特点

大小写敏感；

不可改变，先到先得，谁先设定，之后的都不能改变。

怎样设置

1 、设置 name 和 value 属性值，比如： <property name="srcdir" value="${basedir}/src"/>

2 、 设置 name 和 refid 属性值，比如： <property name="srcpath" refid="dao.compile.classpath"/> ，其中dao.compile.classpath 在别的地方定义。

3 、设置 name 和 location 属性值，比如： <property name="srcdir" location="src"/> ，即将 srcdir 的值设 置为：当前项目根目录的 /src 目录。

4 、设置 file 属性值，比如： <property file="build.properties"/> ， 导入 build.properties 属性文件中的属性值

5 、设置 resource 属性值，比如： <propety resource="build.properties"/>, 导入 build.properties 属性文件中的属性值

6 、设置 url 属性值，比如： <property url="http://www.blogjava.net/wiflish/build.properties"/>, 导入http://www.blogjava.net/wiflish/build.properties 属性文件中的属性值。

7 、设置环境变量，比如： <property environment="env"/> ，设置系统的环境变量为前缀 env.

<property name="tomcat.home" value="${env.CATALINA_HOME}"/> 将系统的 tomcat 安装目录设置到 tomcat.home 属性中。

内置属性

Ant’s built-in properties:

basedir	The absolute path of the project’s basedir.
ant.file	The absolute path of the buildfile.
ant.version	The version of Ant.
ant.project.name	The name of the project that is currently executing.
ant.project.default-target	The name of the currently executing project’s default target.
ant.project.invoked-targets	A comma separated list of the targets that have been specified on the command line when invoking the current.
ant.java.version	The JVM version Ant detected.
ant.core.lib	The absolute path of the ant.jar file.

System properties

java.version	Java Runtime Environment version
java.vendor	Java Runtime Environment vendor
java.vendor.url	Java vendor URL
java.home	Java installation directory
java.vm.specification.version	Java Virtual Machine specification version
java.vm.specification.vendor	Java Virtual Machine specification vendor
java.vm.specification.name	Java Virtual Machine specification name
java.vm.version	Java Virtual Machine implementation version
java.vm.vendor	Java Virtual Machine implementation vendor
java.vm.name	Java Virtual Machine implementation name
java.specification.version	Java Runtime Environment specification version
java.specification.vendor	Java Runtime Environment specification vendor
java.specification.name	Java Runtime Environment specification name
java.class.version	Java class format version number
java.class.path	Java class path
java.library.path	List of paths to search when loading libraries
java.io.tmpdir	Default temp file path
java.compiler	Name of JIT compiler to use
java.ext.dirs	Path of extension directory or directories
os.name	Operating system name
os.arch	Operating system architecture
os.version	Operating system version
file.separator	File separator ("/" on UNIX)
path.separator	Path separator (":" on UNIX)
line.separator	Line separator ("\n" on UNIX)
user.name	User's account name
user.home	User's home directory
user.dir	User's current working directory

用法

${key_name}，如：${os.name}，它将得到当前操作系统的名称。

需注意

1. 内置属性basedir

-- 不需要定义就可以直接使用，${basedir}，得到当前工程的绝对路径

-- 当在<project>标签的basedir属性中指定basedir时，之后工程中出现的所有相对路径都是相对于这个basedir所指向的路径，且${basedir}的值也将变为<project>标签中的basedir属性所指定的值。

2. property的不变性在使用<available><ant><antcall>时会被打破

3. 可以在命令行通过-DpropertyName=propertyValue的方式指定property，注意，-D于propertyName之间没有空格，使用这种方式指定的属性最先被赋值，它是在执行build文件之前就已经赋值了的。

Q&A

How can I do something like <property name="prop" value="${${anotherprop}}"/> (double expanding the property)?

Without any external help you can not.

With <script/>, which needs external libraries, you can do

With AntContrib (external task library) you can do <propertycopy name="prop" from="${anotherprop}"/> .

With Ant 1.6 you can simulate the AntContribs <propertycopy> and avoid the need of an external library:

With the 'props' antlib (external, but also from Ant) you could do the dereferencing with
${${anotherprop} - not just in the property task - instead everywhere in your buildfile (after registering the required property helper).

With Flaka (external Ant Plugin) you could do the dereferencing with #{${anotherprop}} - not just in flaka tasks, but all tasks after installing flaka's property handler.