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| <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> |
| <html> |
| <head> |
| <meta http-equiv="Content-Language" content="en-us"> |
| <link rel="stylesheet" type="text/css" href="../stylesheets/style.css"> |
| <title>Import Task</title> |
| </head> |
| <body> |
| <h2><a name="import">Import</a></h2> |
| <h3>Description</h3> |
| <p> |
| Imports another build file into the current project. |
| </p> |
| |
| <p> |
| On execution it will select the proper ProjectHelper to parse the imported |
| file, using the same algorithm as the one executed at |
| <a href="../projecthelper.html">startup</a>. The selected ProjectHelper |
| instance will then be responsible to actually parse the imported file. |
| </p> |
| |
| <p> |
| <b>Note</b> as seen above, this task heavily relies on the ProjectHelper |
| implementation and doesn't really perform any work of its own. If |
| you have configured Apache Ant to use a ProjectHelper other than Ant's |
| default, this task may or may not work. |
| </p> |
| |
| <p> |
| In the common use case where only Ant's default project helper is |
| used, it basically works like the |
| <a href="http://ant.apache.org/faq.html#xml-entity-include">Entity |
| Includes as explained in the Ant FAQ</a>, as if the imported file was |
| contained in the importing file, minus the top <code><project></code> |
| tag. |
| </p> |
| |
| <p> |
| The import task may only be used as a top-level task. This means that |
| it may not be used in a target. |
| </p> |
| <p> |
| There are two further functional aspects that pertain to this task and |
| that are not possible with entity includes: |
| <ul> |
| <li>target overriding</li> |
| <li>special properties</li> |
| </ul> |
| </p> |
| <h4>Target overriding</h4> |
| |
| <p>If a target in the main file is also present in at least one of the |
| imported files, the one from the main file takes precedence.</p> |
| |
| <p>So if I import for example a <i>docsbuild.xml</i> file named <b>builddocs</b>, |
| that contains a "<b>docs</b>" target, I can redefine it in my main |
| buildfile and that is the one that will be called. This makes it easy to |
| keep the same target name, so that the overriding target is still called |
| by any other targets--in either the main or imported buildfile(s)--for which |
| it is a dependency, with a different implementation. The target from <i>docsbuild.xml</i> is |
| made available by the name "<b>builddocs</b><b>.docs</b>". |
| This enables the new implementation to call the old target, thus |
| <i>enhancing</i> it with tasks called before or after it.</p> |
| |
| <p>If you use the <i>as</i> attribute of the task, its value will be |
| used to prefix the overridden target's name instead of the name |
| attribute of the project tag.</p> |
| |
| <h4>Special Properties</h4> |
| |
| <p>Imported files are treated as they are present in the main |
| buildfile. This makes it easy to understand, but it makes it impossible |
| for them to reference files and resources relative to their path. |
| Because of this, for every imported file, Ant adds a property that |
| contains the path to the imported buildfile. With this path, the |
| imported buildfile can keep resources and be able to reference them |
| relative to its position.</p> |
| |
| <p>So if I import for example a <i>docsbuild.xml</i> file named <b>builddocs</b>, |
| I can get its path as <b>ant.file.builddocs</b>, similarly to the <b>ant.file</b> |
| property of the main buildfile.</p> |
| |
| <p>Note that "builddocs" is not the filename, but the name attribute |
| present in the imported project tag.</p> |
| <p> |
| If the imported file does not have a name attribute, the ant.file.projectname |
| property will not be set. |
| </p> |
| |
| <p>Since Ant 1.8.0 the task can also import resources from URLs or |
| classpath resources (which are URLs, really). If you need to know |
| whether the current build file's source has been a file or an URL |
| you can consult the |
| property <b>ant.file.type.<em>projectname</em></b> (using the same |
| example as above <b>ant.file.type.builddocs</b>) which either have |
| the value "file" or "url".</p> |
| |
| <h4>Resolving files against the imported file</h4> |
| |
| <p>Suppose your main build file called <code>importing.xml</code> |
| imports a build file <code>imported.xml</code>, located anywhere on |
| the file system, and <code>imported.xml</code> reads a set of |
| properties from <code>imported.properties</code>:</p> |
| |
| <pre><!-- importing.xml --> |
| <project name="importing" basedir="." default="..."> |
| <import file="${path_to_imported}/imported.xml"/> |
| </project> |
| |
| <!-- imported.xml --> |
| <project name="imported" basedir="." default="..."> |
| <property file="imported.properties"/> |
| </project> |
| </pre> |
| |
| <p>This snippet however will resolve <code>imported.properties</code> |
| against the basedir of <code>importing.xml</code>, because the basedir |
| of <code>imported.xml</code> is ignored by Ant. The right way to use |
| <code>imported.properties</code> is:</p> |
| |
| <pre> |
| <!-- imported.xml --> |
| <project name="imported" basedir="." default="..."> |
| <dirname property="imported.basedir" file="${ant.file.imported}"/> |
| <property file="${imported.basedir}/imported.properties"/> |
| </project> |
| </pre> |
| |
| <p>As explained above <code>${ant.file.imported}</code> stores the |
| path of the build script, that defines the project called |
| <code>imported</code>, (in short it stores the path to |
| <code>imported.xml</code>) and <a |
