SQLite内存不足异常

Question

I am getting the "java.sql.SQLException: [SQLITE_MISUSE] Library used incorrectly (out of memory)". I paste the code sample for my database connection object

public class DBhandler {
   private String DBUrl="d:\\sqlitedb\\somdb.db";
   private String driverName="org.sqlite.JDBC";
   private String jdbc="jdbc:sqlite:";
   private Connection con=null;
   private Statement stmnt=null;

  public DBhandler() 
  {
        try {
            Class.forName(this.driverName);
        } catch (ClassNotFoundException e1) {
            // TODO Auto-generated catch block
            e1.printStackTrace();
        }

            try {
                this.con=DriverManager.getConnection(this.jdbc+this.DBUrl);
                this.stmnt=con.createStatement();
            } catch (SQLException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }

  }

   public CurrentActiveSom getCurrentActiveSom()
 {

     CurrentActiveSom cas=null;
     String query="select * from current_active_som where active=1"; 
    ResultSet rs=null;

     try {
        rs=this.stmnt.executeQuery(query);
    if (rs.next())
    {
        cas= new CurrentActiveSom();
        cas.setMonth(rs.getString("month"));
        cas.setYear(rs.getString("year"));
        cas.setIsActive(rs.getInt("active"));

    }

    } catch (SQLException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }

     finally
     {
         try {
            rs.close();
            this.stmnt.close();
             this.con.close();
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

     }
     return cas;
 }

 public CurrentActiveSom getIsDoneSom(String month,String year)
 {

     CurrentActiveSom cas=null;
     String query="select * from current_active_som where month='"+month+"' and year='"+year+"' and active=0"; 

    ResultSet rs=null;


     try {

             rs=this.stmnt.executeQuery(query); //this is exception line
        }

        if (rs.next())
        {
            cas= new CurrentActiveSom();
            cas.setMonth(rs.getString("month"));
            cas.setYear(rs.getString("year"));
            cas.setIsActive(rs.getInt("active"));

        }


     } catch (SQLException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
     }

     finally
     {
         try {
            //rs.close(); //if i uncomment this gets null pointer exception 
            this.stmnt.close();
             this.con.close();
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }

     }
     return cas;
 }

The call to these Two methods with same object of DBhandler like

 DBhandler db=new DBhandler();
 CurrentActiveSom cas1=db.getCurrentActiveSom();
 CurrentActiveSom cas2=db.getIsDoneSom(String month,String year)

then I am getting the above exception ,

but if we call thses 2 methods with different object DBhandler like

   DBhandler db1=new DBhandler();
   DBhandler db2=new DBhandler();
   CurrentActiveSom cas1=db1.getCurrentActiveSom();
   CurrentActiveSom cas2=db2.getIsDoneSom(String month,String year)

Then code is working fine.

Is this because of sync problem, with connection ? how to resolve this problem?

Answer 1

Well, the "out of memory"error looks weird, but one definitive error lies in creating Connection once per program run (in the constructor) and then closing it in each data access method.

This code:

CurrentActiveSom cas1=db.getCurrentActiveSom();

closes the Connection , so this code:

CurrentActiveSom cas2=db.getIsDoneSom(String month,String year)

tries to get data from a closed database. This is OK if you are using some kind of connection pooling in which closing a connection returns it to the pool. But it seems you're working on a single physical connection.

So just close it after you're done getting data from DB, and not in each data access method.

Answer 2

在调用`rs.next（）之前，请先关闭连接，以便ResultSet尝试从已关闭的连接中读取。