/*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you 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 org.apache.wink.json4j;
import java.io.BufferedWriter;
import java.io.CharArrayWriter;
import java.io.IOException;
import java.io.StringWriter;
import java.io.Writer;
import java.util.Stack;
import org.apache.wink.json4j.internal.BeanSerializer;
/**
* This class implements a JSONWrier, a convenience function for writing out JSON
* to a writer or underlying stream.
*/
public class JSONWriter {
/**
* The writer to use to output JSON in a semi-streaming fashion.
*/
protected Writer writer = null;
/**
* Flag to denote that the writer is in an object.
*/
private boolean inObject = false;
/**
* Flag to denote that the writer is in an array.
*/
private boolean inArray = false;
/**
* Flag for state checking that a key was placed (if inside an object)
* Required to be true for a value to be placed in that situation
*/
private boolean keyPlaced = false;
/**
* Flag denoting if in an array or object, if the first entry has been placed or not.
*/
private boolean firstEntry = false;
/**
* A stack to keep track of all the closures.
*/
private Stack closures = null;
/**
* Flag used to check the state of this writer, if it has been closed, all
* operations will throw an IllegalStateException.
*/
private boolean closed = false;
/**
* Constructor.
* @param writer The writer to use to do 'streaming' JSON writing.
* @throws NullPointerException Thrown if writer is null.
*/
public JSONWriter(Writer writer) throws NullPointerException {
//Try to avoid double-buffering or buffering in-memory writers.
Class writerClass = writer.getClass();
if (!StringWriter.class.isAssignableFrom(writerClass) &&
!CharArrayWriter.class.isAssignableFrom(writerClass) &&
!BufferedWriter.class.isAssignableFrom(writerClass)) {
writer = new BufferedWriter(writer);
}
this.writer = writer;
this.closures = new Stack();
}
/**
* Open a new JSON Array in the output stream.
* @throws IOException Thrown if an error occurs on the underlying writer.
* @throws IllegalstateException Thrown if the current writer position does not permit an array.
* @return A reference to this writer.
*/
public JSONWriter array() throws IOException, IllegalStateException {
if (closed) {
throw new IllegalStateException("The writer has been closed. No further operations allowed.");
}
if (inObject) {
if (!keyPlaced) {
throw new IllegalStateException("Current containment is a JSONObject, but a key has not been specified to contain a new array");
}
} else if (inArray) {
if (!firstEntry) {
writer.write(",");
}
}
writer.write("[");
inArray = true;
inObject = false;
keyPlaced = false;
firstEntry = true;
closures.push("]");
return this;
}
/**
* Method to close the current JSON Array in the stream.
* @throws IOException Thrown if an IO error occurs on the underlying writer.
* @throws IllegalStateException Thrown if the writer position is not inside an array.
* @return A reference to this writer.
*/
public JSONWriter endArray() throws IOException {
if (closed) {
throw new IllegalStateException("The writer has been closed. No further operations allowed.");
}
if (!inArray) {
throw new IllegalStateException("Current writer position is not within a JSON array");
} else {
writer.write(((String)closures.pop()));
// Set our current positional/control state.
if (!closures.isEmpty()) {
String nextClosure = (String)closures.peek();
if (nextClosure.equals("}")) {
inObject = true;
inArray = false;
} else {
inObject = false;
inArray = true;
}
firstEntry = false;
} else {
inArray = false;
inObject = false;
firstEntry = true;
}
}
return this;
}
/**
* Method to close a current JSON object in the stream.
* @throws IOException Thrown if an IO error occurs on the underlying writer.
* @throws IllegalStateException Thrown if the writer position is not inside an object, or if the object has a key placed, but no value.
* @return A reference to this writer.
