grails 2.0 与 1.3.7，flash.message 和 gsps 的工作方式
在 Grails 1.3.7 中，默认控制器将生成如下代码，用于在域类的保存操作中显示 Flash 消息（只需注意赋值的开始，即“${ ）：
flash.message = "${message(code: 'default.created.message', args: [message(code: 'issue.label', default: 'Issue'), issueInstance.id])}"
在 Grails 2.0 中，这更改为
flash.message = message(code: 'default.created.message', args: [message(code: 'issue.label', default: 'Issue'), issueInstance.id])
我们可以注意到差异是在 1.3.7 中，显然在 gsp 内部传递了一个字符串，在“gsp 编译时/运行时？”处。不Grails 2.0 中不再需要。这是因为 Groovy 功能发生了变化/改进吗？简而言之，我试图了解 Grails 的不同之处，即不再需要传递在 GSP 内部进行计算的消息，以及可以在哪些方面利用它。总体而言，Grails 2.0 中的这种差异/变化
谢谢，Ray 。
In Grails 1.3.7, the default controllers would produce code like the following for the display of flash messages in the save action for a domain class (just notice the start of the assignment, i.e. the "${ ):
flash.message = "${message(code: 'default.created.message', args: [message(code: 'issue.label', default: 'Issue'), issueInstance.id])}"
In Grails 2.0, this is changed to
flash.message = message(code: 'default.created.message', args: [message(code: 'issue.label', default: 'Issue'), issueInstance.id])
Where we can note the difference is at the start of the assignment. In 1.3.7, apparently a string is passed to be evaluated inside the gsp, at "gsp compile-time / run-time?". It appears this no longer needed in Grails 2.0. Is this because of a changed / improved Groovy capability? In short, I'm trying to understand what's different about Grails that passing a message that evaluates inside the GSP is no longer needed, and where one can take advantage of this difference/change in Grails 2.0 in general.
Thanks, Ray
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我认为第二种（Grails 2.0）方式更干净一些。由于这两种替代方案本质上都计算为相同的字符串，因此在 GString 中计算的第一个替代方案似乎没有任何值。事实上，它是一个 GString，这意味着它将执行额外的表达式 (${...}) 处理（因此会稍微慢一些），而 Grails 2.0 版本只是直接进入消息标签库。
不知道为什么它最初是用第一种方式完成的...顺便说一句，我不认为 GString 内部的代码在 GSP 处理期间被评估 - 它是在 GString 分配给控制器中的 flash.message 时评估的（与 Grails 2.0 版本同时）...
I think the second (Grails 2.0) way is a bit cleaner. Since both the alternatives essentially evaluate to the same String, there doesn't seem to be any value in the first one being evaluated in a GString. The fact that it is a GString means that it'll be doing the extra expression (${...}) processing (so will be marginally slower), whereas the Grails 2.0 version just goes straight to the message taglib.
Not sure why it was originally done the first way... BTW, I don't think the code inside the GString is evaluated during the GSP processing - it is evaluated at the time the GString is assigned to flash.message in the controller (same time as the Grails 2.0 version)...