Unit III- Server Side Technologies

Transcription

1 Web Technology Unit III- Server Side Technologies By Prof. B.A.Khivsara Note: The material to prepare this presentation has been taken from internet and are generated only for students reference and not for commercial use.

2 Outline Introduction to Server Side technology and TOMCAT, Servlet: Introduction to Servlet, need and advantages, Servlet Lifecycle, Creating and testing of sample Servlet, session management. JSP: Introduction to JSP, advantages of JSP over Servlet, elements of JSP page: directives, comments, scripting elements, actions and templates, JDBC Connectivity with JSP.

3 Servlets & Tomcat

4 Out Line Servlet Introduction Servlet Lifecycle Servlet Architecture Software Requirement to run Servlet Tomcat Introduction Tomcat Configuration in Eclipse Steps to run servlets in Eclipse Sample code Session Management

5 What are Servlets? Java Servlets are programs that run on a Web or Application server and act as a middle layer between a requests coming from a Web browser or other HTTP client and databases or applications on the HTTP server. Using Servlets, you can collect input from users through web page forms, present records from a database or another source, and create web pages dynamically.

6 Advantages of Servlet over CGI Performance is significantly better. Servlets execute within the address space of a Web server. It is not necessary to create a separate process to handle each client request. Servlets are platform-independent because they are written in Java. servlets are trusted. The full functionality of the Java class libraries is available to a servlet.

7 Servlets Architecture

8 Servlets Packages Java Servlets are Java classes run by a web server that has an interpreter that supports the Java Servlet specification. Servlets can be created using the packages javax.servlet javax.servlet.http

9 Out Line Servlet Introduction Servlet Lifecycle Servlet Architecture Software Requirement to run Servlet Tomcat Introduction Tomcat Configuration in Eclipse Steps to run servlets in Eclipse Sample code

10 Servlet Life Cycle The servlet is initialized by calling the init() method. The servlet calls service() method to process a client's request. The servlet is terminated by calling the destroy() method. Finally, servlet is garbage collected by the garbage collector of the JVM.

11 The init() Method The init method is called only once. It is called only when the servlet is created, and not called for any user requests afterwards. So, it is used for one-time initializations. When a user invokes a servlet, a single instance of each servlet gets created, with each user request resulting in a new thread that is handed off to doget or dopost as appropriate. The init() method simply creates or loads some data that will be used throughout the life of the servlet. The init method definition looks like this public void init() throws ServletException { // Initialization code... }

12 The service() Method The service() method is the main method to perform the actual task. The servlet container (i.e. web server) calls the service() method to handle requests coming from the client( browsers) and to write the formatted response back to the client. When server receives a request for a servlet, the service() method checks the HTTP request type (GET, POST) and calls doget, dopost, methods as appropriate. Here is the signature of this method public void service(servletrequest request, ServletResponse response) throws ServletException, IOException { }

13 The doget() Method A GET request results from a normal request for a URL or from an HTML form that has no METHOD specified and it should be handled by doget() method. public void doget(httpservletrequest request, HttpServletResponse response) } throws ServletException, IOException { // Servlet code

14 The dopost() Method A POST request results from an HTML form that specifically lists POST as the METHOD and it should be handled by dopost() method. public void dopost(httpservletrequest request, HttpServletResponse response) } throws ServletException, IOException { // Servlet code

15 The destroy() Method The destroy() method is called only once at the end of the life cycle of a servlet. This method gives your servlet a chance to close database connections, halt background threads, and perform other such cleanup activities. After the destroy() method is called, the servlet object is marked for garbage collection. The destroy method definition looks like this public void destroy() { // Finalization code... }

16 Out Line Servlet Introduction Servlet Lifecycle Servlet Architecture Software Requirement to run Servlet Tomcat Introduction Tomcat Configuration in Eclipse Steps to run servlets in Eclipse Sample code Session Management

17 Architecture Diagram First the HTTP requests coming to the server are delegated to the servlet container. The servlet container loads the servlet before invoking the service() method. Then the servlet container handles multiple requests by spawning multiple threads, each thread executing the service() method of a single instance of the servlet.

18 Out Line Servlet Introduction Servlet Lifecycle Servlet Architecture Software Requirement to run Servlet Tomcat Introduction Tomcat Configuration in Eclipse Steps to run servlets in Eclipse Sample code Session Management

19 Requirements Before running Servlet your machine requires following tools 1> Eclipse (IDE-integrated development environment) 2> Tomcat (Web Server)

20 Out Line Servlet Introduction Servlet Lifecycle Servlet Architecture Software Requirement to run Servlet Tomcat Introduction Tomcat Configuration in Eclipse Steps to run servlets in Eclipse Sample code Session Management

21 Apache-Tomcat Apache Tomcat, often referred to as Tomcat Server, is an open-source Java Servlet Container developed by the Apache Software Foundation (ASF). Tomcat implements several Java EE specifications including Java Servlet, JavaServer Pages (JSP), Java EL, and WebSocket, and provides a "pure Java" HTTP web server environment in which Java code can run.

