docs/docbook/getting-started/src/docbkx/object-context.xml

<?xml version="1.0" encoding="UTF-8"?>
<?xml-model href="http://www.oasis-open.org/docbook/xml/5.0/rng/docbook.rng" schematypens="http://relaxng.org/ns/structure/1.0"?>
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<section xmlns="http://docbook.org/ns/docbook"
    xmlns:xlink="http://www.w3.org/1999/xlink" version="5.0">
    <title>Getting started with ObjectContext</title>
    <para>In this section we'll write a simple main class to run our application, and get a brief
    introduction to Cayenne ObjectContext.</para>
    <section xml:id="creating-main-class">
        <title>Creating the Main Class</title>
        <itemizedlist>
            <listitem>
                <para>In IDEA create a new class called "<code>Main</code>" in the "<code>org.example.cayenne</code>"
                    package.</para>
            </listitem>
            <listitem>
                <para>Create a standard "main" method to make it a runnable
                    class:<programlisting language="java">package org.example.cayenne;

public class Main {

    public static void main(String[] args) {

    }
}</programlisting></para>
            </listitem>
            <listitem>
                <para>The first thing you need to be able to access the database is to create a
                    <code>ServerRuntime</code> object (which is essentially a wrapper around Cayenne stack) and
                    use it to obtain an instance of an
                    <code>ObjectContext</code>.<programlisting language="java">package org.example.cayenne;

import org.apache.cayenne.ObjectContext;
import org.apache.cayenne.configuration.server.ServerRuntime;

public class Main {

    public static void main(String[] args) {
        ServerRuntime cayenneRuntime = new ServerRuntime(
                "cayenne-project.xml");
        ObjectContext context = cayenneRuntime.newContext();
    }
}</programlisting></para>
                <para><code>ObjectContext</code> is an isolated "session" in Cayenne that provides all needed API
                    to work with data. ObjectContext has methods to execute queries and manage
                    persistent objects. We'll discuss them in the following sections. When the first
                    ObjectContext is created in the application, Cayenne loads XML mapping files and
                    creates a shared access stack that is later reused by other ObjectContexts.
                </para>
            </listitem>
        </itemizedlist>
    </section>
    <section xml:id="runnning-app">
        <title>Running Application</title>
        <para>Let's check what happens when you run the application. But before we do that we need
            to add another dependency to the <code>pom.xml</code> - Apache Derby, our embedded database engine.
            The following piece of XML needs to be added to the
            <code>&lt;dependencies&gt;...&lt;/dependencies&gt;</code> section, where we already have Cayenne
            jars:<programlisting language="xml">&lt;dependency&gt;
   &lt;groupId&gt;org.apache.derby&lt;/groupId&gt;
   &lt;artifactId&gt;derby&lt;/artifactId&gt;
   &lt;version&gt;10.13.1.1&lt;/version&gt;
&lt;/dependency&gt;</programlisting>Now
            we are ready to run. Right click the "Main" class in IDEA and select "Run 'Main.main()'".
        </para>
        <para>
            <inlinemediaobject>
                <imageobject>
                    <imagedata fileref="images/idea-file-run-menu.png"/>
                </imageobject>
            </inlinemediaobject>
        </para>
        <para>
            In the console you'll see output similar to this, indicating that Cayenne stack has been started:
            <screen>INFO: Loading XML configuration resource from file:/.../cayenne-project.xml
INFO: Loading XML DataMap resource from file:/.../datamap.map.xml
INFO: loading user name and password.
INFO: Connecting to 'jdbc:derby:memory:testdb;create=true' as 'null'
INFO: +++ Connecting: SUCCESS.
INFO: setting DataNode 'datanode' as default, used by all unlinked DataMaps</screen>
            
            <note>
                <title>How to Configure Cayenne Logging</title>
                <para>Follow the instructions in the logging chapter to tweak verbosity of the logging output.</para>
            </note>
           </para>
    </section>
</section>