Server-Side Scripting with Java Server Page, JSP

ISYS 350

Java Website

• Java Tutorial:– http://docs.oracle.com/javase/tutorial/

• JSP, Servlet tutorial:– http://www.apl.jhu.edu/~hall/java/Servlet-Tutoria

l/

Java Platforms• Java SE (Standard Edition) provides the core

functionality of the Java programming language. It defines everything from the basic types and objects of the Java programming language to high-level classes that are used for networking, security, database access, etc.

• Java EE (Enterprise Edition) is built on top of the Java SE platform for developing and running large-scale, multi-tiered, scalable, reliable, and secure network applications.

• Java ME (Mobile Edition) provides an API and a small-footprint virtual machine for running Java programming language applications on small devices, like mobile phones.

Using Java Classes

• To develop Java applications, we need to use many different Java classes.

• Groups of related Java classes are organized into packages.

• To use a class from a package we use the “import” statement to import the class.

Common Java packages

Package name Description

java.lang Provides classes fundamental to Java, including classes that work with primitive data types, strings, and math functions.

java.text Provides classes to handle text, dates, and numbers.

java.util Provides various utility classes including those for working with collections.

java.io Provides classes to read data from files and to write data to files.

java.sql Provides classes to read data from databases and to write data to databases.

java.applet An older package that provides classes to create an applet.

Common Java packages (continued)

Package name Description

java.awt An older package called the Abstract Window Toolkit (AWT) that provides classes to create graphical user interfaces.

java.awt.event A package that provides classes necessary to handle events.

javax.swing A newer package called Swing that provides classes to create graphical user interfaces and applets.

Hyper Text Transfer Protocol: Request & Response

Web ServerBrowser

HTTP Request

HTTP Response

Web Application

Data Sent with Request and Response

• Request: – requested URL, cookies, queryString, data from a

form, etc.

• Response:– Web page content in HTML code– Cookies– Etc.

JSP Implicit Objects• Implicit Objects in JSP are objects that are

automatically available in JSP. Implicit Objects are Java objects that the JSP Container provides to a developer to access them in their program.– request: The request object retrieves the values that the client

browser passed to the server during an HTTP request

– response: This denotes the HTTP Response data. – Session: This denotes the data associated with a specific

session of user. The main use of Session Objects is for maintaining states when there are multiple page requests.

– Out

Methods of request Objecthttp://gulland.com/courses/jsp/objects

• getParameter(String name): Returns the value of a request parameter as a String, or null if the parameter does not exist.

• getQueryString(): Gets any query string that is part of the HTTP request URI.

• getCookies(): Gets the array of cookies found in this request.

• getRequestURI(): Gets the URI to the current JSP page.

• etc.

Methods of response Object

• addCookie(Cookie): Adds the specified cookie to the response. It can be called multiple times to set more than one cookie.

• sendRedirect(String): Sends a temporary redirect response to the client using the specified redirect location URL.

JSP Out Object• clearBuffer: The clearBuffer method of out

object is used to clear the output buffer. • println: The println method of out object is used

to write the value to the output, including the newline character. – Ex. out.println("The Output is:" + ex);

• print: The print method of out object writes the value to the output without a newline character.

out.print("Welcome!!!"); out.print("To JSP Training");

Output is: Welcome!!! To JSP Training

Use JSP to Process a Form

FORM

• Form attribute:– Method:

• Preferred method is: Post– Action: Specify the URL of a program on a server or an email

address to which a form’s data will be submitted.– Method: Post/Get<form name="testForm" method="post" action="computeSum.jsp“>

• Button:– Type = “submit”

<input type="submit" value="ComputeSumJSP" name="btnCompute"/>

The eight primitive data types

Type Bytes Use

byte 1 Very short integers from -128 to 127.

short 2 Short integers from -32,768 to 32,767.

int 4 Integers from -2,147,483,648 to 2,147,483,647.

long 8 Long integers from -9,223,372,036,854,775,808 to 9,223,372,036,854,775,807.

float 4 Single-precision, floating-point numbers from -3.4E38 to 3.4E38 with up to 7 significant digits.

double 8 Double-precision, floating-point numbers from -1.7E308 to 1.7E308 with up to 16 significant digits.

char 2 A single Unicode character that’s stored in two bytes.

boolean 1 A true or false value.