22 Tomcat- Components Catalina Coyote Jasper Cluster High availability Web application

23 Tomcat- Components Catalina Catalina is Tomcat's servlet container. Catalina implements Sun Microsystems's specifications for servlet and JavaServer Pages (JSP). In Tomcat, a Realm element represents a "database" of usernames, passwords, and roles assigned to those users. Catalina to be integrated into environments where such authentication information is already being created and maintained, and then use that information to implement Container Managed Security as described in the Servlet Specification.

24 Tomcat- Components Coyote Coyote is a Connector component for Tomcat that supports the HTTP 1.1 protocol as a web server. This allows Catalina, nominally a Java Servlet or JSP container, to also act as a plain web server that serves local files as HTTP documents. Coyote listens for incoming connections to the server on a specific TCP port and forwards the request to the Tomcat Engine to process the request and send back a response to the requesting client.

25 Tomcat- Components Jasper Jasper is Tomcat's JSP Engine. Jasper parses JSP files to compile them into Java code as servlets (that can be handled by Catalina). At runtime, Jasper detects changes to JSP files and recompiles them. From Jasper to Jasper 2, important features were added: JSP Tag library pooling - Each tag markup in JSP file is handled by a tag handler class. Background JSP compilation - While recompiling modified JSP Java code, the older version is still available for server requests. Recompile JSP when included page changes - Pages can be inserted and included into a JSP at runtime JDT Java compiler - Jasper 2 can use the Eclipse JDT Java compiler

26 Tomcat- Components These components are added from Tomcat 7.0 version Cluster This component has been added to manage large applications. High availability A high-availability feature has been added to facilitate the scheduling of system upgrades (e.g. new releases, change requests) without affecting the live environment. Web application It has also added user- as well as system-based web applications enhancement to add support for deployment across the variety of environments.

27 Out Line Servlet Introduction Servlet Lifecycle Servlet Architecture Software Requirement to run Servlet Tomcat Introduction Tomcat Configuration in Eclipse Steps to run servlets in Eclipse Sample code Session Management

28 How to configure tomcat server in Eclipse? (One time Requirement) If you are using Eclipse IDE first time, you need to configure the tomcat server First. For configuring the tomcat server in eclipse IDE, click on servers tab at the bottom side of the IDE -> right click on blank area -> New -> Servers -> choose tomcat then its version -> next -> click on Browse button -> select the apache tomcat root folder previous to bin -> next -> addall -> Finish.

29 How to configure tomcat server in Eclipse?

30 How to configure tomcat server in Eclipse?

31 How to configure tomcat server in Eclipse?

32 How to configure tomcat server in Eclipse?

33 How to configure tomcat server in Eclipse?

34 How to configure tomcat server in Eclipse?

35 How to configure tomcat server in Eclipse?

36 How to configure tomcat server in Eclipse?

37 Out Line Servlet Introduction Servlet Lifecycle Servlet Architecture Software Requirement to run Servlet Tomcat Introduction Tomcat Configuration in Eclipse Steps to run servlets in Eclipse Sample code Session Management

38 Steps to run servlet in Eclipse Create a Dynamic web project create a servlet add servlet-api.jar file Run the servlet

39 Steps to run servlet in Eclipse Create a Dynamic web project create a servlet add servlet-api.jar file Run the servlet

40 Create the dynamic web project Start Eclipse and In Menu : File -> New -> Dynamic Web Project

41 Create the dynamic web project

42 Create the dynamic web project

43 Create the dynamic web project

44 Create the dynamic web project Structure of Dynamic Web Project

45 Steps to run servlet in Eclipse Create a Dynamic web project create a servlet add servlet-api.jar file Run the servlet

46 Create a servlet Right click on Src -> New -> Sevlet

47 Create a servlet Give name of class

48 Create a servlet

49 Create a servlet Either select doget or dopost

50 Create a servlet Servlet is created, you can write the code now.

51 Steps to run servlet in Eclipse Create a Dynamic web project create a servlet add servlet-api.jar file Run the servlet

52 Add servlet-api.jar file

53 Add servlet-api.jar file

54 Add servlet-api.jar file In Tomcat folder goto Lib folder and select servlet-api.jar file

55 Add servlet-api.jar file

56 Steps to run servlet in Eclipse Create a Dynamic web project create a servlet add servlet-api.jar file Run the servlet

