如何检查是否一个属性在ANT价值 [英] How to check if a property has value in ANT

问题描述

我有我使用的共建ANT的XML文件。

I have a ANT XML file which I use for build.

我有3个属性。我想打破建立，如果这些属性不包含任何值。

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

此外，我想打破建立如果值是空的。

Also I want to break the build if the value is empty

我怎样才能做到这一点ANT？

How can I do this in ANT?

我一个使用Ant和不ANT-的contrib

I a using ANT and not ANT-CONTRIB

在此先感谢

KARTHIK

推荐答案

您可以通过使用条件的＆LT;＆失败GT; 任务：

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>

这是等同于说的 如果（未设置$ {富}或$ {富} =） 的是伪code。你必须从内到外读取XML的条件。

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

您可能已经使用了＆LT;除非＆GT; 在＆LT条款;失败＆GT; 任务，如果你只关心变量是否被设置，并且不是否它有一个实际值。

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"/>

不过，这也不会，如果属性设置失败，但是没有价值。

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

有一个技巧，可以使这个简单

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，我不能重置属性！如果 $ {富} 已经有一个值，在＆LT;性＆gt; 任务上面不会做任何事情。这样一来，我可以消除＆LT;＆使用isset GT; 状态。因为你有三个属性可能是不错的：

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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