Compute the Sum of 2 Numbers:

Form Example

<body> <div>Compute the sum of two numbers</div> <form name="testForm" method="post" action="computeSum.jsp"> Enter num1: <input type="text" name="num1" value="" /><br> Enter num2: <input type="text" name="num2" value="" /><br><br> <input type="submit" value="ComputeSumJSP" name="btnCompute"/> </form> </body>

Example of JSP scriptlet <% %> Compute the Sum of 2 Numbers:

<body> <% String value1, value2; double n1, n2, sum; value1=request.getParameter("num1"); value2=request.getParameter("num2"); n1= Double.parseDouble(value1); n2= Double.parseDouble(value2); sum=n1+n2; out.println("The sum is:" + sum); %> </body>

Note 1: Double is an object, not “double” data type.Note 2: “out” is an implicit object that does not need to be declared. It is already predefined .

Writing HTML code as output<body> <% String value1, value2; double n1, n2, sum; value1=request.getParameter("num1"); value2=request.getParameter("num2"); n1= Double.parseDouble(value1); n2= Double.parseDouble(value2); sum=n1+n2; out.println(" <p>Value1: <input type='text' name='num1' size='20' value='" + value1 + "'></p>"); out.println(" <p>Value2: <input type='text' name='num2' size='20' value='" + value2 + "'></p>");

out.println("The sum is: <input type='text' name='sum' size='20' value='" + sum + "'>" ); %> </body>

Using JSP Expression:return a string, <%= %>

String value1, value2; double n1, n2, sum; value1=request.getParameter("num1"); value2=request.getParameter("num2"); n1= Double.parseDouble(value1); n2= Double.parseDouble(value2); sum=n1+n2; %>

<form method="POST" name="testForm" action="ComputeSum2.jsp"> <p>Value1: <input type="text" name="num1" size="20" value="<%=value1%>"></p> <p>Value2: <input type="text" name="num2" size="20" value="<%=value2%>"></p> <p> Sum is: <input type="text" name="num2" size="20" value="<%=sum%>"></p></form>

Import Java ClassExample: Display Current Date Time

• Import java.util.Date– %@page import="java.util.Date"%

• Define a Date type variable:– Date now = new Date();

• Display in textbox using JSP expression:<p>The time is: <input type="text" name="num2" size="20" value="<

%=now%>"></p>

Compute Future Value:Process form with various controls

Form Code<form name="fvForm" method="post" action="computeFV.jsp"> Enter present value: <input type="text" name="PV" value="" /><br><br> Select interest rate: <select name="Rate"> <option value=.04>4%</option> <option value=.05>5%</option> <option value=.06>6%</option> <option value=.07>7%</option> <option value=.08>8%</option> </select><br><br> Select year: <br> <input type="radio" name="Year" value="10" />10-year<br> <input type="radio" name="Year" value="15" />15-year<br> <input type="radio" name="Year" value="30" />30-year<br><br>

<input type="submit" value="ComputeFVJSP" name="btnCompute" /> </form>

JSP Code Example

<body> <% String myPV, myRate, myYear; myPV=request.getParameter("PV"); myRate=request.getParameter("Rate"); myYear=request.getParameter("Year"); double FV, PV, Rate, Year; PV=Double.parseDouble(myPV); Rate=Double.parseDouble(myRate); Year=Double.parseDouble(myYear); FV=PV*Math.pow(1+Rate,Year); out.println("FutureValue is:"+ FV); %>

Using the get method

• Querystring:– http://localhost:8080/DemoM262/computeFVget.jsp?PV=

1000&Rate=.04&Year=10&btnCompute=ComputeFVJSP

• Code:String qString;qString=request.getQueryString();out.println(qString);

Use the same getParameter() method to accessing data submitted with a querystring

<body> <% String myPV, myRate, myYear; myPV=request.getParameter("PV"); myRate=request.getParameter("Rate"); myYear=request.getParameter("Year"); double FV, PV, Rate, Year; PV=Double.parseDouble(myPV); Rate=Double.parseDouble(myRate); Year=Double.parseDouble(myYear); FV=PV*Math.pow(1+Rate,Year); out.println("FutureValue is:"+ FV); %>