57 Run the servlet Right click on project name -> click Run As -> Run on Server

58 Run the servlet

59 Run the servlet

60 Out Line Servlet Introduction Servlet Lifecycle Servlet Architecture Software Requirement to run Servlet Tomcat Introduction Tomcat Configuration in Eclipse Steps to run servlets in Eclipse Sample code Session Management

61 Example 1- To Print Hello World directly import java.io.*; import javax.servlet.*; import javax.servlet.http.*; public class HelloWorld extends HttpServlet { public void init() throws ServletException { } public void doget(httpservletrequest request, HttpServletResponse response) throws ServletException, IOException { response.setcontenttype("text/html"); PrintWriter out = response.getwriter(); out.println("<h1> Hello World </h1>"); } public void destroy() { } }

62 Example 2- To Print Hello World using init method import java.io.*; import javax.servlet.*; import javax.servlet.http.*; public class HelloWorld extends HttpServlet { private String message; public void init() throws ServletException { message = "Hello World"; } public void doget(httpservletrequest request, HttpServletResponse response) throws ServletException, IOException { response.setcontenttype("text/html"); PrintWriter out = response.getwriter(); out.println("<h1>" + message + "</h1>"); } public void destroy() { } }

63 Reading Form Data using Servlet getparameter() You call request.getparameter() method to get the value of a form parameter. getparametervalues() Call this method if the parameter appears more than once and returns multiple values, for example checkbox. getparameternames() Call this method if you want a complete list of all parameters in the current request.

64 Example 3- To read data from HTML file and print that. It requires 2 files: 1. HTML (s1.html)file 2. Servlet (s2.java) File First Run HTML file and after clicking on submit button it will run servel(.java) file.

65 Example 3- To read data from HTML file and print that. S1.html (html code) <html> <form method= post action= s2 > Enter Your Name <input type=text name= t1 > <br> <input type= submit value= submit > </form> </body> </html>

66 Example 3- To read data from HTML file and print that. S2.java (Servlet Code) import java.io.*; import javax.servlet.*; public class s2 extends HttpServlet { public void dopost(httpservletrequest request, HttpServletResponse response) throws ServletException, IOException { response.setcontenttype("text/html"); String a= request.getparameter("t1"); PrintWriter out= response.getwriter(); out.print("<br>your Name is: "+a); } }

67 Example 4 (HTML code) To read data from HTML checkbox values print that <!DOCTYPE html> <html> Name of Servlet File <body> <form method="post" action=s1> Hobbies <input type="checkbox" name="t1" value= Cricket"> Cricket <input type="checkbox" name="t1" value="music">music <input type="checkbox" name="t1" value= Dance">Dance <input type="submit" value="submit"> </form> </body> </html>

68 Example 4 (servlet code) To read data from HTML checkbox values print that protected void dopost(httpservletrequest request, HttpServletResponse response) throws ServletException, IOException { response.setcontenttype("text/html"); PrintWriter out=response.getwriter(); String[] values=request.getparametervalues("t1"); for(int i=0;i<values.length;i++) { out.println("<li>"+values[i]+"</li>"); } } }

69 Example 5 (HTML code) To print complete list of all parameters <!DOCTYPE html> <html> <body> <form method="post" action=s1> Hobbies Enter Name <input type= text" name="t1" > <br> Enter Address <input type= text" name="t2" > <br> Enter Class <input type= text" name="t3" > <br> <input type="submit" value="submit"> </form> </body> </html>

70 Example 5 (Servlet code) To print complete list of all parameters protected void dopost(httpservletrequest request, HttpServletResponse response) throws ServletException, IOException { response.setcontenttype("text/html"); PrintWriter out = response.getwriter(); } Enumeration e = request.getparameternames(); while(e.hasmoreelements()) { Object obj = e.nextelement(); out.println((string) obj+ "<br>"); }

71 Out Line Servlet Introduction Servlet Lifecycle Servlet Architecture Software Requirement to run Servlet Tomcat Introduction Tomcat Configuration in Eclipse Steps to run servlets in Eclipse Sample code Session Management

72 Session Tracking (Management) Session Tracking is a way to maintain state (data) of an user. It is also known as session management in servlet. Http protocol is a stateless so we need to maintain state using session tracking techniques. Each time user requests to the server, server treats the request as the new request. So we need to maintain the state of an user to recognize to particular user. Why use Session Tracking? To recognize the user It is used to recognize the particular user.

