groovy.json

Class JsonBuilder

java.lang.Object

groovy.lang.GroovyObjectSupport

groovy.json.JsonBuilder

All Implemented Interfaces:

GroovyObject, Writable

public class JsonBuilder
extends GroovyObjectSupport
implements Writable

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"]}}}'
 

Since:

1.8.0

Author:

Guillaume Laforge, Andrey Bloshetsov

Constructor Summary

Constructors

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

Method Summary

Methods

Modifier and Type	Method and Description
Object	call(Closure c) A closure passed to a JSON builder will create a root JSON object
Object	call(Collection coll, Closure c) Delegates to call(Iterable, Closure)
Object	call(Iterable 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(List l) A list of elements as arguments to the JSON builder creates a root JSON array
Object	call(Map m) Named arguments can be passed to the JSON builder instance to create a root JSON object
Object	call(Object... args) Varargs elements as arguments to the JSON builder create a root JSON array
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.

Methods inherited from class groovy.lang.GroovyObjectSupport

getMetaClass, getProperty, setMetaClass, setProperty

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Constructor Detail

JsonBuilder

public JsonBuilder()

Instantiates a JSON builder.

JsonBuilder

public JsonBuilder(Object content)

Instantiates a JSON builder with some existing data structure.

Parameters:

content - a pre-existing data structure

Method Detail

getContent

public Object getContent()

call

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 groovy.json.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

public Object call(List l)

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

Example:

 def json = new groovy.json.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

public Object call(Object... args)

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

Example:

 def json = new groovy.json.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

public Object call(Iterable 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 groovy.json.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

call

public Object call(Collection coll,
          Closure c)

Delegates to call(Iterable, Closure)

call

public Object call(Closure c)

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

Example:

 def json = new groovy.json.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

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 groovy.json.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 groovy.json.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 groovy.json.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 groovy.json.JsonBuilder()
 json.person()

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

Specified by:

invokeMethod in interface GroovyObject

Overrides:

invokeMethod in class GroovyObjectSupport

Parameters:

name - the single key

args - the value associated with the key

Returns:

a map with a single key

toString

public String toString()

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

Example:

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

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

Overrides:

toString in class Object

Returns:

a JSON output

toPrettyString

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

writeTo

public Writer writeTo(Writer out)
               throws IOException

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 groovy.json.JsonBuilder()
 json { temperature 37 }

 def out = new StringWriter()
 out << json

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

Specified by:

writeTo in interface Writable

Parameters:

out - a writer on which to serialize the JSON payload

Returns:

the writer

Throws:

IOException - if an error occurred while outputting data to the writer