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2.7 Implicit Objects

Arguably, the most useful feature of the JSTL expression language is the implicit objects it defines for accessing all kinds of application data. Those implicit objects are listed in Table 2.5.

Table 2.5 JSTL Implicit Objects

Implicit Object

Type

Key12

Value

cookie

Map

Cookie name

Cookie

header

Map

Request header name

Request header value

headerValues

Map

Request header name

String[] of request header values

initParam

Map

Initialization parameter name

Initialization parameter value

param

Map

Request parameter name

Request parameter value

paramValues

Map

Request parameter name

String[] of request parameter values

pageContext

PageContext

N/A

N/A

pageScope

Map

Page-scoped attribute name

Page-scoped attribute value

requestScope

Map

Request-scoped attribute name

Request-scoped attribute value

sessionScope

Map

Session-scoped attribute name

Session-scoped attribute value

applicationScope

Map

Application-scoped attribute name

Application-scoped attribute value

There are three types of JSTL implicit objects:

  • Maps for a single set of values, such as request headers and cookies:

  • param, paramValues, header, headerValues, initParam, cookie
  • Maps for scoped variables in a particular scope:

  • pageScope, requestScope, sessionScope, applicationScope
  • The page context: pageContext

The rest of this section examines each of the JSTL implicit objects in the order listed above; the first category begins at "Accessing Request Parameters" below, the second category begins at "Accessing Scoped Attributes" on page 78, and use of the pageContext implicit object begins at "Accessing JSP Page and Servlet Properties" on page 80.

Accessing Request Parameters

Request parameters are the lifeblood of most Web applications, passing information from one Web component to another. That crucial role makes the param and paramValues implicit objects, both of which access request parameters, the most heavily used JSTL implicit objects.

The param and paramValues implicit objects are both maps of request parameters. For both the param and paramValues maps, keys are request parameter names, but the values corresponding to those keys are different for param and paramValues; param stores the first value specified for a request parameter, whereas paramValues stores a String array that contains all the values specified for a request parameter.13

Most often, the overriding factor that determines whether you use param or paramValue is the type of HTML element a request parameter represents; for example, Figure 2–5 shows a Web application that uses both param and paramValues to display request parameters defined by a form.

Figure 2-5Figure 2–5 Accessing Request Parameters with the param and paramValues Implicit Objects


The Web application shown in Figure 2–5 consists of two JSP pages, one that contains a form (top picture) and another that interprets the form's data (bottom picture). Listing 2.13 lists the JSP page that contains the form.

Listing 2.13 index.jsp

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<html>
   <head>
      <title>EL Implicit Objects: Request Parameters</title>
   </head>

   <body>
      <form action='param.jsp'>	
 <table>
            <tr>
               <td>First Name:</td>
               <td><input type='text' name='firstName'/></td>
            </tr>
            <tr>
               <td>Last Name:</td>
               <td><input type='text' name='lastName'/></td>
            </tr>
            <tr>
               <td>
                  Select languages that you have worked with: 
               </td>
               <td>
                  <select name='languages' size='7' 
                      multiple='true'>
                     <option value='Ada'>Ada</option>
                     <option value='C'>C</option>
                     <option value='C++'>C++</option>
                     <option value='Cobol'>Cobol</option>
                     <option value='Eiffel'>Eiffel</option>
                     <option value='Objective-C'>
                        Objective-C
                     </option>
                     <option value='Java'>Java</option>
                  </select>
               </td>
            </tr>
         </table>
         <p><input type='submit' value='Finish Survey'/>
      </form>
   </body>
</html>	

The preceding JSP page is unremarkable; it creates an HTML form with two textfields and a select element that allows multiple selection. That form's action, param.jsp, is the focus of our discussion. It is listed in Listing 2.14.

