org.springframework.extensions.webscripts.json

Class JSONWriter

java.lang.Object

org.springframework.extensions.webscripts.json.JSONWriter

public final class JSONWriter
extends Object

Fast and simple JSON stream writer. Wraps a Writer to output a JSON object stream. No intermediate objects are created - writes are immediate to the underlying stream. Quoted and correct JSON encoding is performed on string values, - encoding is not performed on key names - it is assumed they are simple strings. The developer must call JSONWriter.encodeJSONString() on the key name if required.

The JSON output is safe to be rendered directly into a "text/javascript" mimetype resource as all unicode characters that are not supported in JavaScript are encoded in hex \\uXXXX format.

Since:

1.0 Added improvements to support 'double' and 'long' datatype and all methods now return the current JSONWriter to allow chaining of calls for more succinct serialization code., 1.2 Improvements to handle NaN/Infinity in double/float processing. Added helpers to recursively encode a hierarchy of Java POJO objects (List, Map, basic data-types) into a JSON string.

Author:

Kevin Roast

Constructor Summary

Constructors

Constructor and Description
JSONWriter(Writer out) Constructor

Method Summary

Methods

Modifier and Type	Method and Description
static String	encodeJSONString(String s) Safely encode a JSON string value.
static String	encodeToJSON(Object obj) Encode a simple Java object structure to JSON text.
static void	encodeToJSON(Object obj, JSONWriter writer) Encode a simple Java object structure to JSON text.
JSONWriter	endArray() End an array structure.
JSONWriter	endObject() End an object structure.
JSONWriter	endValue() End a value that was started with startValue()
JSONWriter	startArray() Start an array structure, the endArray() method must be called later.
JSONWriter	startObject() Start an object structure, the endObject() method must be called later.
JSONWriter	startValue(String name) Start a value (outputs just a name key), the endValue() method must be called later.
JSONWriter	writeNullValue() Output a JSON null value.
JSONWriter	writeNullValue(String name) Output a JSON null value.
JSONWriter	writeRawValue(RawValue value) Output a JSON boolean value.
JSONWriter	writeValue(boolean value) Output a JSON boolean value.
JSONWriter	writeValue(double value) Output a JSON number value.
JSONWriter	writeValue(float value) Output a JSON number value.
JSONWriter	writeValue(int value) Output a JSON number value.
JSONWriter	writeValue(long value) Output a JSON number value.
JSONWriter	writeValue(String value) Output a JSON string value.
JSONWriter	writeValue(String name, boolean value) Output a JSON boolean name and value pair.
JSONWriter	writeValue(String name, double value) Output a JSON number name and value pair.
JSONWriter	writeValue(String name, float value) Output a JSON number name and value pair.
JSONWriter	writeValue(String name, int value) Output a JSON number name and value pair.
JSONWriter	writeValue(String name, long value) Output a JSON number name and value pair.
JSONWriter	writeValue(String name, String value) Output a JSON string name and value pair.

Methods inherited from class java.lang.Object

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

Constructor Detail

JSONWriter

public JSONWriter(Writer out)

Constructor

Parameters:

out - The Writer to immediately append values to (no internal buffering)

Method Detail

startArray

public JSONWriter startArray()
                      throws IOException

Start an array structure, the endArray() method must be called later. NOTE: Within the array, either output objects or use the single arg writeValue() method.

Throws:

IOException

endArray

public JSONWriter endArray()
                    throws IOException

End an array structure.

Throws:

IOException

startObject

public JSONWriter startObject()
                       throws IOException

Start an object structure, the endObject() method must be called later.

Throws:

IOException

endObject

public JSONWriter endObject()
                     throws IOException

End an object structure.

Throws:

IOException

startValue

public JSONWriter startValue(String name)
                      throws IOException

Start a value (outputs just a name key), the endValue() method must be called later. NOTE: follow with an array or object only.

Throws:

IOException

endValue

public JSONWriter endValue()

End a value that was started with startValue()

writeValue

public JSONWriter writeValue(String name,
                    String value)
                      throws IOException

Output a JSON string name and value pair.

Throws:

IOException

writeValue

public JSONWriter writeValue(String name,
                    int value)
                      throws IOException

Output a JSON number name and value pair.

Throws:

IOException

writeValue

public JSONWriter writeValue(String name,
                    long value)
                      throws IOException

Output a JSON number name and value pair.

Throws:

IOException

writeValue

public JSONWriter writeValue(String name,
                    float value)
                      throws IOException

Output a JSON number name and value pair.

Throws:

IOException

writeValue

public JSONWriter writeValue(String name,
                    double value)
                      throws IOException

Output a JSON number name and value pair.

Throws:

IOException

writeValue

public JSONWriter writeValue(String name,
                    boolean value)
                      throws IOException

Output a JSON boolean name and value pair.

Throws:

IOException

writeValue

public JSONWriter writeValue(String value)
                      throws IOException

Output a JSON string value. NOTE: no name is written - call from within an array structure.

Throws:

IOException

writeValue

public JSONWriter writeValue(int value)
                      throws IOException

Output a JSON number value. NOTE: no name is written - call from within an array structure.

Throws:

IOException

writeValue

public JSONWriter writeValue(long value)
                      throws IOException

Output a JSON number value. NOTE: no name is written - call from within an array structure.

Throws:

IOException

writeValue

public JSONWriter writeValue(float value)
                      throws IOException

Output a JSON number value. NOTE: no name is written - call from within an array structure.

Throws:

IOException

writeValue

public JSONWriter writeValue(double value)
                      throws IOException

Output a JSON number value. NOTE: no name is written - call from within an array structure.

Throws:

IOException

writeValue

public JSONWriter writeValue(boolean value)
                      throws IOException

Output a JSON boolean value. NOTE: no name is written - call from within an array structure.

Throws:

IOException

writeNullValue

public JSONWriter writeNullValue()
                          throws IOException

Output a JSON null value. NOTE: no name is written - call from within an array structure.

Throws:

IOException

writeNullValue

public JSONWriter writeNullValue(String name)
                          throws IOException

Output a JSON null value.

Throws:

IOException

writeRawValue

public JSONWriter writeRawValue(RawValue value)
                         throws IOException

Output a JSON boolean value. NOTE: no name is written - call from within an array structure.

Throws:

IOException

encodeToJSON

public static String encodeToJSON(Object obj)

Encode a simple Java object structure to JSON text.

Handles standard Java data types such as String, Boolean, Integer, Float, Double, null. Also deals with simple List as JSON Array and Map as JSON Object. Recursively processes lists and maps as needed.

Parameters:

obj - Java object of basic data types or List or Map.

Returns:

JSON string.

encodeToJSON

public static void encodeToJSON(Object obj,
                JSONWriter writer)
                         throws IOException

Encode a simple Java object structure to JSON text.

Handles standard Java data types such as String, Boolean, Integer, Float, Double, null. Also deals with simple List as JSON Array and Map as JSON Object. Recursively processes lists and maps as needed.

Parameters:

obj - Java object of basic data types or List or Map.

writer - JSONWriter for output

Throws:

IOException

encodeJSONString

public static String encodeJSONString(String s)

Safely encode a JSON string value.

Returns:

encoded string, null is handled and returned as "".