JavaChannel’s Interesting Links podcast, episode 13

Welcome to the thirteenth ##java podcast. It’s Tuesday, January 30, 2018. Your hosts are Joseph Ottinger (dreamreal on IRC) and Andrew Lombardi (kinabalu on IRC) from Mystic Coders. We have a guest this podcast: Cedric Beust, who’s always been very active in the Java ecosystem, being a factor in Android and author of TestNG as well as JCommander and other tools – and it’s fair to say that if you’ve used modern technology, Cedric’s actually had something to do with it. Really.
As always, this podcast is basically interesting content pulled from various sources, and funneled through the ##java IRC channel on freenode. You can find the show notes at the channel’s website, at javachannel.org; you can find all of the podcasts using the tag (or even “category”) “podcast”, and each podcast is tagged with its own identifier, too, so you can find this one by searching for the tag “podcast-13”.
A topic of discussion from ##java last week centers on code coverage: what numbers are “good”? What numbers can be expected? What’s a good metric to consider? Joseph likes (apparently) absurdly high numbers, like 90% or higher; Cedric recommends 50% code coverage as a good baseline; Andrew targets 70%. Expect a poll in the channel on this! It’s a really good discussion, but it’s not really going to be summarized here; listen to the podcast!

  1. Grizzly – an HTTP server library based on NIO – has been donated to EE4J. That’s not particularly interesting in and of itself, but there’s a question of whether all the projects being donated to EE4J imply an abandonment of Java EE as a container stack. It may not be; after all, EE4J is an umbrella just like Java EE itself is, so this may be very much what we should expect – which makes pointing it out as news rather odd. (The original item was from Reddit.)

  2. Pivotal gave us a really interesting article, called “Understanding When to use RabbitMQ or Apache Kafka.” Kafka and RabbitMQ are both sort of message-oriented, but there’s a lot of confusion about when you’d use one against the other; this article discusses both RabbitMQ’s and Kafka’s strengths and weaknesses. It would have been nicer to talk about AMQP as opposed to RabbitMQ, but the article works nonetheless. Kafka is a high-performance message streaming library; it’s not transactional in the traditional sense; it’s incredibly fast. AMQP is slower (but still really fast, make no mistake) and provides traditional pub/sub and point to point messaging models. The main point of the article, though, is that if you need something other than a traditional model, Kafka is there… but it’s going to involve some effort.

  3. Gradle 4.5 has been released. It’s supposedly faster than it was, and has improvements for C/C++ programmers. It also has better documentation among other changes; Gradle’s good, and this release is important, but it’s not earth-shattering. This discussion veered off quickly and sharply to Cedric’s homegrown build tool, kobalt – and mentioned Eclipse’ Aether library, since migrated to Apache under the maven-resolver project.

  4. More Java 9 shenanigans: Java EE modules – including CORBA, specifically – aren’t part of the unnamed module in Java 9. This comes to us courtesy of InfoQ, which pointed out CORBA specifically – CORBA being harder to reach isn’t really a big deal, I’d think, because nobody’s intentionally dealt with it who hasn’t absolutely had to. And it’s not really a Java EE module, really, so pointing out the removal along with Java EE is accurate but misleading. What does this mean? Well, if you’re using one of the nine modules removed, you’re likely to have to include flags at compilation and runtime to make these modules visible for your app. (See http://openjdk.java.net/jeps/320 for the actual Java Enhancement Proposal.)

  5. There’s a Java Enhancement Proposal for multiline strings. It’s in draft, but has Brian Goetz’ support; this is one of those features that Java doesn’t have that’s left people wondering why for a long time, I think – every other JVM language seems to include it. This doesn’t come up very often – if it was actually all that critical it would have been done a long time ago – but it’ll be nice to see it when (and if) it does make it into Java. It’s done with backticks; it does not use interpolation. Interesting, though.

