Import BSDDB 4.7.25 (as of svn r89086)
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Zachary Ware
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docs/gsg/JAVA/mydbenv-persist.html
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docs/gsg/JAVA/mydbenv-persist.html
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<?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>MyDbEnv</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="dpl_example.html" title="Chapter 6. A DPL Example" />
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<link rel="previous" href="inventoryclass.html" title="Inventory.class" />
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<link rel="next" href="dataaccessorclass.html" title="DataAccessor.class" />
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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">MyDbEnv</th>
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</tr>
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<tr>
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<td width="20%" align="left"><a accesskey="p" href="inventoryclass.html">Prev</a> </td>
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<th width="60%" align="center">Chapter 6. A DPL Example</th>
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<td width="20%" align="right"> <a accesskey="n" href="dataaccessorclass.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="mydbenv-persist"></a>MyDbEnv</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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The applications that we are building for our example both
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must open and close environments and entity stores. One
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of our applications is writing to the entity store, so this
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application needs to open the store as read-write. It also
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wants to be able to create the store if it does not exist.
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</p>
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<p>
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Our second application only reads from the store. In this
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case, the store should be opened as read-only.
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</p>
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<p>
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We perform these activities by creating a single class that
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is responsible for opening and closing our store and
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environment. This class is shared by both our applications.
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To use it, callers need to only provide the path to the
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environment home directory, and to indicate whether the
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object is meant to be read-only. The class implementation
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is as follows:
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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 MyDbEnv {
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private Environment myEnv;
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private EntityStore store;
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// Our constructor does nothing
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public MyDbEnv() {}
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// The setup() method opens the environment and store
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// for us.
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public void setup(File envHome, boolean readOnly)
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throws DatabaseException {
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EnvironmentConfig myEnvConfig = new EnvironmentConfig();
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StoreConfig storeConfig = new StoreConfig();
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myEnvConfig.setReadOnly(readOnly);
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storeConfig.setReadOnly(readOnly);
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// If the environment is opened for write, then we want to be
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// able to create the environment and entity store if
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// they do not exist.
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myEnvConfig.setAllowCreate(!readOnly);
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storeConfig.setAllowCreate(!readOnly);
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try {
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// Open the environment and entity store
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myEnv = new Environment(envHome, myEnvConfig);
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store = new EntityStore(myEnv, "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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}
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// Return a handle to the entity store
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public EntityStore getEntityStore() {
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return store;
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}
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// Return a handle to the environment
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public Environment getEnv() {
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return myEnv;
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}
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// Close the store and environment.
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public void close() {
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if (store != null) {
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try {
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store.close();
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} catch(DatabaseException dbe) {
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System.err.println("Error closing store: " +
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dbe.toString());
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System.exit(-1);
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}
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}
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if (myEnv != null) {
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try {
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// Finally, close the environment.
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myEnv.close();
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} catch(DatabaseException dbe) {
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System.err.println("Error closing MyDbEnv: " +
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dbe.toString());
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System.exit(-1);
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}
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}
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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="inventoryclass.html">Prev</a> </td>
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<td width="20%" align="center">
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<a accesskey="u" href="dpl_example.html">Up</a>
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</td>
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<td width="40%" align="right"> <a accesskey="n" href="dataaccessorclass.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">Inventory.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"> DataAccessor.class</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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