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/******************************************************************************* * Copyright (c) 2008, 2013 EclipseSource. * All rights reserved. This program and the accompanying materials * are made available under the terms of the Eclipse Public License v1.0 * which accompanies this distribution, and is available at * http://www.eclipse.org/legal/epl-v10.html *//from w w w.j a va 2 s.c o m * Contributors: * Ralf Sternberg - initial implementation and API ******************************************************************************/ package com.denzyldick.square.json; import java.io.IOException; import java.io.Reader; import java.io.Serializable; import java.io.StringReader; import java.io.StringWriter; import java.io.Writer; /** * Represents a JSON value. According to RFC 4627, a JSON value must be an <strong>object</strong>, * an <strong>array</strong>, a <strong>number</strong>, a <strong>string</strong>, or one of the * literal names <strong>true</strong>, <strong>false</strong>, and <strong>null</strong>. * <p> * The literal names <strong>true</strong>, <strong>false</strong>, and <strong>null</strong> are * represented by the constants {@link #TRUE}, {@link #FALSE}, and {@link #NULL}. * </p> * <p> * JSON <strong>objects</strong> and <strong>arrays</strong> are represented by the subtypes * {@link JsonObject} and {@link JsonArray}. Instances of these types can be created using the * public constructors. * </p> * <p> * Instances for JSON <strong>numbers</strong> and <strong>strings</strong> can be created using the * static factory methods {@link #valueOf(String)}, {@link #valueOf(long)}, {@link #valueOf(double)} * , etc. * </p> * <p> * 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. * </p> * <p> * If there is no doubt about the type of a JSON value, one of the methods {@link #asObject()}, * {@link #asArray()}, {@link #asString()}, {@link #asInt()}, etc. can be used to get this value * directly in the appropriate target type. * </p> * <p> * This class is <strong>not supposed to be extended</strong> by clients. * </p> */ @SuppressWarnings( "serial" ) // use default serial UID public abstract class JsonValue implements Serializable { /** * Represents the JSON literal <code>true</code>. */ public static final JsonValue TRUE = new JsonLiteral( "true" ); /** * Represents the JSON literal <code>false</code>. */ public static final JsonValue FALSE = new JsonLiteral( "false" ); /** * The JSON literal <code>null</code>. */ public static final JsonValue NULL = new JsonLiteral( "null" ); JsonValue() { // prevent subclasses outside of this package } /** * Reads a JSON value from the given reader. * * @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 */ 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 */ public static JsonValue readFrom( String text ) { try { return new JsonParser( new StringReader( text ) ).parse(); } catch( IOException exception ) { // StringReader does not throw IOException throw new RuntimeException( exception ); } } /** * Returns a JsonValue instance that represents the given <code>int</code> value. * * @param value * the value to get a JSON representation for * @return a JSON value that represents the given value */ public static JsonValue valueOf( int value ) { return new JsonNumber( Integer.toString( value, 10 ) ); } /** * Returns a JsonValue instance that represents the given <code>long</code> value. * * @param value * the value to get a JSON representation for * @return a JSON value that represents the given value */ public static JsonValue valueOf( long value ) { return new JsonNumber( Long.toString( value, 10 ) ); } /** * Returns a JsonValue instance that represents the given <code>float</code> value. * * @param value * the value to get a JSON representation for * @return a JSON value that represents the given value */ public static JsonValue valueOf( float value ) { if( Float.isInfinite( value ) || Float.isNaN( value ) ) { throw new IllegalArgumentException( "Infinite and NaN values not permitted in JSON" ); } return new JsonNumber( cutOffPointZero( Float.toString( value ) ) ); } /** * Returns a JsonValue instance that represents the given <code>double</code> value. * * @param value * the value to get a JSON representation for * @return a JSON value that represents the given value */ public static JsonValue valueOf( double value ) { if( Double.isInfinite( value ) || Double.isNaN( value ) ) { throw new IllegalArgumentException( "Infinite and NaN values not permitted in JSON" ); } return new JsonNumber( cutOffPointZero( Double.toString( 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 */ public static JsonValue valueOf( String string ) { return string == null ? NULL : new JsonString( string ); } /** * Returns a JsonValue instance that represents the given <code>boolean</code> value. * * @param value * the value to get a JSON representation for * @return a JSON value that represents the given value */ public static JsonValue valueOf( boolean value ) { return value ? TRUE : FALSE; } /** * Detects whether this value represents a JSON object. If this is the case, this value is an * instance of {@link JsonObject}. * * @return <code>true</code> 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 <code>true</code> if this value is an instance of JsonArray */ public boolean isArray() { return false; } /** * Detects whether this value represents a JSON number. * * @return <code>true</code> if this value represents a JSON number */ public boolean isNumber() { return false; } /** * Detects whether this value represents a JSON string. * * @return <code>true</code> if this value represents a JSON string */ public boolean isString() { return false; } /** * Detects whether this value represents a boolean value. * * @return <code>true</code> if this value represents either the JSON literal * <code>true</code> or <code>false</code> */ public boolean isBoolean() { return false; } /** * Detects whether this value represents the JSON literal <code>true</code>. * * @return <code>true</code> if this value represents the JSON literal * <code>true</code> */ public boolean isTrue() { return false; } /** * Detects whether this value represents the JSON literal <code>false</code>. * * @return <code>true</code> if this value represents the JSON literal * <code>false</code> */ public boolean isFalse() { return false; } /** * Detects whether this value represents the JSON literal <code>null</code>. * * @return <code>true</code> if this value represents the JSON literal * <code>null</code> */ 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 <code>int</code> value, assuming that this value represents a * JSON number that can be interpreted as Java <code>int</code>. If this is not the case, an * exception is thrown. * <p> * To be interpreted as Java <code>int</code>, the JSON number must neither contain an exponent * nor a fraction part. Moreover, the number must be in the <code>Integer</code> range. * </p> * * @return this value as <code>int</code> * @throws UnsupportedOperationException * if this value is not a JSON number * @throws NumberFormatException * if this JSON number can not be interpreted as <code>int</code> value */ public int asInt() { throw new UnsupportedOperationException( "Not a number: " + toString() ); } /** * Returns this JSON value as a <code>long</code> value, assuming that this value represents a * JSON number that can be interpreted as Java <code>long</code>. If this is not the case, an * exception is thrown. * <p> * To be interpreted as Java <code>long</code>, the JSON number must neither contain an exponent * nor a fraction part. Moreover, the number must be in the <code>Long</code> range. * </p> * * @return this value as <code>long</code> * @throws UnsupportedOperationException * if this value is not a JSON number * @throws NumberFormatException * if this JSON number can not be interpreted as <code>long</code> value */ public long asLong() { throw new UnsupportedOperationException( "Not a number: " + toString() ); } /** * Returns this JSON value as a <code>float</code> value, assuming that this value represents a * JSON number. If this is not the case, an exception is thrown. * <p> * If the JSON number is out of the <code>Float</code> range, {@link Float#POSITIVE_INFINITY} or * {@link Float#NEGATIVE_INFINITY} is returned. * </p> * * @return this value as <code>float</code> * @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 <code>double</code> value, assuming that this value represents a * JSON number. If this is not the case, an exception is thrown. * <p> * If the JSON number is out of the <code>Double</code> range, {@link Double#POSITIVE_INFINITY} or * {@link Double#NEGATIVE_INFINITY} is returned. * </p> * * @return this value as <code>double</code> * @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 <code>boolean</code> value, assuming that this value is either * <code>true</code> or <code>false</code>. If this is not the case, an exception is thrown. * * @return this value as <code>boolean</code> * @throws UnsupportedOperationException * if this value is neither <code>true</code> or <code>false</code> */ public boolean asBoolean() { throw new UnsupportedOperationException( "Not a boolean: " + toString() ); } /** * Writes the JSON representation for this object to the given writer. * * @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 { write( new JsonWriter( writer ) ); } /** * 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 <em>equal</em> to this object. * * @return a JSON string that represents this value */ @Override public String toString() { StringWriter stringWriter = new StringWriter(); JsonWriter jsonWriter = new JsonWriter( stringWriter ); try { write( jsonWriter ); } catch( IOException exception ) { // StringWriter does not throw IOExceptions throw new RuntimeException( exception ); } return stringWriter.toString(); } /** * Indicates whether some other object is "equal to" this one according to the contract specified * in {@link Object#equals(Object)}. * <p> * 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. * </p> * * @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(); } protected abstract void write( JsonWriter writer ) throws IOException; private static String cutOffPointZero( String string ) { if( string.endsWith( ".0" ) ) { return string.substring( 0, string.length() - 2 ); } return string; } }