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Java Servlet ISYS 350
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What is Java Servlet? It is a java class that serves a client request.
Servlets are most often used to: Process or store data that was submitted from an HTML form Provide dynamic content such as the results of a database query. It is not a web page and cannot be opened by itself. A servlet is called by a HTML form’s action attribute: <form name="fvForm" method="post" action="FVServlet">
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Adding a Servlet Servlet is a class with a “java” extension:
Ex: FVServlet.java It must belong to a package: Add a new Java Package: Ex. MyPackage Then add a new servelet under MyPackage: Ex: MyPackage FVServlet.java
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Servlet’s processRequest Method
This method use the same request and response objects as JSP. For example, it uses the request.getParameter method to read the data submitted with http request: myPV=request.getParameter("PV"); It uses the out.println statement to send HTML code to browser: out.println("<html>"); out.println("<head>");
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Example: Future Value Calculator: Requesting FVServlet servlet
<form name="fvForm" method="post" action="FVServlet"> 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> <br> <input type="submit" value="ComputeFVJSP" name="btnCompute"/> </form>
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FVServlet protected void processRequest(HttpServletRequest request, HttpServletResponse response) String myPV, myRate, myYear,qString; 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); Note: Copy/paste the code between: out.println("<body>"); and out.println("</body>");
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Servlet: depTableServlet to create straight line depreciation table
<form name="depForm" method="post" action="depTableServlet"> Enter Property Value: <input type="text" name="pValue" value="" /><br> Enter Property Life: <input type="text" name="pLife" value="" /><br> <input type="submit" value="Show Table" name="btnShowTable" /> </form>
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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='10%'>" + count + "</td>"); out.write(" <td width='30%'>" + nf.format(value) + "</td>"); out.write(" <td width='30%'>" + nf.format(depreciation) + "</td>"); out.write(" <td width='30%'>" + nf.format(totalDepreciation) + "</td>"); value -= depreciation; totalDepreciation+=depreciation; }
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