HTTP Requests

Note: Locating a servlet may first involve translating a JSP into a servlet.

HTTP request format

REQUEST NL (HEADER NL)* NL [BODY]

GET /myapp/form.html HTTP/1.0

HEADER ::= NAME: VALUE
NAME ::= Host | User-Agent | Cookie | etc.

HTTP Response format

STATUS NL (HEADER NL)* NL DOCUMENT

Forms

Attributes

ACTION="myapp/foo.jsp"
METHOD="post"
ENCTYPE="application/x-www-form-urlencoded"
TARGET="which frame"
NAME="Form #3"
ONRESET="jscriptFun()"
ONSUBMIT="jscriptFun()"

Elements

Input Elements <input ... />
   Attributes:
      name, value, checked, size, etc.
      onclick, ondblclick, onselect, onchange, onfocus, onblur
      type
         Fields (text, password, hidden)
         Buttons (submit, reset, radio)
         checkbox
Text Areas <textarea ...> INITIAL TEXT </textarea>
   Attributes:
      name, rows, cols, etc.
      onselect, onchange, onfocus, onblur,
      onkeydown, onkeypress, onkeyup
Pop-up Menus <select ...> OPTIONS </select>
   Attributes:
      name, size, multiple
      onclick, onfocus, onblur, onchange
   Options <option ... />
      Attributes:
         selected, value

form.html

<html>
<head> <title> Super Form </title> </head>
<body>

User info form: <hr />
<form action = "/myapp/request.jsp" method = "post">
    <p>
   <input type = "hidden" name = "arg" value = "42">
   Name:
   <input type = "text" name = "client" value = "???" size = "30"/>
   <br />
   Password: <input type = "password" name = "password" size = "8"/>
   </p>  <p>
   Party: <br />
   <input type = "radio" name = "party" value="Democrat" checked/>
   Democrat <br />
   <input type = "radio" name = "party" value="Republican"/>
   Republican
   </p>  <p>
   State: <br />
   <select name = "country">
   <option value = "CA">California</option>
   <option value = "OR">Oregon</option>
   <option value = "NM">New Mexico</option>
   </select>
   </p>  <p>
   Comments: <br />
   <textarea name = "comments" rows = "5" cols = "40" >
   Your comments would be appreciated
   </textarea>
   </p>  <p>
   Send me more information:
      <input type = "checkbox" name = "more info" />
   </p>  <p>
   <input type = "reset" value = "Clear Form" />
   <input type = "submit" value = "Send Info" />
   </p> </form> <hr />
</body>
</html>

request.jsp

<html>
<head> <title> Display HTTP Request </title> </head>
<body>

<%
   java.util.Enumeration attNames = request.getAttributeNames();
   java.util.Enumeration paramNames = request.getParameterNames();
   java.util.Enumeration hdrNames = request.getHeaderNames();
%>

Request = <br />
<%= request.getMethod() %>
<%= request.getServerName() %>:
<%= request.getServerPort() %>
<%= request.getProtocol() %>

<hr />
Request headers: <br/>
<% while (hdrNames.hasMoreElements()) {
   String name = (String) hdrNames.nextElement();
   String value = request.getHeader(name);
   out.println("..." + name + ": " + value + "<br />");
   } %>
<hr />
Request parameters: <br/>
<% while (paramNames.hasMoreElements()) {
   String name = (String) paramNames.nextElement();
   String value = request.getParameter(name);
   out.println("..." + name + ": " + value + "<br />");
   } %>
<hr />
Request attributes: <br/>
<% while (attNames.hasMoreElements()) {
   String name = (String) attNames.nextElement();
   Object value = request.getAttribute(name);
   out.println("..." + name + ": " + value + "<br />");
   } %>
<hr />
</body>
</html>