Listing 2.14 param.jsp

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<html>
   <head>
      <title>Accessing Request Parameters</title>	
 </head>
<body>
      <%@ taglib uri='http://java.sun.com/jstl/core' prefix='c' %>

      <font size='5'>
         Skillset for:
      </font>

      <%-- Access the lastName and firstName request parameters
           parameters by name --%>
      <c:out value='${param.lastName}'/>, 
      <c:out value='${param.firstName}'/>

      <%-- Show all request parameters and their values --%>
      <p><font size='5'>
         All Request Parameters:
      </font><p>

      <%-- For every String[] item of paramValues... --%>
      <c:forEach var='parameter' items='${paramValues}'> 
         <ul>
            <%-- Show the key, which is the request parameter
                 name --%>
            <li><b><c:out value='${parameter.key}'/></b>:</li>

            <%-- Iterate over the values -- a String[] -- 
                 associated with this request parameter --%>
            <c:forEach var='value' items='${parameter.value}'>
               <%-- Show the String value --%>
               <c:out value='${value}'/>   
            </c:forEach>
         </ul>
      </c:forEach>

      <%-- Show values for the languages request parameter --%>
      <font size='5'>
         Languages:
      </font><p>

      <%-- paramValues.languages is a String [] of values for the 
           languages request parameter --%>
      <c:forEach var='language' items='${paramValues.languages}'> 
         <c:out value='${language}'/>
      </c:forEach>

      <p>
	
 <%-- Show the value of the param.languages map entry,
           which is the first value for the languages
           request parameter --%>
      <c:out value="${'${'}param.languages} = ${param.languages}"/>
   </body>
</html>	

The preceding JSP page does four things of interest. First, it displays the lastName and firstName request parameters, using the param implicit object. Since we know that those request parameters represent textfields, we know that they are a single value, so the param implicit object fits the bill.

Second, the JSP page displays all of the request parameters and their values, using the paramValues implicit object and the <c:forEach> action.14 We use the paramValues implicit object for this task since we know that the HTML select element supports multiple selection and so can produce multiple request parameter values of the same name.

Because the paramValues implicit object is a map, you can access its values directly if you know the keys, meaning the request parameter names. For example, the third point of interest in the preceding JSP page iterates over the array of strings representing selected languages—paramValues.languages. The selected languages are accessed through the paramValues map by use of the key languages.

To emphasize the difference between param and paramValues, the fourth point of interest is the value of the param.languages request parameter, which contains only the first language selected in the HTML select element. A <c:out> action uses the EL expression ${'${'} to display the characters ${ and another EL expression—${param.languages}—to display the first value for the languages request parameter.

Accessing Request Headers

You can access request headers just as you can access request parameters, except that you use the header and headerValues implicit objects instead of param and paramValues.

Like the param and paramValues implicit objects, the header and headerValues implicit objects are maps, but their keys are request header names. The header map's values are the first value specified for a particular request header, whereas the headerValues map contains arrays of all the values specified for that request header.

Figure 2–6 shows a JSP page that uses the header implicit object to display all of the request headers and the first value defined for each of them.

Figure 2-6Figure 2–6 Accessing Request Headers with the header Implicit Object

The JSP page shown in Figure 2–6 is listed in Listing 2.15.

Listing 2.15 Accessing Requests Headers with the header Implicit Object

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<html>
   <head>
      <title>Request Headers</title>
   </head>

   <body>
      <%@ taglib uri='http://java.sun.com/jstl/core' prefix='c' %>

      <font size='5'>
         Request Headers:
      </font><p>

      <%-- Loop over the JSTL header implicit object, which is a 
           map --%>
      <c:forEach items='${header}' var='h'>
         <ul>
            <%-- Display the key of the current item, which
                 represents the request header name and the
                 current item's value, which represents the
                 header value --%>
            <li>Header Name: <c:out value='${h.key}'/></li>
            <li>Header Value: <c:out value='${h.value}'/></li>
         </ul>
      </c:forEach>
   </body>
</html>	

The keys stored in the header map are request header names and the corresponding values are strings representing request header values. You can also use the headerValues implicit object to iterate over request headers, like this:

