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JSP Implicit Objects Implicit Objects in JSP are objects that are automatically available in JSP. 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
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Methods of request Object
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. getQueryString(): Gets any query string that is part of the HTTP request URI.
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Use JSP to Process a Form
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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>
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Computesum.jsp <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 .
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Process form with various controls
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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>
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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); %>
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Using getparametervalues()
<form method="get“ action=“readmultiplevalues.jsp”> <input type="checkbox" name="author" value="Tan"> Tan <input type="checkbox" name="author" value="Mohd Ali">Ali <input type="checkbox" name="author" value="Kumar"> Kumar <input type="submit" value="Query"> </form>
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Readmultiplevalues.jsp <% String[] authors = request.getParameterValues("author"); if (authors != null) { %> <h3>You have selected author(s):</h3> <ul> <% for (int i = 0; i < authors.length; ++i) <li><%= authors[i] %></li> <% } %> </ul>
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LTC EXERCISES Write JSP code to validate the DATA entered by the user through HTML form Examples Password & Re-enter password fields MATCHED or not AGE field between 18 and 100 Password atleast 8 characters Mobile Number exactly 10 digits
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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.
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Example: Logon Restrict access to home page for valid user.
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Example: Logon v2 index.html Home.html Logon.jsp <html>
<head><title></title></head> <body> <form action=“logon.jsp” method=“post”> Please logon:<br /> <input name="txtUserName" type="text" /><br /> <input name="txtPassWord" type="text" /><br /> <input name="btnLogon" type="submit" value="Logon" /> </form> </body> </html> index.html <html> <head><title>My Home page</title></head> <body> <p> Welcome to my home page.<br /> <img src="YouAreHere.jpg" /> </p> </body> </html> Home.html <% String un; String pw; String msg = ""; un = request.getParameter("txtUserName"); pw = request.getParameter("txtPassWord"); if (un.equals(“admin") && pw.equals(“12345")){ response.sendRedirect(“Home.html"); }else{ out.print(“Login details incorrect.“); } %> Logon.jsp
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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
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DEMO
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