Package lazyj

Class DBFunctions.DBConnection

java.lang.Object
lazyj.DBFunctions.DBConnection
Enclosing class:
DBFunctions
public static final class DBFunctions.DBConnection
extends java.lang.Object
Wrapper around a raw database connection. You cannot create this object directly and you must free the connections properly otherwise you will run in big trouble.

Here is a sample code:

 // set the connection parameters 

 ExtProperties dbProp = new ExtProperties();
 dbProp.set("driver", "org.postgresql.Driver"); // mandatory
 dbProp.set("database", "somedb");                              // mandatory
 dbProp.set("host", "127.0.0.1");                                       // defaults to 127.0.0.1 if missing
 dbProp.set("port", "5432");                                            // DB-dependend default if missing
 dbProp.set("user", "username");                                        // recommended
 dbProp.set("password", "*****");                               // recommended
 // you can also set here various other configuration options that the JDBC driver will look at

 DBFunctions db = new DBFunctions(dbProp);

 DBFunctions.DBConnection conn = db.getConnection();

 if (conn==null) return;

 Statement stat = null;
 ResultSet rs = null;

 try{
      stat = conn.getConnection().createStatement(ResultSet.TYPE_SCROLL_INSENSITIVE, ResultSet.CONCUR_READ_ONLY);
      stat.execute(someQuery, Statement.NO_GENERATED_KEYS);

      rs = stat.getResultSet();

      // ..................

      rs.close();
      rs = null;

      stat.close();
      stat = null;
 }
 catch (Exception e){ ... }
 finally{
                if (rs!=null){
                        // close
                        try{
                                rs.close();
                        }
                        catch (Exception e){
                        }
                }

                if (stat!=null){
                        try{
                                stat.close();
                        }
                        catch (Exception e){
                        }
                }

                conn.free();
 }
Since:
Jan 17, 2009
Author:
costing
See Also:
DBFunctions(ExtProperties)

  • Method Summary

    Modifier and Type Method Description
    boolean canUse​(long checkInterval, boolean validateUsingQuery)
    Find out if this connection is free to use
    void close()
    Really close a connection to the database
    protected void finalize()
    On object deallocation make sure that the connection is properly closed.
    boolean free()
    Mark a previously used connection as free to be used by somebody else
    java.sql.Connection getConnection()
    Get the established JDBC connection for direct access to the database.
    java.lang.String getDescription()
    Get the current description
    boolean isReadOnly()
    Check the (cached) status of this connection.
    void setDescription​(java.lang.String description)
    Set the description to an arbitrary string to be used when debugging a problem.
    boolean setReadOnly​(boolean newValue)
    Set the read-only connection flag.
    boolean use()
    Use this connection, by marking it as busy and setting the last access time to the current time.

    Methods inherited from class java.lang.Object

    clone, equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

  • Method Details

    • getConnection

      public java.sql.Connection getConnection()
      Get the established JDBC connection for direct access to the database.
      Returns:
      the JDBC connection

    • canUse

      public boolean canUse​(long checkInterval, boolean validateUsingQuery)
      Find out if this connection is free to use
      Parameters:
      checkInterval - if strictly positive then how often (in milliseconds) to check if the connection is still valid, otherwise it will always be checked
      validateUsingQuery - if true then execute some explicit query
      Returns:
      true if free, false if busy or other error

    • use

      public boolean use()
      Use this connection, by marking it as busy and setting the last access time to the current time.
      Returns:
      true if the connection was free and could be used, false if it was not available

    • free

      public boolean free()
      Mark a previously used connection as free to be used by somebody else
      Returns:
      true if the connection was in use and was freed, false if the connection was in other state

    • close

      public void close()
      Really close a connection to the database

    • finalize

      protected void finalize()
      On object deallocation make sure that the connection is properly closed.
      Overrides:
      finalize in class java.lang.Object

    • setDescription

      public void setDescription​(java.lang.String description)
      Set the description to an arbitrary string to be used when debugging a problem.
      Parameters:
      description - the description to set

    • getDescription

      public java.lang.String getDescription()
      Get the current description
      Returns:
      the description

    • isReadOnly

      public boolean isReadOnly()
      Check the (cached) status of this connection. Doesn't go to the driver to ask for it but instead this is the last requested state.
      Returns:
      the read-only status of this connection

    • setReadOnly

      public boolean setReadOnly​(boolean newValue)
      Set the read-only connection flag. Only goes to the driver with the request in case the flag is different from the previously known value.
      Parameters:
      newValue -
      Returns:
      previous value of the read only flag