<%-- Loop over the JSTL headerValues implicit object,
     which is a map --%>
<c:forEach items='${headerValues}' var='hv'>
   <ul>
      <%-- Display the key of the current item; that item
           is a Map.Entry --%>
      <li>Header name: <c:out value='${hv.key}'/></li>
   
      <%-- The value of the current item, which is
           accessed with the value method from 
           Map.Entry, is an array of strings 
           representing request header values, so
           we iterate over that array of strings --%>
      <c:forEach items='${hv.value}' var='value'>
           <li>Header Value: <c:out value='${value}'/></li>
      </c:forEach>
   </ul>
</c:forEach>

Unlike request parameters, request headers are rarely duplicated; instead, if multiple strings are specified for a single request header, browsers typically concatenate those strings separated by semicolons. Because of the sparsity of duplicated request headers, the header implicit object is usually preferred over headerValues.

Accessing Context Initialization Parameters

You can have only one value per context initialization parameter, so there's only one JSTL implicit object for accessing initialization parameters: initParam. Like the implicit objects for request parameters and headers, the initParam implicit object is a map. The map keys are context initialization parameter names and the corresponding values are the context initialization parameter values.

Figure 2–7 shows a JSP page that iterates over all the context initialization parameters and prints their values. That JSP page also accesses the parameters directly.

Figure 2-7Figure 2–7 Accessing Initialization Parameters with the initParam Implicit Object

Before we discuss the listing for the JSP page shown in Figure 2–7, let's look at the deployment descriptor, listed in Listing 2.16, which defines two context initialization parameters: com.acme.invaders.difficulty and com.acme.invaders. gameLevels.

Listing 2.16 WEB-INF/web.xml

<?xml version="1.0" encoding="ISO-8859-1"?>

<!DOCTYPE web-app
  PUBLIC "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN"
  "http://java.sun.com/j2ee/dtds/web-app_2.3.dtd">

<web-app>
   <!-- Application-wide default values for the Acme Invaders
        online game -->
   <context-param>
      <param-name>com.acme.invaders.difficulty</param-name>
      <param-value>18</param-value>
   </context-param>

   <context-param>
      <param-name>com.acme.invaders.gameLevels</param-name>
      <param-value>33</param-value>
   </context-param>

   <welcome-file-list>
      <welcome-file>
         index.jsp
      </welcome-file>
   </welcome-file-list>
</web-app>	

The context initialization parameters defined above are accessed by the JSP page shown in Figure 2–7 and listed in Listing 2.17.

Listing 2.17 Accessing Context Initialization Parameters

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<html>
   <head>
      <title>Context Initialization Parameters</title>
   </head>

   <body>
      <%@ taglib uri='http://java.sun.com/jstl/core' prefix='c' %>

      <font size='5'>
         Iterating Over Context Initialization Parameters:
      </font><p>

<%-- Loop over the JSTL initParam implicit object,
           which is a map --%>
<c:forEach items='${initParam}' var='parameter'>	
 <ul>
            <%-- Display the key of the current item, which
                 corresponds to the name of the init param --%>
            <li>Name: <c:out value='${parameter.key}'/></li>

            <%-- Display the value of the current item, which
                 corresponds to the value of the init param --%>
            <li>Value: <c:out value='${parameter.value}'/></li>
         </ul>
      </c:forEach>

      <font size='5'>
         Accessing Context Initialization Parameters Directly:
      </font><p>

      Difficulty: 
      <c:out value='${initParam["com.acme.invaders.difficulty"]}'/>

      Game Levels: 
      <c:out value='${initParam["com.acme.invaders.gameLevels"]}'/>

   </body>
</html>	

The preceding JSP page uses the <c:forEach> action to iterate over the key/value pairs stored in the initParam map. The body of that action displays each key/value pair.

