jsonPath: how confirm the data returned is just one element? and when it is not an array - jsonpath

Question

I am working with:
Spring MVC
Spring MVC Testing
Assuming that a #Controller working with #ResponseBody returns a set of domain objects represented in JSON format and through print() method I can confirm the following:
Body = [ {
"id" : "88",
"nombre" : "Manuel",
"apellido" : "Jordan",
"fecha" : 1449370807750
}, {
"id" : "87",
"nombre" : "Leonardo",
"apellido" : "Jordan",
"fecha" : 1449370807750
}, {
...
}, {
...
}, {
...
} ]
Observe that content is an array.
Through Spring MVC Testing and with hamcrest I have the following:
resultActions.andExpect(jsonPath('$').exists())
.andExpect(jsonPath('$').isArray())
.andExpect(jsonPath('$',hasSize(5)))
…
Until here all work fine.
But assuming the #Controller returns just one element (One Domain Object) and again through the print() method I can see the following:
Body = {
"id" : "100",
"nombre" : "Jesús Você",
"apellido" : "Mão Nuñez",
"fecha" : 1449372342312
}
Observe it is not an array
I have currently the following:
resultActions.andExpect(jsonPath('$').exists())
//.andExpect(jsonPath('$').isArray()) <--- fails
.andExpect(jsonPath('$.*', hasSize(4) ))
How I can confirm the data returned is just one element?
It when is not an array.
I mean, I want have the same approach/behaviour about the following from XML
<persona>
<id>100</id>
<nombre>Jesús Você</nombre>
<apellido>"Mão Nuñez"</apellido>
<fecha>2015-12-05T22:00:07.756-05:00</fecha>
</persona>
Through
resultActions.andExpect(xpath("persona").exists())
.andExpect(xpath("persona").nodeCount(1))
Practically, what is the equivalent of xpath("persona").nodeCount(1) to jsonPath?
Thanks