73 Session Tracking Techniques Cookies Hidden Form Field URL Rewriting HttpSession

74 Session Tracking- Using Cookies A cookie is a small piece of information that is persisted between the multiple client requests. A cookie has a name, a single value, and optional attributes such as a comment, path and domain qualifiers, a maximum age, and a version number. How Cookie works In cookies technique, we add cookie with response from the servlet. So cookie is stored in the cache of the browser. After that if request is sent by the user, cookie is added with request by default. Thus, we recognize the user as the old user.

75 Session Tracking- Using Cookies Types of Cookie Non-persistent cookie Persistent cookie Non-persistent cookie It is valid for single session only. It is removed each time when user closes the browser. Persistent cookie It is valid for multiple session. It is not removed each time when user closes the browser. It is removed only if user logout or signout.

76 Session Tracking- Using Cookies Advantage of Cookies Simplest technique of maintaining the state. Cookies are maintained at client side. Disadvantage of Cookies It will not work if cookie is disabled from the browser. Only textual information can be set in Cookie object.

77 Session Tracking- Using Cookies Useful Methods of Cookie class Method public void setmaxage(int expiry) public String getname() public String getvalue() public void setname(string name) public void setvalue(string value) Description Sets the maximum age of the cookie in seconds. Returns the name of the cookie. The name cannot be changed after creation. Returns the value of the cookie. changes the name of the cookie. changes the value of the cookie.

78 Session Tracking- Using Cookies How to create Cookie? Cookie ck=new Cookie("user","sonu");//creating cookie object response.addcookie(ck);//adding cookie in the response How to delete Cookie? Cookie ck=new Cookie("user","");//deleting value of cookie ck.setmaxage(0);//changing the maximum age to 0 seconds response.addcookie(ck);//adding cookie in the response How to get Cookies? Cookie ck[]=request.getcookies(); for(int i=0;i<ck.length;i++){ out.print("<br>"+ck[i].getname()+" "+ck[i].getvalue());//printing na me and value of cookie }

79 Session Tracking- Using Cookies Simple example of Servlet Cookies

80 Session Tracking- Using Cookies Simple example of Servlet Cookies index.html <form action="servlet1" method="post"> Name:<input type="text" name="username"/><br/> <input type="submit" value="go"/> </form>

81 Session Tracking- Using Cookies Simple example of Servlet Cookies Servlet1.java import java.io.*; import javax.servlet.*; import javax.servlet.http.*; public class FirstServlet extends HttpServlet { public void dopost(httpservletrequest request, HttpServletResponse response){ try{ response.setcontenttype("text/html"); PrintWriter out = response.getwriter(); String n=request.getparameter("username"); out.print("welcome "+n); Cookie ck=new Cookie("uname",n);//creating cookie object response.addcookie(ck);//adding cookie in the response //creating submit button out.print("<form action='servlet2'>"); out.print("<input type='submit' value='go'>"); out.print("</form>"); out.close(); }catch(exception e){system.out.println(e);} } }

82 Session Tracking- Using Cookies Simple example of Servlet Cookies Servlet2.java import java.io.*; import javax.servlet.*; import javax.servlet.http.*; public class SecondServlet extends HttpServlet { public void dopost(httpservletrequest request, HttpServletResponse response){ try{ response.setcontenttype("text/html"); PrintWriter out = response.getwriter(); Cookie ck[]=request.getcookies(); out.print("hello "+ck[0].getvalue()); out.close(); }catch(exception e){system.out.println(e);} } }

83 Session Tracking Techniques Cookies Hidden Form Field URL Rewriting HttpSession

84 Session Tracking- Hidden Form Fields In case of Hidden Form Field a hidden (invisible) textfield is used for maintaining the state of an user. In such case, we store the information in the hidden field and get it from another servlet. Synax <input type="hidden" name="uname" value= Bhavana"> Here, uname is the hidden field name and Bhavana is the hidden field value.

85 Session Tracking- Hidden Form Fields Advantage of Hidden Form Field It will always work whether cookie is disabled or not. Disadvantage of Hidden Form Field: It is maintained at server side. Extra form submission is required on each pages. Only textual information can be used.

