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A Minimal JSON Parser and Writer
/*******************************************************************************
* Copyright (c) 2013, 2015 EclipseSource.
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in all
* copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE.
******************************************************************************/
package com.eclipsesource.json;
import java.io.IOException;
import java.io.Reader;
import java.io.Serializable;
import java.io.StringWriter;
import java.io.Writer;
/**
* Represents a JSON value. This can be a JSON object, an array,
* a number, a string, or one of the literals
* true, false, and null.
*
* The literals true, false, and null are
* represented by the constants {@link #TRUE}, {@link #FALSE}, and {@link #NULL}.
*
*
* JSON objects and arrays are represented by the subtypes
* {@link JsonObject} and {@link JsonArray}. Instances of these types can be created using the
* public constructors of these classes.
*
*
* Instances that represent JSON numbers, strings and
* boolean values can be created using the static factory methods
* {@link #valueOf(String)}, {@link #valueOf(long)}, {@link #valueOf(double)}, etc.
*
*
* In order to find out whether an instance of this class is of a certain type, the methods
* {@link #isObject()}, {@link #isArray()}, {@link #isString()}, {@link #isNumber()} etc. can be
* used.
*
*
* If the type of a JSON value is known, the methods {@link #asObject()}, {@link #asArray()},
* {@link #asString()}, {@link #asInt()}, etc. can be used to get this value directly in the
* appropriate target type.
*
*
* This class is not supposed to be extended by clients.
*
*/
@SuppressWarnings("serial") // use default serial UID
public abstract class JsonValue implements Serializable {
/**
* Represents the JSON literal true.
* @deprecated Use Json.TRUE instead
*/
@Deprecated
public static final JsonValue TRUE = Json.TRUE;
/**
* Represents the JSON literal false.
* @deprecated Use Json.FALSE instead
*/
@Deprecated
public static final JsonValue FALSE = Json.FALSE;
/**
* Represents the JSON literal null.
* @deprecated Use Json.NULL instead
*/
@Deprecated
public static final JsonValue NULL = Json.NULL;
JsonValue() {
// prevent subclasses outside of this package
}
/**
* Reads a JSON value from the given reader.
*
* Characters are read in chunks and buffered internally, therefore wrapping an existing reader in
* an additional BufferedReader does not improve reading
* performance.
*
*
* @param reader
* the reader to read the JSON value from
* @return the JSON value that has been read
* @throws IOException
* if an I/O error occurs in the reader
* @throws ParseException
* if the input is not valid JSON
* @deprecated Use {@link Json#parse(Reader)} instead
*/
@Deprecated
public static JsonValue readFrom(Reader reader) throws IOException {
return new JsonParser(reader).parse();
}
/**
* Reads a JSON value from the given string.
*
* @param text
* the string that contains the JSON value
* @return the JSON value that has been read
* @throws ParseException
* if the input is not valid JSON
* @deprecated Use {@link Json#parse(String)} instead
*/
@Deprecated
public static JsonValue readFrom(String text) {
try {
return new JsonParser(text).parse();
} catch (IOException exception) {
// JsonParser does not throw IOException for String
throw new RuntimeException(exception);
}
}
/**
* Returns a JsonValue instance that represents the given int value.
*
* @param value
* the value to get a JSON representation for
* @return a JSON value that represents the given value
* @deprecated Use Json.value() instead
*/
@Deprecated
public static JsonValue valueOf(int value) {
return Json.value(value);
}
/**
* Returns a JsonValue instance that represents the given long value.
*
* @param value
* the value to get a JSON representation for
* @return a JSON value that represents the given value
* @deprecated Use Json.value() instead
*/
@Deprecated
public static JsonValue valueOf(long value) {
return Json.value(value);
}
/**
* Returns a JsonValue instance that represents the given float value.
*
* @param value
* the value to get a JSON representation for
* @return a JSON value that represents the given value
* @deprecated Use Json.value() instead
*/
@Deprecated
public static JsonValue valueOf(float value) {
return Json.value(value);
}
/**
* Returns a JsonValue instance that represents the given double value.