In the example discussed in "Accessing Request Parameters" on page 65, we accessed a request parameter by name like this: ${paramValues. languages}. In the preceding JSP page, can we access an initialization parameter in a similar fashion with the initParam implicit object? The answer is yes, but in this case we have a problem because the initialization parameter name has . characters, which have special meaning to the expression language. If we try to access the com.acme.invaders.difficulty parameter like this: ${initParam.com.acme.invaders.difficulty}, the expression

language will interpret that expression as an object's property named difficulty, which is not the interpretation we want.

The solution to this difficulty is to use the [] operator, which evaluates an expression and turns it into an identifier; for example, you can access the com.acme.invaders.difficulty initialization parameter like this: ${initParam["com.acme.invaders.difficulty"]}. See "A Closer Look at the [] Operator" on page 56 for more information about the [] operator.

Accessing Cookies

It's not uncommon to read cookies in JSP pages, especially cookies that store user-interface-related preferences. The JSTL expression language lets you access cookies with the cookie implicit object. Like all JSTL implicit objects, the cookie implicit object is a map.15 That map's keys represent cookie names, and the values are the cookies themselves.

Figure 2–8 shows a JSP page that reads cookie values, using the cookie implicit object.

Figure 2-8Figure 2–8 Accessing Cookies with the cookie Implicit Object


The JSP page shown in Figure 2–8 uses the cookie implicit object to iterate over all cookies and also accesses Cookie objects and their values directly. That JSP page is invoked with the URL /cookieCreator, which is mapped to a servlet that creates cookies. That servlet, after creating cookies, forwards to the JSP page shown in Figure 2–8. Listing 2.18 lists the Web application's deployment descriptor, which maps the URL /cookieCreator to the CookieCreatorServlet class.

Listing 2.18 WEB-INF/web.xml

<?xml version="1.0" encoding="ISO-8859-1"?>

<!DOCTYPE web-app
  PUBLIC "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN"
  "http://java.sun.com/j2ee/dtds/web-app_2.3.dtd">

<web-app>
   <servlet>
      <servlet-name>cookieCreator</servlet-name>
      <servlet-class>CookieCreatorServlet</servlet-class>
   </servlet>

   <servlet-mapping>
      <servlet-name>cookieCreator</servlet-name>
      <url-pattern>/cookieCreator</url-pattern>
   </servlet-mapping>
</web-app>	

The CookieCreatorServlet class is listed in Listing 2.19.

Listing 2.19 WEB-INF/classes/CookieCreatorServlet.java

import java.io.IOException;
import javax.servlet.*;
import javax.servlet.http.*;

public class CookieCreatorServlet extends HttpServlet {
   public void doGet(HttpServletRequest request,
                     HttpServletResponse response)
                     throws IOException, ServletException {
      String[] cookieNames = {"acme.userName", "acme.password",
                              "acme.lastAccessDate"};
      String[] cookieValues = {"ronw", "iuo82wer", "2002-03-08"};

      // Create cookies and add them to the HTTP response
      for(int i=0; i < cookieNames.length; ++i) {
         Cookie cookie = new Cookie(cookieNames[i], 
                                    cookieValues[i]); 
         response.addCookie(cookie);
      }

      // Forward the request and response to cookies.jsp
      RequestDispatcher rd = 
         request.getRequestDispatcher("cookies.jsp");
         rd.forward(request, response);
   }
}	

The cookie creator servlet creates three cookies and adds them to the response before forwarding to cookies.jsp. That JSP page is listed in Listing 2.20.

Listing 2.20 cookies.jsp

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<html>
   <head>
      <title>Cookies</title>
   </head>

   <body>
      <%@ taglib uri='http://java.sun.com/jstl/core' prefix='c' %>

      <p><font size='5'>
         Iterating over Cookies:
      </font><p>	
 <%-- Loop over the JSTL cookie implicit object, which is a 
           map. If there are no cookies, the <c:forEach> action
           does nothing. --%>
      <c:forEach items='${cookie}' var='mapEntry'>
         <ul>
            <%-- The mapEntry's key references the cookie name --%>
            <li>Cookie Name: <c:out value='${mapEntry.key}'/></li>