86 Session Tracking- Hidden Form Fields Example of passing username

87 Session Tracking- Hidden Form Fields Example of passing username index.html <form method="post" action= First"> Name:<input type="text" name="user" /><br/> Password:<input type="text" name="pass" ><br/> <input type="submit" value="submit"> </form>

88 Session Tracking- Hidden Form Fields Example of passing username First.java import java.io.*; import javax.servlet.*; import javax.servlet.http.*; public class First extends HttpServlet { } protected void dopost(httpservletrequest request, HttpServletResponse response) throws ServletException, IOException { } response.setcontenttype("text/html;charset=utf-8"); PrintWriter out = response.getwriter(); String user = request.getparameter("user"); //creating a new hidden form field out.println("<form action='second'>"); out.println("<input type='hidden' name='user' value='"+user+"'>"); out.println("<input type='submit' value='submit' >"); out.println("</form>");

89 Session Tracking- Hidden Form Fields Example of passing username Second.java import java.io.*; import javax.servlet.*; import javax.servlet.http.*; public class Second extends HttpServlet { protected void doget(httpservletrequest request, HttpServletResponse response) throws ServletException, IOException { response.setcontenttype("text/html;charset=utf-8"); PrintWriter out = response.getwriter(); } } //getting parameter from the hidden field String user = request.getparameter("user"); out.println("welcome "+user);

90 Session Tracking Techniques Cookies Hidden Form Field URL Rewriting HttpSession

91 Session Tracking- URL Rewriting If the client has disabled cookies in the browser then session management using cookie wont work. In that case URL Rewriting can be used as a backup. URL rewriting will always work. In URL rewriting, a token(parameter) is added at the end of the URL. The token consist of name/value pair separated by an equal(=) sign. For Example:

92 Session Tracking- URL Rewriting When the User clicks on the URL having parameters, the request goes to the Web Container with extra bit of information at the end of URL. The Web Container will fetch the extra part of the requested URL and use it for session management. The getparameter() method is used to get the parameter value at the server side. Advantage of URL Rewriting It will always work whether cookie is disabled or not (browser independent). Extra form submission is not required on each pages. Disadvantage of URL Rewriting It will work only with links. It can send only textual information.

93 Session Tracking- URL Rewriting Example index.html <form method="post" action="validate"> Name:<input type="text" name="user" /><br/> Password:<input type="text" name="pass" ><br/> <input type="submit" value="submit"> </form>

94 Session Tracking- URL Rewriting Example Validate.java import java.io.*; import javax.servlet.*; import javax.servlet.http.*; public class MyServlet extends HttpServlet { } protected void dopost(httpservletrequest request, HttpServletResponse response) } throws ServletException, IOException { response.setcontenttype("text/html;charset=utf-8"); String name = request.getparameter("user"); String pass = request.getparameter("pass"); } if(pass.equals("1234")) { response.sendredirect("first?user_name="+name+"");

95 Session Tracking- URL Rewriting Example First.java import java.io.*; import javax.servlet.*; import javax.servlet.http.*; public class First extends HttpServlet { protected void doget(httpservletrequest request, HttpServletResponse response) throws ServletException, IOException { response.setcontenttype("text/html;charset=utf-8"); PrintWriter out = response.getwriter(); String user = request.getparameter("user_name"); out.println("welcome "+user); } }

96 Session Tracking Techniques Cookies Hidden Form Field URL Rewriting HttpSession

97 Session Tracking- HttpSession The servlet container uses this interface to create a session between an HTTP client and an HTTP server. The session persists for a specified time period, across more than one connection or page request from the user. You would get HttpSession object by calling the public method getsession() of HttpServletRequest, as below HttpSession session = request.getsession();

98 Session Tracking- HttpSession How to get the HttpSession object? public HttpSession getsession():returns the current session associated with this request, or if the request does not have a session, creates one. Commonly used methods of HttpSession interface public String getid():returns unique identifier value. public long getcreationtime():returns the time when this session was created. public long getlastaccessedtime():returns the last time the client sent a request associated with this session. public void invalidate():invalidates this session then unbinds any objects bound to it.

99 Session Tracking- HttpSession Example Hit Count HTML File <h3>hit Count Example with HttpSession</h3> <form method="get" action= HitCount"> Click for Hit Count <input type="submit" value="get HITS"> </form> </body>

100 Session Tracking- HttpSession Example Hit Count public class HitCount extends HttpServlet { public void service(httpservletrequest req, HttpServletResponse res) throws ServletException, IOException { res.setcontenttype("text/html") ; PrintWriter out = res.getwriter( ); HttpSession session = req.getsession(); Integer hitnumber = (Integer) session.getattribute("rama"); if (hitnumber == null) { hitnumber = new Integer(1); } else { hitnumber = new Integer(hitNumber.intValue()+1) ; } session.setattribute("rama", hitnumber); // storing the value with session object out.println("your Session ID: " + session.getid()); // never changes in the whole session out.println("<br>session Creation Time: " + new Date(session.getCreationTime())); out.println("<br>time of Last Access: " + new Date(session.getLastAccessedTime())); out.println("<br>latest Hit Count: " + hitnumber); // increments by 1 for every hit

101 Session Tracking- HttpSession Example Hit Count output

102 JSP

103 Outline Introduction to JSP Advantages of JSP over Servlet JSP Life cycle JSP Creation in Eclipse Elements of JSP page: directives, comments, scripting elements, actions and templates JDBC Connectivity with JSP.

