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<!DOCTYPE html>

<head>

<title>Ebean ORM Setup</title>

<!--[if lt IE 9]>

<![endif]-->

</head>

<body>

<span class="sr-only">Toggle navigation</span>

</button>

<a class="navbar-brand" href="/"><img src="/images/logo-black-3.png" width="32" style="display: inline;">Ebean ORM</a>

</div>

<li ><a href="/videos">Videos</a></li>

<li ><a href="/quickstart">Quick Start</a></li>

<li ><a href="/support">Support</a></li>

<li ><a target="_blank" href="/apidoc/10">ApiDocs</a></li>

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</ul> </div>

<li ><a href="/videos">Videos</a></li>

<li ><a href="/quickstart">Quick Start</a></li>

<li ><a href="/support">Support</a></li>

<li ><a target="_blank" href="/apidoc/10">ApiDocs</a></li>

<li ><a href="/releases">Releases</a></li>

<li ><a target="_blank" href="https://github.com/ebean-orm/ebean"> <i class="fa fa-github"></i> Github</a></li>

</ul> </div>

</div>

<h1><a href="/docs">Documentation</a> / <a href="/docs/setup">Setup</a> / Active record </h1>

</div>

<h2 id="overview">Overview</h2>

<p>

Active record is a pattern originally named by

<a href="https://en.wikipedia.org/wiki/Active_record_pattern">Martin Fowler</a> and is not specific to Ebean but

instead a a pattern common in many persistence frameworks.

</p>

<p>

In general terms it means the entity beans have the capability to <code>save()</code> and <code>delete()</code>

by themselves. You can contrast this to a traditional <code>DAO</code> approach where the entity beans are

instead passed to a DAO for saving and deleting.

</p>

<h4>Play framework</h4>

<p>

For Ebean the active record pattern has been inherited from the Play framework. The original Model and Finder implementations

found in Ebean to implement the active record pattern originated from Play framework and that code has migrated over into Ebean.

</p>

<h2 id="criticism">Criticism</h2>

<p>

The two main criticisms to the active record pattern are:

</p>

<ul>

<li><b>Combining concerns</b> - The 'model' and 'how it is persisted' are tightly combined</li>

<li><b>Testability</b> - Active record is in theory harder to test</li>

</ul>

<p>

It should be noted that Ebean provides a testing mechanism via <code>ebean-mocker</code> such

that the active record patterns for both saving and finding are fully testable.

</p>

<h2 id="jpa">Rob's view: JPA and active record</h2>

<p>

My opinion is that JPA is not well suited to the active record pattern. This is based on my personal experience

with Grails/GORM/Hibernate. Specifically, GORM is effectively hiding the existence of Hibernate Session

from the developer. My experience suggests that this works well with simple cases but in more complex case developers

find a situation where they need to know about and deal with the Session/EntityManager object explicitly.

</p>

<p>

The save() delete() semantics of active record don't match the underlying attach/detach/flush semantics of JPA and in the

more complex cases that mismatch comes out (abstraction leaks). This typically results in a change to both

coding style and thinking and a code base containing both styles.

</p>

<h2 id="ebean">Rob's view: Ebean and active record</h2>

<p>

EbeanServer is a "session-less" ORM and specifically unlike JPA there are no attach/detach semantics.

This makes Ebean well suited to the active record pattern as there is no mismatch between the

active record API/abstraction and that of the underlying EbeanServer.

</p>

<p>

The complex persistence cases with Ebean means you want/need full control over JDBC batch mechanism.

In these more complex cases the active record save() and delete() still work as expected and desired but

instead you additionally adjust JDBC batch control via the transaction (programmatically or via @Transactional).

That is, there is no need to change style in complex cases.

</p>

<h2 id="testing">Testing</h2>

<p>

Ebean provides the <code>ebean-mocker</code> project and that supports the testing requirements

when using active record pattern. It supports using test doubles for EbeanServer in both persisting and

finding and provides DelegateEbeanServer as a good out of the box test double for persisting and finding.

</p>

<h3>DelegateEbeanServer provides</h3>

<ul>

<li>Capture persisting calls, assert saved beans etc</li>

<li>findById stub/mock responses</li>

<li>static Finder stub/mock test doubles</li>

<li>SQL capture</li>

</ul>

<h2 id="benefits">Rob's view: Active record benefits</h2>

<p>

For some people active record combines concerns and that ends the conversation and that is fine.

</p>

<h4>Not missing out on testability</h4>

<p>

Personally when I compare what I call the traditional DAO/Inject approach with active record

I note firstly that I don't lose out on testability - Active record with Ebean can be just as

testable as the DAO/Inject style.

</p>

<h4>Simple things kept simple</h4>

<p>

Secondly the major plus to active record is that "simple things" are kept simple. What I mean

by that is save(), delete(), get reference, find by id and find by unique key are all very

simple and very clean in code. In DAO/Inject code what I have seen is that for each type of

entity bean you inject a DAO - for a service that deals with 4 different entity bean types you

then end up injecting 4 DAOs. For constructor injection in particular injecting DAO's can lead

to relatively ugly constructors and 'workarounds' very quickly.

</p>

<blockquote>With active record, the simple things are kept simple</blockquote>

<h4>In balance I'd choose active record</h4>

<p>

If someone asks me whether to choose between active record style or traditional DAO/Inject style

I would suggest the active record style due to the very nice clean simple code that results.

We don't miss out on testability (due to ebean-mocker) and I'm ok that the entity beans

have save() delete() methods (mixed concerns).

