速度foreach排序列表 | 速度foreach排序列表

本文介绍了速度foreach排序列表的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！

问题描述

到目前为止，我试过了

<$ p $在$ {pro.test} .sort（$ {pro.test.sortOrder}））
...
#end

但是这是抛出错误，我还试着用

pre $ $ pro.test.sort（$ { ...
#end

这一次没有错误，但是控制不是进入循环，

，那么没有 sort 或 sortOrder 方法。假设在 $ sorter 变量下可以使用Velocity SortTool ，对于初学者来说，可以尝试一下：

  #foreach（$ sorter.sort（$ pro.test））
 ... 
 #end

现在， $ pro.test.sortOrder 实际上会尝试调用下面的一个： getsortOrder（）， getSortOrder（）， get（sortOrder）， issortOrder / code>， isSortOrder（）。

Can any one suggest how to sort this list in velocity ?

So far I tried

    #foreach($it in ${pro.test}.sort(${pro.test.sortOrder}))
    .........
    #end

But it is throwing error, Also I tried with

    #foreach($it in ${pro.test.sort(${pro.test.sortOrder})})
    .........
    #end

this time no error but the control is not coming inside loop,

reference

解决方案

First, using ${...} is a way of helping the Velocity parser know exactly what you consider to be Velocity code. Normally, when velocity sees $something.somethingElse.somethingMore, it tries to parse as much as it can until it sees a word breaking character, such as a space or comma. When it sees ${something.somethingElse}.somethingMore, it only reads until the matching } as actual code, the rest is plain text. This means that ${pro.test}.sort(...) considers .sort(...) as plain text that should be printed, so it wouldn't call it as a method. That's why the first example fails with an error. You only need to use the formal syntax outside directives, though, you can just remove all the { and } from the call when inside #foreach(...).

Second, #foreach is very lax, it doesn't complain when you try to pass something invalid in the iterated scope; if it doesn't resolve to a valid list, then it simply ignores it and considers that there's nothing to iterate over. When something doesn't work as expected, print the values you're working with:

$pro.test $pro.test.class $pro.test.sortOrder $pro.test.sortOrder.class
#foreach ($it in ${pro.test.sort(${pro.test.sortOrder})})
  ...
#end

What does that print? Is $pro.test really a set? Is $pro.test.sortOrder a valid sort order specification, as expected by SortTool?

If $pro.test is a standard implementation of the Set interface, then there's no sort or sortOrder method. Assuming that the Velocity SortTool is available under the $sorter variable, you could try, for starters:

#foreach ($it in $sorter.sort($pro.test))
   ...
#end

Now, what exactly is $pro.test.sortOrder supposed to be? If it's a property, then note that for security reasons Velocity doesn't allow access directly to properties, it can only call methods. As a means of simplifying the syntax, $pro.test.sortOrder will actually try to call one of these: getsortOrder(), getSortOrder(), get("sortOrder"), issortOrder(), isSortOrder().

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