextAttributeListener Filter FilterConfig FilterChain Classes in javax.servlet package GenericServlet ServletInputStream ServletOutputStream ServletException ServletRequestWrapper ServletRequestEvent ServletResponseWrapper ServletContextEvent ServletRequestAttributeEvent ServletContextAttributeEvent UnavailableException

18. Interfaces in javax.servlet.http package HttpSession HttpServletRequest HttpServletResponse HttpSessionAttributeListener HttpSessionListener HttpSessionBindingListener HttpSessionActivationListener HttpSessionContext Classes in javax.servlet.http package HttpServlet Cookie HttpSessionEvent HttpSessionBindingEvent HttpServletRequestWrapper HttpServletResponseWrapper HttpUtils

19. Form GET Actions <!DOCTYPE html> < html > < head > < title> doGet Example</title > </ head> < body> <form name=" myform " action =“ MyServlet " method=“get"> Enter Name:<input type="text" name=" uname ">< br >< br > Enter Age:< input type =“text" name =“ uage ">< br >< br > <input type="submit" value="submit"> </form> </ body> </html>

20. Form GET Actions import javax.servlet .*; import javax.servlet.http .*; public class MyServlet extends HttpServlet { public void doGet ( HttpServletRequest request, HttpServletResponse response) throws IOException { try { response.setContentType ("text/html"); PrintWriter out = response.getWriter (); String name= request.getParameter (" uname "); String age= request.getParameter (“ uage "); out.println ("<h3>Welcome to doGet Method</h3> "); out.println ("< br >Name:"+name); out.println ("< br >Age:"+age); out.close (); } catch(Exception e) { System.out.println (e); } } } 20

21. Form POST Actions <!DOCTYPE html> <html> <head> <title> doPost Example</title> </head> <body> <form name=" myform " action=“ MyServlet " method=“post"> Enter Name:<input type="text" name=" uname ">< br >< br > Enter Password:<input type="password" name=" pwd ">< br >< br > <input type="submit" value="submit"> </form> </body> </html>

22. Form POST Actions import javax.servlet .*; import javax.servlet.http .*; public class MySerlvet extends HttpServlet { public void doPost ( HttpServletRequest request, HttpServletResponse response) throws IOException { try { response.setContentType ("text/html"); PrintWriter out = response.getWriter (); String name= request.getParameter (" uname "); String pwd = request.getParameter (" pwd "); out.println ("<h3>Welcome to doPost Method</h3> "); out.println ("< br >Name:"+name); out.println ("< br >Password:"+ pwd ); out.close (); } catch(Exception e) { System.out.println (e); } } } 22

23. JSP Java Server Pages (JSP) is a server-side programming technology that enables the creation of dynamic, platform-independent method for building Web-based applications . JSP have access to the entire family of Java APIs, including the JDBC API to access enterprise databases . JSP technology enables rapid development of web-based applications JSP pages are easier to maintain than a Servlet JSP pages are opposite of Servlets as a servlet adds HTML code inside Java code, while JSP adds Java code inside HTML using JSP tags

24. JSP Architecture 24

25. JSP Life Cycle 25

26. JSP Syntax JSP  Scriptlet Scriptlet tag allows to write Java code into JSP file JSP container moves statements in _ jspservice () method while generating servlet from jsp Syntax:   <% ... %> JSP Declaration Tag for declaring variables, methods and classes declaration is made outside the service method Syntax: <%! Datatype varname ; %> JSP Expression evaluates the expression placed in it <%= ... %> JSP Directives   <%@ ... %> 26

27. JSP Scriptlet Example <!DOCTYPE html> < html> <head>< title>JSP Example</ title></head> <body > <% out.println (“Hello World”); %> </ body> </html>

28. JSP Declaration Example <!DOCTYPE html> < html> <head>< title>JSP Example</ title></head> <body > <%! int num =10; %> <% out.println (“This number is ”+ num ); %> </ body> </html>

29. JSP Expression Example date.jsp <html> <body> Hello! The time is now <%= new java.util.Date () %> </body> </html> 29

30. JSP Implicit Objects request response session exception application PageContext Page

31. Directives The  jsp directives  are messages that tells the web container how to translate a JSP page into the corresponding servlet . There are three types of directives: page directive <%@ page attribute="value" %>  include directive <%@ include file=" resourceName " %> taglib directive <%@  taglib   uri =" uriofthetaglibrary " prefix=" prefixoftaglibrary " %> 31

