Java Tutorial/JSTL/Form Input

Check Parameter Value and Output Error Message

<%@ taglib prefix="c" uri="http://java.sun.ru/jstl/core" %>
<%@ taglib prefix="fmt" uri="http://java.sun.ru/jstl/fmt" %>
<h1>Peter"s Junk-Mail Service</h1>
<c:if test="${param.submitted}">
  <c:if test="${empty param.name}" var="noName" />
  <c:if test="${empty param.email}" var="noEmail" />
  <c:if test="${empty param.age}" var="noAge" />
  <c:catch var="ageError">
    <fmt:parseNumber var="parsedAge" value="${param.age}" />
    <c:if test="${parsedAge < 13}" var="youngAge" />
  </c:catch>
  <c:if test="${not empty ageError}" var="badAge" />
  <c:if
   test="${not (noName or noEmail or noAge or badAge or youngAge)}">
    <c:set value="${param.name}" var="name" scope="request"/>
    <c:set value="${param.email}" var="email" scope="request"/>
    <c:set value="${param.age}" var="age" scope="request"/>
    <jsp:forward page="spamFormHandler.jsp" />
  </c:if>
</c:if>
<form method="post">
  <input type="hidden" name="submitted" value="true" />
  Enter your name:
  <input type="text" name="name"
    value="<c:out value="${param.name}"/>" />
  <br />
  <c:if test="${noName}">
   <small><font color="red">
     Note: you must enter a name
   </font></small>
  </c:if>
  </p>
  Enter your email address:
  <input type="text" name="email"
    value="<c:out value="${param.email}"/>" />
  <br />
  <c:if test="${noEmail}">
   <small><font color="red">
     Note: you must enter an email address
   </font></small>
  </c:if>
  </p>

  Enter your age:
  <input type="text" name="age" size="3"
    value="<c:out value="${param.age}"/>" />
  <br />
  <c:choose>
    <c:when test="${noAge}">
     <small><font color="red">
       Note: you must enter your age
     </font></small>
    </c:when>
    <c:when test="${badAge}">
     <small><font color="red">
       Note: I couldn"t decipher the age you typed in
     </font></small>
    </c:when>
    <c:when test="${youngAge}">
     <small><font color="red">
       Please grow older and try again.
     </font></small>
    </c:when>
  </c:choose>
  </p>
  <input type="submit" value="Sign up" />
</form>

Get Date value from Form

index.jsp

<%@ taglib prefix="c" uri="http://java.sun.ru/jstl/core" %>
<form method="post" action="dateHandler.jsp">
  Please enter your birthday:
  <select name="month">
    <option value="Jan">January</option>
    <option value="Feb">February</option>
    <option value="Mar">March</option>
    <option value="Apr">April</option>
    <option value="May">May</option>
    <option value="Jun">June</option>
    <option value="Jul">July</option>
    <option value="Aug">August</option>
    <option value="Sep">September</option>
    <option value="Oct">October</option>
    <option value="Nov">November</option>
    <option value="Dec">December</option>
  </select>
  <select name="day">
    <c:forEach begin="1" end="31" var="day">
      <option><c:out value="${day}"/></option>
    </c:forEach>
  </select>
  <select name="year">
    <c:forEach begin="1930" end="2003" var="year">
      <option><c:out value="${year}"/></option>
    </c:forEach>
  </select>
  <input type="submit" value="Submit" />
</form>

JSTL Form Error Check and Forward

package beans;
public class Bid {
    
    /** Holds value of property price. */
    private long price;
    
    /** Holds value of property item. */
    private String item;
    
    /** Creates a new instance of Bid */
    public Bid() {
    }
    
    /** Getter for property price.
     * @return Value of property price.
     *
     */
    public long getPrice() {
        return this.price;
    }
    
    /** Setter for property price.
     * @param price New value of property price.
     *
     */
    public void setPrice(long price) {
        this.price = price;
    }
    
    /** Getter for property item.
     * @return Value of property item.
     *
     */
    public String getItem() {
        return this.item;
    }
    
    /** Setter for property item.
     * @param item New value of property item.
     *
     */
    public void setItem(String item) {
        this.item = item;
    }
    
