如何检查属性在 Ant 中是否有价值 [英] How to check if a property has value in Ant

问题描述

我有一个用于构建的 Ant XML 文件.

I have an Ant XML file which I use for build.

我有 3 个属性.如果这些属性不包含任何值，我想中断构建.如果值为空，我也想中断构建.

I have 3 properties. I want to break the build if these properties does not contain any value. Also I want to break the build if the value is empty.

如何在 Ant 中执行此操作?

How can I do this in Ant?

我使用 Ant 而不是 Ant-contrib.

I a using Ant and not Ant-contrib.

推荐答案

您可以通过 任务使用条件:

You can use conditions using the <fail> task:

<fail message="Property &quot;foo&quot; needs to be set to a value">
    <condition>
        <or>
            <equals arg1="${foo}" arg2=""/>
            <not>
                <isset property="foo"/>
            </not>
       </or>
   </condition>

这相当于说if (not set ${foo} or ${foo} = "") 是伪代码.您必须从内到外读取 XML 条件.

This is equivalent to saying if (not set ${foo} or ${foo} = "") is pseudocode. You have to read the XML conditions from the inside out.

如果您只关心是否设置了变量，而不关心它是否已设置，则您可以在 <fail> 任务中使用 子句有实际价值.

You could have used the <unless> clause on the <fail> task if you only cared whether or not the variable was set, and not whether it has an actual value.

<fail message="Property &quot;foo&quot; needs to be set"
    unless="foo"/>

但是，如果设置了属性，但没有值，这不会失败.

However, this won't fail if the property is set, but has no value.

有一个技巧可以使这更简单

There's a trick that can make this simpler

 <!-- Won't change the value of `${foo}` if it's already defined -->
 <property name="foo" value=""/>
 <fail message="Property &quot;foo&quot; has no value">
     <condition>
             <equals arg1="${foo}" arg2=""/>
     </condition>
</fail>

请记住，我无法重置属性！如果 ${foo} 已经有一个值，上面的 任务将不会做任何事情.这样，我可以消除 条件.这可能很好，因为您拥有三个属性:

Remember that I can't reset a property! If ${foo} already has a value, the <property> task above won't do anything. This way, I can eliminate the <isset> condition. It might be nice since you have three properties:

<property name="foo" value=""/>
<property name="bar" value=""/>
<property name="fubar" value=""/>
<fail message="You broke the build, you dufus">
    <condition>
        <or>
            <equals arg1="${foo}" arg2=""/>
            <equals arg1="${bar}" arg2=""/>
            <equals arg1="${fubar}" arg2=""/>
       </or>
    </condition>
</fail>

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