Pivotal GemFire® v9.1

Adding JSON Documents to the GemFire Cache

The JSONFormatter API allows you to put JSON formatted documents into regions and retrieve them later by storing the documents internally as PdxInstances.

GemFire supports the use of JSON formatted documents natively. When you add a JSON document to a GemFire cache, you call the JSONFormatter APIs to transform them into the PDX format (as a PdxInstance), which enables GemFire to understand the JSON document at a field level.

In terms of querying and indexing, because the documents are stored internally as PDX, applications can index on any field contained inside the JSON document including any nested field (within JSON objects or JSON arrays.) Any queries run on these stored documents will return PdxInstances as results. To update a JSON document stored in GemFire , you can execute a function on the PdxInstance.

You can then use the JSONFormatter to convert the PdxInstance results back into the JSON document.

JSONFormatter uses a streaming parser (Jackson, JSON processor) to turn JSON documents into the optimized PDX format. To use the JSONFormatter, make sure that lib/geode-dependencies.jar is available in your application’s CLASSPATH.

The JSONFormatter class has four static methods that are used to convert JSON document into PdxInstances and then to convert those PdxInstances back into JSON document.

You need to call the following methods before putting any JSON document into the GemFire region:

  • fromJSON. Creates a PdxInstance from a JSON byte array. Returns the PdxInstance.
  • fromJSON. Creates a PdxInstance from a JSON string. Returns the PdxInstance.

After putting the JSON document into a region as a PdxInstance, you can execute standard GemFire queries and create indexes on the JSON document in the same manner you would query or index any other GemFire PdxInstance.

After executing a GemFire query or calling region.get, you can use the following methods to convert a PdxInstance back into the JSON format:

  • toJSON. Reads a PdxInstance and returns a JSON string.
  • toJSONByteArray. Reads a PdxInstance and returns a JSON byte array.

For more information on using the JSONFormatter, see the Java API documentation for org.apache.geode.pdx.JSONFormatter.

Sorting Behavior of Serialized JSON Fields

By default, GemFire serialization creates a unique pdx typeID for each unique JSON document, even if the only difference between the JSON documents is the order in which their fields are specified.

If you prefer that JSON documents which differ only in the order in which their fields are specified map to the same typeID, set the property gemfire.pdx.mapper.sort-json-field-names to true. This tells the system to sort the JSON fields prior to serialization, allowing the system to identify matching entries, and helps reduce the number of pdx typeIDs that are generated by the serialization mechanism.