Is it safe to store data in a static field when deployed to Google App Engine?

Question

I was looking at the Vosao CMS code, an open source CMS hosted by the Google App Engine (which I find an amazing idea), and I came across the following code inside the CurrentUser class :

/**
 * Current user session value cache class. Due to GAE single-threaded nature
 * we can cache currently logged in user in static property. Which we set in 
 * authentication filter.
 */
public class CurrentUser {

        private static UserEntity user;

        public static UserEntity getInstance2() {
                return user;
        }

        public static void setInstance2(UserEntity aUser) {
                user = aUser;
        }
}

I have never used GAE, but it sounds very strange to me.

• Is GAE really single-threaded? Is it safe to store data with query scope in a static field when using GAE?

• Does this mean that for each instance of JVM will run only HTTP-request one , and all other requests are waiting for?

• GAE? , GAE UserEntity ? ThreadLocal , Spring ? - bean ( Injection Dependency)?

Answer 1

GAE ""? GAE?

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, JVM HTTP- , ?

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Answer 2

Java Python App Engine ; , , JVM HTTP-, JVM .

, - Java Servlet . ThreadLocal.