连接oracle时候报空指针异常

Question

    try {
        String className = "oracle.jdbc.driver.OracleDriver";
        Class.forName(className);
        System.out.println("加载数据库驱动成功!");
    } catch (ClassNotFoundException e) {
        System.out.println("加载数据库驱动失败!");
        e.printStackTrace();
    }

    try {
        System.out.println("开始连接数据库");
        String user = "sys as sysdba";
        String password = "123123";
        String url = "jdbc:oracle:thin:@焱:1521:XE";
        con = DriverManager.getConnection(url, user, password);
        System.out.print(con);
        System.out.println("创建数据库连接成功!");

    } catch (SQLException e) {
        System.out.print(con);
        System.out.println("创建数据库连接失败!");
        con = null;
        e.printStackTrace();
    }

            如果直接在类里面使用main函数 获取数据库能够连接成功，取出数据，但是在web页面的servlet中使用DBManager dbm = new DBManager(); 就会报空指针异常
            java.lang.NullPointerException
java.lang.String.<init>(String.java:166)
oracle.sql.CharacterSet.AL32UTF8ToString(CharacterSet.java:1516)
oracle.jdbc.driver.DBConversion.CharBytesToString(DBConversion.java:588)
oracle.jdbc.driver.DBConversion.CharBytesToString(DBConversion.java:541)
oracle.jdbc.driver.T4CTTIoauthenticate.receiveOauth(T4CTTIoauthenticate.java:815)
oracle.jdbc.driver.T4CConnection.logon(T4CConnection.java:361)
oracle.jdbc.driver.PhysicalConnection.<init>(PhysicalConnection.java:413)
oracle.jdbc.driver.T4CConnection.<init>(T4CConnection.java:164)
oracle.jdbc.driver.T4CDriverExtension.getConnection(T4CDriverExtension.java:34)
oracle.jdbc.driver.OracleDriver.connect(OracleDriver.java:752)
java.sql.DriverManager.getConnection(DriverManager.java:664)
java.sql.DriverManager.getConnection(DriverManager.java:247)
util.DBManager.<init>(DBManager.java:33)
service.StudentService.stu_Login(StudentService.java:21)
MyServlet.LoginPageServlet.doPost(LoginPageServlet.java:35)
javax.servlet.http.HttpServlet.service(HttpServlet.java:644)
javax.servlet.http.HttpServlet.service(HttpServlet.java:725)
org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)

最后指向的就是 con = DriverManager.getConnection(url, user, password);这一句连接语句

Answer 1

http://tieba.baidu.com/p/3272717602