Use the optional Òv arÓ attribute when you want access to this value l ater.... Note: the exception implicit object is available ONLY to error pages with an explicitly-deÞ ned page dire
Trang 1Unlike the other t wo includes, the <c:import> url can be f
rom outside the web Container!
WKH F LPSRUW! WDJ
Trang 2Òhorse.htmlÓ and Òhorse.gifÓ are both on Server B, a completely different web server from the one with the JSP
(DonÕt forget: as with other include mechanisms, the thing you import should be an HTML fragment and NOT a complete page with opening and closing <html><body> tags.)
Trang 3as a new request parameter.
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Trang 4This page doesnÕt change a t all It doesnÕt care HOW the parameter got there, as long as itÕs ther e.
No slash, because NOW the tag has a body
Trang 7F VHWYDU ´ODVW´YDOXH ´+LGGHQ&XUVRU´!
F VHWYDU ´¿UVW´YDOXH ´&URXFKLQJ3L[HOV´!
F XUOYDOXH ´LQSXW&RPPHQWVMVS"¿UVW ^¿UVW` ODVW ^ODVW`´YDU ´LQSXW85/´!
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2EMEMBER
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MVS"ÀUVW &URXFKLQJ3L[HOV ODVW +LGGHQ&XUVRU
Uh-oh youÕre not supp osed to have spaces in a URL!
Yikes! Query string parameter s have
to be encoded spaces, f or example, must be replaced with a plus Ò+Ó sign.
Use the optional Òv arÓ attribute when you want access to this value l ater
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4HIS
F XUOYDOXH ´LQSXW&RPPHQWVMVS´YDU ´LQSXW85/´!
F SDUDPQDPH ´¿UVW1DPH´YDOXH ´^¿UVW`´!
F SDUDPQDPH ´ODVW1DPH´YDOXH ´^ODVW`´!
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no slash
.OW
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Now weÕre safe, because <c:param>
takes care of the encoding!
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Trang 9ConÞ rms for the Container, ÒY es, this IS
an ofÞ cially-designated error page.Ó
Tells the Container, ÒIf something goes wrong here, forward the request to errorPage.jspÓ.
The REQUEST was for ÒbadPage.jspÓ, but that page threw an exception, so the RESPONSE came from ÒerrorPage.jspÓ.
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Trang 10\RXDUHKHUH
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Trang 11The <location> MUST be rel ative to the web-app root/contex
t, which means it MUST start with a sl ash (This is true regardless of w
hether the error page is based on <error-code> or <exc eption-type>.)
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Trang 12Note: the exception implicit object is available ONLY to error pages with an explicitly-deÞ ned page directive:
<%@ page isErrorPage=ÓtrueÓ %>
In other words, conÞ guring an error page in the DD is not enough to make the Container give that page the implicit exception object!
Trang 13ANDANDMIGHT
AND
TAGCAUGHTEITHER OF
#WDJOLESUH¿[ ´F´XUL ´KWWS MDYDVXQFRPMVSMVWOFRUH´!
If this prints out, then we KNOW
we made it past the exception (which in this example, means we successfully caught the exception).
Trang 14This creates a new page-scop ed attribute named ÒmyExc eptionÓ, and assigns the exception object t o it.
Now thereÕs an attribute myException, and since itÕs a Throwable, it has a
has a getMessage() method).
Trang 16We didnÕt cover this one it lets
you iterate over tokens where YOU
give it the delimiter Works a lot
like StringTokenizer We also didnÕt
cover <c:redirect> and <c:out>, but
that gives you a wonderful excuse
to get the JSTL docs.
Trang 174,$ 4,$
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Trang 18This is the v ersion of the XML schema tha
t you use for JSP 2.0 DonÕt memor
ize it
just copy it int o your <taglib> element.
MANDATORY (the tag, not the v
alue)Ñ the develop er puts it in to decl are the version of the tag library.
REQUIRED! This is wha t you use inside the tag (example: <my:advic e>). REQUIRED ! This is how the
Container knows wha
t to call when someone uses the tag in a JSP.
If your tag has attributes, then one <attribute>
element per tag attribute is required.
The unique name we use
in the taglib directive!
REQUIRED! This says that the tag must NOT have anything in the body.
This says you MUST put a ÒuserÓ attribute in the tag.
This says the ÒuserÓ a ttribute can be a
r un t ime expr ession value (i.e
doesnÕt have to be a Str ing literal).
Optional, but a r eally good idea
MANDATORY; mainly for tools to use
Trang 19in the TLD is set to ÒtrueÓ for the user attribute
(Assume the ÒuserNameÓ attribute already exists.)
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This is the same tag you saw
on the previous page, but without the annotations.
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Trang 20The Container calls doT ag() when the JSP inv
okes the tag using the name decl ared in the TLD.
The Container calls this method t
o set the value from the tag attribute It uses Jav
aBean property naming conventions to Þ gure out tha
t a ÒuserÓ attribute should be sent to the setUser() method.
Our own interna l method.
Trang 21If thereÕs no <rtexprv alue>, the default value is f alse.
Trang 22It has to be an expression, not just a scriplet
So it must have the Ò=Ó sign in there and no semicolon on the end.
Trang 23<jsp:attribute> tags donÕt count as Òbody contentÓ.
The tag must N OT have a body.
The tag must N OT have scripting elements (scr
iptlets, scripting expressions, and decl arations), but i
t CAN have template text and EL and cus
tom and standard actions.
The tag body is treated as plain text, so the EL is NOT evaluated and tags/actions are not triggered.
The tag body can have anything that can go inside a JSP.
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Trang 24\RXDUHKHUH
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deploy and run a web app that uses the tag.
Trang 25#WDJOLESUH¿[ ´F´XUL ´KWWS MDYDVXQFRPMVSMVWOFRUH´!
This LOOKS like a URL t o
a web resource, but i tÕs not
ItÕs just a name tha t happens
Trang 27#WDJO XUL ´:
Trang 29FKDSWHU
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Trang 30F VHWYDU ´XVHU/HYHO´VFRSH ´VHVVLRQ´ ´IRR´!
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of the tag instead of as an a ttribute.
The <c:otherwise> tag is optiona l.
Trang 31FKDSWHU
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Trang 32!SSUMINGWHICH
Trang 33FKDSWHU
!VALUEASSOCIATED
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Trang 57< /span>:HE&RQWDLQHU 6LPSOH7DJFODVV 7DJ+DQGOHU2EMHFW
Your tag handlerÕs...
iptlets, scripting expressions, and decl arations), but i
t CAN have template text and EL and cus
tom and standard actions.
The