  6. Baeldung has an article called “The Trie Data Structure in Java,” which, well, presents a Trie. It’s a good article, and explains the data structure really well – but doesn’t explain why you’d use a Trie as opposed to some other similar data structures. Tries represent a tradeoff between data size and speed; Tries tend to be incredibly fast while being more memory-hungry than some of their counterparts. Incidentally: there’s a question of pronunciation! “Trie” is typically pronounced the same was as “tree” is – while Joe pronounces it like “try” and struggled mightily to concede to peer pressure and say “tree.” Naturally, he was inconsistent about it; early pronunciation was in fact like “try” but, as stated, convention says “tree.” And it is a tree structure…

  7. Simon Levermann, sonOfRa on the channel, published a reference to his new pwhash project, a result of a series of discussions that seem to have gone on for a few weeks on the channel. It’s a password hashing library; it provides a unified interface to a set of hashing algorithms, like argon2 and bcrypt.

JavaChannel’s Interesting Links podcast, episode 12

Welcome to the twelfth ##java podcast. Your hosts are Joseph Ottinger, dreamreal on the IRC channel, and Andrew Lombardi (kinabalu on IRC) from Mystic Coders. It’s Tuesday, January 23, 2018.
As always, this podcast is basically interesting content pulled from various sources, and funneled through the ##java IRC channel on freenode. You can find the show notes at the channel’s website, at javachannel.org; you can find all of the podcasts using the tag (or even “category”) “podcast”, and each podcast is tagged with its own identifier, too, so you can find this one by searching for the tag “podcast-12”.
Not an “interesting link,” but we discuss data formats – JSON, XML, HOCON, YAML, Avro, protobuff, Thrift…

  1. Java 9.0.4 has been released, as part of the scheduled January update. NOTE: This is the final planned release for JDK 9. This is scary; see also Azul’s post, “Java: Stable, Secure and Free. Choose Two out of Three,” which points out that with Java’s new rapid-release schedule, you’re going to have to be out of date, insecure, or financially on the hook to … someone to keep up with security releases. We’ve been wanting new features in Java for a long time; we’ve been wanting more churn in the JVM, too. Looks like we, as an ecosystem, might get to experience what Scala goes through every few months, except at least we have the option of stability somewhere.

  2. Speaking of Scala, we have “10 reasons to Learn Scala Programming Language.” It actually has some decent points to make… but makes them with Scala. That’s dumb. There’s nothing that Scala really offers you that Kotlin doesn’t, and that’s assuming Java 8 and Java 9’s improvements don’t turn your crank themselves. It’s almost got a point with Spark and Kafka (well, it mentions Spark, Play, and Akka, and I’m going to pretend that the author meant to say “Kafka” instead), but… when that’s your real lever for learning a language, it’s time to admit that the language was a mistake.

  3. DZone: “Java 8: Oogway’s Advice on Optional” is yet another attempt to justify Optional in Java. It has a fair point to make: “Optional is not a replacement for the null check. Rather, it tries to tell the caller about the nature of the returned value and implicitly reminds the caller to handle the absent cases.” But … okay. So what? In the end, you still have to write what is effectively pretty simple code, and adding the semantic turns out in practice to mostly add noise to your code without actually making it any better.

  4. DZone: “An Introduction to Hollow Jars”, which I found fascinating but I don’t know why. A “hollow jar” is apparently a deployment mechanism where you have two deployable components: the main one, the “hollow jar” basically has the other component – which is the actual application code – in its classpath, and serves to invoke the entry point of the application. The invoker would theoretically change very rarely, and therefore could be baked into a docker image or some other base image, and the component that changes more often would be soft-loaded at runtime.

JavaChannel's Interesting Links podcast, episode 11

Welcome to the eleventh ##java podcast. I’m Joseph Ottinger, dreamreal on the IRC channel, and it’s Tuesday, 2018 January 16. Andrew Lombardi (kinabalu on IRC) from Mystic Coders is also on the podcast, and this episode has a special guest, Kirk Pepperdine from Kodewerk.
As always, this podcast is basically interesting content pulled from various sources, and funneled through the ##java IRC channel on freenode. You can find the show notes at the channel’s website, at javachannel.org; you can find all of the podcasts using the tag (or even “category”) “podcast”, and each podcast is tagged with its own identifier, too, so you can find this one by searching for the tag “podcast-11”.
This podcast has a lot to say about Meltdown, courtesy of Kirk – who’s a performance expert and one of the people you go to when you really need to figure out what your Java application is doing. The short version is this: Meltdown and Spectre are going to affect everything, due to the way modern CPUs work (listen to the podcast to figure out why – it’s fascinating!) – and Java’s reputation as the environment where you can code and let the JVM magically fix everything for you may be in danger. Intel may have revived the importance of data structures for the JVM singlehandedly – not a bad thing, necessarily, but something Java programmers might have to get used to again.
Kirk also went into the things that make Java 9 worth using – and it’s not modules. It’s the extended APIs and the packaging support, neither of which get mentioned very much because of all the chatter about modules.
The interesting links for this week:

