## Mapping File Names

Some tasks take source files and create target files. Depending on the task, it may be quite obvious which name a target file will have (using javac, you know there will be `.class` files for your `.java` files)—in other cases you may want to specify the target files, either to help Apache Ant or to get an extra bit of functionality.

While source files are usually specified as filesets, you don't specify target files directly—instead, you tell Ant how to find the target file(s) for one source file. An instance of `org.apache.tools.ant.util.FileNameMapper` is responsible for this. It constructs target file names based on rules that can be parameterized with from and to attributes—the exact meaning of which is implementation-dependent.

These instances are defined in `<mapper>` elements with the following attributes:

Attribute | Description | Required
--- | --- | ---
type | specifies one of the built-in implementations. | Exactly one of these
classname | specifies the implementation by class name.
classpath | the classpath to use when looking up `classname`. | No
classpathref | the classpath to use, given as reference to a path defined elsewhere. | No
from | the `from` attribute for the given implementation. | Depends on implementation
to | the `to` attribute for the given implementation. | Depends on implementation

Note that Ant will not automatically convert / or \ characters in the to and from attributes to the correct directory separator of your current platform. If you need to specify this separator, use `${file.separator}` instead. For the regexp mapper, `${file.separator}` will not work, as on Windows it is the \ character, and this is an escape character for regular expressions, one should use the `handledirsep` attribute instead.

### Parameters specified as nested elements

The classpath can be specified via a nested `<classpath>`, as well—that is, a path-like structure.

Since Ant 1.7.0, nested File Mappers can be supplied via either `<mapper>` elements or `<typedef>`'d implementations of `org.apache.tools.ant.util.FileNameMapper`. If nested File Mappers are specified by either means, the mapper will be implicitly configured as a composite mapper.

### The built-in mapper types

All built-in mappers are case-sensitive.

Since Ant 1.7.0, each of the built-in mapper implementation types is directly accessible using a specific tagname. This makes it possible for filename mappers to support attributes in addition to the generally available to and from.
The `<mapper type|classname="...">` usage form remains valid for reasons of backward compatibility.

#### identity

The target file name is identical to the source file name. Both to and from will be ignored.

##### Examples

    <mapper type="identity"/>
    <identitymapper/>

Source file name | Target file name
--- | ---
`A.java` | `A.java`
`foo/bar/B.java` | `foo/bar/B.java`
`C.properties` | `C.properties`
`Classes/dir/dir2/A.properties` | `Classes/dir/dir2/A.properties`

#### flatten

The target file name is identical to the source file name, with all leading directory information stripped off. Both to and from will be ignored.

##### Examples

    <mapper type="flatten"/>
    <flattenmapper/>

Source file name | Target file name
--- | ---
`A.java` | `A.java`
`foo/bar/B.java` | `B.java`
`C.properties` | `C.properties`
`Classes/dir/dir2/A.properties` | `A.properties`

#### merge

The target file name will always be the same, as defined by to—from will be ignored.

##### Examples

    <mapper type="merge" to="archive.tar"/>
    <mergemapper to="archive.tar"/>

Source file name | Target file name
--- | ---
`A.java` | `archive.tar`
`foo/bar/B.java` | `archive.tar`
`C.properties` | `archive.tar`
`Classes/dir/dir2/A.properties` | `archive.tar`

#### glob

Both to and from are required and define patterns that may contain at most one *. For each source file that matches the from pattern, a target file name will be constructed from the to pattern by substituting the * in the to pattern with the text that matches the * in the from pattern. Source file names that don't match the from pattern will be ignored.

##### Examples

    <mapper type="glob" from="*.java" to="*.java.bak"/>
    <globmapper from="*.java" to="*.java.bak"/>

Source file name | Target file name
--- | ---
`A.java` | `A.java.bak`
`foo/bar/B.java` | `foo/bar/B.java.bak`
`C.properties` | ignored
`Classes/dir/dir2/A.properties` | ignored

    <mapper type="glob" from="C*ies" to="Q*y"/>
    <globmapper from="C*ies" to="Q*y"/>

Source file name | Target file name
--- | ---
`A.java` | ignored
`foo/bar/B.java` | ignored
`C.properties` | `Q.property`
`Classes/dir/dir2/A.properties` | `Qlasses/dir/dir2/A.property`

The `globmapper` mapper can take the following extra attributes.

Attribute | Description | Required
--- | --- | ---
casesensitive | This attribute can be true or false. If this is false, the mapper will ignore case when matching the glob pattern. Since Ant 1.6.3 | No; default is true
handledirsep | This attribute can be true or false. If this is specified, the mapper will ignore the difference between the normal directory separator characters—\ and /. This attribute is useful for cross-platform build files. Since Ant 1.6.3 | No; default is false

An example:

    <pathconvert property="x" targetos="unix">
      <path path="Aj.Java"/>
      <mapper>
      <chainedmapper>
        <flattenmapper/>
        <globmapper from="a*.java" to="*.java.bak" casesensitive="no"/>
      </chainedmapper>
      </mapper>
    </pathconvert>
    <echo>x is ${x}</echo>

will output `x is j.java.bak`, and

    <pathconvert property="x" targetos="unix">
      <path path="d/e/f/j.java"/>
      <mapper>
        <globmapper from="${basedir}\d/e\*" to="*" handledirsep="yes"/>
      </mapper>
    </pathconvert>
    <echo>x is ${x}</echo>

will output `x is f/j.java`.

#### regexp

Both to and from are required and define regular expressions. If the source file name (as a whole or in part) matches the from pattern, the target file name will be constructed from the to pattern, using `\0` to `\9` as back-references for the full match (`\0`) or the matches of the subexpressions in parentheses. The to pattern determines the whole file name, so if you wanted to replace the extension of a file you should not use `from="\.old$" to=".new"` but rather `from="(.*)\.old$" to="\1.new"` (or rather use a glob mapper in this case).

Source files not matching the from pattern will be ignored.

Note that you need to escape a dollar-sign ($) with another dollar-sign in Ant.

The regexp mapper needs a supporting library and an implementation of `org.apache.tools.ant.util.regexp.RegexpMatcher` that hides the specifics of the library. Since Ant 1.8.0, Java 1.4 or later is required, so the implementation based on the `java.util.regex` package is always be available. You can still use the now retired Jakarta ORO or Jakarta Regex instead if your provide the corresponding jar in your `CLASSPATH`.

For information about using gnu.regexp or gnu.rex with Ant, see this article. Please keep in mind that your mileage may vary with different regexp engines.

If you want to use one of the regular expression libraries other than `java.util.regex` you need to also use the corresponding `ant-[apache-oro, apache-regexp].jar` from the Ant release you are using. Make sure that both will be loaded from the same classpath, that is either put them into your `CLASSPATH`, `ANT_HOME/lib` directory or a nested `<classpath>` element of the mapper—you cannot have `ant-[apache-oro, apache-regexp].jar` in `ANT_HOME/lib` and the library in a nested `<classpath>`.

Ant will choose the regular expression library based on the following algorithm:

- If the system property `ant.regexp.matcherimpl` has been set, it is taken as the name of the class implementing `org.apache.tools.ant.util.regexp.RegexpMatcher` that should be used.
- If it has not been set, uses the JDK 1.4 classes.

##### Examples

    <mapper type="regexp" from="^(.*)\.java$$" to="\1.java.bak"/>
    <regexpmapper from="^(.*)\.java$$" to="\1.java.bak"/>

Source file name | Target file name
--- | ---
`A.java` | `A.java.bak`
`foo/bar/B.java` | `foo/bar/B.java.bak`
`C.properties` | ignored
`Classes/dir/dir2/A.properties` | ignored

    <mapper type="regexp" from="^(.*)/([^/]+)/([^/]*)$$" to="\1/\2/\2-\3"/>
    <regexpmapper from="^(.*)/([^/]+)/([^/]*)$$" to="\1/\2/\2-\3"/>

Source file name | Target file name
--- | ---
`A.java` | ignored
`foo/bar/B.java` | `foo/bar/bar-B.java`
`C.properties` | ignored
`Classes/dir/dir2/A.properties` | `Classes/dir/dir2/dir2-A.properties`