            <%-- The mapEntry's value references the Cookie
                 object, so we show the cookie's value --%>
            <li>Cookie Value: 
                <c:out value='${mapEntry.value.value}'/></li>
         </ul>
      </c:forEach>

      <p><font size='5'>
         Accessing Cookies Directly:
      </font><p>

      Cookie Objects:
      <ul>
         <li>
            User Name: <c:out value='${cookie["acme.userName"]}'/>
         </li>
         <li>
            Password:  <c:out value='${cookie["acme.password"]}'/>
         </li>
      </ul>

      Cookie Values:
      <ul>
         <li>
            User Name: 
            <c:out value='${cookie["acme.userName"].value}'/>
         </li>
         <li>
            Password:  
            <c:out value='${cookie["acme.password"].value}'/>
         </li>
      </ul>
   </body>
</html>	

The preceding JSP page uses the <c:forEach> action to iterate over the entries contained in the cookie map. For each entry, the body of the <c:forEach> action displays the cookie's name and value. Notice that cookie values are accessed with the expression ${mapEntry.value.value}. The map entry's value is a cookie, which also has a value property.

The rest of the JSP page accesses cookie objects and their values directly. Because the cookie names contain . characters, they cannot be used as identifiers, so the preceding JSP page uses the [] operator to directly access cookies and their values.

Accessing Scoped Attributes

Since we started discussing JSTL implicit objects at "Implicit Objects" on page 64, we've seen how to access four types of objects:

  • Request parameters
  • Request headers
  • Context initialization parameters
  • Cookies

In addition to the specific types listed above, you can access any type of object that's stored in one of the four JSP scopes: page, request, session, or application. The expression language provides one implicit object for each scope:

  • pageScope
  • requestScope
  • sessionScope
  • applicationScope

Remember from our discussion in "Identifiers" on page 43 that identifiers refer to scoped variables; for example, the expression ${name} refers to a scoped variable named name. That scoped variable can reside in page, request, session, or application scope. The expression language searches those scopes, in that order, for scoped variables.

The implicit objects listed above let you explicitly access variables stored in a specific scope; for example, if you know that the name scoped variable resides in session scope, the expression ${sessionScope.name} is equivalent to ${name}, but the latter unnecessarily searches the page and request scopes before finding the name scoped variable in session scope. Because of that unnecessary searching, ${sessionScope.name} should be faster than ${name}.

The scope implicit objects listed above—pageScope, requestScope, sessionScope, and applicationScope—are also handy if you need to iterate over attributes stored in a particular scope; for example, you might look for a timestamp attribute in session scope. The scope implicit objects give you access to a map of attributes for a particular scope.

Figure 2–9 shows a Web application that displays all of the attributes from the scope of your choosing. The top picture in Figure 2–9 shows a JSP page that lets you select a scope, and the bottom picture shows a JSP page that lists the attributes for the selected scope.

Figure 2-9Figure 2–9 Accessing Scoped Variables for a Specific Scope with the pageScope Implicit Object


The JSP page shown in the top picture in Figure 2–9 is listed in Listing 2.21.

Listing 2.21 Choosing a Scope

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<html>
   <head>
      <title>Select a Scope</title>
   </head>

   <body>
      <form action='show_scope_attributes.jsp'>
         Select a scope:
         <select name='scope'>
            <option value='page'>page</option>
            <option value='request'>request</option>
            <option value='session'>session</option>
            <option value='application'>application</option>
         </select>

         <p><input type='submit' value='Show Scope Attributes'/>
      </form>
   </body>
</html>	

The preceding JSP page creates an HTML form that lets you select a scope. That form's action is show_scope_attributes.jsp, which is listed in Listing 2.22.

