我想替换JSON字段
您可以执行以下操作：

import groovy.json.JsonBuilder
import groovy.json.JsonSlurper

// ...

// This hardcoded String represents "body" from the code in the question
String jsonString = '''
[{"RoleName": "Normal User","ModuleName": "Calendar Management"},
{"RoleName": "Reporter","ModuleName": "Incident Management"}]
'''
def slurper = new JsonSlurper()
def json = slurper.parseText(jsonString)

println 'Before Update...'
println new JsonBuilder(json).toPrettyString()

json[0].'RoleName' = 'Updated'

println 'After Update...'
println new JsonBuilder(json).toPrettyString()

输出：

Before Update...
[
    {
        "RoleName": "Normal User",
        "ModuleName": "Calendar Management"
    },
    {
        "RoleName": "Reporter",
        "ModuleName": "Incident Management"
    }
]
After Update...
[
    {
        "RoleName": "Updated",
        "ModuleName": "Calendar Management"
    },
    {
        "RoleName": "Reporter",
        "ModuleName": "Incident Management"
    }
]