}

Parse input from Form

<%@ taglib uri="http://java.sun.ru/jstl/core" prefix="c" %>
<%@ taglib uri="http://java.sun.ru/jstl/fmt" prefix="fmt" %>
<html>
  <head>
    <title>Parse Number</title>
  </head>
  <body>
    <form method="POST">
      <table>
        <tr>
          <td width="100%" colspan="2">
               Number Formatting
          </td>
        </tr>
        <tr>
          <td width="47%">Enter a number to be parsed:</td>
          <td width="53%">
            <input type="text" name="num" size="20" />
          </td>
        </tr>
        <tr>
          <td width="100%" colspan="2">
            <p align="center">
              <input type="submit" value="Submit" name="submit" />
              <input type="reset" value="Reset" name="reset" />
            </p>
          </td>
        </tr>
      </table>
      <P>&#160;</p>
    </form>
    <c:if test="${pageContext.request.method=="POST"}">
      <table>
        <tr>
          <td width="100%" colspan="2">
             Formatting: <c:out value="${param.num}" escapeXml="false" />
          </td>
        </tr>
        <tr>
          <td width="51%">type="number"</td>
          <td width="49%">
            <c:catch var="e">
              <fmt:parseNumber var="i" type="number" value="${param.num}" />
              <c:out value="${i}"  escapeXml="false" />
            </c:catch>
            <c:out value="${e}"  escapeXml="false" />
          </td>
        </tr>
        <tr>
          <td width="51%">type="currency"</td>
          <td width="49%">
            <c:catch var="e">
              <fmt:parseNumber var="i" type="currency" value="${param.num}" />
              <c:out value="${i}"  escapeXml="false" />
            </c:catch>
            <c:out value="${e}"  escapeXml="false" />
          </td>
        </tr>
        <tr>
          <td width="51%">type="percent"</td>
          <td width="49%">
            <c:catch var="e">
              <fmt:parseNumber var="i" type="percent"
              value="${param.num}" />
              <c:out value="${i}"  escapeXml="false" />
            </c:catch>
            <c:out value="${e}"  escapeXml="false" />
          </td>
        </tr>
        <tr>
          <td width="51%">type="number" integerOnly="true"</td>
          <td width="49%">
            <c:catch var="e">
              <fmt:parseNumber var="i" integerOnly="true"
              type="number" value="${param.num}" />
              <c:out value="${i}"  escapeXml="false" />
            </c:catch>
            <c:out value="${e}"  escapeXml="false" />
          </td>
        </tr>
      </table>
    </c:if>
  </body>
</html>

Set Parameter Value

index.jsp

<%@ taglib prefix="c" uri="http://java.sun.ru/jstl/core" %>
<%@ taglib prefix="fmt" uri="http://java.sun.ru/jstl/fmt" %>
<h1>Peter"s Junk-Mail Service</h1>
<c:if test="${param.submitted}">
  <c:if test="${empty param.name}" var="noName" />
  <c:if test="${empty param.email}" var="noEmail" />
  <c:if test="${empty param.age}" var="noAge" />
  <c:catch var="ageError">
    <fmt:parseNumber var="parsedAge" value="${param.age}" />
    <c:if test="${parsedAge < 13}" var="youngAge" />
  </c:catch>
  <c:if test="${not empty ageError}" var="badAge" />
  <c:if
   test="${not (noName or noEmail or noAge or badAge or youngAge)}">
    <c:set value="${param.name}" var="name" scope="request"/>
    <c:set value="${param.email}" var="email" scope="request"/>
    <c:set value="${param.age}" var="age" scope="request"/>
    <jsp:forward page="spamFormHandler.jsp" />
  </c:if>
</c:if>
<form method="post">
  <input type="hidden" name="submitted" value="true" />
  <P>
  Enter your name:
  <input type="text" name="name"
    value="<c:out value="${param.name}"/>" />
  <br />
  <c:if test="${noName}">
   <small><font color="red">
     Note: you must enter a name
   </font></small>
  </c:if>
  </p>
  <P>
  Enter your email address:
  <input type="text" name="email"
    value="<c:out value="${param.email}"/>" />
  <br />
  <c:if test="${noEmail}">
   <small><font color="red">
     Note: you must enter an email address
   </font></small>
  </c:if>
  </p>
  <P>
  Enter your age:
  <input type="text" name="age" size="3"
    value="<c:out value="${param.age}"/>" />
  <br />
  <c:choose>
    <c:when test="${noAge}">
     <small><font color="red">
       Note: you must enter your age
     </font></small>
    </c:when>
    <c:when test="${badAge}">
     <small><font color="red">
       Note: I couldn"t decipher the age you typed in
     </font></small>
    </c:when>
    <c:when test="${youngAge}">
     <small><font color="red">
       Note: You"re too young to receive pornographic
       junk mail.  Please grow older and try again.
     </font></small>
    </c:when>
  </c:choose>
  </p>
  <input type="submit" value="Sign up" />
</form>

Use ForEach to List All Form Parameters

index.jsp

<html>
  <head>
    <title>Set page parameters</title>
  </head>
  <body>
    This page allows you to enter information that is sent as request
    parameters to another page. The next page lists them. <P />
    <form action="listPageParameters.jsp" method="get">
      <table>
        <tr><td>Enter an adjective:</td>
            <td><input type="text" name="adjective" /></td>
        </tr>
        <tr><td>Enter a noun:</td>
            <td><input type="text" name="noun" /></td>
        </tr>
        <tr><td>Enter a color:</td>
            <td><input type="text" name="color" /></td>
        </tr>
      </table>
      <input type="submit" value="Send parameters" />
    </form>
  </body>
</html>

Use JSTL to Create URL From Form Input

index.jsp

<%@ taglib uri="http://java.sun.ru/jstl/core" prefix="c" %>
<c:set var="originalURL" value="http://localhost:8080/chapter05/core/url/url.jsp" />
<html>
  <head>
    <title>the c:url action </title>
  </head>
  <body>
    This page takes 3 values that you specify, and forwards them to another JSP.
    That JSP will create a URL to another page, that then extracts the
    parameters and displays them.
    <p />
      <form action="createURL.jsp" method="post">
        <table>
          <tr><td>Enter name:</td>
              <td><input type="text" name="name"   /></td></tr>
          <tr><td>Enter age:</td>
              <td><input type="text" name="age"    /></td></tr>
          <tr><td>Enter gender:</td >
              <td><input type="text" name="gender" /></td></tr>
        </table>
        <input type="submit" value="Submit details" />
      </form>
  </body>
</html>