jsp中jstl标签库core全解析
一：:
查看c.tld可知：
Like<%=...>,butforexpressions.
out
org.apache.taglibs.standard.tag.rt.core.OutTag
JSP
Expressiontobeevaluated.
value
true
true
Defaultvalueiftheresultingvalueisnull.
default
false
true
Determineswhethercharacters<,>,&,'',"inthe
resultingstringshouldbeconvertedtotheir
correspondingcharacterentitycodes.Defaultvalueis
true.
escapeXml
false
true
向界面输出value值（可输出特殊字符）：
属性解析：value:输出的值（el表达式，字符串）
escapeXml:是否将特殊字符转化，默认true
default:value值为null时输出
代码示例：
<%
pageContext.setAttribute("name","Tom");
pageContext.setAttribute("name2","Tom");
%>
${name2}
out会将<>解析成&qt;>，这样保证界面原样输出，而一般的el表达式不转化<>，hyml会解析颜色
二：
Setstheresultofanexpressionevaluationina''scope''
set
org.apache.taglibs.standard.tag.rt.core.SetTag
JSP
Nameoftheexportedscopedvariabletoholdthevalue
specifiedintheaction.Thetypeofthescopedvariableis
whatevertypethevalueexpressionevaluatesto.
var
false
false
Expressiontobeevaluated.
value
false
true
java.lang.Object
Targetobjectwhosepropertywillbeset.Mustevaluateto
aJavaBeansobjectwithsetterpropertyproperty,ortoa
java.util.Mapobject.
target
false
true
Nameofthepropertytobesetinthetargetobject.
property
false
true
Scopeforvar.
scope
false
false
设置属性：相当于setAttribute();
属性搭配一：var:存储容器中的属性变量名
value:属性值
属性搭配二：target:容器中的一个对象
property:对象属性名
value:属性值
scope:容器的种类（四种，二种搭配可选可不选）
代码示例：
${aa},${requestScope.aa}
三：
Removesascopedvariable(fromaparticularscope,ifspecified).
remove
org.apache.taglibs.standard.tag.common.core.RemoveTag
empty
Nameofthescopedvariabletoberemoved.
var
true
false
Scopeforvar.
scope
false
false
在容器中移除var值属性，默认全部容器
属性：var:容器中的属性值
scope:指定的容器
代码示例：
${aa}
四：
Simpleconditionaltag,whichevalutesitsbodyifthe
suppliedconditionistrueandoptionallyexposesaBoolean
scriptingvariablerepresentingtheevaluationofthiscondition
if
org.apache.taglibs.standard.tag.rt.core.IfTag
JSP
Thetestconditionthatdetermineswhetheror
notthebodycontentshouldbeprocessed.
test
true
true
boolean
Nameoftheexportedscopedvariableforthe
resultingvalueofthetestcondition.Thetype
ofthescopedvariableisBoolean.
var
false
false
Scopeforvar.
scope
false
false
判断test属性值真假，是否执行里面的代码
属性：test：一个返回boolean值得表达式
var：存储test返回值的变量名
scope:存储var变量的容器
代码示例：
10}"var="boo">
dfdfdfdf
NOooooo
五：
Simpleconditionaltagthatestablishesacontextfor
mutuallyexclusiveconditionaloperations,markedby
and
choose
org.apache.taglibs.standard.tag.common.core.ChooseTag
JSP
Subtagofthatincludesitsbodyifits
conditionevalutesto''true''
when
org.apache.taglibs.standard.tag.rt.core.WhenTag
JSP
Thetestconditionthatdetermineswhetherornotthe
bodycontentshouldbeprocessed.
test
true
true
boolean
Subtagofthatfollowstags
andrunsonlyifallofthepriorconditionsevaluatedto
''false''
otherwise
org.apache.taglibs.standard.tag.common.core.OtherwiseTag
JSP
一种类似于swich-case结构
:无属性，标记开始
:相当于case可重复属性test:会返回为boolea值得表达式
:无属性，相当于defaule语句
代码示例：
=90}">
优秀
=80}">
良好
=70}">
中等
不行
六：普通循环：
增强for循环：
Thebasiciterationtag,acceptingmanydifferent
collectiontypesandsupportingsubsettingandother
functionality
forEach
org.apache.taglibs.standard.tag.rt.core.ForEachTag
org.apache.taglibs.standard.tei.ForEachTEI
JSP
Collectionofitemstoiterateover.
items
false
true
java.lang.Object
java.lang.Object
Ifitemsspecified:
Iterationbeginsattheitemlocatedatthe
specifiedindex.Firstitemofthecollectionhas
index0.
Ifitemsnotspecified:
Iterationbeginswithindexsetatthevalue
specified.
begin
false
true
int
Ifitemsspecified:
Iterationendsattheitemlocatedatthe
specifiedindex(inclusive).
