In order to place an object in a DPL entity store, you must:
Open the environment and store.
Instantiate the object.
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 java.io.FileNotFoundException; import com.sleepycat.db.DatabaseException; import com.sleepycat.db.Environment; import com.sleepycat.db.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); try { // Open the environment and entity store envmnt = new Environment(envHome, envConfig); store = new EntityStore(envmnt, "EntityStore", storeConfig); } catch (FileNotFoundException fnfe) { System.err.println("setup(): " + fnfe.toString()); System.exit(-1); } }
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 serious
of SimpleEntityClass
(see A Simple Entity Class)
instances 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."); } }