Java is slow, but not in this case. Tight loop java is fast. Anything that touches memory is slow. Anything that involves loading jar files is slow. Anything that involves starting the VM is slow. But tight loop java is fast, indeed, being a JIT, potentially faster than C (better branch prediction given that the JIT can optimize at runtime).
So the claim that Java is slow is true. That's why so many people hate it. The fact that Java is fast is also true.
To be more fair, java is mostly slow on startup which which is mostly due to:
1) Swing. I have no idea what this does on startup but it is bad. This is what killed most java GUI apps. A simple AWT or SWT app will pop open while a simple swing app will take a few seconds to get started
2) Jars on systems with virus scanners. Jars are just zip files. Many virus scanners will unzip and scan a zip on every open which leads to each jar being unziped at least 2 times and often more if the app has to load more things from the jar at a later time.
3) Spring. Really spring is just a bad idea all the way through and most of the reason people hate java is Spring. Huge XML configuration files instead of code? Spring (mostly annotations now). Stupid names like AbstractSingletonProxyFactoryBean? Spring. That aside, on startup Spring will auto generate classes which really slows things down. This could have been done during the last build but spring does it at each startup which is really slow. Spring Boot has helped with startup times but it is still slower.
After startup Spring continues to kill performance. The underling code is full of maps to control request lifecycle so instead of just calling a method it has to ask "who all is configured to do something at step PreParseRequestEncoding?" then again at ParseRequestEncoding, PostParseRequestEncoding, PrePareRequestBody, ParseRequestBody.... Not real names but the idea and number of steps is. Most of the time the answer is "nobody" but it has to ask for every step that might ever need something done.
Add on top of this JPA which is super easy but quickly breaks down to a lot of DB calls. JPA is great for people who don't want to learn SQL and simple CRUD apps but anything with any amount of data will quickly slow down to thousands of DB round trips.
I like Spring, I find it makes Java development pleasant, plus I have unfair access to the Spring team members by working for the same company. So I'll bite.
> Huge XML configuration files instead of code? Spring (mostly annotations now).
Spring 3, yes. Spring 4 and 5, no. XML has not been the blessed configuration approach for ~4 years.
> Stupid names like AbstractSingletonProxyFactoryBean? Spring.
Java is a language that has evolved enormously in expressiveness since Spring began, meaning heavyweight Go4 patterns were necessary early on to maintain a flexible substrate with a uniform interface serving very many use cases? Spring.
> That aside, on startup Spring will auto generate classes which really slows things down.
I believed this urban legend too.
Dave Syer, who is understandably interested in Spring criticism, has done more empirical investigation than anyone on this topic[0].
The tl;dr is that boot time is proportional to total classes loaded. That's all, that's it.
In-memory reflection operations are hilariously, stupidly, insanely faster than I/O. The JVM fetches and loads classes individually. So if you have a lot of classes, it takes a longer time to load.
The other thing to bear in mind is that Spring relies on this much less than it used to. As the language and JVM have evolved, so has Spring.
> The underling code is full of maps to control request lifecycle ... Not real names but the idea and number of steps is.
Are you talking about servlet filters? Because any web framework is going to have a few of these. Spring MVC adds a handful and all of them can be removed, replaced or added to. Spring Security adds a bunch and all of them can be removed, replaced or added to. But the defaults are chosen because of feedback, not just for the heck of it.
> Add on top of this JPA which is super easy but quickly breaks down to a lot of DB calls. JPA is great for people who don't want to learn SQL and simple CRUD apps but anything with any amount of data will quickly slow down to thousands of DB round trips.
In general, yes, I agree that JPA is a PITA. For a small to medium system I would try to avoid it where possible. For a sufficiently large codebase -- thousands of domain objects, dozens or hundreds of programmers -- it might be a necessary evil.
Mind you, if you want to see a world where the database goes from abused to outright mocked and ignored, pay a visit to Rails land. It drives me batty.
I will admit that spring has gotten a lot better recently, but it is still a mess (IMHO of course) and this "benchmark" seems to agree.
The biggest issue I have with spring isn't performance but is the huge internal state that is the basis of Spring's DI.
