com.cinchapi.etl

Interface Transformer

Functional Interface:

This is a functional interface and can therefore be used as the assignment target for a lambda expression or method reference.

@FunctionalInterface
public interface Transformer

A Transformer is a routine that takes a key/value pair and potentially alters one or both of them, prior to import.

Sometimes, raw data from a source must be modified before being imported into Concourse, for example:

• Modifying keys by changing their case or stripping illegal characters
• Normalizing values, for example, converting strings to a specific case or sanitizing
• Compacting representation by values from an enumerated set of values to a simple integer
• Constructing a link or resolvable link

Method Summary

Modifier and Type	Method and Description
default java.util.Map<java.lang.String,java.lang.Object>	transform(java.util.Map<java.lang.String,java.lang.Object> object) Transform all of the key/value pairs in the object and returned the merged result.
java.util.Map<java.lang.String,java.lang.Object>	transform(java.lang.String key, java.lang.Object value) Potentially transform the provided key and value pair.
default java.util.Map.Entry<java.lang.String,java.lang.Object>	transform(java.lang.String key, java.lang.String value) Deprecated. in version 1.1.0; scheduled to be removed in version 2.0.0. Use transform(String, Object) instead.

Method Detail

transform

@Nullable
 @Deprecated
default java.util.Map.Entry<java.lang.String,java.lang.Object> transform(java.lang.String key,
                                                                                                java.lang.String value)

Deprecated. in version 1.1.0; scheduled to be removed in version 2.0.0. Use transform(String, Object) instead.

Potentially transform one or both of the key/value pair. If no transformation should occur, it is acceptable to return null to inform the caller that the import values are acceptable in their passed in state. Otherwise, the preferred pair should be wrapped in an Map.Entry object.

Parameters:

key - the raw key to potentially transform

value - the raw value to potentially transform; in which case, it is acceptable to return any kind of object, but it is recommended to return an encoded String (i.e. don't return a Link object, but return a string that encodes a link (@record@) instead)

Returns:

a Map.Entry object that contains the transformed key/value pair or null if no transformation occurred

transform

default java.util.Map<java.lang.String,java.lang.Object> transform(java.util.Map<java.lang.String,java.lang.Object> object)

Transform all of the key/value pairs in the object and returned the merged result.

The result of the transformations will be merged using the upsert merge strategy.

Parameters:

object -

Returns:

the transformation

transform

@Nullable
java.util.Map<java.lang.String,java.lang.Object> transform(java.lang.String key,
                                                                     java.lang.Object value)

Potentially transform the provided key and value pair.

There are four possible transformation scenarios:

1. Neither the key or value changes
2. Only the key changes
3. Only the value changes
4. Both the key and value change

In scenario 1, this method returns null. In the other scenarios, this method returns a Map which contains the data that will replace the original key and value. So, if the input parameters are part of a larger data map, the caller should merge the data from this map with the source data.

Even though the inputs to this method are simple, a Map is returned to allow for complex transformations. For example,

• You can transform a single value into multiple values by including multiple objects in the associated values collection.
• You can transform a single key/value pair into multiple key/value pairs by including multiple keys in the returned map

For the basic case of transforming a single key/value pair into another single key/value pair, you should use the Transformation#to(Object, Object) utility.

Parameters:

key - the raw key to potentially transform

value - the raw value to potentially transform

Returns:

the transformation