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| <title>12. Schema Reflection</title><link rel="stylesheet" href="css/docbook.css" type="text/css"><base href="display"><meta name="generator" content="DocBook XSL Stylesheets V1.72.0"><link rel="start" href="manual.html" title="Apache OpenJPA 2.1 User's Guide"><link rel="up" href="ref_guide_dbsetup.html" title="Chapter 4. JDBC"><link rel="prev" href="ref_guide_schema_def.html" title="11. Default Schema"><link rel="next" href="ref_guide_schema_schematool.html" title="13. Schema Tool"></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">12. |
| Schema Reflection |
| </th></tr><tr><td width="20%" align="left"><a accesskey="p" href="ref_guide_schema_def.html">Prev</a> </td><th width="60%" align="center">Chapter 4. |
| JDBC |
| </th><td width="20%" align="right"> <a accesskey="n" href="ref_guide_schema_schematool.html">Next</a></td></tr></table><hr></div><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="ref_guide_schema_info"></a>12. |
| Schema Reflection |
| </h2></div></div></div><div class="toc"><dl><dt><span class="section"><a href="ref_guide_schema_info.html#ref_guide_schema_info_list">12.1. |
| Schemas List |
| </a></span></dt><dt><span class="section"><a href="ref_guide_schema_info.html#ref_guide_schema_info_factory">12.2. |
| Schema Factory |
| </a></span></dt></dl></div><a class="indexterm" name="d0e24614"></a><p> |
| OpenJPA needs information about your database schema for two reasons. First, it |
| can use schema information at runtime to validate that your schema is compatible |
| with your persistent class definitions. Second, OpenJPA requires schema |
| information during development so that it can manipulate the schema to match |
| your object model. OpenJPA uses the <code class="literal">SchemaFactory</code> interface |
| to provide runtime mapping information, and the <code class="classname">SchemaTool |
| </code> for development-time data. Each is presented below. |
| </p><div class="section" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="ref_guide_schema_info_list"></a>12.1. |
| Schemas List |
| </h3></div></div></div><a class="indexterm" name="d0e24630"></a><a class="indexterm" name="d0e24633"></a><p> |
| By default, schema reflection acts on all the schemas your JDBC driver can |
| "see". You can limit the schemas and tables OpenJPA acts on with the <code class="literal"> |
| openjpa.jdbc.Schemas</code> configuration property. This property accepts a |
| comma-separated list of schemas and tables. To list a schema, list its name. To |
| list a table, list its full name in the form <code class="literal"> |
| <schema-name>.<table-name></code>. If a table does not have a |
| schema or you do not know its schema, list its name as <code class="literal"> |
| .<table-name></code> (notice the preceding '.'). For example, to list |
| the <code class="literal">BUSOBJS</code> schema, the <code class="literal">ADDRESS</code> table in |
| the <code class="literal">GENERAL</code> schema, and the <code class="literal">SYSTEM_INFO</code> |
| table, regardless of what schema it is in, use the string: |
| </p><pre class="programlisting"> |
| BUSOBJS,GENERAL.ADDRESS,.SYSTEM_INFO |
| </pre><div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3><p> |
| Some databases are case-sensitive with respect to schema and table names. |
| Oracle, for example, requires names in all upper case. |
| </p></div></div><div class="section" lang="en"><div class="titlepage"><div><div><h3 class="title"><a name="ref_guide_schema_info_factory"></a>12.2. |
| Schema Factory |
| </h3></div></div></div><a class="indexterm" name="d0e24669"></a><p> |
| OpenJPA relies on the |
| <a xmlns:xlink="http://www.w3.org/1999/xlink" href="../javadoc/org/apache/openjpa/jdbc/schema/SchemaFactory.html" target="_top"> |
| <code class="classname">openjpa.jdbc.SchemaFactory</code></a> interface for runtime |
| schema information. You can control the schema factory OpenJPA uses through the |
| <code class="literal">openjpa.jdbc.SchemaFactory</code> property. There are several |
| built-in options to choose from: |
| </p><div class="itemizedlist"><ul type="disc"><li><p> |
| <code class="literal">dynamic</code>: This is the default setting. It is an alias for the |
| <a xmlns:xlink="http://www.w3.org/1999/xlink" href="../javadoc/org/apache/openjpa/jdbc/schema/DynamicSchemaFactory.html" target="_top"> |
| <code class="classname"> |
| org.apache.openjpa.jdbc.schema.DynamicSchemaFactory</code></a>. The |
| <code class="classname">DynamicSchemaFactory</code> is the most performant |
| schema factory, because it does not validate mapping information against the |
| database. Instead, it assumes all object-relational mapping information is |
| correct, and dynamically builds an in-memory representation of the schema from |
