This Snap executes a Javascript, Python, or Ruby script using the JVM ScriptEngine mechanism. After selecting your language of choice, click the Edit Script button to open the script editor. By default, the editor will be populated with a skeleton script that you can modify. The skeleton simply reads an input document, wraps it in a map and writes the wrapper to the output view. If a script file is present in the SLDB, it can be uploaded to the Snap by using the Script file property; this property also accepts Pipeline parameters and upstream parameters. 

The document data can convert to and from the JSON data interchange language. By convention, the root of every document is conceptually a JSON object -- a collection of name/value pairs, where each name is a string and each value is an object, an array, a string, a number, a boolean, or a null. Every modern programming language has a corresponding type for this concept:

When you are writing a script for the Script Snap, each input document is an object that implements the Java Map interface, and can be accessed as an instance of the scripting language’s native object class; for example, as a Python dictionary.

To write an output document, your script must create a new object. In Python or Ruby, you can create an instance of the required language’s native object type, a Python dictionary or a Ruby hash. The values you add to these objects must be one of the JSON-compatible types including objects, arrays, strings, numbers, booleans. For an array, you can use the corresponding array or list type of the language. Objects written to the output view should be of Java types. This is required by some downstream Snaps. For example, the Join Snap. To write a Python map to the output view in a Python script, convert the map to a Java HashMap

General Instructions for All Scripting Languages

The script author should declare a global variable named 'hook' (note that this variable name is case sensitive). The Script engine makes the following four global variables available to the script as defined in the Script#ScriptHook Interface section:

• Variable input is of type ScriptHook.Input
• Variable output is of type ScriptHook.Output
• Variable error is of type ScriptHook.Error
• Variable log is of type org.slf4j.Logger

Type defined in the schema maps to the Java class per the following:

Modes

• Ultra pipelines: Works in Ultra Pipelines if you pass the original document to the write() method for the output view. For example, in the JavaScript template, the body of the loop is per the following: 

  Note the two arguments to the output.write() method. The first argument is the input document -- doc. The second argument is the data for the output document -- wrapper. Both the arguments are needed so that the lineage of the output document can be tied to the input document. This is especially important for an Ultra pipeline responding to web requests. The initial request becomes an input document to the first Snap in the SnapLogic Pipeline, eventually resulting in an output document from the last Snap in the Pipeline. The Pipeline must maintain the lineage of each document so that each response can be correlated to the request that generated it.

For JavaScript, objects written to the output view should be composed of serializable Java types. This is required by some downstream Snaps such as the Copy Snap. To write out a map to the output view in a JavaScript script, use a Java Map implementation, such as HashMap or LinkedHashMap per the following:

Required. The name for the Snap. You can modify this to be more specific, especially if you have more than one of the same Snap in your pipeline.

A script file that implements the ScriptHook interface. This field can be used if the script file is present in the SLDB. Click on the 'browse' icon to select the required script file from the SLDB. 

Example: transform.py

Default value: [None]

Required. This property enables you to edit a script within the Snap instead of through an external file. From this page, you can export the script to a file in a project, import a script, or generate a template for the selected Scripting Language.

Default value: A skeleton for the chosen scripting language.  You can click the Generate Template button to regenerate the skeleton.

Select one of the three modes in which the Snap executes. Available options are:

• Validate & Execute: Performs limited execution of the Snap, and generates a data preview during Pipeline validation. Subsequently, performs full execution of the Snap (unlimited records) during Pipeline runtime.
• Execute only: Performs full execution of the Snap during Pipeline execution without generating preview data.

• Disabled: Disables the Snap and all Snaps that are downstream from it.