Plugins.md

# Task Plugins #

The *Task* entities defined in a *Processor* definition can be implemented as dedicated native java plugins or as scripts written in *Perl*, *Python* or *Shell* scripting languages.


## Java plugins

Dedicated native java plugins can be developed by implementing the GenericTaskInterface process method defined in the DES library

**GenericTaskInterface Interface**

```java
public interface GenericTaskInterface {

	/**
	 * 
	 * @param basepath Basepath as configured in DistributionServer.ini
	 * @param aoi_name AOI name contained in the $processor.processor_config.xml
	 * @param processor_name Processor name related to the $processor.processor_config.xml
	 * @param entity_name Name of executing entity (Task, Consumer, etc.)
	 * @param parameters Parameters as defined by <Parameter>
	 * @param args List of arguments of the Task (String or Hashtables, to be checked by the plugin)
	 * @param files List of files of the Task iff <FileType>regexp</FileType> is defined, else null
	 * @return ExitCodes
	 */
	public int process(String basepath, String aoi_name,
			String processor_name, String entity_name, Hashtable parameters, Object[] args, String[] files);
	
}
```

The implemented plugin should be packaged as a jar file and placed in the DES ./plugins directory where it is automatically loaded at Runtime.

The plugin can be executed in a given *Processor* *Task* with the following definition:

Example:
```xml
<Task name="renameFiles" type="class" active="yes" priority="NORM">
	<Command>class</Command>
	<FileType>SAMPLE.*.AA.txt</FileType>
	<Parameter>edu.eurac.distributionserver.tasks.generic.FileRename</Parameter>
	<FilePrefix>RENAME</FilePrefix>
</Task>
```

The parameters can be passed to the *Task* plugin with one of the following options:
    
1) By using a custom keyword tag eg. *FilePrefix* in the *Task* definition and then accessing the parameter with the Hashtable parameters in the Interface
    
```java
    String file_prefix = (String)parameters.get("FilePrefix");
```
    
2) By using the *Parameter* tag in the *Task* definition and than referencing the parameter with the Object[] args type in the Interface
    
```java
    String classname = (String)args[1];
```
Note: Note: args[0] is the class name