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Using Entities with Collections
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<th width="60%" align="center">Chapter 4.
Using Entity Classes
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<h2 class="title" style="clear: both"><a id="entitieswithcollections"></a>
Using Entities with Collections
</h2>
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<p>
In this example entity objects, rather than key and value
objects, are used for adding and enumerating the records in a
collection. Because fewer classes and objects are involved, adding
and enumerating is done more conveniently and more simply than in
the prior examples.
</p>
<p>
For adding and iterating entities, the collection of entities
returned by
<a class="ulink" href="http://java.sun.com/j2se/1.5.0/docs/api/java/util/Map.html#values" target="_top">Map.values</a>
is used. In general, when using an entity binding, all Java
collection methods that are passed or returned a value object will
be passed or returned an entity object instead.
</p>
<p>
The <code class="classname">Sample</code> class has been changed in this example to add
objects using the
<a class="ulink" href="http://java.sun.com/j2se/1.5.0/docs/api/java/util/Set.html#add" target="_top">Set.add</a>
method rather than the
<a class="ulink" href="http://java.sun.com/j2se/1.5.0/docs/api/java/util/Map.html#put" target="_top">Map.put</a>
method that was used in the prior examples. Entity objects are
constructed and passed to
<a class="ulink" href="http://java.sun.com/j2se/1.5.0/docs/api/java/util/Set.html#add" target="_top">Set.add</a>.
</p>
<a id="entity_addsuppliers"></a>
<pre class="programlisting">import java.util.Set;
...
public class Sample
{
...
private void addSuppliers()
{
<strong class="userinput"><code> Set suppliers = views.getSupplierSet();
if (suppliers.isEmpty())
{
System.out.println("Adding Suppliers");
suppliers.add(new Supplier("S1", "Smith", 20, "London"));
suppliers.add(new Supplier("S2", "Jones", 10, "Paris"));
suppliers.add(new Supplier("S3", "Blake", 30, "Paris"));
suppliers.add(new Supplier("S4", "Clark", 20, "London"));
suppliers.add(new Supplier("S5", "Adams", 30, "Athens"));
}</code></strong>
}
private void addParts()
{
<strong class="userinput"><code> Set parts = views.getPartSet();
if (parts.isEmpty())
{
System.out.println("Adding Parts");
parts.add(new Part("P1", "Nut", "Red",
new Weight(12.0, Weight.GRAMS), "London"));
parts.add(new Part("P2", "Bolt", "Green",
new Weight(17.0, Weight.GRAMS), "Paris"));
parts.add(new Part("P3", "Screw", "Blue",
new Weight(17.0, Weight.GRAMS), "Rome"));
parts.add(new Part("P4", "Screw", "Red",
new Weight(14.0, Weight.GRAMS), "London"));
parts.add(new Part("P5", "Cam", "Blue",
new Weight(12.0, Weight.GRAMS), "Paris"));
parts.add(new Part("P6", "Cog", "Red",
new Weight(19.0, Weight.GRAMS), "London"));
}</code></strong>
}
private void addShipments()
{
<strong class="userinput"><code> Set shipments = views.getShipmentSet();
if (shipments.isEmpty())
{
System.out.println("Adding Shipments");
shipments.add(new Shipment("P1", "S1", 300));
shipments.add(new Shipment("P2", "S1", 200));
shipments.add(new Shipment("P3", "S1", 400));
shipments.add(new Shipment("P4", "S1", 200));
shipments.add(new Shipment("P5", "S1", 100));
shipments.add(new Shipment("P6", "S1", 100));
shipments.add(new Shipment("P1", "S2", 300));
shipments.add(new Shipment("P2", "S2", 400));
shipments.add(new Shipment("P2", "S3", 200));
shipments.add(new Shipment("P2", "S4", 200));
shipments.add(new Shipment("P4", "S4", 300));
shipments.add(new Shipment("P5", "S4", 400));
}</code></strong>
} </pre>
<p>
Instead of printing the key/value pairs by iterating over the
<a class="ulink" href="http://java.sun.com/j2se/1.5.0/docs/api/java/util/Map.html#entrySet" target="_top">Map.entrySet</a>
as done in the prior example, this example
iterates over the entities in the
<a class="ulink" href="http://java.sun.com/j2se/1.5.0/docs/api/java/util/Map.html#values" target="_top">Map.values</a>
collection.
