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EL表达式
判断Map是否为空和map的取值
判断Map是否为空和map的取值
1. Map<String, Object> fieldMap
<c:if test=”${fieldMap[‘realname’].showstatus == 1}”>
action中的代码
private Map<String, String> msgs = new HashMap<String, String>
msgs.put(“loginError”, “验证码错误”);
jsp页面中的代码：
<script type=”text/javascript”>
var msgTip = “${msgs[‘loginError’]}”;
alert(msgTip);
</script>
————————————————————————————————————————————–
注意事项：map名后不要加点，直接是[]
key要用单引号
在js中写，要在整个取值外面加双引号
private Map<String, String> msgs = new HashMap<String, String>
msgs.put(“loginError”, “验证码错误”);
jsp页面中的代码：
<script type=”text/javascript”>
var msgTip = “${msgs[‘loginError’]}”;
alert(msgTip);
</script>
————————————————————————————————————————————–
注意事项：map名后不要加点，直接是[]
key要用单引号
在js中写，要在整个取值外面加双引号
1.在JSP页面中引入sun的核心标签库
<%
@ taglib uri
=
“
http://java.sun.com/jstl/core_rt
“
prefix
=
“
c
“
%>
2.在JSP页面中引入sun的函数标签库
<%
@ taglib uri
=
“
http://java.sun.com/jsp/jstl/functions
“
prefix
=
“
fn
“
%>
3.判断是否为空
<
c:if
test
=”${!empty map}”
>
</
c:if
>
4.判断长度大于0
<
c:if
test
=”${fn:length(map)>0}”
>
</
c:if
>
注：fn:length(obj)，对于空对象也会返回0
5.例子：将request传入的hashmap显示在表格中
<%
@ page language
=
“
java
“
contentType
=
“
text/html; charset=utf-8
“
pageEncoding
=
“
utf-8
“
import
=
“
java.util.HashMap,java.util.Iterator
“
%>
<%
@ taglib uri
=
“
http://java.sun.com/jstl/core_rt
“
prefix
=
“
c
“
%>
<!–
引入sun的核心标签库
–>
<%
@ taglib uri
=
“
http://java.sun.com/jsp/jstl/functions
“
prefix
=
“
fn
“
%>
<!–
引入sun的函数标签库
–>
<!
DOCTYPE html PUBLIC “-//W3C//DTD HTML 4.01 Transitional//EN” “http://www.w3.org/TR/html4/loose.dtd”
>
<
html
>
<
head
>
<
meta
http-equiv
=”Content-Type”
content
=”text/html; charset=utf-8″
>
<
title
>显示jsp传递的参数-使用标签库
</
title
>
</
head
>
<
body
>
<
center
><
h1
>传递的参数
</
h1
></
center
>
<
hr
/>
<
c:choose
>
<
c:when
test
=”${fn:length(requestScope.paramMap)>0}”
>
<
table
border
=”1″
>
<
tr
><
th
>参数名
</
th
><
th
>参数值
</
th
></
tr
>
<
c:forEach
items
=”${requestScope.paramMap}”
var
=”map”
>
<
tr
><
td
>${map.key}
</
td
><
td
>${map.value}
</
td
></
tr
>
</
c:forEach
>
</
table
>
</
c:when
>
<
c:otherwise
>
<
c:out
value
=”没有在request中传递paramMap属性”
/><
br
/>
<
p
>paramMap大小为:${fn:length(requestScope.paramMap)}
</
p
>
</
c:otherwise
>
</
c:choose
>
</
body
>
</
html
>
@ page language
=
“
java
“
contentType
=
“
text/html; charset=utf-8
“
pageEncoding
=
“
utf-8
“
import
=
“
java.util.HashMap,java.util.Iterator
“
%>
<%
@ taglib uri
=
“
http://java.sun.com/jstl/core_rt
“
prefix
=
“
c
“
%>
<!–
引入sun的核心标签库
–>
<%
@ taglib uri
=
“
http://java.sun.com/jsp/jstl/functions
“
prefix
=
“
fn
“
%>
<!–
引入sun的函数标签库
–>
<!
DOCTYPE html PUBLIC “-//W3C//DTD HTML 4.01 Transitional//EN” “http://www.w3.org/TR/html4/loose.dtd”
>
<
html
>
<
head
>
<
meta
http-equiv
=”Content-Type”
content
=”text/html; charset=utf-8″
>
<
title
>显示jsp传递的参数-使用标签库
</
title
>
</
head
>
<
body
>
<
center
><
h1
>传递的参数
</
h1
></
center
>
<
hr
/>
<
c:choose
>
<
c:when
test
=”${fn:length(requestScope.paramMap)>0}”
>
<
table
border
=”1″
>
<
tr
><
th
>参数名
</
th
><
th
>参数值
</
th
></
tr
>
<
c:forEach
items
=”${requestScope.paramMap}”
var
=”map”
>
<
tr
><
td
>${map.key}
</
td
><
td
>${map.value}
</
td
></
tr
>
</
c:forEach
>
</
table
>
</
c:when
>
<
c:otherwise
>
<
c:out
value
=”没有在request中传递paramMap属性”
/><
br
/>
<
p
>paramMap大小为:${fn:length(requestScope.paramMap)}
</
p
>
</
c:otherwise
>
</
c:choose
>
</
body
>
</
html
>
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