Principles and Techniques of DBMS 6 JSP & Servlet

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1 Principles and Techniques of DBMS 6 JSP & Servlet Haopeng Chen REliable, INtelligent and Scalable Systems Group (REINS) Shanghai Jiao Tong University Shanghai, China chen-hp@sjtu.edu.cn

2 Overview Servlet Servlet + JDBC reading JSP JSP concept JSP + JavaBean 2

3 Servlet access DB Index.html <BODY> <FORM METHOD=POST ACTION="SaveUser"> What's your name? <INPUT TYPE=TEXT NAME=username SIZE=20 ><BR> What's your address? <INPUT TYPE=TEXT NAME= SIZE=20 ><BR> What's your password? <INPUT TYPE=TEXT NAME=password SIZE=4 > <P> <INPUT TYPE=SUBMIT> </FORM> 3

4 Servlet access DB public class UserServlet extends HttpServlet { private static final long serialversionuid = DataSource ds; protected void processrequest(httpservletrequest request, HttpServletResponse response) throws ServletException, IOException { response.setcontenttype("text/html;charset=utf-8"); PrintWriter out = response.getwriter(); try { out.println("<html lang=\"en\">"); out.println("<head>"); out.println("<title>servlet UserServlet</title>"); out.println("</head>"); out.println("<body>"); out.println("<h1>servlet UserServlet at " + request.getcontextpath() + "</h1>"); String user = (String) request.getparameter("username"); String = (String) request.getparameter(" "); String password = (String) request.getparameter("password"); 4

5 Servlet access DB UserServlet.java Connection con = ds.getconnection(); PreparedStatement ps = con.preparestatement("select * FROM tbl_user WHERE username =?"); ps.setstring(1, user); ResultSet rs = ps.executequery(); rs.last(); int count = rs.getrow(); if ( count == 0) { PreparedStatement pst = con.preparestatement("insert INTO tbl_user VALUES (?,?,?,?) "); Random rand = new Random(); int id = rand.nextint(); pst.setint(1, id); pst.setstring(2,user); pst.setstring(3,password); pst.setstring(4, ); boolean b = pst.execute(); out.println("<p>" + user + " " + + " " + password); } else{ out.println("<p>" + "existing user"); } out.println("</body>"); out.println("</html>"); } } catch(sqlexception e){ e.printstacktrace(); } finally { out.close(); } 5

6 Servlet access DB protected void doget(httpservletrequest request, HttpServletResponse response) throws ServletException, IOException { response.setcontenttype("text/html;charset=utf-8"); processrequest(request, response); protected void dopost(httpservletrequest request, HttpServletResponse response) throws ServletException, IOException { processrequest(request, response); } public String getservletinfo() { return "Short description"; }// </editor-fold> 6

7 Servlet access DB Context.xml <Context> <Resource name="jdbc/sample auth="container" type="javax.sql.datasource" maxactive="100" maxidle="30" maxwait="10000" username="root" password=" " driverclassname="com.mysql.jdbc.driver" url="jdbc:mysql://localhost:3306/sample_one"/> </Context> 7

8 First JSP JSP simply puts Java inside HTML pages. You can take any existing HTML page and change its extension to ".jsp" instead of ".html". In fact, this is the perfect exercise for your first JSP. Take the following HTML file. Change its extension from ".html" to ".jsp. Now load the new file, with the ".jsp" extension, in your browser. <BODY> Hello, world 8

9 First JSP You will see the same output, but it will take longer! But only the first time. If you reload it again, it will load normally. What is happening behind the scenes is that your JSP is being turned into a Java file, compiled and loaded. This compilation only happens once, so after the first load, the file doesn't take long to load anymore. (But everytime you change the JSP file, it will be re-compiled again.) 9

10 Adding dynamic content via expressions Put the following text in a file with.jsp, place it in your JSP directory, and view it in a browser. <BODY> Hello! The time is now <%= new java.util.date() %> Notice that each time you reload the page in the browser, it comes up with the current time. The character sequences <%= and %> enclose Java expressions, which are evaluated at run time. 10

