Posted by Jakub Holý on January 31, 2013
- Dustin Marx: Significant Software Development Developments of 2012 – Groovy 2.0 with static typing, rise of Git[Hub], NoSQL, mobile development (iOS etc.), Scala and Typesafe stack 2.0, big data, HTML5, security (Java issues etc.), cloud, DevOps.
- 20 Kick-ass programming quotes – including Bill Gates’ “Measuring programming progress by lines of code is like measuring aircraft building progress by weight.”, B.W. Kernighan’s “Debugging is twice as hard as writing the code in the first place. Therefore, if you write the code as cleverly as possible, you are, by definition, not smart enough to debug it.”, Martin Golding’s “Always code as if the guy who ends up maintaining your code will be a violent psychopath who knows where you live.” (my favorite)
- How to Have a Year that Matters (via @gbrindusa) – do you want to just survive and collect possessions or do you want to make a difference? Some questions everybody should pose to him/herself.
- Expression Language Injection – security defect in applications using JSP EL that can sometimes leads to double evaluation of the expressions and thus makes it possible to execute data supplied by the user in request parameters etc. as expressions, affects e.g. unpatched Spring 2.x and 3.
- HN discussion about Scala 2.10 – compilation speed and whether it matters, comparison of the speed and type system with Haskell and OCaml, problems with incremental compilation (dependency cycles, fragile base class), some speed up tips such as factoring out subprojects, the pros and cons of implicits etc.
- Blog Mechanical Sympathy – interesting posts and performance tests regarding “writing software which works in harmony with the underlying hardware to gain great performance” such as Memory Access Patterns Are Important and Compact Off-Heap Structures/Tuples In Java.
- Neal Ford: Functional thinking: Why functional programming is on the rise – Why you should care about functional programming, even if you don’t plan to change languages any time soon – N. Ford explains the advantages of FP and why FP concepts are spreading into other languages (higher abstractions enabling focus on the results over steps and ceding control to the language, more reusability on a finer level (higher-order functions etc.), few generic data structures with many operations -> better composability, “new” and different tool such as lazy collections, shaping the language towards the problem instead of vice versa, aligning with trends such as immutability)
- Neal Ford: Java.next: The Java.next languages Leveraging Groovy, Scala, and Clojure in an increasingly polyglot world – a comparison of these languages with focus on what they are [not] suitable for, exploration of their paradigms (static vs. dynamic typing, imperative vs. functional)
- How to Completely Fail at BDD – a story of an enthusiastic developer who tried to make everyone’s life better by introducing automated BDD tests and failed due to differences in culture (and inability to change thinking from the traditional testing), a surprising lack of interest in the tool and learning how to write good tests: “Culturally, my current team just isn’t ready or interested in something like this.” Morale: It is hard to change people, good ideas are not enough.
- M. Feathers: Refactoring is Sloppy – refactoring is often prioritized out of regular development and refactoring sprints/stories aren’t popular due to past failures etc. An counter-intuitive way to get refactoring in is to imagine, during planning, what the code would need to be like to make it easy to implement a story. Then create a task for making it so before the story itself and assign it to somebody else then the story (to force a degree of scrutiny and communication). “Like anything else in process, this is medicine. It’s not meant to be ‘the way that people do things for all time’ [..]” – i.e. intended for use when you can’t fit refactoring in otherwise. It may also make the cost of the current bad code more visible. Read also the commits (f.ex. the mikado method case).
- Cyber-dojo: A great way to practice TDD together. Compare your read-green cycle and development over time with other teams. Purposefully minimalistic editor, a number of prepared tdd tasks.
- On the Dark Side of “Craftsmanship” – an interesting and provoking article. Some developers, the software labouers, want to get work done and go home, they haven’t the motivation and energy to continualy spend time improving themselves. There is nothing wrong with that and we shouldn’t disparge them because of that. We shouldn’t divide people into craftsmen and the bad ones. A summary of and response to the varied reactions follows up in More on “Craftsmanship”. The author is right that we can’t expect everybody to spend nights improving her/his programming skills. Still they should not produce code of poor quality (with few exceptions) since maintaining such code costs a lot. There should be time for enough quality in a 9-5 day and people should be provided with enough guidance and education to be able to write decent code. (Though I’m not sure how feasible it is, how much effort it takes to become an acceptable developer.) Does the increased cost of writing (an learning to write) good code overweight the cost of working with bad code? That is an eternal discussion.
