Package groovy.json

# Class StreamingJsonBuilder

java.lang.Object
groovy.lang.GroovyObjectSupport
groovy.json.StreamingJsonBuilder

All Implemented Interfaces:
  `GroovyObject`

public class StreamingJsonBuilder 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.

Unlike the JsonBuilder class which creates a data structure in memory, which is handy in those situations where you want to alter the structure programatically before output, the StreamingJsonBuilder streams to a writer directly without any memory data structure. So if you don't need to modify the structure, and want a more memory-efficient approach, please use the StreamingJsonBuilder.

Example:

         new StringWriter().with { w ->
             def builder = new groovy.json.StreamingJsonBuilder(w)
             builder.people {
                 person {
                     firstName 'Tim'
                     lastName 'Yates'
                     // Named arguments are valid values for objects too
                     address(
                         city: 'Manchester',
                         country: 'UK',
                         zip: 'M1 2AB',
                     )
                     living true
                     eyes 'left', 'right'
                 }
             }

             assert w.toString() == '{"people":{"person":{"firstName":"Tim","lastName":"Yates","address":{"city":"Manchester","country":"UK","zip":"M1 2AB"},"living":true,"eyes":["left","right"]}}}'
        }

Since:
  1.8.1

- ## Nested Class Summary

  Nested Classes
  Modifier and Type
  Class
  Description
  `static class`
  `StreamingJsonBuilder.StreamingJsonDelegate`
  The delegate used when invoking closures

- ## Constructor Summary

  Constructors
  Constructor
  Description
  `StreamingJsonBuilder(Writer writer)`
  Instantiates a JSON builder.
  `StreamingJsonBuilder(Writer writer, JsonGenerator generator)`
  Instantiates a JSON builder with the given generator.
  `StreamingJsonBuilder(Writer writer, Object content)`
  Instantiates a JSON builder, possibly with some existing data structure.
  `StreamingJsonBuilder(Writer writer, Object content, JsonGenerator generator)`
  Instantiates a JSON builder, possibly with some existing data structure and the given generator.

- ## Method Summary

  Modifier and Type
  Method
  Description
  `Object`
  `call(Closure c)`
  A closure passed to a JSON builder will create a root JSON object
  `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(Object... args)`
  Varargs elements as arguments to the JSON builder create a root JSON array
  `void`
  `call(String name)`
  The empty args call will create a key whose value will be an empty JSON object:
  `void`
  `call(String name, Closure c)`
  A name and a closure passed to a JSON builder will create a key with a JSON object
  `void`
  `call(String name, Iterable coll, Closure c)`
  A name, a collection and closure passed to a JSON builder will create a root JSON array applying the closure to each object in the collection
  `void`
  `call(String name, Collection coll, Closure c)`
  Delegates to `call(String, Iterable, Closure)`
  `void`
  `call(String name, Map map, Closure callable)`
  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.
  `Object`
  `call(Collection coll, Closure c)`
  Delegates to `call(Iterable, Closure)`
  `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`
  `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.

  ### Methods inherited from class groovy.lang.GroovyObjectSupport

  `getMetaClass, setMetaClass`

  ### Methods inherited from class java.lang.Object

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

  ### Methods inherited from interface groovy.lang.GroovyObject

  `getProperty, setProperty`

- ## Constructor Details

  - ### StreamingJsonBuilder

    public StreamingJsonBuilder(Writer writer)
    Instantiates a JSON builder.
    Parameters:
      `writer` - A writer to which Json will be written

  - ### StreamingJsonBuilder

    public StreamingJsonBuilder(Writer writer, JsonGenerator generator)
    Instantiates a JSON builder with the given generator.
    Parameters:
      `writer` - A writer to which Json will be written
      `generator` - used to generate the output
    Since:
      2.5.0

  - ### StreamingJsonBuilder

    public StreamingJsonBuilder(Writer writer, Object content) throws IOException
    Instantiates a JSON builder, possibly with some existing data structure.
    Parameters:
      `writer` - A writer to which Json will be written
      `content` - a pre-existing data structure, default to null
    Throws:
      `IOException`

  - ### StreamingJsonBuilder

    public StreamingJsonBuilder(Writer writer, Object content, JsonGenerator generator) throws IOException
    Instantiates a JSON builder, possibly with some existing data structure and the given generator.
    Parameters:
      `writer` - A writer to which Json will be written
      `content` - a pre-existing data structure, default to null
      `generator` - used to generate the output
    Throws:
      `IOException`
    Since:
      2.5.0

- ## Method Details

  - ### call

    public Object call(Map m) throws IOException
    Named arguments can be passed to the JSON builder instance to create a root JSON object

    Example:

         new StringWriter().with { w ->
           def json = new groovy.json.StreamingJsonBuilder(w)
           json name: "Tim", age: 31

           assert w.toString() == '{"name":"Tim","age":31}'
         }

    Parameters:
      `m` - a map of key / value pairs
    Returns:
      a map of key / value pairs
    Throws:
      `IOException`

  - ### call

    public void call(String name) throws IOException
    The empty args call will create a key whose value will be an empty JSON object:

         new StringWriter().with { w ->
             def json = new groovy.json.StreamingJsonBuilder(w)
             json.person()

