java - 无法连接到servlet中的mysql数据库

Question

当我尝试连接到我的 MySQL 数据库时，我不断收到此错误:

exception

javax.servlet.ServletException: JDBC Problem: 
root cause

com.mysql.jdbc.exceptions.jdbc4.CommunicationsException: Communications link failure

The last packet sent successfully to the server was 0 milliseconds ago. The driver has not received any packets from the server.
root cause

java.net.ConnectException: Connection timed out: connect

这是一些代码:

Connection con = null;
        Statement stmt = null;
        ResultSet rs = null;
        try{
            Class.forName("com.mysql.jdbc.Driver");
            con = DriverManager.getConnection
                    ("jdbc:mysql://mysql11.000webhost.com/database_name","user_name","password");
        stmt = con.createStatement();
        rs = stmt.executeQuery("INSERT into emailadresses('email') values ('"+email+"')");
        } catch (ClassNotFoundException ex) {
            Logger.getLogger(EmailServlet.class.getName()).log(Level.SEVERE, null, ex);
        }catch(SQLException e){
            throw new ServletException("JDBC Problem: ", e);
        }

编辑:我的库中有 mysql-connector-java jar 文件

编辑:发现问题我在我托管数据库的网站上寻找答案并找到了这个:

JDBC/ODBC is not supported here

这太糟糕了...

Answer 1

“在尝试将套接字连接到远程地址和端口时发生错误的信号。通常，连接被远程拒绝(例如，没有进程正在监听远程地址/端口)”。 - From Oracle Docs

查看您的连接字符串，确保数据库、用户名和密码输入正确。

另一个原因可能是您的数据库服务器未启动。