核心内容摘要
robotstxt是什么意思
搜索引擎数据库实现_搜索引擎数据库架构设计与实现方案
The element in the is a truncated version of
the element. It consists of the ,
, and elements. The
elements only include these four elements because they
concerns themselves with the build system as a whole (which is the role
of the file), not about individual project object model
settings.
If a profile is active from , its values will override any
equivalently ID'd profiles in a POM or file.
Activation
Activations are the key of a profile. Like the POM's profiles, the power
of a profile comes from its ability to modify some values only under
certain circumstances; those circumstances are specified via an
element.
Activation occurs when all specified criteria have been met, though not
all are required at once.
jdk: has a built in, Java-centric check in the
element. This will activate if the test is run under a jdk
version number that matches the prefix given. In the above example,
will match. Ranges are also supported.
See the
for more details about supported ranges.
os: The element can define some operating system specific
properties shown above. See the
for more details about OS values.
property: The will activate if Maven detects a
property (a value which can be dereferenced within the POM by
) of the corresponding pair.
file: Finally, a given filename may activate the by
the of a file, or if it is .
The element is not the only way that a may be
activated. The file's element may contain
the profile's . They may also be activated explicitly through the
command line via a comma separated list after the flag (e.g.
).
To see which profile will activate in a certain build, use the
.
Properties
Maven properties are value placeholder, like properties in Ant. Their
values are accessible anywhere within a POM by using the notation
, where is the property. They come in five different styles,
all accessible from the file:
: Prefixing a variable with “env.” will return the shell's
environment variable. For example, contains the $path
environment variable ( in Windows).
: A dot (.) notated path in the POM will contain the
corresponding element's value. For example:
is accessible via
.
: A dot (.) notated path in the will
contain the corresponding element's value. For example:
is accessible via
.
Java System Properties: All properties accessible via
are available as POM properties,
such as .
: Set within a
