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232

Chapter 10 JSP Scripting Elements

could put a normal Web page: no compiling, no packages, and no user

CLASSPATH

 settings. However, although your personal environment doesn't

need any special settings, the server still has to be set up with access to the

servlet and JSP class files and the Java compiler. For details, see your server's

documentation or Section 1.5 (Installation and Setup). 

Although what you write often looks more like a regular HTML file than a

servlet, behind the scenes, the JSP page is automatically converted to a nor 

mal servlet, with the static HTML simply being printed to the output stream

associated with the servlet's 

service

 method. This translation is normally

done the first time the page is requested. To ensure that the first real user

doesn't get a momentary delay when the JSP page is translated into a servlet

and compiled, developers can simply request the page themselves after first

installing it. Many Web servers also let you define aliases so that a URL that

appears to reference an HTML file really points to a servlet or JSP page. 

Depending on how your server is set up, you can even look at the source

code for servlets generated from your JSP pages. With Tomcat 3.0, you need to

change the 

isWorkDirPersistent

 attribute from 

false

 to 

true

 in

install_dir/server.xml

. After that, the code can be found in

install_dir/work/port number

. With the JSWDK 1.0.1, you need to

change the 

workDirIsPersistent

 attribute from 

false

 to 

true

 in

install_dir/webserver.xml

. After that, the code can be found in

install_dir/work/%3Aport number%2F

. With the Java Web Server, 2.0 the

default setting is to save source code for automatically generated servlets. They

can be found in 

install_dir/tmpdir/default/pagecompile/jsp/_JSP

.

One warning about the automatic translation process is in order. If you

make an error in the dynamic portion of your JSP page, the system may not

be able to properly translate it into a servlet. If your page has such a fatal

translation time error, the server will present an HTML error page describ 

ing the problem to the client. Internet Explorer 5, however, typically replaces

server generated error messages with a canned page that it considers friend 

lier. You will need to turn off this  feature  when debugging JSP pages. To do

so with Internet Explorer 5, go to the Tools menu, select Internet Options,

choose the Advanced tab, and make sure  Show friendly HTTP error mes 

sages  box is not checked.

Core Warning

When debugging JSP pages, be sure to turn off Internet Explorer's 

 friendly  HTTP error messages.

Second edition of this book: www.coreservlets.com; Sequel: www.moreservlets.com.

Servlet and JSP training courses by book's author: courses.coreservlets.com.