Reading Request Parameter Values

The HTML specification defines a set of elements for presenting a form with fields in which the user can enter text or select among predefined choices. I’m sure you have encountered these countless times—to tell a vendor about yourself when downloading demo software, to specify what you’re looking for on a search engine site, or to select the toppings when you order a pizza online. But you may not be familiar with what’s going on behind the scene when you fill out the form and click Submit. Example 8-1 shows an HTML page that contains the most commonly used HTML form elements.

Example 8-1. HTML form elements
<html>
  <head>
    <title>User Info Entry Form</title>
  </head>
  <body bgcolor="white">
    <form action="process.jsp" method="post">
      <table>
        <tr>
          <td>Name:</td>
          <td>
            <input type="text" name="userName">
          </td>
        </tr>
        <tr>
          <td>Birth Date:</td>
          <td>
            <input type="text" name="birthDate">
          </td>
          <td>(Use format yyyy-mm-dd)</td>
        </tr>
        <tr>
          <td>Email Address:</td>
          <td>
            <input type="text" name="emailAddr">
          </td>
          <td>(Use format name@company.com)</td>
        </tr>
        <tr>
          <td>Gender:</td>
          <td>
            <input type="radio" name="gender" value="m" checked>Male<br>
            <input type="radio" name="gender" value="f">Female
          </td>
        </tr>
        <tr>
          <td>Lucky number:</td>
          <td>
            <input type="text" name="luckyNumber">
          </td>
          <td>(A number between 1 and 100)</td>
        </tr>
        <tr>
          <td>Favorite Foods:</td>
          <td>
            <input type="checkbox" name="food" value="z">Pizza<br> <input type="checkbox" name="food" value="p">Pasta<br> ...

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