Listing 2.22 Showing Scoped Variables for a Specific Scope

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<html>
   <head>
      <title>Scoped Variables</title>
   </head>

   <body>
      <%@ taglib uri='http://java.sun.com/jstl/core' prefix='c' %>

      <%-- Set a page-scoped attribute named scope to 
           pageScope, requestScope, sessionScope, or
           applicationScope, depending on the value of a
           request parameter named scope --%>
      <c:choose>
         <c:when test='${param.scope == "page"}'>
            <c:set var='scope' value='${pageScope}'/>
         </c:when>
         <c:when test='${param.scope == "request"}'>
            <c:set var='scope' value='${requestScope}'/>
         </c:when>
         <c:when test='${param.scope == "session"}'>
            <c:set var='scope' value='${sessionScope}'/>
         </c:when>
         <c:when test='${param.scope == "application"}'>
            <c:set var='scope' value='${applicationScope}'/>
         </c:when>
      </c:choose>

      <font size='5'>
         <c:out value='${param.scope}'/>-scope attributes:
      </font><p>

      <%-- Loop over the JSTL implicit object, stored in the
           page-scoped attribute named scope that was set above.
           That implicit object is a map --%>
      <c:forEach items='${scope}' var='p'>
         <ul>
            <%-- Display the key of the current item, which
                 represents the parameter name --%>
            <li>Parameter Name: <c:out value='${p.key}'/></li>

            <%-- Display the value of the current item, which
                 represents the parameter value --%>
            <li>Parameter Value: <c:out value='${p.value}'/></li>
         </ul>
      </c:forEach>
   </body>
</html>	

The preceding JSP page is passed a request parameter named scope whose value is "page", "request", "session", or "application". The JSP page creates a page-scoped variable, also named scope, and sets it to the appropriate JSTL implicit object—pageScope, requestScope, sessionScope, or applicationScope—based on the scope request parameter. Then the JSP page loops over that implicit object and displays each scoped variable's name and value.

Accessing JSP Page and Servlet Properties

Now that we've seen how to access request parameters and headers, initialization parameters, cookies, and scoped variables, the JSTL implicit objects have one more feature to explore: accessing servlet and JSP properties, such as a request's protocol or server port, or the major and minor versions of the servlet API your container supports. You can find out that information and much more with the pageContext implicit object, which gives you access to the request, response, session, and application (also known as the servlet context). Useful properties for the pageContext implicit object are listed in Table 2.6.

Table 2.6 pageContext Properties

Property

Type

Description

request

ServletRequest

The current request

response

ServletResponse

The current response

servletConfig

ServletConfig

The servlet configuration

servletContext

ServletContext

The servlet context (the application)

session

HttpSession

The current session


The pageContext properties listed in Table 2.6 give you access to a lot of information; for example, you can access a client's host name like this: ${pageContext.request.remoteHost}, or you can access the session ID like this: ${pageContext.session.id}.

The following four tables list useful request, response, session, and application properties, all of which are available through the pageContext implicit object.

Table 2.7 pageContext.request Properties

Property

Type

Description

characterEncoding

String

The character encoding for the request body

contentType

String

The MIME type of the request body

locale

Locale

The user's preferred locale

locales

Enumeration

The user's preferred locales

new

boolean

Evaluates to true if the server has created a session, but the client has not yet joined

protocol

String

The name and version of the protocol for the request; for example: HTTP/1.1

remoteAddr

String

The IP address of the client

remoteHost

String

The fully qualified host name of the client, or the IP address if the host name is undefined

scheme

String

The name of the scheme used for the current request; i.e.: HTTP, HTTPS, etc.

serverName

String

The host name of the server that received the request

serverPort

int

The port number that the request was received on

secure

boolean

Indicates whether this was made on a secure channel such as HTTPS


Table 2.8 pageContext.response Properties

Property

Type

Description

bufferSize

int

The buffer size used for the response

characterEncoding

String

The character encoding used for the response body

locale

Locale

The locale assigned to the response

committed

boolean

Indicates whether the response has been committed


Table 2.9 session Properties

Property

Type

Description

creationTime

long

The time the session was created (in milliseconds since January 1, 1970, GMT)

id

String

A unique session identifier

lastAccessedTime

long

The last time the session was accessed (in milliseconds since January 1, 1970, GMT)

maxInactiveInterval

int

The time duration for no activities, after which the session times out


Table 2.10 pageContext.servletContext Properties

Property

Type

Description

majorVersion

int

The major version of the Servlet API that the container supports

minorVersion

int

The minor version of the Servlet API that the container supports

serverInfo

Set

The name and version of the servlet container

servletContextName

String

The name of the Web application specified by the display-name attribute in the deployment descriptor


