Error Handling In Javacc
Reporting and Recovery This document describes the error recovery features introduced in Version 0.7.1. This document also describes how features have changed since Version 0.6. The first change (from 0.6) is that we have two new exceptions: . ParseException . TokenMgrError Whenever the token manager detects a problem, it throws the exception TokenMgrError. Previously, it used to print the message: Lexical Error ... following which it use to throw the exception ParseError. Whenever the parser detects a problem, it throws the exception ParseException. Previously, it used to print the message: Encountered ... Was expecting one of ... following which it use to throw the exception ParseError. In Version 0.7.1, error messages are never printed explicitly, rather this information is stored inside the exception objects that are thrown. Please see the classes ParseException.java and TokenMgrError.java (that get generated by JavaCC [tm] during parser generation) for more details. If the thrown exceptions are never caught, then a standard action is taken by the virtual machine which normally includes printing the stack trace and also the result of the "toString" method in the exception. So if you do not catch the JavaCC exceptions, a message quite similar to the ones in Version 0.6. But if you catch the exception, you must print the message yourself. Exceptions in the Java [tm] programming language are all subclasses of type Throwable. Furthermore, exceptions are divided into two broad categories - ERRORS and other exceptions. Errors are exceptions that one is not expected to recover from - examples of these are ThreadDeath or OutOfMemoryError. Errors are indicated by subclassing the exception "Error". Exceptions subclassed from Error need not be specified in the "throws" clause of method declarations. Exceptions other than errors are typically defined by subclassing the exception "Exception". These exceptions are typically handled by the user program and must be declared in throws clauses of method declarations (if it is possible for the method to throw that exception). The exception TokenMgrError is a subclass of Error, while the exception ParseException is a subclass of Exception. The reasoning here is that the token manager is never expected to throw an exception - you must be careful in defining your token specifications such that you cover all cases. Hence the suffix "Error" in TokenMgrError. You do not have to worry about this exception - if you have designed your tokens well, it should never get thrown. Whereas it is typical to attempt recovery from Parser errors - hence t
to 15 of 15 Thread: How to handle error in parser javacc LinkBack LinkBack URL About LinkBacks Thread Tools Show Printable Version Email this Page… Subscribe to this Thread… Search Thread Advanced Search Display Linear Mode Switch to Hybrid Mode Switch to Threaded Mode 05-30-2013,12:56 PM #1 rrl Member Join Date May 2013 Posts 8 Rep Power 0 How to handle error in parser javacc in attachment, my parser https://javacc.java.net/doc/errorrecovery.html generated with javacc in eclipse. I don't know as to handle errors of sintax in my parser. how I can to do? what ways there are? I prefer if you can posting your code that show it. Thank you very much in advanced. Attached Files parser.txt (3.0 KB, 7 views) Reply With Quote 06-11-2013,11:09 http://www.java-forums.org/new-java/74676-how-handle-error-parser-javacc.html AM #2 rrl Member Join Date May 2013 Posts 8 Rep Power 0 Re: How to handle error in parser javacc I have an important exam of this project and I don't know to do. Help me! Thank you very much Reply With Quote 06-11-2013,01:15 PM #3 DarrylBurke Forum Police Join Date Sep 2008 Location Madgaon, Goa, India Posts 12,001 Rep Power 23 Re: How to handle error in parser javacc For reference, this is the content of the attachment. Java Code: /** * JavaCC template file created by SF JavaCC plugin 1.5.17+ wizard for JavaCC 1.5.0+ */ options { JDK_VERSION = "1.5"; IGNORE_CASE = true; LOOKAHEAD = 2; static = true; } PARSER_BEGIN(MyParser) import java.io.* ; public class MyParser { public static void main(String args []) throws ParseException { Token t; MyParserTokenManager tm; int numToken = 0; if (args.length<1) { System.out.println("Sorgente non specificato"); System.exit(1); } try { java.io.InputStream infile; infile = new java.io.FileInputStream(args[0]); tm = new MyParserTokenManager(new SimpleCharStream(infile)); } catch (java.io.FileNotFoundException
of the warnings and errors generated by JavaCC Posted on June 20, 2013 by Ram Kulkarni I am currently building a parser using JavaCC. I have used JavaCC in the past, but whenever I use it after a long http://ramkulkarni.com/blog/handling-some-of-the-warnings-and-errors-generated-by-javacc/ gap, I have to relearn a few things about it - particularly handling warnings. So I thought this time I would blog about ways to handle some of the frequent warnings that I have seen. If you are unfamiliar with JavaCC, then it is a parser generator. You create grammer using EBNF (Extended Backus-Naur Form) and feed it to JavaCC. JavaCC then creates Java classes for the parser. I do not want to error handling make this post into JavaCC tutorial. There are some very good tutorials available at JavaCC Documentation page and FAQ. I especially find Lookahead MiniTutorial and Token Manager MiniTutorial very useful. If you use Eclipse IDE, then you would find JavaCC plugin for Eclipse useful - it provides wizard to create JavaCC or JJTree (JJTree creates AST, Abstract Syntax Tree, after parsing the input) files, provides code colorization, outline, code hyper link, syntax checking and compilation. You can also error handling in set JavaCC debug options easily using this plugin. I will use following tokens that are generated by default if you use the wizard provided by JavaCC Eclipse plugin to create a JavaCC grammer file. I have created a .jjt file for examples in this blog. SKIP: { " " | "\t" | "\n" | "\r" | <"//" (~["\n","\r"])* ("\n"|"\r"|"\r\n")> | <"/*" (~["*"])* "*" (~["/"] (~["*"])* "*")* "/"> } TOKEN:/* LITERALS */ { < INTEGER_LITERAL: