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289 lines
9.1 KiB
XML
289 lines
9.1 KiB
XML
<!DOCTYPE chapter PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN" "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd">
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<sect1 id="sql_integration" revision="1">
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<title>Querying SQL/JDBC sources</title>
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<para>This chapter describes the query type generation and querying functionality of the SQL module.</para>
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<sect2>
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<title>Creating the Querydsl query types</title>
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<para>To get started export your schema into Querydsl query types like this :</para>
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<programlisting language="java"><![CDATA[
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java.sql.Connection conn; // connection of database containing the schema to use
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// obtain Connection etc.
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NamingStrategy namingStrategy = new DefaultNamingStrategy();
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MetaDataSerializer serializer = new MetaDataSerializer("Q",namingStrategy);
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MetaDataExporter exporter = new MetaDataExporter(
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"Q", // namePrefix
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"com.myproject.mydomain", // target package
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new File("src/main/java"), // target source folder
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namingStrategy, // naming strategy
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serializer); // serializer
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exporter.export(conn.getMetaData());
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]]></programlisting>
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<para>This declares that the database schema is to be mirrored into the com.myproject.domain package in the src/main/java folder.</para>
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<para>
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The generated types have the table name transformed to mixed case as the class name and a similar mixed case transformation
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applied to the columns which are available as property paths in the query type.
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</para>
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</sect2>
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<sect2>
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<title>Maven integration</title>
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<para>This functionality is also available as a Maven plugin. The presented example can be declared like this in the POM :</para>
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<programlisting language="xml"><![CDATA[
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<plugin>
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<groupId>com.mysema.querydsl</groupId>
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<artifactId>querydsl-maven-plugin</artifactId>
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<version>${querydsl.version}</version>
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<executions>
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<execution>
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<goals>
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<goal>export</goal>
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</goals>
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</execution>
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</executions>
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<configuration>
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<jdbcDriver>org.apache.derby.jdbc.EmbeddedDriver</jdbcDriver>
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<jdbcUrl>jdbc:derby:target/demoDB;create=true</jdbcUrl>
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<!--
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optional elements :
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* namePrefix
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* jdbcUser
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* jdbcPassword
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* schemaPattern
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* tableNamePattern
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-->
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<packageName>com.myproject.domain</packageName>
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<targetFolder>target/generated-sources/java</targetFolder>
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</configuration>
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<dependencies>
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<dependency>
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<groupId>org.apache.derby</groupId>
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<artifactId>derby</artifactId>
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<version>${derby.version}</version>
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</dependency>
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</dependencies>
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</plugin>
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]]></programlisting>
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<para>Use the goal <emphasis>test-export</emphasis> to add the targetFolder as a test compile source root
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instead of a compile source root.</para>
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</sect2>
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<sect2>
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<title>Querying</title>
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<para>Querying with Querydsl SQL is as simple as this :</para>
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<programlisting language="java"><![CDATA[
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QCustomer customer = new QCustomer("c");
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SQLTemplates dialect = new HSQLDBTemplates(); // SQL-dialect
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SQLQuery query = SQLQueryImpl(connection, dialect);
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List<String> lastNames = query.from(customer)
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.where(customer.firstName.eq("Bob"))
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.list(customer.lastName);
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]]></programlisting>
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<para>which is transformed into the following sql query, assuming that the related table name is
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<emphasis>customer</emphasis> and the columns <emphasis>first_name</emphasis> and
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<emphasis>last_name</emphasis> :</para>
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<programlisting><![CDATA[
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SELECT c.last_name
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FROM customer c
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WHERE c.first_name = 'Bob'
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]]></programlisting>
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<para>Internally Querydsl SQL uses PreparedStatements, though.</para>
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<para>Querydsl uses SQL dialects to customize the SQL serialization needed for different relational databases. The
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available dialects are :</para>
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<itemizedlist>
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<listitem>
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<para>com.mysema.query.sql.DerbyTemplates</para>
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<itemizedlist>
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<listitem><para>tested with version 10.5.3</para></listitem>
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</itemizedlist>
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</listitem>
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<listitem>
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<para>com.mysema.query.sql.HSQLDBTemplates</para>
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<itemizedlist>
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<listitem><para>tested with version 1.8.0.7</para></listitem>
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</itemizedlist>
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</listitem>
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<listitem>
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<para>com.mysema.query.sql.MySQLTemplates</para>
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<itemizedlist>
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<listitem><para>tested with MySQL CE 5.1</para></listitem>
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</itemizedlist>
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</listitem>
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<listitem>
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<para>com.mysema.query.sql.OracleTemplates</para>
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<itemizedlist>
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<listitem><para>tested with Oracle 10g XE</para></listitem>
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</itemizedlist>
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</listitem>
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<listitem>
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<para>com.mysema.query.sql.PostgresTemplates</para>
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<itemizedlist>
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<listitem><para>tested with Postgres 8.4</para></listitem>
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</itemizedlist>
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</listitem>
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<listitem>
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<para>com.mysema.query.sql.SQLServerTemplates</para>
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<itemizedlist>
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<listitem><para>tested with SQL Server 2008</para></listitem>
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</itemizedlist>
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</listitem>
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</itemizedlist>
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</sect2>
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<sect2>
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<title>General usage</title>
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<para>Use the the cascading methods of the SQLQuery interface like this</para>
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<para><emphasis>from :</emphasis> Define the query sources here.</para>
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<para><emphasis>innerJoin, join, leftJoin, fullJoin, on</emphasis> : Define join elements using these constructs.
