Java Velocity foreach 循环

发布于 2024-11-15 15:48:37 字数 474 浏览 4 评论 0原文

我有一个 ArrayList，它在 java 中填充并将其传递给速度模板以供使用。现在，当我尝试迭代列表并从列表中创建一个“逗号”分隔的字符串时，我观察到一种不稳定的行为。

以下是我的代码

> #set($list_str="")
> #foreach($item in $list)
>     #set($list_str=$!list_str+$!item+",")
> #end

现在我看到我的变量 $list_str 具有列表的所有元素，但最后还附加了迭代器“$!item”的变量名称。

所以，假设我的列表有 [0,1,2,3,4]，我的最终结果（$list_str 的值）是 [0,1,2,3,4],$!item, 我不确定

这是否是因为列表中的空引用被填充并传递给速度模板。

任何有关解决此问题的指示将不胜感激。

谢谢

原文

I have an ArrayList that im populating within java and passing it off to a velocity template for consumption. Now when i try iterating the list and creating a 'comma' separated string from the list, Im observing an erratic behavior.

The following is my code

> #set($list_str="")
> #foreach($item in $list)
>     #set($list_str=$!list_str+$!item+",")
> #end

Now i see that my variable $list_str has all the elements of the list but at the end the variable name of the iterator '$!item' is also being appended.

So, say my list has [0,1,2,3,4], my end result(value of $list_str) is [0,1,2,3,4],$!item,

Im not sure if this is because of a null reference from within the list being populated and being passed to the velocity template.

Any pointers towards fixing this would be greatly appreciated.

Thanks

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迷雾森÷林ヴ 2024-11-22 15:48:37

我快速检查了一下，这似乎是因为 ArrayList 中存在空值。

对于如下所示填充的 ArrayList -

ArrayList list=new ArrayList();
        list.add("try");
        list.add("to");
        list.add("figure");
        list.add("it");

以及速度代码如下 -

#foreach($iter in $list)
    $!iter
    #set($list_str=$!list_str+$!iter+",")
#end
$!list_str

我得到以下输出 -

try
    to
    figure
    it
try,to,figure,it,

这似乎符合预期。

现在，当我如下填充我的 Arraylist 时——

ArrayList list=new ArrayList();
        list.add("try");
        list.add("to");
        list.add("figure");
        list.add("it");
        list.add(null);

并且使用与上面相同的速度代码，我得到以下输出——

try
    to
    figure
    it

try,to,figure,it,$!iter,

所以，我猜测您需要在代码中的某处添加空检查以避免这种情况。

谢谢
p1nG

PS：正如@Thilo 所指出的，我不确定括号来自哪里，不确定这是否是所需的行为。

I did a quick check and this seems to be because of a null value in your ArrayList.

For an ArrayList populated as below --

ArrayList list=new ArrayList();
        list.add("try");
        list.add("to");
        list.add("figure");
        list.add("it");

and with a velocity code as below --

#foreach($iter in $list)
    $!iter
    #set($list_str=$!list_str+$!iter+",")
#end
$!list_str

I get the following output --

try
    to
    figure
    it
try,to,figure,it,

which seems to be as expected.

Now when i populate my Arraylist as follows --

ArrayList list=new ArrayList();
        list.add("try");
        list.add("to");
        list.add("figure");
        list.add("it");
        list.add(null);

and with the same velocty code as above, i get the following output --

try
    to
    figure
    it

try,to,figure,it,$!iter,

So , im guessing that you need to add a null check somewhere in your code to avoid this.

Thanks
p1nG

PS: As pointed out by @Thilo Im not sure where the brackets are from, not sure if this is the desired behavior.

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苦笑流年记忆 2024-11-22 15:48:37

使用速度工具来执行此操作
例如，

#set($display = $utils.getClass().forName("org.apache.velocity.tools.generic.DisplayTool").newInstance())
#set($myArray=["nando","bob","don"])
$display.list($myArr,",")

就是这样，结果将是 nando,bob,don
如果您在列表方法中不包含第二个参数，则会得到
南多、鲍勃和唐

Use the velocity tools to do this
eg

#set($display = $utils.getClass().forName("org.apache.velocity.tools.generic.DisplayTool").newInstance())
#set($myArray=["nando","bob","don"])
$display.list($myArr,",")

Thats it the result will be nando,bob,don
if you dont include the second parameter in the list method you get
nando,bob and don

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