Application: gvSIG desktop » gvSIG tools: ToolBox

package org.json;

import java.io.IOException;

import java.io.Writer;

/*

Copyright (c) 2006 JSON.org

Permission is hereby granted, free of charge, to any person obtaining a copy

of this software and associated documentation files (the "Software"), to deal

in the Software without restriction, including without limitation the rights

to use, copy, modify, merge, publish, distribute, sublicense, and/or sell

copies of the Software, and to permit persons to whom the Software is

furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all

copies or substantial portions of the Software.

The Software shall be used for Good, not Evil.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR

IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,

FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE

AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER

LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,

OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE

SOFTWARE.

*/

/**

 * JSONWriter provides a quick and convenient way of producing JSON text. The texts produced strictly conform to JSON syntax

 * rules. No whitespace is added, so the results are ready for transmission or storage. Each instance of JSONWriter can produce

 * one JSON text.

 * <p>

 * A JSONWriter instance provides a <code>value</code> method for appending values to the text, and a <code>key</code> method

 * for adding keys before values in objects. There are <code>array</code> and <code>endArray</code> methods that make and

 * bound array values, and <code>object</code> and <code>endObject</code> methods which make and bound object values. All of

 * these methods return the JSONWriter instance, permitting a cascade style. For example,

 *

 * <pre>

 * new JSONWriter(myWriter).object().key("JSON").value("Hello, World!").endObject();

 * </pre>

 *

 * which writes

 *

 * <pre>

 * {"JSON":"Hello, World!"}

 * </pre>

 *

 * <p>

 * The first method called must be <code>array</code> or <code>object</code>. There are no methods for adding commas or

 * colons. JSONWriter adds them for you. Objects and arrays can be nested up to 20 levels deep.

 * <p>

 * This can sometimes be easier than using a JSONObject to build a string.

 *

 * @author JSON.org

 * @version 2

 */

public class JSONWriter {

   private static final int maxdepth = 20;

   /**

    * The comma flag determines if a comma should be output before the next value.

    */

   private boolean          comma;

   /**

    * The current mode. Values: 'a' (array), 'd' (done), 'i' (initial), 'k' (key), 'o' (object).

    */

   protected char           mode;

   /**

    * The object/array stack.

    */

   private final char             stack[];

   /**

    * The stack top index. A value of 0 indicates that the stack is empty.

    */

   private int              top;

   /**

    * The writer that will receive the output.

    */

   protected Writer         writer;

   /**

    * Make a fresh JSONWriter. It can be used to build one JSON text.

    */

   public JSONWriter(final Writer w) {

      this.comma = false;

      this.mode = 'i';

      this.stack = new char[maxdepth];

      this.top = 0;

      this.writer = w;

   }

   /**

    * Append a value.

    *

    * @param s

    *                A string value.

    * @return this

    * @throws JSONException

    *                 If the value is out of sequence.

    */

   private JSONWriter append(final String s) throws JSONException {

      if (s == null) {

         throw new JSONException("Null pointer");

      }

      if (this.mode == 'o' || this.mode == 'a') {

         try {

            if (this.comma && this.mode == 'a') {

               this.writer.write(',');

            }

            this.writer.write(s);

         }

         catch (final IOException e) {

            throw new JSONException(e);

         }

         if (this.mode == 'o') {

            this.mode = 'k';

         }

         this.comma = true;

         return this;

      }

      throw new JSONException("Value out of sequence.");

   }

   /**

    * Begin appending a new array. All values until the balancing <code>endArray</code> will be appended to this array. The

    * <code>endArray</code> method must be called to mark the array's end.

    *

    * @return this

    * @throws JSONException

    *                 If the nesting is too deep, or if the object is started in the wrong place (for example as a key or after

    *                 the end of the outermost array or object).

    */

   public JSONWriter array() throws JSONException {

      if (this.mode == 'i' || this.mode == 'o' || this.mode == 'a') {

         this.push('a');

         this.append("[");

         this.comma = false;

         return this;

      }

      throw new JSONException("Misplaced array.");

   }

   /**

    * End something.

    *

    * @param m

    *                Mode

    * @param c

    *                Closing character

    * @return this

    * @throws JSONException

    *                 If unbalanced.