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

    Parameters:
      `name` - The name of the empty object to create
    Throws:
      `IOException`

  - ### call

    public Object call(List l) throws IOException
    A list of elements as arguments to the JSON builder creates a root JSON array

    Example:

         new StringWriter().with { w ->
           def json = new groovy.json.StreamingJsonBuilder(w)
           def result = json([1, 2, 3])

           assert result == [ 1, 2, 3 ]
           assert w.toString() == "[1,2,3]"
         }

    Parameters:
      `l` - a list of values
    Returns:
      a list of values
    Throws:
      `IOException`

  - ### call

    public Object call(Object... args) throws IOException
    Varargs elements as arguments to the JSON builder create a root JSON array

    Example:

         new StringWriter().with { w ->
           def json = new groovy.json.StreamingJsonBuilder(w)
           def result = json 1, 2, 3

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

    Parameters:
      `args` - an array of values
    Returns:
      a list of values
    Throws:
      `IOException`

  - ### call

    public Object call(Iterable coll, @DelegatesTo(value=StreamingJsonDelegate.class,strategy=1) Closure c) throws IOException
    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")]

         new StringWriter().with { w ->
             def json = new groovy.json.StreamingJsonBuilder(w)
             json authors, { Author author ->
                 name author.name
             }

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

    Parameters:
      `coll` - a collection
      `c` - a closure used to convert the objects of coll
    Throws:
      `IOException`

  - ### call

    public Object call(Collection coll, @DelegatesTo(value=StreamingJsonDelegate.class,strategy=1) Closure c) throws IOException
    Delegates to `call(Iterable, Closure)`
    Throws:
      `IOException`

  - ### call

    public Object call(@DelegatesTo(value=StreamingJsonDelegate.class,strategy=1) Closure c) throws IOException
    A closure passed to a JSON builder will create a root JSON object

    Example:

         new StringWriter().with { w ->
           def json = new groovy.json.StreamingJsonBuilder(w)
           json {
              name "Tim"
              age 39
           }

           assert w.toString() == '{"name":"Tim","age":39}'
         }

    Parameters:
      `c` - a closure whose method call statements represent key / values of a JSON object
    Throws:
      `IOException`

  - ### call

    public void call(String name, @DelegatesTo(value=StreamingJsonDelegate.class,strategy=1) Closure c) throws IOException
    A name and a closure passed to a JSON builder will create a key with a JSON object

    Example:

         new StringWriter().with { w ->
           def json = new groovy.json.StreamingJsonBuilder(w)
           json.person {
              name "Tim"
              age 39
           }

           assert w.toString() == '{"person":{"name":"Tim","age":39}}'
         }

    Parameters:
      `name` - The key for the JSON object
      `c` - a closure whose method call statements represent key / values of a JSON object
    Throws:
      `IOException`

  - ### call

    public void call(String name, Iterable coll, @DelegatesTo(value=StreamingJsonDelegate.class,strategy=1) Closure c) throws IOException
    A name, 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")]

         new StringWriter().with { w ->
             def json = new groovy.json.StreamingJsonBuilder(w)
             json.people authors, { Author author ->
                 name author.name
             }

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

    Parameters:
      `coll` - a collection
      `c` - a closure used to convert the objects of coll
    Throws:
      `IOException`

  - ### call

    public void call(String name, Collection coll, @DelegatesTo(value=StreamingJsonDelegate.class,strategy=1) Closure c) throws IOException
    Delegates to `call(String, Iterable, Closure)`
    Throws:
      `IOException`

  - ### call

    public void call(String name, Map map, @DelegatesTo(value=StreamingJsonDelegate.class,strategy=1) Closure callable) throws IOException
    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.

         new StringWriter().with { w ->
             def json = new groovy.json.StreamingJsonBuilder(w)
             json.person(name: "Tim", age: 35) { town "Manchester" }

             assert w.toString() == '{"person":{"name":"Tim","age":35,"town":"Manchester"}}'
         }

    Parameters:
      `name` - The name of the JSON object
      `map` - The attributes of the JSON object
      `callable` - Additional attributes of the JSON object represented by the closure
    Throws:
      `IOException`

  - ### 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:

         new StringWriter().with { w ->
             def json = new groovy.json.StreamingJsonBuilder(w)
             json.person {
                 name "Tim"
                  age 28
             }

             assert w.toString() == '{"person":{"name":"Tim","age":28}}'
         }

    Or alternatively with a method call taking named arguments:

         new StringWriter().with { w ->
             def json = new groovy.json.StreamingJsonBuilder(w)
             json.person name: "Tim", age: 32

             assert w.toString() == '{"person":{"name":"Tim","age":32}}'
         }

    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.

         new StringWriter().with { w ->
             def json = new groovy.json.StreamingJsonBuilder(w)
             json.person(name: "Tim", age: 35) { town "Manchester" }

             assert w.toString() == '{"person":{"name":"Tim","age":35,"town":"Manchester"}}'
         }

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

         new StringWriter().with { w ->
             def json = new groovy.json.StreamingJsonBuilder(w)
             json.person()

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

    Parameters:
      `name` - the single key
      `args` - the value associated with the key
    Returns:
      the result of invoking the method