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51Degrees API Documentation  4.4

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• Concepts
• Configuration
• Builders
• Element Builder

Element Builder

Introduction

Flow elements are constructed using a builder which follows the fluent builder pattern. This gives a consistent structure when building any flow element and allows automatic building via configuration files.

Typically the flow element built by an element builder is added to a Pipeline via a pipeline builder.

By convention, the configuration of a flow element is immutable once it has been constructed, so all configuration should be done in the builder.

See the Specification for more technical details.

Configuration

Following the convention of fluent builder, configuration methods are prefixed with 'set'. For example, the method to set a configuration option with the name 'cachesize' would have a 'SetCacheSize' method which takes the value of the option as an argument and returns the builder.

The precise constraints around these methods vary by language.

C# Java

Select a language.

In .NET, the user is free to define methods on the builder as they wish. However, if they want to take advantage of the build from configuration method on the Pipeline then they must follow certain rules:

1. A configuration method on an element builder must have one and only one parameter.
2. The builder must have at least one method named 'Build' which returns an instance that implements IFlowElement.
3. The types of any parameters on configuration methods and build methods must be string or have a static 'TryParse' method. This can be an extension method if needed. It is used to parse the string value from the configuration file.

In Java, the user is free to define methods on the builder as they wish. However, if they want to take advantage of the build from configuration method on the Pipeline then they must follow certain rules:

1. A configuration method on an element builder must have one and only one parameter.
2. The builder must have at least one method named 'Build' which returns an instance that implements FlowElement.
3. The types of any parameters on configuration methods and build methods must be string or have a static parse method. This can be in the boxed class in the case of primative type e.g. Integer.parseInt is used for int. It is used to parse the string value from the configuration file.

Building

Once all options are set in the builder, a 'build' method is used to build and return a flow element with the configuration provided. A build method can take additional arguments and a builder may have multiple build methods. When an argument appears on all build methods for that builder it becomes compulsory.

For example, a 'Resource Key' is compulsory for 51Degrees' cloud engines. Consequently, it appears as an argument in all build methods for the associated builders.

Combinations of compulsory arguments can also be arranged. For example, 51Degrees' on-premise engines require either a filename or a data structure containing the file data in memory. Therefore they have two build methods, one taking a filename and the other taking the memory-based data structure.

Usage

C# Java

Select a language.

IFlowElement element = new ElementBuilder(loggerFactory)

.SetOption(value)

.SetAnotherOption(anotherValue)

.Build(compulsoryOption);

FlowElement element = new ElementBuilder(loggerFactory)

.setOption(value)

.setAnotherOption(anotherValue)

.build(compulsoryOption);

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