/*
* 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 java.io.IOException;
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 {
private static final Escaper BASIC_ESCAPER = new Escaper(false);
/**
* 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.");
}
}
public JsonObject getAsJsonObject(String memberName) {
return getAsJsonObject().get(memberName).getAsJsonObject();
}
/**
* 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 {@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();
}
/**
* 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();
}
/**
* 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();
}
/**
* Returns a String representation of this element.
*
* @return String the string representation of this element.
*/
@Override
public String toString() {
try {
StringBuilder sb = new StringBuilder();
toString(sb, BASIC_ESCAPER);
return sb.toString();
} catch (IOException e) {
throw new RuntimeException(e);
}
}
protected abstract void toString(Appendable sb, Escaper escaper)
throws IOException;
}
|