el表达式之operators的应用实例讲解。
el_operators.jsp文件：
<%@ page language=”java” import=”java.util.*” pageEncoding=”utf-8″%>
<!DOCTYPE HTML PUBLIC “-//W3C//DTD HTML 4.01 Transitional//EN”>
<html>
<head>
<title>My JSP ‘el_operators.jsp’ starting page</title>
</head>
<body>
<table border=”1″>
<thead>
<td><b>EL表达式</b></td>
<td><b>运算符运算结果</b></td>
<td><b>EL表达式</b></td>
<td><b>运算符运算结果</b></td>
</thead>
<tr>
<td>\${11 }</td>
<td>${11 }</td>
<td>\${11+2 }</td>
<td>${ 11+2}</td>
</tr>
<tr>
<td>\${ 5.5+1.2}</td>
<td>${5.5+1.2 }</td>
<td>\${5*5 }</td>
<td>${5*5 }</td>
</tr>
<tr>
<td>\${ 2-1}</td>
<td>${2-1 }</td>
<td>\${2/1 }</td>
<td>${ 2/1}</td>
</tr>
<tr>
<td>\${2*2 }</td>
<td>${2*2 }</td>
<td>\${ 2%2}</td>
<td>${ 2%2}</td>
</tr>
<tr>
<td>\${2==2?2:0 }</td>
<td>${2==2?2:0 }</td>
<td>\${1<2?1:0 }</td>
<td>${1<2?1:0 }</td>
</tr>
</table>
</body>
</html>
| EL Operators |
|---|
<%– div and mod are alternatives to / and % –%>
| Arithmetic Operators | Relational Operators | ||
|---|---|---|---|
| Expression | Result | Expression | Result |
| \${3+2-1} | ${3+2-1} <%– Addition/Subtraction –%> | \${1<2} | ${1<2} <%– Numerical comparison –%> |
| \${“1″+2} | ${“1″+2} <%– String conversion –%> | \${“a”<”b”} | ${“a”<”b”} <%– Lexical comparison –%> |
| \${1 + 2*3 + 3/4} | ${1 + 2*3 + 3/4} <%– Mult/Div –%> | \${2/3 >= 3/2} | ${2/3 >= 3/2} <%– >= –%> |
| \${3%2} | ${3%2} <%– Modulo –%> | \${3/4 == 0.75} | ${3/4 == 0.75} <%– Numeric = –%> |
| \${(8 div 2) mod 3} | ${(8 div 2) mod 3} <%– Compares with “equals” but returns false for null –%> | \${null == “test”} | ${null == “test”} |
| Logical Operators | empty Operator |
||
| Expression | Result | Expression | Result |
| \${(1<2) && (4<3)} | ${(1<2) && (4<3)} <%–AND–%> | \${empty “”} | ${empty “”} <%– Empty string –%> |
| \${(1<2) || (4<3)} | ${(1<2) || (4<3)} <%–OR–%> | \${empty null} | ${empty null} <%– null –%> |
| \${!(1<2)} | ${!(1<2)} <%– NOT -%> <%– Handles null or empty string in request param –%> | \${empty param.blah} | ${empty param.blah} |