Placing Objects in an Entity Store

In order to place an object in a DPL entity store, you must:

  1. Open the environment and store.

  2. Instantiate the object.

  3. Put the object to the store using the put() method for the object's primary index.

The following example uses the SimpleDA class that we show in SimpleDA.class to put a SimpleEntityClass object (see A Simple Entity Class) to the entity store.

To begin, we import the Java classes that our example needs. We also instantiate the private data members that we require.

package persist.gettingStarted;

import java.io.File;

import com.sleepycat.je.DatabaseException;
import com.sleepycat.je.Environment;
import com.sleepycat.je.EnvironmentConfig;

import com.sleepycat.persist.EntityStore;
import com.sleepycat.persist.StoreConfig; 

public class SimpleStorePut {

    private static File envHome = new File("./JEDB");

    private Environment envmnt;
    private EntityStore store;
    private SimpleDA sda; 

Next we create a method that simply opens our database environment and entity store for us.

   // The setup() method opens the environment and store
    // for us.
    public void setup()
        throws DatabaseException {

        EnvironmentConfig envConfig = new EnvironmentConfig();
        StoreConfig storeConfig = new StoreConfig();

        envConfig.setAllowCreate(true);
        storeConfig.setAllowCreate(true);

        // Open the environment and entity store
        envmnt = new Environment(envHome, envConfig);
        store = new EntityStore(envmnt, "EntityStore", storeConfig);
    } 

We also need a method to close our environment and store.

    // Close our environment and store.
    public void shutdown()
        throws DatabaseException {

        store.close();
        envmnt.close();
    } 

Now we need to create a method to actually write objects to our store. This method creates a SimpleDA object (see SimpleDA.class that we will use to access our indexes. Then we instantiate a series of SimpleEntityClass (see A Simple Entity Class) objects that we will place in our store. Finally, we use our primary index (obtained from the SimpleDA class instance) to actually place these objects in our store.

In Retrieving Objects from an Entity Store we show a class that is used to retrieve these objects.

    // Populate the entity store
    private void run()
        throws DatabaseException {

        setup();

        // Open the data accessor. This is used to store
        // persistent objects.
        sda = new SimpleDA(store);

        // Instantiate and store some entity classes
        SimpleEntityClass sec1 = new SimpleEntityClass();
        SimpleEntityClass sec2 = new SimpleEntityClass();
        SimpleEntityClass sec3 = new SimpleEntityClass();
        SimpleEntityClass sec4 = new SimpleEntityClass();
        SimpleEntityClass sec5 = new SimpleEntityClass();

        sec1.setPKey("keyone");
        sec1.setSKey("skeyone");

        sec2.setPKey("keytwo");
        sec2.setSKey("skeyone");

        sec3.setPKey("keythree");
        sec3.setSKey("skeytwo");

        sec4.setPKey("keyfour");
        sec4.setSKey("skeythree");

        sec5.setPKey("keyfive");
        sec5.setSKey("skeyfour");

        sda.pIdx.put(sec1);
        sda.pIdx.put(sec2);
        sda.pIdx.put(sec3);
        sda.pIdx.put(sec4);
        sda.pIdx.put(sec5);

        shutdown();
    } 

Finally, to complete our class, we need a main() method, which simply calls our run() method.

    // main
    public static void main(String args[]) {
        SimpleStorePut ssp = new SimpleStorePut();
        try {
            ssp.run();
        } catch (DatabaseException dbe) {
            System.err.println("SimpleStorePut: " + dbe.toString());
            dbe.printStackTrace();
        } catch (Exception e) {
            System.out.println("Exception: " + e.toString());
            e.printStackTrace();
        }
        System.out.println("All done.");
    }

}