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Developing a Writer Developing a Writer

Writers

To create a writer plugin implement the ProductWriterPlugIn interface.



public interface ProductWriterPlugIn extends ProductIOPlugIn {

    /**
     * Returns an array containing the classes that represent valid output types for this writer.
     * Instances of the classes returned in this array are valid objects for the setOutput method of the
     * ProductWriter interface (the method will not throw an InvalidArgumentException in this case).
     *
     * @return an array containing valid output types, never null
     */
    Class[] getOutputTypes();

    /**
     * Creates an instance of the actual product writer class. This method should never return null.
     *
     * @return a new writer instance, never null
     */
    ProductWriter createWriterInstance();
}

The writer plugin should create a new instance of your reader in createWriterInstance().



To create a writer implementation, extend the AbstractProductWriter. In writeProductNodesImpl(), write your data files.



WriteBandRasterData() writes raster data from the given in-memory source buffer into the data sink specified by the given source band and region.



Maven DataIO Archetype

The Maven 2 Archetype Plugin for NEST data I/O modules is used to create archetypes for NEST data I/O modules.



A Maven Archetype is a template toolkit for generating a new module package. By using the Maven Archetype you can create a module structure easily and get started adding your code to the module.



A DataIO Archetype will generate a product reader and writer within the same package.


Before beginning, make sure that you have built the NEST source code and do a

maven install

to ensure that all dependencies are in the repository.



From the command line type the following from the NEST source code root folder.:



mvn archetype:create

-DarchetypeGroupId=org.esa.nest.maven

-DarchetypeArtifactId=maven-nest-dataio-archetype

-DarchetypeVersion=1.0

-DgroupId=myGroupId

-DartifactId=myArtifactId

-Dversion=myVersion

-DpackageName=myPackageName

where

  • myGroupId will become the groupId of the generated POM
  • myArtifactId will become the artifactId of the generated POM and the NEST module's symbolicName.
  • myVersion will become the version of the generated POM and NEST module. Defaults to 1.0-SNAPSHOT.
  • myPackageName will become the source package name. Defaults to the value of myGroupId
    .

Please also refer to the documentation of the Maven 2 Archetype Plugin.

Example

mvn archetype:create
-DarchetypeGroupId=org.esa.nest.maven -DarchetypeArtifactId=maven-nest-dataio-archetype
-DarchetypeVersion=1.0
-DgroupId=org.esa.nest -DartifactId=nest-sar-io

Publishing a Writer

Writer implementations are published via the Java service provider interface (SPI). A JAR publishes its writers in the resource file

META-INF/services/

org.esa.beam.framework.dataio.ProductWriterPlugIn. In this file add your writer SPI eg: org.esa.beam.dataio.geotiff.GeoTiffProductWriterPlugIn


Adding Menu Item Actions

In the modules.xml file found in the resources folder of the package, add an Action to create a menu item in the DAT. State the class of the Action to be called and the text to show in the menu item.  



        <action>


            <id>exportGeoTIFFProduct</id>


            <class>org.esa.beam.dataio.geotiff.GeoTiffExportAction</class>


            <formatName>GeoTIFF</formatName>


            <useAllFileFilter>true</useAllFileFilter>


            <mnemonic>O</mnemonic>


            <text>Export GeoTIFF Product...</text>


            <shortDescr>Export a GeoTIFF data product or subset.</shortDescr>


            <description>Export a GeoTIFF data product or product subset.</description>


            <helpId>exportGeoTIFFProduct</helpId>


        </action>


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