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<p>
<tt class="classname">ExampleInventoryRead</tt>
retrieves
inventory information from our entity store and
displays it. When it displays each inventory item, it
also displays the related vendor contact information.
</p>
<p>
<tt class="classname">ExampleInventoryRead</tt>
can do one of two things. If you provide no search
criteria, it displays all of the inventory items in the
store. If you provide an item name (using the
<tt class="literal">-s</tt> command line switch), then just
those inventory items using that name are displayed.
</p>
<p>
The beginning of our example is almost identical to our
<tt class="classname">ExampleDatabasePut</tt>
example program. We
repeat that example code here for the sake of
completeness. For a complete walk-through of it, see
the previous section (<a href="dpl_exampledatabaseput.html">ExampleDatabasePut.class</a>).
</p>
<pre class="programlisting">package persist.gettingStarted;
import java.io.File;
import java.io.IOException;
import com.sleepycat.db.DatabaseException;
import com.sleepycat.persist.EntityCursor;
public class ExampleInventoryRead {
private static File myDbEnvPath =
new File("/tmp/JEDB");
private DataAccessor da;
// Encapsulates the database environment.
private static MyDbEnv myDbEnv = new MyDbEnv();
// The item to locate if the -s switch is used
private static String locateItem;
private static void usage() {
System.out.println("ExampleInventoryRead [-h <env directory>]" +
"[-s <item to locate>]");
System.exit(-1);
}
public static void main(String args[]) {
ExampleInventoryRead eir = new ExampleInventoryRead();
try {
eir.run(args);
} catch (DatabaseException dbe) {
System.err.println("ExampleInventoryRead: " + dbe.toString());
dbe.printStackTrace();
} finally {
myDbEnv.close();
}
System.out.println("All done.");
}
private void run(String args[])
throws DatabaseException {
// Parse the arguments list
parseArgs(args);
myDbEnv.setup(myDbEnvPath, // path to the environment home
true); // is this environment read-only?
// Open the data accessor. This is used to retrieve
// persistent objects.
da = new DataAccessor(myDbEnv.getEntityStore());
// If a item to locate is provided on the command line,
// show just the inventory items using the provided name.
// Otherwise, show everything in the inventory.
if (locateItem != null) {
showItem();
} else {
showAllInventory();
}
} </pre>
<p>
The first method that we provide is used to show inventory
items related to a given inventory name. This method is called
only if an inventory name is passed to
<tt class="classname">ExampleInventoryRead</tt>
via the <tt class="literal">-s</tt> option. Given the sample data
that we provide with this example, each matching inventory name
will result in the display of three inventory objects.
</p>
<p>
To display these objects we use the
<tt class="classname">Inventory</tt> class'
<tt class="literal">inventoryByName</tt> secondary index to retrieve
an <tt class="classname">EntityCursor</tt>, and then we iterate
over the resulting objects using the cursor.
</p>
<p>
Notice that this method calls
<tt class="methodname">displayInventoryRecord()</tt>
to display each individual object. We show this
method a little later in the example.
</p>
<pre class="programlisting"> // Shows all the inventory items that exist for a given
// inventory name.
private void showItem() throws DatabaseException {
// Use the inventory name secondary key to retrieve
// these objects.
EntityCursor<Inventory> items =
da.inventoryByName.subIndex(locateItem).entities();
try {
for (Inventory item : items) {
displayInventoryRecord(item);
}
} finally {
items.close();
}
} </pre>
<p>
Next we implement <tt class="methodname">showAllInventory()</tt>,
which shows all of the <tt class="classname">Inventory</tt>
objects in the store. To do this, we
obtain an <tt class="classname">EntityCursor</tt>
from the <tt class="classname">Inventory</tt> class'
primary index and, again, we iterate using that cursor.
</p>
<pre class="programlisting"> // Displays all the inventory items in the store
private void showAllInventory()
throws DatabaseException {
// Get a cursor that will walk every
// inventory object in the store.
EntityCursor<Inventory> items =
da.inventoryBySku.entities();
try {
for (Inventory item : items) {
displayInventoryRecord(item);
}
} finally {
items.close();
}
} </pre>
<p>
Now we implement
<tt class="methodname">displayInventoryRecord()</tt>. This
uses the getter methods on the <tt class="classname">Inventory</tt>
class to obtain the information that we want to display.
The only thing interesting about this method is that we
obtain <tt class="classname">Vendor</tt> objects within.
The vendor objects are retrieved <tt class="classname">Vendor</tt>
objects using their primary index. We get the key
for the retrieval from the <tt class="classname">Inventory</tt>
object that we are displaying at the time.
</p>
<pre class="programlisting"> private void displayInventoryRecord(Inventory theInventory)
throws DatabaseException {
System.out.println(theInventory.getSku() + ":");
System.out.println("\t " + theInventory.getItemName());
System.out.println("\t " + theInventory.getCategory());
System.out.println("\t " + theInventory.getVendor());
System.out.println("\t\tNumber in stock: " +
theInventory.getVendorInventory());
System.out.println("\t\tPrice per unit: " +
theInventory.getVendorPrice());
System.out.println("\t\tContact: ");
Vendor theVendor =
da.vendorByName.get(theInventory.getVendor());
assert theVendor != null;
System.out.println("\t\t " + theVendor.getAddress());
System.out.println("\t\t " + theVendor.getCity() + ", " +
theVendor.getState() + " " + theVendor.getZipcode());
System.out.println("\t\t Business Phone: " +
theVendor.getBusinessPhoneNumber());
System.out.println("\t\t Sales Rep: " +
theVendor.getRepName());
System.out.println("\t\t " +
theVendor.getRepPhoneNumber());
} </pre>
<p>
The last remaining parts of the example are used to parse
the command line. This is not very
interesting for our purposes here, but we show it anyway
for the sake of completeness.
</p>
<pre class="programlisting"> protected ExampleInventoryRead() {}
private static void parseArgs(String args[]) {
for(int i = 0; i < args.length; ++i) {
if (args[i].startsWith("-")) {
switch(args[i].charAt(1)) {
case 'h':
myDbEnvPath = new File(args[++i]);
break;
case 's':
locateItem = args[++i];
break;
default:
usage();
}
}
}
}
} </pre>
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