Cloud, web, big data etc.
- Whom the Gods Would Destroy, They First Give Real-time Analytics (via Leon) – a very reasonable argument against real-time analytics: yes, we want real-time operational metrics but “analytics” only makes sense on a sensible amount of data (for the sake of statistical significance etc.) RT analytics could easily provide misguided results.
CAP Twelve Years Later: How the “Rules” Have Changed (tl;dr, via @_dagi) – an in-depth discussion of the CAP theorem and the simplification (2 out of 3) that it makes; there are many more nuances. By Eric Brewer, a professor of computer science at the University of California, Berkeley, and vice president of infrastructure at Google.
- ROCA: Resource-oriented Client Architecture – “A collection of simple recommendations for decent Web application frontends.” Server-side: true REST, no session state, working back/refresh etc. Client: semantic HTML independent of layout, progressive enhancement (usable with older browsers), usable without JS (all logic on the server) etc. Certainly not suitable for all types of apps but worthwile to consider the principles and compare them with your needs.
- Vaurien, the Chaos TCP Proxy (via @bsvingen) – an extensible proxy that you can control from your tests to simulate network failure or problems such as delays on 20% of the requests; great for testing how an application behaves when facing failures or difficulties with its dependencies. It supports the protocols tcp, http, redis, memcache.
- Wvanbergen’s request-log-analyzer for Apache, MySQL, PostgreSQL, Rails and more (via Zarko) – generates a performance report from a supported access log to point out requests that might need optimizing
- Working Effectively With iTerm2 (Mac) – good tips in the body and comments
A very good (though not very scientific) definition of project success applicable for distinguishing truly agile from process-driven projects:
[..] a project is successful if:
- Something was delivered and put to use
- The project members, sponsors and users are basically happy with the outcome of the project
- Johannes Brodwall in “How do we become Agile?” and why it doesn’t matter, inspired by Alistair Cockburn
(Notice there isn’t a single word about being “on time and budget”.)
Posted in General, Java, Testing, Tools, Top links of month | Tagged: bigdata, clojure, cloud, fun, life, performance, SbE, scala, security, tdd, Testing | Leave a Comment »
Posted by Jakub Holý on June 21, 2012
JBoss AS 7 is neat but the documentation is still quite lacking (and error messages not as useful as they could be). This post summarizes how you can create your own JavaEE-compliant login module for authenticating users of your webapp deployed on JBoss AS. A working elementary username-password module provided.
Read the rest of this entry »
Posted in j2ee, Java, Tools | Tagged: jboss, security, webapp | Leave a Comment »
Posted by Jakub Holý on November 30, 2011
- Recommended Reading by Poppendiecks – an excellent selection, starting with Lean from Trenches, Management 3.0, Specification by Example, The Lean Startup etc.
- Eric Allman says that Programming Isn’t Fun Any More because problem solving has been replaced with learning, configuring, and integrating tons of libraries, frameworks, and tools and many people agree with that (as discussion on reddit proves). In other words we tend to go for any benefit we can have without considering the costs and for “easy” solutions without considering the true enemy: complexity. Perhaps we should always listen to the Rich Hickey’s Simple Made Easy talk before we add a lib/tool/framework?
- Dean Wampler claims that functional programming can bring the joy back – “[..] a functional language, Scala, Clojure, Haskell, etc. will greatly reduce the amount of code you create. That won’t solve the problem of trying to integrate with too many libraries, but you’ll be less tempted. I also believe those libraries will be less bulky, etc.“
- Few quotes from a related article by M. Taylor: To put it another way, libraries make excellent servants, but terrible masters. | [..] frameworks [..] do keep their promise of making things very quick and easy … so long as you do things in exactly the way the framework author intended | On libraries: [..] we all assume (I know I do) that “plug in solutions X1 and X3″ is going to be trivial. But it never is — it’s a tedious exercise in impedance-matching, requiring lots of time spent grubbing around in poorly-written manuals [..] | On the effect of language choice: [..] different languages, with their different expressive power and especially their different culture, yield very different experiences.
- To sum it up: Choose your tools and libraries wisely and always mind the global complexity. More usually means worse.
