Question

尝试使用共享连接（在初始化请求时创建连接）将记录添加到数据库中这里我是request.getAttribute（）方法，用于从RequestListener.java检索属性并将其分配给连接类型引用。 / p>

这是我的代码：RequestListener.java

public class RequestListener implements ServletRequestListener {
@Override
public void requestDestroyed(ServletRequestEvent sre) {
    try {
        Connection connection=(Connection) sre.getServletContext().getAttribute("conn");
        connection.close();
    } catch (SQLException ex) {
        Logger.getLogger(RequestListener.class.getName()).log(Level.SEVERE, null, ex);
    }
}

@Override
public void requestInitialized(ServletRequestEvent sre) {

        try {
            Class.forName("com.mysql.jdbc.Driver");
           Connection connection= DriverManager.getConnection("jdbc:mysql://localhost/school?user=root&password=mysql"); 
            sre.getServletContext().setAttribute("conn",connection);
        } catch (Exception ex) {
        Logger.getLogger(RequestListener.class.getName()).log(Level.SEVERE, null, ex);
    }
}

}

 error:java.lang.NullPointerException
      at servlets.One.processRequest(One.java:45)
      at servlets.One.doGet(One.java:89)

////// One.java（servlet）

protected void processRequest(HttpServletRequest request, HttpServletResponse response)
        throws ServletException, IOException {
    response.setContentType("text/html;charset=UTF-8");
    try (PrintWriter out = response.getWriter()) {

        String t1=request.getParameter("text1");
        out.println("A");
         Connection connection = (Connection) request.getAttribute("conn");
  //line45 **PreparedStatement ps = connection.prepareStatement("insert into tb1 values(?)");**
        ps.setString(1, t1);
        ps.executeUpdate();
        ps.close();
        request.setAttribute("conn", connection);
        request.getRequestDispatcher("B").forward(request, response);
            request.getRequestDispatcher("Two").forward(request, response);
        } catch (SQLException ex) {
            Logger.getLogger(One.class.getName()).log(Level.SEVERE, null, ex);
        }

    }

Answer 1

RequestListener.java

＆＃34; sre.getServletContext（）的setAttribute（＆＃34;康恩＆＃34;，连接）＆＃34;必须更正为sre.getServletRequest（）。setAttribute（＆＃34; conn＆＃34;，connection）并避免将请求发送到两个servlet作为＆＃34; request.getRequestDispatcher（＆＃34; B＆＃34;）。forward （要求，回应）; request.getRequestDispatcher（＆＃34; Two＆＃34;）。forward（request，response）;＆＃34;这会导致illegalStateException

GlassFishServer中的java.lang.NullPointerException

1 个答案: