昨天我看了一个关于Java Server Faces 2.0的演示,它看起来确实令人印象深刻,尽管我现在是一个快乐的ASP。asp.net MVC / jQuery开发。我最喜欢JSF的地方是它有大量支持ajax的UI组件,这使得开发比使用ASP要快得多。NET MVC,特别是在ajax较多的站点上。集成测试看起来也很不错。
由于这个演示只强调了JSF的优点,所以我也想听听其他方面的情况。
所以我的问题是:
Java Server Faces 2.0的主要缺点是什么?
什么会使JSF开发人员考虑使用ASP。NET MVC而不是JSF?
在使用JSF工作了5年之后,我认为我可以添加我的2分。
Two major JSF drawbacks:
Big learning curve. JSF is complex, that's just true.
Its component nature. Component-based framework tries to hide the true nature of the Web, which comes with a huge amount of complications and disasters (like not supporting GET in JSF within almost 5 years).
IMHO hiding HTTP Request/Response from the developer is an enormous mistake. From my experience, every component-based framework adds abstraction to the Web development, and that abstraction results in unnecessary overhead and higher complexity.
And minor drawbacks that come to my mind:
By default ID of the object is composed of its parents' ids, for example form1:button1.
No easy way to comment-out incorrect page's fragment. Tag <ui:remove> needs syntactically correct content which is parsed anyway.
Low quality 3rd party components which e.g. don't check isRendered() inside processXxx() method before continuing.
Incorporating LESS & Sencha is hard.
Doesn't play well with REST.
Not so easy for UX designers, because ready-to-use components have their own CSS styles, that need to be overwritten.
不要误会我的意思。作为一个组件框架,JSF在版本2中确实很好,但它仍然是基于组件的,而且永远是……
请看看Tapestry、Wicket的低人气以及有经验的JSF开发人员的低热情(这是更有意义的)。
作为对比,看看Rails、Grails、Django、Play!框架——它们都是基于动作的,不会试图向程序员隐藏真实的请求/响应和web的无状态特性。
对我来说,这是JSF的主要缺点。恕我直言,JSF可以适合某些类型的应用程序(内部网、表单密集型),但对于现实生活中的web应用程序来说,它不是一个好方法。
希望它能帮助一些人做出关于前端的选择。
Inexperienced developers usually will create applications that are painfully slow and code will be really ugly and hard to maintain. Its deceptively simple to start, but actually requires some investment in learning if you want to write good programs.
At least at the start you will often "stuck" on some problem and will spend more time reading balusc posts on internet than actually working :) After a while it will be less and less of that, but it still can be annoying.
Even more annoying when you find out that the problem is not due to you lack of knowledge/mistake but actually a bug. Mojarra was(is?) quite buggy, and another layer of components adds even more problems. Richfaces was biggest piece of crap software ever written :) Don't know how it is now on version 4. We have Primefaces which is better, but still you will run into bugs or lack of features especially with more exotic components. And now you will need to pay for Primefaces updates. So I would say its buggy but its getting better especially after 2.2 version fixed some problems with spec. Framework getting more mature but still far from perfect (maybe myfaces better?).
I don't find it especially flexible. Often if you need something very very customized and there are no components that does that - it will be a bit painful. Again I'm talking from average developer perspective - the one with deadlines, quick reading tutorials, and searching stackoverflow when getting stuck because no time to learn how it really works :) Often some components seems to have "almost" what you need, but not exactly and sometimes you might spend too much time to make it do something you want :) Need to be careful in evaluating if its better to create your own or torture existing component. Actually if you are creating something really unique I would not recommend JSF.
简而言之,我的缺点是:复杂,开发过程不流畅,漏洞百出,缺乏灵活性。
当然也有好处,但这不是你问的。不管怎样,这是我使用框架的经验,其他人可能有不同的意见,所以最好的方法是尝试一段时间,看看它是否适合你(只是一些更复杂的东西-不是天真的例子- JSF真的很出色:)依我看,JSF的最佳用例是业务应用程序,如crm等…
我们使用JSF开发了一个示例项目(这是一个为期三周的研究,所以我们可能会丢失一些东西!)
我们尝试使用核心jsf,如果需要组件,我们使用PrimeFaces。
该项目是一个带有导航功能的网站。当点击菜单时,每个页面都应该通过ajax加载。
该网站有两个用例:
带有网格的页面。网格是通过ajax加载的,应该支持排序和分页
一个三步向导页面。每个页面都有客户端验证(用于简单验证)和服务器端ajax基础验证(用于复杂验证)。任何服务器异常(来自服务层)应该显示在向导的同一页上,而不需要导航到下一页。
我们发现:
You need to use some hacks from omniFaces to make the JSF view state fixed. The JSF state will be corrupted when you include pages via ajax in each other. This seems a bug in JSF and may be fixed on next releases (not in 2.3).
The JSF Flow is not working correctly with ajax (or we could not make it work!) We try to use primeface wizard component instead but the client validation seems not supported and mean while it was not standard JSF flow standard.
When using some jQuery components like jqGird, and you need to load JSON results, then you are advised to use pure servlet, The JSF will do nothing for you. So if you use these kind of components, your design will not fit in JSF.
We try to do some client scripts when ajax complete by ajaxComplete and we found that the PF 4 has implemented its own ajax events. We had some jQuery components and we need to change their code.
如果您将上面的示例更改为非Ajax项目(或至少是较少的Ajax项目),您将不会面临上述许多问题。
我们将我们的研究总结为:
JSF在一个完全基于ajax的网站上不能很好地工作。
当然,我们发现JSF中有很多不错的特性,这些特性在某些项目中可能非常有用,所以请考虑您的项目需求。
请参考JSF技术文档来回顾JSF的优点,在我看来JSF最大的优点是来自@BalusC的完全和巨大的支持;-)