- Java Magazine – Adam Bien: Stress Testing Java EE 6 Applications (page 41+) – do developer stress testing! Using: JMeter, VisualVM to find out resource consumption and behavior in the application, VisualVM’s Sampler profiling tool [cca 20% overhead], a webapp to extract metrics from GF (STM)
- Java Magazine – Polyglot Programming on the JVM (page 50; excerpt from The Well-Grounded Java Developer) – why you should consider polyglot programming and how to decide whether to use it and what languages to pick, f.ex.: “These [Java's] qualities make the language a great choice for implementing functionality in the stable layer [of the polyglot programming pyramid]. However, these same attributes become a burden in the middle and upper [lower, DSL, on the linked image] tiers of the pyramid; for example: Recompilation is laborious; Static typing can be inflexible and lead to long refactoring times; Deployment is a heavyweight process; Java’s syntax is not a natural fit for producing DSLs.” “There is a wide range of natural use cases for *alternative languages*. [after identifying such a UC] You *now need to evaluate* whether using an alternative language is appropriate.”
- Intrusion Detection for Web Apps – Detection Points – If security is a concern of your web application then you should build intrusion detection into the application f.ex. leveraging the OWASP AppSensor project. The key is to detect malicious/unexpected behavior and proactively do something such as locking the user out or alerting the admins. The page linked above lists some common suspicious behaviors such as the use of multiple usernames, unexpected HTTP command/method, additional/duplicated data in request. Worth checking out!
- Yammer Moving From Scala to Java- Scala is a cool language but sometimes its cost is higher than the benefits. Snippets from the post: “…the friction and complexity that
comes with using Scala instead of Java isn’t offset by enough productivity benefit or reduction of maintenance burden …”. “Scala, as a language, has some profoundly interesting ideas in it. [...] But it’s also a very complex language. The number of concepts I had to explain to new members of our team for even the simplest usage of a collection was surprising: implicit parameters, builder typeclasses, ‘operator overloading’, return type inference, etc. etc.” (It’s claimed that only library authors need to know some of that but if it’s a part of library APIs, the users need to understand it too.) Notice that the author isn’t saying “Scala is bad” but only that Scala isn’t the best balance of their needs at this time, as Alex Miller put it*
: The text wasn’t intended for publication and it is a private opinion of a Yammer developer, not the company itself. You should read the official Yammer’s position
where Coda puts it into the right context.
- Opportunistic Refactoring by Martin Fowler – refactor on the go – how & why
- Michael Feathers: Getting Empirical about Refactoring – gather information that helps us understand the impact of our refactoring decisions using data from a SCM, namely File Churn (frequency of changes, i.e. commits) vs. Complexity – files with both high really need refactoring. Summary: “If we refactor as we make changes to our code, we end up working in progressively better code. Sometimes, however, it’s nice to take a high-level view of a code base so that we can discover where the dragons are. I’ve been finding that this churn-vs.-complexity view helps me find good refactoring candidates and also gives me a good snapshot view of the design, commit, and refactoring styles of a team.“
UIs and Web Frameworks
- Devoxx 2011 - WWW: World Wide Wait? A Performance Comparison of Java Web Frameworks (slides) – the authors did extensive performance testing of some of the most popular web frameworks. Of course it’s always hard to guess how general their results are, if/how they apply to one’s particular situation, and if they aren’t distorted in some way but it’s worth for their approach alone (AWS with its CloudWatch monitoring, WebDriver, additional measurement of page load with HAR and a browser plugin). In their particular tests GWT scored best, followed by Spring MVC, with JSF and Wicket lagging far behind (especially the MyFaces implementation). Conclusion: A web framework may have strong impact on performance and scalability, if they are important for you then do test the performance early with as realistic code and load as possible.
- JSF2 – Benchmark datatable by N. Labrot, 2/2011 – performance comparison of PrimeFaces 2.2.1, IceFaces 2.0, Richfaces 4.0.0M4 on a simple page with Ajax. I do not trust any benchmark that I don’t fake myself (for there are always too many factors that influence the conclusions to be drawn) but it’s interesting anyway – and perhaps a good thing to do before you decide for a JSF component library.
- Alex MacCaw: Asynchronous UIs – the future of web user interfaces and the Spine framework – users in 2011 shouldn’t anymore wait for pages to load and operations to complete, we should build asynchronous UIs where changes to the UI are performed immediately while a request to the server is sent in the background, similarly to sending e-mail in GMail, which returns at once displaying a non-intrusive “Sending…” notification. As a user I very much agree with Alex.
