使用JDBC联接MySQL失败
日期：2014-05-17 浏览次数：21003 次
使用JDBC连接MySQL失败
使用JDBC连接MySQL数据库时连接失败，并返回java.lang.NullPointerException异常，为什么会发生空指针异常？求大神指点~~
<body>
<%
String userName=
new String(request.getParameter("userName").getBytes("ISO-8859-1"),"UTF-8");
String password=
new String(request.getParameter("password").getBytes("ISO-8859-1"),"UTF-8");
Connection con=null;
Statement st=null;
ResultSet rs=null;
if(userName.equals(""))
{
response.sendRedirect("login.jsp");
}
try{
Class.forName("com.mysql.jdbc.Driver");
String url="jdbc:mysql://localhost:3306/eims?useUnicode=true&characterEncoding=gbk";
con=DriverManager.getConnection(url, "root", "6785098");
st = con.createStatement();
String query = "select * from user where userName = '" + userName + "'";
rs = st.executeQuery(query);
if (rs.next())
{
String query2 = "select * from user where password = '" + password + "'";
rs = st.executeQuery(query2);
if (rs.next())
{
response.sendRedirect("main/main.jsp");
&nbs
使用JDBC连接MySQL数据库时连接失败，并返回java.lang.NullPointerException异常，为什么会发生空指针异常？求大神指点~~
<body>
<%
String userName=
new String(request.getParameter("userName").getBytes("ISO-8859-1"),"UTF-8");
String password=
new String(request.getParameter("password").getBytes("ISO-8859-1"),"UTF-8");
Connection con=null;
Statement st=null;
ResultSet rs=null;
if(userName.equals(""))
{
response.sendRedirect("login.jsp");
}
try{
Class.forName("com.mysql.jdbc.Driver");
String url="jdbc:mysql://localhost:3306/eims?useUnicode=true&characterEncoding=gbk";
con=DriverManager.getConnection(url, "root", "6785098");
st = con.createStatement();
String query = "select * from user where userName = '" + userName + "'";
rs = st.executeQuery(query);
if (rs.next())
{
String query2 = "select * from user where password = '" + password + "'";
rs = st.executeQuery(query2);
if (rs.next())
{
response.sendRedirect("main/main.jsp");
&nbs
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