[Java] Class JsonBuilder

public class JsonBuilder
extends GroovyObjectSupport
implements Writable

       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"]}}}'
 

Constructor Detail

public JsonBuilder()

Instantiates a JSON builder.

public JsonBuilder(JsonGenerator generator)

Instantiates a JSON builder with a configured generator.

Parameters:

generator - used to generate the output

Since:

2.5.0

public JsonBuilder(Object content)

Instantiates a JSON builder with some existing data structure.

Parameters:

content - a pre-existing data structure

public JsonBuilder(Object content, JsonGenerator generator)

Instantiates a JSON builder with some existing data structure and a configured generator.

Parameters:

content - a pre-existing data structure

generator - used to generate the output

Since:

2.5.0

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 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

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

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

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

public Object call(Collection coll, Closure c)

Delegates to call(Iterable, Closure)

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

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 classical 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":{}}'
 

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 groovy.json.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 groovy.json.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