com.neurosys.etl.common.transformers

Class EntityChainAccessTransformer

java.lang.Object

com.neurosys.etl.common.transformers.UsesIntermediateObjectImpl

com.neurosys.etl.common.transformers.EntityChainAccessTransformer

All Implemented Interfaces:

AccessorLookUp, ContextAware, FunctionTransformer, UsesIntermediateObject, Serializable, Function, org.apache.commons.collections.Transformer

public class EntityChainAccessTransformer
extends UsesIntermediateObjectImpl
implements FunctionTransformer, AccessorLookUp

A convenient way to access (read only) an entity; and derive the accessor object or value using any of the following methods:

• Dot chaining convention like "a.b.c". Assuming the passed entity has an attribute a; a contains b; b contains c.
• Map based derivation: One may also substitute and derive from Maps where c could be a Key in a Map b in the entity a.
• List/Object Array based derivation: If List is provided; one can provide Index number as the accessor. (-) Numbers count from end of list. -1 means last element and so on.
• JSON based derivation: If the attribute isn't a field or a Map then it tries a JSON alternative if jsonTransformer is provided.

TODO: Add unit test case for List scenarios

Author:

Arjun Dhar

See Also:

EntityChainAccessModifierTransformer, ObjectFieldValueTransformer, Serialized Form

Field Summary

Fields inherited from class com.neurosys.etl.common.transformers.UsesIntermediateObjectImpl

intermediateResults, resultNamesUsed, resultsThatAreOptional

Constructor Summary

Constructors

Constructor and Description
EntityChainAccessTransformer()
EntityChainAccessTransformer(String accessor)

Method Summary

Modifier and Type	Method and Description
Object	get(Object entity, Object key)
String	getAccessor() A string representation in a.b.c format; where any word represents a property as an entity or a map.
org.apache.commons.collections.Transformer	getJsonTransformer() If provided; will attempt to convert a String intermediate-input in chain; and extract the JSON property directly Performance Note: Using a JSON transformer for a Field maybe convenient; however it also results in a conversion cost.
boolean	isReturnNullOnException() If a property or value is not found should exceptions be allowed to propagate or mute and return null
void	setAccessor(String accessor) A string representation in a.b.c format; where any word represents a property as an entity or a map.
void	setJsonTransformer(org.apache.commons.collections.Transformer jsonTransformer) If provided; will attempt to convert a String intermediate-input in chain; and extract the JSON property directly Performance Note: Using a JSON transformer for a Field maybe convenient; however it also results in a conversion cost.
void	setReturnNullOnException(boolean returnNullOnException) If a property or value is not found should exceptions be allowed to propagate or mute and return null
Object	transform(Object input)
Object	transform(Object input, String accessor)

Methods inherited from class com.neurosys.etl.common.transformers.UsesIntermediateObjectImpl

determineInput, getInputFromContext, getInterMediateResults, getResultNamesThatAreOptional, getResultNamesUsed, setIntermediateResults, setResultNamesThatAreOptional, setResultNamesUsed

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface com.neurosys.etl.common.transformers.FunctionTransformer

apply

Methods inherited from interface java.util.function.Function

andThen, compose, identity

Constructor Detail

EntityChainAccessTransformer

public EntityChainAccessTransformer()

EntityChainAccessTransformer

public EntityChainAccessTransformer(String accessor)

Method Detail

transform

public Object transform(Object input)

Specified by:

transform in interface org.apache.commons.collections.Transformer

transform

public Object transform(Object input,
                        String accessor)

get

public Object get(Object entity,
                  Object key)
           throws Exception

Specified by:

get in interface AccessorLookUp

Parameters:

entity - as Entity to be looked up

key - to lookup the entity

context[0] - returnNullOnException @nullable true

context[1] - jsonTransformer @nullable true

Returns:

Object

Throws:

Exception

getAccessor

public String getAccessor()

A string representation in a.b.c format; where any word represents a property as an entity or a map.

setAccessor

public void setAccessor(String accessor)

A string representation in a.b.c format; where any word represents a property as an entity or a map.

isReturnNullOnException

public boolean isReturnNullOnException()

If a property or value is not found should exceptions be allowed to propagate or mute and return null

Default value:

false

setReturnNullOnException

public void setReturnNullOnException(boolean returnNullOnException)

If a property or value is not found should exceptions be allowed to propagate or mute and return null

Default value:

false

getJsonTransformer

public org.apache.commons.collections.Transformer getJsonTransformer()

If provided; will attempt to convert a String intermediate-input in chain; and extract the JSON property directly
Performance Note: Using a JSON transformer for a Field maybe convenient; however it also results in a conversion cost. For scenarios; where multiple fields have to be derived from the same JSON you maybe better off caching or using a once converted JSON object and referring to it rather than transforming again and again for each access.

setJsonTransformer

public void setJsonTransformer(org.apache.commons.collections.Transformer jsonTransformer)

If provided; will attempt to convert a String intermediate-input in chain; and extract the JSON property directly
Performance Note: Using a JSON transformer for a Field maybe convenient; however it also results in a conversion cost. For scenarios; where multiple fields have to be derived from the same JSON you maybe better off caching or using a once converted JSON object and referring to it rather than transforming again and again for each access.