</p>
<a id="entity_printdatabase"></a>
<pre class="programlisting">import java.util.Iterator;
import java.util.Set;
...
public class Sample
{
...
private class PrintDatabase implements TransactionWorker
{
public void doWork()
throws Exception
{
<strong class="userinput"><code> printValues("Parts",
views.getPartSet().iterator());
printValues("Suppliers",
views.getSupplierSet().iterator());</code></strong>
printValues("Suppliers for City Paris",
views.getSupplierByCityMap().duplicates(
"Paris").iterator());
<strong class="userinput"><code> printValues("Shipments",
views.getShipmentSet().iterator());</code></strong>
printValues("Shipments for Part P1",
views.getShipmentByPartMap().duplicates(
new PartKey("P1")).iterator());
printValues("Shipments for Supplier S1",
views.getShipmentBySupplierMap().duplicates(
new SupplierKey("S1")).iterator());
}
}
...
} </pre>
<p>
The output of the example program is shown below.
</p>
<pre class="programlisting">Adding Suppliers
Adding Parts
Adding Shipments
--- Parts ---
Part: number=P1 name=Nut color=Red weight=[12.0 grams] city=London
Part: number=P2 name=Bolt color=Green weight=[17.0 grams] city=Paris
Part: number=P3 name=Screw color=Blue weight=[17.0 grams] city=Rome
Part: number=P4 name=Screw color=Red weight=[14.0 grams] city=London
Part: number=P5 name=Cam color=Blue weight=[12.0 grams] city=Paris
Part: number=P6 name=Cog color=Red weight=[19.0 grams] city=London
--- Suppliers ---
Supplier: number=S1 name=Smith status=20 city=London
Supplier: number=S2 name=Jones status=10 city=Paris
Supplier: number=S3 name=Blake status=30 city=Paris
Supplier: number=S4 name=Clark status=20 city=London
Supplier: number=S5 name=Adams status=30 city=Athens
--- Suppliers for City Paris ---
Supplier: number=S2 name=Jones status=10 city=Paris
Supplier: number=S3 name=Blake status=30 city=Paris
--- Shipments ---
Shipment: part=P1 supplier=S1 quantity=300
Shipment: part=P1 supplier=S2 quantity=300
Shipment: part=P2 supplier=S1 quantity=200
Shipment: part=P2 supplier=S2 quantity=400
Shipment: part=P2 supplier=S3 quantity=200
Shipment: part=P2 supplier=S4 quantity=200
Shipment: part=P3 supplier=S1 quantity=400
Shipment: part=P4 supplier=S1 quantity=200
Shipment: part=P4 supplier=S4 quantity=300
Shipment: part=P5 supplier=S1 quantity=100
Shipment: part=P5 supplier=S4 quantity=400
Shipment: part=P6 supplier=S1 quantity=100
--- Shipments for Part P1 ---
Shipment: part=P1 supplier=S1 quantity=300
Shipment: part=P1 supplier=S2 quantity=300
--- Shipments for Supplier S1 ---
Shipment: part=P1 supplier=S1 quantity=300
Shipment: part=P2 supplier=S1 quantity=200
Shipment: part=P3 supplier=S1 quantity=400
Shipment: part=P4 supplier=S1 quantity=200
Shipment: part=P5 supplier=S1 quantity=100
Shipment: part=P6 supplier=S1 quantity=100 </pre>
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Creating Collections with Entity Bindings
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Using Tuples
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