11 Scriptlets JSP also allows you to write blocks of Java code inside the JSP. You do this by placing your Java code between <% and %> characters just like expressions, but without the = sign at the start of the sequence. This block of code is known as a "scriptlet". A scriptlet contains Java code that is executed every time the JSP is invoked. <BODY> <% System.out.println( "Evaluating date now" ); java.util.date date = new java.util.date(); %> Hello! The time is now <%= date %> 11

12 Scriptlets By itself a scriptlet does not generate HTML. If a scriptlet wants to generate HTML, it can use a variable called "out". This variable does not need to be declared. It is already predefined for scriptlets, along with some other variables. <BODY> <% System.out.println( "Evaluating date now" ); java.util.date date = new java.util.date(); %> Hello! The time is now <% out.println( String.valueOf( date )); %> 12

13 Scriptlets Another very useful pre-defined variable is "request". The JSP "request" variable is used to obtain information from the request as sent by the browser. <BODY> <% // This scriptlet declares and initializes "date" System.out.println( "Evaluating date now" ); java.util.date date = new java.util.date(); %> Hello! The time is now <% out.println( date ); out.println( "<BR>Your machine's address is " ); out.println( request.getremotehost()); %> 13

14 Scriptlets A similar variable is "response". This can be used to affect the response being sent to the browser. For instance, you can call response.sendredirect( anotherurl ); to send a response to the browser that it should load a different URL. This response will actualy go all the way to the browser. The browser will then send a different request, to "anotherurl". <BODY> <% // This scriptlet declares and initializes "date" response.sendredirect("index3.jsp"); %> 14

15 Mixing Scriptlets and HTML For more complicated HTML, using the out variable all the time loses some of the advantages of JSP programming. <TABLE BORDER=2> <% int n = 10; for ( int i = 0; i < n; i++ ) { %> <TR> <TD>Number</TD> <TD><%= i+1 %></TD> </TR> <% } %> </TABLE> 15

16 JSP Directives It is possible to use "import" statements in JSPs, but the syntax is a little different from normal Java. <%@ page import="java.util.*" %> <BODY> <% System.out.println( "Evaluating date now" ); Date date = new Date(); %> Hello! The time is now <%= date %> The first line in the above example is called a "directive". A JSP "directive" starts with <%@ characters. <%@ page import="java.util.*,java.text.*" %> 16

17 JSP Directives The include directive is used to physically include the contents of another file. The included file can be HTML or JSP or anything else the result is as if the original JSP file actually contained the included text. <BODY> Going to include index.jsp...<br> include file= "index.jsp" %> 17

18 JSP Declarations The JSP you write turns into a class definition. To add a declaration, you must use the <%! and %> sequences to enclose your declarations, as shown below. <%@ page import="java.util.*" %> <BODY> <%! Date thedate = new Date(); Date getdate(){ System.out.println( "In getdate() method" ); return thedate; } %> Hello! The time is now <%= getdate() %> 18

19 JSP Tags A JSP tag is somewhat like an HTML tag. JSP tags can have a "start tag", a "tag body" and an "end tag". JSP tags do not use <%, but just the < character. <some:tag> body </some:tag> <some:tag/> <BODY> Going to include index.jsp...<br> <jsp:include page= index.jsp"/> 19

20 JSP Sessions On a typical web site, a visitor might visit several pages and perform several interactions. If you are programming the site, it is very helpful to be able to associate some data with each visitor. For this purpose, "session"s can be used in JSP. A session is an object associated with a visitor. Data can be put in the session and retrieved from it, much like a Hashtable. A different set of data is kept for each visitor to the site. 20

21 JSP Sessions First we have a form, let us call it GetName.html <BODY> <FORM METHOD=POST ACTION="SaveName.jsp"> What's your name? <INPUT TYPE=TEXT NAME=username SIZE=20> <P> <INPUT TYPE=SUBMIT> </FORM> 21

