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解决java.lang.NoClassDefFoundError错误的方法
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好端端辛苦做的项目 突然jsp页面打不开。报错如下
<!DOCTYPE html><html><head><title>Apache Tomcat/8.0.29 - Error report</title><style type="text/css">H1 {font-family:Tahoma,Arial,sans-serif;color:white;background-color:#525D76;font-size:22px;} H2 {font-family:Tahoma,Arial,sans-serif;color:white;background-color:#525D76;font-size:16px;} H3 {font-family:Tahoma,Arial,sans-serif;color:white;background-color:#525D76;font-size:14px;} BODY {font-family:Tahoma,Arial,sans-serif;color:black;background-color:white;} B {font-family:Tahoma,Arial,sans-serif;color:white;background-color:#525D76;} P {font-family:Tahoma,Arial,sans-serif;background:white;color:black;font-size:12px;}A {color : black;}A.name {color : black;}.line {height: 1px; background-color: #525D76; border: none;}</style> </head><body><h1>HTTP Status 500 - javax.servlet.ServletException: java.lang.NoClassDefFoundError: performance/WMac</h1><div class="line"></div><p><b>type</b> Exception report</p><p><b>message</b> <u>javax.servlet.ServletException: java.lang.NoClassDefFoundError: performance/WMac</u></p><p><b>description</b> <u>The server encountered an internal error that prevented it from fulfilling this request.</u></p><p><b>exception</b></p><pre>org.apache.jasper.JasperException: javax.servlet.ServletException: java.lang.NoClassDefFoundError: performance/WMac org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:555) org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:461) org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:396) org.apache.jasper.servlet.JspServlet.service(JspServlet.java:340) javax.servlet.http.HttpServlet.service(HttpServlet.java:729) org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)</pre><p><b>root cause</b></p><pre>javax.servlet.ServletException: java.lang.NoClassDefFoundError: performance/WMac org.apache.jasper.runtime.PageContextImpl.doHandlePageException(PageContextImpl.java:909) org.apache.jasper.runtime.PageContextImpl.handlePageException(PageContextImpl.java:838) org.apache.jsp.net_005finfo_jsp._jspService(net_005finfo_jsp.java:486) org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70) javax.servlet.http.HttpServlet.service(HttpServlet.java:729) org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:438) org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:396) org.apache.jasper.servlet.JspServlet.service(JspServlet.java:340) javax.servlet.http.HttpServlet.service(HttpServlet.java:729) org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)</pre><p><b>root cause</b></p><pre>java.lang.NoClassDefFoundError: performance/WMac org.apache.jsp.net_005finfo_jsp._jspService(net_005finfo_jsp.java:365) org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70) javax.servlet.http.HttpServlet.service(HttpServlet.java:729) org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:438) org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:396) org.apache.jasper.servlet.JspServlet.service(JspServlet.java:340) javax.servlet.http.HttpServlet.service(HttpServlet.java:729) org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)</pre><p><b>root cause</b></p><pre>java.lang.ClassNotFoundException: performance.WMac org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1333) org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1167) org.apache.jasper.servlet.JasperLoader.loadClass(JasperLoader.java:125) org.apache.jasper.servlet.JasperLoader.loadClass(JasperLoader.java:62) org.apache.jsp.net_005finfo_jsp._jspService(net_005finfo_jsp.java:365) org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70) javax.servlet.http.HttpServlet.service(HttpServlet.java:729) org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:438) org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:396) org.apache.jasper.servlet.JspServlet.service(JspServlet.java:340) javax.servlet.http.HttpServlet.service(HttpServlet.java:729) org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)</pre><p><b>note</b> <u>The full stack trace of the root cause is available in the Apache Tomcat/8.0.29 logs.</u></p><hr class="line"><h3>Apache Tomcat/8.0.29</h3></body></html>报错信息是java.lang.NoClassDefFoundError这是因为“引用自定义标签库出现异常”，根治此疑难杂症的方法
1、
（1）项目根目录下新建一个libs文件夹
（2）把要加的包放到这个目录下
（3）右键 Build Path-> Use as source folder
（4）在jar包上右键->add to build path
（注意，上面的是libs，不是lib）
3.
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