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51Degrees API Documentation  4.4

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• Examples with a custom flow element
• Simple Custom Flow Element

Simple Custom Flow Element

Introduction

This example shows a very simple flow element which takes a date of birth and returns an star sign. Although a basic (and not all that useful) flow element, the example demonstrates how you can start to implement your own flow elements.

Download example

The source code used in this example is available here:

• C# Visual Studio project
• Java project
• PHP project
• Node.js project

Dependencies

The flow element will need a reference to the Pipeline core package

C# Java PHP Node.js

Select a tab to view language specific dependencies.

Create a new console project (.NET Core or Framework) and add a reference to the FiftyOne.Pipeline.Core NuGet package.

The only dependency needed for Java is the pipeline.core Maven package from com.51degrees. To include this, add the following to the <dependencies> section of the project's pom.xml:

<dependency>

<groupId>com.51degrees</groupId>

<artifactId>pipeline.core</artifactId>

<version>4.2.0</version>

</dependency>

Add a dependency to the fiftyone.pipeline.core composer package to the composer.json, and required it in the source with include("../vendor/autoload.php");

Add a dependency to the fiftyone.pipeline.core NPM package to the package.json, and required it in the source with require("fiftyone.pipeline.core").

Data

The element data being added to the flow data by this flow element is a star sign. So this should have its own 'getter' in its element data.

C# Java PHP Node.js

Select a tab to view language specific element data implementation.

.NET supports interfaces, so the element data should have a public interface and an internal concrete implementation with easy 'setters'.

In this example, only one value is populated. So an interface IStarSign will extend IElementData to add a 'getter' for it.

Now the internal implementation of it will implement this 'getter' and add a 'setter' for the flow element to use.

Java supports interfaces, so the element data should have a public interface and a package private concrete implementation with easy 'setters'.

In this example, only one value is populated. So an interface StarSignData will extend ElementData to add a 'getter' for it.

Now the internal implementation of it will implement this 'getter' and add a 'setter' for the flow element to use.

Note that this concrete implementation of StarSignData sits in the same package as the flow element, not the StarSignData interface, as it only needs to be accessible by the flow element.

PHP's implementation of element data does not require concrete getters for IDE autocompletion, so elementDataDictionary can be used.

Node's implementation of element data does not require concrete getters for IDE autocompletion, so elementDataDictionary can be used.

Flow element

Now the actual flow element needs to be implemented. For this, the flow element's base class can be used which deals with most of the logic. The element properties, evidence keys and the processing are all that need implementing.

C# Java PHP Node.js

Select a tab to view language specific flow element implementation.

First let's define a class which extends FlowElementBase (and partially implements IFlowElement). This has the type arguments of IStarSignData - the interface extending element data which will be added to the flow data, and IElementPropertyMetaData - as we only need the standard metadata for element properties.

This needs a constructor matching the FlowElementBase class. So it takes a logger, and an element data factory which will be used to construct an IStarSignData:

The Init method in this example will simply initialize a list of star signs with the start and end dates of each star sign and add each to a list of a new class named StarSign which has the following simple implementation:

Note that the year of the start and end date are both set to 1, as the year should be ignored, but the year 0 cannot be used in a DateTime.

The new Init method looks like this:

Now the abstract methods can be implemented to create a functional flow element.

First let's define a class which extends FlowElementBase (which partially implements FlowElement). This has the type arguments of StarSignData - the interface extending element data which will be added to the flow data, and ElementPropertyMetaData - as we only need the standard metadata for element properties.

This needs a constructor matching the FlowElementBase class. So it takes a logger, and an element data factory which will be used to construct a StarSignData:

The init method in this example will simply initialize a list of star signs with the start and end dates of each star sign and add each to a list of a new class named StarSign which has the following simple implementation:

Note that the year of the start and end date are both set to 0, as the year should be ignored.

The new init method looks like this:

Now the abstract methods can be implemented to create a functional flow element.

First let's define a class which extends flowElement:

Now the abstract methods can be implemented to create a functional flow element.

First let's define a class which extends flowElement.

This needs a constructor matching the flowElement class which initializes the element:

Now the abstract methods can be implemented to create a functional flow element.

Builder

Now the flow element needs one final thing, an element builder to construct it. This only needs to provide the flow element with a logger and an element data factory - as this example has no extra configuration options.

C# Java PHP Node.js

Select a tab to view language specific element builder implementation.

The element builder has one important method, and that is Build. This returns a new flow element which the element builder provides with a logger and an element data factory.

The element data factory is implemented in the element builder class to make use of the same logger factory.

The element builder has one important method, and that is build. This returns a new flow element which the element builder provides with a logger and an element data factory.

The element data factory is implemented in the element builder class to make use of the same logger factory.

The PHP implementation does not use separate builder classes. Instead the options are provided by optional constructor parameters.

The Node implementation does not use separate builder classes. Instead the options are provided by optional constructor parameters.

Usage

C# Java PHP Node.js

Select a tab to view language specific usage.

This new flow element can now be added to a Pipeline and used like:

to give an output of:

With a date of birth of 18/12/1992, your star sign is Sagittarius.

This new flow element can now be added to a Pipeline and used like:

to give an output of:

With a date of birth of 18/12/1992, your star sign is Sagittarius.

This new flow element can now be added to a Pipeline and used like:

To print the star sign of the user.

This new flow element can now be added to a Pipeline and used like:

To print the star sign of the user.

This new flow element can now be added to a Pipeline and used like:

to give an output of:

With a date of birth of 18/12/1992, your star sign is Sagittarius.

Next steps

The example for Custom On-premise Engine shows how you can extend the functionality of this flow element to use a data file.

The flow element can also be upgraded to use evidence supplied by the client, as shown in the Custom Client-Side Evidence example.

To delegate the processing and logic to a cloud service, refer to the Custom Cloud Engine example.

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