Standalone Tool Adapter

Operator structure

Simply put, an adapter operator has the following folder structure:

ADAPTER_FOLDER

META-INF
- MANIFEST.MF
- descriptor.xml
org
- esa
  - snap
    - ui
      - tooladapter
        layer.xml
    - utils
      - ModuleInstaller.class
adapter-template.vm
version.txt

This folder should be copied in the location defined by user.module.path property in the configuration file snap.properties

Quick Overview

This is a listing of the elements directly under the descriptor's operator root element:

XML Element	Required	Description
Operator descriptive parameters
name	Yes	The name of the adapter. Must be unique among the set of adapters. Sample value: org.esa.snap.core.gpf.operators.tooladapter.MyAdapter
operatorClass	Yes	The implementing Java class. It is always org.esa.snap.core.gpf.operators.tooladapter.ToolAdapterOp
alias	Yes	The alias of the adapter. This is should be the same as the name of the adapter folder. Sample value: MyAdapter
label	Yes	The tag of the adapter. This will be used for creating the menu action for the adapter. Sample value: My Adapter
version	No	The version of the adapter. Even though it is not mandatory, it is recommended to set it to a value. Sample value: 1.0.0
description	No	Descriptive text for the adapter. Sample value: This is my first adapter
authors	No	The author(s) of the adapter. Sample value: John Doe
copyright	No	Any copyright information of the adapter. Sample value: (C)2015 Zulu
internal	No	Not used Possible values: true, false
autoWriteSuppressed	No	Not used Possible values: true, false
menuLocation	Yes	The menu path, in SNAP Desktop, where the action for the adapter will be placed. Value must be a valid NetBeans path. Sample value: Menu/Tools/External Tools
source	Yes	Specifies if the adapter comes from a NBM module, or is created by the user. Possible values: user, package
isHandlingOutputName	No	Specifies if the tool handles the output product name by itself. If false, targetProductFile has to be provided at execution time. Possible values: true, false
isSystem	No	Deprecated. Possible values: true, false
Pre-processing parameters
preprocessTool	Yes	Specifies if the adapter should execute another operator before its execution. Possible values: false, true
writeForProcessing	Yes	Specifies if the input product of the adapter should be converted to another format before execution. Possible values: false, true
processingWriter	Yes	Specifies to what format the input product of the adapter should be converted to. Possible values: BEAM-DIMAP, CSV, ENVI, GeoTIFF, GeoTIFF-BigTIFF, HDF5, NetCDF-BEAM, NetCDF-CF, NetCDF4-BEAM, NetCDF4-CF
Execution parameters
mainToolFileLocation	Yes	The path to the tool executable. Variables defined in the variables section can be used. Sample values: C:\ToolBin\tool.exe, /usr/var/tool/bin/tool, $TOOL_PATH/$TOOL_BINARY
workingDir	Yes	The working directory. Variables defined in the variables section can be used. Sample values: C:\ToolBin\SomeFolder, /usr/var/wdir, $WORK_DIR
template	Yes	The path of the main Velocity template file, relative to the adapter folder. Should be on the same level as the META-INF directory. Sample value: MyAdapter-template.vm
progressPattern	No	If specified, the regular expression to capture the progress from the tool output stream. Sample value: (?:.+): (\d{1,3})% (?:.+)
errorPattern	No	If specified, the regular expression to capture tool errors from its output stream. Sample value: ERROR: (.+)
numSourceProducts	Yes	The number of input source products. This is to be set in conjuction with the number of DefaultSourceProductDescriptor elements. Sample value: 1
System variables
variables	No	See variables section.
Operator parameters
parameters	Yes	See parameters section.

Variables Section

The element variables has one or more child elements variable (simple values) or osvariable (platform-dependent values):

XML Element Required Description

variable

key Yes The variable key (or name). This value can be used as indicated above by prefixing the key with $
Sample value: BIN_PATH

value Yes The variable value. If the variable represents an OS environment variable, the value element can be empty (the OS value will be read at run-time).
Sample value: /usr/var/tool/bin

osvariable

key Yes The variable key (or name). This value can be used as indicated above by prefixing the key with $
Sample value: BIN_PATH

windows Yes The Windows-specific value.
Sample value: C:\Program Files\Tool\bin

linux Yes The Linux-specific value.
Sample value: /usr/var/tool/bin

macosx Yes The Mac OSX-specific value. May be similar to the Linux one.
Sample value: /usr/var/tool/bin

XML Element	Required	Description
variable
key	Yes	The variable key (or name). This value can be used as indicated above by prefixing the key with $ Sample value: BIN_PATH
value	Yes	The variable value. If the variable represents an OS environment variable, the value element can be empty (the OS value will be read at run-time). Sample value: /usr/var/tool/bin
osvariable
key	Yes	The variable key (or name). This value can be used as indicated above by prefixing the key with $ Sample value: BIN_PATH
windows	Yes	The Windows-specific value. Sample value: C:\Program Files\Tool\bin
linux	Yes	The Linux-specific value. Sample value: /usr/var/tool/bin
macosx	Yes	The Mac OSX-specific value. May be similar to the Linux one. Sample value: /usr/var/tool/bin

Parameters Section

The element variables has one or more child elements parameter with the following structure:

XML Element	Required	Description
name	Yes	The parameter name. This value can be used in templates by prefixing the key with $ Sample value: inputFile
alias	No	The parameter alias. Sample value: in
alias	No	The parameter alias. In a future version this will be the command line flag of the parameter. Sample value: in
dataType	Yes	The parameter type. Can be one of the following: Boolean: defaultValue may be true or false Integer: defaultValue may be an integer Decimal: defaultValue may be a float String: defaultValue may be a text value File: defaultValue may be a File object List: defaultValue may be list of string values TemplateBeforeExecution: defaultValue should be the name of the before-execution Velocity template TemplateAfterExecution: defaultValue should be the name of the after-execution Velocity template
defaultValue	No	The parameter default value. Sample value: see the above element.
valueSet	No	For all types except File or List, this specifies the set of accepted values for the parameter. The values are specified by string child elements. Example: for an Integer data type, the valueSet elements would have the children: < string>1< /string>< string>2< /string>< string>3< /string>
notNull	Yes	Specifies if the parameter's defaultValue can be null. Possible values: true or false
notEmpty	Yes	Specifies if the parameter's defaultValue can be empty. Possible values: true or false
parameterType	Yes	Specifies the type of the parameter. Possible values: RegularParameter, FolderParameter, TemplateParameter, TemplateBeforeExecution, TemplateAfterExecution

Source Products Descriptors section

The element sourceProductDescriptors has one or more child elements org.esa.snap.core.gpf.descriptor.DefaultSourceProductDescriptor with the following structure:

XML Element	Required	Description
name	Yes	The conventional name of the source product name. The convention is sourceProduct.n where n is the product number Sample value: sourceProduct.1

Please remember that the number of org.esa.snap.core.gpf.descriptor.DefaultSourceProductDescriptor elements should match the value of the numSourceProducts element