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<h2>Extension Points</h2>

<p>We call these extensions so they are not confusd with plugins.  Webpieces has specific extension points
to help you create a seamless development experience and speed up your development.</p>

<p>Webpieces leverages <a href="https://github.com/google/guice/wiki/Multibindings">Guice's amazing Multibinders</a>.
Webpieces creates empty Multibinders in <a href="https://github.com/deanhiller/webpieces/blob/master/webserver/http-router/src/main/java/org/webpieces/router/impl/EmptyPluginModule.java">EmptyPluginModule.java</a>.
You can see the 4 plugin points that other modules can add to the multibinder are:</p>

<ol>
    <li><a href="https://github.com/deanhiller/webpieces/blob/master/webserver/http-router/src/main/java/org/webpieces/router/api/Startable.java">Startable.java</a></li>
    <li><a href="https://github.com/deanhiller/webpieces/blob/master/webserver/http-router/src/main/java/org/webpieces/router/api/EntityLookup.java">EntityLookup.java</a></li>
    <li><a href="https://github.com/deanhiller/webpieces/blob/master/webserver/http-router/src/main/java/org/webpieces/router/api/BodyContentBinder.java">BodyContentBinder.java</a></li>
    <li><a href="https://github.com/deanhiller/webpieces/blob/master/webserver/http-router/src/main/java/org/webpieces/router/api/ObjectStringConverter.java">ObjectStringConverter.java</a></li>
</ol>

<p>We will break down what each of these for so you can leverage these to make life easier in many cases</p>

<h3>Startable.java</h3>

<p>As an example, in <a href="https://github.com/deanhiller/webpiecesexample-all/blob/master/webpiecesexample/src/main/java/org/webpieces/base/GuiceModule.java">GuiceModule.java</a>
in the template, you will see that we already wired in a plugin class PopulateDatabase so there is some data.  Also of note is that this is 
a 'production' module so you may want to move it to a DevelopmentServer module instead.  This is however debatable as you 'could' do a database
check and if there a is data do nothing and if there is no data, run it all so you could easily start up an integration database more easily
every time.  It's up to you.</p>

<p>All Startable classes are called before loading routes currently.  All Startable classes can also be injected with any of your
application classes using Guice as well so it's easy to inject hibernate EntityManagerFactory and such for saving data to a 
database</p>

<h3>EntityLookup.java</h3>

<p>This is for hibernate or other object mapping layers.  When a controller is about to be invoked and takes a bean, we know the
Class of that bean and we ask all plugins if they are managing that bean.  If they are, we then proceed to invoke the find method
to either lookup the entity from the database or create a brand new empty one so we can fill it in from the form that was
just posted.  This is very specific to bean mapping layers so generally you will not need to implement this.</p>

<h3>BodyContentBinder.java</h3>

<p>This is great for implementing any protocol you want.  It will marshal the body into a bean or a bean into a html body.  One
example is the <a href="https://github.com/deanhiller/webpieces/blob/master/webserver-plugins/plugin-json-jackson/src/main/java/org/webpieces/plugin/json/JacksonLookup.java">JacksonLookup.java</a>
for the jackson plugin.  You just have to implement isManaged to tell us if this is the plugin managing that bean or not
and the bytes to bean and bean to bytes and we do the rest.</p>

<p>If you ever need a new protocol over webpieces, this is the man, google protobuf, thrift or whatever protocol you want</p>

<h3>ObjectStringConverter.java</h3>

<p>Now for some juicy very useful stuff.  As seen in 
<a href="https://github.com/deanhiller/webpiecesexample-all/blob/master/webpiecesexample/src/main/java/org/webpieces/base/GuiceModule.java">GuiceModule.java</a>,
we add to ObjectStringConverters, one is EducationEnum.WebConverter.class and another is RoleEnum.WebConverter.class.  When we have forms, we need 
to convert objects or enums to strings to display them AND when the form is posted, we need to convert Strings to objects or enums.  
ObjectStringConverter allows you to add in conversions from joda.util.Time to string and back all so things are converted for you by the time
they reach your controller</p>

<p>One example is you may have an Account object in a controller method like postAccount(Account account) and inside that account,
there is a EducationEnum field and a DateTime field.  Well, with the ObjectStringConverter, we will convert that stuff for you
and then pass in a ready to use Account object</p>