Dynamically build json using groovy - json

Question

I am trying to dynamically build some json based on data I retrieve from a database. Up until the opening '[' is the "root" I guess you could say. The next parts with name and value are dynamic and will be based on the number of results I get from the db. I query the db and then the idea was to iterate through the result adding to the json. Can I use jsonBuilder for the root section and then loop with jsonSlurper to add each additional section? Most of the examples I have seen deal with a root and then a one time "slurp" and then joining the two so wasn't sure if I should try a different method for looping and appending multiple sections.
Any tips would be greatly appreciated. Thanks.
{
"hostname": "$hostname",
"path": "$path",
"extPath": "$extPath",
"appName": "$appName",
"update": {"parameter": [
{
"name": "$name",
"value": "$value"
},
{
"name": "$name",
"value": "$value"
}
]}
}
EDIT: So what I ended up doing was just using StringBuilder to create the initial block and then append the subsequent sections. Maybe not the most graceful way to do it, but it works!
//Create the json string
StringBuilder json = new StringBuilder("""{
"hostname": "$hostname",
"path": "$path",
"extPath": "$extPath",
"appName": "$appName",
"update": {"parameter": ["""
)
//Append
sql.eachRow("""<query>""",
{ params ->
json.append("""{ "name": "params.name", "value": "params.value" },""");
}
)
//Add closing json tags
json.append("""]}}""")

Answer 1

If I got your explanation correctly and if the data is not very big (it can live in memory), I'd build a Map object (which is very easy to work with in groovy) and convert it to JSON afterwards. Something like this:
def data = [
hostname: hostname,
path: path,
extPath: extPath,
appName: appName,
update: [parameter: []]
]
sql.eachRow(sqlStr) { row ->
data.update.parameter << [name: row.name, value: row.value]
}
println JsonOutput.toJson(data)

Answer 2

If you're using Grails and Groovy you can utilize grails.converters.JSON.
First, define a JSON named config:
JSON.createNamedConfig('person') {
it.registerObjectMarshaller(Person) {
Person person ->
def output = [:]
output['name'] = person.name
output['address'] = person.address
output['age'] = person.age
output
}
}
This will result in a statically defined named configuration for the Object type of person. Now, you can simply call:
JSON.use('person') {
Person.findAll() as JSON
}
This will return every person in the database with their name, address and age all in one JSON request. I don't know if you're using grails as well in this situation though, for pure Groovy go with another answer here.