以下是我的代码,我正在使用JDBC,并使查询运行得更快,将PrepareStatement替换为Statement,但页面不是woking。我在做什么错?用Statement替换时,Prepared statement is not working?
代码:
<select name="city" onchange="Consituteshow(this.value)" required="required">
<option value="">Select State</option>
<%
PreparedStatement stmt=null;
DBconnection db=new DBconnection();
Connection con=db.dbConn();
try{
stmt = (PreparedStatement)con.createStatement();
ResultSet rs = stmt.executeQuery("select distinct StateID,State from election_history;");
while(rs.next())
{
%>
<option value="<%=rs.getString(2)%>"><%=rs.getString(2)%></option>
<%
}
}
catch(SQLException e){
e.printStackTrace();
}
finally{
con.close();
stmt.close();
}
%>
</select>
我的罐子:
antlr.jar
java-image-scaling
mysql-connecotr-java 2.0.14
错误:
java.lang.NullPointerException
at org.apache.jsp.election_005fresults_jsp._jspService(election_005fresults_jsp.java:267)
at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:374)
at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:342)
at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:267)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:233)
at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:191)
at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:128)
at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:102)
at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:109)
at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:293)
at org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:849)
at org.apache.coyote.http11.Http11Protocol$Http11ConnectionHandler.process(Http11Protocol.java:583)
at org.apache.tomcat.util.net.JIoEndpoint$Worker.run(JIoEndpoint.java:454)
at java.lang.Thread.run(Unknown Source)
显示内部控制台。可谁能告诉什么是错误的下面的错误?
旁注:避免小脚本,使用JSTL。单独的控制器和DAO,并保持BE Servlets的逻辑 – sanbhat
请花更多时间格式化您的问题。有没有必要这样滚动水平差不多这么多... –
@Jon Skeet我怎样才能让我的查询运行得更快???有没有办法做到这一点? – user3332446