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updated docs
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Timo Westkämper
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@ -4,12 +4,206 @@
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<title>Querying in Scala</title>
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<para>TODO</para>
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<para>Generic support for Querydsl usage in Scala is available via querydsl-scala module. To add it to your Maven build, use the following snippet :</para>
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<!--
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* DSL expressions for Scala
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* Querying with SQL
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* Querying with other backends
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-->
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<programlisting language="xml"><![CDATA[
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<dependency>
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<groupId>com.mysema.querydsl</groupId>
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<artifactId>querydsl-scala</artifactId>
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<version>${querydsl.version}</version>
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</dependency>
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]]></programlisting>
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<sect2>
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<title>DSL expressions for Scala</title>
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<para>Querydsl for Scala provides an alternative DSL for expression construction. The Scala DSL utilizes language features such as operator overloading,
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function pointers and implicit imports for enhanced readability and conciseness.</para>
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<para>Here is an overview of the main alternatives :</para>
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<programlisting><![CDATA[
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Standard Enhanced
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expr isNotNull expr is not(null)
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expr isNull expr is null
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expr eq "Ben" expr === "Ben"
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expr ne "Ben" expr !== "Ben"
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expr append "X" expr + "X"
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expr isEmpty expr is empty
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expr isNotEmpoty expr not empty
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// boolean
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left and right left && right
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left or right left || right
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expr not !expr
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// comparison
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expr lt 5 expr < 5
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expr loe 5 expr <= 5
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expr gt 5 expr > 5
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expr notBetween(2,6) expr not between (2,6)
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expr negate -expr
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// numeric
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expr add 3 expr + 3
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expr subtract 3 expr - 3
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expr divide 3 expr / 3
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expr multiply 3 expr * 3
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expr mod 5 expr % 5
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list.get(0) list(0)
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map.get("X") map("X")
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]]></programlisting>
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</sect2>
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<sect2>
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<title>Querying with SQL</title>
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<para>
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Like with Querydsl SQL for Java you need to generate Query types to be able to construct your queries.
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The following two unit test methods show how this is done :</para>
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<programlisting language="java"><![CDATA[
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@Test
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def Generation_without_Beantypes() {
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val namingStrategy = new DefaultNamingStrategy();
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val exporter = new MetaDataExporter();
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exporter.setNamePrefix("Q");
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exporter.setPackageName("test");
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exporter.setTargetFolder(new File("target/gen1"));
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exporter.setSerializerClass(classOf[ScalaMetaDataSerializer]);
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exporter.setCreateScalaSources(true);
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exporter.setTypeMappings(ScalaTypeMappings.create);
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exporter.export(connection.getMetaData);
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}
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@Test
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def Generation_with_Beantypes() {
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val namingStrategy = new DefaultNamingStrategy();
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val beanSerializer = new ScalaBeanSerializer();
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val exporter = new MetaDataExporter();
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exporter.setNamePrefix("Q");
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exporter.setPackageName("test");
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exporter.setTargetFolder(new File("target/gen2"));
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exporter.setSerializerClass(classOf[ScalaMetaDataSerializer]);
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exporter.setBeanSerializer(beanSerializer)
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exporter.setCreateScalaSources(true);
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exporter.setTypeMappings(ScalaTypeMappings.create);
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exporter.export(connection.getMetaData);
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}
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]]></programlisting>
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</sect2>
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<sect2>
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<title>Querying with other backends</title>
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<para>When querying with other backends the Expression model has to be created manually or alternatively the alias functionality can be used.</para>
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<para>Here is a minimal example with JPA/Hibernate :</para>
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<programlisting language="java"><![CDATA[
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@Entity
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class User {
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@BeanProperty
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@Id
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var id: Integer = _;
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@BeanProperty
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var userName: String = _;
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@BeanProperty
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@ManyToOne
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var department: Department = _;
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}
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@Entity
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class Department {
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@BeanProperty
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@Id
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var id: Integer = _;
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@BeanProperty
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var name: String = _;
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}
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]]></programlisting>
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<para>And here are some query examples</para>
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<programlisting language="java"><![CDATA[
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import com.mysema.query.scala.Conversions._
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import com.mysema.query.jpa.impl.JPAQuery
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import com.mysema.query.types.path._
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import org.junit.Test
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class JPAQueryTest {
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val person = alias(classOf[Person])
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@Test
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def Various() {
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// list
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query from person where (person.firstName $like "Rob%")
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.list person
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// unique result
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query from person where (person.firstName $like "Rob%")
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.unique person
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// long where
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query from person
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.where (person.firstName $like "Rob%", person.lastName $like "An%")
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.list person
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// order
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query from person orderBy (person.firstName asc) list person
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// not null
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query from person
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.where (person.firstName $isEmpty, person.lastName $isNotNull)
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.list person
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}
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def query() = new JPAQuery(entityManager)
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}
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]]></programlisting>
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<para>The main import for Querydsl Scala integration is the following</para>
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<programlisting language="java"><![CDATA[
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import com.mysema.query.scala.Conversions._
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]]></programlisting>
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<para>The factory method for query creation is</para>
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<programlisting language="java"><![CDATA[
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def query() = new JPAQuery(entityManager)
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]]></programlisting>
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<para>In addition to queries you need variables which can be created like this</para>
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<programlisting language="java"><![CDATA[
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var person = alias(classOf[Person])
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]]></programlisting>
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<para>The person variable is a proxy instance of the the Person class which can be used in queries. Now you can construct your queries, populate them via from-where-...-orderBy calls and get the projection out via list/uniqueResult/listResults calls.</para>
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<para>Querydsl expressions are constructed via method calls starting with the "$" sign.</para>
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<para>>With the Querydsl Java API a simple like expression would be constructed like this :</para>
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<programlisting language="java"><![CDATA[
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person.firstName.like("Rob%")
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]]></programlisting>
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<para>Using the Scala API it is</para>
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<programlisting language="java"><![CDATA[
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person.firstName $like "Rob%"
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]]></programlisting>
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</sect2>
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</sect1>
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@ -65,7 +65,7 @@ class JDBCIntegrationTest {
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exporter.setSerializerClass(classOf[ScalaMetaDataSerializer]);
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exporter.setCreateScalaSources(true);
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exporter.setTypeMappings(ScalaTypeMappings.create);
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exporter.export(connection.getMetaData());
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exporter.export(connection.getMetaData);
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}
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@Test
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@ -80,7 +80,7 @@ class JDBCIntegrationTest {
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exporter.setBeanSerializer(beanSerializer)
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exporter.setCreateScalaSources(true);
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exporter.setTypeMappings(ScalaTypeMappings.create);
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exporter.export(connection.getMetaData());
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exporter.export(connection.getMetaData);
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}
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@Test
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