Module jakarta.json
Package jakarta.json.stream

Interface JsonGenerator

  • All Superinterfaces:
    AutoCloseable, Closeable, Flushable
    public interface JsonGenerator
extends Flushable, Closeable
    Writes JSON data to an output source in a streaming way. The class Json contains methods to create generators for character or output streams (Writer and OutputStream).

    The following example shows how to create a JSON generator: 

     
 JsonGenerator generator = Json.createGenerator(...);

    The class JsonGeneratorFactory also contains methods to create JsonGenerator instances. JsonGeneratorFactory should be used when creating multiple generator instances, as in the following example: 

     
 JsonGeneratorFactory factory = Json.createGeneratorFactory();
 JsonGenerator generator1 = factory.createGenerator(...);
 JsonGenerator generator2 = factory.createGenerator(...);

    JSON objects can be created using JsonGenerator by calling the writeStartObject() method and then adding name/value pairs with the write method.

    The following example shows how to generate an empty JSON object: 

     
 JsonGenerator generator = ...;
 generator.writeStartObject().writeEnd().close();
    JSON arrays can be created using JsonGenerator by calling the writeStartArray() method and then adding values with the write method.

    The following example shows how to generate an empty JSON array: 

     
 JsonGenerator generator = ...;
 generator.writeStartArray().writeEnd().close();

    Other JSON values (that are not JSON objects or arrays) can be created by calling the appropiate write methods.

    The following example shows how to generate a JSON string: 

    
 JsonGenerator generator = ...;
 generator.write("message").close();
    JsonGenerator methods can be chained as in the following example: 
     
 generator
     .writeStartObject()
         .write("firstName", "John")
         .write("lastName", "Smith")
         .write("age", 25)
         .writeStartObject("address")
             .write("streetAddress", "21 2nd Street")
             .write("city", "New York")
             .write("state", "NY")
             .write("postalCode", "10021")
         .writeEnd()
         .writeStartArray("phoneNumber")
             .writeStartObject()
                 .write("type", "home")
                 .write("number", "212 555-1234")
             .writeEnd()
             .writeStartObject()
                 .write("type", "fax")
                 .write("number", "646 555-4567")
             .writeEnd()
         .writeEnd()
     .writeEnd();
 generator.close();
    The example code above generates the following JSON (or equivalent): 
     
 {
   "firstName": "John", "lastName": "Smith", "age": 25,
   "address" : {
       "streetAddress": "21 2nd Street",
       "city": "New York",
       "state": "NY",
       "postalCode": "10021"
   },
   "phoneNumber": [
       {"type": "home", "number": "212 555-1234"},
       {"type": "fax", "number": "646 555-4567"}
    ]
 }
    The generated JSON text must strictly conform to the grammar defined in RFC 7159.
    See Also:
    Json, JsonGeneratorFactory

    • Field Detail

      • PRETTY_PRINTING

        static final String PRETTY_PRINTING
        Configuration property to generate JSON prettily. All providers must support this property. The value of the property could be be anything.
        See Also:
        Constant Field Values

    • Method Detail

      • writeStartObject

        JsonGenerator writeStartObject()
        Writes the JSON start object character. It starts a new child object context within which JSON name/value pairs can be written to the object. This method is valid only in an array context, field context or in no context (when a context is not yet started). This method can only be called once in no context.
        Returns:
        this generator
        Throws:
        JsonException - if an i/o error occurs (IOException would be cause of JsonException)
        JsonGenerationException - if this method is called within an object context or if it is called more than once in no context.

      • writeStartObject

        JsonGenerator writeStartObject​(String name)
        Writes the JSON name/start object character pair in the current object context. It starts a new child object context within which JSON name/value pairs can be written to the object.
        Parameters:
        name - a name within the JSON name/object pair to be written
        Returns:
        this generator
        Throws:
        JsonException - if an i/o error occurs (IOException would be cause of JsonException)
        JsonGenerationException - if this method is not called within an object context

      • writeKey

        JsonGenerator writeKey​(String name)
        Writes the JSON name with a colon. It starts a field context, in which valid options are writing a value, starting an object or an array. Writing value closes field context, if object or array is started after field name, field context will be closed after object/array close.
        Parameters:
        name - name of json field
        Returns:
        this generator
        Throws:
        JsonException - if an i/o error occurs (IOException would be cause of JsonException)
        JsonGenerationException - if this method is not called within an object context
        Since:
        1.1

      • writeStartArray

        JsonGenerator writeStartArray()
        Writes the JSON start array character. It starts a new child array context within which JSON values can be written to the array. This method is valid only in an array context, field context or in no context (when a context is not yet started). This method can only be called once in no context.
        Returns:
        this generator
        Throws:
        JsonException - if an i/o error occurs (IOException would be cause of JsonException)
        JsonGenerationException - if this method is called within an object context or if called more than once in no context

