## Typedef

### Description

Adds a task or a data type definition to the current project such that this new type or task can be used in the current project.

Tasks are any class that extend org.apache.tools.ant.Task or a class that is adapted to a Task using an adapter class.

Data types are things like paths or filesets that can be defined at the project level and referenced via their ID attribute. Custom data types usually need custom tasks to put them to good use.

Two attributes are needed to make a definition, the name that identifies this data type uniquely, and the full name of the class (including the packages) that implements this type.

You can also define a group of definitions at once using the file or resource attributes. These attributes point to files in the format of Java property files or an xml format.

For property files each line defines a single data type in the format:

        typename=fully.qualified.java.classname

The xml format is described in the Antlib section.

### Parameters

Attribute | Description | Required
name | the name of the data type | Yes, unless the file or resource type attributes have been specified.
classname | the full class name implementing the data type | Yes, unless file or resource have been specified.
file | Name of the file to load definitions from. | No
resource | Name of the resource to load definitions from. If there is multiple resources of this name in the classpath, and the format is "properties", the first resource will be loaded, otherwise all the resources will be loaded. | No
format | The format of the file or resource. The values are "properties" or "xml". If the value is "properties" the file/resource is a property file contains name to classname pairs. If the value is "xml", the file/resource is an xml file/resource structured according to Antlib. The default is "properties" unless the file/resorce name ends with ".xml", in which case the format attribute will have the value "xml". (introduced in ant1.6) | No
classpath | the classpath to use when looking up `classname`. | No
loaderRef | the name of the loader that is used to load the class, constructed from the specified classpath. Use this to allow multiple tasks/types to be loaded with the same loader, so they can call each other. ( introduced in ant1.5 ) | No
onerror | The action to take if there was a failure in defining the type. The values are fail - cause a build exception, report, output a warning, but continue, ignore, do nothing. The default is fail. (introduced in ant1.6) | No
adapter | A class that is used to adapt the defined class to another interface/class. The adapter class must implement the interface "org.apache.tools.ant.TypeAdapter". The adapter class will be used to wrap the defined class unless the defined class implements/extends the class defined by the attribute "adaptto". If "adaptto" is not set, the defined class will always be wrapped. (introduced in ant1.6) | No
adaptto | This attribute is used in conjunction with the adapter attribute. If the defined class does not implement/extend the interface/class specified by this attribute, the adaptor class will be used to wrap the class. (introduced in ant1.6) | No
uri | The uri that this definition should live in. since Ant1.6 | No

### Parameters specified as nested elements

#### classpath

`Typedef`'s classpath attribute is a PATH like structure and can also be set via a nested classpath element.

### Examples

The following fragment defines define a type called urlset.

        <typedef name="urlset" classname="com.mydomain.URLSet"/>

The data type is now availabe to Ant. The class `com.mydomain.URLSet` implements this type.

Assuming a class org.acme.ant.RunnableAdapter that extends Task and implements org.apache.tools.ant.TypeAdapter, and in the execute method invokes run on the proxied object, one may use a Runnable class as an Ant task. The following fragment defines a task called runclock.

        <typedef name="runclock"
                 classname="com.acme.ant.RunClock"
                 adapter="org.acme.ant.RunnableAdapter"/>

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