- Matt Raible’s 20 criteria for evaluating web frameworks, 2010 (detailed description, here’s a brief list) – Matt’s results are disputable and as he himself says you should always do your own evaluation and spikes but the criteria are pretty useful: Developer Productivity, Developer Perception, Learning Curve, Project Health, Developer Availability, Job Trends, Templating, Components, Ajax, Plugins or Add-Ons, Scalability, Testing, i18n and l10n, Validation, Multi-language Support (Groovy / Scala), Quality of Documentation/Tutorials, Books Published, REST Support (client and server), Mobile / iPhone Support, Degree of Risk.
Don’t use MongoDB via @nicolaiarocci – a (fake?!) bad experience with MongoDB – the text is not credible (the author is anonymous, s/he doesn’t explicitely state which version of MongoDB they used, the 10gen CTO can’t find a matching client and any evidence for some of the issues mentioned) but it gives context for the read-worthy response from the 10gen CTO, and a post that nicely explains how to correctly design for MongoDB. A comment about MongoDB experience at Forsquare: “Currently we have dozens of MongoDB instances across several different data clusters storing over a TB of data and handling 10s of thousands of requests per second (mostly reads but the write load is reasonably high as well).Have we run into problems with MongoDB along the way? Yes, of course we have. It is a new technology and problems happen.Have they been problematic enough to seriously threaten our data? No they have not.“
- Martin Fowler on Polyglot Persistence – the are when will be choosing persistence solution with respect to our needs instead of mindlessly picking RDBMS is coming. Applications will combine multiple, specific solutions, f.ex. we could pick Redis (key-value) for caching, MongoDB (document DB) for product catalog, Neo4J (graph DB) for recommendations, RDBMS for financial data and reporting… (of course not all in one project!). Polyglot persistence will come at a cost (complexity, learning) – but it will come because the benefits are worth it – performance, data storage model and behavior more aligned with the business logic (NoSql databases ofer various models and tradeoffs and thus we can find a much better fit than with general-purpose RDBMs).
Talks & Video
- Adam Bien’s JavaOne talk Java EE 6: The Cool Parts (1h) – absolutely worth the time – a very practical fly through the cool features of Java EE (eventing, ..), most of the time is spent actually coding. Don’t forget to check also the interesting discussion below the video (JEE and other frameworks, Java FX and JSF 2, …).
- Jurgen Appelo’s keynote How to Change the World at Smidig 2011 is well done and highly useful. We all strive to change the world around us – as consultants we want to make our clients more agile, as team members we want to make our Scrum teams more self-organizing, as employees we want to help building knowledge-sharing and open culture, … . However it isn’t easy to influence or change people and culture and if we aren’t aware of all the dimensions of a change (system, individuals, interactions, environment) and how to work along each of them, we are much less likely to succeed. The knowledge and experience that Jurgen shares with us can help us a lot in having an impact. You can also download the slides and change management questions.
- Project X: What is being a programmer like? (5min) If ever again a non-geek asks you what you as a developer are doing, just show him this short and extremely funny video (created by my ex-employer – perhaps they estimated how much time and energy developers loose trying to explain it to normal people and decided to prevent this great waste )
- RSA Animate – Drive: The surprising truth about what motivates us (10 min) – entertaining and enlightening; once we’ve enough money to cover our needs, it’s autonomy (self-direction), mastery, and purpose what motivates us (money actually decrease our performance). Now this is a great evidence for lean/agile – for they’re based on making people self-directing and encourage mastery (as in continous integration and top quality to enable steady pace). Autonomy enables engagement as does a higher purpose (“make the world a better place”) – Steve Jobs with his visions was able to provide such a purpose. Atlassian’s FedEx Days are a good example of what engagement and benefits autonomy brings.
- Simon Sinek: How great leaders inspire action (18 min, subtitles in 37 languages) – do you want to succeed, to change the world around you for the better, to start a new company? Then you must start by communicating “why” you do what you do, not “what” – like M. L. King, bro Wrights, and Apple. Very inspiring! (More in his Why book.)
Links to Keep
Refactoring is like advertising: it doesn’t cost, it pays.
