net.obvj.confectory.merger

Class GenericJSONConfigurationMerger<T>

java.lang.Object

net.obvj.confectory.merger.AbstractConfigurationMerger<T>

net.obvj.confectory.merger.GenericJSONConfigurationMerger<T>

All Implemented Interfaces:

ConfigurationMerger<T>

Direct Known Subclasses:

JSONObjectConfigurationMerger

public class GenericJSONConfigurationMerger<T>
extends AbstractConfigurationMerger<T>

A generic ConfigurationMerger that combines two Configuration objects of type JSON.

The operation is provider-agnostic and depends on a specialized JsonProvider which must be specified via constructor.

The resulting JSON document from the merge operation shall contain all exclusive objects from source documents and in case of In case of key collisions (i.e., the same key appears in both documents), the following rules will be applied:

• for simple values, such as strings, numbers and boolean values, the value from the highest-precedence Configuration will be selected;
• if the value is a JSON object in both JSON sources, the two objects will be merged recursively; if the types are not compatible (e.g.: JSON object in one side and simple value or array in the other), then a copy of the object from the highest-precedence Configuration will be selected as fallback;
• if the value is a JSON array in both JSON sources, then all elements from both two arrays will be copied distinctively (i.e., repeated elements will not be copied to the resulting JSON document); if the types are not compatible (e.g.: JSON array in one side and simple value or complex object in the other), then a copy of the object from the highest-precedence Configuration will be selected as fallback

A special solution for merging arrays of distinct objects with a specific key can be created using the optional constructor GenericJSONConfigurationMerger(JsonProvider, Map).

Since:

2.1.0

Author:

oswaldo.bapvic.jr (Oswaldo Junior)

See Also:

JsonProvider, ConfigurationMerger

Constructor Summary

Constructors

Constructor and Description
GenericJSONConfigurationMerger(JsonProvider jsonProvider) Creates a new JSON Configuration Merger for a specific provider.
GenericJSONConfigurationMerger(JsonProvider jsonProvider, Map<String,String> distinctObjectKeysInsideArrays) Creates a new JSON Configuration Merger for a specific provider and a preset map of distinct keys.

Method Summary

Methods inherited from class net.obvj.confectory.merger.AbstractConfigurationMerger

merge

Methods inherited from class java.lang.Object

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

Constructor Detail

GenericJSONConfigurationMerger

public GenericJSONConfigurationMerger(JsonProvider jsonProvider)

Creates a new JSON Configuration Merger for a specific provider.

Parameters:

jsonProvider - the JsonProvider to use; not null

Throws:

NullPointerException - if the specified JsonProvider is null

GenericJSONConfigurationMerger

public GenericJSONConfigurationMerger(JsonProvider jsonProvider,
                                      Map<String,String> distinctObjectKeysInsideArrays)

Creates a new JSON Configuration Merger for a specific provider and a preset map of distinct keys.

The distinctObjectKeysInsideArrays map shall be used to specify key objects inside arrays.

For example, consider the following document:

 {
   "params": [
     {
       "param": "name",
       "value": "John Doe"
     },
     {
       "param": "age",
       "value": 33
     }
   ]
 }
 

A map entry with the key "$.params" associated with the "param" value tells the algorithm to check for distinct objects identified by the value inside the "param" field during the merge of the "$.params" array.

In other words, if two JSON documents contain different objects identified by the same "param" attribute inside the array returned by the JsonPath expression "$.params", then only the object from the Configuration with the highest precedence will be selected.

A JsonPath expression can be specified using either dot- or bracket-notation, but complex expressions containing filters, script, subscript, or union operations, are not supported.

Parameters:

jsonProvider - the JsonProvider to use; not null

distinctObjectKeysInsideArrays - a map that associates JsonPath expressions and distinct keys during the merge of an array; null is allowed

Throws:

NullPointerException - if the specified JsonProvider is null

IllegalArgumentException - if the map contains a null or empty expression

com.jayway.jsonpath.InvalidPathException - if the specified JsonPath expression is invalid