遇到了問題，編譯的時候，有一些目錄，比如
tr\src
tr\src_x1 for prj X1
tr\src_x2 for prj X2
_______ for prj X3, X3中沒有，怎么設置ant腳本呢？
<target name="compile-tr">
<mkdir dir="${tr.classes.dir}" />
<javac destdir="${tr.classes.dir}" debug="${compiler.debug}" optimize="${compiler.optimize}" source="${compiler.source}" target="${compiler.target}" deprecation="true">
<classpath>
<path refid="devel.lib" />
</classpath>
<src path="${tr.src.dir}" />
<src path="${tr.src.dir}_${project.code}" />
</javac>
</target>
在編譯X3的時候，這肯定是失敗的。
怎么辦呢？ 通過Condition和Avaliable來實現。（貼一個粗糙的示范實現）
<target name="compile-3tr" depends="dir.check" if="dir.exists">
<mkdir dir="${tr.classes.dir}" />
<javac destdir="${tr.classes.dir}" debug="${compiler.debug}" optimize="${compiler.optimize}" source="${compiler.source}" target="${compiler.target}" deprecation="true">
<classpath>
<path refid="devel.lib" />
</classpath>
<src path="${tr.src.dir}" />
<src path="${tr.src.dir}_${project.code}" />
</javac>
</target>
<target name="dir.check">
<condition property="dir.exists" value="true">
<available file="${tr.src.dir}_${project.code}" type="dir"/>
</condition>
<mkdir dir="${tr.classes.dir}" />
</target>
居然在網上找到一個更贊的招
<target name="go" depends="file-checks, do-something-with-first-file, do-something-with-second-file"/>
<target name="file-checks">
<available file="/home/doc/somefile" property="first.file.found"/>
<available file="/usr/local/somefile" property="second.file.found"/>
</target>
<target name="do-something-with-first-file" if="first.file.found">
???
</target>
<target name="do-something-with-second-file" if="second.file.found">
???
</target>
原來if....then....else需要
ant-contrib的支持，怪不得我一直失敗
ant-contrib
<if>
<available file="file1"/>
<then>
<property name="file.exists" value="true"/>
</then>
<else>
<if>
<available file="file2"/>
<then>
<copy file="file2" tofile="file1"/>
<property name="file.exists" value="true"/>
</then>
</if>
</else>
</if>
最后我很生氣的找到了apache本身的技術文檔
http://ant.apache.org/manual/properties.html#if+unless
If/Unless Attributes
The
<target> element and various tasks (such as
<fail>) and task elements (such as
<test> in
<junit>) support if and unless attributes which can be used to control whether the item is run or otherwise takes effect.
In Ant 1.7.1 and earlier, these attributes could only be property names. The item was enabled if a property with that name was defined - even to be the empty string or false - and disabled if the property was not defined. For example, the following works but there is no way to override the file existence check negatively (only positively):
<target name="-check-use-file"> <available property="file.exists" file="some-file"/></target><target name="use-file" depends="-check-use-file" if="file.exists"> <!-- do something requiring that file
--></target><target name="lots-of-stuff" depends="use-file,other-unconditional-stuff"/> As of Ant 1.8.0, you may instead use property expansion; a value of true (or on or yes) will enable the item, while false (or off or no) will disable it. Other values are still assumed to be property names and so the item is enabled only if the named property is defined.
Compared to the older style, this gives you additional flexibility, because you can override the condition from the command line or parent scripts:
<target name="-check-use-file" unless="file.exists"> <available property="file.exists" file="some-file"/></target><target name="use-file" depends="-check-use-file" if="${file.exists}"> <!-- do something requiring that file --></target><target name="lots-of-stuff" depends="use-file,other-unconditional-stuff"/> Now ant -Dfile.exists=false lots-of-stuff will run other-unconditional-stuff but not use-file, as you might expect, and you can disable the condition from another script too:
<antcall target="lots-of-stuff"> <param name="file.exists" value="false"/></antcall> Similarly, an unless attribute disables the item if it is either the name of property which is defined, or if it evaluates to a true-like value. For example, the following allows you to define skip.printing.message=true in my-prefs.properties with the results you might expect:
<property file="my-prefs.properties"/><target name="print-message" unless="${skip.printing.message}"> <echo>hello!
</echo></target>