32. page directive Attributes of JSP page directive import contentType Session errorPage Language info buffer isThreadSafe pageEncoding isErrorPage 32

33. page directive Page Encoding Directive : Sets the character encoding for the JSP page. <%@ page pageEncoding ="UTF-8" %> Import Directive : Imports Java classes or packages for use in the JSP page. <%@ page import=" java.util .*, java.io.*" %> Session Directive : Specifies whether the JSP page participates in HTTP session tracking. <%@ page session="true" %> Error Page Directive : Specifies a JSP page to handle exceptions thrown by the current page. <%@ page errorPage ="error.jsp" %>

34. page directive Language Directive : Specifies the scripting language used in the JSP page. <%@ page language="java" %> Content Type Directive : Sets the content type of the response generated by the JSP page. <%@ page contentType ="text/html" %> Buffer Directive : Controls the buffering behavior of the JSP page. <%@ page buffer="8kb" %> IsThreadSafe Directive : Indicates whether the generated servlet is thread-safe. <%@ page isThreadSafe ="true" %>

35. page directive Info Directive : Provides information about the JSP page <%@ page info="This is my JSP page" %> IsErrorPage Directive : Specifies whether the JSP page is intended to be used as an error page <%@ page isErrorPage ="true" %>

36. page directive <!DOCTYPE html> <html> <head> <title>import directive Demo</title> <head> <body> <%@ page import=" java.util.Date " %> Today is: <%= new Date() %> </body> </html>

37. <%-- Text Content Type --%> <% out.println ("Content-Type: text/plain"); out.println ("Hello, this is a plain text response."); %> <%-- HTML Content Type --%> <% response.setContentType ("text/html; charset =UTF-8"); out.println ("< br >< br >Content-Type: text/html"); out.println ("<p>Hello, this is an HTML response.</p>"); %> <%-- JSON Content Type --%> <% response.setContentType ("application/ json "); out.println ("< br >< br >Content-Type: application/ json "); out.println ("{\"message\": \"This is a JSON response.\"}"); %> setContentType

38. <%-- XML Content Type --%> <% response.setContentType ("application/xml"); out.println ("< br >< br >Content-Type: application/xml"); out.println ("<message>This is an XML response.</message>"); %> <%-- PDF Content Type --%> <% response.setContentType ("application/ pdf "); out.println ("< br >< br >Content-Type: application/ pdf "); // Code to generate PDF goes here (not included in this example) %> <%-- CSV Content Type --%> <% response.setContentType ("text/ csv "); out.println ("< br >< br >Content-Type: text/ csv "); out.println ("Name, Age, Country"); out.println ("John Doe, 30, USA"); out.println ("Jane Smith, 25, Canada"); %>

39. Include directive The include directive in JSP is used to include the contents of another resource (such as a JSP file, HTML file, or servlet ) in the current JSP page at translation time. Syntax: <%@ include file=“value" %> Attributes file virtual flush errorPage

40. Include directive attributes file : This attribute specifies the path of the resource to be included. It can be a relative or absolute path. <%@ include file="header.jsp" %> virtual : This attribute is an alternative to the file attribute. It specifies the path of the resource to be included relative to the root of the web application. <%@ include virtual="/WEB-INF/include/footer.jsp" %> flush : This optional attribute specifies whether the output buffer should be flushed before including the content. <%@ include file="header.jsp" flush="false" %> errorPage : This attribute specifies the JSP page that should handle any errors that occur during the include operation. If an error occurs, the request is forwarded to the specified error page. <%@ include file="header.jsp" errorPage ="error.jsp" %>

41. include directive example header.html <html> <head> <title> K.Ramakrishnan College of Technology</title> </head> <body> <h1> K.Ramakrishnan College of Technology</h1> footer.html </body> </html> main.jsp <%@ include file="header.html" %> <p>Main content</p> <%@ include file="footer.html" %> 41

42. taglib directive The JavaServer Pages API allows you to define custom JSP tags that look like HTML or XML tags and a tag library is a set of user-defined tags that implement custom behavior . Syntax: <%@  taglib   uri =" uriofthetaglibrary " prefix=" prefixoftaglibrary " %>   uri : This attribute specifies the unique identifier or URI (Uniform Resource Identifier) of the custom tag library. prefix : This attribute specifies the prefix that you will use to reference the custom tags from the tag library within your JSP page. 42

43. taglib example <%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %> uri ="http://java.sun.com/jsp/jstl/core" This specifies the URI of the JSTL ( JavaServer Pages Standard Tag Library) Core tag library. This URI uniquely identifies the JSTL Core library. prefix="c“ This specifies the prefix c that will be used to reference tags from the JSTL Core library within the JSP page. For example, if you want to use the <c:forEach> tag from the JSTL Core library, you would use c:forEach syntax in your JSP code.

