Errata for Head First Servlets and JSP

implicit variable is cookie not cookies.

Note from the Author or Editor:
Correct

http://jakarta.apache.org/site/bin/index.cgi SHOULD BE http://jakarta.apache.org/site/binindex.cgi

The 3rd bullet point reads... "A typical servlet is a class that extends HttpServletRequest" should be: "A typical servlet is a class that extends HttpServlet"

In the top figure, labeled "Web Server," move the form.html file into the Container box.

- Its directory structure should be /WEB-INF/classes/com/model should have been - Its directory structure should be /WEB-INF/classes/com/example/model

The code for servlet version three on page 89 shows the following line as commented out: // out.println("<br>Got beer color " + c); However, that line never appeared in the servlet version two code and should be added (uncommented out and in bold) just above the following line on page 84: BeerExpert be = new BeerExpert(); AUTHOR: This is how I would reorganize these two code examples in a future printing of the book. First, on pg 84 move all of the code that (a) retrieves the 'color' parameter and (b) retrieve the results of the beer search from the BeerExpert to the top of the doPost method. Put the code to (a) set content type, (b) retrieve the Writer, and (c) generate the response at the bottom of the doPost method. Second, on pg 89, reproduce the code structure from above, but now comment out the bottom half which is being replaced by the code to (a) set the 'styles' attribute, (b) create the RequestDispatcher, and (c) forward to the view ReqDisp.

The final sentence says: "So each time my doGet() or doPost() runs, it's in a separate method" SHOULD READ "So each time my doGet() or doPost() runs, it's in a separate thread."

ServletResponse Interface shown has two setContentType() methods. One of them should be getContentType()

The line: "getParameter()" should be: "getParameter(String)"

"POST is considered idempotent by the HTTP 1.1 spec." should be: "POST is not considered idempotent by the HTTP 1.1 spec."

The Input stream from request.getInputStream() will only contain the body, not the header

A. response.setHeader(CONTENT-LENGTH, "numBytes"); B. response.setHeader("CONTENT-LENGTH", "numBytes"); should be: A. response.setHeader(CONTENT-LENGTH, "1024"); B. response.setHeader("CONTENT-LENGTH", "1024");

The source code for the TestInitParams servlet is missing an import. Add: import java.util.*; Without the import the code won't compile because the Enumeration class is used.

"setAttribute(String)" should read: "setAttribute(String, Object)"

enumeration getAttributeNames() should be: Enumeration getAttributeNames()

ServletRequest interface box shows method name of getContextType(), where it should be getContentType().

In the list of methods for HttpSession Interface, the setMaxInactiveInterval is shown without arguments. setMaxInactiveInterval() should instead be written as setMaxInactiveInterval(int interval)

out.println("test context attributes<br>"); should be: out.println("test session attributes<br>");

Which statements about listeners defined in the javax.servlet package are true? should be: "Which statements about listeners are true?"

When I call the getOutputStream method on the response object and use the RequestDispatcher to perform a forward I get and IllegalStateException even if I do not write to or flush the output stream. For this reason I think choice D is also correct.

Note from the Author or Editor:
OK O'Reilly: check option D

out.println("<a href="" + response.encodeURL("/BeerTest.do")); should be read: out.println("<a href="" + response.encodeURL("/BeerTest.do") + "">Click Me</a>");

delete the line: String foo = (String) session.getAttribute("foo"); out.println("Foo: " + foo); should read: out.println("Foo: " + session.getAttribute("foo"));

There should be a if (cookies!=null) { } after Cookie[] cookies = request.getCookies();

"...can also choose to implement a readObject() method, called by the VM whenever an object is serialized, and a writeObject() method, called when an object is deserialized." Should read: "...can also choose to implement a writeObject() method called by the VM whenever an object is serialized, and a readObject() method, called when an object is deserialized."

The Bang! box on pg 261 is erroneous and should be dropped altogther.

Answer C left off a vital part of the sentence when it was copied from the Servlet specification. The Servlet specification says: 'Any object bound into a session is available to any other servlet that belongs to the same ServletContext and handles a request identified as being a part of the same session.' Answer C leaves off the final part of the sentence: 'and handles a request identified as being a part of the same session.' Without this answer C is not correct.

