National Academy for Software Development

1
????????? ?? ??? ??????????
(Custom Tag Libraries)
Dreamix Ltd.
????? ?????
2
??????????

• ????? ?? ??????????????? ??????
• ??????? ??????????????
• ??? ??????? ?? ????????? ?? ????????????? ??????
• Java Handler
• JSP ??? ????
• ????????, ???? ?? ???, ??????????????? ??????.

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????? ?? Custom Tags

• ???????? ?? ??????????? JSP ???????
• ?????????? ?????????????
• ????? ? ??????? ?? ???? ??????, ???? ? ? ????????
  ???????
• ??????? ???????? ?? ?????????????
• JSP-?? ?????? ??-?????? ? ??????????
• ??????? ???????? ?? ???????????? ?? Java Web
  Frameworks

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??????? ??????????????

• ????? ?? ?? ??????????? ???? ????????
• ????? ?? ?????? ?????????? ??? ???????????
  ???????? (JSP)
• ????? ?? ????????? ?????? ?????? ???????? ?? JSP
  ?????????
• ????? ?? ??????????? ???? ? ????
• ????? ?? ?? ???????
• ????? ?? ???? ???? (body)

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??? ??????? Java ????

• Java ??????
• ???-? ???????????? java ????
• ?????? ?? JSPWriter ?????
• ???????? ??, ?????? ???-? ??????? ????? ?????????
  ????????
• ?????????? ?? ???????????? ?? ????????

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??? ??????? JSP ????

• JSP ??????
• ???? JSP 2.0
• ??????? ?? ? ???? ? ?????????? .tag
• ???????? JSP ?????????
• ???????? ??, ?????? ??? ?????? ???????? ????????
  ?? ??????? ??????
• ?????????? ?? ???????????? ?? JSP

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Custom Tag Libraries
Java ????
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??????????

• Java ????
• ??? ?? ???????????? ???????? ?? ???? ? ????? ??
  ????????
• ?????? ?? ???????????? javax.servlet.jsp.tagext.S
  impleTag
• ?????????? ?? ????????? javax.servlet.jsp.tagext.
  SimpleTagSupport
• ??? ??????????
• XML ????, ? ?????????? .tld
• ??????? ?? ????? ?? ????, ?????????? ?? ? java
  ??????

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??? ???? - ??????
package eu.dreamix.test.tags import
javax.servlet.jsp. import javax.servlet.jsp.tage
xt. import java.io. public class
SimpleGreetingTag
extends SimpleTagSupport public
void doTag() throws JspException,
IOException
JspWriter out getJspContext().getOut()
String greeting "Hello"
out.print(greeting)
10
??? ??????????

• ????? ?? XML-a e taglib
• ???????? ?? ??? ???????????? ltdescriptiongt,
  ltdisplay-namegt, lttlib-versiongt, lturigt,
  ltshort-namegt, lttaggt
• ????? ??????? ??? ?? ?????? ? tag ???????, ?????
  ???????
• description - ?????? ????????
• name ????? ?? ???-?
• tag-class ??????? ??? ?? ??? ?????
• body-content ?????? ???? ???? ??? ??????????
  ????? ????????? ? ?????????? ???

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??? ?????????? - ??????
lt?xml version"1.0" encoding"UTF-8" ?gt lttaglib
xmlns"http//java.sun.com/xml/ns/j2ee"
xmlnsxsi"http//www.w3.org/2001/XMLSchema-instan
ce" xsischemaLocation"http//java.sun.com/xml/n
s/j2ee http//java.sun.com/xml/ns/j2ee/web-jsptag
library_2_0.xsd" version"2.0"gt
lttlib-versiongt1.0lt/tlib-versiongt
ltshort-namegtTestTagslt/short-namegt
lturigthttp//dreamix.eu/web/tags/jwclt/urigt
lttaggt ltdescriptiongt Displays
a simple greeting message lt/descriptiongt
ltnamegtgreetinglt/namegt lttag-classgt
eu.dreamix.test.tags.SimpleGreetingTag
lt/tag-classgt ltbody-contentgtemptylt/
body-contentgt lt/taggt lt/taglibgt
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????????? ? JSP-??

• ?????? ?? ??? ???????????? (??? ??????)
• ?????? ?? ???? ?? .tld ???????????
• ?????? ?? URI-?? ?? ??? ???????????? (???????? ??
  lturigt ? taglib ????)

lt_at_ taglib uri"/WEB-INF/tlds/my-taglib.tld"
prefix"mytaglib" gt
lt_at_ taglib uri"http//dreamix.eu/web/tags/jwc"
prefix"mytaglib" gt
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??? ?????????? Java ????