The JSP page shown in Figure 2–10 accesses some of the information available in the preceding tables: the request port, protocol, and locale; the response locale; the session ID and maximum inactive interval; and the servlet API version supported by the JSP container.

Figure 2-10Figure 2–10 Using the pageContext Implicit Object

The JSP page shown in Figure 2–10 is listed in Listing 2.23.

Listing 2.23 Accessing Servlet and JSP Properties

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<html>
   <head>
      <title>Using the pageContext Implicit Object</title>
   </head>

   <body>
      <%@ taglib uri='http://java.sun.com/jstl/core' prefix='c' %>

      <%-- Show Request Information --%>
      <font size='5'>Request Information</font><p>

         <%-- Use the request object to show the server port and
                protocol --%>
The current request was made on <b>port 
         <c:out value='${pageContext.request.serverPort}'/></b>	
 with this <b>protocol:
         <c:out value='${pageContext.request.protocol}'/></b>.<br>

         <%-- Use the request object to show the user's preferred
              locale --%>
         The request <b>locale</b> is 
         <b><c:out value='${pageContext.request.locale}'/>.</b>

         <p>

      <%-- Show Response Information --%>
      <font size='5'>Response Information</font><p>

         The response <b>locale</b> is 
         <b><c:out value='${pageContext.response.locale}'/>.</b>

         <%-- Use the response object to show whether the response
              has been committed --%>
         The <b>response
         <c:choose>
            <c:when test='${pageContext.response.committed}'>
               has
            </c:when>

            <c:otherwise>
               has not
            </c:otherwise>
         </c:choose>   
         </b> been committed.

         <p>

      <%-- Show Session Information --%>
      <font size='5'>Session Information</font><p>

         Session ID: 
         <b><c:out value='${pageContext.session.id}'/></b><br>
         Max Session Inactive Interval:<b>
         <c:out 
            value='${pageContext.session.maxInactiveInterval}'/> 
         </b>seconds.

         <p>

      <%-- Show Application Information --%>
      <font size='5'>Application Information</font><p>
	
 <%-- Store the servlet context in a page-scoped variable
              named app for better readability --%>
         <c:set var='app' value='${pageContext.servletContext}'/>

         <%-- Use the application object to show the major and
              minor versions of the servlet API that the container
              supports --%>
         Your servlet container supports version<b> 
         <c:out 
            value='${app.majorVersion}.${app.minorVersion}'/></b>
         of the servlet API.
   </body>
</html>	

The preceding JSP page accesses request, response, session, and application properties, using the pageContext implicit object. The end of that JSP page creates a page-scoped variable named app that references the servlet context (meaning the application). That page-scoped variable is subsequently used to access the Servlet API version supported by the JSP container. Sometimes it's convenient, for the sake of readability, to store a reference to one of the objects listed in Table 2.6 on page 82 in a page-scoped variable, as does the preceding JSP page.

InformIT Promotional Mailings & Special Offers

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Overview


Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about products and services that can be purchased through this site.

This privacy notice provides an overview of our commitment to privacy and describes how we collect, protect, use and share personal information collected through this site. Please note that other Pearson websites and online products and services have their own separate privacy policies.

Collection and Use of Information


To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including:

Questions and Inquiries

For inquiries and questions, we collect the inquiry or question, together with name, contact details (email address, phone number and mailing address) and any other additional information voluntarily submitted to us through a Contact Us form or an email. We use this information to address the inquiry and respond to the question.

