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15.4 Example: Showing Raw Servlet and JSP Output

377

Also note that this type of file inclusion differs from that supported by

the JSP 

include

 directive discussed in Section 12.1 (Including Files at

Page Translation Time). There, the actual source code of JSP files was

included in the page by use of the 

include

 directive, whereas the 

include

method of 

RequestDispatcher

 just includes the result of the specified

resource. On the other hand, the 

jsp:include

 action discussed in Section

12.2 (Including Files at Request Time) has behavior similar to that of the

include

 method, except that 

jsp:include

 is available only from JSP

pages, not from servlets.

15.4 Example: Showing Raw 

Servlet and JSP Output

When you are debugging servlets or JSP pages, it is often useful to see the

raw HTML they generate. To do this, you can choose  View Source  from

the browser menu after seeing the result. Alternatively, to set HTTP

request headers and see the HTTP response headers in addition to HTML

source, use the 

WebClient

 program shown in Section 2.10 (WebClient:

Talking to Web Servers Interactively). For quick debugging, another option

is available: create a servlet that takes a URL as input and creates an output

page showing the HTML source code. Accomplishing this task relies on the

fact that the HTML 

TEXTAREA

 element ignores all HTML markup other

than the 

 tag. So, the original servlet generates the top of a

Web page, up to a 

</b></font></pre></span>
<span name = "INTRA" style='top:861px; left:442px' class="ft1"><pre><font face='Arial'> tag. Then, it includes the output of what </font></pre></span>
<span name = "INTRA" style='top:884px; left:191px' class="ft1"><pre><font face='Arial'>ever URL was specified in the query data. Next, it continues with the Web</font></pre></span>
<span name = "INTRA" style='top:907px; left:191px' class="ft1"><pre><font face='Arial'>page, starting with a </font></pre></span>
<span name = "INTRA" style='top:908px; left:360px' class="ft0"><pre><font face='Arial'><b>

 tag. Of course, the servlet will fail if it

tries to display a resource that contains the 

 tag, but the point

here is the process of including files.

Listing 15.10 shows the servlet that accomplishes this task, and Listing

15.11 shows an HTML form that gathers input and sends it to the servlet.

Figures 15 3 and 15 4 show the results of the HTML form and servlet,

respectively.

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

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