*
* @param value
* the value to get a JSON representation for
* @return a JSON value that represents the given value
* @deprecated Use Json.value() instead
*/
@Deprecated
public static JsonValue valueOf(double value) {
return Json.value(value);
}
/**
* Returns a JsonValue instance that represents the given string.
*
* @param string
* the string to get a JSON representation for
* @return a JSON value that represents the given string
* @deprecated Use Json.value() instead
*/
@Deprecated
public static JsonValue valueOf(String string) {
return Json.value(string);
}
/**
* Returns a JsonValue instance that represents the given boolean value.
*
* @param value
* the value to get a JSON representation for
* @return a JSON value that represents the given value
* @deprecated Use Json.value() instead
*/
@Deprecated
public static JsonValue valueOf(boolean value) {
return Json.value(value);
}
/**
* Detects whether this value represents a JSON object. If this is the case, this value is an
* instance of {@link JsonObject}.
*
* @return true if this value is an instance of JsonObject
*/
public boolean isObject() {
return false;
}
/**
* Detects whether this value represents a JSON array. If this is the case, this value is an
* instance of {@link JsonArray}.
*
* @return true if this value is an instance of JsonArray
*/
public boolean isArray() {
return false;
}
/**
* Detects whether this value represents a JSON number.
*
* @return true if this value represents a JSON number
*/
public boolean isNumber() {
return false;
}
/**
* Detects whether this value represents a JSON string.
*
* @return true if this value represents a JSON string
*/
public boolean isString() {
return false;
}
/**
* Detects whether this value represents a boolean value.
*
* @return true if this value represents either the JSON literal true or
* false
*/
public boolean isBoolean() {
return false;
}
/**
* Detects whether this value represents the JSON literal true.
*
* @return true if this value represents the JSON literal true
*/
public boolean isTrue() {
return false;
}
/**
* Detects whether this value represents the JSON literal false.
*
* @return true if this value represents the JSON literal false
*/
public boolean isFalse() {
return false;
}
/**
* Detects whether this value represents the JSON literal null.
*
* @return true if this value represents the JSON literal null
*/
public boolean isNull() {
return false;
}
/**
* Returns this JSON value as {@link JsonObject}, assuming that this value represents a JSON
* object. If this is not the case, an exception is thrown.
*
* @return a JSONObject for this value
* @throws UnsupportedOperationException
* if this value is not a JSON object
*/
public JsonObject asObject() {
throw new UnsupportedOperationException("Not an object: " + toString());
}
/**
* Returns this JSON value as {@link JsonArray}, assuming that this value represents a JSON array.
* If this is not the case, an exception is thrown.
*
* @return a JSONArray for this value
* @throws UnsupportedOperationException
* if this value is not a JSON array
*/
public JsonArray asArray() {
throw new UnsupportedOperationException("Not an array: " + toString());
}
/**
* Returns this JSON value as an int value, assuming that this value represents a
* JSON number that can be interpreted as Java int. If this is not the case, an
* exception is thrown.
*
* To be interpreted as Java int, the JSON number must neither contain an exponent
* nor a fraction part. Moreover, the number must be in the Integer range.
*
*
* @return this value as int
* @throws UnsupportedOperationException
* if this value is not a JSON number
* @throws NumberFormatException
* if this JSON number can not be interpreted as int value
*/
public int asInt() {
throw new UnsupportedOperationException("Not a number: " + toString());
}
/**
* Returns this JSON value as a long value, assuming that this value represents a
* JSON number that can be interpreted as Java long. If this is not the case, an
* exception is thrown.
*
* To be interpreted as Java long, the JSON number must neither contain an exponent
* nor a fraction part. Moreover, the number must be in the Long range.
*
*
* @return this value as long
* @throws UnsupportedOperationException
* if this value is not a JSON number
* @throws NumberFormatException
* if this JSON number can not be interpreted as long value
*/
public long asLong() {
throw new UnsupportedOperationException("Not a number: " + toString());
}
/**
* Returns this JSON value as a float value, assuming that this value represents a
* JSON number. If this is not the case, an exception is thrown.
