Add Parse JSON processor doc.

_data-prepper/pipelines/configuration/processors/parse-json-processor.md

@@ -0,0 +1,80 @@
+---
+layout: default
+title: Parse JSON processor
+parent: Processors
+grand_parent: Pipelines
+nav_order: 45
+---
+
+# Parse JSON processor
+
+The `parse_json` processor parses JSON data for an event, including any nested fields. The processor extracts the JSON pointer data and adds the input event to the extracted fields.
+
+## Usage
+
+To get started, create the following `pipeline.yaml` file:
+
+```yaml
+parse-json-pipeline:
+  source:
+    stdin:
+  processor:
+    - parse_json:
+  sink:
+    - stdout:
+```
+
+### Basic example
+
+You can test the JSON Processor with the previous configuration by using the following example.
+
+Run the pipeline and paste the following line into your console, then enter `exit` on a new line:
+
+```
+{"outer_key": {"inner_key": "inner_value"}}
+```
+{% include copy.html %}
+
+The processor parses the message into the following format:
+
+```
+{"message": {"outer_key": {"inner_key": "inner_value"}}", "outer_key":{"inner_key":"inner_value"}}}
+```
+
+### Example with JSON pointer
+
+You can parse a selection of the JSON data by specifying a JSON pointer and using the `pointer` option in the configuration. See the following YAML configuration file and example of pointer use:
+
+```yaml
+parse-json-pipeline:
+  source:
+    stdin:
+  processor:
+    - parse_json:
+        pointer: "outer_key/inner_key"
+  sink:
+    - stdout:
+```
+
+Run the pipeline and paste the following line into your console, then enter `exit` on a new line.
+
+```
+{"outer_key": {"inner_key": "inner_value"}}
+```
+{% include copy.html %}
+
+The processor parses the message into the following format:
+
+```
+{"message": {"outer_key": {"inner_key": "inner_value"}}", "inner_key": "inner_value"}
+```
+
+## Configuration
+
+You can configure the `Parse JSON` processor with the following options.
+
+| Option | Required | Type | Description |
+| :--- | :--- | :--- | :--- | 
+| `source` | No | String | The field in the `Event` that will be parsed. Default value is `message`. |
+| `destination` | No | String | The destination field of the parsed JSON. Defaults to the root of the `Event`. Cannot be `""`, `/`, or any whitespace-only `String` because these are not valid `Event` fields. |
+| `pointer` | No | String | A JSON Pointer to the field to be parsed. There is no `pointer` by default, meaning the entire `source` is parsed. The `pointer` can access JSON Array indices as well. If the JSON Pointer is invalid then the entire `source` data is parsed into the outgoing `Event`. If the pointed-to key already exists in the `Event` and the `destination` is the root, then the pointer uses the entire path of the key. |