104 Introduction to JSP JSP technology is used to create web application just like Servlet technology. It can be thought of as an extension to servlet because it provides more functionality than servlet such as expression language, jstl etc. A JSP page consists of HTML tags and JSP tags. The jsp pages are easier to maintain than servlet because we can separate designing and development. It provides some additional features such as Expression Language, Custom Tag etc.

105 Outline Introduction to JSP Advantages of JSP over Servlet JSP Life cycle JSP Creation in Eclipse Elements of JSP page: directives, comments, scripting elements, actions and templates JDBC Connectivity with JSP.

106 Advantages of JSP vs. Active Server Pages (ASP) The advantages of JSP are twofold. First, the dynamic part is written in Java, not Visual Basic or other MS specific language, so it is more powerful and easier to use. Second, it is portable to other operating systems and non- Microsoft Web servers. vs. JavaScript JavaScript can generate HTML dynamically on the client but can hardly interact with the web server to perform complex tasks like database access and image processing etc.

107 Advantage of JSP over Servlet 1) Extension to Servlet JSP technology is the extension to servlet technology. We can use all the features of servlet in JSP. In addition to, we can use implicit objects, predefined tags, expression language and Custom tags in JSP, that makes JSP development easy. 2) Easy to maintain JSP can be easily managed because we can easily separate our business logic with presentation logic. In servlet technology, we mix our business logic with the presentation logic. 3) Fast Development: No need to recompile and redeploy If JSP page is modified, we don't need to recompile and redeploy the project. The servlet code needs to be updated and recompiled if we have to change the look and feel of the application. 4) Less code than Servlet In JSP, we can use a lot of tags such as action tags, jstl, custom tags etc. that reduces the code. Moreover, we can use EL, implicit objects etc.

108 Outline Introduction to JSP Advantages of JSP over Servlet JSP Life cycle JSP Creation in Eclipse Elements of JSP page: directives, comments, scripting elements, actions and templates JDBC Connectivity with JSP.

109 Life cycle of a JSP Page The JSP pages follows these phases: Translation of JSP Page Compilation of JSP Page Classloading (class file is loaded by the classloader) Instantiation (Object of the Generated Servlet is created). Initialization ( jspinit() method is invoked by the container). Reqeust processing ( _jspservice() method is invoked by the container). Destroy ( jspdestroy() method is invoked by the container).

110 Life cycle of a JSP Page In the end a JSP becomes a Servlet JSP pages are converted into Servlet by the Web Container. The Container translates a JSP page into servlet class source(.java) file and then compiles into a Java Servlet class.

111 JSP Compilation When a browser asks for a JSP, the JSP engine first checks to see whether it needs to compile the page. If the page has never been compiled, or if the JSP has been modified since it was last compiled, the JSP engine compiles the page. The compilation process involves three steps Parsing the JSP. Turning the JSP into a servlet. Compiling the servlet.

112 JSP Initialization When a container loads a JSP it invokes the jspinit() method before servicing any requests. If you need to perform JSP-specific initialization, override the jspinit() method public void jspinit(){ // Initialization code... } Typically, initialization is performed only once and as with the servlet init method, you generally initialize database connections, open files, and create lookup tables in the jspinit method.

113 JSP Execution This phase of the JSP life cycle represents all interactions with requests until the JSP is destroyed. Whenever a browser requests a JSP and the page has been loaded and initialized, the JSP engine invokes the _jspservice() method in the JSP. The _jspservice() method as follows void _jspservice(httpservletrequest request, HttpServletResponse response) { // Service handling code... } The _jspservice() method of a JSP is invoked on request basis. This is responsible for generating the response for that request and this method is also responsible for generating responses to all seven of the HTTP methods, i.e, GET, POST, DELETE, etc.

114 JSP Cleanup The destruction phase of the JSP life cycle represents when a JSP is being removed from use by a container. The jspdestroy() method is the JSP equivalent of the destroy method for servlets. The jspdestroy() method has the following form public void jspdestroy() { // Your cleanup code goes here. }

115 Outline Introduction to JSP Advantages of JSP over Servlet JSP Life cycle JSP Creation in Eclipse Elements of JSP page: directives, comments, scripting elements, actions and templates JDBC Connectivity with JSP.

