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Overview

The You can use the Script Snap executes a to execute Javascript, Python, or Ruby script scripts using the JVM ScriptEngine mechanism. Accounts are not required to work with this Snap.

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Snap Type

The Script Snap is a Write write-type Snap.

Support for Ultra Pipelines

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For JavaScript, objects written to the output view should be composed of serializable Java types. This is required by some Some downstream Snaps, such as the Copy Snap, require this. 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:

importClass(java.util.LinkedHashMap);
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var inDoc = this.input.next();
var outDoc = new LinkedHashMap();
outDoc.put("original", inDoc);
this.output.write(inDoc, outDoc);

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To implement Python in the Script Snap, we use Jython. We recently have upgraded the Jython engine from version 2.7-b3 (a beta version from 2014) to the current version , 2.7.2(March , 2020). The following are the resultant issues and workarounds that we are suggesting:

• There's an An open bug in 2.7 that introduced a backward-incompatible change in the SnapLogic platform wherein the Jython engine automatically converts BigInteger values to primitive long values. This impacts all your scripts that perform numeric manipulation of integer values from documents (SnapLogic uses the BigInteger type to represent integers in documents). Your Pipelines pipelines and Snaps with the Script Snap (or the deprecated Execute Script Snap) that use numeric manipulation scripts with integer or BigInteger data type may fail during execution. We recommend you to prospectively replace integer or BigInteger values with long values.

  Example:
  sum = a.intValue() + b.intValue()
  Here Here, a and b are of BigInteger type that now fail as Jython 2.7.2 automatically and transparently calls longValue() on any BigInteger value it encounters. So a and b would need to use the long and not BigInteger type.

  The known fix is to rewrite the above calculation as sum = a + b by removing occurrences of .intValue() or .longValue() from your Python scripts. 

• Before the 4.22 release (August 2020), when using the Script Snap with the Scripting language option selected as Python, requesting a key that did not exist in a dictionary (for example, my_dict['missing_key']) would return None. Starting from the 4.22 release, the same request now returns a KeyError exception. If you need to continue returning None, use the .get(key) method instead (for example, my_dict.get['missing_key']).

• - zlib.compress():
 The zlib library compresses the JSON files retrieved from the SnapLogic APIs and backs-up Pipelines and accounts to a database. The following Python code, when trying to compress displays an ascii … ordinal not in range(128) error.
  Original code: in_doc["json"] = zlib.compress(in_doc["json"])
  Fix: in_doc["json"] = zlib.compress(in_doc["json"].encode("utf-8"))

• {dictionary}.values().toArray()[i]:
 Prior to 
Before the 4.22 release (August 2020), to subscript a {dictionary}.values() method, you had to append the toArray() method to values(); else, you would see the Failure: ‘java.util.LinkedHashMap$LinkedValues’ object is unsubscriptable error. After the 4.22 release, toArray() returns Failure: ‘list’ object has no attribute ‘toArray’. However, the requirement for toArray() is no longer necessary for the subscript.
  Original code: sLine = data.values().toArray()[0]
  Fix: sLine = data.values()[0]

Additional Information

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:

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Snap Views

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Type

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Format

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Number of Views

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Examples of Upstream and Downstream Snaps

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Description

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Input 

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Document

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• Min: 1

• Max: 1

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• Mapper

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This Snap has at most one document input view.

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Output

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Document

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• Min: 1

• Max: 1

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• Mapper

• Copy

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This Snap has at most one document output view. 

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Error

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Error handling is a generic way to handle errors without losing data or failing the Snap execution. You can handle the errors that the Snap might encounter when running the pipeline by choosing one of the following options from the When errors occur list under the Views tab:

• Stop pipeline Execution: Stops the current pipeline execution if the Snap encounters an error.

• Discard Error Data and Continue: Ignores the error, discards that record, and continues with the remaining records.

• Route Error Data to Error View: Routes the error data to an error view without stopping the Snap execution.

Learn more about Error handling in Pipelines.

