Java example source code file (CachingParserPool.java)
The CachingParserPool.java Java example source code
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/*
* Copyright 1999-2002,2004 The Apache Software Foundation.
*
* Licensed 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.
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package com.sun.org.apache.xerces.internal.parsers;
import com.sun.org.apache.xerces.internal.xni.grammars.Grammar;
import com.sun.org.apache.xerces.internal.xni.grammars.XMLGrammarPool;
import com.sun.org.apache.xerces.internal.xni.grammars.XMLGrammarDescription;
import com.sun.org.apache.xerces.internal.util.XMLGrammarPoolImpl;
import com.sun.org.apache.xerces.internal.util.ShadowedSymbolTable;
import com.sun.org.apache.xerces.internal.util.SymbolTable;
import com.sun.org.apache.xerces.internal.util.SynchronizedSymbolTable;
/**
* A parser pool that enables caching of grammars. The caching parser
* pool is constructed with a specific symbol table and grammar pool
* that has already been populated with the grammars used by the
* application.
* <p>
* Once the caching parser pool is constructed, specific parser
* instances are created by calling the appropriate factory method
* on the parser pool.
* <p>
* <strong>Note: There is a performance penalty for using
* a caching parser pool due to thread safety. Access to the symbol
* table and grammar pool must be synchronized to ensure the safe
* operation of the symbol table and grammar pool.
* <p>
* <strong>Note: If performance is critical, then another
* mechanism needs to be used instead of the caching parser pool.
* One approach would be to create parser instances that do not
* share these structures. Instead, each instance would get its
* own copy to use while parsing. This avoids the synchronization
* overhead at the expense of more memory and the time required
* to copy the structures for each new parser instance. And even
* when a parser instance is re-used, there is a potential for a
* memory leak due to new symbols being added to the symbol table
* over time. In other words, always take caution to make sure
* that your application is thread-safe and avoids leaking memory.
*
* @author Andy Clark, IBM
*
*/
public class CachingParserPool {
//
// Constants
//
/** Default shadow symbol table (false). */
public static final boolean DEFAULT_SHADOW_SYMBOL_TABLE = false;
/** Default shadow grammar pool (false). */
public static final boolean DEFAULT_SHADOW_GRAMMAR_POOL = false;
//
// Data
//
/**
* Symbol table. The symbol table that the caching parser pool is
* constructed with is automatically wrapped in a synchronized
* version for thread-safety.
*/
protected SymbolTable fSynchronizedSymbolTable;
/**
* Grammar pool. The grammar pool that the caching parser pool is
* constructed with is automatically wrapped in a synchronized
* version for thread-safety.
*/
protected XMLGrammarPool fSynchronizedGrammarPool;
/**
* Shadow the symbol table for new parser instances. If true,
* new parser instances use shadow copies of the main symbol
* table and are not allowed to add new symbols to the main
* symbol table. New symbols are added to the shadow symbol
* table and are local to the parser instance.
*/
protected boolean fShadowSymbolTable = DEFAULT_SHADOW_SYMBOL_TABLE;
/**
* Shadow the grammar pool for new parser instances. If true,
* new parser instances use shadow copies of the main grammar
* pool and are not allowed to add new grammars to the main
* grammar pool. New grammars are added to the shadow grammar
* pool and are local to the parser instance.
*/
protected boolean fShadowGrammarPool = DEFAULT_SHADOW_GRAMMAR_POOL;
//
// Constructors
//
/** Default constructor. */
public CachingParserPool() {
this(new SymbolTable(), new XMLGrammarPoolImpl());
} // <init>()
/**
* Constructs a caching parser pool with the specified symbol table
* and grammar pool.
*
* @param symbolTable The symbol table.
* @param grammarPool The grammar pool.
*/
public CachingParserPool(SymbolTable symbolTable, XMLGrammarPool grammarPool) {
fSynchronizedSymbolTable = new SynchronizedSymbolTable(symbolTable);
fSynchronizedGrammarPool = new SynchronizedGrammarPool(grammarPool);
} // <init>(SymbolTable,XMLGrammarPool)
//
// Public methods
//
/** Returns the symbol table. */
public SymbolTable getSymbolTable() {
return fSynchronizedSymbolTable;
} // getSymbolTable():SymbolTable
/** Returns the grammar pool. */
public XMLGrammarPool getXMLGrammarPool() {
return fSynchronizedGrammarPool;
} // getXMLGrammarPool():XMLGrammarPool
// setters and getters
/**
* Sets whether new parser instance receive shadow copies of the
* main symbol table.
*
* @param shadow If true, new parser instances use shadow copies
* of the main symbol table and are not allowed to
* add new symbols to the main symbol table. New
* symbols are added to the shadow symbol table and
* are local to the parser instance. If false, new
* parser instances are allowed to add new symbols
* to the main symbol table.
