获得的变量为NULL
当然会出错
cate =request.getParameter("incate");
if(cate!=null){ int intincate=java.lang.Integer.parseInt(cate);
}
当然会出错
cate =request.getParameter("incate");
if(cate!=null){ int intincate=java.lang.Integer.parseInt(cate);
}
if(cate.equals("")!=true)
{
int intincate=java.lang.Integer.parseInt(cate);
}
谢谢!
以前一直用PHP,还不太习惯。
Thank you very much
:)
String sqlSel="select id,title,cate,size,note,fname from oaperson where userid ='"+dbuserid+"' '"+osel+"' order by id desc limit '"+bnum+"','"+enum+"'";
ResultSet rstSel=null;
int i=0;
String fgfg="";
rstSel=mysql.Sele(dataMybase,sqlSel);
int dbid=0;
String dbtitle="";
int dbcate=0;
String dbsize;
String dbnote;
String dbfname;
while(rstSel.next())
{
i++;
dbid=rstSel.getInt(1);
dbtitle=rstSel.getString(2);
dbcate=rstSel.getInt(3);
dbsize=rstSel.getString(4);
dbnote=rstSel.getString(5);
dbfname=rstSel.getString(6);
fgfg=fgfg+"<tr><td align=center bgcolor=#FFFFCC>"+dbtitle+"</td> <td align=center bgcolor=#FFFFCC>"+dbsize+"</td> <td align=center bgcolor=#FFFFCC>"+dbnote+"</td> <td align=center bgcolor=#FFFFCC><a href=\"/upload/person/"+dbfname+"\"><img border=0 src=/images/doing.gif width=18 height=16></a></td> <td align=center bgcolor=#FFFFCC><a href='javascript:isdel("+dbid+");'><img border=0 src=/images/del.gif width=16 height=16 ></a></td></tr>
";
}这段程序为什么会提示:
java.lang.NullPointerException
at org.apache.jsp.person$jsp._jspService(person$jsp.java:370)
at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:107)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:853)
at org.apache.jasper.servlet.JspServlet$JspServletWrapper.service(JspServlet.java:201)
at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:381)
at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:473)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:853)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:247)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:193)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:243)
at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:566)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:472)
at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:943)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:190)
at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:566)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:472)
at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:943)
at org.apache.catalina.core.StandardContext.invoke(StandardContext.java:2347)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:180)
at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:566)
at org.apache.catalina.valves.ErrorDispatcherValve.invoke(ErrorDispatcherValve.java:170)
at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:564)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:170)
at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:564)
at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:468)
at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:564)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:472)
at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:943)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:174)
at org.apache.catalina.core.StandardPipeline.invokeNext(StandardPipeline.java:566)
at org.apache.catalina.core.StandardPipeline.invoke(StandardPipeline.java:472)
at org.apache.catalina.core.ContainerBase.invoke(ContainerBase.java:943)
at org.apache.ajp.tomcat4.Ajp13Processor.process(Ajp13Processor.java:458)
at org.apache.ajp.tomcat4.Ajp13Processor.run(Ajp13Processor.java:551)
at java.lang.Thread.run(Thread.java:484)
我对PHP还一窍不通呢!
共同学习!
java.lang.NullPointerException
的问题呢??
谢谢!!
后面应该很清楚了。
String sqlSel="select id,title,cate,size,note,fname from oaperson where userid ='"+dbuserid+"' '"+osel+"' order by id desc limit '"+bnum+"','"+enum+"'";
1,'"+osel+"' 前要有字段名(例如:title='"+osel+"' )
2,有没有userid这个字段名?
3,limit是什么限制?好象没这样的语法!
4,where后如果有一个以上的条件要用and ,or等连接!
忘了告诉你'"+osel+"' 是一个字符串,相当与动态的条件,比如,他可以是“and cate=0 ”,至于LIMIT,是限定获取记录的范围。
不过,还是非常感谢你!