Head First Servlets and JSP phần 2 ppsx

+HUH·VWKH-63 Here weÕre getting an attribute from the request object.. We commented it out so that you could still see it here.Add an attribute to the request object for the JSP to use..

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<form method=ÓPOS TÓ action=ÓSelectBeer.doÓ>

But the browser pr epends Ò/Beer-v1/Ó

on to the reques t, because tha

tÕs where the client reques t is coming f

rom In other words, the ÒSelectBeer.doÓ in the HTML is r elative to the URL of the page its on In this case, r

elative to the root of the web app, Ò/Beer-v1Ó.

The host

server

root.

WeÕll use doPost to

Adjust this to match your own directory path to your system!

Everything after Òtomcat/Ó will be the same.

Use the -d option to tell the compiler to put the class Þ le into the classes directory within the correct package structure

Your class Þ le will end up in /beerV1/classes/com/example/web/.

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public class BeerSelect extends HttpServlet {

l (third) version, the advice will be pr inted from a JSP instead of the servlet.

DonÕt forget the imp ort for the package that BeerExp ert is in.

WeÕre modifying the or iginal servlet, not making a new cl ass.

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Some standard Java sitting inside <% %> tags (this is known as scriptlet code).

Some standard HTML (which is known as Òtemplate textÓ in the JSP world).

+HUH·VWKH-63

Here weÕre getting an attribute from the request object A little later in the book, weÕll explain everything about attributes and how we managed

to get the request object

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Now that the JSP is going to produce the output, we should remove the test output from the servlet We commented it out so that you could still see it here.

Add an attribute to the request object for the JSP to use Notice the JSP is looking for ÒstylesÓ.

Instantiate a request dispatcher for the JSP.

HereÕs what you should see !

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(Each request runs in a separate thr ead.)

Your servlet cl ass no-arg cons

tructor runs (you should N OT write a cons

tructor; just use the comp iler-supplied def

ault).

Called only ONCE in the servletÕs life, and must complete before Container can call service().

Container calls to give the servlet

a chance to clean up before the servlet is killed (i.e., made ready for garbage collection) Like init(), itÕs called only once.

This is where the servlet spends most of its life.

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rom the Servlet interface You will probably NEVER extend this class yourself Most

of your servletÕs Òservlet behaviorÓ comes from this class.

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