groovy.json
[Groovy] Class JsonBuilder

java.lang.Object
  groovy.json.JsonBuilder

All Implemented Interfaces:

Writable

class JsonBuilder

A builder for creating JSON payloads.

This builder supports the usual builder syntax made of nested method calls and closures, but also some specific aspects of JSON data structures, such as list of values, etc. Please make sure to have a look at the various methods provided by this builder to be able to learn about the various possibilities of usage.

Example:

       def builder = new groovy.json.JsonBuilder()
       def root = builder.people {
           person {
               firstName 'Guillame'
               lastName 'Laforge'
               // Named arguments are valid values for objects too
               address(
                       city: 'Paris',
                       country: 'France',
                       zip: 12345,
               )
               married true
               // a list of values
               conferences 'JavaOne', 'Gr8conf'
           }
       }

       // creates a data structure made of maps (Json object) and lists (Json array)
       assert root instanceof Map

       assert builder.toString() == '{"people":{"person":{"firstName":"Guillame","lastName":"Laforge","address":{"city":"Paris","country":"France","zip":12345},"married":true,"conferences":["JavaOne","Gr8conf"]}}}'
 

Authors:

Guillaume Laforge

Since:

1.8.0

content

def content

Resulting data structure made of lists and maps, representing a JSON payload

JsonBuilder

JsonBuilder(def content = null)

Instanciates a JSON builder, possibly with some existing data structure.

Parameters:

content - a pre-existing data structure, default to null

call

def call(Map m)

Named arguments can be passed to the JSON builder instance to create a root JSON object

Example:

 def json = new JsonBuilder()
 json name: "Guillaume", age: 33

 assert json.toString() == '{"name":"Guillaume","age":33}'
 

Parameters:

m - a map of key / value pairs

Returns:

a map of key / value pairs

call

def call(List l)

A list of elements as arguments to the JSON builder creates a root JSON array

Example:

 def json = new JsonBuilder()
 def result = json([1, 2, 3])

 assert result instanceof List
 assert json.toString() == "[1,2,3]"
 

Parameters:

l - a list of values

Returns:

a list of values

call

def call(Object... args)

Varargs elements as arguments to the JSON builder create a root JSON array

Example:

 def json = new JsonBuilder()
 def result = json 1, 2, 3

 assert result instanceof List
 assert json.toString() == "[1,2,3]"
 

Parameters:

args - an array of values

Returns:

a list of values

call

def call(Closure c)

A closure passed to a JSON builder will create a root JSON object

Example:

 def json = new JsonBuilder()
 def result = json {
      name "Guillaume"
      age 33
 }

 assert result instanceof Map
 assert json.toString() == '{"name":"Guillaume","age":33}'
 

Parameters:

c - a closure whose method call statements represent key / values of a JSON object

Returns:

a map of key / value pairs

invokeMethod

def invokeMethod(String name, Object args)

A method call on the JSON builder instance will create a root object with only one key whose name is the name of the method being called. This method takes as arguments:

• a closure
• a map (ie. named arguments)
• a map and a closure
• or no argument at all

Example with a classicala builder-style:

 def json = new JsonBuilder()
 def result = json.person {
      name "Guillaume"
      age 33
 }

 assert result instanceof Map
 assert json.toString() == '{"person":{"name":"Guillaume","age":33}}'
 

Or alternatively with a method call taking named arguments:

 def json = new JsonBuilder()
 json.person name: "Guillaume", age: 33

 assert json.toString() == '{"person":{"name":"Guillaume","age":33}}'
 

If you use named arguments and a closure as last argument, the key/value pairs of the map (as named arguments) and the key/value pairs represented in the closure will be merged together — the closure properties overriding the map key/values in case the same key is used.

 def json = new JsonBuilder()
 json.person(name: "Guillaume", age: 33) { town "Paris" }

 assert json.toString() == '{"person":{"name":"Guillaume","age":33,"town":"Paris"}}'
 

The empty args call will create a key whose value will be an empty JSON object:

 def json = new JsonBuilder()
 json.person()

 assert json.toString() == '{"person":{}}'
 

Parameters:

name - the single key

args - the value associated with the key

Returns:

a map with a single key

toPrettyString

String toPrettyString()

Pretty-prints and formats the JSON payload.

This method calls the JsonLexer to parser the output of the builder, so this may not be an optimal method to call, and should be used mainly for debugging purpose for a human-readable output of the JSON content.

Returns:

a pretty printed JSON output

toString

String toString()

Serializes the internal data structure built with the builder to a conformant JSON payload string

Example:

 def json = new JsonBuilder()
 json { temperature 37 }
 
 assert json.toString() == '{"temperature":37}'
 

Returns:

a JSON output

writeTo

Writer writeTo(Writer out)

The JSON builder implements the Writable interface, so that you can have the builder serialize itself the JSON payload to a writer.

Example:

 def json = new JsonBuilder()
 json { temperature 37 }

 def out = new StringWriter()
 out << json

 assert out.toString() == '{"temperature":37}' 
 

Parameters:

out - a writer on which to serialize the JSON payload

Returns:

the writer

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