java - java jdbc连接过多

Question

错误:- 严重:空com.mysql.jdbc.exceptions.jdbc4.MySQLNonTransientConnectionException:数据源拒绝建立连接，来自服务器的消息:“连接太多”代码如下所示

   try {
        BufferedReader br=new BufferedReader(new FileReader(filename));
        String line;
        String tru="TRUNCATE `project`.`uploadtable`;";
        try
       {
             Statement stmt = Dutil.getConnection().createStatement();



     stmt.executeUpdate(tru);
        }
        catch(Exception e){}
        try {
            while((line=br.readLine())!=null){
                String values[]=line.split("\t");
                String[] splitStr = values[1].split(" ");


               try {String  sql="INSERT INTO `project`.`uploadtable` 
            (`empid`, `date`, `time`, `in_out_index`) VALUES 
            ('"+values[0]+"', '"+splitStr[0]+"', '"+splitStr[1]+"', 
             '"+values[3]+"');";
                    PreparedStatement 
                   pst=Dutil.getConnection().prepareStatement(sql);
                    pst.executeUpdate();
                } catch (SQLException ex) {
                    System.out.println("Error");

             Logger.getLogger(UploadFrame.class.getName()).log(Level.SEVERE, 
              null, ex);
                }
            } br.close();

             this.dispose();
           LogButtonFrame lbf=new LogButtonFrame();
          lbf.clockinouttable();
           JOptionPane.showMessageDialog(null,"Upload Complete");} catch 
           (IOException ex) {
            Logger.getLogger(UploadFrame.class.getName()).log(Level.SEVERE, 
          null, ex);
            }
             } catch (FileNotFoundException ex) {
           Logger.getLogger(UploadFrame.class.getName()).log(Level.SEVERE, 
            null, ex);
          }
          catch (Exception ex) {
         JOptionPane.showMessageDialog(null, "Error");
        }

Answer 1

问题是:

PreparedStatement pst = Dutil.getConnection().prepareStatement(sql);

您尚未显示 Dutil 的代码，但假设它在每次调用时创建一个新连接，这意味着该连接不会关闭，只能靠运气、驱动程序实现细节以及垃圾收集器将其关闭。

您应该使用 try-with-resources :

try (Connection connection = Dutil.getConnection();
     PreparedStatement pst = connection.prepareStatement(sql)) {
    // Use pst
}

此 block 结束后，pst和connection都会正确关闭，即使发生异常等情况。