    <mapper type="regexp" from="^(.*)\.(.*)$$" to="\2.\1"/>
    <regexpmapper from="^(.*)\.(.*)$$" to="\2.\1"/>

Source file name | Target file name
--- | ---
`A.java` | `java.A`
`foo/bar/B.java` | `java.foo/bar/B`
`C.properties` | `properties.C`
`Classes/dir/dir2/A.properties` | `properties.Classes/dir/dir2/A`

    <mapper type="regexp" from="^(.*?)(\$$[^/\\\.]*)?\.class$$" to="\1.java"/>
    <regexpmapper from="^(.*?)(\$$[^/\\\.]*)?\.class$$" to="\1.java"/>

Source file name | Target file name
--- | ---
`ClassLoader.class` | `ClassLoader.java`
`java/lang/ClassLoader.class` | `java/lang/ClassLoader.java`
`java\lang\ClassLoader$1.class` | `java\lang\ClassLoader.java`
`java/lang/ClassLoader$foo$1.class` | `java/lang/ClassLoader.java`

The regexp mapper can take the following extra attributes.

Attribute | Description | Required
--- | --- | ---
casesensitive | This attribute can be true or false. If this is false, the mapper will ignore case when matching the pattern. Since Ant 1.6.3 | No; default is true
handledirsep | This attribute can be true or false. If this is specified, the mapper will treat a \ character in a filename as a / for the purposes of matching. This attribute is useful for cross-platform build files. Since Ant 1.6.3 | No; default is false

An example:

    <pathconvert property="x" targetos="unix">
      <path path="Aj.Java"/>
      <chainedmapper>
        <flattenmapper/>
        <regexpmapper from="a(.*)\.java" to="\1.java.bak" casesensitive="no"/>
      </chainedmapper>
    </pathconvert>
    <echo>x is ${x}</echo>

will output `x is j.java.bak`, and

    <pathconvert property="hd.prop" targetos="windows">
      <path path="d\e/f\j.java"/>
      <chainedmapper>
        <regexpmapper from="${basedir}/d/e/(.*)" to="\1" handledirsep="yes"/>
      </chainedmapper>
    </pathconvert>

will set `hd.prop` to `f\j.java`.

#### package

Sharing the same syntax as the glob mapper, the package mapper replaces directory separators found in the matched source pattern with dots in the target pattern placeholder. This mapper is particularly useful in combination with `<uptodate>` and `<junit>` output.

The to and from attributes are both required.

##### Example

    <mapper type="package" from="*Test.java" to="TEST-*Test.xml"/>
    <packagemapper from="*Test.java" to="TEST-*Test.xml"/>

Source file name | Target file name
--- | ---
`org/apache/tools/ant/util/PackageMapperTest.java` | `TEST-org.apache.tools.ant.util.PackageMapperTest.xml`
`org/apache/tools/ant/util/Helper.java` | ignored

#### unpackage

Since Ant 1.6.0

This mapper is the inverse of the package mapper. It replaces the dots in a package name with directory separators. This is useful for matching XML formatter results against their JUnit test test cases. The mapper shares the sample syntax as the glob mapper.

The to and from attributes are both required.

##### Example

    <mapper type="unpackage" from="TEST-*Test.xml" to="${test.src.dir}/*Test.java">
    <unpackagemapper from="TEST-*Test.xml" to="${test.src.dir}/*Test.java">

Source file name | Target file name
--- | ---
`TEST-org.acme.AcmeTest.xml` | `${test.src.dir}/org/acme/AcmeTest.java`

#### composite

Since Ant 1.7.0

This mapper implementation can contain multiple nested mappers. File mapping is performed by passing the source filename to each nested `<mapper>` in turn, returning all results. The to and from attributes are ignored.

Since Ant 1.8.0, the order of the mapped results is the same as the order of the nested mappers; prior to Ant 1.8.0 the order has been undefined.

##### Examples

    <compositemapper>
      <identitymapper/>
      <packagemapper from="*.java" to="*"/>
    </compositemapper>

Source file name | Target file names
--- | ---
`foo/bar/A.java` | `foo/bar/A.java`
`foo.bar.A`

The composite mapper has no corresponding `<mapper>` type attribute.