</p>

<h2 id="model">Model</h2>

<p>

When your entity beans extend the

<a href="https://github.com/ebean-orm/ebean/blob/master/src/main/java/io/ebean/Model.java"><code>io.ebean.Model</code></a> object they

inherit some convenience methods save(), delete() etc. When these methods are called internally

the default EbeanServer is used to perform the save() and delete().

</p>

<p>

Ebean Model provides the following convenience methods:

</p>

<ul>

<li>save() - Saves the entity</li>

<li>update() - Explicitly update the entity</li>

<li>insert() - Explicitly insert the entity</li>

<li>delete() - Delete the entity</li>

<li>refresh() - Refreshes the entity from the database</li>

<li>markAsDirty() - this is used so that when a bean that is otherwise unmodified is updated the version property is updated</li>

<li>update(String server) - Update the entity using the specified Ebean server</li>

<li>insert(String server)- Insert the entity using the specified server</li>

<li>delete(String server)- Delete the entity using the specified server</li>

</ul>

<h4>Example: extend Model</h4>

<span class="cm"> * Extend Model to get the save(), delete() etc</span>

<span class="cm"> * methods on the bean itself (active record style).</span>

<span class="nd">@Entity</span>

<span class="nd">@Table</span><span class="o">(</span><span class="n">name</span><span class="o">=</span><span class="s">"o_customer"</span><span class="o">)</span>

<span class="kd">public</span> <span class="kd">class</span> <span class="nc">Customer</span> <span class="kd">extends</span> <span class="n">Model</span> <span class="o">{</span>

<span class="n">String</span> <span class="n">name</span><span class="o">;</span>

<span class="n">Date</span> <span class="n">registered</span><span class="o">;</span>

<span class="n">String</span> <span class="n">comments</span><span class="o">;</span>

</pre></div>

</div>

<h4>Example: save()</h4>

<span class="n">customer</span><span class="o">.</span><span class="na">setName</span><span class="o">(</span><span class="s">"Rob"</span><span class="o">);</span>

<span class="n">customer</span><span class="o">.</span><span class="na">save</span><span class="o">();</span>

</pre></div>

</div>

<h2 id="finder">Finder</h2>

<p>

Finder provides some convenience query methods but also it suggests a way to

organise 'finder' code.

</p>

<p>

</p>

<h4>Example: find by id</h4>

<div class="syntax java"><div class="highlight"><pre><span></span><span class="n">Customer</span> <span class="n">customer</span> <span class="o">=</span> <span class="n">Customer</span><span class="o">.</span><span class="na field">find</span><span class="o">.</span><span class="na">byId</span><span class="o">(</span><span class="mi">42</span><span class="o">);</span>

</pre></div>

</div>

<h4>Example: get reference</h4>

<div class="syntax java"><div class="highlight"><pre><span></span><span class="n">Customer</span> <span class="n">customer</span> <span class="o">=</span> <span class="n">Customer</span><span class="o">.</span><span class="na field">find</span><span class="o">.</span><span class="na">ref</span><span class="o">(</span><span class="mi">42</span><span class="o">);</span>

</pre></div>

</div>

<h4>Example: delete by id</h4>

<div class="syntax java"><div class="highlight"><pre><span></span><span class="n">Customer</span><span class="o">.</span><span class="na field">find</span><span class="o">.</span><span class="na">deleteById</span><span class="o">(</span><span class="mi">42</span><span class="o">);</span>

</pre></div>

</div>

<h4>Example: find where</h4>

<div class="syntax java"><div class="highlight"><pre><span></span><span class="n">List</span><span class="o"><</span><span class="n">Customer</span><span class="o">></span> <span class="n">customers</span> <span class="o">=</span>

<span class="n">Customer</span><span class="o">.</span><span class="na">find</span>

<span class="o">.</span><span class="na">where</span><span class="o">().</span><span class="na">ilike</span><span class="o">(</span><span class="s">"name"</span><span class="o">,</span> <span class="s">"rob%"</span><span class="o">)</span>

<span class="o">.</span><span class="na">findList</span><span class="o">();</span>

</pre></div>

</div>

<li >

<a href="/docs/setup/enhancement">Enhancement</a>

</li>

<li >

<a href="/docs/setup/eclipse-apt">Eclipse IDE - APT</a>

</li>

<li >

<a href="/docs/setup/logging">Logging</a>

</li>

<li >

<a href="/docs/setup/serverconfig">ServerConfig</a>

</li>

<li >

<a href="/docs/setup/guice">Guice</a>

</li>

<li >

<a href="/docs/setup/spring">Spring</a>

</li>

<a href="/docs/setup/activerecord">Active Record</a>

<li><a href="#overview">Overview</a></li>

<li><a href="#criticism">Criticism</a></li>

<li><a href="#jpa">JPA and active record</a></li>

<li><a href="#ebean">Ebean and active record</a></li>

<li><a href="#testing">Testing</a></li>

<li><a href="#benefits">Benefits</a></li>

<li><a href="#model">Model</a></li>

<li><a href="#finder">Finder</a></li>

</ul>

</li>

<li >

<a href="/docs/setup/ddl-create-all">DDL - Create All</a>

</li>

<li >

<a href="/docs/setup/dbmigration">DDL - DB Migration</a>

</li>

<li >

<a href="/docs/setup/test-properties"> Test properties</a>

</li>

<li >

<a href="/docs/setup/testing">Testing</a>

</li>

</ul>

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