22 JSP Sessions The target of the form is "SaveName.jsp", which saves the user's name in the session. <% String name = request.getparameter( "username" ); session.setattribute( "thename", name ); %> <BODY> <A HREF="NextPage.jsp">Continue</A> The SaveName.jsp saves the user's name in the session, and puts a link to another page, NextPage.jsp. 22

23 JSP Sessions NextPage.jsp shows how to retrieve the saved name. <BODY> Hello, <%= session.getattribute( "thename" ) %> If you bring up two different browsers (not different windows of the same browser), or run two browsers from two different machines, you can put one name in one browser and another name in another browser, and both names will be kept track of. The session is kept around until a timeout period. Then it is assumed the user is no longer visiting the site, and the session is discarded. 23

24 Beans and Form processing The standard way of handling forms in JSP is to define a "bean". You just need to define a class that has a field corresponding to each field in the form. The class fields must have "setters" that match the names of the form fields. <BODY> <FORM METHOD=POST ACTION= NewSaveName.jsp"> What's your name? <INPUT TYPE=TEXT NAME=username SIZE=20><BR> What's your address? <INPUT TYPE=TEXT NAME= SIZE=20><BR> What's your password? <INPUT TYPE=TEXT NAME=password SIZE=4> <P> <INPUT TYPE=SUBMIT> </FORM> 24

25 Beans and Form processing The User Bean. package user; public class User { String username; String ; String password; } public void setusername( String value ) { username = value; } public void set ( String value ) { = value; } public void setage( String value ) { password = value; } public String getusername() { return username; } public String get () { return ; } public String getpassword() { return password; } 25

26 Beans and Form processing Now let us change NewSaveName.jsp" to use a bean to collect the data. <jsp:usebean id="user" class="user.user" scope="session"/> <jsp:setproperty name="user" property="*"/> <BODY> <A HREF="NextPage.jsp">Continue</A> 26

27 Beans and Form processing Let us modify NewNextPage.jsp to retrieve the data from bean.. <jsp:usebean id="user" class="user.user" scope="session"/> <BODY> You entered <BR> Name: <%= user.getusername() %> <BR> <%= user.get () %> <BR> Password: <%= user.getpassword() %> <BR> 27

28 Controllers Sometimes, some pre-processing needs to be done after the user has submitted a form. The result of this pre-processing decides where the control flow should go next. Such pre-processing code is frequently referred to as a "controller". <jsp:usebean id="user" class="user.userdata" scope="session"/> <jsp:setproperty name="user" property="*"/> <% String tgtpage = null; if ( user.choice.equals( "choice1" )) tgtpage = "tgt1.jsp"; else if ( user.choice.equals( "choice2" )) tgtpage = "tgt2.jsp"; else tgtpage = "tgtdefault.jsp"; response.sendredirect( tgtpage ); %> 28

29 Tag Libraries JSP introduces a method of extending JSP tags, called "tag libraries". These libraries allow addition of tags similar to jsp:include or jsp:forward, but with different prefixes other than jsp: and with additional features. <%@ page language="java" contenttype="text/html; charset=iso " pageencoding="iso "%> <%@ taglib uri=" prefix="sql" %> <%@ taglib uri=" prefix="c" %> <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" " <sql:query var="rs" datasource="jdbc/sample"> select id, username, password, from tbl_user </sql:query> <head> <title>db Test</title> </head> <body> <h2>results</h2> <c:foreach var="row" items="${rs.rows}"> ID ${row.id}<br/> Name ${row.username}<br/> Password ${row.password}<br/> ${row. }<br/> </c:foreach> </body> </html> 29

30 References Java EE 7 tutorial Java Servlet Specification spec/servlet-3_1- final.pdf?authparam= _99ca893c1d a2baf6a88414 bf8 JSP Tutorial 30

31 Thank You! 31

JSP (Java Server Page)

JSP (Java Server Page) http://www.jsptut.com/ http://www.jpgtutorials.com/introduction-to-javaserver-pages-jsp Lab JSP JSP simply puts Java inside HTML pages. Hello!