json

GemFire JSON Example

The GemFire JSON-related APIs allow you to convert a JSON String into a binary form called JsonDocument that can be stored in a GemFire region. JsonDocuments use less memory and have better performance than JSON strings.

This example starts a GemFire cluster with one locator and two servers with a replicated region called example-region. It then uses the JSON-related APIs to create a JsonDocumentFactory which converts a JSON string into a JsonDocument. The converted JSON strings are stored as region entry values.

The example uses JSON strings that contain fields of different types. For example:

{
  "booleanField": true,
  "intField": 0,
  "name": "name0",
  "nestedField": 
  {
    "field1": 5,
    "field2": "something",
    "field3": 55555.0
  },
  "arrayField": [0, "Fred", 4.0, true]
}

The JsonDocument API is used to get the values of fields of a JSON document. For example, JsonDocument.getField().

For details about JsonDocumentFactory and JsonDocument. Please refer to the Javadoc or GemFire documentation.

Steps to run the JSON example

Build the code

$ ../gradlew build

Start a GemFire cluster with one locator and two servers

$ gfsh run --file=scripts/start.gfsh

Run the example code

$ ../gradlew run

It first creates a GemFire client with a proxy client cache. Then it converts a number of JSON strings to JsonDocuments with the default BSON storage format and put them to the example-region.

BSON and PDX are two underlying storage formats for JsonDocument. For the details, benefits and use cases of BSON and PDX storage formats, please refer to the GemFire documentation.

JsonDocument.toJson() is used to convert a JsonDocument back to a JSON string.

JsonDocument.getField() is used to get the value of a specific JSON field, including a nested field.

OQL query can be used to query JSON fields as well. For example:

Query: select * from /example-region where name='name5'

Query result:

[
  {"booleanField": true,
    "intField": 5,
    "name": "name5",
    "nestedField": 
    {
      "field1": 5,
      "field2": "something",
      "field3": 55555.0
    },
    "arrayField": [5, "Fred", 4.0, true]
  }
]

Query: select * from /example-region where arrayField[0]=6

Query result:

[
  {
    "booleanField": true,
    "intField": 6,
    "name": "name6",
    "nestedField":
    {
      "field1": 5,
      "field2": "something",
      "field3": 55555.0},
    "arrayField": [6, "Fred", 4.0, true]
  }
]

Stop the GemFire cluster

$ gfsh run --file=scripts/stop.gfsh