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For the join methods the first argument is the join source and the second the target (alias).</para>
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<para><emphasis>where :</emphasis> Define the query filters, either in varargs form separated via commas or
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cascaded via the and-operator.</para>
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<para><emphasis>groupBy :</emphasis> Define the group by arguments in varargs form.</para>
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<para><emphasis>having :</emphasis> Define the having filter of the "group by" grouping as an varags array of
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EBoolean expressions.</para>
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<para><emphasis>orderBy :</emphasis> Define the ordering of the result as an varargs array of order expressions.
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Use asc() and desc() on numeric, string and other comparable expression to access the OrderSpecifier instances. </para>
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<para><emphasis>limit, offset, restrict :</emphasis> Define the paging of the result. Limit for max results,
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offset for skipping rows and restrict for defining both in one call.</para>
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</sect2>
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<sect2>
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<title>Ordering</title>
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<para>The syntax for declaring ordering is </para>
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<programlisting language="java"><![CDATA[
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query.from(customer)
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.orderBy(customer.lastName.asc(), customer.firstName.asc())
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.list(customer.firstName, customer.lastName);
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]]></programlisting>
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<para>which is equivalent to the following native SQL</para>
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<programlisting>
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SELECT c.first_name, c.last_name
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FROM customer c
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ORDER BY c.last_name ASC, c.first_name ASC
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</programlisting>
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</sect2>
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<sect2>
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<title>Grouping</title>
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<para>Grouping can be done in the following form</para>
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<programlisting language="java"><![CDATA[
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query.from(customer)
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.groupBy(customer.lastName)
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.list(customer.lastName);
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]]></programlisting>
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<para>which is equivalent to the following native SQL</para>
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<programlisting>
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SELECT c.last_name
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FROM customer c
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GROUP BY c.last_name
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</programlisting>
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</sect2>
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<sect2>
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<title>Using Data manipulation commands</title>
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<para>Insert examples :</para>
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<programlisting language="java"><![CDATA[
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// with columns
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insert(survey)
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.columns(survey.id, survey.name)
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.values(3, "Hello").execute();
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// without columns
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insert(survey)
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.values(4, "Hello").execute();
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// with subquery
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insert(survey)
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.columns(survey.id, survey.name)
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.select(s().from(survey2).list(survey2.id.add(1), survey2.name))
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.execute();
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// with subquery, without columns
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insert(survey)
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.select(s().from(survey2).list(survey2.id.add(10), survey2.name))
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.execute();
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]]></programlisting>
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<para>Using the following methods :</para>
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<programlisting language="java"><![CDATA[
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protected SQLInsertClause insert(PEntity<?> e){
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return new SQLInsertClause(getConnection(), dialect, e);
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}
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protected SQLSubQuery s(){
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return new SQLSubQuery();
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}
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]]></programlisting>
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<para>Update examples :</para>
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<programlisting language="java"><![CDATA[
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// update with where
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update(survey).where(survey.name.eq("XXX")).set(survey.name, "S").execute();
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// update without where
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update(survey).set(survey.name, "S").execute()
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]]></programlisting>
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<para>Using the following methods :</para>
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<programlisting language="java"><![CDATA[
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protected SQLUpdateClause update(PEntity<?> e){
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return new SQLUpdateClause(Connections.getConnection(), dialect, e);
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}
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]]></programlisting>
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</sect2>
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</sect1> |