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| <title>5. Cache Management</title><base href="display"><link rel="stylesheet" type="text/css" href="css/docbook.css"><meta name="generator" content="DocBook XSL Stylesheets V1.79.1"><link rel="home" href="manual.html" title="Apache OpenJPA 3.0 User's Guide"><link rel="up" href="jpa_overview_em.html" title="Chapter 8. EntityManager"><link rel="prev" href="jpa_overview_em_identity.html" title="4. Entity Identity Management"><link rel="next" href="jpa_overview_em_query.html" title="6. Query Factory"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">5. |
| Cache Management |
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| EntityManager |
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| Cache Management |
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| |
| <a class="indexterm" name="d5e2615"></a> |
| <pre class="programlisting"> |
| public void flush(); |
| </pre> |
| <p> |
| <a class="indexterm" name="d5e2620"></a> |
| <a class="indexterm" name="d5e2623"></a> |
| <a class="indexterm" name="d5e2626"></a> |
| The <code class="methodname">flush</code> method writes any changes that have been made |
| in the current transaction to the datastore. If the <code class="classname">EntityManager |
| </code> does not already have a connection to the datastore, it obtains one |
| for the flush and retains it for the duration of the transaction. Any exceptions |
| during flush cause the transaction to be marked for rollback. See |
| <a class="xref" href="jpa_overview_trans.html" title="Chapter 9. Transaction">Chapter 9, <i> |
| Transaction |
| </i></a>. |
| </p> |
| <p> |
| Flushing requires an active transaction. If there isn't a transaction in |
| progress, the <code class="methodname">flush</code> method throws a <code class="classname"> |
| TransactionRequiredException</code>. |
| </p> |
| <pre class="programlisting"> |
| public FlushModeType getFlushMode(); |
| public void setFlushMode(FlushModeType flushMode); |
| </pre> |
| <p> |
| <a class="indexterm" name="d5e2637"></a> |
| <a class="indexterm" name="d5e2640"></a> |
| The <code class="classname">EntityManager</code>'s <code class="literal">FlushMode</code> property |
| controls whether to flush transactional changes before executing queries. This |
| allows the query results to take into account changes you have made during the |
| current transaction. Available |
| <a class="ulink" href="http://download.oracle.com/javaee/6/api/javax/persistence/FlushModeType.html" target="_top"> |
| <code class="classname">javax.persistence.FlushModeType</code></a> constants are: |
| </p> |
| <div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"> |
| <p> |
| <code class="literal">COMMIT</code>: Only flush when committing, or when told to do so |
| through the <code class="methodname">flush</code> method. Query results may not take |
| into account changes made in the current transaction. |
| </p> |
| </li><li class="listitem"> |
| <p> |
| <code class="literal">AUTO</code>: The implementation is permitted to flush before |
| queries to ensure that the results reflect the most recent object state. |
| </p> |
| </li></ul></div> |
| <p> |
| You can also set the flush mode on individual |
| <a class="link" href="jpa_overview_query.html" title="Chapter 10. JPA Query"><code class="classname">Query</code></a> |
| instances. |
| </p> |
| <div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3> |
| <p> |
| OpenJPA only flushes before a query if the query might be affected by data |
| changed in the current transaction. Additionally, OpenJPA allows fine-grained |
| control over flushing behavior. See the Reference Guide's |
| <a class="xref" href="ref_guide_dbsetup_retain.html" title="8. Configuring the Use of JDBC Connections">Section 8, “ |
| Configuring the Use of JDBC Connections |
| ”</a>. |
| </p> |
| </div> |
| <pre class="programlisting"> |
| public void clear(); |
| </pre> |
| <p> |
| <a class="indexterm" name="d5e2662"></a> |
| <a class="indexterm" name="d5e2665"></a> |
| Clearing the <code class="classname">EntityManager</code> effectively ends the |
| persistence context. All entities managed by the <code class="classname">EntityManager |
| </code> become detached. |
| </p> |
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| Entity Identity Management |
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| Query Factory |
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