Java Tutorial/JSTL/Exception
Версия от 17:44, 31 мая 2010; (обсуждение)
Содержание
Catch Error
index.jsp
<%@ taglib prefix="c" uri="http://java.sun.ru/jstl/core" %>
<%@ taglib prefix="fmt" uri="http://java.sun.ru/jstl/fmt" %>
<h1>Peter"s Junk-Mail Service</h1>
<c:if test="${param.submitted}">
<c:if test="${empty param.name}" var="noName" />
<c:if test="${empty param.email}" var="noEmail" />
<c:if test="${empty param.age}" var="noAge" />
<c:catch var="ageError">
<fmt:parseNumber var="parsedAge" value="${param.age}" />
<c:if test="${parsedAge < 13}" var="youngAge" />
</c:catch>
<c:if test="${not empty ageError}" var="badAge" />
<c:if
test="${not (noName or noEmail or noAge or badAge or youngAge)}">
<c:set value="${param.name}" var="name" scope="request"/>
<c:set value="${param.email}" var="email" scope="request"/>
<c:set value="${param.age}" var="age" scope="request"/>
<jsp:forward page="spamFormHandler.jsp" />
</c:if>
</c:if>
<form method="post">
<P>
Thanks for signing up for our junk-mail service.
Once you submit your information on the form below,
you"ll begin to receive all the "spam" you ever wanted.
</p>
<input type="hidden" name="submitted" value="true" />
<P>
Enter your name:
<input type="text" name="name"
value="<c:out value="${param.name}"/>" />
<br />
<c:if test="${noName}">
<small><font color="red">
Note: you must enter a name
</font></small>
</c:if>
</p>
<P>
Enter your email address:
<input type="text" name="email"
value="<c:out value="${param.email}"/>" />
<br />
<c:if test="${noEmail}">
<small><font color="red">
Note: you must enter an email address
</font></small>
</c:if>
</p>
<P>
Enter your age:
<input type="text" name="age" size="3"
value="<c:out value="${param.age}"/>" />
<br />
<c:choose>
<c:when test="${noAge}">
<small><font color="red">
Note: you must enter your age
</font></small>
</c:when>
<c:when test="${badAge}">
<small><font color="red">
Note: I couldn"t decipher the age you typed in
</font></small>
</c:when>
<c:when test="${youngAge}">
<small><font color="red">
Note: You"re too young to receive pornographic
junk mail. Please grow older and try again.
</font></small>
</c:when>
</c:choose>
</p>
<input type="submit" value="Sign up" />
</form>
Catch Exception
<%@ taglib uri="http://java.sun.ru/jstl/core" prefix="c" %>
<html>
<head>
<title>Catch an Exception?</title>
</head>
<body>
<c:catch var="e">
<c:set var="x" value="10" scope="page" />
<c:set var="y" value="five" scope="page" />
10 divided by 0 is
<c:out value="${10/0}" />
<br />
</c:catch>
<c:if test="${e!=null}">The caught exception is:
<c:out value="${e}" />
<br />
</c:if>
<c:if test="${e==null}">No exception was thrown
<br />
</c:if>
</body>
</html>
Catch Exception and Print Out Exception Message
<%@ taglib uri="http://java.sun.ru/jstl/core" prefix="c" %>
<html>
<head>
<title>Catch an Exception</title>
</head>
<body>
<c:catch var="e">
<c:set var="x" value="10" scope="page" />
<c:set var="y" value="five" scope="page" />
x divided by y is
<c:out value="${x/y}" />
<br />
</c:catch>
<br />
<c:if test="${e!=null}">The caught exception is:
<c:out value="${e}" />
<br />
</c:if>
<c:if test="${e==null}">No exception was thrown
<br />
</c:if>
</body>
</html>
C:Catch Exception
<%@ taglib uri="http://java.sun.ru/jstl/core" prefix="c" %>
<html>
<head>
<title>The c:catch action</title>
</head>
<body>
<h1>So you want to make a call from your cell phone?!</h1>
<h2>Checking the signal strength...</h2>
<c:catch var="signalException">
<%
int i= (int) (Math.random() * 10);
if (i < 5 )
throw new NullPointerException(); %>
</c:catch>
<c:choose>
<c:when test="${signalException != null}">
Exception!!!
</c:when>
<c:otherwise>
No Exception!!!
</c:otherwise>
</c:choose>
</body>
</html>
Generate Exception in c:out
<%@ taglib uri="http://java.sun.ru/jstl/core" prefix="c" %>
<html>
<head>
<title>Throw an Exception</title>
</head>
<body>10 divided by 0 is
<c:out value="${10/0}" />
<br />
</body>
</html>