*
* If the JSON number is out of the Float range, {@link Float#POSITIVE_INFINITY} or
* {@link Float#NEGATIVE_INFINITY} is returned.
*
*
* @return this value as float
* @throws UnsupportedOperationException
* if this value is not a JSON number
*/
public float asFloat() {
throw new UnsupportedOperationException("Not a number: " + toString());
}
/**
* Returns this JSON value as a double value, assuming that this value represents a
* JSON number. If this is not the case, an exception is thrown.
*
* If the JSON number is out of the Double range, {@link Double#POSITIVE_INFINITY} or
* {@link Double#NEGATIVE_INFINITY} is returned.
*
*
* @return this value as double
* @throws UnsupportedOperationException
* if this value is not a JSON number
*/
public double asDouble() {
throw new UnsupportedOperationException("Not a number: " + toString());
}
/**
* Returns this JSON value as String, assuming that this value represents a JSON string. If this
* is not the case, an exception is thrown.
*
* @return the string represented by this value
* @throws UnsupportedOperationException
* if this value is not a JSON string
*/
public String asString() {
throw new UnsupportedOperationException("Not a string: " + toString());
}
/**
* Returns this JSON value as a boolean value, assuming that this value is either
* true or false. If this is not the case, an exception is thrown.
*
* @return this value as boolean
* @throws UnsupportedOperationException
* if this value is neither true or false
*/
public boolean asBoolean() {
throw new UnsupportedOperationException("Not a boolean: " + toString());
}
/**
* Writes the JSON representation of this value to the given writer in its minimal form, without
* any additional whitespace.
*
* Writing performance can be improved by using a {@link java.io.BufferedWriter BufferedWriter}.
*
*
* @param writer
* the writer to write this value to
* @throws IOException
* if an I/O error occurs in the writer
*/
public void writeTo(Writer writer) throws IOException {
writeTo(writer, WriterConfig.MINIMAL);
}
/**
* Writes the JSON representation of this value to the given writer using the given formatting.
*
* Writing performance can be improved by using a {@link java.io.BufferedWriter BufferedWriter}.
*
*
* @param writer
* the writer to write this value to
* @param config
* a configuration that controls the formatting or null for the minimal form
* @throws IOException
* if an I/O error occurs in the writer
*/
public void writeTo(Writer writer, WriterConfig config) throws IOException {
if (writer == null) {
throw new NullPointerException("writer is null");
}
if (config == null) {
throw new NullPointerException("config is null");
}
WritingBuffer buffer = new WritingBuffer(writer, 128);
write(config.createWriter(buffer));
buffer.flush();
}
/**
* Returns the JSON string for this value in its minimal form, without any additional whitespace.
* The result is guaranteed to be a valid input for the method {@link #readFrom(String)} and to
* create a value that is equal to this object.
*
* @return a JSON string that represents this value
*/
@Override
public String toString() {
return toString(WriterConfig.MINIMAL);
}
/**
* Returns the JSON string for this value using the given formatting.
*
* @param config
* a configuration that controls the formatting or null for the minimal form
* @return a JSON string that represents this value
*/
public String toString(WriterConfig config) {
StringWriter writer = new StringWriter();
try {
writeTo(writer, config);
} catch (IOException exception) {
// StringWriter does not throw IOExceptions
throw new RuntimeException(exception);
}
return writer.toString();
}
/**
* Indicates whether some other object is "equal to" this one according to the contract specified
* in {@link Object#equals(Object)}.
*
* Two JsonValues are considered equal if and only if they represent the same JSON text. As a
* consequence, two given JsonObjects may be different even though they contain the same set of
* names with the same values, but in a different order.
*
*
* @param object
* the reference object with which to compare
* @return true if this object is the same as the object argument; false otherwise
*/
@Override
public boolean equals(Object object) {
return super.equals(object);
}
@Override
public int hashCode() {
return super.hashCode();
}
abstract void write(JsonWriter writer) throws IOException;
}