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/* * Copyright (C) 2011 bedatadriven * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ package com.google.gson; import com.google.gwt.json.client.JSONValue; /** * A class representing an element of Json. It could either be a {@link JsonObject}, a * {@link JsonArray}, a {@link JsonPrimitive} or a {@link JsonNull}. * * @author Inderjeet Singh * @author Joel Leitch */ public abstract class JsonElement { /** * provides check for verifying if this element is an array or not. * * @return true if this element is of type {@link JsonArray}, false otherwise. */ public boolean isJsonArray() { return this instanceof JsonArray; } /** * provides check for verifying if this element is a Json object or not. * * @return true if this element is of type {@link JsonObject}, false otherwise. */ public boolean isJsonObject() { return this instanceof JsonObject; } /** * provides check for verifying if this element is a primitive or not. * * @return true if this element is of type {@link JsonPrimitive}, false otherwise. */ public boolean isJsonPrimitive() { return this instanceof JsonPrimitive; } /** * provides check for verifying if this element represents a null value or not. * * @return true if this element is of type {@link JsonNull}, false otherwise. * @since 1.2 */ public boolean isJsonNull() { return this instanceof JsonNull; } /** * convenience method to get this element as a {@link JsonObject}. If the element is of some * other type, a {@link ClassCastException} will result. Hence it is best to use this method * after ensuring that this element is of the desired type by calling {@link #isJsonObject()} * first. * * @return get this element as a {@link JsonObject}. * @throws IllegalStateException if the element is of another type. */ public JsonObject getAsJsonObject() { if (isJsonObject()) { return (JsonObject) this; } else { throw new IllegalStateException("This is not a JSON Object."); } } /** * convenience method to get this element as a {@link JsonArray}. If the element is of some * other type, a {@link ClassCastException} will result. Hence it is best to use this method * after ensuring that this element is of the desired type by calling {@link #isJsonArray()} * first. * * @return get this element as a {@link JsonArray}. * @throws IllegalStateException if the element is of another type. */ public JsonArray getAsJsonArray() { if (isJsonArray()) { return (JsonArray) this; } else { throw new IllegalStateException("This is not a JSON Array."); } } /** * convenience method to get this element as a {@link JsonPrimitive}. If the element is of some * other type, a {@link ClassCastException} will result. Hence it is best to use this method * after ensuring that this element is of the desired type by calling {@link #isJsonPrimitive()} * first. * * @return get this element as a {@link JsonPrimitive}. * @throws IllegalStateException if the element is of another type. */ public JsonPrimitive getAsJsonPrimitive() { if (isJsonPrimitive()) { return (JsonPrimitive) this; } else { throw new IllegalStateException("This is not a JSON Primitive."); } } /** * convenience method to get this element as a {@link JsonNull}. If the element is of some * other type, a {@link ClassCastException} will result. Hence it is best to use this method * after ensuring that this element is of the desired type by calling {@link #isJsonNull()} * first. * * @return get this element as a {@link JsonNull}. * @throws IllegalStateException if the element is of another type. * @since 1.2 */ public JsonNull getAsJsonNull() { if (isJsonNull()) { return (JsonNull) this; } else { throw new IllegalStateException("This is not a JSON Null."); } } /** * convenience method to get this element as a boolean value. * * @return get this element as a primitive boolean value. * @throws ClassCastException if the element is of not a {@link JsonPrimitive} and is not a valid * boolean value. * @throws IllegalStateException if the element is of the type {@link JsonArray} but contains * more than a single element. */ public boolean getAsBoolean() { throw new UnsupportedOperationException(); } /** * convenience method to get this element as a {@link Boolean} value. * * @return get this element as a {@link Boolean} value. * @throws ClassCastException if the element is of not a {@link JsonPrimitive} and is not a valid * boolean value. * @throws IllegalStateException if the element is of the type {@link JsonArray} but contains * more than a single element. */ Boolean getAsBooleanWrapper() { throw new UnsupportedOperationException(); } /** * convenience method to get this element as a {@link Number}. * * @return get this element as a {@link Number}. * @throws ClassCastException if the element is of not a {@link JsonPrimitive} and is not a valid * number. * @throws IllegalStateException if the element is of the type {@link JsonArray} but contains * more than a single element. */ public Number getAsNumber() { throw new UnsupportedOperationException(); } /** * convenience method to get this element as a string value. * * @return get this element as a string value. * @throws ClassCastException if the element is of not a {@link JsonPrimitive} and is not a valid * string value. * @throws IllegalStateException if the element is of the type {@link JsonArray} but contains * more than a single element. */ public String getAsString() { throw new UnsupportedOperationException(); } /** * convenience method to get this element as a primitive double value. * * @return get this element as a primitive double value. * @throws ClassCastException if the element is of not a {@link JsonPrimitive} and is not a valid * double value. * @throws IllegalStateException if the element is of the type {@link JsonArray} but contains * more than a single element. */ public double getAsDouble() { throw new UnsupportedOperationException(); } /** * convenience method to get this element as a primitive float value. * * @return get this element as a primitive float value. * @throws ClassCastException if the element is of not a {@link JsonPrimitive} and is not a valid * float value. * @throws IllegalStateException if the element is of the type {@link JsonArray} but contains * more than a single element. */ public float getAsFloat() { throw new UnsupportedOperationException(); } /** * convenience method to get this element as a primitive long value. * * @return get this element as a primitive long value. * @throws ClassCastException if the element is of not a {@link JsonPrimitive} and is not a valid * long value. * @throws IllegalStateException if the element is of the type {@link JsonArray} but contains * more than a single element. */ public long getAsLong() { throw new UnsupportedOperationException(); } /** * convenience method to get this element as a primitive integer value. * * @return get this element as a primitive integer value. * @throws ClassCastException if the element is of not a {@link JsonPrimitive} and is not a valid * integer value. * @throws IllegalStateException if the element is of the type {@link JsonArray} but contains * more than a single element. */ public int getAsInt() { throw new UnsupportedOperationException(); } /** * convenience method to get this element as a primitive byte value. * * @return get this element as a primitive byte value. * @throws ClassCastException if the element is of not a {@link JsonPrimitive} and is not a valid * byte value. * @throws IllegalStateException if the element is of the type {@link JsonArray} but contains * more than a single element. * @since 1.3 */ public byte getAsByte() { throw new UnsupportedOperationException(); } /** * convenience method to get this element as a primitive character value. * * @return get this element as a primitive char value. * @throws ClassCastException if the element is of not a {@link JsonPrimitive} and is not a valid * char value. * @throws IllegalStateException if the element is of the type {@link JsonArray} but contains * more than a single element. * @since 1.3 */ public char getAsCharacter() { throw new UnsupportedOperationException(); } /** * convenience method to get this element as a primitive short value. * * @return get this element as a primitive short value. * @throws ClassCastException if the element is of not a {@link JsonPrimitive} and is not a valid * short value. * @throws IllegalStateException if the element is of the type {@link JsonArray} but contains * more than a single element. */ public short getAsShort() { throw new UnsupportedOperationException(); } /** * convenience method to get this element as an {@link Object} value. * * @return get this element as an Object value. * @throws ClassCastException if the element is of not a {@link JsonPrimitive} and is not a valid * Object value. * @throws IllegalStateException if the element is of the type {@link JsonArray} but contains * more than a single element. */ Object getAsObject() { throw new UnsupportedOperationException(); } abstract JSONValue getAsGwtValue(); static JsonElement wrap(JSONValue value) { if (value == null) return null; if (value.isNull() != null) return JsonNull.createJsonNull(); if (value.isBoolean() != null || value.isNumber() != null || value.isString() != null) return new JsonPrimitive(value); if (value.isObject() != null) return new JsonObject(value.isObject()); if (value.isArray() != null) return new JsonArray(value.isArray()); throw new IllegalArgumentException(); } @Override public String toString() { return getAsGwtValue().toString(); } }