request.getAttribute("xxx")如果我没有在request里面设置xxx属性那么执行这段request.getAttribute("xxx")代码的效果是什么?都说回返回null,但是我没有先设置xxx,直接执行后报错了...下面是错误.如果先设置xxx的话就不会报错...
我是这么获取的:String name = request.getAttribute("name").toString();获取的方式没有错吧?在线等...HTTP Status 500 -type Exception reportmessagedescription The server encountered an internal error () that prevented it from fulfilling this request.exceptionorg.apache.jasper.JasperException: java.lang.NullPointerException
org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:502)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:430)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:313)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:260)
javax.servlet.http.HttpServlet.service(HttpServlet.java:717)root causejava.lang.NullPointerException
org.apache.jsp.addPersonList_jsp._jspService(addPersonList_jsp.java:59)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:388)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:313)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:260)
javax.servlet.http.HttpServlet.service(HttpServlet.java:717)note The full stack trace of the root cause is available in the Apache Tomcat/6.0.33 logs.
我是这么获取的:String name = request.getAttribute("name").toString();获取的方式没有错吧?在线等...HTTP Status 500 -type Exception reportmessagedescription The server encountered an internal error () that prevented it from fulfilling this request.exceptionorg.apache.jasper.JasperException: java.lang.NullPointerException
org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:502)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:430)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:313)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:260)
javax.servlet.http.HttpServlet.service(HttpServlet.java:717)root causejava.lang.NullPointerException
org.apache.jsp.addPersonList_jsp._jspService(addPersonList_jsp.java:59)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:388)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:313)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:260)
javax.servlet.http.HttpServlet.service(HttpServlet.java:717)note The full stack trace of the root cause is available in the Apache Tomcat/6.0.33 logs.
request.getAttribute("name"),返回一个空对象null,然后执行null.toString()方法,就报出了空指针错误,这个很容易理解你上面说的跟实验根本不冲突,恰恰证实了是返回null的
应该是
String name = (String)request.getAttribute("name");
然后判断name 是否为空,再做其他的操作