After a few versions you end up with code that depends on bean named 'Abd" to preform a task, but in the next version is renamed to "Abc" which fixes the typo, but makes all the documentation off. And the 3 other classes that also needed that task still look for it under the name "Abd". And then the next major version replaces this entire module and the bean name is now "Xyz". To me this IS spring programming. Googling the DI names and trying them one by until you get the desired run time functionality.
I've had apps in production with unused beans defined (It only had 1 function that only throw an exception and was never called) but had to be defined or something would break. Multiple team members wasted some free time trying to locate the code that was requiring that bean but nobody could ever figure it out. At some point everybody gave up, it was easier to just let it be.
Most developers have little to no idea what is actually going on inside their spring apps (or even what half their dependencies are). When a struts like vulnerability comes along in the spring world it is going to be a massive PITA to fix. With how complex this all is I have little doubt that a vulnerability exist somewhere in there.
The Struts vulnerability was less about Struts and more about the universal difficulty of dependency management.
Which Spring Boot ameliorates by providing starter POMs. Curated, levelled, updated collections of dependencies for common cases. No need to play whack-a-dep with Maven or Gradle. No need to track 50 different dependencies yourself.
The thing is: I don't care how Spring does the magic. I care that I don't have to care.
I came to Spring and Java-for-real development relatively late -- by fluke I was on what is almost certainly the first Boot production app ever deployed, back in early 2014.
Later I got a chance to see the primordial world of Spring 3. I understand the residual hate.
> Are you talking about servlet filters? Because any web framework is going to have a few of these. Spring MVC adds a handful and all of them can be removed, replaced or added to. Spring Security adds a bunch and all of them can be removed, replaced or added to. But the defaults are chosen because of feedback, not just for the heck of it.
Even ignoring filters, it seems to me that Spring brings a lot of overhead. Adding an annotation to a method sometimes means that would appear to be a direct call between two of your beans is in fact separated by 10 method calls on a stack trace. In many cases this is not an issue (expecially in "enterprise" applications), but it is clear to me that performance is not really one of the main concerns of spring developers.
> In-memory reflection operations are hilariously, stupidly, insanely faster than I/O. The JVM fetches and loads classes individually. So if you have a lot of classes, it takes a longer time to load.
One thing that I have noticed is that with all these annotation, the Java compiler is not doing much any more. Java has effectively became a dynamic language (as in an interpreted language) where errors are only visible at runtime when hitting some specific method.
Coupled with the really slow startup time (again, I talk about Spring Boot--I get a steady 10s vs 0.01s for Go, same functionality), it makes developing a simple CRUD a pain compared to both Go or Python/Ruby...
I don't even know what to say about items #1 and #2 here. Unless you work for JetBrains, is Swing relevant to anything? And virus scanners shouldn't be an issue unless you're running on a Windows server, in which case I question whether you know what you're doing.
If you really believe that JPA means "you don't have to understand SQL", then you definitely don't know what you're doing.
As for Spring, I get so tired of reading lengthy critiques that boil down to:
1. "It uses XML! (or at least it did 10 years ago, when my personal experience with it was last up-to-date)"
2. "It has some classes with long names! Named after design patterns that I don't like!"
By all means, don't use Spring if you don't want to. But know that Spring is very modular, letting you include or exclude whatever you like, and the core is rather light. If you're not using at least some of it, then you're probably re-writing it... and doing a worse job than they did. Either way, stop ranting about it on web forums if your knowledge is from 2007.
> And virus scanners shouldn't be an issue unless you're running on a Windows server, in which case I question whether you know what you're doing.
Is "the server" the only place where code is run today? That is a sad image for privacy and user sovereignty. I certainly still run a lot of code on my local system, and I wish more people did the same.
I (sadly) have production experience from within the last year. I don't use Spring by choice, but it still gets forced on me by coworkers and teammates, so I reserve the right to complain.
I've heard the "you're probably re-writing it... and doing a worse job than they did" argument so many times, is this on the spring forums or something?
Not sure about using Spring for creating Web services (most use JAX-RS), but otherwise Spring is great. Not sure what we would do without it. The two major aspects are the dependency injection and just sheer number of service libraries to do anything imaginable.
