为什么我的servlet连接mysql数据库时，总发生以下错误（我用的是tomcat服务器）：

显示全部楼层 · 2011-5-8 14:43:57

type Exception report
message
description The server encountered an internal error () that prevented it from fulfilling this request.
exception
java.lang.NullPointerException
HelloServletJdbc.doPost(HelloServletJdbc.java:50)
HelloServletJdbc.doGet(HelloServletJdbc.java:11)
javax.servlet.http.HttpServlet.service(HttpServlet.java:690)
javax.servlet.http.HttpServlet.service(HttpServlet.java:803)
note The full stack trace of the root cause is available in the Apache Tomcat/6.0.14 logs.
--------------------------------------------------------------------------------
Apache Tomcat/6.0.14
Connection conn = null;
Statement st = null;
ResultSet rs = null;
resp.setContentType("text/html");
resp.setCharacterEncoding("gb2312");
PrintWriter out = resp.getWriter();
try {
Class.forName("com.mysql.jdbc.Driver");
conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/bbs?user=root&password=6850262");
st = conn.createStatement();
rs = st.executeQuery("select * from aa");
while (rs.next()) {
out.println(rs.getString("myname"));
}
} catch (ClassNotFoundException e) {
e.printStackTrace();
} catch (SQLException e) {
e.printStackTrace();
} finally {
if (rs != null) {
try {
rs = null;
rs.close();
st.close();
conn.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}

千问 · 2011-5-8 14:43:57

推测原因：1、数据库没有打开，解决方法：打开服务器；2、驱动包没有加进去，解决办法：下载mysql驱动包->项目->右击->properties->java build path->libraries-> add external jars（这是在myeclipse下的流程，如果你用的是其他的IDE你再百度一下）；3、连接字符串写错，解决办法：仔细检查你的URL是否正确。

千问 · 2011-5-8 14:43:57

空指针,看看50行是什么内容

千问 · 2011-5-8 14:43:57

请求被阻止了