As Jacques mentioned, OFBiz is a bit special in Apache. Why special? Personally, I think OFBiz is built for Sharan, for consultants. The other projects in Apache are for developers.
So my vote will follow Sharan's. :) -----邮件原件----- 发件人: Adrian Crum [mailto:adrian.c...@sandglass-software.com] 发送时间: 2015年10月15日 3:21 收件人: dev@ofbiz.apache.org 主题: Why A Framework Rewrite Is Necessary I understand that Sharan brought up the framework rewrite subject at ApacheCon, and some attendees felt that the framework is fine and no action needs to be taken. In this message, I will try to give a detailed explanation of why a framework rewrite is necessary. I don't plan to take any further action on this subject, because I've brought it up before without success, and I'm tired of discussing it. It is my hope that the light bulb will click on in someone's head and they will take action. My Background ------------- I became a member of the OFBiz community in 2004. I immediately started making contributions to the project by supplying patches to the issue tracker. In 2007, I became a committer. Most of my initial work was on the UI and some work in the applications (mainly Asset Maintenance and Work Effort). I stayed away from touching the framework code because it was deep, dark, and scary. Eventually, I started to understand how the framework code works and I made some minor modifications. As my understanding grew, I progressed to rewriting large swaths of framework code - making it thread-safe, fault tolerant, efficient, and easier to use. I will list some of my contributions here, so everyone can have a clear understanding of my experience with the framework code: New Features User Preferences Visual Themes Custom UI Label XML File Format Temporal Expressions Data Type Conversion Framework Screen Widget Boundary Comments Metrics Integrations UEL iCalendar JSR 223 WebDAV LDAP Refactorings/Improvements FlexibleStringExpander FlexibleMapExpander FOP Integration FreeMarkerWorker Date-Time Handling Mini-language Job Scheduler In addition, I have performed innumerable framework bug fixes. So, the contents of this message come from years of experience mucking about in the framework code. Okay, let's get started... Initial Problem Statement ------------------------- In 2009, David Jones started a framework rewrite in a branch: https://svn.apache.org/repos/asf/ofbiz/branches/executioncontext20090716 At the time, there was some agreement that a rewrite was necessary, but there was disagreement as to how the rewrite should be incorporated into the project: https://mail-archives.apache.org/mod_mbox/ofbiz-dev/200908.mbox/%3c455601.62605...@web63102.mail.re1.yahoo.com%3E There were concerns that a rewrite would break backward compatibility. Work on the rewrite branch stopped. Eventually, Jacopo suggested the community be more accepting of backward-incompatible changes: https://mail-archives.apache.org/mod_mbox/ofbiz-dev/201004.mbox/%3cd24f129d-4f9f-444e-84af-aca46f499...@hotwaxmedia.com%3e Despite an effort to convince David to proceed with the framework rewrite, he ended up doing it in a separate project: http://mail-archives.apache.org/mod_mbox/ofbiz-dev/201104.mbox/%3c07565c88-4023-4d24-93a3-a4906e86f...@me.com%3E This page describes differences between OFBiz and Moqui, and within it you can extract information on the problems David was trying to solve: http://sourceforge.net/p/moqui/discussion/1086127/thread/4c52f240/ There was an email he sent out on the OFBiz dev list where he listed the problems he saw in the framework, but I can't find it. The rest of this message will include the issues he mentioned (the ones I remember). I was in agreement with him at the time, and I still agree that a framework rewrite is necessary. The Problems ------------ Code is scattered everywhere - due to an initial effort to make the framework modular. This causes serious problems. The mere fact that components like entityext and securityext EXIST makes it clear that there are problems - those components should not be there. Also, we run into the recurring problem of circular dependencies (component A will not build unless component B is built, and component B will not build unless component A is built). Bad separation of concerns. There are far too many examples of classes that try to be everything to everyone. This makes debugging difficult, and it makes maintenance/improvements a nightmare. [Using an analogy, consider an automobile design where a spark plug is not separate from a transmission. Instead, the automobile uses a spark-plug-transmission. So when the engine is running rough because the spark plug is bad, you have to replace the spark plug AND the transmission.] A good framework example can be found in my rewrite of the mini-language code. Originally, the models AND the script execution context both contained script behaviors - making debugging/improvements difficult. I changed it so only the models contain script behavior and the script execution context contains only the script execution state. Lack of good OO design. There are many places where a bit of framework functionality is contained in a single method that is hundreds or thousands of lines long. There is a term for that: Brittle Code. Code isn't reused. Instead, it is copy-and-pasted all over - so when a problem is found in the C&P code, it has to be fixed in many places instead of one. Fail-slow design. There are a lot of places in low-level code where an error condition is encountered, but instead of