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| <title>5. MethodQL</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="ref_guide_runtime.html" title="Chapter 9. Runtime Extensions"><link rel="prev" href="ref_guide_savepoints.html" title="4. Savepoints"><link rel="next" href="ref_guide_sequence.html" title="6. Generators"></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. |
| MethodQL |
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| Runtime Extensions |
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| MethodQL |
| </h2></div></div></div> |
| |
| <a class="indexterm" name="d5e15788"></a> |
| <a class="indexterm" name="d5e15790"></a> |
| <p> |
| If JPQL and SQL queries do not match your needs, OpenJPA also allows you to name |
| a Java method to use to load a set of objects. In a <span class="emphasis"><em>MethodQL |
| </em></span> query, the query string names a static method to invoke to determine |
| the matching objects: |
| </p> |
| <pre class="programlisting"> |
| import org.apache.openjpa.persistence.*; |
| |
| ... |
| |
| // the method query language is 'openjpa.MethodQL'. |
| // set the query string to the target method to execute, prefixed by fullly- |
| // qualified class name. |
| // If a candidate class has been specified for the query, then if the class is |
| // in the candidate class' package or in the query imports, you can omit the |
| // package. If the method is in the candidate class, you can omit the class name |
| // and just specify the method name. |
| |
| OpenJPAEntityManager oem = OpenJPAPersistence.cast(emf); |
| OpenJPAQuery q = oem.createQuery("openjpa.MethodQL", "com.xyz.Finder.getByName"); |
| |
| // parameters are passed the same way as in standard queries |
| // but you have to declare the parameters with their types on the implementation |
| |
| // Unwrap the implementation and declare parameters with types in a |
| // comma-separated list |
| q.unwrap(org.apache.openjpa.kernel.Query.class) |
| .declareParameters("String firstName, String lastName"); |
| |
| q.setParameter("firstName", "Fred").setParameter("lastName", "Lucas"); |
| |
| // this executes the target method to get the results |
| List results = q.getResultList(); |
| |
| // The result is returned as a list but the element(s) in the list is determined |
| // by the returned value of the target method |
| |
| </pre> |
| <p> |
| For datastore queries, the method must have the following signature: |
| </p> |
| <pre class="programlisting"> |
| public static <a class="ulink" href="../../apidocs/org/apache/openjpa/lib/rop/ResultObjectProvider.html" target="_top">ResultObjectProvider</a> xxx(<a class="ulink" href="../../apidocs/org/apache/openjpa/kernel/StoreContext.html" target="_top">StoreContext</a> ctx, <a class="ulink" href="../../apidocs/org/apache/openjpa/meta/ClassMetaData.html" target="_top">ClassMetaData</a> meta, boolean subclasses, Map params, <a class="ulink" href="../javadoc/org/apache/openjpa/kernel/FetchConfiguration.html" target="_top">FetchConfiguration </a> fetch) |
| </pre> |
| <p> |
| The returned result object provider should produce objects of the candidate |
| class that match the method's search criteria. If the returned objects do not |
| have all fields in the given fetch configuration loaded, OpenJPA will make |
| additional trips to the datastore as necessary to fill in the data for the |
| missing fields. |
| </p> |
| <p> |
| In-memory execution is slightly different, taking in one object at a time and |
| returning a boolean on whether the object matches the query: |
| </p> |
| <pre class="programlisting"> |
| public static boolean xxx(<a class="ulink" href="../../apidocs/org/apache/openjpa/kernel/StoreContext.html" target="_top">StoreContext</a> ctx, <a class="ulink" href="../../apidocs/org/apache/openjpa/meta/ClassMetaData.html" target="_top">ClassMetaData</a> meta, boolean subclasses, Object obj, Map params, <a class="ulink" href="../../apidocs/org/apache/openjpa/kernel/FetchConfiguration.html" target="_top">FetchConfiguration</a> fetch) |
| </pre> |
| <p> |
| In both method versions, the given <code class="literal">params</code> map contains the |
| names and values of all the parameters for the query. |
| </p> |
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| Savepoints |
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| Generators |
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