I generally try to stay away from strong opinions and assume that when something has an opinion there may be a reason behind it, but in the case of Spring and Java, I have concluded that those not using or familiar with Spring are simply clueless jokers.
Java is slow compared to C/C++ and Fortran and comparable with SBCL / Rust. But it is fast compared to Python, JavaScript, PHP and Ruby.
It's the rise of these languages that confuses me.
They somehow got away with the 'fast enough' argument whilst Java is constantly being compared to languages that are designed for fine tuning for the target architecture.
In my mind it is Java that is 'fast enough' and,with Java 8, very expressive. The continued success of these incredibly slow interpreted languages in enterprises where you need to buy servers feels like an anti-pattern.
From my perspective, choosing Python over Java (on Linux) around 2001:
It was easy to find benchmarks showing that Java was fast. But Java turned out to be slower in every situation we might consider using it.
Command-line applications were slower because the JVM took ages to start.
GUI applications were slower, apparently because Python would use C-implemented widgets while Java would do much of the drawing itself.
Web applications were slower without any good excuse as far as I could see, but something in the application server that was the mainstream way of doing things added more per-request overhead than starting a whole new Python interpreter via CGI.
CPU-intensive operations (I remember image resizing in particular) were slower because, again, you ended up comparing the JVM against a well-written C extension.
I think that the part this is missing is that when comparing Java to Python/Ruby part of the argument for the latter is the dynamic language aspect. To the folks making these statements, Java is seen as involving all the headaches of those faster languages but none of the advantages whereas Python/Ruby have slower runtimes but come with potentially faster development time, etc. I personally don't like this comparison but it's how I see it made typically.
Random anecdote which led me to stop calling Java slow: I'll never forget the time I took a 3000ish line Python program which had been heavily performance tuned and thus completely impenetrable. I converted it to a dumbest-scheme-possible naive implementation in Java weighing in at roughly 100 lines , expecting that to be a first pass. It turned out that the Java implementation was many times faster so we called it good enough and moved on with life. Obviously YMMV and all of that
Do multi-threaded workloads, which a lot of high performance workloads are, Java has also the potential to be faster than C++ due to garbage collection and threading aware optimizations it can make. Memory allocation, especially when memory lifecycle spans threads can be expensive in C++.
"A JVM does that???" by Cliff Click is a good introduction on what can go in the background.
I just looked at the list for where my beloved cherrypy might sit. It is almost at the bottom. But that does not matter because writing webapps with it is easy and fun.
As I see it, most sites don't need the hardware they're allocated. If you want to sleep on the weekend, you need at least two and probably three servers. That is almost certainly in the realms of 10x what most applications actually need. So a language that is 10x slower than C isn't a big deal.
CherryPy fits nicely into this window of opportunity, but as soon as you have to go back to your boss and say "I think we need a bigger boat" someone should be asking questions about library and language choices, at the very least there should be a conversation about prototypes vs production architectures.
Similarly, Python and the dynamic languages are 'fast enough' because in the 90s the bottleneck was IO, not CPU. That is still true, but is becoming less true. SSDs rapidly closed that gap, and it looks like memristor storage could mean that non-volatile RAM is as large as SSD and as fast as DRAM is today.
The dynamic language decision to focus on single threaded performance is also smart, but that will stop being true when CPU have hundreds of cores, instead of 10s. Synchronized access to cache is 100x slower than regular access. So to see benefit for work loads other than the "embarrassingly parallel" with multi-core you need around 100 threads. The new competition in the CPU market might see the first 100 core die on the market in 5 years.
The trend towards 'serverless' could be even worse for dynamic/interpreted languages. Smaller slices of billing will show that the same service written in Java vs Python cost 5-10x less. That was harder to show when you had to pay for at least two servers for every deployed service, now it will be very clear to CFOs how much language choice affects their bottom line.
What this means is that the perceived difference in performance between Java and Python can only grow over the next 5-10 years. If Java continues to gross you out, I'd be looking to pad your resume with something like Clojure / Go / Rust. High productivity, high performance languages are here and their relevance is growing.
So the claim that Java is slow is true. That's why so many people hate it. The fact that Java is fast is also true.