| your mapping metadata. When using this factory, it is important that your |
| mapping metadata correctly represent your database's foreign key constraints so |
| that OpenJPA can order its SQL statements to meet them. |
| </p></li><li><p> |
| <code class="literal">native</code>: This is an alias for the |
| <a xmlns:xlink="http://www.w3.org/1999/xlink" href="../javadoc/org/apache/openjpa/jdbc/schema/LazySchemaFactory.html" target="_top"> |
| <code class="classname">org.apache.openjpa.jdbc.schema.LazySchemaFactory</code></a> |
| . As persistent classes are loaded by the application, OpenJPA reads their |
| metadata and object-relational mapping information. This factory uses the |
| <code class="classname">java.sql.DatabaseMetaData</code> interface to reflect on the |
| schema and ensure that it is consistent with the mapping data being read. |
| Use this factory if you want up-front validation that your mapping metadata is |
| consistent with the database during development. This factory accepts the |
| following important properties: |
| </p><div class="itemizedlist"><ul type="circle"><li><p> |
| <code class="literal">ForeignKeys</code>: Set to <code class="literal">true</code> to automatically |
| read foreign key information during schema validation. |
| </p></li></ul></div></li><li><p> |
| <code class="literal">table</code>: This is an alias for the |
| <a xmlns:xlink="http://www.w3.org/1999/xlink" href="../javadoc/org/apache/openjpa/jdbc/schema/TableSchemaFactory.html" target="_top"> |
| <code class="classname">org.apache.openjpa.jdbc.schema.TableSchemaFactory</code></a> |
| . This schema factory stores schema information as an XML document in a database |
| table it creates for this purpose. If your JDBC driver doesn't support the |
| <code class="classname">java.sql.DatabaseMetaData</code> standard interface, but you |
| still want some schema validation to occur at runtime, you might use this |
| factory. It is not recommended for most users, though, because it is easy for |
| the stored XML schema definition to get out-of-synch with the actual database. |
| This factory accepts the following properties: |
| </p><div class="itemizedlist"><ul type="circle"><li><p> |
| <code class="literal">Table</code>: The name of the table to create to store schema |
| information. Defaults to <code class="literal">OPENJPA_SCHEMA</code>. |
| </p></li><li><p> |
| <code class="literal">PrimaryKeyColumn</code>: The name of the table's numeric primary |
| key column. Defaults to <code class="literal">ID</code>. |
| </p></li><li><p> |
| <code class="literal">SchemaColumn</code>: The name of the table's string column for |
| holding the schema definition as an XML string. Defaults to <code class="literal">SCHEMA_DEF |
| </code>. |
| </p></li></ul></div></li><li><p> |
| <code class="literal">file</code>: This is an alias for the |
| <a xmlns:xlink="http://www.w3.org/1999/xlink" href="../javadoc/org/apache/openjpa/jdbc/schema/FileSchemaFactory.html" target="_top"> |
| <code class="classname">org.apache.openjpa.jdbc.schema.FileSchemaFactory</code></a> |
| . This factory is a lot like the <code class="classname">TableSchemaFactory</code>, and |
| has the same advantages and disadvantages. Instead of storing its XML schema |
| definition in a database table, though, it stores it in a file. This factory |
| accepts the following properties: |
| </p><div class="itemizedlist"><ul type="circle"><li><p> |
| <code class="literal">File</code>: The resource name of the XML schema file. By default, |
| the factory looks for a resource called <code class="filename"> package.schema</code>, |
| located in any top-level directory of the <code class="literal">CLASSPATH</code> or in the |
| top level of any jar in your <code class="literal">CLASSPATH</code>. |
| </p></li></ul></div></li></ul></div><p> |
| You can switch freely between schema factories at any time. The XML file format |
| used by some factories is detailed in <a href="ref_guide_schema_xml.html" title="14. XML Schema Format">Section 14, “ |
| XML Schema Format |
| ”</a> |
| . As with any OpenJPA plugin, you can also implement your own schema |
| factory if you have needs not met by the existing options. |
| </p></div></div><div class="navfooter"><hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="ref_guide_schema_def.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="ref_guide_dbsetup.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="ref_guide_schema_schematool.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">11. |
| Default Schema |
| </td><td width="20%" align="center"><a accesskey="h" href="manual.html">Home</a></td><td width="40%" align="right" valign="top"> 13. |
| Schema Tool |
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