116 Creating a JSP Page A JSP page looks similar to an HTML page, but a JSP page also has Java code in it. We can put any regular Java Code in a JSP file using a scriplet tag which start with <% and ends with %>. JSP pages are used to develop dynamic responses.

117 Creating a JSP Page Open Eclipse, Click on New Dynamic Web Project

118 Creating a JSP Page Give a name to your project and click on OK

119 Creating a JSP Page You will see a new project created in Project Explorer

120 Creating a JSP Page To create a new JSP file right click on Web Content directory, New JSP file

121 Creating a JSP Page Give a name to your JSP file and click Finish.

122 Creating a JSP Page Write something in your JSP file. The complete HTML and the JSP code, goes inside the <body> tag, just like HTML pages.

123 Creating a JSP Page To run your project, right click on Project, select Run As Run on Server

124 Creating a JSP Page To start the server, Choose existing server name and click on finish

125 Creating a JSP Page See the Output in your browser.

126 Outline Introduction to JSP Advantages of JSP over Servlet JSP Life cycle JSP Creation in Eclipse Elements of JSP page: directives, comments, scripting elements, actions and templates JDBC Connectivity with JSP.

127 Elements of JSP Scripting Element Example Comment <%-- comment --%> Directive directive %> Declaration <%! declarations %> Scriptlet <% scriplets %> Expression <%= expression %>

128 JSP Comments JSP comment marks text or statements that the JSP container should ignore. Syntax of the JSP comments <%-- This is JSP comment --%> Example shows the JSP Comments <html> <body> <h2>a Test of Comments</h2> <%-- This comment will not be visible in the page source --%> </body> </html>

129 JSP Directives A JSP directive affects the overall structure of the servlet class. It usually has the following form <%@ directive attribute="value" %> There are three types of directive tag

130 The Scriptlet A scriptlet can contain any number of JAVA language statements, variable or method declarations, or expressions that are valid in the page scripting language. syntax of Scriptlet <% code fragment %> first example for JSP <html> <head><title>hello World</title></head> <body> Hello World!<br/> <% out.println("your IP address is " + request.getremoteaddr()); %> </body> </html>

131 JSP Declarations A declaration declares one or more variables or methods that you can use in Java code later in the JSP file. You must declare the variable or method before you use it in the JSP file. Syntax for JSP Declarations <%! declaration; %> Example for JSP Declarations <%! int i = 0; %> <%! int a, b, c; %> <%! Circle a = new Circle(2.0); %>

132 JSP Expression A JSP expression element contains a scripting language expression that is evaluated, converted to a String, and inserted where the expression appears in the JSP file. you cannot use a semicolon to end an expression. Syntax of JSP Expression <%= expression %> Example shows a JSP Expression <html> <body> <%= "Welcome "+request.getparameter("uname") %> </body> </html>

133 JSP Actions JSP actions use to control the behavior of the servlet engine. You can dynamically insert a file, reuse JavaBeans components, forward the user to another page, or generate HTML for the Java plugin. Syntax <jsp:action_name attribute = "value" />

134 JSP Actions S.No. Syntax & Purpose 1 jsp:include - Includes a file at the time the page is requested. 2 jsp:usebean - Finds or instantiates a JavaBean. 3 jsp:setproperty - Sets the property of a JavaBean. 4 jsp:getproperty - Inserts the property of a JavaBean into the output. 5 jsp:forward - Forwards the requester to a new page. 6 jsp:plugin - Generates browser-specific code that makes an OBJECT or EMBED tag for the Java plugin. 7 jsp:element - Defines XML elements dynamically. 8 jsp:attribute - Defines dynamically-defined XML element's attribute. 9 jsp:body - Defines dynamically-defined XML element's body. 10 jsp:text - Used to write template text in JSP pages and documents.

135 JSP Templates If a Website has multiple pages with identical formats, which is common, even simple layout changes require modifications to all of the pages. To minimize the impact of layout changes, we need a mechanism for including layout in addition to content; that way, both layout and content can vary without modifying files that use them. That mechanism is JSP templates. (Same like CSS in HTML)

136 JSP Templates Templates are JSP files that include parameterized content. The templates have a set of custom tags: template:get, template:put, template:insert. Example <template:get name='header'/> <template:get name='content'/> <template:get name='footer'/> <template:insert template='/articletemplate.jsp'> <template:put name='header' content='/header.html' /> <template:put name='sidebar' content='/sidebar.jsp' /> <template:put name='content' content='/introduction.html'/> <template:put name='footer' content='/footer.html' /> </template:insert>

137 Outline Introduction to JSP Advantages of JSP over Servlet JSP Life cycle JSP Creation in Eclipse Elements of JSP page: directives, comments, scripting elements, actions and templates JDBC Connectivity with JSP.

