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/* * Copyright (C) 2008 Google Inc. * * 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.gson.internal.Streams; import com.google.gson.stream.JsonWriter; import java.io.IOException; import java.io.StringWriter; import java.math.BigDecimal; import java.math.BigInteger; /** * 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 { /** * Returns a deep copy of this element. Immutable elements like primitives * and nulls are not copied. * @since 2.8.2 */ public abstract JsonElement deepCopy(); /** * 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 IllegalStateException} 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; } throw new IllegalStateException("Not a JSON Object: " + this); } /** * convenience method to get this element as a {@link JsonArray}. If the element is of some * other type, a {@link IllegalStateException} 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; } throw new IllegalStateException("Not a JSON Array: " + this); } /** * convenience method to get this element as a {@link JsonPrimitive}. If the element is of some * other type, a {@link IllegalStateException} 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; } throw new IllegalStateException("Not a JSON Primitive: " + this); } /** * convenience method to get this element as a {@link JsonNull}. If the element is of some * other type, a {@link IllegalStateException} 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; } throw new IllegalStateException("Not a JSON Null: " + this); } /** * 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(getClass().getSimpleName()); } /** * 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(getClass().getSimpleName()); } /** * 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(getClass().getSimpleName()); } /** * 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(getClass().getSimpleName()); } /** * 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(getClass().getSimpleName()); } /** * 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(getClass().getSimpleName()); } /** * 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(getClass().getSimpleName()); } /** * 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(getClass().getSimpleName()); } /** * convenience method to get the first character of this element as a string or the first * character of this array's first element as a string. * * @return the first character of the string. * @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. * @since 1.3 * @deprecated This method is misleading, as it does not get this element as a char but rather as * a string's first character. */ @Deprecated public char getAsCharacter() { throw new UnsupportedOperationException(getClass().getSimpleName()); } /** * convenience method to get this element as a {@link BigDecimal}. * * @return get this element as a {@link BigDecimal}. * @throws ClassCastException if the element is of not a {@link JsonPrimitive}. * * @throws NumberFormatException if the element is not a valid {@link BigDecimal}. * @throws IllegalStateException if the element is of the type {@link JsonArray} but contains * more than a single element. * @since 1.2 */ public BigDecimal getAsBigDecimal() { throw new UnsupportedOperationException(getClass().getSimpleName()); } /** * convenience method to get this element as a {@link BigInteger}. * * @return get this element as a {@link BigInteger}. * @throws ClassCastException if the element is of not a {@link JsonPrimitive}. * @throws NumberFormatException if the element is not a valid {@link BigInteger}. * @throws IllegalStateException if the element is of the type {@link JsonArray} but contains * more than a single element. * @since 1.2 */ public BigInteger getAsBigInteger() { throw new UnsupportedOperationException(getClass().getSimpleName()); } /** * 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(getClass().getSimpleName()); } /** * Returns a String representation of this element. */ @Override public String toString() { try { StringWriter stringWriter = new StringWriter(); JsonWriter jsonWriter = new JsonWriter(stringWriter); jsonWriter.setLenient(true); Streams.write(this, jsonWriter); return stringWriter.toString(); } catch (IOException e) { throw new AssertionError(e); } } }