• ????????????

SimpleGreetingTag
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????????

• ?? ????? ??????? xxx ?? ??? ?, ???????? ????? ?
  java ????? setXxx(? value)
• ??????
• ?? ?? ????????? ???-? ? ???????
• ? java ????? ?????? ?? ?????

ltprefixtagName attribute1"Test" /gt
public void setAttribute1(String value1)
doSomethingWith(value1)
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??????? Java ??????????
... ...
public class SimpleGreetingTag
extends SimpleTagSupport private String
person public void setPerson(String value)
this.person person public void
doTag() throws JspException,
IOException JspWriter out
getJspContext().getOut() String greeting
"Hello, " person out.print(greeting)
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???????? ??? ??????????

• ?? ????? ???????,tag ???????? ?????? ?? ???????
  ??????? attribute
• attribute ??????? 3 ????????
• name, ??? ?? ????????
• required, ???? ???????? ? ???????????? ???
  ???????? ?? ????
• rtexprvalue(truefalse), ??????? ???? ?????????
  ?? ???????? ???? ?? ? JSP ????? (lt?????gt) ???
  ? ???????? ??????.

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???????? TLD ??????
... lttaggt ltdescriptiongt Displays a
simple greeting message lt/descriptiongt
ltnamegtgreetinglt/namegt lttag-classgt
eu.dreamix.test.tags.SimpleGreetingTag
lt/tag-classgt ltbody-contentgtemptylt/body-content
gt ltattributegt ltnamegtpersonlt/namegt
ltrequiredgttruelt/requiredgt lt/attributegt lt/taggt

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??? ?????????? Java ????

• ????????????

????????
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Custom Tag Libraries
JSP ????
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????????????? ??????

• ??? Java ??????? ?? ??????????
• Java ????, ????? ???????????? doTag()
• ??? ?????????? (TLD)
• JSP, ? ????? ?? ??????? ??????????? ?? ???
  ????????????
• ??? JSP ??????? ?? ??????????
• JSP ??? (??? ????)
• JSP, ? ????? ?? ??????? ????????????, ?????????
  ??? ?????

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??? ???? - ??????
/WEB-INF/tags/greeting.tag
lt!-- Display greeging message --gt lth2gtHello! I'm
the simpliest tag in the world!!lt/h2gt

• ????????????, ? ????? ?? ?????? ???? ?? ?
  ??????????!
• ???? ?????? ?? ?? ?????? ?
  /WEB-INF/tags ??? ????????????? ?? ???

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????????? ?? ???-???? ? JSP
Greeting.jsp
... lt_at_ taglib tagdir"/WEB-INF/tags"
prefix"mytags" gt ... ltbodygt ...
ltmytagsgreeting /gt ... lt/bodygt

• ?????? uri ?? ???????? tagdir
• ?????? ?? ????????????, ????? ??????? ????????

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????????

• ?? ????? ??????? ?? ??????
  
• ? ???????? ?? ??? ?????

lt_at_ attribute name"XXX" required"(truefalse)"
gt
/WEB-INF/tags/greeting.tag
lt!-- Display greeging message --gt lt!--
Attributes--gt lt_at_ attribute name"location"
required"true" gt lth2gt Hello! I'm the simpliest
tag in the location!! lt/h2gt
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??? ?????????? Java ????

• ????????????

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?????? ? ????

• ?????? ??????????? ???? ?????? ??? ????
• ?????? ? ????

ltprefixtag attribute1"value1"/gt
ltprefixtagName attr1"value1"gt Scriptless JSP
content lt/prefixtagNamegt
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??? ???????????????????? ?? ???? ?? ???

• ltbody-contentgt

lttaggt ltnamegt...lt/namegt lttag-classgt...lt/tag
-classgt ltbody-contentgtscriptlesslt/body-content
gt lt/taggt

• ????????? ?????????
• empty ???-? ???? ???? (???? ? ?? ??? ?? ????????
• scriptless ????-? ???????? ????, ????? ???? JSP
  ????????? ????????
• tagdependent ?????? ?? ????????? ?? ????

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??????????? ?? ?????? -Java ???? ??????

• ??????? ?? getJspBody().invoke()
• invoke() ?????? ???? ???????? java.io.Writer
  ?????, ? ????? ?? ???????? ?????? ?? ????.
• invoke(null) ????????? ?????? ???????? ? JSP
  ??????????.

public void doTag() throws ... JspWriter
out getJspContext().getOut()
out.print("...") getJspBody().invoke(null)
out.print("...")
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?????? ? ???? JSP ????

