asked on 3/4/2007

apache.commons: How to get a DataSource?

Hi,

I plan to hide it for my application to access a "settings"-table or file with two columns: attribute and value.
For that I thought to use apache.commons.

What I did (using a database) until now is getting the connection like this:
try {
            Class.forName(plmSettingsDBDriver);
      }
      catch (ClassNotFoundException cnfe) {
            logger.error("Error while reading database-driver-class", cnfe );
      }
      String url = plmSettingsDBURL;
      String username = plmSettingsUser;
      String password = mySettingsPassword;
      Connection con = DriverManager.getConnection(url, username, password);

and reading the data as usual:

con = getPLMSettingsConnection();

                    for (int i = 0; i < select.length; i++) {
                    stmt = con.createStatement();
                    String query = "SELECT value FROM settings WHERE ATTRIBUTE = '" +
                          select[i] + "'";
                    ResultSet rs = stmt.executeQuery(query);
...
}

Now I would like to replace the reading of data with Connections, Statements and ResultSets with something like this:

String value = config.getEntry(select[0], "settings");

while config is of type CCommConf, where I defined the following functions:

private Configuration getConfiguration(String configName) throws Exception {
            ConfigurationFactory factory = new ConfigurationFactory();
             factory.setConfigurationFileName(CONFIGFILE);
             Configuration conf1 = factory.getConfiguration();
             Configuration conf2 = null;
             if (con != null) {
                   conf2 = new DatabaseConfiguration((DataSource)con,
                         "settings", "attribute", "value");
             } else {
                  ConfigurationFactory factory2 = new ConfigurationFactory();
                   factory2.setConfigurationFileName(SETTINGSFILE);
                   conf2 = factory.getConfiguration();
             }

             // Create and initialize the node combiner
            NodeCombiner combiner = new UnionCombiner();

            // Construct the combined configuration
            CombinedConfiguration cc = new CombinedConfiguration(combiner);
            cc.addConfiguration((AbstractConfiguration) conf1, "db");
            cc.addConfiguration((AbstractConfiguration) conf2, "settings");

            return cc.getConfiguration(configName);
      }

/**
       * Constructor without any code
       *
       */
      public CCommConf() {
      }

      /**
       * Set´s the connection for the settings-table, if the
       * settings-table is in a database and not some other kind
       * of storage.
       * @param con Connection
       */
      public void setConnection(Connection con) {
            this.con = con;
      }

public String getEntry(String entry, String configName) throws Exception {
            String ret = null;
try {
      config = getConfiguration(configName);
                 if (config.getProperty(entry) != null)
                       ret = config.getProperty(entry).toString();
            } catch (ConfigurationException e) {
                  logger.fatal(e);
                  throw e;
            }
            return ret;
      }

What I don´t know is now:
- How to get a DataSource (I know, the following case is not the right thing to do it: conf2 = new DatabaseConfiguration((DataSource)con, "settings", "attribute", "value"); ). I read somewhere that I have to use JNDI, but - if it´s really necessary - I don´t know how to do that. But maybe it´s not necessary to use JNDI, there is a simpler way?

Java

Last Comment

anokun7

3/5/2007

anokun7

3/4/2007

You need to configure the JNDI names on your application server. Its really very simple especially with most application servers which provide a console / web interface for filling in the details.

Once you create a JNDI name that binds (links) to a DataSource which contains the connection pool, you can use code something like this to point to it:

public static Connection getConnection() {
Connection dbConnection = null;
InitialContext ic;
DataSource dataSource;

try {
ic = new InitialContext();
dataSource = (DataSource) ic.lookup("<THE JNDI NAME>");
if (dataSource != null) {
dbConnection = dataSource.getConnection();
}
} catch (Exception e) {
System.out.println(e.getMessage());
}
return dbConnection;
}

spetrowitsch

3/4/2007

ASKER

@anokun7

Is it really necessary to make it with an JNDI? In that case, there has to be an application server (and - until now - there is no application server connected with our application, so I would need one just for using jakarta.commons).

anokun7

3/4/2007

ohh - i am sorry - i assumed you were using a j2ee setting.

So - then you do not need a JNDI setup - actually you do not even need a datasource - A datasource is intended to be used with a JNDI context only.

You should be able to get a connection from your connection pool and that would handle creating adequate connections to serve new clients from th pool...

Let me know if my answer is not very clear - I can elaborate.

ASKER CERTIFIED SOLUTION

Mayank S

3/5/2007

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rrz

3/5/2007

>conf2 = new DatabaseConfiguration((DataSource)con, "settings", "attribute", "value");
You can't use a cast. I have an idea(hack) that might take you in the right direction. Hopefully the experts will comment. I've never done this before. You could try to use something like this.
conf2 = new DatabaseConfiguration( new MyDataSource(), "settings", "attribute", "value");
where we have something like

import javax.sql.DataSource;
import //.... the others needed
public class MyDataSource implements DataSource
{
String username = plmSettingsUser;
String password = mySettingsPassword;
String url = plmSettingsDBURL;
Connection con;
public MyDataSource() {
con = DriverManager.getConnection(url, username, password);
}
public Connection getConnection() throws SQLException{
return con;
}
public Connection getConnection(String username,String password) throws SQLException{
}
public PrintWriter getLogWriter() throws SQLException{
return ??? ;
}
public void setLogWriter() throws SQLException{
}
public int getLoginTimeout() throws SQLException{
return ??? ;
public void setLoginTimeout() throws SQLException{
}
}

spetrowitsch

3/5/2007

ASKER

I tried to implement something like this:
http://svn.apache.org/viewvc/jakarta/commons/proper/dbcp/trunk/doc/BasicDataSourceExample.java?view=markup

I changed getConfiguration to:
private Configuration getConfiguration(String configName) throws Exception {
            if (configName.equals("settings")) {
                  if (dbDriver != null) {
                        DataSource ds = setupDataSource();
                         return new DatabaseConfiguration(ds,
                               "settings", "attribute", "value");
                   } else {
                        ConfigurationFactory factory = new ConfigurationFactory();
                         factory.setConfigurationFileName(SETTINGSFILE);
                         return factory.getConfiguration();
                   }
            }
            return null;
      }

and added the following function:

private DataSource setupDataSource() throws Exception {
            BasicDataSource ds = null;
            try {
      ds = new BasicDataSource();
       ds.setDriverClassName(dbDriver);
       ds.setUsername(dbUser);
       ds.setPassword(dbPwd);
       ds.setUrl(dbURL);
} catch (Exception e) {
      throw e;
}
return ds;
}

but when I reach the following line in this function:
ds = new BasicDataSource();

I get this error:
ERROR Following error occurred in method performAction: org/apache/commons/pool/impl/GenericObjectPool, class: ...
Inner: java.lang.NoClassDefFoundError: org/apache/commons/pool/impl/GenericObjectPool
ERROR org/apache/commons/pool/impl/GenericObjectPool

I tried to import org.apache.commons.pool.impl.GenericObjectPool, but org.apache.commons.pool is not available.

SOLUTION

anokun7

3/5/2007

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