*/
public JSONWriter endObject() throws IOException, IllegalStateException {
if (closed) {
throw new IllegalStateException("The writer has been closed. No further operations allowed.");
}
if (!inObject) {
throw new IllegalStateException("Current writer position is not within a JSON object");
} else {
if (keyPlaced) {
throw new IllegalStateException("Current writer position in an object and has a key placed, but no value has been assigned to the key. Cannot end.");
} else {
writer.write((String)closures.pop());
// Set our current positional/control state.
if (!closures.isEmpty()) {
String nextClosure = (String)closures.peek();
if (nextClosure.equals("}")) {
inObject = true;
inArray = false;
} else {
inObject = false;
inArray = true;
}
firstEntry = false;
} else {
inArray = false;
inObject = false;
firstEntry = true;
}
}
}
return this;
}
/**
* Place a key in the current JSON Object.
* @throws IOException Thrown if an IO error occurs on the underlying writer.
* @throws IllegalStateException Thrown if the current writer position is not within an object.
* @return A reference to this writer.
*/
public JSONWriter key(String s) throws IOException, IllegalStateException, NullPointerException {
if (closed) {
throw new IllegalStateException("The writer has been closed. No further operations allowed.");
}
if (s == null) {
throw new NullPointerException("Key cannot be null");
} else {
if (!inObject) {
throw new IllegalStateException("Current writer position is not inside a JSON Object, a key cannot be placed.");
} else {
if (!keyPlaced) {
if (firstEntry) {
firstEntry = false;
} else {
writer.write(",");
}
keyPlaced = true;
writeString(s);
writer.write(":");
} else {
throw new IllegalStateException("Current writer position is inside a JSON Object an with an open key waiting for a value. Another key cannot be placed.");
}
}
}
return this;
}
/**
* Open a new JSON Object in the output stream.
* @throws IllegalStateException Thrown if an object cannot currently be created in the stream.
* @throws IOException Thrown if an IO error occurs in the underlying writer.
* @return A reference to this writer.
*/
public JSONWriter object() throws IOException, IllegalStateException {
if (closed) {
throw new IllegalStateException("The writer has been closed. No further operations allowed.");
}
if (inObject) {
if (!keyPlaced) {
throw new IllegalStateException("Current containment is a JSONObject, but a key has not been specified to contain a new object");
}
} else if (inArray) {
if (!firstEntry) {
writer.write(",");
}
}
writer.write("{");
inObject = true;
inArray = false;
keyPlaced = false;
firstEntry = true;
closures.push("}");
return this;
}
/**
* Method to write a boolean to the current writer position.
* @throws IOException Thrown if an IO error occurs on the underlying writer.
* @throws IllegalStateException Thrown if the current writer position will not accept a boolean value.
* @return A reference to this writer.
*/
public JSONWriter value(boolean b) throws IOException, IllegalStateException {
if (closed) {
throw new IllegalStateException("The writer has been closed. No further operations allowed.");
}
if (inArray) {
if (firstEntry) {
firstEntry = false;
} else {
writer.write(",");
}
writer.write(Boolean.toString(b));
} else if (inObject) {
if (keyPlaced) {
writer.write(Boolean.toString(b));
keyPlaced = false;
} else {
throw new IllegalStateException("Current containment is a JSONObject, but a key has not been specified for the boolean value.");
}
} else {
throw new IllegalStateException("Writer is currently not in an array or object, cannot write value");
}
return this;
}
/**
* Method to write a double to the current writer position.
* @param d The Double to write.
* @throws IOException Thrown if an IO error occurs on the underlying writer.
* @throws IllegalStateException Thrown if the current writer position will not accept a double value.
* @return A reference to this writer.
*/
public JSONWriter value(double d) throws IOException, IllegalStateException {
if (closed) {
throw new IllegalStateException("The writer has been closed. No further operations allowed.");
}
if (inArray) {
if (firstEntry) {
firstEntry = false;
} else {
writer.write(",");
}
writer.write(Double.toString(d));
} else if (inObject) {
if (keyPlaced) {
writer.write(Double.toString(d));
keyPlaced = false;
} else {
throw new IllegalStateException("Current containment is a JSONObject, but a key has not been specified for the double value.");
}
} else {
throw new IllegalStateException("Writer is currently not in an array or object, cannot write value");
}
return this;
}
/**
* Method to write a double to the current writer position.