    */

   private JSONWriter end(final char m,

                          final char c) throws JSONException {

      if (this.mode != m) {

         throw new JSONException(m == 'o' ? "Misplaced endObject." : "Misplaced endArray.");

      }

      this.pop(m);

      try {

         this.writer.write(c);

      }

      catch (final IOException e) {

         throw new JSONException(e);

      }

      this.comma = true;

      return this;

   }

   /**

    * End an array. This method most be called to balance calls to <code>array</code>.

    *

    * @return this

    * @throws JSONException

    *                 If incorrectly nested.

    */

   public JSONWriter endArray() throws JSONException {

      return this.end('a', ']');

   }

   /**

    * End an object. This method most be called to balance calls to <code>object</code>.

    *

    * @return this

    * @throws JSONException

    *                 If incorrectly nested.

    */

   public JSONWriter endObject() throws JSONException {

      return this.end('k', '}');

   }

   /**

    * Append a key. The key will be associated with the next value. In an object, every value must be preceded by a key.

    *

    * @param s

    *                A key string.

    * @return this

    * @throws JSONException

    *                 If the key is out of place. For example, keys do not belong in arrays or if the key is null.

    */

   public JSONWriter key(final String s) throws JSONException {

      if (s == null) {

         throw new JSONException("Null key.");

      }

      if (this.mode == 'k') {

         try {

            if (this.comma) {

               this.writer.write(',');

            }

            this.writer.write(JSONObject.quote(s));

            this.writer.write(':');

            this.comma = false;

            this.mode = 'o';

            return this;

         }

         catch (final IOException e) {

            throw new JSONException(e);

         }

      }

      throw new JSONException("Misplaced key.");

   }

   /**

    * Begin appending a new object. All keys and values until the balancing <code>endObject</code> will be appended to this

    * object. The <code>endObject</code> method must be called to mark the object's end.

    *

    * @return this

    * @throws JSONException

    *                 If the nesting is too deep, or if the object is started in the wrong place (for example as a key or after

    *                 the end of the outermost array or object).

    */

   public JSONWriter object() throws JSONException {

      if (this.mode == 'i') {

         this.mode = 'o';

      }

      if (this.mode == 'o' || this.mode == 'a') {

         this.append("{");

         this.push('k');

         this.comma = false;

         return this;

      }

      throw new JSONException("Misplaced object.");

   }

   /**

    * Pop an array or object scope.

    *

    * @param c

    *                The scope to close.

    * @throws JSONException

    *                 If nesting is wrong.

    */

   private void pop(final char c) throws JSONException {

      if (this.top <= 0 || this.stack[this.top - 1] != c) {

         throw new JSONException("Nesting error.");

      }

      this.top -= 1;

      this.mode = this.top == 0 ? 'd' : this.stack[this.top - 1];

   }

   /**

    * Push an array or object scope.

    *

    * @param c

    *                The scope to open.

    * @throws JSONException

    *                 If nesting is too deep.

    */

   private void push(final char c) throws JSONException {

      if (this.top >= maxdepth) {

         throw new JSONException("Nesting too deep.");

      }

      this.stack[this.top] = c;

      this.mode = c;

      this.top += 1;

   }

   /**

    * Append either the value <code>true</code> or the value <code>false</code>.

    *

    * @param b

    *                A boolean.

    * @return this

    * @throws JSONException

    */

   public JSONWriter value(final boolean b) throws JSONException {

      return this.append(b ? "true" : "false");

   }

   /**

    * Append a double value.

    *

    * @param d

    *                A double.

    * @return this

    * @throws JSONException

    *                 If the number is not finite.

    */

   public JSONWriter value(final double d) throws JSONException {

      return this.value(new Double(d));

   }

   /**

    * Append a long value.

    *

    * @param l

    *                A long.

    * @return this

    * @throws JSONException

    */

   public JSONWriter value(final long l) throws JSONException {

      return this.append(Long.toString(l));

   }

   /**

    * Append an object value.

    *

    * @param o

    *                The object to append. It can be null, or a Boolean, Number, String, JSONObject, or JSONArray, or an object

    *                with a toJSONString() method.

    * @return this

    * @throws JSONException

    *                 If the value is out of sequence.

    */

   public JSONWriter value(final Object o) throws JSONException {

      return this.append(JSONObject.valueToString(o));

   }

}