/*
* 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 {
/**
* 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;
}
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 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;
}
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;
}
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;
}
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(getClass().getSimpleName());
}
/**
* 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(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 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(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);
}
}
}