Groovy JsonBuilder strange behavior when toString() - json

Question

I need to create a json to use as body in an http.request. I'm able to build dynamically up the json, but I noticed a strange behavior when calling builder.toString() twice. The resulting json was totally different. I'm likely to think this is something related to a kind of buffer or so. I've been reading the documentation but I can't find a good answer. Here is a code to test.
import groovy.json.JsonBuilder
def builder = new JsonBuilder()
def map = [
catA: ["catA-element1", "catA-element2"],
catB:[],
catC:["catC-element1"]
]
def a = map.inject([:]) { res, k, v ->
def b = v.inject([:]) {resp, i ->
resp[i] = k
resp
}
res += b
}
println a
def root = builder.query {
bool {
must a.collect{ k, v ->
builder.match {
"$v" k
}
}
}
should([
builder.simple_query_string {
query "text"
}
])
}
println builder.toString()
println builder.toString()
This will print the following lines. Pay attention to the last two lines
[catA-element1:catA, catA-element2:catA, catC-element1:catC]
{"query":{"bool":{"must":[{"match":{"catA":"catA-element1"}},{"match":{"catA":"catA-element2"}},{"match":{"catC":"catC-element1"}}]},"should":[{"simple_query_string":{"query":"text"}}]}}
{"match":{"catC":"catC-element1"}}
In my code I can easily send the first toString() result to a variable and use it when needed. But, why does it change when invoking more than one time?

Answer 1

I think this is happening because you are using builder inside the closure bool. If we make print builder.content before printing the result (buider.toString() is calling JsonOutput.toJson(builder.content)) we get:
[query:[bool:ConsoleScript54$_run_closure3$_closure6#294b5a70, should:[[simple_query_string:[query:text]]]]]
Adding println builder.content to the bool closure we can see that the builder.content is modified when the closure is evaluated:
def root = builder.query {
bool {
must a.collect{ k, v ->
builder.match {
"$v" k
println builder.content
}
}
}
should([
builder.simple_query_string {
query "text"
}
])
}
println JsonOutput.toJson(builder.content)
println builder.content
The above yields:
[query:[bool:ConsoleScript55$_run_closure3$_closure6#39b6156d, should:[[simple_query_string:[query:text]]]]]
[match:[catA:catA-element1]]
[match:[catA:catA-element2]]
{"query":{"bool":{"must":[{"match":{"catA":"catA-element1"}},{"match":{"catA":"catA-element2"}},{"match":{"catC":"catC-element1"}}]},"should":[{"simple_query_string":{"query":"text"}}]}}
[match:[catC:catC-element1]]
You can easily avoid that with a different builder for the closure inside:
def builder2 = new JsonBuilder()
def root = builder.query {
bool {
must a.collect{ k, v ->
builder2.match {
"$v" k
}
}
}
should([
builder.simple_query_string {
query "text"
}
])
}
Or even better:
def root = builder.query {
bool {
must a.collect({ k, v -> ["$v": k] }).collect({[match: it]})
}
should([
simple_query_string {
query "text"
}
])
}