[
https://issues.apache.org/jira/browse/WW-4874?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16223520#comment-16223520
]
ASF GitHub Bot commented on WW-4874:
------------------------------------
yasserzamani opened a new pull request #179: WW-4874 Introduces Servlet3 plugin
(adds support for async methods)
URL: https://github.com/apache/struts/pull/179
> Tested with high concurrent requests using JMeter (a simple async action
which returns a json result after 40 seconds).
# Simple usage
## Action
```java
public class AsyncAction {
public Callable<String> execute() throws InterruptedException {
return new Callable<String>() {
@Override
public String call() throws Exception {
waitForEvent();
return "success";
}
});
}
private void waitForEvent() throws InterruptedException {
Thread.sleep(40000);
}
}
```
## struts.xml
```xml
<action name="async"
class="me.zamani.yasser.ww_convention.actions.AsyncAction">
<result name="success" type="json" />
</action>
```
## web.xml
```xml
<servlet>
<servlet-name>appServlet</servlet-name>
<servlet-class>org.apache.struts2.dispatcher.servlet.StrutsServlet</servlet-class>
<load-on-startup>1</load-on-startup>
<async-supported>true</async-supported>
</servlet>
<servlet-mapping>
<servlet-name>appServlet</servlet-name>
<url-pattern>/</url-pattern>
</servlet-mapping>
```
# Customize timeout
## Action
```java
public class AsyncAction {
public Callable<String> execute() throws InterruptedException {
return new
org.apache.struts2.servlet3.async.AsyncAction(60000/*timeout*/,
new Callable<String>() {
@Override
public String call() throws Exception {
waitForEvent();
return "success";
}
});
}
private void waitForEvent() throws InterruptedException {
Thread.sleep(40000);
}
}
```
# Serializing multiple async tasks ❗️ 😮
## Action
```java
public class AsyncAction {
public Callable<String> execute() throws InterruptedException {
return new Callable<String>() {
@Override
public String call() throws Exception {
waitForEvent1();
return new Callable<String>() {
@Override
public String call() throws Exception {
waitForEvent2();
return "success";
}
});
}
});
}
private void waitForEvent1() throws InterruptedException {
Thread.sleep(40000);
}
private void waitForEvent2() throws InterruptedException {
Thread.sleep(40000);
}
}
```
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> Asynchronous action method
> --------------------------
>
> Key: WW-4874
> URL: https://issues.apache.org/jira/browse/WW-4874
> Project: Struts 2
> Issue Type: New Feature
> Components: Core Actions, Dispatch Filter
> Reporter: Yasser Zamani
> Labels: action, asynchronous
> Fix For: 2.5.x
>
> Original Estimate: 1,344h
> Remaining Estimate: 1,344h
>
> User will be able to return {{java.util.concurrent.Callable<String>}} in
> their actions. Struts when sees such result, runs {{resultCode =
> result.call();}} in it's own managed thread pool but exits from servlet's
> main thread with a null result, i.e. gives back main thread to container and
> leaves response open for concurrent processing. When {{resultCode =
> result.call();}} returned, Struts calls
> {{javax.servlet.AsyncContext.dispatch()}} and {{resumes request processing}}
> within a container's thread servlet to generate the appropriate result for
> user according to {{resultCode}}.
> This adds better support for SLS (Short request processing, Long action
> execution, Short response processing) via Servlet 3's Async API.
> Support of other cases like SSL (e.g. a download server) or LLL(e.g. a video
> converter server) is still open.
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