················很简单的问题·················

在Java里面，只要是类，都可以有构造函数，如果没有构造的话，系统会默认一个给你

解决方案 »

  1.   

    运行时老是出现如下的错误：
    Error: 500
    Location: /examples/jsp/MJspUserPreferences.jsp
    Internal Servlet Error:java.lang.NoSuchMethodError
    at org.apache.jasper.runtime.PageContextImpl.getAttribute(PageContextImpl.java:236)
    at jsp.MJspUserPreferences_8._jspService(MJspUserPreferences_8.java:60)
    at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:119)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:840)
    at org.apache.tomcat.facade.ServletHandler.doService(ServletHandler.java:574)
    at org.apache.tomcat.core.Handler.invoke(Handler.java:322)
    at org.apache.tomcat.core.Handler.service(Handler.java:235)
    at org.apache.tomcat.facade.ServletHandler.service(ServletHandler.java:485)
    at org.apache.tomcat.core.ContextManager.internalService(ContextManager.java:917)
    at org.apache.tomcat.core.ContextManager.service(ContextManager.java:833)
    at org.apache.tomcat.modules.server.Http10Interceptor.processConnection(Http10Interceptor.java:176)
    at org.apache.tomcat.util.net.TcpWorkerThread.runIt(PoolTcpEndpoint.java:494)
    at org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:516)
    at java.lang.Thread.run(Thread.java:484)搞不懂，郁闷中......
      

  2.   

    java bean必须要构造函数？
      

  3.   

    jsp中有这么一行（在<body>标签下第二行）：<%@ include file="Header.jsp" %>去掉它