没有可用的缓冲区空间，已达到最大连接数

Question

package Simple;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.sql.Statement;
import java.sql.Time;
import java.sql.Timestamp;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Calendar;
import java.util.Date;
import java.util.List;
import java.text.*;

public class CurrentProg {
    //connecting to the database

  private static final String DB_DRIVER = "com.mysql.jdbc.Driver";
  private static final String DB_CONNECTION ="jdbc:mysql://localhost:3306/db?autoReconnect=true"; 
  private static final String DB_USER = "root";
  private static final String DB_PASSWORD = "root";
  static Connection dbConnection = null;
  static Statement statement = null;

  static int total=1;

  //Searching between startdate and enddate

  public static java.util.LinkedList searchBetweenDates(java.util.Date startDate, java.util.Date endDate) {

        java.util.Date begin = new Date(startDate.getTime());
        java.util.LinkedList list = new java.util.LinkedList();
        list.add(new Date(begin.getTime()));
        java.util.Date end = new Date(endDate.getTime());
        endDate.setTime(endDate.getTime() + 24*3600*1000);
        Calendar cal = Calendar.getInstance();
        cal.setTime(begin);
       dbConnection = getDBConnection();

        while(begin.compareTo(endDate)<0){
        begin = new Date(begin.getTime() + 86400000);
        list.add(new Date(begin.getTime()));        
        Timestamp timestamp = new Timestamp(new Date().getTime());

        //For a single day calculation: 24hours*60mins=1440 /2 (2 mins time difference as per the requirement) = 720 

                for (int j = 0; j < 720; j++) {
                cal.add(Calendar.MINUTE, 2);            
                timestamp = new Timestamp(cal.getTime().getTime());
                String S = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(timestamp);               
                String[] parts = S.split(" ");
                String date=parts[0];
                String time=parts[1];
                cal.getTime().toString();

           // To create data loop into a List
            List<String> records = new ArrayList<String>();
            StringBuffer record = new StringBuffer();
            for (int i = 1; i <= total; i++) {
            records = new ArrayList<String>(total);         

            int a2 = 220 + j % 31; // 230 - 244 by 1
            String wString = Integer.toString(a2);
            String a = String.valueOf(a2);   
            double b2 = 0.00 + j % 3.7  ; // 1.3 - 3.9 by 0.1 
            String aString = Double.toString(b2);
            String b = String.valueOf(b2);
            b = b.substring(0, Math.min(b.length(), 5));


          record.delete(0, record.length());
          record.append(a + "," + b  +  ",'"+  date + "', '"+  time + "'");
          record.append("\t\t");      
          record.append("\n");
          records.add(record.toString()); 

          //Insert Query
          String insertTableSQL = "INSERT INTO cmd1"
                  + "(a, b, date, time) " + "VALUES"
                  + "("+record.toString()+")";
                  System.out.println("insertTableSQL - " + insertTableSQL);             //  Statement.executeUpdate(insertTableSQL);

          try {

                  statement = dbConnection.createStatement();
                  statement.executeUpdate(insertTableSQL);
                  System.out.println("Record is inserted into Db table!");
                  } catch (SQLException e) {
                  System.out.println(e.getMessage());
                  } 
      try {

            //  dbConnection = getDBConnection();
              statement = dbConnection.createStatement();
              statement.executeUpdate(insertTableSQL);
              System.out.println("Record is inserted into Db table!");
              } catch (SQLException e) {
              System.out.println(e.getMessage());
              } 
        finally {
        //  httpPost.releaseConnection()
            try{
                 if(statement!=null)
                    statement.close();
              }
             finally{
             }

              try{
                 if(dbConnection!=null)
                    dbConnection.close();
              }
              finally{

              }

              }                                            
         }
        }
        }
        return list;
        }

  @SuppressWarnings("unused")
public static void main(String[] args) throws Exception {

      //To enter startDate and enddate
    //  EntityManagerFactory.getCache().evictAll;


    SimpleDateFormat  startDate=new java.text.SimpleDateFormat("yyyy-MM-dd");
    SimpleDateFormat  endDate=new java.text.SimpleDateFormat("yyyy-MM-dd");

                java.util.LinkedList hitList = searchBetweenDates(
                startDate.parse("2016-01-01"),
                endDate.parse("2016-03-01"));
                String[] combo = new String[hitList.size()];
                for(int i=0; i<hitList.size(); i++)
                combo[i] = new java.text.SimpleDateFormat("yyyy-MM-dd").format(((java.util.Date)hitList.get(i)));

  }

private static void insertRecordIntodb() {
    //
  }
  private static Connection getDBConnection() {
    Connection dbConnection = null;
    try {
      Class.forName(DB_DRIVER);
    } catch (ClassNotFoundException e) {
      System.out.println(e.getMessage());
    }
    try {
      dbConnection = DriverManager.getConnection(DB_CONNECTION, DB_USER, DB_PASSWORD);
      return dbConnection;
    } catch (SQLException e) {
      System.out.println(e.getMessage());
    }
    return dbConnection;
  }  
} 

Server connection failure during transaction. Due to underlying exception: 'java.net.SocketException: java.net.SocketException: No buffer space available (maximum connections reached?): connect'.

