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32            <h2 class="title" style="clear: both"><a id="CoreEnvUsage"></a>Managing Databases in Environments</h2>
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37      <p>
38            In 
39            
40            <span>
41            <a href="Env.html">Database Environments</a>, 
42            </span>
43            
44            we introduced
45        environments. While environments are not used in the example built in this book,
46        they are so commonly used for a wide class of DB applications that it is 
47        necessary to show their basic usage, if only from a completeness perspective.
48    </p>
49      <p>
50        To use an environment, you must first
51            
52        open it. At open time, you must identify the directory in 
53        which it resides. This directory must exist prior to the open attempt. 
54        You can also identify open properties, such as whether the environment can be
55        created if it does not already exist.
56    </p>
57      <p>
58        You will also need to initialize the in-memory cache when you open your environment.
59    </p>
60      <p>
61        For example, to 
62            <span>create an environment handle and</span>
63        open an environment:
64    </p>
65      <a id="java_env1"></a>
66      <pre class="programlisting">package db.GettingStarted;
67
68import com.sleepycat.db.DatabaseException;
69import com.sleepycat.db.Environment;
70import com.sleepycat.db.EnvironmentConfig;
71
72import java.io.File;
73import java.io.FileNotFoundException;
74
75...
76
77Environment myEnv = null;
78File envHome = new File("/export1/testEnv");
79try {
80    EnvironmentConfig envConf = new EnvironmentConfig();
81    envConf.setAllowCreate(true);         // If the environment does not
82                                          // exist, create it.
83    envConf.setInitializeCache(true);     // Initialize the in-memory
84                                          // cache.
85
86    myEnv = new Environment(envHome, envConf);
87} catch (DatabaseException de) {
88    // Exception handling goes here
89} catch (FileNotFoundException fnfe) {
90    // Exception handling goes here
91} </pre>
92      <p>
93        Once an environment is opened, you can open databases in it. Note that by default databases
94        are stored in the environment's home directory, or relative to that directory if you
95        provide any sort of a path in the database's file name:
96    </p>
97      <a id="java_env2"></a>
98      <pre class="programlisting">package db.GettingStarted;
99
100<b class="userinput"><tt>import com.sleepycat.db.Database;
101import com.sleepycat.db.DatabaseConfig;
102import com.sleepycat.db.DatabaseType;</tt></b>
103import com.sleepycat.db.DatabaseException;
104import com.sleepycat.db.Environment;
105import com.sleepycat.db.EnvironmentConfig;
106
107import java.io.File;
108import java.io.FileNotFoundException;
109
110...
111
112Environment myEnv = null;
113Database myDb = null;
114File envHome = new File("/export1/testEnv");
115String dbFileName = new String("mydb.db", "UTF-8");
116
117try {
118    EnvironmentConfig envConf = new EnvironmentConfig();
119    envConf.setAllowCreate(true);
120    DatabaseConfig dbConfig = new DatabaseConfig();
121    <b class="userinput"><tt>dbConfig.setAllowCreate(true);
122    dbConfig.setType(DatabaseType.BTREE);</tt></b>
123
124    myEnv = new Environment(envHome, envConf);
125    <b class="userinput"><tt>myDb = myEnv.openDatabase(null, dbFileName, null, dbConfig);</tt></b>
126} catch (DatabaseException de) {
127    // Exception handling goes here
128} catch (FileNotFoundException fnfe) {
129    // Exception handling goes here
130} </pre>
131      <p>
132        When you are done with an environment, you must close it. Before you close an environment,
133        make sure you close any opened databases.
134    </p>
135      <a id="java_env3"></a>
136      <pre class="programlisting">finally {
137    try {
138        if (myDb != null) {
139            myDb.close();
140        }
141
142        if (myEnv != null) {
143            myEnv.close();
144        }
145    } catch (DatabaseException de) {
146        // Exception handling goes here
147    }
148} </pre>
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