| href="dirname.html"><code><dirname></code></a> takes its |
| directory. This technique also allows <code>imported.xml</code> to be |
| used as a standalone file (without being imported in other |
| project).</p> |
| |
| <p>The above description only works for imported files that actually |
| are imported from files and not from URLs. For files imported from |
| URLs using resources relative to the imported file requires you to |
| use tasks that can work on non-file resources in the first place. |
| To create a relative resource you'd use something like:</p> |
| |
| <pre> |
| <loadproperties> |
| <url baseUrl="${ant.file.imported}" |
| relativePath="imported.properties"/> |
| </loadproperties> |
| </pre> |
| |
| <h3>Parameters</h3> |
| <table border="1" cellpadding="2" cellspacing="0"> |
| <tbody> |
| <tr> |
| <td valign="top"><b>Attribute</b></td> |
| <td valign="top"><b>Description</b></td> |
| <td align="center" valign="top"><b>Required</b></td> |
| </tr> |
| <tr> |
| <td valign="top"> |
| file |
| </td> |
| <td valign="top"> |
| The file to import. If this is a relative file name, the file name will be resolved |
| relative to the <i>importing</i> file. <b>Note</b>, this is unlike most other |
| ant file attributes, where relative files are resolved relative to ${basedir}. |
| </td> |
| <td valign="top" align="center">Yes or a nested resource collection</td> |
| </tr> |
| <tr> |
| <td valign="top"> |
| optional |
| </td> |
| <td valign="top"> |
| If true, do not stop the build if the file does not exist, |
| default is false. |
| </td> |
| <td valign="top" align="center">No</td> |
| </tr> |
| <tr> |
| <td valign="top"> |
| as |
| </td> |
| <td valign="top"> |
| Specifies the prefix prepended to the target names. If |
| omitted, the name attribute of the project tag of the |
| imported file will be used. |
| </td> |
| <td valign="top" align="center">No</td> |
| </tr> |
| <tr> |
| <td valign="top"> |
| prefixSeparator |
| </td> |
| <td valign="top"> |
| Specifies the separator to be used between the prefix and the |
| target name. Defaults to ".". |
| </td> |
| <td valign="top" align="center">No</td> |
| </tr> |
| </tbody> |
| </table> |
| |
| <h3>Parameters specified as nested elements</h3> |
| |
| <h4>any <a href="../Types/resources.html">resource</a> or resource |
| collection</h4> |
| |
| <p>The specified resources will be imported. <em>Since Ant |
| 1.8.0</em></p> |
| |
| <h3>Examples</h3> |
| <pre> <import file="../common-targets.xml"/> |
| </pre> |
| |
| <p>Imports targets from the common-targets.xml file that is in a parent |
| directory.</p> |
| |
| <pre> <import file="${deploy-platform}.xml"/> |
| </pre> |
| |
| <p>Imports the project defined by the property deploy-platform</p> |
| |
| <pre> |
| <import> |
| <javaresource name="common/targets.xml"> |
| <classpath location="common.jar"/> |
| </javaresource> |
| </import> |
| </pre> |
| |
| <p>Imports targets from the targets.xml file that is inside the |
| directory common inside the jar file common.jar.</p> |
| |
| <h3>How is <import> different |
| from <a href="include.html"><include></a>?</h3> |
| |
| <p>The short version: Use import if you intend to override a target, |
| otherwise use include.</p> |
| |
| <p>When using import the imported targets are available by up to two |
| names. Their "normal" name without any prefix and potentially with |
| a prefixed name (the value of the as attribute or the imported |
| project's name attribute, if any).</p> |
| |
| <p>When using include the included targets are only available in the |
| prefixed form.</p> |
| |
| <p>When using import, the imported target's depends attribute |
| remains unchanged, i.e. it uses "normal" names and allows you to |
| override targets in the dependency list.</p> |
| |
| <p>When using include, the included targets cannot be overridden and |
| their depends attributes are rewritten so that prefixed names are |
| used. This allows writers of the included file to control which |
| target is invoked as part of the dependencies.</p> |
| |
| <p>It is possible to include the same file more than once by using |
| different prefixes, it is not possible to import the same file more |
| than once.</p> |
| |
| <h4>Examples</h4> |
| |
| <p><i>nested.xml</i> shall be:</p> |
| |
| <pre> |
| <project> |
| <target name="setUp"> |
| <property name="prop" value="in nested"/> |
| </target> |
| |
| <target name="echo" depends="setUp"> |
| <echo>prop has the value ${prop}</echo> |
| </target> |
| </project> |
| </pre> |
| |
| <p>When using import like in</p> |
| |
| <pre> |
| <project default="test"> |
| <target name="setUp"> |
| <property name="prop" value="in importing"/> |
| </target> |
| |
| <import file="nested.xml" as="nested"/> |
| |
| <target name="test" depends="nested.echo"/> |
| </project> |
| </pre> |
| |
| <p>Running the build file will emit: |
| |
| <pre> |
| setUp: |
| |
| nested.echo: |
| [echo] prop has the value in importing |
| |
| test: |
| |
| </pre> |
| |
| <p>When using include like in</p> |
| |
| <pre> |
| <project default="test"> |
| <target name="setUp"> |
| <property name="prop" value="in importing"/> |
| </target> |
| |
| <include file="nested.xml" as="nested"/> |
| |
| <target name="test" depends="nested.echo"/> |
| </project> |
| </pre> |
| |
| <p>Running the target build file will emit: |
| |
| <pre> |
| nested.setUp: |
| |
| nested.echo: |
| [echo] prop has the value in nested |
| |
| test: |
| |
| </pre> |
| |
| <p>and there won't be any target named "echo" on the including build file.</p> |
| |
| </body> |
| </html> |
