blocks|key|5407745|text|我要注意的一件事是，与使用(正常的)全页HTTP传递相比，您的服务器很可能会遇到更多的HTTP请求。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|5407746|让我解释一下。当你的网页支持AJAX时，你的客户最终会创建更多的HTTP请求(比如说)表单填充、页面片段重新生成等。我见过开发人员疯狂使用AJAX的场景，并使网页成为一个主要的动态文档。这会带来很好的用户体验(如果做得好的话)，但每个请求都会导致服务器命中，从而导致可伸缩性和延迟问题。|5407747|注意-这并不是DWR所特有的，而是一个AJAX问题。我使用过DWR，它工作得很好。不幸的是，我发现它工作得很好，而且很容易，所有的东西都变成了远程处理的候选者，你可能会得到大量的小请求。|5407748|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|H|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|I|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|J|8|@]|9|@]|A|$]]|$1|F|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|G|$]]

One thing I would watch out for is that your server will most likely get hit by more HTTP requests than if you have the (normal) full page HTTP delivery.

Let me explain. When your web page is AJAX-enabled, your clients will end up creating more HTTP requests for (say) form filling, page-fragment regeneration etc. I've seen scenarios where developers have gone AJAX-crazy, and made the web page a largely dynamic document. This results in a great user experience (if done well), but every request results in a server hit, leading to scalability and latency issues.

Note - this isn't particular to DWR, but is an AJAX issue. I've used DWR, and it works nicely. Unfortunately, I found that it worked so well, and so easily, that everything becomes a candidate for remoting, and you can end up with huge numbers of small requests.

blocks|key|353686|text|我用DWR做了一个项目--一个非常好的工具。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|353687|不过，我对开发的速度并不信服。他们确实在on+the+development+log上发布了他们正在努力推出3.0，但最后一个稳定版本2.0是在2006年夏天发布的。从支持的角度来看，这有点令人担忧--尤其是bug修复。|offset|length|353688|entityMap|0|LINK|mutability|MUTABLE|url|http://directwebremoting.org/dwr/devlog/index.html^0|0|K|M|0|0^^$0|@$1|2|3|4|5|6|7|N|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|O|8|@]|9|@$D|P|E|Q|1|R]]|A|$]]|$1|F|3|-4|5|6|7|S|8|@]|9|@]|A|$]]]|G|$H|$5|I|J|K|A|$L|M]]]]

I worked on a project with DWR - a really nice tool.

I'm not convinced about the pace of development though. They did post <a href="http://directwebremoting.org/dwr/devlog/index.html" rel="nofollow noreferrer">on the development log</a> that they're working on getting 3.0 out the door, but the last stable release - 2.0 - was out in summer 2006. It's a bit worrying taken from a support perspective - bug fixes especially.

blocks|key|356264|text|我遇到的主要问题是试图在一个系统上编写负载测试脚本，其中大部分工作都是通过DWR调用完成的。与只回复一堆参数不断变化的urls相比，调用的格式很难复制。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|356265|尽管如此，DWR仍然是一个优秀的框架，它使得实现Javascript+->+Java+RPC变得非常容易。|356266|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|F|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|G|8|@]|9|@]|A|$]]|$1|D|3|-4|5|6|7|H|8|@]|9|@]|A|$]]]|E|$]]

Main problem I've experienced is trying to script a load test on a system where the main bulk of the work is done via DWR calls. The format of the calls is difficult to replicate when compared with just replying a bunch of urls with changing parameters.

Still DWR is an excellent framework and makes implementing Javascript -> Java RPC pretty damn easy.

blocks|key|353714|text|当前DWR+3.x中任何用户都应该注意的一个特性是，当bean的实例具有空值的属性时，这些属性仍将被注入到JSON中，并且这些冗余数据确实会影响性能。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|353715|当属性值为NULL时，通常不应将其发送到前端。|353716|问题详细信息：http://dwr.2114559.n2.nabble.com/Creating-Custom-bean-converter-td6178318.html|offset|length|353717|entityMap|0|LINK|mutability|MUTABLE|url|http://dwr.2114559.n2.nabble.com/Creating-Custom-bean-converter-td6178318.html^0|0|0|7|26|0|0^^$0|@$1|2|3|4|5|6|7|P|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|Q|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|R|8|@]|9|@$F|S|G|T|1|U]]|A|$]]|$1|H|3|-4|5|6|7|V|8|@]|9|@]|A|$]]]|I|$J|$5|K|L|M|A|$N|O]]]]

One feature missing of current DWR 3.x that any user should take good care is that when an instance of a bean has properties of NULL value, those properties will be still injected to the JSON and these redundant data DO affect the performance.

When a property has the value of NULL, usually it should not be sent to frontend.

