JDBC链接数据库的问题,出现如下错误 !

Question

作用域不对啊，
你的Connection Conn定义在Try Catch当中，也就是只能在Try Catch之间可见
所以不对，
Connection Conn = null;
try{
Class.forName("org.gjt.mm.mysql.Driver").newInstance();
coon = java.sql.DriverManager.getConnection();

Answer 1

Connection Conn 
try{
Class.forName("org.gjt.mm.mysql.Driver").newInstance();
Conn= java.sql.DriverManager.getConnection("jdbc:mysql://localhost:3306/test","sbm","1");
}
catch(ClassNotFoundException e){
out.print("ClassNotFount Error!!");
}
catch(SQLException e1){
out.print("SQL Error");
}这样Conn在try外面try相当于一个块，所以在别的地方访问不到

Answer 2

哦,的确,我把try去掉又出现下面的错误,不好意思,初学者,请再帮忙一下
---------------------------------------------------------------
错误
---------------------------------------------------------------
javax.servlet.ServletException: Before start of result set
org.apache.jasper.runtime.PageContextImpl.doHandlePageException(PageContextImpl.java:867)
org.apache.jasper.runtime.PageContextImpl.handlePageException(PageContextImpl.java:800)
org.apache.jsp.test.two_jsp._jspService(two_jsp.java:67)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:133)
javax.servlet.http.HttpServlet.service(HttpServlet.java:856)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:311)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:301)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:248)
javax.servlet.http.HttpServlet.service(HttpServlet.java:856)
root cause java.sql.SQLException: Before start of result set
org.gjt.mm.mysql.ResultSet.checkRowPos(ResultSet.java:1336)
org.gjt.mm.mysql.ResultSet.getString(ResultSet.java:220)
org.gjt.mm.mysql.ResultSet.getString(ResultSet.java:889)
org.apache.jsp.test.two_jsp._jspService(two_jsp.java:52)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:133)
javax.servlet.http.HttpServlet.service(HttpServlet.java:856)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:311)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:301)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:248)
javax.servlet.http.HttpServlet.service(HttpServlet.java:856)
note The full stack trace of the root cause is available in the Tomcat logs.

Answer 3

stat = Conn.createStatement(ResultSet.TYPE_SCROLL_SENSITIVE,ResultSet.CONCUR_UPDATABLE);
这样试试

Answer 4

我看不懂你的代码,我的代码是这样子的,是哪里出了毛病...:)()<%
Connection Conn=null;
Statement stmt=null;
String sql=null;
ResultSet rs=null;Class.forName("org.gjt.mm.mysql.Driver").newInstance();
Conn = java.sql.DriverManager.getConnection("jdbc:mysql://localhost:3306/test","sbm","1");stmt=Conn.createStatement();
sql="select * from test";
rs=stmt.executeQuery(sql);if (rs.getString("pwd")==null){
out.print("rs null");
}
else{
while(rs.next()){
out.print(rs.getString("pwd"));
}
}
%>