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Each 'Project' has a Build File, Default
build file name is 'build.xml',
Can Specify any name with '-buildfile'
command line option, Ant's buildfiles
are written in XML.
The first or root element of any buildfile
is always the <project> tag. No buildfile can be without one
nor can it have more than one.
<project
name="MyProject" default="all"
basedir=".">
...
</project>
The <project> tag has three attributes: name, default,
and basedir.
- The
name attribute gives the project
a name.
- The
default attribute refers to
a target name within the buildfile.
If you run Ant without specifying
a target on the command line,
Ant executes the default target.
If the default target doesn't
exist, Ant returns an error.
- The
basedir attribute defines
the root directory of a project.
Typically, it is ".",
the directory in which the
buildfile resides, regardless
of the directory you're in
when you run Ant. However,
basedir can also define different
points of reference.
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Each
buildfile contains one project and at
least one (default) target. Examples
are: 'compile', 'test', 'install', 'clean',
etc.
| <target
name="dosomething"> |
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<task1
param1="value1" param2="value2"> |
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<task2
param3="value3" > |
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... |
| </target> |
The <target> tag has three attributes: name, depends,
if, unless, descriptiondefault, and
basedir.
- The
name attribute gives the target
a name.
- The
depends attribute are a comma-separated
list of names of targets on
which this target depends.
- The
if attribute the name of the
property that must be set
in order for this target to
execute.
- The
unless attribute the name
of the property that must
not be set in order for this
target to execute.
- The
description attribute a short
description of this target's
function.
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Targets
must have a name and may have several
additional attributes that determine
when and if the target actually gets
executed. The target is made up of
one or more Tasks like invoke a command
or another program. Targets can have
Dependencies, examples: 'install'
depends on 'compile', Targets can
handle cascading dependencies, each
Dependency is handled only once, dependency
executed only if required.
It should be noted, however, that
Ant's depends attribute only specifies
the order in which targets should
be executed - it does not affect whether
the target that specifies the dependency(s)
gets executed if the dependent target(s)
did not (need to) run.
Ant tries to execute the targets in
the depends attribute in the order
they appear (from left to right).
Keep in mind that it is possible that
a target can get executed earlier
when an earlier target depends on
it.A target gets executed only once,
even when more than one target depends
on it .
A <task> is a
piece of code that can be executed.
A task can have multiple attributes
(or arguments, if you prefer). The
value of an attribute might contain
references to a property. These references
will be resolved before the task is
executed. Tasks have a common structure:
<name attribute1="value1"
attribute2="value2" ...
/>
where name is the name of the task,
attributeN is the attribute name,
and valueN is the value for this attribute.
Each task element of the buildfile
can have an id attribute and can later
be referred to by the value supplied
to this. The value has to be unique.
Each Task is bound to a Java class
file that Ant executes, passing to
it any arguments or sub-elements defined
with that task. The Ant tool is extensible
and it allows you to create your own
tasks
Typical
build.xml Tasks
init, sets properties, prepare, creates
directories, build, builds the system,
package, creates jar file, install,
installs an application to Tomcat
or other engine, deploy, deploy a
WAR engine, reload, update previously
installed application engine, redeploy.
Properties
A project can have a set of properties.
These might be set in the buildfile
by the property task, or might be
set outside Ant. A property has a
name and a value; the name is case-sensitive.
Properties may be used in the value
of task attributes. This is done by
placing the property name between
"${" and "}" in
the attribute value. For example,
if there is a "builddir"
property with the value "build",
then this could be used in an attribute
like this: ${builddir}/classes. This
is resolved at run-time as build/classes.
Built-in Properties
Ant provides access to all system
properties as if they had been defined
using a <property> task. For
example, ${os.name} expands to the
name of the operating system. For
a list of system properties see the
Javadoc of System.getProperties.
In addition, Ant has some built-in
properties:
basedir the
absolute path of the project's basedir
(as set with the basedir attribute
of <project>).
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; it is set in the name attribute
of <project>.
ant.java.version the
JVM version Ant detected; currently
it can hold
the values "1.1", "1.2",
"1.3" and "1.4".
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