Snap Settings

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Field

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Description

Label*

Default Value: Script
Example: Script

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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.

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Scripting Language:

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Required. Language in which the script is provided. The options available include:

• Javascript

• Python

• Ruby

Example: Javascript
Default value: Javascript

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Script file:

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]

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Edit Script:

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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.

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ScriptHook Interface

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Snap Views

Snap Settings

ScriptHook Interface

package com.snaplogic.scripting.language;

import java.util.Iterator;

/**
 * ScriptHook is the interface that should be implemented as a callback mechanism for
 * ExecuteScript snap to call into the script.
*/

public interface ScriptHook {

    /**
     * Scripts should implement this method to provide application logic.
     */
    void execute();

    /**
     * Scripts should implement this method to cleanup any resources allocated in execute().
     */
    void cleanup();

    /**
     * Input is interface that is used by the script to read input from the snap's input view.
     */
    interface Input extends Iterator<Object> {
    }

    /**
     * Output is interface that is used by the script to send output data to the snap output view.
     */
    interface Output {

        /**
         * Write the data to the snap output.
         *
         * @param data
         */
        void write(Object data);

        /**
         * Write the data that was generated for the given incoming data to the snap output.
         * This method carries the lineage data forward.
         *
         * @param incomingData
         * @param data
         */
        void write(Object incomingData, Object data);
    }

    /**
     * Error is interface that is used by the script to send error data to snap error view.
     */
    interface Error extends Output {
    }
}

Importing Third-Party Libraries

While SnapLogic does not support importing third-party libraries directly using the Script Snap, you can add their package/JAR files in a directory in your Groundplex nodes and then import them using this Snap. For example, consider that you have added the JAR file, mongo-java-driver-3.12.7.jar, in the directory /opt/snaplogic/ext_jar/. For your Python scripts to be able to use this library, create a file named .jython in the home directory of the user running the JCC process. The .jython file should specify a value for the python.path, as follows:

python.path=/opt/snaplogic/ext_jar/mongo-java-driver-3.12.7.jar

Here’s an example of Python script that imports and uses code from this library. Use the cleanup method to ensure that the mongoClient object is appropriately closed.

from com.snaplogic.scripting.language import ScriptHook
from com.mongodb.client import MongoClients

class TransformScript(ScriptHook):
    def __init__(self, input, output, error, log):
        self.input = input
        self.output = output
        self.error = error
        self.log = log

    def execute(self):
        try:
            self.mongoClient = MongoClients.create("mongodb://localhost:27017/?readPreference=primary&ssl=false")
         

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   for d 

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in self.mongoClient.listDatabases():
 

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 self.output.write(d)
        except 

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Exception as e:
            errDoc = {

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    'error' : str(e.args)
   

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       }
  

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 self.error.write(

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errDoc)

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   def cleanup(self):

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  self.mongoClient.close()

hook = 

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Importing Third Party Libraries

While SnapLogic does not support importing third party libraries directly using the Script Snap, you can add their package/JAR files in a directory in your Groundplex nodes and then import them using this Snap.

For example, consider that you have added the JAR file, mongo-java-driver-3.12.7.jar, in the directory /opt/snaplogic/ext_jar/. For your Python scripts to be able to use this library, create a file named .jython in the home directory of the user running the JCC process. The .jython file should specify a value for python.path, as follows:

python.path=/opt/snaplogic/ext_jar/mongo-java-driver-3.12.7.jar

Here’s an example Python script that imports and uses code from this library. Note the use of the cleanup method to ensure that the mongoClient object is closed properly.

from com.snaplogic.scripting.language import ScriptHook
from com.mongodb.client import MongoClients

class TransformScript(ScriptHook):
    def __init__(self, input, output, error, log):
        self.input = input
        self.output = output
        self.error = error
        self.log = log

    def execute(self):
        try:
            self.mongoClient = MongoClients.create("mongodb://localhost:27017/?readPreference=primary&ssl=false")
            for d in self.mongoClient.listDatabases():
                self.output.write(d)
        except Exception as e:
            errDoc = {
                'error' : str(e.args)
            }
            self.error.write(errDoc)

    def cleanup(self):
        self.mongoClient.close()

hook = TransformScript(input, output, error, log)