138 JDBC Java JDBC is a java API to connect and execute query with the database. JDBC API uses jdbc drivers to connect with the database. Before JDBC, ODBC API was the database API to connect and execute query with the database. But, ODBC API uses ODBC driver which is written in C language (i.e. platform dependent and unsecured). That is why Java has defined its own API (JDBC API) that uses JDBC drivers (written in Java language).

139 JDBC Driver JDBC Driver is a software component that enables java application to interact with the database. There are 4 types of JDBC drivers: 1. JDBC-ODBC bridge driver 2. Native-API driver (partially java driver) 3. Network Protocol driver (fully java driver) 4. Thin driver (fully java driver)

140 JDBC Connectivity with JSP Software Requirement 1 MySQL 2 MySQL Connector (Jar file) 3 Apache Tomcat Server 4 Eclipse Important Note: Copy MySQL Connector (Jar file) into Tomcat s Bin and Lib folder Before running program right click on project name -> Build path -> Configure build path -> Libraries -> Add External Jar file -> Mysql.jar file -> ok

141 JDBC Connectivity with JSP- Create table and add rows in database(mysql) Create the Employee table in the db1 database as follows mysql> Create database db1; mysql> use db1; mysql> create table emp ( id int, name varchar (255) ); Query OK, 0 rows affected (0.08 sec)

142 JDBC Connectivity with JSP- Create table and add rows in database(mysql) Insert Data mysql> INSERT INTO emp VALUES (100, 'Zara''); mysql> INSERT INTO Employees VALUES (101, 'Mamta');

143 JSP Code in Eclipse File->New->Web->Dynamic Web Project->Give Project Name Right click on Project name->new->package->give package name For Writing JSP Code project-> Right click->new->jsp file-> Give file name with.jsp Extension In Body tag write java code in script let tag <% %> Right click on.jsp file -> Run -> Run as Server

144 JDBC Connectivity with JSP- Example 1- JSP Code for to select data from emp table page import ="java.sql.*" %> page import ="javax.sql.*" %> <% Class.forName("com.mysql.jdbc.Driver"); java.sql.connection con = DriverManager.getConnection("jdbc:mysql://localhost:3306/db1","root","root"); Statement st= con.createstatement(); ResultSet rs=st.executequery("select * from emp"); out.print("<h2 align=center>employee Database</h2>"); out.print("<table border=1 align=center>"); out.print("<tr><th> ENo</th> <th>ename</th></tr>");

145 JDBC Connectivity with JSP- Example 1- JSP Code for to select data from emp table while(rs.next()) { out.print("<tr align=center>"); out.print("<td>"); out.print(rs.getint(1)); out.print("</td>"); out.print("<td>"); out.print(rs.getstring(2)); out.print("</td>"); out.print("</tr>"); } %>

146 JDBC Connectivity with JSP- Example 2- JSP Code for insert data in emp table and display the inserted data from table It requires 2 files 1. S1.html (Html file to take values from user) 2. s2.jsp (jsp file to insert data in database and to display the inserted data)

147 JDBC Connectivity with JSP- Example 2- JSP Code for insert data in emp table and display the inserted data from table S1.html <html> <body> <form method="post" action= s2.jsp"> Enter Employee No<input type="text" name="t1"><br> Enter Empoyee Name <input type="text" name="t2"><br> <input type="submit" value="submit"> </form> </body> </html>

148 JDBC Connectivity with JSP- Example 2- JSP Code for insert data in emp table and display the inserted data from table S2.jsp page import ="java.sql.*" %> page import ="javax.sql.*" %> <% Class.forName("com.mysql.jdbc.Driver"); java.sql.connection con = DriverManager.getConnection("jdbc:mysql://localhost:3307/db1","root","root"); Statement st= con.createstatement(); int id= Integer.parseInt(request.getParameter("t1")); String name=request.getparameter("t2"); st.executeupdate("insert into emp values("+id+",'"+name+"')");

149 JDBC Connectivity with JSP- Example 2- JSP Code for insert data in emp table and display the inserted data from table ResultSet rs=st.executequery("select * from emp"); out.print("<h2 align=center>employee Database</h2>"); out.print("<table border=1 align=center>"); out.print("<tr><th> ENo</th><th>Ename</th></tr>"); while(rs.next()) { out.print("<tr align=center>"); out.print("<td>"); out.print(rs.getint(1)); out.print("</td>"); out.print("<td>"); out.print(rs.getstring(2)); out.print("</td>"); out.print("</tr>"); } %>

150 References