** BEGIN NESTED EXCEPTION ** 

java.net.SocketException
MESSAGE: java.net.SocketException: No buffer space available (maximum connections reached?): connect

STACKTRACE:

java.net.SocketException: java.net.SocketException: No buffer space available (maximum connections reached?): connect
    at com.mysql.jdbc.StandardSocketFactory.connect(StandardSocketFactory.java:156)
    at com.mysql.jdbc.MysqlIO.<init>(MysqlIO.java:276)
    at com.mysql.jdbc.Connection.createNewIO(Connection.java:2717)
    at com.mysql.jdbc.Connection.<init>(Connection.java:1509)
    at com.mysql.jdbc.NonRegisteringDriver.connect(NonRegisteringDriver.java:266)
    at java.sql.DriverManager.getConnection(Unknown Source)
    at java.sql.DriverManager.getConnection(Unknown Source)
    at Simple.CurrentProg.getDBConnection(CurrentProg.java:186)
    at Simple.CurrentProg.searchBetweenDates(CurrentProg.java:126)
    at Simple.CurrentProg.main(CurrentProg.java:164)


** END NESTED EXCEPTION **


Attempted reconnect 3 times. Giving up.
Exception in thread "main" java.lang.NullPointerException
    at Simple.CurrentProg.searchBetweenDates(CurrentProg.java:137)
    at Simple.CurrentProg.main(CurrentProg.java:164)

Here I am trying to connect java program with database but when i am trying to insert large data say for 1 month so its only fetching 16000 records not more than that i want the data should be inserted as per the given date range what should i do to get that . In stacktrace its showing an exception as no buffer space available maximum connection reached. Thanks In advance

Answer 1

Here is the modified code. I removed a lot of code which is not necessary:

public static LinkedList<Date> searchBetweenDates(Date startDate, Date endDate) throws SQLException {
    Date begin = new Date(startDate.getTime());
    LinkedList<Date> list = new LinkedList<Date>();

    list.add(new Date(begin.getTime()));

    endDate.setTime(endDate.getTime() + 24 * 3600 * 1000);
    Calendar cal = Calendar.getInstance();
    cal.setTime(begin);

    dbConnection = getDBConnection();
    PreparedStatement ps = dbConnection.prepareStatement("INSERT INTO cmd1(aaaa, bbbb, datee, timee) VALUES(?, ?, ?, ?)");
    while (begin.compareTo(endDate) < 0) {
        begin = new Date(begin.getTime() + 86400000);
        list.add(new Date(begin.getTime()));
        Timestamp timestamp = new Timestamp(new Date().getTime());

        // For a single day calculation: 24hours*60mins=1440 /2 (2 mins time
        // difference as per the requirement) = 720

        for (int j = 0; j < 720; j++) {
            cal.add(Calendar.MINUTE, 2);
            timestamp = new Timestamp(cal.getTime().getTime());
            String S = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(timestamp);
            String[] parts = S.split(" ");
            String date = parts[0];
            String time = parts[1];
            cal.getTime().toString();

            // To create data loop into a List
            for (int i = 1; i <= total; i++) {

                int a2 = 220 + j % 31; // 230 - 244 by 1
                String a = String.valueOf(a2);
                double b2 = 0.00 + j % 3.7; // 1.3 - 3.9 by 0.1
                String b = String.valueOf(b2);
                b = b.substring(0, Math.min(b.length(), 5));

                ps.setString(1, a);
                ps.setString(2, b);
                ps.setString(3, date);
                ps.setString(4, time);

                ps.execute();
            }
        }
    }
    if (ps != null)
        ps.close();
    if (dbConnection != null)
        dbConnection.close();

    return list;
}

What I changed:

• I removed your try/catch's because I wanted to make the code short so that I can edit it here easily. But you should handle exception correctly. And don't swallow exceptions ever. I mean the following is no go :

   } catch (SQLException e) { System.out.println(e.getMessage()); } 

It is very bad Idea because you'll not see the real cause of the problem in this case; at least do e.printStackTrace() eventhough it is not recommended in a real project.

• I exchanged the Statement object for PreparedStatement because it is much more efficient.
• Removed package names and put import statements instead because it is not necessary to do so unless you have different classes from different packages with the same name.
• I changed column names because my DB does not want to accept them. Column names like a are very bad. Choose instead descriptive names so that you might understand what it is for a couple of months later. Don't use column names like date because they are reserved words for some databases systems I know.
• Don't create database resources like Connection in a loop unless it is absolutely needed! Otherwise, your program will go out of resources because these resources are very expensive! That is exactly what you are experiencing right now.

Hope it helps, otherwise, drop me a comment.