Re: please help: PostgreSQL JDBC Pooling problem - Mailing list pgsql-jdbc

Marcus,

The fix for this is pretty easy, just add the following to the beginning
of the toString() method of AbstractJdbc1Statement.java:

    //if no sql yet set, return default toString()
    if (m_sqlFragments == null)
        return super.toString();

I will check in a fix for this soon.

thanks,
--Barry


Barry Lind wrote:
> Marcus,
>
> OK, that reproduces.  The stack traces shows that it is this line of
> code that is causing the null pointer exception:
>               System.out.println("Statement = " + loStatement);
>
> Specificly the toString() method on the loStatement object.  It isn't
> the fact that loStatement is null, but a logic error in the toString()
> method.  I don't yet know why the toString() method has a null pointer
> exception, but in normal operations I wouldn't expect that code would be
> calling toString on a Statement object.
>
> thanks,
> --Barry
>
> Marcus Andree S. Magalhaes wrote:
>
>> Barry,
>>
>> Try to change the openConnection method as follows:
>>
>> public Statement openConnection() {
>>          Statement loStatement;
>>          System.out.println("opening  con");
>>          try {
>>              // gets a connection from Pool
>> this.loConnection = loPoolSource.getConnection();
>>              System.out.println("loConnection = " + this.loConnection);
>>              loStatement = this.loConnection.createStatement();
>>              System.out.println("Statement = " + loStatement);
>>              return loStatement;
>>              // return this.loConnection.createStatement();
>>
>>          } catch (Exception loException) {
>>              loException.printStackTrace();
>>          }
>>
>>          return null;
>>      }
>>
>>
>> With my system (Solaris x86, latest jdk 1.4 from Sun and postgresql
>> 7.3.2) this
>> results in a NullPointer Exception when printing loStatement on the
>> screen.
>>
>> This seems to reproduce the error happening in my main application.
>> The classes
>> simply can't connect to the database because all Statements that
>> openConnection()
>> returns are null.
>>
>> BTW, is this the correct manner to implement a Pooled DB in PostgreSQL
>> and
>> a singleton class wrapped as a static attribute (loPoolSource) ??
>>
>>
>> Thanks again.
>>
>> Marcus Andree
>>
>>
>> Quoting Barry Lind <blind@xythos.com>:
>>
>>
>>> Marcus,
>>>
>>> I can't reproduce your problem.  When I run the modifed version of
>>> your test (changes made so that it compiles and runs standalone) I
>>> don't have any errors.  My test table has about 1000 rows in it and
>>> everything works fine without any errors.
>>>
>>> I am running the latest 7.3 build (109) against a 7.3.2 database
>>> using the sun 1.4.1_01 jdk on Redhat8.
>>>
>>> Is there something else I need to do to reproduce the problem?
>>>
>>> thanks,
>>> --Barry
>>>
>>> Marcus Andree S. Magalhaes wrote:
>>>
>>>> Dear list,
>>>>
>>>>
>>>> I'm having a couple problems while implementing a JDBC Connection pool
>>>
>>>
>>> using
>>>
>>>> Postgresql Jdbc3PoolingDataSource.
>>>>
>>>> I was able to reproduce the errors with a simple java program. I'll
>>>> be grateful if someone could analyse this problem for a while...
>>>>
>>>> The class io_property is a local class using standard java Properties
>>>> classes to load data from a simple text file. This is done when calling
>>>> the io_property.startService() static method.
>>>>
>>>> If I run the program exactly as show below, it works wonderfully.
>>>> However,
>>>> when commenting the return line of openConnection and uncommenting the
>>>> previous 3 lines as:
>>>>
>>>>         this.loConnection = loPoolSource.getConnection();
>>>>         System.out.println("loConnection = " + this.loConnection);
>>>>         loStatement = this.loConnection.createStatement();
>>>>         System.out.println("Statement = " + loStatement);
>>>>         return loStatement;
>>>>         // return this.loConnection.createStatement();
>>>>
>>>> The JDBC Statement returned is null. That's the problem I'm facing
>>>> with my
>>>> main application...
>>>> Why is this happening?? In which circumstances
>>>> does Connection.createStatement() return null???
>>>>
>>>>
>>>> My main application is a bit different... It uses threads and lots
>>>> of SQL
>>>> code. I have to return a Statement instead of a Connection for
>>>> historical
>>>> reasons...
>>>>
>>>>
>>>> Any help is welcome. The source file follows...
>>>>
>>>>
>>>> Marcus
>>>>
>>>>
>>>
>>> ===============================================================================