throwing an exception, the error is ignored and maybe it is logged, or the code tries to "guess" at a solution and then provide an arbitrary default behavior. I've seen many developers struggle with debugging a problem because they didn't look at the logs, or because the error was not logged and there is no way of knowing what caused it. They end up spending hours single-stepping through code until it reaches the error. Out-of-date code. A good example is the use of Javolution. That library was beneficial in the Java 1.4 days, but it is not necessary today because of improved garbage collection. Another good example is DCL code. DCL was used extensively in OFBiz, but it is clearly documented to be an unreliable design (I can get it to fail 90% of the time). Some DCL code has been replaced, but a lot of it is still there. Portions of the API are overly complicated. Some methods require a collection of user-specified artifacts/arguments, which makes client code complicated and verbose. (David solved that problem with his Execution Context.) Portions of the API are cluttered with unnecessary "convenience methods" - making the API harder to learn and memorize. In some places, a domain-specific API is spread across instance methods and static methods and across different classes - making the API hard to understand and use. Yes, there can be good designs that require something like that, but in the OFBiz framework, it exists because of a bad design, not a good one. Use of thread-local variables. This makes multi-threaded design impossible. The J2EE specification and the Servlet API require one thread per request (and most J2EE libraries depend on that behavior), so the current design makes sense from a J2EE perspective, but what if I don't want to run the framework in a J2EE container? Which leads to the next problem... Dependence on J2EE designs/APIs/libraries. There are developers in the Java community (myself included) who are beginning to question if J2EE is really necessary to run web applications. The folks at Atomikos are a good example. OFBiz does not use EJBs, so tying the framework to J2EE does not make sense. It would be better if the framework was designed to run outside a J2EE container, and then have container integration as an option. Configuration files are scattered everywhere. Anyone who has deployed OFBiz in a production environment will agree this is a problem. Try changing the HTTP/HTTPS and port settings - it is a nightmare. Some configuration settings are in nonsensical places. An abysmal lack of unit testing. I don't have an exact figure for code coverage, but my gut feeling is coverage is less than 10%. Basically, we all have our fingers crossed - hoping that the framework code works as expected. This was made painfully obvious a while back when I was looking at some entity caching code and thought to myself "this code can't work." So I wrote some entity cache unit tests and confirmed that the entity cache had serious problems. Think about that - years passed with no entity cache unit tests and consequently we had no idea it wasn't working. Fix Versus Rewrite ------------------ Jira issues could be created for these problems and teams of developers could work to fix them. Or, we could create a branch and start over from scratch. This time around, there should be less push-back from people concerned about backwards compatibility. A rewrite offers the advantage of reconsidering everything - like API design, general problem solving, and new features. I created a Wiki page for a framework design: https://cwiki.apache.org/confluence/display/OFBADMIN/Another+Framework+Vision but there hasn't been much interest in it. If the community decides to go ahead with a rewrite, then please feel free to use the Wiki pages as a guide. Sandglass Foundation -------------------- Like David, I came to the conclusion that a framework rewrite would be easier outside the OFBiz community. So, I created my own library called Foundation: http://www.sandglass-software.com/products/sandglass/documents/Foundation_Brochure.pdf (PDF) and I only mention it here to stress how wonderful it can be to start with a clean slate and design an API that is concise yet powerful. (Please do not discuss Foundation here, contact me privately if you want more information.) Some examples of what can be done with a rewrite: A single configuration file Use ANSI/ISO SQL SELECT statement strings instead of constructing complicated Java structures Simultaneous asynchronous queries Relational integrity across multiple datasources Multi-table SELECT across multiple datasources Automatic and transparent row version control Automatic and transparent multi-language datasource support Abstract entities (similar to SQL user types) Service engine throttling (protects against server over-utilization) Simplified security (authorization) (https://cwiki.apache.org/confluence/display/OFBIZ/OFBiz+Security+Redesign) Pure interface-based API - so developers are free to modify framework behavior by using decorators Thorough unit tests Benefits of a rewrite: Reduced resource requirements (lower hosting fees) Reduce application development time - due to a simplified API Easier framework code maintenance Better reliability Conclusion ---------- Like I said at the start, this is all I will say about the subject. I'm done trying to convince everyone. I hope someone agrees with me and they are able to build support for the idea. -- Adrian Crum Sandglass Software www.sandglass-software.com