      • writeStartArray

        JsonGenerator writeStartArray​(String name)
        Writes the JSON name/start array character pair with in the current object context. It starts a new child array context within which JSON values can be written to the array.
        Parameters:
        name - a name within the JSON name/array pair to be written
        Returns:
        this generator
        Throws:
        JsonException - if an i/o error occurs (IOException would be cause of JsonException)
        JsonGenerationException - if this method is not called within an object context

      • write

        JsonGenerator write​(String name,
                    JsonValue value)
        Writes a JSON name/value pair in the current object context.
        Parameters:
        name - a name in the JSON name/value pair to be written in current JSON object
        value - a value in the JSON name/value pair to be written in current JSON object
        Returns:
        this generator
        Throws:
        JsonException - if an i/o error occurs (IOException would be cause of JsonException)
        JsonGenerationException - if this method is not called within an object context

      • write

        JsonGenerator write​(String name,
                    String value)
        Writes a JSON name/string value pair in the current object context. The specified value is written as JSON string value.
        Parameters:
        name - a name in the JSON name/string pair to be written in current JSON object
        value - a value in the JSON name/string pair to be written in current JSON object
        Returns:
        this generator
        Throws:
        JsonException - if an i/o error occurs (IOException would be cause of JsonException)
        JsonGenerationException - if this method is not called within an object context

      • write

        JsonGenerator write​(String name,
                    BigInteger value)
        Writes a JSON name/number value pair in the current object context. The specified value is written as a JSON number value. The string new BigDecimal(value).toString() is used as the text value for writing.
        Parameters:
        name - a name in the JSON name/number pair to be written in current JSON object
        value - a value in the JSON name/number pair to be written in current JSON object
        Returns:
        this generator
        Throws:
        JsonException - if an i/o error occurs (IOException would be cause of JsonException)
        JsonGenerationException - if this method is not called within an object context.

      • write

        JsonGenerator write​(String name,
                    BigDecimal value)
        Writes a JSON name/number value pair in the current object context. The specified value is written as a JSON number value. The specified value's toString() is used as the text value for writing.
        Parameters:
        name - a name in the JSON name/number pair to be written in current JSON object
        value - a value in the JSON name/number pair to be written in current JSON object
        Returns:
        this generator
        Throws:
        JsonException - if an i/o error occurs (IOException would be cause of JsonException)
        JsonGenerationException - if this method is not called within an object context.

      • write

        JsonGenerator write​(String name,
                    int value)
        Writes a JSON name/number value pair in the current object context. The specified value is written as a JSON number value. The string new BigDecimal(value).toString() is used as the text value for writing.
        Parameters:
        name - a name in the JSON name/number pair to be written in current JSON object
        value - a value in the JSON name/number pair to be written in current JSON object
        Returns:
        this generator
        Throws:
        JsonException - if an i/o error occurs (IOException would be cause of JsonException)
        JsonGenerationException - if this method is not called within an object context.

      • write

        JsonGenerator write​(String name,
                    long value)
        Writes a JSON name/number value pair in the current object context. The specified value is written as a JSON number value. The string new BigDecimal(value).toString() is used as the text value for writing.
        Parameters:
        name - a name in the JSON name/number pair to be written in current JSON object
        value - a value in the JSON name/number pair to be written in current JSON object
        Returns:
        this generator
        Throws:
        JsonException - if an i/o error occurs (IOException would be cause of JsonException)
        JsonGenerationException - if this method is not called within an object context.

      • write

        JsonGenerator write​(String name,
                    double value)
        Writes a JSON name/number value pair in the current object context. The specified value is written as a JSON number value. The string BigDecimal.valueOf(double).toString() is used as the text value for writing.
        Parameters:
        name - a name in the JSON name/number pair to be written in current JSON object
        value - a value in the JSON name/number pair to be written in current JSON object
        Returns:
        this generator
        Throws:
        JsonException - if an i/o error occurs (IOException would be cause of JsonException)
        NumberFormatException - if the value is Not-a-Number (NaN) or infinity.
        JsonGenerationException - if this method is not called within an object context

      • write

        JsonGenerator write​(String name,
                    boolean value)
        Writes a JSON name/boolean value pair in the current object context. If value is true, it writes the JSON true value, otherwise it writes the JSON false value.
        Parameters:
        name - a name in the JSON name/boolean pair to be written in current JSON object
        value - a value in the JSON name/boolean pair to be written in current JSON object
        Returns:
        this generator
        Throws:
        JsonException - if an i/o error occurs (IOException would be cause of JsonException)
        JsonGenerationException - if this method is not called within an object context.