Use Client-Side Validating and Sumbit Validated Form

<script type="text/javascript"><!--function Validating(){var Valid;Valid=true;if (document.fvForm.PV.value=="") {Valid=false;}

if (Valid==false){alert("Cannot contain blank");}else {document.fvForm.submit();}

}--></script>

Note: Must use a standard button, not submit button: <input type="button" value="ComputeFVJSP" name="btnCompute" onclick="Validating()"/>

Depreciation Table

Straight Line Depreciation Table <form name="depForm" method="post" action="createDepTable.jsp"> Enter Property Value: <input type="text" name="pValue" value="" /><br> Enter Property Life: <input type="text" name="pLife" value="" /><br> <input type="submit" value="ShowTable JSP" name="btnShowTable" /> </form>

Output

<% String strValue, strLife; strValue=request.getParameter("pValue"); strLife=request.getParameter("pLife"); double value, life, depreciation,totalDepreciation=0; value=Double.parseDouble(strValue); life=Double.parseDouble(strLife); NumberFormat nf = NumberFormat.getCurrencyInstance(); out.println("Straight Line Depreciation Table" + "<br>"); out.println("Property Value: <input type='text' name='pValue' value='" + nf.format(value) + "' /><br>"); out.println("Property Life: <input type='text' name='pLife' value='" + life + "' /><br>"); depreciation=value/life; totalDepreciation=depreciation; out.println( "<table border='1' width='400' cellspacing=1>"); out.println("<thead> <tr> <th>Year</th> <th>Value at BeginYr</th>"); out.println("<th>Dep During Yr</th> <th>Total to EndOfYr</th></tr> </thead>"); out.println("<tbody>"); for (int count = 1; count <= life; count++) { out.write("<tr>"); out.write(" <td width='25%'>" + count + "</td>"); out.write(" <td width='25%'>" + nf.format(value) + "</td>"); out.write(" <td width='25%'>" + nf.format(depreciation) + "</td>"); out.write(" <td width='25%'>" + nf.format(totalDepreciation) + "</td>"); value -= depreciation; totalDepreciation+=depreciation; } %>

Number to Currency Format

• Import class:– %@page import="java.text.NumberFormat"%

• Define a format:– NumberFormat nf = NumberFormat.getCurrencyInstance();

• Convert:– nf.format(value)

Cookie

• Cookie is a small data file added by a website to reside in user’s system.

• Define a cookie:– new Cookie(“Key”, “value”);– Ex. Cookie cookieCID = new Cookie ("cookieCID",CID);

• Write a cookie: – response.addCookie(cookieCID);

Example:

<% String CID, Cname; CID=request.getParameter("CID"); Cname=request.getParameter("Cname"); Cookie cookieCID = new Cookie ("cookieCID",CID); response.addCookie(cookieCID); Cookie cookieCname = new Cookie ("cookieCname",Cname); response.addCookie(cookieCname);

out.println("CID cookie= " + CID + "added"); out.println("Cname cookie= " + Cname + "added"); %>

Read Cookies:Cookie is in array object, we need to get in

request.getCookies() of array

<% Cookie[] cookies = request.getCookies(); out.println(cookies[0].getName() + cookies[0].getValue() + "<br>"); out.println(cookies[1].getName() + cookies[1].getValue() + "<br>"); %>

Expire a cookie

• Add a expiration time:– cookieCID setMaxAge(N);

• N is # of seconds• N = 0, the cookie will be deleted right way• N < 0 : the cookie will be deleted once the user exit the

browser

Cookie cookieCID = new Cookie ("cookieCID",CID);cookieCID setMaxAge(-1);

JSP Session Object• Session Object denotes the data associated

with a specific session of user. • Methods:

– session.setAttribute(“Key”, object)• add an object to the session object associated with a key.

– session.getId()• return the unique identifier associated with the session

– session.getAttribute(“key”)• return the object with the specified key given in

parameter

Add an object to session objectAdd Cname to session, then redirect to another page to

read the cname

<% Cookie[] cookies = request.getCookies(); out.println(cookies[0].getName() + cookies[0].getValue() + "<br>"); out.println(cookies[1].getName() + cookies[1].getValue() + "<br>"); session.setAttribute("Cname", cookies[1].getValue()); response.sendRedirect("readSession.jsp"); %>

Retrieve an object from session

<% Object custName; custName=session.getAttribute("Cname"); out.println("Welcome, " + custName.toString()); %>