HTTP Status 500 -
--------------------------------------------
type Exception report
message
description The server encountered an internal error () that prevented it from fulfilling this request.
exception
org.apache.jasper.JasperException
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:372)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:292)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:236)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
root cause
java.lang.NullPointerException
soccertable.BlobBean.readBlob(BlobBean.java:155)
org.apache.jsp.categoryshow_jsp._jspService(categoryshow_jsp.java:107)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:94)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:324)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:292)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:236)
javax.servlet.http.HttpServlet.service(HttpServlet.java:802)
note The full stack trace of the root cause is available in the Apache Tomcat/5.0.28 logs.
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Apache Tomcat/5.0.28
------解决方案--------------------
从内置对象request中获得变量值为空，但是在后面代码中有通过此变量获得此变量的属性。如果变量为空，当获得空值的属性就会报空指针异常。
如：String aaa=request.getParameter( "*** ");
String类型的aaa获得后是空值
如果后面代码想从aaa执行一些操作时就会报错（如：aaa.split( "- ");)
因为是空值，空值没有任何属性。
这样报错异常为空指针异常。
大多空指针异常也是由于这样的失误造成，解决办法：判断是否为空然后进行操作。
代码迷推荐解决方案：The server encountered an internal error () that prevented it from fulfilling this request.,http://www.daimami.com/search?q=317