* @param l The long to write.
* @throws IOException Thrown if an IO error occurs on the underlying writer.
* @throws IllegalStateException Thrown if the current writer position will not accept a double value.
* @return A reference to this writer.
*/
public JSONWriter value(long l) throws IOException, IllegalStateException {
if (closed) {
throw new IllegalStateException("The writer has been closed. No further operations allowed.");
}
if (inArray) {
if (firstEntry) {
firstEntry = false;
} else {
writer.write(",");
}
writer.write(Long.toString(l));
} else if (inObject) {
if (keyPlaced) {
writer.write(Long.toString(l));
keyPlaced = false;
} else {
throw new IllegalStateException("Current containment is a JSONObject, but a key has not been specified for the long value.");
}
} else {
throw new IllegalStateException("Writer is currently not in an array or object, cannot write value");
}
return this;
}
/**
* Method to write an int to the current writer position.
* @param i The int to write.
* @throws IOException Thrown if an IO error occurs on the underlying writer.
* @throws IllegalStateException Thrown if the current writer position will not accept a double value.
* @return A reference to this writer.
*/
public JSONWriter value(int i) throws IOException, IllegalStateException {
if (closed) {
throw new IllegalStateException("The writer has been closed. No further operations allowed.");
}
if (inArray) {
if (firstEntry) {
firstEntry = false;
} else {
writer.write(",");
}
writer.write(Integer.toString(i));
} else if (inObject) {
if (keyPlaced) {
writer.write(Integer.toString(i));
keyPlaced = false;
} else {
throw new IllegalStateException("Current containment is a JSONObject, but a key has not been specified for the int value.");
}
} else {
throw new IllegalStateException("Writer is currently not in an array or object, cannot write value");
}
return this;
}
/**
* Method to write a short to the current writer position.
* @param s The short to write.
* @throws IOException Thrown if an IO error occurs on the underlying writer.
* @throws IllegalStateException Thrown if the current writer position will not accept a double value.
* @return A reference to this writer.
*/
public JSONWriter value(short s) throws IOException, IllegalStateException {
if (closed) {
throw new IllegalStateException("The writer has been closed. No further operations allowed.");
}
if (inArray) {
if (firstEntry) {
firstEntry = false;
} else {
writer.write(",");
}
writer.write(Short.toString(s));
} else if (inObject) {
if (keyPlaced) {
writer.write(Short.toString(s));
keyPlaced = false;
} else {
throw new IllegalStateException("Current containment is a JSONObject, but a key has not been specified for the short value.");
}
} else {
throw new IllegalStateException("Writer is currently not in an array or object, cannot write value");
}
return this;
}
/**
* Method to write an Object to the current writer position.
* @param o The object to write.
* @throws IOException Thrown if an IO error occurs on the underlying writer.
* @throws JSONException Thrown if the object is not JSONAble.
* @return A reference to this writer.
*/
public JSONWriter value(Object o) throws IOException, IllegalStateException, JSONException {
if (closed) {
throw new IllegalStateException("The writer has been closed. No further operations allowed.");
}
if (inArray) {
if (firstEntry) {
firstEntry = false;
} else {
writer.write(",");
}
writeObject(o);
} else if (inObject) {
if (keyPlaced) {
writeObject(o);
keyPlaced = false;
} else {
throw new IllegalStateException("Current containment is a JSONObject, but a key has not been specified for the boolean value.");
}
} else {
throw new IllegalStateException("Writer is currently not in an array or object, cannot write value");
}
return this;
}
/**
* Method to close the JSON Writer. All current object depths will be closed out and the writer closed.
* @throws IOException Thrown if an IO error occurs on the underlying writer.
* @throws IllegalStateException Thrown if the writer position is in an object and a key has been placed, but a value has not been assigned or if the writer was already closed.
