je/docs/TransactionGettingStarted/enabletxn.html

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<title>Chapter 2. Enabling Transactions</title>
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<th colspan="3" align="center">Chapter 2. Enabling Transactions</th>
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<div class="chapter" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h2 class="title"><a id="enabletxn"></a>Chapter 2. Enabling Transactions</h2>
</div>
</div>
</div>
<div class="toc">
<p>
<b>Table of Contents</b>
</p>
<dl>
<dt>
<span class="sect1">
<a href="enabletxn.html#envopen">Opening a Transactional Environment and
<span>Store or Database</span>
</a>
</span>
</dt>
</dl>
</div>
<p>
In order to use transactions with your application, you must turn them
on. To do this you must:
</p>
<div class="itemizedlist">
<ul type="disc">
<li>
<p>
Turn on transactions for your environment.
<span>
You do this by using the
<code class="methodname">EnvironmentConfig.setTransactional()</code>
method<span>, or by using the
<code class="literal">je.env.isTransactional</code>
<code class="filename">je.properties</code> parameter</span>.
</span>
</p>
</li>
<li>
<p>
If you are using the DPL, transaction-enable your stores.
You do this by using the
<code class="methodname">StoreConfig.setTransactional() method.</code>
</p>
</li>
<li>
<p>
<span>
Transaction-enable your databases.
</span>
<span>
If you are using the base API, transaction-enable your databases.
</span>
You do this by
<span>
using the
<code class="methodname">DatabaseConfig.setTransactional()</code>
method, and then opening the database from within a transaction.
</span>
<span>
Note that the common practice is for auto commit to be used to
transaction-protect the database open. To use auto-commit, you
must still enable transactions as described here, but you do
not have to explicitly use a transaction when you open your
database. An example of this is given in the next section.
</span>
</p>
</li>
</ul>
</div>
<div class="sect1" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h2 class="title" style="clear: both"><a id="envopen"></a>Opening a Transactional Environment and
<span>Store or Database</span>
</h2>
</div>
</div>
</div>
<p>
To enable transactions for your environment, you must initialize the
transactional subsystem. For example, do this with the DPL:
</p>
<pre class="programlisting">package persist.txn;
import com.sleepycat.je.DatabaseException;
import com.sleepycat.je.Environment;
import com.sleepycat.je.EnvironmentConfig;
import com.sleepycat.persist.EntityStore;
import com.sleepycat.persist.StoreConfig;
import java.io.File;
...
Environment myEnv = null;
EntityStore myStore = null;
try {
EnvironmentConfig myEnvConfig = new EnvironmentConfig();
StoreConfig storeConfig = new StoreConfig();
myEnvConfig.setTransactional(true);
storeConfig.setTransactional(true);
myEnv = new Environment(new File("/my/env/home"),
myEnvConfig);
myStore = new EntityStore(myEnv, "EntityStore", storeConfig);
} catch (DatabaseException de) {
// Exception handling goes here
}</pre>
<p>
And when using the base API:
</p>
<pre class="programlisting">package je.txn;
import com.sleepycat.je.DatabaseException;
import com.sleepycat.je.Environment;
import com.sleepycat.je.EnvironmentConfig;
import java.io.File;
...
Environment myEnv = null;
try {
EnvironmentConfig myEnvConfig = new EnvironmentConfig();
myEnvConfig.setTransactional(true);
myEnv = new Environment(new File("/my/env/home"),
myEnvConfig);
} catch (DatabaseException de) {
// Exception handling goes here
}</pre>
<p>
You then create and open your database(s) as you would for a non-transactional system.
<span>
The only difference is that you must set
<code class="methodname">DatabaseConfig.setTransactional()</code>
to <code class="literal">true</code>. Note that your database open must be
transactional-protected. However, if you do not give the
<code class="methodname">openDatabase()</code> method a transaction handle,
then the open is automatically protected using auto commit.
Typically auto commit is used for this purpose.
For example:
</span>
</p>
<pre class="programlisting">package je.txn;
<strong class="userinput"><code>import com.sleepycat.je.Database;
import com.sleepycat.je.DatabaseConfig;</code></strong>
import com.sleepycat.je.DatabaseException;
import com.sleepycat.je.Environment;
import com.sleepycat.je.EnvironmentConfig;
import java.io.File;
...
<strong class="userinput"><code>Database myDatabase = null;</code></strong>
Environment myEnv = null;
try {
EnvironmentConfig myEnvConfig = new EnvironmentConfig();
myEnvConfig.setTransactional(true);
myEnv = new Environment(new File("/my/env/home"),
myEnvConfig);
<strong class="userinput"><code>// Open the database. Create it if it does not already exist.
DatabaseConfig dbConfig = new DatabaseConfig();
dbConfig.setTransactional(true);
myDatabase = myEnv.openDatabase(null,
"sampleDatabase",
dbConfig);</code></strong>
} catch (DatabaseException de) {
// Exception handling goes here
}
</pre>
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
<h3 class="title">Note</h3>
<p>
Never close a database <span> or
store </span> that has active transactions. Make sure
all transactions are resolved (either committed or aborted)
before closing the database.
</p>
</div>
</div>
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