Yes, you CAN get servlet init parameters from a servlet.... should read: Yes, you CAN get servlet init parameters from a JSP...

"...OR place a checkmark in the ignored column if scripting will be treated like other template text." should be: "...OR place a checkmark in the error column if scripting will cause a translation error." And change the "ignored" column title to "error". (323 *and* 326) code magnets; The code magnet should read <jsp:include page="foo.html"/> *not* <jsp:include file="foo.html"/>

AS IS: (Remember: scripting expressions are ALWAYS the argument to the out.write() method.) SHOULD BE: (Remember: scripting expressions are ALWAYS the argument to the out.print() method.)

The first variable is either ..., and the thing to the right of the dot is either a map value(if the first variable is a map) ... should be The first variable is either..., and the thing to the right of the dot is either a map key(if the first variable is a map) ...

The <jsp:include> standard action appears to do the same thing as the include standard action. should be: The <jsp:include> standard action appears to do the same thing as the include directive.

Sentence should end "but that's more obvious with the include directive.", not "page directive."

As the .jspf convention is not supported by default in Tomcat, the following mapping needs to be added to the application's web.xml for the example to work correctly: <servlet-mapping> <servlet-name>jsp</servlet-name> <url-pattern>*.jspf</url-pattern> </servlet-mapping>

"${list[list['listIdx']]}" should read: "${list[list[listIdx]]}"

The instructions indicate just jstl.jar file is required to run JSTL in Tomcat. You also need standard.jar from the webapps/jsp-examples/WEB-INF/lib/ directory.

... "target" attribute in the tag seems like it should work like "id" in the <jsp:setProperty>. should be: ... "target" attribute in the tag seems like it should work like "id" in the <jsp:useBean>.

Answer talks about using 'scope' attribute for c:set for 'var' or 'target'. Scope attribute is only meaningful for 'var'. Answer needs to be rewritten to remove any reference to the 'target' attribute.

The scope is optional, and like always - page is the default scope. should be: The scope is optional, and when not specified the attribute is removed from all scopes.

The JSP with the <jsp:include> last line </body></html should be </body></html>

the closing single-quote is in the wrong place <mine:advice user='<%= request.getAttribute("username")' %> /> should be: <mine:advice user='<%= request.getAttribute("username") %>' />

the sentence "the Container searches for tag files in four locations" needs a period at the end.

The 2nd sentence in the "BE the Container" paragraph should read "Assume that the tag handler prints the body of tag."

Says "What is the result if the thingsDontWork test is false?" should be: "What is the result if the thingsDontWork test is True?"

return type of doAfterBody() should be "int" instead of "void"

<%@ tag body-content="tagdependent" %> should be <%@ tag body-content="empty" %>

The code on Option E should be: String p = (String) pageContext.getRequest().getAttribute("param");

Option E cannot be correct because it assigns the return value of ServletRequest.getAttribute (an Object) to a String without a cast. The code on Option E should be: String p = (String) pageContext.getRequest().getAttribute("param");

The notes for options E and F should be swapped.

Option C should read: "The method that retrieves these parameters has a signature that returns an Object." (where "Object" should be in courier font to indicate the class name, not the generic concept)

"If you do NOT specify any <http-element>, then..." should read: "If you do NOT specify any <http-method>, then..."

The deployment descriptor on the right hand side of the page has two errors. First the closing and opening <web-app> tags should be dropped; this is all a single DD. Second, there should be only one <role-name> subelement in the <security-role> element. Remove the Member and Guest roles as they are not needed in this example.

The third missing piece, at the end of the 4th line of the DD section, has a "/" after the blank box. This "/" should be before the blank box.

The last line of the second step reads: "... until it reaches its chain. doFilter ()call." Should be: "... until it reaches its chain. doFilter() call."

streamUsed != pw should be: if ( (streamUsed != null) && (streamUsed == pw) ) {

streamUsed != servletGzipOS should be: if ( (streamUsed != null) && (streamUsed == servletGzipOS) ) {

"Given this method in an otherwise properly defined Filter implementation:" should be: "Given the class UserRequest is an implementation of HttpServletRequest, and given this method in an otherwise properly defined Filter implementation:"

The bullet "* should reduce duplicate code" should be deleted. It is not a feature of the design pattern described.