java bean已经编译好了.
但在jsp运行java段的时候却报错,程序写法如下:
<%
String ls_s;
ls_s = "00226" ;
String sqlid = "select * from a where b = " + ls_s;
String zhm ;
ResultSet rsid=student.executeQuery(sqlid);
if(rsid.next())
{
zhm=rsid.getString("bb");
out.println(zhm);
}
%>
如果把 if(rsid.next())
{
zhm=rsid.getString("bb");
out.println(zhm);
}
封掉,就不会报错,但如果不封,就会出现HTTP Status 500 - --------------------------------------------------------------------------------type Exception reportmessage 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
org.apache.jsp.a_jsp._jspService(a_jsp.java:73)
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)这样的错误.为什么呢?有没有哪位高手知道啊?
但在jsp运行java段的时候却报错,程序写法如下:
<%
String ls_s;
ls_s = "00226" ;
String sqlid = "select * from a where b = " + ls_s;
String zhm ;
ResultSet rsid=student.executeQuery(sqlid);
if(rsid.next())
{
zhm=rsid.getString("bb");
out.println(zhm);
}
%>
如果把 if(rsid.next())
{
zhm=rsid.getString("bb");
out.println(zhm);
}
封掉,就不会报错,但如果不封,就会出现HTTP Status 500 - --------------------------------------------------------------------------------type Exception reportmessage 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
org.apache.jsp.a_jsp._jspService(a_jsp.java:73)
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)这样的错误.为什么呢?有没有哪位高手知道啊?
if(rsid.next())
{
zhm=rsid.getString("bb");
out.println(zhm);
}
然后打印一下rsid.next(),看输出是不是null
// to your things
}
还有ResultSet rsid=student.executeQuery(sqlid); 这句之前最好也 判断一下student是否为空.