My advice on how to get answers to your questions is to find a good set of sites on the web (tech news sites, blogs, blog aggregators, vendor sites, etc.). Then, keep up to date by reading these sites regularly. The purpose of this is not only to keep up with the latest developments, but also to understand the history, direction, and rate of development of each technology area you're interested in.
Also, you should develop a repertoire of bookmarks to websites with reference materials for all of these technologies. Usually, all of this information (specifications, API docs, tutorials, examples, etc.) is available free on the web. The materials on the web are often kept up to date -- if it's not, that should tell you something right there. In many cases where a technology is evolving quickly, multiple versions of the documentation are available. This is important, as when a technology is moving fast, deployments will often lag by one or more releases. You might have to develop on an older release.
Now, sometimes books are good. I like to read books, and I have a lot of them. There are a bunch of reasons why reading books is nicer than reading stuff online. But books cost money, they take up space, and they're never with you when you want to look at them. Most importantly, they go out of date, at varying rates depending on the technology they cover.
Let's take 2008 as an example. If you have a book on the Java platform from 2008, it's probably still reasonably up to date right now. To know this, you have to know that there was a nearly 5-year gap between Java releases -- Java SE 6 was released in 2006 and Java SE 7 wasn't released until 2011. Presumably a book published in 2008 would cover Java SE 6. While uptake of Java 7 is healthy, many sites probably still have Java 6 in production, so the 2008 book would be pretty current. Oracle is stepping up the pace of Java platform development, though, so a 2008 book might end up going out of date fairly quickly.
You had asked about a 2008 book on JSPs and servlets. I don't know much about these areas, but I know that JSPs and servlets are part of Java EE. Java EE 6 and GlassFish v3 (the Java EE 6 reference implementation) weren't released until late 2009. Again, I'm not very familiar with these technologies, but this seems like a significant set of releases, and they wouldn't be covered by a 2008 book. While the 2008 book would be missing some significant new bits, I'd guess that it would cover some useful background and that many parts would still be relevant.
Different technologies develop and different rates. You have to keep tabs on their development by reading the web. Only after you've done this can you assess the relevance or currency of any particular book.