TransformScript(input, output, error, log)

Additional Information

The document data can be converted 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 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, such 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, and booleans. You can use the corresponding array or list type of the language for an array. Objects written to the output view should be of Java types. Some downstream Snaps require this, 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:

• The variable input is of type ScriptHook.Input

• The variable output is of type ScriptHook.Output

• The variable error is of type ScriptHook.Error

• The variable log is of type org.slf4j.Logger

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

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Example Scripts

JavaScript

script = {
   execute : function() {
       var fruits = ["apple", "banana", "cherry"]
       var map = {"fruits" : fruits}
       output.write(map)
   }
}
var hook = new com.snaplogic.scripting.language.ScriptHook(script)

Python

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This example requires an input view be defined in order for it to work.

Paste code macro
language python
from com.snaplogic.scripting.language import ScriptHook from com.snaplogic.scripting.language.ScriptHook import * class TransformScript(ScriptHook): def __init__(self, input, output, error, log): self.input = input self.output = output self.error = error self.log = log def execute(self): self.log.info("Executing Transform script") while self.input.hasNext(): data = self.input.next() data["firstLast"] = "%s-%s" %(data["first"],data["last"]) data["firstLast2"] = data["first"] + data["last"] data["numberMath"] = data["counter"] + 22 data["numberMath2"] = data["counter"] + 23 data["dateMonthPlusOne"] = data["birthday"].plusMonths(1) data["numberMathType"] = type(data["counter"]) data["dateType"] = type(data["birthday"]) try: data["mathTryCatch"] = data["counter2"] + 33 self.output.write(data) except Exception as e: data["errorMessage"] = e.message self.error.write(data) self.log.info("Finished executing the Transform script") hook = TransformScript(input, output, error, log)

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Script Snap Configuration Using Python, JS Script, and Ruby Script 

The following pipeline is a demonstration of demonstrates the Script Snap using all three supported languages. In this This pipeline uses a simple JSON file with information like First Name, Last Name, and Birthday are passed to the Script Snaps.

The following is a snapshot of the input for the Script Snap:

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Python Script

Script Snap uses the Jython engine to execute the scripts written in Python. 

from com.snaplogic.scripting.language import ScriptHook
from random import randint
from time import sleep
 
class TransformScript(ScriptHook):
   def __init__(self, input, output, error, log):
       self.input = input
       self.output = output
       self.error = error
       self.log = log
   def execute(self):
       self.log.info("Executing Transform script")
       i = 1
       while self.input.hasNext():
           data = self.input.next()
           sleep(randint(1,10))
           map = {"out": data}
           self.output.write(map)
       self.log.info("Finished executing the Transform script")
hook = TransformScript(input, output, error, log)

JavaScriptJava Script

The Script Snap uses the Nashorn engine to execute the scripts written in JavaScript.

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The exported Pipeline pipeline is available in the Script#Downloads section below.

Script Snap Execution Using Pipeline

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Parameters

The following example demonstrates the execution of the Script Snap also accepts using the pipeline parameters, ; the script file in the SLDB can be is passed as a Pipeline parameter. The pipeline demonstrated above is modified to accept pipeline parameters in this example by configuring the Script file property. For the scripts to be passed as a pipeline parameter, the script file should be present in the project folder in SnapLogic. Confirm in the Files section inside the Manager that  that the script files are present, ; if they are not then , upload them by clicking on the '+' icon.

In this example, there are three files, one for each type of scripting language supported: 

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Below is a snapshot of the Pipelinepipeline's properties with the and configured pipeline parameters also configured.

The individual Script Snaps are configured as shown below:

 Image Removed

Image Added

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Image Added

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Image Added

As in the example above, this pipeline also produces the same output upon execution. The exported Pipeline pipeline and sample script files used are available as a zip file in the Downloads section below.

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