- Mary & Tom Poppendiecks, Implementing Lean Software Development, p.166
Posted by Jakub Holý on October 21, 2010
If you would like to get the security certificate used by a server in communication over SSL, such as with the HTTPS or POP3s protocols, for instance to install it on a client device that needs to talk to the server, you can use OpenSSL to retrieve it:
bash$ openssl s_client -connect pop.gmail.com:995 -showcerts
You then store the text starting with “—–BEGIN CERTIFICATE—–” and ending with “—–END CERTIFICATE—–” (inclusive) into a file with the extension .pem.
You can also use openssl to convert the certificate into another format, e.g.:
bash$ openssl x509 -in mycertificate.pem -inform PEM -out mycertificate.der -outform DER
The information originates from the page Gmail POP3 with Fetchmail where you can find a more detailed description and also instructions for testing the certificate.
Posted in General | Tagged: certificate, security, SSL | Leave a Comment »
Posted by Jakub Holý on September 10, 2010
This post describes how to configure the jetty-maven-plugin and the Jetty servlet container to run a web application that uses a data source and requires users to log in, which are the basic requirements of most web applications. I use Jetty in development because it’s fast and easy to work with. Read the rest of this entry »
Posted in j2ee, Java, Tools | Tagged: datasource, development, java, javaEE, jetty, Maven, security | Leave a Comment »
Posted by Jakub Holý on November 24, 2006
Recently I started a new J2EE project that required j2ee security. Unfortunately Rational app. Developer 6 seemed to have some problems running a WAS Test Environment in this way, at least with the default setup. I encountered 2 problems:
- RAD wasn’t able to connect to the server at all, throwing some security exceptions.
The solution (or rather work-around) was to switch the “Server connection type..” in the server’s configuration in RAD from RMI to SOAP. It seems that RMI doesn§t support authetification.
- After that, everything seemed to be ok, but an error was logged every few seconds with the cause “No received or invocation credential exist on the thread“. The stack trace pointed to a MBean (a part of JMX) being contacted via RMI.
Work-around: Disable an RMIConnector for JMX in WAS Console: log in, go to
Application servers > server1 > Administration > Administration Services > JMX connectors
And delete the RMIConnector – make first sure that you don’t need it.
BTW, to enable the security, I enabled it first on the server via WAS admin console and then I created a new server configuration in RAD and set it to use security.
Stack trace for issue 2:
com.ibm.ws.security.role.RoleBasedAuthorizerImpl.checkAccess(RoleBasedAuthorizerImpl.java(Compiled Code)) at com.ibm.ws.management.AdminServiceImpl.preInvoke(AdminServiceImpl.java:1696) at com.ibm.ws.management.AdminServiceImpl.preInvoke(AdminServiceImpl.java:1603) at com.ibm.ws.management.AdminServiceImpl.preInvoke(AdminServiceImpl.java:1533) at com.ibm.ws.management.AdminServiceImpl.preInvoke(AdminServiceImpl.java:1506) at com.ibm.ws.management.AdminServiceImpl.getAttribute(AdminServiceImpl.java:501) at com.ibm.ws.management.connector.AdminServiceDelegator.getAttribute(AdminServiceDelegator.java:99) at com.ibm.ws.management.connector.rmi.RMIConnectorService.getAttribute(RMIConnectorService.java:123) at com.ibm.ws.management.connector.rmi._RMIConnectorService_Tie.getAttribute(_RMIConnectorService_Tie.java:193) at com.ibm.ws.management.connector.rmi._RMIConnectorService_Tie._invoke(_RMIConnectorService_Tie.java:87) at com.ibm.CORBA.iiop.ServerDelegate.dispatchInvokeHandler(ServerDelegate.java:608) at com.ibm.CORBA.iiop.ServerDelegate.dispatch(ServerDelegate.java:461) at com.ibm.rmi.iiop.ORB.process(ORB.java:432) at com.ibm.CORBA.iiop.ORB.process(ORB.java:1728) at com.ibm.rmi.iiop.Connection.doWork(Connection.java:2229) at com.ibm.rmi.iiop.WorkUnitImpl.doWork(WorkUnitImpl.java:65) at com.ibm.ejs.oa.pool.PooledThread.run(ThreadPool.java:95) at com.ibm.ws.util.ThreadPool$Worker.run(ThreadPool.java(Compiled Code)) .
Posted in eclipse, WebSphere | Tagged: development, IDE, javaEE, security, WebSphere | Leave a Comment »