JSON

To manipulate JSON object, Vert.x proposes its own implementation of JsonObject and JsonArray. This is because, unlike some other languages, Java does not have first class support for JSON.

When developping a vert.x application with Groovy, you can rely on these two classes, or use the (JSON support from Groovy. This section explains how to use the Vert.x classes.

Note
Most vert.x methods taking a JSON object as argument in their Java version, take a map instead.

JSON objects

The JsonObject class represents JSON objects.

A JSON object is basically just a map which has string keys and values can be of one of the JSON supported types (string, number, boolean).

JSON objects also support null values.

Creating JSON objects

Empty JSON objects can be created with the default constructor.

You can create a JSON object from a string or g-string JSON representation as follows:

def object = new JsonObject("{\"foo\":\"bar\"}")
def object2 = new JsonObject("""
{
"foo": "bar"
}
""")

In Groovy it’s also convenient to create a JSON object from a map:

def map = [ "foo" : "bar" ]
def json = new JsonObject(map)

Nested maps are transformed to nested JSON objects.

It can be achieved using a Groovy cast as well:

def map = [ "foo" : "bar" ]
def json = map as JsonObject

Putting entries into a JSON object

Use the put methods to put values into the JSON object.

The method invocations can be chained because of the fluent API:

def object = new JsonObject()
object.put("foo", "bar").put("num", 123).put("mybool", true)

The Groovy subscript operator works too:

def object = new JsonObject()
object["foo"] = "bar"
object["num"] = 123
object["mybool"] = true

Getting values from a JSON object

You get values from a JSON object using the getXXX methods, for example:

dev val1 = jsonObject.getString("some-key")
def val2 = jsonObject.getInteger("some-other-key")

The Groovy subscript operator works too:

dev val1 = jsonObject["some-key"]
def val2 = jsonObject["some-other-key"]

Encoding the JSON object to a String

You use encode to encode the object to a String form. There is also a encodePrettily that makes the output pretty (understand multi-line and indented).

JSON arrays

The JsonArray class represents JSON arrays.

A JSON array is a sequence of values (string, number, boolean).

JSON arrays can also contain null values.

Creating JSON arrays

Empty JSON arrays can be created with the default constructor.

You can create a JSON array from a string JSON representation or a list as follows:

def object = new JsonArray("[\"foo\", \"bar\"]")
def object2 = new JsonObject("""
[
"foo", "bar"
]
""")

In Groovy it’s also convenient to create a JSON array from a list:

def list = [ "foo", "bar" ]
def json = new JsonArray(list)

Nested maps are transformed to nested JSON objects.

It can be achieved using a Groovy cast as well:

def list = [ "foo", "bar" ]
def json = map as JsonArray

Adding entries into a JSON array

You add entries to a JSON array using the add methods.

def array = new JsonArray()
array.add("foo").add(123).add(false)

The left shift operator can be used as well:

def array = new JsonArray()
array << "foo"
array << 123
array << false

Getting values from a JSON array

You get values from a JSON array using the getXXX methods, for example:

def val = array.getString(0)
def intVal = array.getInteger(1)
def boolVal = array.getBoolean(2)

The Groovy subscript operator works too:

def val = array[0]
def intVal = array[1]
def boolVal = array[2]

Encoding the JSON array to a String

You use encode to encode the array to a String form. There is also a encodePrettily that makes the output pretty (understand multi-line and indented).