1<?xml version="1.0" encoding="UTF-8" standalone="no"?> 2<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> 3<html xmlns="http://www.w3.org/1999/xhtml"> 4 <head> 5 <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /> 6 <title>Chapter��7.��Databases</title> 7 <link rel="stylesheet" href="gettingStarted.css" type="text/css" /> 8 <meta name="generator" content="DocBook XSL Stylesheets V1.73.2" /> 9 <link rel="start" href="index.html" title="Getting Started with Berkeley DB" /> 10 <link rel="up" href="baseapi.html" title="Part��II.��Programming with the Base API" /> 11 <link rel="prev" href="baseapi.html" title="Part��II.��Programming with the Base API" /> 12 <link rel="next" href="coredbclose.html" title="Closing Databases" /> 13 </head> 14 <body> 15 <div class="navheader"> 16 <table width="100%" summary="Navigation header"> 17 <tr> 18 <th colspan="3" align="center">Chapter��7.��Databases</th> 19 </tr> 20 <tr> 21 <td width="20%" align="left"><a accesskey="p" href="baseapi.html">Prev</a>��</td> 22 <th width="60%" align="center">Part��II.��Programming with the Base API</th> 23 <td width="20%" align="right">��<a accesskey="n" href="coredbclose.html">Next</a></td> 24 </tr> 25 </table> 26 <hr /> 27 </div> 28 <div class="chapter" lang="en" xml:lang="en"> 29 <div class="titlepage"> 30 <div> 31 <div> 32 <h2 class="title"><a id="DB"></a>Chapter��7.��Databases</h2> 33 </div> 34 </div> 35 </div> 36 <div class="toc"> 37 <p> 38 <b>Table of Contents</b> 39 </p> 40 <dl> 41 <dt> 42 <span class="sect1"> 43 <a href="DB.html#DBOpen">Opening Databases</a> 44 </span> 45 </dt> 46 <dt> 47 <span class="sect1"> 48 <a href="coredbclose.html">Closing Databases</a> 49 </span> 50 </dt> 51 <dt> 52 <span class="sect1"> 53 <a href="DBConfig.html">Database Properties</a> 54 </span> 55 </dt> 56 <dt> 57 <span class="sect1"> 58 <a href="DBAdmin.html">Administrative Methods</a> 59 </span> 60 </dt> 61 <dt> 62 <span class="sect1"> 63 <a href="dbErrorReporting.html">Error Reporting Functions</a> 64 </span> 65 </dt> 66 <dt> 67 <span class="sect1"> 68 <a href="CoreEnvUsage.html">Managing Databases in Environments</a> 69 </span> 70 </dt> 71 <dt> 72 <span class="sect1"> 73 <a href="CoreJavaUsage.html">Database Example</a> 74 </span> 75 </dt> 76 </dl> 77 </div> 78 <p>In Berkeley DB, a database is a collection of <span class="emphasis"><em>records</em></span>. Records, 79 in turn, consist of key/data pairings. 80 </p> 81 <p> 82 Conceptually, you can think of a 83 <code class="classname">Database</code> 84 85 as containing a two-column table where column 1 contains a key and column 2 86 contains data. Both the key and the data are managed using 87 <code class="classname">DatabaseEntry</code> 88 89 90 <span>class instances</span> 91 92 (see <a class="xref" href="DBEntry.html" title="Chapter��8.��Database Records">Database Records</a> for details on this 93 <span>class</span> 94 ). 95 So, fundamentally, using a DB 96 <code class="classname">Database</code> 97 98 involves putting, getting, and deleting database records, which in turns involves efficiently 99 managing information 100 <span>encapsulated by </span> 101 102 103 <code class="classname">DatabaseEntry</code> 104 105 106 107 <span>objects.</span> 108 109 The next several chapters of this book are dedicated to those activities. 110 </p> 111 <p> 112 Also, note that in the previous section of this book, <a class="xref" href="dpl.html" title="Part��I.��Programming with the Direct Persistence Layer">Programming with the Direct Persistence Layer</a>, 113 we described the DPL The DPL handles all database management 114 for you, including creating all primary and secondary databases as is 115 required by your application. That said, if you are using the DPL 116 you can access the underlying database for a given index if 117 necessary. See the Javadoc for the DPL for more information. 118 </p> 119 <div class="sect1" lang="en" xml:lang="en"> 120 <div class="titlepage"> 121 <div> 122 <div> 123 <h2 class="title" style="clear: both"><a id="DBOpen"></a>Opening Databases</h2> 124 </div> 125 </div> 126 </div> 127 <p> 128 You open a database by instantiating a <code class="classname">Database</code> 129 object. 130 </p> 131 <p> 132 Note that by default, DB does not create databases if they do not already exist. 133 To override this behavior, set the <a class="link" href="DBConfig.html" title="Database Properties">creation property</a> to true. 134 </p> 135 <p> 136 The following code fragment illustrates a database open: 137 138 </p> 139 <a id="java_db1"></a> 140 <pre class="programlisting">package db.GettingStarted; 141 142import com.sleepycat.db.DatabaseException; 143import com.sleepycat.db.Database; 144import com.sleepycat.db.DatabaseConfig; 145 146import java.io.FileNotFoundException; 147... 148 149Database myDatabase = null; 150 151... 152 153try { 154 // Open the database. Create it if it does not already exist. 155 DatabaseConfig dbConfig = new DatabaseConfig(); 156 dbConfig.setAllowCreate(true); 157 myDatabase = new Database ("sampleDatabase.db", 158 null, 159 dbConfig); 160} catch (DatabaseException dbe) { 161 // Exception handling goes here 162} catch (FileNotFoundException fnfe) { 163 // Exception handling goes here 164}</pre> 165 </div> 166 </div> 167 <div class="navfooter"> 168 <hr /> 169 <table width="100%" summary="Navigation footer"> 170 <tr> 171 <td width="40%" align="left"><a accesskey="p" href="baseapi.html">Prev</a>��</td> 172 <td width="20%" align="center"> 173 <a accesskey="u" href="baseapi.html">Up</a> 174 </td> 175 <td width="40%" align="right">��<a accesskey="n" href="coredbclose.html">Next</a></td> 176 </tr> 177 <tr> 178 <td width="40%" align="left" valign="top">Part��II.��Programming with the Base API��</td> 179 <td width="20%" align="center"> 180 <a accesskey="h" href="index.html">Home</a> 181 </td> 182 <td width="40%" align="right" valign="top">��Closing Databases</td> 183 </tr> 184 </table> 185 </div> 186 </body> 187</html> 188