> ## Documentation Index
> Fetch the complete documentation index at: https://docs.apinizer.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Extracting Data from JSON in Payload Field of Incoming JWT Key

> Extracting payload data from JWT token with Groovy script

## Groovy Script

```groovy theme={null}
import groovy.json.JsonSlurper
import org.apache.commons.codec.binary.Base64

def authzHeaderValue = requestHeaderMapToTargetAPI.get("Authorization")
authzHeaderValue = authzHeaderValue.split('\\.')[1] //Bearer yazan kısım için, veri her zaman ilk nokta işaretinden sonra geçtiği için ayrılma ihtiyacı duyulmamıştır.

def decodedValue = new String(Base64.decodeBase64(authzHeaderValue),"UTF-8")
def jsonSlurper = new JsonSlurper()
def jsonMessage = jsonSlurper.parseText(decodedValue)

//do some logic with json:
requestHeaderMapToTargetAPI.put("usernameTest",jsonMessage.username)
```

## Explanation

This script performs the following operations:

1. **Token Retrieval**: JWT token is retrieved from Authorization header
2. **Payload Parsing**: JWT token format is `header.payload.signature`. Token is split by dot (.) character and payload part (second section) is retrieved
3. **Base64 Decode**: Payload part is Base64 encoded JSON format. This part is decoded
4. **JSON Parse**: Decoded data is parsed as JSON
5. **Data Usage**: Desired fields (e.g., `username`) are extracted and can be used

In the example, the `username` field within the payload is retrieved and added to the header as `usernameTest`.

<Note>
  This script should be run on the request line (Request Policy) because it uses the `requestHeaderMapToTargetAPI` variable.
</Note>