Package: groovy.json

## [Java] Class JsonBuilder

- groovy.json.JsonBuilder

- All Implemented Interfaces and Traits:
    Writable

      public class JsonBuilder
      extends GroovyObjectSupport

  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
    Andrey Bloshetsov
  Since:
    1.8.0

- - ### Constructor Summary

    Constructors
    Constructor and description
    `JsonBuilder ()` Instantiates a JSON builder.
    `JsonBuilder (Object content)` Instantiates a JSON builder with some existing data structure.

  - ### Methods Summary

    Methods
    Type | Name and description
    --- | ---
    `Object` | `call(Map m)` Named arguments can be passed to the JSON builder instance to create a root JSON object
    `Object` | `call(List l)` A list of elements as arguments to the JSON builder creates a root JSON array
    `Object` | `call(Object... args)` Varargs elements as arguments to the JSON builder create a root JSON array
    `Object` | `call(Collection coll, Closure c)` A collection and closure passed to a JSON builder will create a root JSON array applying the closure to each object in the collection
    `Object` | `call(Closure c)` A closure passed to a JSON builder will create a root JSON object
    `Object` | `getContent()`
    `Object` | `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.
    `String` | `toPrettyString()` Pretty-prints and formats the JSON payload.
    `String` | `toString()` Serializes the internal data structure built with the builder to a conformant JSON payload string
    `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.

  - ### Inherited Methods Summary

    Inherited Methods
    Methods inherited from class | Name
    --- | ---
    `class GroovyObjectSupport` | `getMetaClass, getProperty, invokeMethod, setMetaClass, setProperty`
    `class Object` | `wait, wait, wait, equals, toString, hashCode, getClass, notify, notifyAll`

- - ### Constructor Detail

    - #### public JsonBuilder()

      Instantiates a JSON builder.

    - #### public JsonBuilder(Object content)

      Instantiates a JSON builder with some existing data structure.

      Parameters:
        `content` - a pre-existing data structure

  - ### Method Detail

    - #### public Object 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

    - #### public Object 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

    - #### public Object 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

    - #### public Object call(Collection coll, Closure c)

      A collection and closure passed to a JSON builder will create a root JSON array applying the closure to each object in the collection

      Example:

           class Author {
                String name
           }
           def authors = [new Author (name: "Guillaume"), new Author (name: "Jochen"), new Author (name: "Paul")]

           def json = new JsonBuilder()
           json authors, { Author author ->
                name author.name
           }

           assert json.toString() == '[{"name":"Guillaume"},{"name":"Jochen"},{"name":"Paul"}]'

      Parameters:
        `coll` - a collection
        `c` - a closure used to convert the objects of coll
      Returns:
        a list of values

    - #### public Object 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

    - #### public Object getContent()

    - #### public Object 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

    - #### public 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

    - #### public 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

    - #### public 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