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<h2 id="savepoint">Savepoint</h2>
<p>
Ebean supports using <code>Savepoints</code> which are a feature of most Relational Databases
in which we can create a Savepoint (nested transaction) inside a transaction which can
commit or rollback as a unit of work.
</p>
<p>
If we have a task that performs some operations which can fail/rollback, but don't
want to loose all the work for the entire transaction <code>Savepoint</code> provides a mechanism to do this.
You can check more information on <a href='https://docs.oracle.com/javase/tutorial/jdbc/basics/transactions.html#set_roll_back_savepoints'>Oracle's JDBC tutorial</a>
</p>
<h2 id="setNestedUseSavepoint">Transaction.setNestedUseSavepoint()</h2>
<p>
For a transaction we can use <code>transaction.setNestedUseSavepoint()</code> to enable it to use
<code>Savepoint</code> for nested transactions. This means that these nested transactions
can be rolled back leaving the outer transaction to continue and potentially commit.
</p>
<h5>Example</h5>
<div class="syntax java"><div class="highlight"><pre><span></span><span class="c1">// start 'outer' transaction</span>
<span class="k">try</span> <span class="o">(</span><span class="n">Transaction</span> <span class="n">outerTxn</span> <span class="o">=</span> <span class="n">database</span><span class="o">.</span><span class="na">beginTransaction</span><span class="o">())</span> <span class="o">{</span>
<span class="n">outerTxn</span><span class="o">.</span><span class="na">setNestedUseSavepoint</span><span class="o">();</span>
<span class="c1">// do stuff with the 'outer' transaction</span>
<span class="n">bean</span><span class="o">.</span><span class="na">save</span><span class="o">();</span>
<span class="k">try</span> <span class="o">(</span><span class="n">Transaction</span> <span class="n">nestedTransaction</span> <span class="o">=</span> <span class="n">database</span><span class="o">.</span><span class="na">beginTransaction</span><span class="o">())</span> <span class="o">{</span>
<span class="c1">// nested transaction is a savepoint ...</span>
<span class="c1">// do some piece of work which we might want to either commit or rollback ...</span>
<span class="n">otherBean</span><span class="o">.</span><span class="na">save</span><span class="o">();</span>
<span class="k">if</span> <span class="o">(...)</span> <span class="o">{</span>
<span class="n">nestedTransaction</span><span class="o">.</span><span class="na">rollback</span><span class="o">();</span>
<span class="o">}</span> <span class="k">else</span> <span class="o">{</span>
<span class="n">nestedTransaction</span><span class="o">.</span><span class="na">commit</span><span class="o">();</span>
<span class="o">}</span>
<span class="o">}</span>
<span class="c1">// continue using 'outer' transaction ...</span>
<span class="n">outerTxn</span><span class="o">.</span><span class="na">commit</span><span class="o">();</span>
<span class="o">}</span>
</pre></div>
</div>
<h2 id="explicit">Explicit Savepoints</h2>
<p>
As an alternative to using <em>transaction.setNestedUseSavepoint()</em> we can instead
explicitly create and use savepoints by obtaining the JDBC <code>Connection</code> from the transaction.
</p>
<p>
For example:
</p>
<div class="syntax java"><div class="highlight"><pre><span></span><span class="k">var</span> <span class="n">newCustomer</span> <span class="o">=</span> <span class="k">new</span> <span class="n">Customer</span><span class="o">();</span>
<span class="n">newCustomer</span><span class="o">.</span><span class="na">setName</span><span class="o">(</span><span class="s">"John"</span><span class="o">);</span>
<span class="n">newCustomer</span><span class="o">.</span><span class="na">save</span><span class="o">();</span>
<span class="k">try</span> <span class="o">(</span><span class="n">Transaction</span> <span class="n">transaction</span> <span class="o">=</span> <span class="n">DB</span><span class="o">.</span><span class="na">beginTransaction</span><span class="o">())</span> <span class="o">{</span>
<span class="n">Connection</span> <span class="n">connection</span> <span class="o">=</span> <span class="n">transaction</span><span class="o">.</span><span class="na">getConnection</span><span class="o">();</span>
<span class="c1">// create a Savepoint</span>
<span class="n">Savepoint</span> <span class="n">savepoint</span> <span class="o">=</span> <span class="n">connection</span><span class="o">.</span><span class="na">setSavepoint</span><span class="o">();</span>
<span class="n">newCustomer</span><span class="o">.</span><span class="na">setName</span><span class="o">(</span><span class="s">"Doe"</span><span class="o">);</span>
<span class="n">newCustomer</span><span class="o">.</span><span class="na">save</span><span class="o">();</span>
<span class="c1">// Rollback to a specific save point</span>
<span class="n">connection</span><span class="o">.</span><span class="na">rollback</span><span class="o">(</span><span class="n">savepoint</span><span class="o">);</span>
<span class="n">transaction</span><span class="o">.</span><span class="na">commit</span><span class="o">();</span>
<span class="o">}</span>
<span class="k">var</span> <span class="n">found</span> <span class="o">=</span> <span class="n">DB</span><span class="o">.</span><span class="na">find</span><span class="o">(</span><span class="n">Customer</span><span class="o">.</span><span class="na">class</span><span class="o">,</span> <span class="n">newCustomer</span><span class="o">.</span><span class="na">getId</span><span class="o">());</span>
<span class="n">System</span><span class="o">.</span><span class="na field">out</span><span class="o">.</span><span class="na">println</span><span class="o">(</span><span class="n">found</span><span class="o">.</span><span class="na">getName</span><span class="o">());</span> <span class="c1">// Prints "John"</span>
</pre></div>
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