• ???????? ?? ltjspdoBody /gt ?? ?? ?? ????????
  ??????.

/WEB-INF/tags/note.tag
lt_at_ attribute name"author" required"true"
gt lttable border"1"gt lttrgt ltthgtAuthorlt/thgt ltthgt
Notelt/thgt lt/trgt lttrgt lttdgtauthorlt/tdgt
lttdgtltjspdoBody /gtlt/tdgt lt/trgt lt/tablegt
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?????? ? ???? JSP ???? (2)
notes.jsp
ltmytagsnote author"Mojo Jojo"gt I will rule
the world ! lt/mytagsnotegt
Browser
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??? ?????????? Java ????

• ????????????

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??-?????? ???????????

• ?? ???????? ???????? ???
• ?????? ?? ????????? ?????? ?? ?????? ?? ??????
• ?????? ?????? ?? ??????? ???????
• ????????
• ???????? ?????? ?? ? ?? ??? ???????? ??? ?????
• ? ?????? ?????? ?? ????? ?????? ?? ????? ???????

32
???????? ?? ?????? ???

• ?????????? ?? ??????? ?? ???, ???????? ?? String
  ??? ????????
• setXXX ?????? ? ?????????? ??? (??? Object)
• rtexprvalue true
• ?????????? ?? ???? ???????? ???? EL ?????

lttagsloop items"someList" ... /gt
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???????? ?? ???? ? ??????

• ?? ?? ???????? ????? ????? ???????? ? ?????? ??
  ????
• ?????????? ??????
• key ????? (????) ?? ??????
• object ?????? ?????
• ?? ?? ???????? ?????? ? ??????
• ?????????? EL ????? key

getJspContext().setAttribute(key, object)
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Loop Tag Handler
public class LoopTagHandler extends
SimpleTagSupport private Collection items
private String var public void
setItems(Collection items) this.items
items public void setVar(String var)
this.var var
???????? ??????????
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Loop Tag Handler
... ???????????
public void doTag() throws JspException,
IOException
Iterator iter items.iterator() while
(iter.hasNext()) Object current
iter.next() //???????? ?? ???????
????? ? ?????? ?? ???? getJspContext().setAt
tribute(var, current) //???????????
?? ?????? ? JSP ??????????
getJspBody().invoke(null)
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??? ?????????? Java ????

• ????????????

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??????? ??????

• ?????? ??????????? ?? ???? ??? ?????? ?? ???????
  ?????????? (?????????)
• getParent() - ????? ??????????? ???
• findAncestorWithClass(this, OuterTag.class)
  ????? ????????? ??? ?? ??????? ??? (???
  ??????????)
• ?????? ?? ???????? If, Then ? Else ??????

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IfTag
public class IfTag extends SimpleTagSupport
private boolean test public void
setTest(boolean test) this.test test
public boolean getTest() return(test)
public void doTag() throws JspException,
IOException
getJspBody().invoke(null)
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ThenTag
public class ThenTag extends SimpleTagSupport
public void doTag() throws JspException,
IOException //
Get parent tag (if tag) IfTag ifTag
(IfTag)getParent() if (ifTag ! null)
// Decide whether to output body of then
if (ifTag.getTest()) getJspBody().invoke
(null) else String msg
"Error 'then' must be inside 'if'." throw new
JspTagException(msg)
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ElseTag
public class ElseTag extends SimpleTagSupport
public void doTag() throws JspException,
IOException
// Get parent tag (if tag) IfTag ifTag
(IfTag)getParent() if (ifTag ! null)
// Decide whether to output body of else if
(!ifTag.getTest()) getJspBody().invoke(null)
else String msg
"Error 'else' must be inside 'if'." throw new
JspTagException(msg)
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If Then Else - ??????

• ???????? ?????????

ltmytagsif test"lt Math.random() lt 0.5
gt"gt ltmytagsthengtHeadslt/mytagsthengt ltmytagsel
segtTailslt/mytagselsegt lt/mytagsifgt
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??????????

• ??????????????? ??????
• ????????? java ???? ?? JSP ??????????
• ?? ?????? JSP ?? ???????????
• ????? ?????????? ????? ????????? ?? ??
  ???????????
• ????????? ?? ?????? ???? ?? ???? ?????
• ??????? ???????? ?? ?????????????
• Online ??? ??????????
• http//jakarta.apache.org/taglibs/

43
????????? ?? ??? ??????????

• ????????