#### chained

Since Ant 1.7.0

This mapper implementation can contain multiple nested mappers. File mapping is performed by passing the source filename to the first nested mapper, its results to the second, and so on. The target filenames generated by the last nested mapper comprise the ultimate results of the mapping operation. The to and from attributes are ignored.

##### Examples

    <chainedmapper>
      <flattenmapper/>
      <globmapper from="*" to="new/path/*"/>
      <mapper>
        <globmapper from="*" to="*1"/>
        <globmapper from="*" to="*2"/>
      </mapper>
    </chainedmapper>

Source file name | Target file names
--- | ---
`foo/bar/A.java` | `new/path/A.java1`
`new/path/A.java2`
`boo/far/B.java` | `new/path/B.java1`
`new/path/B.java2`

The chained mapper has no corresponding `<mapper>` type attribute.

#### filtermapper

Since Ant 1.6.3

This mapper implementation applies a filterchain to the source file name.

##### Examples

    <filtermapper>
      <replacestring from="\" to="/"/>
    </filtermapper>

Source file name | Target file names
--- | ---
`foo\bar\A.java` | `foo/bar/A.java`

    <filtermapper>
      <scriptfilter language="beanshell">
        self.setToken(self.getToken().toUpperCase());
      </scriptfilter>
    </filtermapper>

Source file name | Target file names
--- | ---
`foo\bar\A.java` | `FOO\BAR\A.JAVA`

The filtermapper has no corresponding `<mapper>` type attribute.

#### scriptmapper

Since Ant 1.7

This mapper executes a script written in Apache BSF or JSR 223 supported language, once per file to map.

The script can be declared inline or in a specified file.

See the Script task for an explanation of scripts and dependencies.

Attribute | Description | Required
--- | --- | ---
language | Scripting language | Yes
manager | The script engine manager to use. See the script task for using this attribute. | No; default is auto
src | File containing the script | No
encoding | The encoding of the script as a file. Since Ant 1.10.2 | No; defaults to default JVM character encoding
setbeans | whether to have all properties, references and targets as global variables in the script. Since Ant 1.8.0 | No; default is true
classpath | The classpath to pass into the script. | No
classpathref | The classpath to use, given as a reference to a path defined elsewhere. | No

This filename mapper can take a nested `<classpath>` element. See the script task on how to use this element.

##### Example

    <scriptmapper language="javascript">
      self.addMappedName(source.toUpperCase());
      self.addMappedName(source.toLowerCase());
    </scriptmapper>

Source file name | Target file names
--- | ---
`foo\bar\A.java` | `FOO\BAR\A.JAVA`
`foo\bar\a.java`

To use this mapper, the scripts need access to the source file, and the ability to return multiple mappings. Here are the relevant beans and their methods. The script is called once for every source file, with the list of mapped names reset after every invocation.

Script bean | Description
--- | ---
`source: String` | The file/path to map
`self` | The scriptmapper itself
`self.addMappedName(String name)` | Add a new mapping
`self.clear()` | Reset the list of files

The scriptmapper has no corresponding `<mapper>` type attribute.

#### firstmatchmapper

Since Ant 1.8.0

This mapper supports an arbitrary number of nested mappers and returns the results of the first mapper that matches. This is different from composite mapper which collects the results of all matching children.

##### Examples

    <firstmatchmapper>
      <globmapper from="*.txt" to="*.bak"/>
      <globmapper from="*A.*" to="*B.*"/>
    </firstmatchmapper>

Source file name | Target file names
--- | ---
`foo/bar/A.txt` | `foo/bar/A.bak`
`foo/bar/A.java` | `foo/bar/B.java`

The firstmatchmapper has no corresponding `<mapper>` type attribute.

#### cutdirsmapper

Since Ant 1.8.2

This mapper strips a configured number of leading directories from the source file name.

##### Examples

    <cutdirsmapper dirs="1"/>

Source file name | Target file names
--- | ---
`foo/bar/A.txt` | `bar/A.txt`

The cutdirsmapper has no corresponding `<mapper>` type attribute.

Attribute | Description | Required
--- | --- | ---
dirs | Number of directories to strip (must be a positive number). | Yes