225 lines
8.1 KiB
HTML
225 lines
8.1 KiB
HTML
<?xml version="1.0" encoding="UTF-8" standalone="no"?>
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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<html xmlns="http://www.w3.org/1999/xhtml">
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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
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<title>Placing Objects in an Entity Store</title>
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<link rel="stylesheet" href="gettingStarted.css" type="text/css" />
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<meta name="generator" content="DocBook XSL Stylesheets V1.62.4" />
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<link rel="home" href="index.html" title="Getting Started with Berkeley DB" />
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<link rel="up" href="persist_access.html" title="Chapter 5. Saving and Retrieving Objects" />
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<link rel="previous" href="simpleda.html" title="SimpleDA.class" />
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<link rel="next" href="simpleget.html" title="Retrieving Objects from an Entity Store" />
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</head>
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<body>
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<div class="navheader">
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<table width="100%" summary="Navigation header">
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<tr>
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<th colspan="3" align="center">Placing Objects in an Entity Store</th>
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</tr>
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<tr>
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<td width="20%" align="left"><a accesskey="p" href="simpleda.html">Prev</a> </td>
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<th width="60%" align="center">Chapter 5. Saving and Retrieving Objects</th>
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<td width="20%" align="right"> <a accesskey="n" href="simpleget.html">Next</a></td>
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</tr>
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</table>
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<hr />
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</div>
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<div class="sect1" lang="en" xml:lang="en">
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<div class="titlepage">
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<div>
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<div>
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<h2 class="title" style="clear: both"><a id="simpleput"></a>Placing Objects in an Entity Store</h2>
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</div>
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</div>
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<div></div>
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</div>
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<p>
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In order to place an object in a DPL entity store,
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you must:
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</p>
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<div class="orderedlist">
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<ol type="1">
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<li>
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<p>
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Open the environment and store.
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</p>
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</li>
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<li>
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<p>
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Instantiate the object.
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</p>
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</li>
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<li>
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<p>
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Put the object to the store using the
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<tt class="methodname">put()</tt> method
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for the object's primary index.
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</p>
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</li>
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</ol>
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</div>
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<p>
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The following example uses the <tt class="classname">SimpleDA</tt>
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class that we show in <a href="simpleda.html">SimpleDA.class</a> to put a
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<tt class="classname">SimpleEntityClass</tt> object (see
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<a href="persist_access.html#simpleentity">A Simple Entity Class</a>) to the
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entity store.
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</p>
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<p>
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To begin, we import the Java classes that our example
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needs. We also instantiate the private data members that we
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require.
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</p>
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<pre class="programlisting">package persist.gettingStarted;
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import java.io.File;
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import java.io.FileNotFoundException;
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import com.sleepycat.db.DatabaseException;
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import com.sleepycat.db.Environment;
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import com.sleepycat.db.EnvironmentConfig;
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import com.sleepycat.persist.EntityStore;
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import com.sleepycat.persist.StoreConfig;
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public class SimpleStorePut {
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private static File envHome = new File("./JEDB");
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private Environment envmnt;
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private EntityStore store;
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private SimpleDA sda; </pre>
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<p>
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Next we create a method that simply opens our database
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environment and entity store for us.
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</p>
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<pre class="programlisting"> // The setup() method opens the environment and store
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// for us.
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public void setup()
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throws DatabaseException {
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EnvironmentConfig envConfig = new EnvironmentConfig();
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StoreConfig storeConfig = new StoreConfig();
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envConfig.setAllowCreate(true);
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storeConfig.setAllowCreate(true);
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try {
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// Open the environment and entity store
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envmnt = new Environment(envHome, envConfig);
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store = new EntityStore(envmnt, "EntityStore", storeConfig);
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} catch (FileNotFoundException fnfe) {
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System.err.println("setup(): " + fnfe.toString());
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System.exit(-1);
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}
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} </pre>
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<p>
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We also need a method to close our environment and store.
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</p>
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<pre class="programlisting"> // Close our environment and store.
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public void shutdown()
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throws DatabaseException {
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store.close();
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envmnt.close();
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} </pre>
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<p>
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Now we need to create a method to actually write objects to our
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store. This method creates a <tt class="classname">SimpleDA</tt>
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object (see <a href="simpleda.html">SimpleDA.class</a> that we
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will use to access our indexes. Then we instantiate a serious
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of <tt class="classname">SimpleEntityClass</tt> (see <a href="persist_access.html#simpleentity">A Simple Entity Class</a>)
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instances that we
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will place in our store. Finally, we use our primary index
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(obtained from the <tt class="classname">SimpleDA</tt> class
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instance) to actually place these objects in our store.
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</p>
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<p>
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In <a href="simpleget.html">Retrieving Objects from an Entity Store</a>
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we show a class that is used to retrieve these objects.
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</p>
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<pre class="programlisting"> // Populate the entity store
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private void run()
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throws DatabaseException {
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setup();
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// Open the data accessor. This is used to store
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// persistent objects.
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sda = new SimpleDA(store);
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// Instantiate and store some entity classes
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SimpleEntityClass sec1 = new SimpleEntityClass();
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SimpleEntityClass sec2 = new SimpleEntityClass();
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SimpleEntityClass sec3 = new SimpleEntityClass();
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SimpleEntityClass sec4 = new SimpleEntityClass();
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SimpleEntityClass sec5 = new SimpleEntityClass();
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sec1.setpKey("keyone");
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sec1.setsKey("skeyone");
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sec2.setpKey("keytwo");
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sec2.setsKey("skeyone");
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sec3.setpKey("keythree");
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sec3.setsKey("skeytwo");
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sec4.setpKey("keyfour");
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sec4.setsKey("skeythree");
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sec5.setpKey("keyfive");
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sec5.setsKey("skeyfour");
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sda.pIdx.put(sec1);
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sda.pIdx.put(sec2);
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sda.pIdx.put(sec3);
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sda.pIdx.put(sec4);
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sda.pIdx.put(sec5);
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shutdown();
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} </pre>
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<p>
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Finally, to complete our class, we need a
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<tt class="methodname">main()</tt> method, which simply calls our
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<tt class="methodname">run()</tt> method.
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</p>
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<pre class="programlisting"> // main
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public static void main(String args[]) {
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SimpleStorePut ssp = new SimpleStorePut();
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try {
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ssp.run();
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} catch (DatabaseException dbe) {
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System.err.println("SimpleStorePut: " + dbe.toString());
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dbe.printStackTrace();
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} catch (Exception e) {
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System.out.println("Exception: " + e.toString());
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e.printStackTrace();
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}
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System.out.println("All done.");
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}
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} </pre>
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</div>
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<div class="navfooter">
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<hr />
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<table width="100%" summary="Navigation footer">
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<tr>
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<td width="40%" align="left"><a accesskey="p" href="simpleda.html">Prev</a> </td>
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<td width="20%" align="center">
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<a accesskey="u" href="persist_access.html">Up</a>
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</td>
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<td width="40%" align="right"> <a accesskey="n" href="simpleget.html">Next</a></td>
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</tr>
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<tr>
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<td width="40%" align="left" valign="top">SimpleDA.class </td>
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<td width="20%" align="center">
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<a accesskey="h" href="index.html">Home</a>
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</td>
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<td width="40%" align="right" valign="top"> Retrieving Objects from an Entity Store</td>
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</tr>
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</table>
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</div>
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</body>
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</html>
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