Java 7：在ServletContextListener中实现线程安全的可修改静态对象的最佳方法？

Question

In a Java 7 Tomcat application, an object/structure obj containing several simple (String and numeric) types is frequently shared (read) by multiple servlet threads. Periodically (every n minutes), all of obj 's members need to be refreshed simultaneously and atomically with respect to each other, and each of the servlet threads must always get the updated values whenever it reads the object. If no clients are connected, there is no need to refresh the values; but as soon as one does connect (assuming at least n minutes have passed since the last update), the update needs to happen before the object is read. Update: I should mention that currently, one of obj 's members is a timestamp indicating when the object data expires and needs to be refreshed. If a solution, such as Guava Cache suggested in a comment below, already has this functionality built in, then all the better.

How would you implement this in Java 7? At this point, simplicity and 'cleanliness' are more important than performance, but if you also want to provide a solution that's optimized for performance, please do. I have an idea that may or may not work the way I expect, but would like to hear other opinions first. Thanks in advance.

Answer 1

Use Guava Cache.

In the context listener, do something like this:

LoadingCache<String, List<YourObjectType>> myCache = CacheBuilder.newBuilder()
    .expireAfterWrite(60, TimeUnit.MINUTES)
    .build(new CacheLoader<String, List<YourObjecttype>>() {
        public List<YourObjectType> load(String arg) {
            ...
        }
});

Save it to your servlet context:

ServletContext servletContext = servletContextEvent.getServletContext();
servletContext.setAttribute("myCache", myCache);

Then use it anywhere by getting the "myCache" attribute from the context object.