  1. DZone has been putting out a lot of information regarding Java 9’s modules. Up first is “Java 9 Modules Introduction (Part 1)“, which does a pretty good job of walking through Java 9 modules from the basics on up. It’s all command-line based, so no IDE, no Maven, no Gradle – Part 2 promises integration with tooling. But knowing what the tools do is important, so this article is a good introduction, about as good as any other so far.

  2. Another entry from DZone on Java 9 is “Java 9 Module Services”, which could be written to be more clear – it refers to a source repository instead of showing lots of relevant code – but does walk through the old ServiceLoader stuff and then walks through the same mechanism in Java 9.

  3. Speaking of tooling: Baeldung has done a walkthrough of docker-java-api, providingi a guide to a Java client that interfaces with the Docker daemon, providing programmatic management of images, volumes, and networks.

  4. There’s also resilience4j, a fault-tolerance library inspired by Netflix Hystrix.It provides features for limited retries, transaction management, a number of other such things; I haven’t run into a situation where I’ve needed this (transaction management has been enough, generally) but it looks like it might be useful; maybe I’ve made architectural decisions that allow me to avoid using libraries like this because I didn’t want to write the features myself. Maybe if I’d known about this, my choices would be different… hard to say.

  5. Lastly, there’s little-java-functions, a collection of functions that look pretty useful, although not modular at all. This library covers a lot of ground. The lack of modularity probably works against it; since we’ve mentioned Java 9 so much, it’d be nice if it mentioned Java 9 compatibility with modules, but maybe Java isn’t prepared to go that far down the Scala rabbit-hole yet. In the process of recording this, a potential problem with licenses came up – possibly the subject of a future conversation – and the author ended up explicitly licensing the code under Creative Commons, thanks to Andrew.

Javachannel’s Interesting Links podcast, episode 10

Welcome to the tenth ##java podcast. If we were Neanderthals, our lives would be half over by now. As usual, I think, I’m Joseph Ottinger, dreamreal on the IRC channel, and it’s Tuesday, 2018 January 9. Andrew Lombardi, kinabalu on IRC from Mystic Coders is with me again.
As always, this podcast is basically interesting content pulled from various sources, and funneled through the ##java IRC channel on freenode. You can find the show notes at the channel’s website, at javachannel.org; you can find all of the podcasts using the tag (or even “category”) “podcast”, and each podcast is tagged with its own identifier, too, so you can find this one by searching for the tag “podcast-10”. The podcast can also be found on iTunes and I’m trying to figure out if it’d be worth it to put it on Youtube, too – sorry, folks, no video from me. I can’t afford the cameras; every time they take a picture of me, they shatter.
You can submit to the podcast, too, by using the channel bot; ~submit, followed by an interesting url, along with maybe a comment that shows us what you think is interesting about the url. Yes, you have to have a url; this is not necessarily entirely sourced material, but we definitely prefer sourced material over random thoughts.

  1. TechTarget finally gets into the podcast, with Four ways the container ecosystem will evolve in 2018. Kubernetes gets the nod of approval, and… imagine containers being used in IoT. I’m not quite sure how the latter point will work. Is docker communicating with an embedded device, or are they talking about embedded devices RUNNING docker? If so, that’d be challenging. After all, Java’s not been all that successful on constrained devices either, and it has a constrained version. (The other two ways are: increased WIndows adoption in containers, and LinuxKit – derived from the Windows thing.)