44. JSP Action Tags 44 JSP ( JavaServer Pages) action tags are XML-based tags used within JSP pages to provide dynamic behavior, control flow, and access to server-side resources. These action tags are executed when the JSP page is translated into a servlet .

45. JSP Action Tags JSP Action Tags Description jsp:forward forwards the request and response to another resource. jsp:include includes another resource. jsp:useBean creates or locates bean object. jsp:setProperty sets the value of property in bean object. jsp:getProperty prints the value of property of the bean. jsp:plugin embeds another components such as applet. jsp:params sets the parameter value. It is used in forward and include mostly. jsp:fallback can be used to print the message if plugin is working. It is used in jsp:plugin . 45

46. jsp:forward & jsp:param 46 page1.jsp <html> <body> <h2>this is index page</h2> < jsp:forward page="page2.jsp" > < jsp:param name=“email" value=“[email protected]" /> </ jsp:forward > </body> </html> page2.jsp <html> <body> <%= request.getParameter (“email") %> </body> </html>

47. jsp:include <html> <body> <h2>this is index page</h2> < jsp:include page=“page2.jsp" /> <h2>end section of index page</h2> </body> </html> 47

48. JSTL The JSP Standard Tag Library (JSTL) represents a set of tags to simplify the JSP development. Advantage of JSTL Fast Development  JSTL provides many tags that simplifies the JSP. Code Reusability  We can use the JSTL tags in various pages. No need to use scriptlet tag < %@ taglib   uri =“ “ prefix=“ “ % >    48

49. JSTL Tag Types Core Tags Formatting Tags XML Tags SQL Tags 49

50. Core Tags Tags Description c:out It display the result of an expression c:import It Retrives relative or an absolute URL and display the contents to either a String in ' var ', a Reader in ' varReader ' or the page. c:set It sets the result of an expression under evaluation in a 'scope' variable. c:remove Remove the specified scoped variable from a particular scope. c:catch It is used for Catches any Throwable exceptions that occurs in the body. c:if Test a condition and display the body content only if the expression evaluates is true. c:choose, c:when, c:otherwise Conditional tag that includes its body content if the evaluated condition is true. c:forEach Repeats the nested body content for fixed number of times or over collection. c:param Adds a parameter in a containing 'import' tag's URL. c:redirect Redirects the browser to a new URL and supports the context-relative URLs. c:url Creates a URL with optional query parameters. 50

51. Formatting tags Tags Description fmt:parseNumber It is used to Parses the string representation of a currency, percentage or number. fmt:timeZone It specifies a parsing action nested in its body or the time zone for any time formatting. fmt:formatNumber It is used to format the numerical value with specific format or precision. fmt:parseDate It parses the string representation of a time and date. fmt:bundle It is used for creating the ResourceBundle objects which will be used by their tag body. fmt:setTimeZone It stores the time zone inside a time zone configuration variable. fmt:setBundle It loads the resource bundle and stores it in a bundle configuration variable or the named scoped variable. fmt:message It display an internationalized message. fmt:formatDate It formats the time and/or date using the supplied pattern and styles. 51

52. XML tags Tags Description x:out Similar to <%= ... > tag, but for XPath expressions. x:parse It is used for parse the XML data specified either in the tag body or an attribute. x:set It is used to sets a variable to the value of an XPath expression. x:choose It is a conditional tag that establish a context for mutually exclusive conditional operations. x:when It is a subtag of  that will include its body if the condition evaluated be 'true'. x:otherwise It is subtag of  that follows  tags and runs only if all the prior conditions evaluated be 'false'. x:if It is used for evaluating the test XPath expression and if it is true, it will processes its body content. x:transform It is used in a XML document for providing the XSL(Extensible Stylesheet Language) transformation. x:param It is used along with the transform tag for setting the parameter in the XSLT style sheet. 52

53. SQL Tags Tags Description sql:setDataSource It is used for creating a simple data source suitable only for prototyping. sql:query It is used for executing the SQL query defined in its sql attribute or the body. sql:update It is used for executing the SQL update defined in its sql attribute or in the tag body. sql:param It is used for sets the parameter in an SQL statement to the specified value. sql:dateParam It is used for sets the parameter in an SQL statement to a specified java.util.Date value. sql:transaction It is used to provide the nested database action with a common connection. 53