Online Store

For orders and purchases placed through our online store on this site, we collect order details, name, institution name and address (if applicable), email address, phone number, shipping and billing addresses, credit/debit card information, shipping options and any instructions. We use this information to complete transactions, fulfill orders, communicate with individuals placing orders or visiting the online store, and for related purposes.

Surveys

Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites. Participation is voluntary. Pearson collects information requested in the survey questions and uses the information to evaluate, support, maintain and improve products, services or sites, develop new products and services, conduct educational research and for other purposes specified in the survey.

Contests and Drawings

Occasionally, we may sponsor a contest or drawing. Participation is optional. Pearson collects name, contact information and other information specified on the entry form for the contest or drawing to conduct the contest or drawing. Pearson may collect additional personal information from the winners of a contest or drawing in order to award the prize and for tax reporting purposes, as required by law.

Newsletters

If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email information@informit.com.

Service Announcements

On rare occasions it is necessary to send out a strictly service related announcement. For instance, if our service is temporarily suspended for maintenance we might send users an email. Generally, users may not opt-out of these communications, though they can deactivate their account information. However, these communications are not promotional in nature.

Customer Service

We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form.

Other Collection and Use of Information


Application and System Logs

Pearson automatically collects log data to help ensure the delivery, availability and security of this site. Log data may include technical information about how a user or visitor connected to this site, such as browser type, type of computer/device, operating system, internet service provider and IP address. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

Web Analytics

Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson (but not the third party web trend services) to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.

Cookies and Related Technologies

This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site.

Do Not Track

This site currently does not respond to Do Not Track signals.

Security


Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.

Children


This site is not directed to children under the age of 13.

Marketing


Pearson may send or direct marketing communications to users, provided that

  • Pearson will not use personal information collected or processed as a K-12 school service provider for the purpose of directed or targeted advertising.
  • Such marketing is consistent with applicable law and Pearson's legal obligations.
  • Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.
  • Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn.

Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider. Marketing preferences may be changed at any time.

Correcting/Updating Personal Information


If a user's personally identifiable information changes (such as your postal address or email address), we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at customer-service@informit.com and we will process the deletion of a user's account.

Choice/Opt-out


Users can always make an informed choice as to whether they should proceed with certain services offered by InformIT. If you choose to remove yourself from our mailing list(s) simply visit the following page and uncheck any communication you no longer want to receive: www.informit.com/u.aspx.

Sale of Personal Information


Pearson does not rent or sell personal information in exchange for any payment of money.

While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to NevadaDesignatedRequest@pearson.com.

Supplemental Privacy Statement for California Residents


California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice. The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services.

Sharing and Disclosure


Pearson may disclose personal information, as follows:

  • As required by law.
  • With the consent of the individual (or their parent, if the individual is a minor)
  • In response to a subpoena, court order or legal process, to the extent permitted or required by law
  • To protect the security and safety of individuals, data, assets and systems, consistent with applicable law
  • In connection the sale, joint venture or other transfer of some or all of its company or assets, subject to the provisions of this Privacy Notice
  • To investigate or address actual or suspected fraud or other illegal activities
  • To exercise its legal rights, including enforcement of the Terms of Use for this site or another contract
  • To affiliated Pearson companies and other companies and organizations who perform work for Pearson and are obligated to protect the privacy of personal information consistent with this Privacy Notice
  • To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency.

Links


This web site contains links to other sites. Please be aware that we are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of each and every web site that collects Personal Information. This privacy statement applies solely to information collected by this web site.

Requests and Contact


Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information.

Changes to this Privacy Notice


We may revise this Privacy Notice through an updated posting. We will identify the effective date of the revision in the posting. Often, updates are made to provide greater clarity or to comply with changes in regulatory requirements. If the updates involve material changes to the collection, protection, use or disclosure of Personal Information, Pearson will provide notice of the change through a conspicuous notice on this site or other appropriate way. Continued use of the site after the effective date of a posted revision evidences acceptance. Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions.

Last Update: November 17, 2020