  2. Meltdown and Spectre – scary words indeed, and deservedly so. Our benefactors at Intel, whose sponsorship we’d accept mostly because we’re cheap and will take money from ANYONE, have blessed us with horrible security in virtually every chip manufactured in the last decade or so. Meltdown allows a program to access the memory of other programs and the host OS; Spectre also breaks isolation between programs. Fixing this requires replacing your physical CPU or patching your OS; the patches have performance implications. If you’re not patched, start looking for patches today. The JVM is not a good vector for delivering either of these flaws, although yawkat’s been playing around with trying it out; this is not the same as the JVM protecting you from other programs exploiting these flaws. Again, thanks, Intel.

  3. Riccardo Cardin wrote up “Single-Responsibility Principle Done Right on DZone. He’s addressing one of the SOLID principles from Robert Martin, the “Single Responsibility” principle, which states: “A class should have only one reason to change.” Mr. Cardin understandably says that that’s a qualitative assertion and not a quantitative assertion – and he suggests adding cohesion to the definition, so that “only one reason” means that it has a single purpose – be it serving as a rectangle, or interacting with a database, or what-have-you. That’s still qualitative, really, but it’s a good baseline – a data access object should ONLY interact with a database, not perform calculations on the individual objects (although I guess you could bend the definitions to make THAT work, too, in the case of reporting.)

  4. Lorenzo Sciandra wrote up “I thought I understood Open Source – I was wrong,” a well-written post about the open source mindset. He says that he used to see open source as a customer getting a freebie: the maintainers have a product that they give freely to the world. But that’s wrong: open source is all about participation. As soon as you use an open source product, you yourself are an actual owner, even if you’re passive about it; it’s yours, not theirs, and you have a right (and to a degree a responsibility) to participate and contribute to that product. It’s yours. You bit it, you bought it… which means if you find a problem, it’s your responsibility to report and address it.

  5. DZone offered us “A Log Message is Executable Code and Comment”. Basically, the author – Dustin Marx – suggests that using a logger for comments actually is a lot more useful than simple code comments; code comments are easy to ignore (even if your IDE highlights them, you get used to seeing the green or blue marker and just skip over them). But a logger event – especially if the log levels are high enough to not hide, like error or severe levels – isn’t something you can ignore. The danger here, of course, is that your comments can actually affect your runtime; interpolation takes time, so you may end up having guards around your comments, a concept I’m struggling with. But it’s a neat idea – if the logger uses a lambda instead of an interpolated value (the lambda can do the interpolation, after all) the logger can do its own guarding and the performance impact MIGHT be minimal.

  6. Up next: JaVers compared to Envers. This is a comparison between JaVers and Envers. Both are auditing tools for databases, but they have very different mindsets; Envers stores in an “audit” table that shows the history of the data with an additional version number, while JaVers stores a JSON representation of the object. The article’s pretty well-done – and uses Groovy to show functionality. Who knew – people use Groovy for something outside of Gradle? Crazy. Given that the article was written by the author of JaVers, I can’t say it was completely unbiased. It looks like a decent write-up of both tools, and seems like a fairly useful tool if you it’s a requirement for you. Have you needed to use any data auditing tools like this before?

  7. Jiccup is a library inspired by Clojure’s “hiccup” – oddly reminiscent of ECS. It reminds one more of the Jade templating engine over in NodeJS land. You don’t see this thing done much outside of JavaScript libraries (well, except for hiccup, maybe?), so it’s good to see it but it’s really weak compared to what they’ve done with something like Jade. I’m looking forward to seeing if this gets more interest, as it looks like a fairly young project. (ECS is a dead project from Jakarta; each HTML element was represented as an object type, so you’d have an HTML object to which you’d add a head object and a body object, and your body would have a list of paragraph objects… so you’re just building an object model of an HTML page. It was slaughtered, and badly and quickly, by templating.)

  8. Switch Expressions coming to Java?” mentions a Java enhancement to make switch an expression instead of a statement. I’m all for this, but why limit it to switch? Why not try or if? This is one of those features that made me love Scala – before I realized what a puddle of hacks Scala was in the real world – and makes me enjoy Kotlin today. It’d be interesting to see how this works out – there are semantics that need defining, especially in light of backward compatibility – but I love this idea.