jsp问题

Question

org.apache.jasper.JasperException: Exception in JSP: /user.jsp:8885:    sql="select * from chatroom where room='"+room+"' and NickName<> '"+NickName+"'";
86:    rs=list.executeQuery(sql);
87: 
88:       while(rs.next())
89:    {
90:      if(rs.getString("Sex")=="男")
91:  {
Stacktrace:
org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:451)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:373)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:329)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:265)
javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
root cause java.lang.NullPointerException
org.apache.jsp.user_jsp._jspService(user_jsp.java:142)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:98)
javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:331)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:329)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:265)
javax.servlet.http.HttpServlet.service(HttpServlet.java:803)什么原因啊?什么原因?

Answer 1

空指针啊，你进行方法调用的某个类为null了，检查一下

Answer 2

空指针错误:if(rs!=null){
   while(rs.next()) 
 { 
      if(rs.getString("Sex")=="男") 
 
}

Answer 3

java.lang.NullPointerException 空指针错误
rs.getString("Sex")=="男"
先判断空 而且 string比较用equals

Answer 4

用equals方法有这个问题哦 怎么解决?
在selectroom.jsp中
<a href="main.jsp?room=sportchat" target="_parent">体育地带(<%=sportnumber%>人)</a>
在main.jsp中
String room=(String)request.getParameter("room");
运行后:
org.apache.jasper.JasperException: Exception in JSP: /user.jsp:4542:    String sql="insert into chatroom(NickName,Room,Sex) values('"+UserName+"','"+room+"','"+Sex+"')";
43:    int update=list.excuteUpdate(sql);
44: 
45:    if(room.equals("sportchat"))
46:    {
47: %>
48: 
Stacktrace:
org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:451)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:373)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:329)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:265)
javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
root cause java.lang.NullPointerException
org.apache.jsp.user_jsp._jspService(user_jsp.java:95)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:98)
javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:331)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:329)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:265)
javax.servlet.http.HttpServlet.service(HttpServlet.java:803)

Answer 5

 if(room != null && room.equals("sportchat"))