JSON转XML转换报错：无法从START_ARRAY反序列化HashMap（Groovy求助）

Hey there! Let's break down why you're hitting this error and get your JSON-to-XML script working smoothly.

What's Causing the Error? #

That error message is telling you exactly the issue: your payload is a JSON array (wrapped in []) instead of a single JSON object (wrapped in {}). Groovy tries to deserialize single JSON objects as HashMaps, but arrays get turned into Lists—so when your code treats it like a single object, it throws a fit.

For example, your input might look like this (array):

[{"AdditionalInfo": {"ClientEmail": "test@example.com"}, "Amount": 100, "WithdrawalId": "123"}]

Instead of this (single object):

{"AdditionalInfo": {"ClientEmail": "test@example.com"}, "Amount": 100, "WithdrawalId": "123"}

How to Fix It #

We’ll adjust the code to handle both scenarios—either processing multiple items from an array, or grabbing the first item if the payload was accidentally wrapped in brackets.

Option 1: Process a JSON Array (Multiple Items)

If your payload is supposed to be an array, modify the script to loop through each entry and generate corresponding XML nodes:

import groovy.xml.StreamingMarkupBuilder
import groovy.xml.XmlUtil

def xmlBuilder = new StreamingMarkupBuilder()
def payloadItems = payload // payload is a List here

writer = xmlBuilder.bind {
    mkp.declareNamespace( ns1: "TV")
    'ns1:transfers' { // Plural root node to wrap multiple transfer entries
        payloadItems.each { item ->
            'ns1:transfer' { // Fixed typo: "tranfer" → "transfer"
                'merchant_id'()
                'surveyYear'()
                'merchant_password' ()
                'email'(item.AdditionalInfo?.ClientEmail) // Use ?. to avoid null pointers if AdditionalInfo is missing
                'amount'(item.Amount)
                'reference_code'(item.WithdrawalId)
            }
        }
    }
}

return XmlUtil.serialize(writer)

Option 2: Handle a Single Object (Accidental Array)

If your payload should be a single object but is wrapped in an array, adjust the code to extract the first element:

import groovy.xml.StreamingMarkupBuilder
import groovy.xml.XmlUtil

def xmlBuilder = new StreamingMarkupBuilder()
// Check if payload is a list—if so, take the first item; else use it directly
def item = payload instanceof List ? payload[0] : payload

writer = xmlBuilder.bind {
    mkp.declareNamespace( ns1: "TV")
    'ns1:transfer' { // Fixed typo: "tranfer" → "transfer"
        'merchant_id'()
        'surveyYear'()
        'merchant_password' ()
        'email'(item.AdditionalInfo?.ClientEmail)
        'amount'(item.Amount)
        'reference_code'(item.WithdrawalId)
    }
}

return XmlUtil.serialize(writer)

Quick Debug Tips #

• Add a line to confirm your payload type:

  println "Payload type: ${payload.getClass().name}"
  

  If it prints java.util.ArrayList, you’re dealing with an array. If it’s java.util.LinkedHashMap, it’s a single object.
• The safe navigation operator ?. prevents null pointer exceptions if AdditionalInfo is missing from any item.
• Fixed the typo in ns1:tranfer to ns1:transfer (assuming that was a small mistake in your original code).

内容的提问来源于stack exchange，提问作者xkvt