      • writeNull

        JsonGenerator writeNull​(String name)
        Writes a JSON name/null value pair in an current object context.
        Parameters:
        name - a name in the JSON name/null pair to be written in current JSON object
        Returns:
        this generator
        Throws:
        JsonException - if an i/o error occurs (IOException would be cause of JsonException)
        JsonGenerationException - if this method is not called within an object context

      • writeEnd

        JsonGenerator writeEnd()
        Writes the end of the current context. If the current context is an array context, this method writes the end-of-array character (']'). If the current context is an object context, this method writes the end-of-object character ('}'). After writing the end of the current context, the parent context becomes the new current context. If parent context is field context, it is closed.
        Returns:
        this generator
        Throws:
        JsonException - if an i/o error occurs (IOException would be cause of JsonException)
        JsonGenerationException - if this method is called in no context.

      • write

        JsonGenerator write​(JsonValue value)
        Writes the specified value as a JSON value within the current array, field or root context.
        Parameters:
        value - a value to be written in current JSON array
        Returns:
        this generator
        Throws:
        JsonException - if an i/o error occurs (IOException would be cause of JsonException)
        JsonGenerationException - if this method is not called within an array, root or field context.

      • write

        JsonGenerator write​(String value)
        Writes the specified value as a JSON string value within the current array, field or root context.
        Parameters:
        value - a value to be written in current JSON array
        Returns:
        this generator
        Throws:
        JsonException - if an i/o error occurs (IOException would be cause of JsonException)
        JsonGenerationException - if this method is not called within an array, root or field context.

      • write

        JsonGenerator write​(BigDecimal value)
        Writes the specified value as a JSON number value within the current array, field or root context. The specified value's toString() is used as the the text value for writing.
        Parameters:
        value - a value to be written in current JSON array
        Returns:
        this generator
        Throws:
        JsonException - if an i/o error occurs (IOException would be cause of JsonException)
        JsonGenerationException - if this method is not called within an array, root or field context.
        See Also:
        JsonNumber

      • write

        JsonGenerator write​(BigInteger value)
        Writes the specified value as a JSON number value within the current array, field or root context. The string new BigDecimal(value).toString() is used as the text value for writing.
        Parameters:
        value - a value to be written in current JSON array
        Returns:
        this generator.
        Throws:
        JsonException - if an i/o error occurs (IOException would be cause of JsonException)
        JsonGenerationException - if this method is not called within an array, root or field context.
        See Also:
        JsonNumber

      • write

        JsonGenerator write​(int value)
        Writes the specified value as a JSON number value within the current array, field or root context. The string new BigDecimal(value).toString() is used as the text value for writing.
        Parameters:
        value - a value to be written in current JSON array
        Returns:
        this generator
        Throws:
        JsonException - if an i/o error occurs (IOException would be cause of JsonException)
        JsonGenerationException - if this method is not called within an array, root or field context.

      • write

        JsonGenerator write​(long value)
        Writes the specified value as a JSON number value within the current array, field or root context. The string new BigDecimal(value).toString() is used as the text value for writing.
        Parameters:
        value - a value to be written in current JSON array
        Returns:
        this generator
        Throws:
        JsonException - if an i/o error occurs (IOException would be cause of JsonException)
        JsonGenerationException - if this method is not called within an array, root or field context.

      • write

        JsonGenerator write​(double value)
        Writes the specified value as a JSON number value within the current array, field or root context. The string BigDecimal.valueOf(value).toString() is used as the text value for writing.
        Parameters:
        value - a value to be written in current JSON array
        Returns:
        this generator
        Throws:
        JsonException - if an i/o error occurs (IOException would be cause of JsonException)
        JsonGenerationException - if this method is not called within an array, root or field context.
        NumberFormatException - if the value is Not-a-Number (NaN) or infinity.

      • write

        JsonGenerator write​(boolean value)
        Writes a JSON true or false value within the current array, field or root context. If value is true, this method writes the JSON true value, otherwise it writes the JSON false value.
        Parameters:
        value - a boolean value
        Returns:
        this generator
        Throws:
        JsonException - if an i/o error occurs (IOException would be cause of JsonException)
        JsonGenerationException - if this method is not called within an array, root or field context.

      • writeNull

        JsonGenerator writeNull()
        Writes a JSON null value within the current array, field or root context.
        Returns:
        this generator
        Throws:
        JsonException - if an i/o error occurs (IOException would be cause of JsonException)
        JsonGenerationException - if this method is not called within an array, root or field context.

      • close

        void close()
        Closes this generator and frees any resources associated with it. This method closes the underlying output source. The underlying stream is closed only if complete JSON object is written. In case of incomplete object JsonGenerationException is thrown and underlying stream is not closed.
        Specified by:
        close in interface AutoCloseable
        Specified by:
        close in interface Closeable
        Throws:
        JsonException - if an i/o error occurs (IOException would be cause of JsonException)
        JsonGenerationException - if an incomplete JSON is generated

      • flush

        void flush()
        Flushes the underlying output source. If the generator has saved any characters in a buffer, writes them immediately to the underlying output source before flushing it.
        Specified by:
        flush in interface Flushable
        Throws:
        JsonException - if an i/o error occurs (IOException would be cause of JsonException)