io.cdap.wrangler.api

Interface Directive

All Superinterfaces:

Executor<List<Row>,List<Row>>, Serializable

public interface Directive
extends Executor<List<Row>,List<Row>>

Directive is a user defined directive. DIE - Define, Initialize & Execute - Pattern Following is a simple example of how to use this interface.

Field Summary

Fields

Modifier and Type	Field and Description
static String	TYPE This defines a interface variable that is static and final for specify the type of the plugin this interface would provide.

Method Summary

Modifier and Type	Method and Description
UsageDefinition	define() This method provides a way for the developer to provide information about the arguments expected by this directive.

Methods inherited from interface io.cdap.wrangler.api.Executor

destroy, execute, initialize

Field Detail

TYPE

static final String TYPE

This defines a interface variable that is static and final for specify the type of the plugin this interface would provide.

This constant should be used when defining a plugin. An example of such usage is as follow:

See Also:

Constant Field Values

Method Detail

define

UsageDefinition define()

This method provides a way for the developer to provide information about the arguments expected by this directive. The definition of arguments would provide information to the framework about how each argument should be parsed and interpretted.

This method uses UsageDefinition#Builder to build the token definitions. Each token definition consists of name, TokenType and optional field that specifies whether the token specified is optionally present.

The UsageDefinition provides different methods to define, and as well generate usage based on the definition.

This method is invoked by the framework at the time of creating an executable directive that will be added to the RecipePipeline. It's generally during the configuration phase.

.

NOTE: As best practice, developer needs to make sure that this class doesn't throw an exception. Also, it should not include external libraries that can generate exception unknown to the developer.

Following is an example of how define could be used. public UsageDefinition define() { UsageDefinition.Builder builder = UsageDefinition.builder(); builder.define("column", TokeType.COLUMN_NAME); // :column builder.define("number", TokenType.NUMERIC, Optional.TRUE); // 1.0 or 8 builder.define("text", TokenType.TEXT); // 'text' builder.define("boolean", TokenType.BOOL); // true / false builder.define("expression", TokenType.EXPRESSOION); // exp: { age < 10.0 } }

TokenType supports many different token types that can be used within the usage definition.

Returns:

A object of UsageDefinition containing definitions of each argument expected by this directive.

See Also:

TokenType