<title>Exception Handling for Async Requests</title>

<title>Configuration for Async Request Processing</title>

<section xml:id="mvc-ann-async-configuration-servlet3">

<title>Servlet 3 Async Config</title>

<para>To use Servlet 3 async request processing, you need to update

<filename>web.xml</filename> to version 3.0:</para>

<programlisting language="xml">&lt;web-app xmlns="http://java.sun.com/xml/ns/javaee"

xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"

xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"

version="3.0"&gt;

...

&lt;web-app&gt;

</programlisting>

<para>The <classname>DispatcherServlet</classname> and any

<interfacename>Filter</interfacename> configuration need to have

the <code>&lt;async-supported&gt;true&lt;/async-supported&gt;</code> sub-element.

Additionally, any <interfacename>Filter</interfacename> that also needs

to get involved in async dispatches should also be configured

to support the ASYNC dispatcher type. Note that it is safe

to enable the ASYNC dispatcher type for all filters provided with

the Spring Framework since they will not get involved in async

dispatches unless needed.</para>

<para>If using Servlet 3, Java based configuration, e.g. via

<interfacename>WebApplicationInitializer</interfacename>, you'll

also need to set the "asyncSupported" flag as well as the

ASYNC dispatcher type just like with <filename>web.xml</filename>.

To simplify all this configuration, consider

extending <classname>AbstractDispatcherServletInitializer</classname>

or <classname>AbstractAnnotationConfigDispatcherServletInitializer</classname>,

which automatically set those options and make it very easy to register

<interfacename>Filter</interfacename> instances.</para>

</section>

<section xml:id="mvc-ann-async-configuration-spring-mvc">

<title>Spring MVC Async Config</title>

<para>The MVC Java config and the MVC namespace both provide options for

configuring async request processing.

<interfacename>WebMvcConfigurer</interfacename> has the method

<code>configureAsyncSupport</code> while &lt;mvc:annotation-driven&gt;

has an &lt;async-support&gt; sub-element.</para>

<para>Those allow you to configure the default timeout value to use for

async requests, which if not set depends on the underlying Servlet

container (e.g. 10 seconds on Tomcat). You can also configure an

<interfacename>AsyncTaskExecutor</interfacename> to use for executing

<interfacename>Callable</interfacename> instances returned from

controller methods. It is highly recommended to configure this property

since by default Spring MVC uses

<classname>SimpleAsyncTaskExecutor</classname>. The MVC Java config

and the MVC namespace also allow you to register

<interfacename>CallableProcessingInterceptor</interfacename> and

<interfacename>DeferredResultProcessingInterceptor</interfacename>

instances.</para>

<para>If you need to override the default timeout value for a

specific <classname>DeferredResult</classname>, you can do so by using

the appropriate class constructor. Similarly, for a

<interfacename>Callable</interfacename>, you can wrap it in a

<classname>WebAsyncTask</classname> and use the appropriate class

constructor to customize the timeout value. The class constructor of

<classname>WebAsyncTask</classname> also allows providing

an <interfacename>AsyncTaskExecutor</interfacename>.</para>

</section>

</section>

to be registered explicitly if they can be discovered via