Package groovy.json

Class 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

    • Constructor Detail

      • JsonBuilder

        public JsonBuilder()
        Instantiates a JSON builder.

      • JsonBuilder

        public JsonBuilder​(JsonGenerator generator)
        Instantiates a JSON builder with a configured generator.
        Parameters:
        generator - used to generate the output
        Since:
        2.5.0

      • JsonBuilder

        public JsonBuilder​(Object content)
        Instantiates a JSON builder with some existing data structure.
        Parameters:
        content - a pre-existing data structure

      • JsonBuilder

        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

      • 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​(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 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":{}}'
        Specified by:
        invokeMethod in interface GroovyObject
        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