<!--$Id: read.html,v 1.2 2004/03/30 01:22:46 jtownsen Exp $--> <!--Copyright 1997-2003 by Sleepycat Software, Inc.--> <!--All rights reserved.--> <!--See the file LICENSE for redistribution information.--> <html> <head> <title>Berkeley DB Reference Guide: Using entities with collections</title> <meta name="description" content="Berkeley DB: An embedded database programmatic toolkit."> <meta name="keywords" content="embedded,database,programmatic,toolkit,b+tree,btree,hash,hashing,transaction,transactions,locking,logging,access method,access methods,Java,C,C++"> </head> <body bgcolor=white> <a name="2"><!--meow--></a> <table width="100%"><tr valign=top> <td><h3><dl><dt>Berkeley DB Reference Guide:<dd>Java API Tutorial - Entity</dl></h3></td> <td align=right><a href="../bdb_entity/views.html"><img src="../../images/prev.gif" alt="Prev"></a><a href="../toc.html"><img src="../../images/ref.gif" alt="Ref"></a><a href="../bdb_tuple/intro.html"><img src="../../images/next.gif" alt="Next"></a> </td></tr></table> <p> <h3 align=center>Using entities with collections</h3> <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 href="http://java.sun.com/j2se/1.3/docs/api/java/util/Map.html#values">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> <hr size=1 noshade> <p>The <b>Sample</b> class has been changed in this example to add objects using the <a href="http://java.sun.com/j2se/1.3/docs/api/java/util/Set.html#add">Set.add</a> method rather than the <a href="http://java.sun.com/j2se/1.3/docs/api/java/util/Map.html#put">Map.put</a> method that was used in the prior examples. Entity objects are constructed and passed to <a href="http://java.sun.com/j2se/1.3/docs/api/java/util/Set.html#add">Set.add</a> .</p> <blockquote><pre> public class Sample { ... private void addSuppliers() { <b> 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")); } </b> } <p> private void addParts() { <b> 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")); } </b> } <p> private void addShipments() { <b> 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)); } </b> } </pre></blockquote> <hr size=1 noshade> <p>Instead of printing the key/value pairs by iterating over the <a href="http://java.sun.com/j2se/1.3/docs/api/java/util/Map.html#entrySet">Map.entrySet</a> as done in the prior example, this example iterates over the entities in the <a href="http://java.sun.com/j2se/1.3/docs/api/java/util/Map.html#values">Map.values</a> collection.</p> <blockquote><pre> import com.sleepycat.bdb.collection.StoredIterator; import java.util.Iterator; import java.util.Set; ... public class Sample { ... private class PrintDatabase implements TransactionWorker { public void doWork() throws Exception { <b> printValues("Parts", views.getPartSet().iterator()); printValues("Suppliers", views.getSupplierSet().iterator()); </b> printValues("Suppliers for City Paris", views.getSupplierByCityMap().duplicates( "Paris").iterator()); <b> printValues("Shipments", views.getShipmentSet().iterator()); </b> 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></blockquote> <hr size=1 noshade> <p>The output of the example program is shown below.</p> <blockquote><pre> Adding Suppliers Adding Parts Adding Shipments <p> --- 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 <p> --- 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 <p> --- Suppliers for City Paris --- Supplier: number=S2 name=Jones status=10 city=Paris Supplier: number=S3 name=Blake status=30 city=Paris <p> --- 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 <p> --- Shipments for Part P1 --- Shipment: part=P1 supplier=S1 quantity=300 Shipment: part=P1 supplier=S2 quantity=300 <p> --- 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></blockquote> <table width="100%"><tr><td><br></td><td align=right><a href="../bdb_entity/views.html"><img src="../../images/prev.gif" alt="Prev"></a><a href="../toc.html"><img src="../../images/ref.gif" alt="Ref"></a><a href="../bdb_tuple/intro.html"><img src="../../images/next.gif" alt="Next"></a> </td></tr></table> <p><font size=1><a href="../../sleepycat/legal.html">Copyright (c) 1996-2003</a> <a href="http://www.sleepycat.com">Sleepycat Software, Inc.</a> - All rights reserved.</font> </body> </html>