Details of problem: <a href="http://dwr.2114559.n2.nabble.com/Creating-Custom-bean-converter-td6178318.html" rel="nofollow">http://dwr.2114559.n2.nabble.com/Creating-Custom-bean-converter-td6178318.html</a>

blocks|key|5407806|text|当您的站点有很多ajax调用时，DWR是一个很好的工具。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|5407807|进行dwr+rpc调用的每个页面都需要包括：|5407808|a)对应于正在进行的调用的接口文件。以及b)与dwr捆绑在一起的js文件，该文件包含使这些调用成为可能的dwr引擎代码。例如，<script+src="/dwr/engine.js"+></script>|offset|length|style|CODE|5407809|在优化web应用时经常使用的一种技术是，当服务器上的资源(如js文件)没有改变时，尽可能多地使用浏览器缓存。|5407810|engine.js是永远不会改变的东西，除非你把你的dwr升级到一个新的版本。但是，默认情况下，engine.js不是由您的not服务器提供服务的静态文件。它被捆绑为dwr工具本身的一部分，并由dwr控制器/+served提供服务，这对客户端缓存没有帮助。|5407811|因此，最好将engine.js保存在let服务器的文档根目录下，并让let服务器将其作为静态文件提供服务。|5407812|entityMap^0|0|0|1R|13|0|0|0|0^^$0|@$1|2|3|4|5|6|7|R|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|S|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|T|8|@$F|U|G|V|H|I]]|9|@]|A|$]]|$1|J|3|K|5|6|7|W|8|@]|9|@]|A|$]]|$1|L|3|M|5|6|7|X|8|@]|9|@]|A|$]]|$1|N|3|O|5|6|7|Y|8|@]|9|@]|A|$]]|$1|P|3|-4|5|6|7|Z|8|@]|9|@]|A|$]]]|Q|$]]

DWR is a great tool when your site has a lot of ajax calls. 

Each page that makes dwr rpc calls needs to include :

a) an interface file corresponding to the calls being made.
and 
b) a js file bundled with dwr that contains the dwr engine code that makes these calls possible. for e.g. <code>&lt;script src="/dwr/engine.js" &gt;&lt;/script&gt;</code>

one technique that is frequently used while optimizing web applications is to use the browser cache as much as possible when a resource(like a js file) has not changed on a server. 

engine.js is something that will never change unless you upgrade your dwr to a newer version. But, by default, engine.js is not a static file served by your webserver. its bundled as part of the dwr tool itsef and is served by the dwr controller/servlet.this doesnt aid client side caching. 

So, it is beneficial to save engine.js under the document root of your webserver and let the webserver serve it as a static file.

blocks|key|5407845|text|传输对象(封送处理)的其他解决方案之间最大的区别是对象引用。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|5407846|例如，如果您使用它来传输树：|5407847|一个|5407848|%7C-B|5407849|%7C-C|5407850|在列表{A，B，C}中：|5407851|B.parent+=A+C.parent=+A|5407852|那么A在Javascrit中是同一个对象！|5407853|不好的一面是，如果你有复杂的结构，有循环依赖和大量的对象:+A<-B，B<-C，C<-B，C<.A，...它可能会崩溃。|5407854|无论如何，我在一个真实的项目中使用了它，数百家公司在生产中使用它将数千个对象传输到一个单独的html页面，以便绘制一个复杂的图形，它工作得很好，性能也很好。|5407855|entityMap^0|0|0|0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|V|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|W|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|X|8|@]|9|@]|A|$]]|$1|F|3|G|5|6|7|Y|8|@]|9|@]|A|$]]|$1|H|3|I|5|6|7|Z|8|@]|9|@]|A|$]]|$1|J|3|K|5|6|7|10|8|@]|9|@]|A|$]]|$1|L|3|M|5|6|7|11|8|@]|9|@]|A|$]]|$1|N|3|O|5|6|7|12|8|@]|9|@]|A|$]]|$1|P|3|Q|5|6|7|13|8|@]|9|@]|A|$]]|$1|R|3|S|5|6|7|14|8|@]|9|@]|A|$]]|$1|T|3|-4|5|6|7|15|8|@]|9|@]|A|$]]]|U|$]]

The biggest difference among other solutions to transfer objects (marshaling) is object references.

For instance, if you use it to transfer a tree:

A

|-B

|-C

in a list {A,B,C}:

B.parent = A
C.parent= A

then A is the same object in Javascrit!

On the bad side, if you have complex structures with circular dependencies and lot of objects: A&lt;-B, B&lt;-C, C&lt;-B, C&lt;.A,... it could crash.

Anyway, I use it in a real project used by many hundreds of companies in production to transfer thousands of objects to a single html page in order to draw a complex graph and it works nicely with a good performance.

While using DWR in a intranet, will disadvantages like perfomance or security issues occur?
Direct web remoting is a tool which uses Ajax request to contact a server from a js file.

What is the disadvantage of DWR?

翻译质量差，导致语言生硬或混乱。

没有提供实际的解决方法或示例。

解答不清晰，无法理解或解决问题。

页面排版不美观，阅读体验差。

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在intranet中使用DWR时，是否会出现性能或安全问题等缺点？Direct web remoting是一个使用Ajax请求从js文件联系服务器的工具。

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