54. <%@ taglib uri ="http://java.sun.com/jsp/jstl/core" prefix="c"%> <%@ taglib uri ="http://java.sun.com/jsp/jstl/sql" prefix=" sql "%> <html> <body> < sql:setDataSource var =" db " driver=" com.mysql.jdbc.Driver " url =" jdbc:mysql ://localhost:3306/test " user=" root " password=" root "/> < sql:query dataSource ="${db}" var =" rs "> SELECT * from student; </ sql:query > <h1>Student Details</h1> <c:forEach var ="table" items="${ rs.rows }"> <c:out value="${ table.rollno }"/> <c:out value="${table.name}"/> <c:out value="${ table.dept }"/> < c:out value="${ table.score }"/> </c:forEach> </body> </html> 54 Database Access using JSTL

55. Creating HTML forms by embedding JSP code. <html> <head> <title>Using GET Method to Read Form Data</title> </head> < body> <h1>Using GET Method to Read Form Data</h1> < ul > <li><p><b>First Name:</b> <%= request.getParameter (" first_name ")%> </p></li> <li><p><b>Last Name:</b> <%= request.getParameter (" last_name ")%> </p></li> </ ul > </body> </html>

56. DATABASE CONNECTIVITY JDBC perspectives JDBC program example

57. JDBC Java Database Connectivity  ( JDBC ) is an application programming interface (API) for the programming language Java, which defines how a client may access a database It is Java based data access technology and used for Java database connectivity JDBC allows multiple implementations to exist and be used by the same application The JVM uses a JDBC driver to translate generalized JDBC calls into vendor specific database calls

58. JDBC Architecture

59. JDBC Architecture JDBC API JDBC API provides universal data access from the Java programming language Using the JDBC API, you can access virtually any data source, from relational databases to spreadsheets and flat files The JDBC API is comprised of two packages : java.sql javax.sql

60. JDBC Architecture JDBC Driver Manager The DriverManager class acts as an interface between user and drivers It keeps track of the drivers that are available and handles establishing a connection between a database and the appropriate driver The DriverManager class maintains a list of Driver classes that have registered themselves by calling the method DriverManager.registerDriver ()

61. JDBC Architecture JDBC Driver A  JDBC driver  is a software component enabling a Java application to interact with a database JDBC drivers are analogous to ODBC drivers, ADO.NET data providers, and OLE DB providers To connect with individual databases, JDBC (the Java Database Connectivity API) requires drivers for each database The JDBC driver gives out the connection to the database and implements the protocol for transferring the query and result between client and database .

62. Drivers Types Type 1 - JDBC-ODBC Bridge Type 2 - Native API Driver Type 3 – Network-Protocol Driver Type 4 – Database-Protocol Driver 62

63. Drivers Types Type 1  that calls native code of the locally available ODBC driver. Type 2  that calls database vendor native library on a client side. This code then talks to database over the network. Type 3 , the pure-java driver that talks with the server-side middleware that then talks to the database. Type 4 , the pure-java driver that uses database native protocol. 63

64. Drivers Types Type 1 - JDBC-ODBC Bridge Uses a bridging technology to access a database. JDBC-ODBC bridge is an example. It provides a gateway to the ODBC. Type 2 - Native API Driver Native API drivers. Driver contains Java code that calls native C/C++ methods provided by the database vendors. Type 3 – Network-Protocol Driver Generic network API that is then translated into database-specific access at the server level. The JDBC driver on the client uses sockets to call a middleware application on the server that translates the client requests into an API specific to the desired driver. Extremely flexible. Type 4 – Database-Protocol Driver Using network protocols built into the database engine talk directly to the database using Java sockets. Almost always comes only from database vendors. 64

65. Type-1 JDBC-ODBC Bridge 65

66. Type-1 JDBC-ODBC Bridge C onverts JDBC method calls into ODBC function calls P latform-dependent ODBC must be installed on the computer having the driver Sun (now Oracle) provided a JDBC-ODBC Bridge river:  sun.jdbc.odbc.JdbcOdbcDriver . Advantages Almost any database for which an ODBC driver is installed can be accessed, and data can be retrieved. Disadvantages Performance overhead The ODBC driver needs to be installed on the client machine. Not suitable for applets Specific ODBC drivers are not always available on all platforms No support from JDK 1.8 (Java 8) onwards. 66