>>>
>>>
>>>> public class con_database {
>>>>
>>>>    static Jdbc3PoolingDataSource loPoolSource = null;
>>>>    private Connection loConnection = null;
>>>>
>>>>    con_database() {
>>>>     io_property.startService();
>>>>    }
>>>>
>>>>    private static void setPool() {
>>>>     // DataSource initialization
>>>>     System.out.println("setPool()");
>>>>     try {
>>>>         System.out.println("setting pool");
>>>>         // constructs a pool only when loPoolSource is not assigned.
>>>>         // this will prevent problems if the same pool is set more than
>>>>         // one time
>>>>         if (loPoolSource == null) {
>>>>         loPoolSource = new Jdbc3PoolingDataSource();
>>>>         // DataSource configuration.
>>>>
>>>
>>>
>>> loPoolSource.setDataSourceName(io_property.DATABASE_POOL_DATA_SOURCE_NAME);
>>>
>>> //
>>>
>>>> any name is valid here
>>>>
>>>> loPoolSource.setServerName(io_property.DATABASE_POOL_SERVER_NAME);
>>>>
>>>> loPoolSource.setPortNumber(io_property.DATABASE_POOL_SERVER_PORT);
>>>>
>>>> loPoolSource.setDatabaseName(io_property.DATABASE_POOL_DATABASE_NAME);
>>>>         loPoolSource.setUser(io_property.DATABASE_POOL_USER_NAME);
>>>>         loPoolSource.setPassword(io_property.DATABASE_POOL_PASSWORD);
>>>>
>>>> loPoolSource.setMaxConnections(io_property.DATABASE_POOL_MAXCONNECTIONS);
>>>>
>>>
>>>
>>>>
>>>>         } else {
>>>>         System.out.println("pool is set");
>>>>         return;
>>>>         }
>>>>     } catch (Exception loException) {
>>>>         // logger.logToFile(loException);
>>>>         loException.printStackTrace();
>>>>     }
>>>>
>>>>    }
>>>>
>>>>
>>>>
>>>>    public Statement openConnection() {
>>>>     Statement loStatement;
>>>>     System.out.println("opening  con");
>>>>     try {
>>>>         // gets a connection from Pool
>>>>         this.loConnection = loPoolSource.getConnection();
>>>>         System.out.println("loConnection = " + this.loConnection);
>>>>         // loStatement = this.loConnection.createStatement();
>>>>         // System.out.println("Statement = " + loStatement);
>>>>         // return loStatement;
>>>>         return this.loConnection.createStatement();
>>>>
>>>>     } catch (Exception loException) {
>>>>         loException.printStackTrace();
>>>>     }
>>>>
>>>>     return null;
>>>>    }
>>>>
>>>>    public void closeConnection() {
>>>>     System.out.println("closing  con");
>>>>     try {
>>>>         if (this.loConnection != null) this.loConnection.close();
>>>>     } catch (Exception loException) {
>>>>         loException.printStackTrace();
>>>>     }
>>>>    }
>>>>
>>>>
>>>>    public static void main(String args[]) {
>>>>
>>>>     Statement loStatement = null;
>>>>     con_database loPoolConnection = new con_database();
>>>>     loPoolConnection.setPool();
>>>>     loStatement = loPoolConnection.openConnection();
>>>>     ResultSet lors = null;
>>>>     try {
>>>>         lors = loStatement.executeQuery("select * from <tablename>");
>>>>         while (lors.next()) {
>>>>         System.out.println(lors.getString(1));
>>>>         }
>>>>     } catch (Exception e) {
>>>>         e.printStackTrace();
>>>>     }
>>>>     finally {
>>>>         try {
>>>>         lors.close();
>>>>         loStatement.close();
>>>>         loPoolConnection.closeConnection();
>>>>         } catch (Exception loException) {
>>>>         loException.printStackTrace();
>>>>         }
>>>>     }
>>>>
>>>>     loPoolConnection = new con_database();
>>>>     loPoolConnection.setPool();
>>>>     loStatement = null;
>>>>     loStatement = loPoolConnection.openConnection();
>>>>     lors = null;
>>>>     try {
>>>>         lors = loStatement.executeQuery("select * from <table_name>");
>>>>         while (lors.next()) {
>>>>         System.out.println(lors.getString(2));
>>>>         }
>>>>     } catch (Exception e) {
>>>>         e.printStackTrace();
>>>>     }
>>>>     finally {
>>>>         try {
>>>>         lors.close();
>>>>         loStatement.close();
>>>>         loPoolConnection.closeConnection();
>>>>         } catch (Exception loException) {
>>>>         loException.printStackTrace();
>>>>         }
>>>>     }
>>>>     }
>>>>   }
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>> -------------------------------
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>>>>
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>>>
>>
>>
>>
>>
>> -------------------------------
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>>
>
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