de.bsd.x2svg
Class ParserLoader

java.lang.Object
  de.bsd.x2svg.ParserLoader

public class ParserLoader
extends java.lang.Object

This singleton class is used to load the Parsers as plugins. Parsers are expected to live in the package de.bsd.x2svg.parsers and to implement the interface InputParser.

The loader currently expects that all parsers live in the main jar file (x2svg) within the classpath.

Before the any other methods can be called, it is necessary to at lease once call load().

Since:

1.0

Author:

hwr@pilhuhn.de

See Also:

de.bsd.x2svg.parsers

Nested Class Summary

private static class

ParserLoader.ClassNameFileFilter Filter that accepts files ending in .class

Field Summary

private static boolean	debug
private java.util.Map<java.lang.String,java.lang.String>	helpByMode
private boolean	loaded
private java.util.Map<java.lang.String,java.lang.String>	modeAndSuffix
private static java.lang.String	NO_SPECIFIC_HELP_AVAILABLE
private static java.lang.String	PACKAGE_STRING
private java.util.Map<java.lang.String,java.lang.Class<InputParser>>	parserByMode
private java.util.Map<java.lang.String,java.lang.Class<InputParser>>	parserBySuffix
private static ParserLoader	theLoader

Constructor Summary

private

ParserLoader() Private constructor as we are a singleton

Method Summary

private void	addToParserList(java.lang.Class<InputParser> clazz) Enter the passed class into the lists of parsers
private void	checkClassIsParser(java.lang.String classname) Checks if the class passed in is a valid InputParser.
java.lang.String	getHelpForMode(java.lang.String mode) Return the parser specific help for the passed mode.
static ParserLoader	getLoader() Get the instance of ParserLoader
InputParser	getParserByMode(java.lang.String mode) Return a parser for a given mode.
InputParser	getParserForFilename(java.lang.String filename) Return a parser instance by selecting a matching suffix for the file name.
java.lang.String	listParsers() List all parsers that we know about
void	load() Load the parsers from the main jar and register them in our list.
static void	main(java.lang.String[] args) For debugging the ParserLoader separately

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

PACKAGE_STRING

private static final java.lang.String PACKAGE_STRING

See Also:

Constant Field Values

theLoader

private static volatile ParserLoader theLoader

parserByMode

private java.util.Map<java.lang.String,java.lang.Class<InputParser>> parserByMode

parserBySuffix

private java.util.Map<java.lang.String,java.lang.Class<InputParser>> parserBySuffix

helpByMode

private java.util.Map<java.lang.String,java.lang.String> helpByMode

modeAndSuffix

private java.util.Map<java.lang.String,java.lang.String> modeAndSuffix

debug

private static boolean debug

NO_SPECIFIC_HELP_AVAILABLE

private static final java.lang.String NO_SPECIFIC_HELP_AVAILABLE

See Also:

Constant Field Values

loaded

private boolean loaded

Constructor Detail

ParserLoader

private ParserLoader()

Private constructor as we are a singleton

Method Detail

getLoader

public static ParserLoader getLoader()

Get the instance of ParserLoader

Returns:

The instance of the ParserLoader

getParserByMode

public InputParser getParserByMode(java.lang.String mode)
                            throws NoParserException,
                                   java.lang.IllegalAccessException,
                                   java.lang.InstantiationException

Return a parser for a given mode.

Parameters:

mode - a Mode that needs to be registered by the parser.

Returns:

a valid InputParser if found

Throws:

NoParserException - if the passed mode is invalid or no parser was found

java.lang.IllegalAccessException - If the parser class is not accessible

java.lang.InstantiationException - If the parser class can not be instantiated

java.lang.IllegalStateException - If load() has not yet been called

getParserForFilename

public InputParser getParserForFilename(java.lang.String filename)
                                 throws NoParserException,
                                        java.lang.InstantiationException,
                                        java.lang.IllegalAccessException

Return a parser instance by selecting a matching suffix for the file name.

Parameters:

filename - Name of the file to determine the suffix

Returns:

a valid InputParser

Throws:

NoParserException - if the input is invalid or no parser was found for the passed filename.

java.lang.IllegalAccessException - If the parser class is not accessible

java.lang.InstantiationException - If the parser class can not be instantiated

java.lang.IllegalStateException - If load() has not yet been called

See Also:

String.endsWith(String)

load

public void load()

Load the parsers from the main jar and register them in our list. This method needs to be called before calling one of the getParser*(), listParsers() or getHelpForMode() methods.

We first open the main jar, get the entries in the package de.bsd.x2svg.parsers and then look at those entries if they implement InputParser. After this, we pass the the matching class to the addToParserList() method, which does the magic for us.

checkClassIsParser

private void checkClassIsParser(java.lang.String classname)
                         throws java.lang.ClassNotFoundException

Checks if the class passed in is a valid InputParser. This is done by looking at the interfaces of that class.

Parameters:

classname - Name of a class in form of a path

Throws:

java.lang.ClassNotFoundException - If the passed class could not be found in the classpath

addToParserList

private void addToParserList(java.lang.Class<InputParser> clazz)

Enter the passed class into the lists of parsers

Parameters:

clazz - The main class of an InputParser

listParsers

public java.lang.String listParsers()

List all parsers that we know about

Returns:

A string with a list of parsers separated by newlines

Throws:

java.lang.IllegalStateException - If load() has not yet been called

getHelpForMode

public java.lang.String getHelpForMode(java.lang.String mode)

Return the parser specific help for the passed mode. If mode is '*', then help is shown for all parsers.

Parameters:

mode - a valid mode or '*'

Returns:

the parser specific help

Throws:

java.lang.IllegalStateException - If load() has not yet been called

main

public static void main(java.lang.String[] args)

For debugging the ParserLoader separately

Parameters:

args - No command line options needed.