67. Type 2 - Native API Driver 67

68. Type 2 - Native API Driver It is a database driver implementation that uses the client-side libraries of the database Converts JDBC method calls into native calls of the database API Advantages As there is no implementation of JDBC-ODBC bridge, it may be considerably faster than a Type 1 driver. Disadvantages The vendor client library needs to be installed on the client machine. Not all databases have a client-side library. This driver is platform dependent. No Applets support 68

69. Type 3 – Network-Protocol Driver 69

70. Type 3 – Network-Protocol Driver Pure Java driver for database middleware It 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 a vendor-specific database protocol.  platform-independent Advantages Since the communication between client and the middleware server is database independent, there is no need for the database vendor library on the client. The middleware server can provide typical middleware services like caching, load balancing, logging, and auditing. A single driver can handle any database, provided the middleware supports it. Disadvantages Requires database-specific coding to be done in the middle tier. The middleware layer added may result in additional latency, but is typically overcome by using better middleware services. 70

71. Type-4 Database-Protocol driver (Pure Java driver) 71

72. Type-4 Database-Protocol driver (Pure Java driver) Database driver implementation that converts JDBC calls directly into a vendor-specific database protocol Written completely in Java Platform independent Advantages These drivers don't translate the requests into an intermediary format (such as ODBC) The client application connects directly to the database server The JVM can manage all aspects of the application-to-database connection Disadvantages Drivers are database specific, as different database vendors use widely different network protocols. 72

73. Which Driver should be Used ? Type is 4: If you are accessing one type of database, such as Oracle, Sybase, or IBM Type 3: If your Java application is accessing multiple types of databases at the same time Type 2: When a type 3 or type 4 driver is not available Type 1: It is typically used for development and testing purposes only .

74. Basic steps to use a database in Java Register the Driver class Create connection Create statement Execute queries Close connection 74

75. JDBC program example-1 import java.sql .*; public class DatabaseAccess { public static void main(String args []) throws IOException { try { Class.forName (" com.mysql.jdbc.Driver "); Connection conn = DriverManager.getConnection (" jdbc:mysql :// localhost / test","root","root "); Statement stmt = conn.createStatement (); ResultSet rs = stmt.executeQuery ("SELECT * FROM student"); while( rs.next ()) { System.out.println ("Roll No: " + rs.getInt (1) + "< br >"); System.out.println ("Name: " + rs.getString (2) + "< br >"); } stmt.close (); conn.close (); } catch( SQLException se ) { se.printStackTrace (); } } } 75

76. JDBC program example-2 import java.sql .*; class DatabaseInsert { public static void main(String args []) { try { Class.forName (" oracle.jdbc.driver.OracleDriver "); Connection con= DriverManager.getConnection (" jdbc:oracle:thin :@localhost:1521:testdb","system","oracle"); PreparedStatement stmt = con.prepareStatement ("insert into Emp values(?,?)"); stmt.setInt (1,101); stmt.setString (2,"Ratan"); int i= stmt.executeUpdate (); System.out.println (i+" records inserted"); con.close (); } catch(Exception e ){ System.out.println (e );} } } 76

77. Class.forName () The   forName ()  method of Class class is used to register the driver class. This method is used to dynamically load the driver class. DriverManager class The DriverManager class maintains a list of Driver classes that have registered themselves by calling the method DriverManager.registerDriver (). public static Connection getConnection (String url,String userName,String password ) : establish the connection with the specified url , username and password. Connection interface A Connection is the session between java application and database . public Statement createStatement (): creates a statement object that can be used to execute SQL queries . public void close():  closes the connection and Releases a JDBC resources immediately. Statement interface provides methods to execute queries with the database . public ResultSet executeQuery (String sql ):  is used to execute SELECT query. It returns the object of ResultSet . public int executeUpdate (String sql ):  is used to execute specified query, it may be create, drop, insert, update, delete etc.

78. ResultSet interface maintains a cursor pointing to a row of a table. Initially, cursor points to before the first row.  public boolean next(): is used to move the cursor to the one row next from the current position. public int getInt ( int columnIndex ): return the data of specified column index of the current row as int. public int getInt (String columnName ): return the data of specified column name of the current row as int . public String getString ( int columnIndex ): return the data of specified column index of the current row as String . public String getString (String columnName ): return the data of specified column name of the current row as String. PreparedStatement interface a subinterface of Statement  It is used to execute parameterized query. Eg .: String  sql =" insert into  emp  values(?,?,?) ";