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My first Java HIPE task

This tutorial will teach you the following:

1. How to write a simple Java task in Eclipse.
2. How to include the task in HIPE.

Requisites:

• You know at least the basics of Java and are familiar with concepts such as package, class and superclass.
• You have read the Getting started with HIPE development tutorial.

Writing the task in Eclipse

Start Eclipse. Choose File --> New --> Java Project. Enter DoesNotDoMuch in the Project name field. Click Next.

In the next window, click on the Libraries tab. Click Add Library. The Add Library dialogue window appears. Select HCSS Project Container from the list and click Next. If you do not see HCSS Project Container among the available libraries, you need to install the HCSS Project plugin as described in the Getting started with HIPE development tutorial.

In the configuration dialogue window for the HCSS Project Container library, enter hcss.dp.core in the Project field, the major version number of your HIPE installation in the Track field (3.0 for HIPE 3.x, and so on), and click Fetch latest to get the latest build. These settings work for the simple example in this tutorial; if you are developing instrument-specific software, set the Project field as hcss.dp.hifi, hcss.dp.pacs or hcss.dp.spire.

Click Finish, then Finish again in the New Java Project dialogue window.

Right click on the project name in the Package Explorer view, and choose New --> Class from the context menu. The New Java Class dialogue window appears. Write herschel.ia.doesnotdomuch in the Package field, and DoesNotDoMuchTask in the Name field. In the Superclass field, change java.lang.Object to herschel.ia.task.Task.

Click Finish. Eclipse creates the class and opens the source file with the skeleton code:

package herschel.ia.doesnotdomuch;

import herschel.ia.task.Task;

public class DoesNotDoMuchTask extends Task {

}

Complete the source code as follows:

package herschel.ia.doesnotdomuch;

import herschel.ia.gui.kernel.util.PopupDialog;
import herschel.ia.task.Task;
import herschel.ia.task.TaskParameter;

public class DoesNotDoMuchTask extends Task {
    private static final long serialVersionUID = 1L;

    public DoesNotDoMuchTask() {
   
   TaskParameter parameter = new TaskParameter("input", String.class);
        parameter.setDefaultValue("nothing");
        parameter.setDescription("You can write anything.");
        addTaskParameter(parameter);
    }
    
    public void execute() {
   PopupDialog.showInfo("You wrote \"" + getParameter("input").getValue() + "\".");
    }

}

Save the file. Right click on the project name, and choose Export from the context menu. Choose JAR File from the list and click Next. Write a name of your liking in the JAR file field and click Finish. Eclipse creates the JAR file.

Including the task in HIPE

Create a Jython file, named for example doesnotdomuch.py (but it can be any other name). It does not matter where you create the file. Write the following in the file:

from herschel.ia.doesnotdomuch import DoesNotDoMuchTask

from herschel.ia.task.views import TaskToolRegistry
from herschel.ia.gui.kernel.Tool import Category

print "Importing DoesNotDoMuch..."

doesNotDoMuch = DoesNotDoMuchTask()

toolRegistry = TaskToolRegistry.getInstance()
toolRegistry.register(doesNotDoMuch, [Category.SPECTRUM, Category.GENERAL])
del(toolRegistry)

This is the file HIPE is going to use to import the new task. Note these two points:

• The print statement is not required, but it is useful to make sure that the task is being imported. It should be among the first statements written to the console when you start HIPE.
• The task is assigned to the GENERAL and SPECTRUM categories. Again, this is not required. The task would appear anyway in the All folder of the Tasks view in HIPE. The available categories are GENERAL, CUBE, IMAGE, SPECTRUM, HIFI, PACS and SPIRE.

Open the installed.userlibraries file in your HIPE installation directory. Add the following line as the first of the line beginning with <archive path:

<archive path="/path/to/jar/file/doesnotdomuch.jar"/>

Of course you have to substitute the correct path and name for the JAR file you created before.

Now go to the .hcss directory, which should be within your home directory. Open the file hipe.props, or create it if it does not exist. Add the following line:

hcss.interpreter.imports = { /path/to/py/file/doesnotdomuch.py }

Again, change the path and the file name to the correct values. If the hcss.interpreter.imports is already defined in hipe.props, or in another file such as hcss.props, add the new value after a comma within the braces:

hcss.interpreter.imports = { /path/to/other/file/alreadythere.py, /path/to/py/file/doesnotdomuch.py }

Now start HIPE. You should see the Importing DoesNotDoMuch... in the console, and the doesNotDoMuch task should appear in the All, General and Spectrum folders in the Tasks view.

Please add your comments!