学习JSP遇到的问题 ---标准标志库

学习JSP遇到的问题 ---标准标志库

- 中国WEB开发者网络 (http://www.webasp.net)
-- 技术教程 (http://www.webasp.net/article/)
--- 学习JSP遇到的问题 ---标准标志库 (http://www.webasp.net/article/26/25991.htm)

-- 作者：未知
-- 发布日期： 2005-08-18

我刚刚开始学习JSP ，最近看到了标准标志库这一节，问题还真的不少，在CSDN上发布了一下我的疑问，居然只有一个人回复。晕。

现在再说这两个问题吧：

我的环境是 Eclipse 3.1 + jdk1.5 + tomcat 5

1.xmlbuddy_2.0.56总是装不上。在单位和家，一样的开发环境（我保证完全一样，我用的相同的安装程序），在单位就一下子成功了。在家就一直不成功。郁闷。我以为是xmlbuddy_2.0.56.的版本不对，换了N个还是不可以。

2.使用标准标志库后，总出现这样的问题JSP Parsing Error:The absolute uri: http://java.sun.com/jsp/jstl/core cannot be resolved in either web.xml or the jar files deployed with this application. 相同的两个JSP文件有的时候却没有这种问题老外的一些网站说，这是TOMCAT的servlet-api.jar有和。。。的有冲突（好像是这个文件），事实上我觉得不像。我给大家看我的两个例子吧:

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">

<%@ page contentType="text/html; charset=gb2312" language="java" %>

<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
<jsp:useBean id = "cal" class="jstlTest.CalendarBean"/>

<html>
<head>
<title>测试网页</title>
</head>
<body>

The time is currently: 
<c:out value = "${cal.date}"/>

<c:set var ="hour" value = "${cal.hour}" scope = "request"/>

<c:choose>
<c:when test = "${hour >0 && hour <= 11}">
Good Morning!
</c:when>

<c:when test = "${hour >=12 && hour <= 17}">
Good Afternoon!
</c:when>

<c:otherwise>
Good Evening!
</c:otherwise>

</c:choose>
</body>
</html>

这个文件没有任何问题。但是看下一：

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN">
<%@ page contentType="text/html; charset=gb2312" language="java"%>

<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
<%@ taglib uri="http://java.sun.com/jsp/jstl/fmt" prefix="fmt" %>

<fmt:setLocale value = "en_US"/>

<jsp:useBean id = "cal" class="jstlTest.CalendarBean"/>

<html>
<head>
<title>测试网页</title>
</head>
<body>

The time is currently: 
<c:out value = "${cal.date}"/>

<c:set var ="hour" value = "${cal.hour}" scope = "request"/>

<c:if test = "${hour >0 && hour <= 11}">
Good Morning!
</c:if>

<c:if test = "${hour >=12 && hour <= 17}">
Good Afternoon!
</c:if>

<c:if test = "${hour >=18}">
Good Evening!
</c:if>

<c:out value = "${hour}"/>
</body>
</html>
这个页面就会出现上面的问题.JSP Parsing Error:The absolute uri: http://java.sun.com/jsp/jstl/core cannot be resolved in either web.xml or the jar files deployed with this application.

3.关于标志库的XML部分。页面代码如下:

<%@ page contentType="text/html; charset=gb2312" language="java" %>
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
<%@ taglib uri="http://java.sun.com/jsp/jstl/xml" prefix="x" %>

<c:import var="rssFeed" url="/jstlTest/book.xml"/>
<x:parse var="rss" xml="${rssFeed}"/>
<x:set select="$book/book/title" var="rss" scope="session" />
<x:out select="$rss"/>

出错:Content is not allowed in prolog.

javax.servlet.ServletException: javax.servlet.jsp.JspException: Content is not allowed in prolog.

        org.apache.jasper.runtime.PageContextImpl.doHandlePageException(PageContextImpl.java:844)

        org.apache.jasper.runtime.PageContextImpl.handlePageException(PageContextImpl.java:781)

        org.apache.jsp.isJSTLxml_jsp._jspService(org.apache.jsp.isJSTLxml_jsp:91)

        org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:97)

        javax.servlet.http.HttpServlet.service(HttpServlet.java:802)

        org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:322)

        org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:291)

        org.apache.jasper.servlet.JspServlet.service(JspServlet.java:241)

        javax.servlet.http.HttpServlet.service(HttpServlet.java:802)

root cause

org.xml.sax.SAXParseException: Content is not allowed in prolog.

        com.sun.org.apache.xerces.internal.parsers.DOMParser.parse(Unknown Source)

        com.sun.org.apache.xerces.internal.jaxp.DocumentBuilderImpl.parse(Unknown Source)

        org.apache.taglibs.standard.tag.common.xml.ParseSupport.parseInputSource(ParseSupport.java:227)

        org.apache.taglibs.standard.tag.common.xml.ParseSupport.parseInputSourceWithFilter(ParseSupport.java:193)

        org.apache.taglibs.standard.tag.common.xml.ParseSupport.parseReaderWithFilter(ParseSupport.java:199)

        org.apache.taglibs.standard.tag.common.xml.ParseSupport.parseStringWithFilter(ParseSupport.java:206)

        org.apache.taglibs.standard.tag.common.xml.ParseSupport.doEndTag(ParseSupport.java:138)

        org.apache.jsp.isJSTLxml_jsp._jspx_meth_x_parse_0(org.apache.jsp.isJSTLxml_jsp:135)

        org.apache.jsp.isJSTLxml_jsp._jspService(org.apache.jsp.isJSTLxml_jsp:74)

        org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:97)

        javax.servlet.http.HttpServlet.service(HttpServlet.java:802)

        org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:322)

        org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:291)

        org.apache.jasper.servlet.JspServlet.service(JspServlet.java:241)

        javax.servlet.http.HttpServlet.service(HttpServlet.java:802)

晕。

google上关于这个的也很少。

独学真的很郁闷。

webasp.net