Ifitemsnotspecified:
Iterationendswhenindexreachesthevalue
specified.
end
false
true
int
Iterationwillonlyprocesseverystepitemsof
thecollection,startingwiththefirstone.
step
false
true
int
Nameoftheexportedscopedvariableforthe
currentitemoftheiteration.Thisscoped
variablehasnestedvisibility.Itstypedepends
ontheobjectoftheunderlyingcollection.
var
false
false
Nameoftheexportedscopedvariableforthe
statusoftheiteration.Objectexportedisoftype
javax.servlet.jsp.jstl.core.LoopTagStatus.Thisscopedvariablehasnested
visibility.
varStatus
false
false
第一套普通循环相当于：for(var=begin;var<=end;var+=step)
属性：begin:起始值
end:结尾值
step:步长值
var:表示目前的循环值
第二套属性搭配相当于：for(var:items)
属性：items:集合/数组的引用名
var:每一项的变量名
varStatus=""该属性可加可不加：有俩个下级变量：
index:记录当前下标值items-var型从0开始begin-end-step型从begin开始
count:记录当前遍历数
代码示例：
<%
Listlist2=newArrayList();
list2.add("aa1111");
list2.add("bb2222");
list2.add(200);
list2.add(100);
request.setAttribute("lis2",list2);
%>
${aa},
<%
Mapmap=newHashMap();
map.put("name","Rose");
map.put("age",55);
map.put("tel","13566668888");
pageContext.setAttribute("m",map);
%>
${im.key}=${im.value}
<%
Stringstrs[]={"aaa","bbb","111","2222"};
pageContext.setAttribute("strs",strs);
%>
${str},,
看看ForEach标签中的varStatus属性---idx.index是元素的下标(从0开始)，idx.count是元素的序号(从1开始计数)
${str}----index=${idx.index}count=${idx.count}
${i}--${idx.count}
七：分隔符拆分
从begin-end间，以step长度分割
Iteratesovertokens,separatedbythesupplieddelimeters
forTokens
org.apache.taglibs.standard.tag.rt.core.ForTokensTag
JSP
Stringoftokenstoiterateover.
items
true
true
java.lang.String
java.lang.String
Thesetofdelimiters(thecharactersthat
separatethetokensinthestring).
delims
true
true
java.lang.String
Iterationbeginsatthetokenlocatedatthe
specifiedindex.Firsttokenhasindex0.
begin
false
true
int
Iterationendsatthetokenlocatedatthe
specifiedindex(inclusive).
end
false
true
int
Iterationwillonlyprocesseverysteptokens
ofthestring,startingwiththefirstone.
step
false
true
int
Nameoftheexportedscopedvariableforthe
currentitemoftheiteration.Thisscoped
variablehasnestedvisibility.
var
false
false
Nameoftheexportedscopedvariableforthe
statusoftheiteration.Objectexportedisof
type
javax.servlet.jsp.jstl.core.LoopTag
Status.Thisscopedvariablehasnested
visibility.
varStatus
false
false
型：
属性：items:要分割的表达式
delims:分隔符
var:分割的每一项
代码示例：
${str}
八：相当于动态导入
RetrievesanabsoluteorrelativeURLandexposesitscontents
toeitherthepage,aStringin''var'',oraReaderin''varReader''.
import
org.apache.taglibs.standard.tag.rt.core.ImportTag
org.apache.taglibs.standard.tei.ImportTEI
JSP
TheURLoftheresourcetoimport.
url
true
true
Nameoftheexportedscopedvariableforthe
resource''scontent.Thetypeofthescoped
variableisString.
var
false
false
Scopeforvar.
scope
false
false
Nameoftheexportedscopedvariableforthe
resource''scontent.Thetypeofthescoped
variableisReader.
varReader
false
false
Nameofthecontextwhenaccessingarelative
URLresourcethatbelongstoaforeign
context.
context
false
true
Characterencodingofthecontentattheinput
resource.
charEncoding
false
true
属性：url:导入的资源路径（可访问）
代码示例：
九：链接，具有重写url技术
CreatesaURLwithoptionalqueryparameters.
url
org.apache.taglibs.standard.tag.rt.core.UrlTag
JSP
Nameoftheexportedscopedvariableforthe
processedurl.Thetypeofthescopedvariableis
String.
var
false
false
Scopeforvar.
scope
false
false
URLtobeprocessed.
value
false
true
NameofthecontextwhenspecifyingarelativeURL
resourcethatbelongstoaforeigncontext.
context
false
true
属性：value:资源路径（可访问）
代码示例
?
1
I18N演示
十：重定向
RedirectstoanewURL.
redirect
org.apache.taglibs.standard.tag.rt.core.RedirectTag
JSP
TheURLoftheresourcetoredirectto.
url
false
true
NameofthecontextwhenredirectingtoarelativeURL
resourcethatbelongstoaforeigncontext.
context
false
true
属性：url:资源路径（可访问）
代码示例
<%--
--%>
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