*/
public void close() throws IOException, IllegalStateException {
if (!closed) {
if (inObject && keyPlaced) {
throw new IllegalStateException("Object has key without value. Cannot close.");
} else {
while (!closures.isEmpty()) {
writer.write((String)closures.pop());
}
writer.flush();
writer.close();
closed = true;
}
}
}
/**
* Method to flush the underlying writer so that all buffered content, if any, is written out.
* @return A reference to this writer.
*/
public JSONWriter flush() throws IOException {
writer.flush();
return this;
}
/**
* Method to write a String out to the writer, encoding special characters and unicode characters properly.
* @param value The string to write out.
* @throws IOException Thrown if an error occurs during write.
*/
private void writeString(String value) throws IOException {
writer.write('"');
char[] chars = value.toCharArray();
for (int i=0; i<chars.length; i++) {
char c = chars[i];
switch (c) {
case '"': writer.write("\\\""); break;
case '\\': writer.write("\\\\"); break;
case 0: writer.write("\\0"); break;
case '\b': writer.write("\\b"); break;
case '\t': writer.write("\\t"); break;
case '\n': writer.write("\\n"); break;
case '\f': writer.write("\\f"); break;
case '\r': writer.write("\\r"); break;
case '/': writer.write("\\/"); break;
default:
if ((c >= 32) && (c <= 126)) {
writer.write(c);
} else {
writer.write("\\u");
writer.write(rightAlignedZero(Integer.toHexString(c),4));
}
}
}
writer.write('"');
}
/**
* Method to generate a string with a particular width. Alignment is done using zeroes if it does not meet the width requirements.
* @param s The string to write
* @param len The minimum length it should be, and to align with zeroes if length is smaller.
* @return A string properly aligned/correct width.
*/
private String rightAlignedZero(String s, int len) {
if (len == s.length()) return s;
StringBuffer sb = new StringBuffer(s);
while (sb.length() < len) {
sb.insert(0, '0');
}
return sb.toString();
}
/**
* Method to write a number to the current writer.
* @param value The number to write to the JSON output string.
* @throws IOException Thrown if an error occurs during write.
*/
private void writeNumber(Number value) throws IOException {
if (null == value) {
writeNull();
}
if (value instanceof Float) {
if (((Float)value).isNaN()) {
writeNull();
}
if (Float.NEGATIVE_INFINITY == value.floatValue()) {
writeNull();
}
if (Float.POSITIVE_INFINITY == value.floatValue()) {
writeNull();
}
}
if (value instanceof Double) {
if (((Double)value).isNaN()) {
writeNull();
}
if (Double.NEGATIVE_INFINITY == value.doubleValue()) {
writeNull();
}
if (Double.POSITIVE_INFINITY == value.doubleValue()) {
writeNull();
}
}
writer.write(value.toString());
}
/**
* Method to write an object to the current writer.
* @param o The object to write.
* @throws IOException Thrown if an IO error occurs on the underlying writer.
* @throws JSONException Thrown if the specified object is not JSONAble.
*/
private void writeObject(Object o) throws IOException, JSONException {
// Handle the object!
if (o == null) {
writeNull();
} else {
Class clazz = o.getClass();
if (JSONArtifact.class.isAssignableFrom(clazz)) {
writer.write(((JSONArtifact)o).toString());
} else if (Number.class.isAssignableFrom(clazz)) {
writeNumber((Number)o);
} else if (Boolean.class.isAssignableFrom(clazz)) {
writer.write(((Boolean)o).toString());
} else if (String.class.isAssignableFrom(clazz)) {
writeString((String)o);
} else if (JSONString.class.isAssignableFrom(clazz)) {
writer.write(((JSONString)o).toJSONString());
} else {
// Unknown type, we'll just try to serialize it like a Java Bean.
writer.write(BeanSerializer.toJson(o, true).write());
}
}
}
/**
* Method to write the text string 'null' to the output stream (null JSON object).
* @throws IOException Thrown if an error occurs during write.
*/
private void writeNull() throws IOException {
writer.write("null");
}
}