juneau-doc/docs/Topics/06.juneau-rest-server/03.Instantiation/08.LifecycleHooks.html

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Lifecycle Hooks

<p>
	Lifecycle hooks allow you to hook into lifecycle events of the servlet/resource creation and REST calls.
</p>
<p>
	For example, if you want to add an initialization method to your resource:
</p>
<p class='bpcode w800'>
	<ja>@Rest</ja>(...)
	<jk>public class</jk> MyResource  {

		<jc>// Our database.</jc>
		<jk>private</jk> Map&lt;Integer,Object&gt; <jf>myDatabase</jf>;

		<ja>@RestHook</ja>(<jsf>INIT</jsf>)
		<jk>public void</jk> initMyDatabase(RestContextBuilder builder) <jk>throws</jk> Exception {
			<jf>myDatabase</jf> = <jk>new</jk> LinkedHashMap&lt;&gt;();
		}
	}
</p>
<p>
	Or if you want to intercept REST calls:
</p>
<p class='bpcode w800'>
	<ja>@Rest</ja>(...)
	<jk>public class</jk> MyResource {

		<jc>// Add a request attribute to all incoming requests.</jc>
		<ja>@RestHook</ja>(<jsf>PRE_CALL</jsf>)
		<jk>public void</jk> onPreCall(RestRequest req) {
			req.setAttribute(<js>"foo"</js>, <js>"bar"</js>);
		}
	}
</p>
<p>
	The hook events can be broken down into two categories:
</p>
<ul class='spaced-list'>
	<li>Resource lifecycle events:
		<ul>
			<li class='jf'>{@link oajr.annotation.HookEvent#INIT INIT} - Right before initialization.
			<li class='jf'>{@link oajr.annotation.HookEvent#POST_INIT POST_INIT} - Right after initialization.
			<li class='jf'>{@link oajr.annotation.HookEvent#POST_INIT_CHILD_FIRST POST_INIT_CHILD_FIRST} - Right after initialization, but run child methods first.
			<li class='jf'>{@link oajr.annotation.HookEvent#DESTROY DESTROY} - Right before servlet destroy.
		</ul>
	<li>REST call lifecycle events:
		<ul>
			<li class='jf'>{@link oajr.annotation.HookEvent#START_CALL START_CALL} - At the beginning of a REST call.
			<li class='jf'>{@link oajr.annotation.HookEvent#PRE_CALL PRE_CALL} - Right before the <ja>@RestMethod</ja> method is invoked.
			<li class='jf'>{@link oajr.annotation.HookEvent#POST_CALL POST_CALL} - Right after the <ja>@RestMethod</ja> method is invoked.
			<li class='jf'>{@link oajr.annotation.HookEvent#END_CALL END_CALL} - At the end of the REST call after the response has been flushed.
		</ul>
</ul>

<ul class='seealso'>
	<li class='ja'>{@link oajr.annotation.RestHook}
</ul>