org.thales.punch.libraries.punchlang.operator

Class FindByKeyOperator

java.lang.Object

org.thales.punch.libraries.punchlang.operator.FindByKeyOperator

public class FindByKeyOperator
extends Object

The FindByKey operator gives you efficient lookup inside Json documents, passed to your punchlet as punch Tuple.

Say you have a json resource file called "map.json" containing the following json:

 
 [
   {  "city" : "paris",
      "user" : "bob",
      "datacenter" : "dc1",
   },
   {  "city" : "london",
      "user" : ["ted", "bob"],
      "datacenter" : "dc7",
   },
   {  "city" : "madrid",
      "user" : "sophie",
   }
 ]
 
 

Say you want to retrieve all elements matching "city" == "paris". Write :

 
 Tuple result;
 findByKey(map, "city").on("paris").into(result);
 print(result);
 
 

You'll get :

 
 [ { "city": "paris", "user": "bob", "datacenter": "dc1"} ]
 
 

Whenever several matches are found, you can get the result as a plain array, or as a union. With union, each property is returned as a set, so that you have immediately the matches at hand without the need for additional scans. For example:

 
 findByKey(map, "user").on("bob").into(result);
 
 

produces

 
 [
 { "city": "paris", "user": "bob", "datacenter": "dc1"  },
 { "city": "london", "user": ["ted","bob"],"datacenter": "dc7"}
 ]
 
 

that is, a plain array with all matched elements from your original tuple. Now if instead you do

 
 findByKey(map, "user").union().on("bob").into(result);
 
 

you will get

 
 { "city": [ "paris", "london"],
 "user": ["bob", ["ted", "bob"]],
 "datacenter": ["dc1","dc7"]
 }
 
 

This example is available here : finding.punch. To run it, use the json files from the json directory.

Constructor Summary

Constructors

Constructor and Description
FindByKeyOperator(Tuple sourceMap, String... key) Return a new FindByKeyOperatorRefactor, ready to answer queries with one or several lookup values.

Method Summary

Modifier and Type	Method and Description
FindByKeyOperator	defaultMatch(String defaultMatch) Set a default value if no match is found.
boolean	into(Tuple into) Fire the operator
FindByKeyOperator	on(String... values) Take the lookup keys from Strings
FindByKeyOperator	on(Tuple... tuples) Take the lookup key from an array of tuples
FindByKeyOperator	union() Make the result be computed as a union.
FindByKeyOperator	where(String key, String value) Return an operator to find a named element which matches some value
FindByKeyOperator	where(String key, Tuple value) Return an operator to find a named element which matches some tuple value.

Methods inherited from class java.lang.Object

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

Constructor Detail

FindByKeyOperator

public FindByKeyOperator(Tuple sourceMap,
                         String... key)

Return a new FindByKeyOperatorRefactor, ready to answer queries with one or several lookup values.

Parameters:

sourceMap - the input document

key - one or several key identifying the properties on which you will want to query.

Method Detail

union

public FindByKeyOperator union()

Make the result be computed as a union.

Returns:

this operator

on

public FindByKeyOperator on(Tuple... tuples)

Take the lookup key from an array of tuples

Parameters:

tuples - the tuple containing the lookup search values

Returns:

this operator

where

public FindByKeyOperator where(String key,
                               String value)

Return an operator to find a named element which matches some value

Parameters:

key - the target key name

value - the searched value

Returns:

this operator

where

public FindByKeyOperator where(String key,
                               Tuple value)

Return an operator to find a named element which matches some tuple value.

Watch out the tuple must contain a String.

Parameters:

key - the target key name

value - the searched value

Returns:

this operator

on

public FindByKeyOperator on(String... values)

Take the lookup keys from Strings

Parameters:

values - the key

Returns:

this operator

defaultMatch

public FindByKeyOperator defaultMatch(String defaultMatch)

Set a default value if no match is found.

Parameters:

defaultMatch - the default value

Returns:

this operator

into

public boolean into(Tuple into)

Fire the operator

Parameters:

into - where to put the result

Returns:

true if there is a match