Java tutorial
/* * $Id: JSONParser.java,v 1.1 2006/04/15 14:10:48 platform Exp $ * Created on 2006-4-15 */ package org.json.simple.parser; import java.io.IOException; import java.io.Reader; import java.io.StringReader; import java.util.LinkedList; import java.util.List; import java.util.Map; import org.json.simple.JSONArray; import org.json.simple.JSONObject; /** * Parser for JSON text. Please note that JSONParser is NOT thread-safe. * * @author FangYidong<fangyidong@yahoo.com.cn> */ public class JSONParser { public static final int S_INIT = 0; public static final int S_IN_FINISHED_VALUE = 1;//string,number,boolean,null,object,array public static final int S_IN_OBJECT = 2; public static final int S_IN_ARRAY = 3; public static final int S_PASSED_PAIR_KEY = 4; public static final int S_IN_PAIR_VALUE = 5; public static final int S_END = 6; public static final int S_IN_ERROR = -1; private LinkedList handlerStatusStack; private Yylex lexer = new Yylex((Reader) null); private Yytoken token = null; private int status = S_INIT; private int peekStatus(LinkedList statusStack) { if (statusStack.size() == 0) return -1; Integer status = (Integer) statusStack.getFirst(); return status.intValue(); } /** * Reset the parser to the initial state without resetting the underlying reader. * */ public void reset() { token = null; status = S_INIT; handlerStatusStack = null; } /** * Reset the parser to the initial state with a new character reader. * * @param in - The new character reader. * @throws IOException * @throws ParseException */ public void reset(Reader in) { lexer.yyreset(in); reset(); } /** * @return The position of the beginning of the current token. */ public int getPosition() { return lexer.getPosition(); } public Object parse(String s) throws ParseException { return parse(s, (ContainerFactory) null); } public Object parse(String s, ContainerFactory containerFactory) throws ParseException { StringReader in = new StringReader(s); try { return parse(in, containerFactory); } catch (IOException ie) { /* * Actually it will never happen. */ throw new ParseException(-1, ParseException.ERROR_UNEXPECTED_EXCEPTION, ie); } } public Object parse(Reader in) throws IOException, ParseException { return parse(in, (ContainerFactory) null); } /** * Parse JSON text into java object from the input source. * * @param in * @param containerFactory - Use this factory to createyour own JSON object and JSON array containers. * @return Instance of the following: * org.json.simple.JSONObject, * org.json.simple.JSONArray, * java.lang.String, * java.lang.Number, * java.lang.Boolean, * null * * @throws IOException * @throws ParseException */ public Object parse(Reader in, ContainerFactory containerFactory) throws IOException, ParseException { reset(in); LinkedList statusStack = new LinkedList(); LinkedList valueStack = new LinkedList(); try { do { nextToken(); switch (status) { case S_INIT: switch (token.type) { case Yytoken.TYPE_VALUE: status = S_IN_FINISHED_VALUE; statusStack.addFirst(new Integer(status)); valueStack.addFirst(token.value); break; case Yytoken.TYPE_LEFT_BRACE: status = S_IN_OBJECT; statusStack.addFirst(new Integer(status)); valueStack.addFirst(createObjectContainer(containerFactory)); break; case Yytoken.TYPE_LEFT_SQUARE: status = S_IN_ARRAY; statusStack.addFirst(new Integer(status)); valueStack.addFirst(createArrayContainer(containerFactory)); break; default: status = S_IN_ERROR; }//inner switch break; case S_IN_FINISHED_VALUE: if (token.type == Yytoken.TYPE_EOF) return valueStack.removeFirst(); else throw new ParseException(getPosition(), ParseException.ERROR_UNEXPECTED_TOKEN, token); case S_IN_OBJECT: switch (token.type) { case Yytoken.TYPE_COMMA: break; case Yytoken.TYPE_VALUE: if (token.value instanceof String) { String key = (String) token.value; valueStack.addFirst(key); status = S_PASSED_PAIR_KEY; statusStack.addFirst(new Integer(status)); } else { status = S_IN_ERROR; } break; case Yytoken.TYPE_RIGHT_BRACE: if (valueStack.size() > 1) { statusStack.removeFirst(); valueStack.removeFirst(); status = peekStatus(statusStack); } else { status = S_IN_FINISHED_VALUE; } break; default: status = S_IN_ERROR; break; }//inner switch break; case S_PASSED_PAIR_KEY: switch (token.type) { case Yytoken.TYPE_COLON: break; case Yytoken.TYPE_VALUE: statusStack.removeFirst(); String key = (String) valueStack.removeFirst(); Map parent = (Map) valueStack.getFirst(); parent.put(key, token.value); status = peekStatus(statusStack); break; case Yytoken.TYPE_LEFT_SQUARE: statusStack.removeFirst(); key = (String) valueStack.removeFirst(); parent = (Map) valueStack.getFirst(); List newArray = createArrayContainer(containerFactory); parent.put(key, newArray); status = S_IN_ARRAY; statusStack.addFirst(new Integer(status)); valueStack.addFirst(newArray); break; case Yytoken.TYPE_LEFT_BRACE: statusStack.removeFirst(); key = (String) valueStack.removeFirst(); parent = (Map) valueStack.getFirst(); Map newObject = createObjectContainer(containerFactory); parent.put(key, newObject); status = S_IN_OBJECT; statusStack.addFirst(new Integer(status)); valueStack.addFirst(newObject); break; default: status = S_IN_ERROR; } break; case S_IN_ARRAY: switch (token.type) { case Yytoken.TYPE_COMMA: break; case Yytoken.TYPE_VALUE: List val = (List) valueStack.getFirst(); val.add(token.value); break; case Yytoken.TYPE_RIGHT_SQUARE: if (valueStack.size() > 1) { statusStack.removeFirst(); valueStack.removeFirst(); status = peekStatus(statusStack); } else { status = S_IN_FINISHED_VALUE; } break; case Yytoken.TYPE_LEFT_BRACE: val = (List) valueStack.getFirst(); Map newObject = createObjectContainer(containerFactory); val.add(newObject); status = S_IN_OBJECT; statusStack.addFirst(new Integer(status)); valueStack.addFirst(newObject); break; case Yytoken.TYPE_LEFT_SQUARE: val = (List) valueStack.getFirst(); List newArray = createArrayContainer(containerFactory); val.add(newArray); status = S_IN_ARRAY; statusStack.addFirst(new Integer(status)); valueStack.addFirst(newArray); break; default: status = S_IN_ERROR; }//inner switch break; case S_IN_ERROR: throw new ParseException(getPosition(), ParseException.ERROR_UNEXPECTED_TOKEN, token); }//switch if (status == S_IN_ERROR) { throw new ParseException(getPosition(), ParseException.ERROR_UNEXPECTED_TOKEN, token); } } while (token.type != Yytoken.TYPE_EOF); } catch (IOException ie) { throw ie; } throw new ParseException(getPosition(), ParseException.ERROR_UNEXPECTED_TOKEN, token); } private void nextToken() throws ParseException, IOException { token = lexer.yylex(); if (token == null) token = new Yytoken(Yytoken.TYPE_EOF, null); } private Map createObjectContainer(ContainerFactory containerFactory) { if (containerFactory == null) return new JSONObject(); Map m = containerFactory.createObjectContainer(); if (m == null) return new JSONObject(); return m; } private List createArrayContainer(ContainerFactory containerFactory) { if (containerFactory == null) return new JSONArray(); List l = containerFactory.creatArrayContainer(); if (l == null) return new JSONArray(); return l; } public void parse(String s, ContentHandler contentHandler) throws ParseException { parse(s, contentHandler, false); } public void parse(String s, ContentHandler contentHandler, boolean isResume) throws ParseException { StringReader in = new StringReader(s); try { parse(in, contentHandler, isResume); } catch (IOException ie) { /* * Actually it will never happen. */ throw new ParseException(-1, ParseException.ERROR_UNEXPECTED_EXCEPTION, ie); } } public void parse(Reader in, ContentHandler contentHandler) throws IOException, ParseException { parse(in, contentHandler, false); } /** * Stream processing of JSON text. * * @see ContentHandler * * @param in * @param contentHandler * @param isResume - Indicates if it continues previous parsing operation. * If set to true, resume parsing the old stream, and parameter 'in' will be ignored. * If this method is called for the first time in this instance, isResume will be ignored. * * @throws IOException * @throws ParseException */ public void parse(Reader in, ContentHandler contentHandler, boolean isResume) throws IOException, ParseException { if (!isResume) { reset(in); handlerStatusStack = new LinkedList(); } else { if (handlerStatusStack == null) { isResume = false; reset(in); handlerStatusStack = new LinkedList(); } } LinkedList statusStack = handlerStatusStack; try { do { switch (status) { case S_INIT: contentHandler.startJSON(); nextToken(); switch (token.type) { case Yytoken.TYPE_VALUE: status = S_IN_FINISHED_VALUE; statusStack.addFirst(new Integer(status)); if (!contentHandler.primitive(token.value)) return; break; case Yytoken.TYPE_LEFT_BRACE: status = S_IN_OBJECT; statusStack.addFirst(new Integer(status)); if (!contentHandler.startObject()) return; break; case Yytoken.TYPE_LEFT_SQUARE: status = S_IN_ARRAY; statusStack.addFirst(new Integer(status)); if (!contentHandler.startArray()) return; break; default: status = S_IN_ERROR; }//inner switch break; case S_IN_FINISHED_VALUE: nextToken(); if (token.type == Yytoken.TYPE_EOF) { contentHandler.endJSON(); status = S_END; return; } else { status = S_IN_ERROR; throw new ParseException(getPosition(), ParseException.ERROR_UNEXPECTED_TOKEN, token); } case S_IN_OBJECT: nextToken(); switch (token.type) { case Yytoken.TYPE_COMMA: break; case Yytoken.TYPE_VALUE: if (token.value instanceof String) { String key = (String) token.value; status = S_PASSED_PAIR_KEY; statusStack.addFirst(new Integer(status)); if (!contentHandler.startObjectEntry(key)) return; } else { status = S_IN_ERROR; } break; case Yytoken.TYPE_RIGHT_BRACE: if (statusStack.size() > 1) { statusStack.removeFirst(); status = peekStatus(statusStack); } else { status = S_IN_FINISHED_VALUE; } if (!contentHandler.endObject()) return; break; default: status = S_IN_ERROR; break; }//inner switch break; case S_PASSED_PAIR_KEY: nextToken(); switch (token.type) { case Yytoken.TYPE_COLON: break; case Yytoken.TYPE_VALUE: statusStack.removeFirst(); status = peekStatus(statusStack); if (!contentHandler.primitive(token.value)) return; if (!contentHandler.endObjectEntry()) return; break; case Yytoken.TYPE_LEFT_SQUARE: statusStack.removeFirst(); statusStack.addFirst(new Integer(S_IN_PAIR_VALUE)); status = S_IN_ARRAY; statusStack.addFirst(new Integer(status)); if (!contentHandler.startArray()) return; break; case Yytoken.TYPE_LEFT_BRACE: statusStack.removeFirst(); statusStack.addFirst(new Integer(S_IN_PAIR_VALUE)); status = S_IN_OBJECT; statusStack.addFirst(new Integer(status)); if (!contentHandler.startObject()) return; break; default: status = S_IN_ERROR; } break; case S_IN_PAIR_VALUE: /* * S_IN_PAIR_VALUE is just a marker to indicate the end of an object entry, it doesn't proccess any token, * therefore delay consuming token until next round. */ statusStack.removeFirst(); status = peekStatus(statusStack); if (!contentHandler.endObjectEntry()) return; break; case S_IN_ARRAY: nextToken(); switch (token.type) { case Yytoken.TYPE_COMMA: break; case Yytoken.TYPE_VALUE: if (!contentHandler.primitive(token.value)) return; break; case Yytoken.TYPE_RIGHT_SQUARE: if (statusStack.size() > 1) { statusStack.removeFirst(); status = peekStatus(statusStack); } else { status = S_IN_FINISHED_VALUE; } if (!contentHandler.endArray()) return; break; case Yytoken.TYPE_LEFT_BRACE: status = S_IN_OBJECT; statusStack.addFirst(new Integer(status)); if (!contentHandler.startObject()) return; break; case Yytoken.TYPE_LEFT_SQUARE: status = S_IN_ARRAY; statusStack.addFirst(new Integer(status)); if (!contentHandler.startArray()) return; break; default: status = S_IN_ERROR; }//inner switch break; case S_END: return; case S_IN_ERROR: throw new ParseException(getPosition(), ParseException.ERROR_UNEXPECTED_TOKEN, token); }//switch if (status == S_IN_ERROR) { throw new ParseException(getPosition(), ParseException.ERROR_UNEXPECTED_TOKEN, token); } } while (token.type != Yytoken.TYPE_EOF); } catch (IOException ie) { status = S_IN_ERROR; throw ie; } catch (ParseException pe) { status = S_IN_ERROR; throw pe; } catch (RuntimeException re) { status = S_IN_ERROR; throw re; } catch (Error e) { status = S_IN_ERROR; throw e; } status = S_IN_ERROR; throw new ParseException(getPosition(), ParseException.ERROR_UNEXPECTED_TOKEN, token); } }