*/
public void setShadowSymbolTable(boolean shadow) {
fShadowSymbolTable = shadow;
} // setShadowSymbolTable(boolean)
// factory methods
/** Creates a new DOM parser. */
public DOMParser createDOMParser() {
SymbolTable symbolTable = fShadowSymbolTable
? new ShadowedSymbolTable(fSynchronizedSymbolTable)
: fSynchronizedSymbolTable;
XMLGrammarPool grammarPool = fShadowGrammarPool
? new ShadowedGrammarPool(fSynchronizedGrammarPool)
: fSynchronizedGrammarPool;
return new DOMParser(symbolTable, grammarPool);
} // createDOMParser():DOMParser
/** Creates a new SAX parser. */
public SAXParser createSAXParser() {
SymbolTable symbolTable = fShadowSymbolTable
? new ShadowedSymbolTable(fSynchronizedSymbolTable)
: fSynchronizedSymbolTable;
XMLGrammarPool grammarPool = fShadowGrammarPool
? new ShadowedGrammarPool(fSynchronizedGrammarPool)
: fSynchronizedGrammarPool;
return new SAXParser(symbolTable, grammarPool);
} // createSAXParser():SAXParser
//
// Classes
//
/**
* Synchronized grammar pool.
*
* @author Andy Clark, IBM
*/
public static final class SynchronizedGrammarPool
implements XMLGrammarPool {
//
// Data
//
/** Main grammar pool. */
private XMLGrammarPool fGrammarPool;
//
// Constructors
//
/** Constructs a synchronized grammar pool. */
public SynchronizedGrammarPool(XMLGrammarPool grammarPool) {
fGrammarPool = grammarPool;
} // <init>(XMLGrammarPool)
//
// GrammarPool methods
//
// retrieve the initial set of grammars for the validator
// to work with.
// REVISIT: does this need to be synchronized since it's just reading?
// @param grammarType type of the grammars to be retrieved.
// @return the initial grammar set the validator may place in its "bucket"
public Grammar [] retrieveInitialGrammarSet(String grammarType ) {
synchronized (fGrammarPool) {
return fGrammarPool.retrieveInitialGrammarSet(grammarType);
}
} // retrieveInitialGrammarSet(String): Grammar[]
// retrieve a particular grammar.
// REVISIT: does this need to be synchronized since it's just reading?
// @param gDesc description of the grammar to be retrieved
// @return Grammar corresponding to gDesc, or null if none exists.
public Grammar retrieveGrammar(XMLGrammarDescription gDesc) {
synchronized (fGrammarPool) {
return fGrammarPool.retrieveGrammar(gDesc);
}
} // retrieveGrammar(XMLGrammarDesc): Grammar
// give the grammarPool the option of caching these grammars.
// This certainly must be synchronized.
// @param grammarType The type of the grammars to be cached.
// @param grammars the Grammars that may be cached (unordered, Grammars previously
// given to the validator may be included).
public void cacheGrammars(String grammarType, Grammar[] grammars) {
synchronized (fGrammarPool) {
fGrammarPool.cacheGrammars(grammarType, grammars);
}
} // cacheGrammars(String, Grammar[]);
/** lock the grammar pool */
public void lockPool() {
synchronized (fGrammarPool) {
fGrammarPool.lockPool();
}
} // lockPool()
/** clear the grammar pool */
public void clear() {
synchronized (fGrammarPool) {
fGrammarPool.clear();
}
} // lockPool()
/** unlock the grammar pool */
public void unlockPool() {
synchronized (fGrammarPool) {
fGrammarPool.unlockPool();
}
} // unlockPool()
/***
* Methods corresponding to original (pre Xerces2.0.0final)
* grammarPool have been commented out.
*/
/**
* Puts the specified grammar into the grammar pool.
*
* @param key Key to associate with grammar.
* @param grammar Grammar object.
*/
/******
public void putGrammar(String key, Grammar grammar) {
synchronized (fGrammarPool) {
fGrammarPool.putGrammar(key, grammar);
}
} // putGrammar(String,Grammar)
*******/
/**
* Returns the grammar associated to the specified key.
*
* @param key The key of the grammar.
*/
/**********
public Grammar getGrammar(String key) {
synchronized (fGrammarPool) {
return fGrammarPool.getGrammar(key);
}
} // getGrammar(String):Grammar
***********/
/**
* Removes the grammar associated to the specified key from the
* grammar pool and returns the removed grammar.
*
* @param key The key of the grammar.
*/
/**********
public Grammar removeGrammar(String key) {
synchronized (fGrammarPool) {
return fGrammarPool.removeGrammar(key);
}
} // removeGrammar(String):Grammar
******/
/**
* Returns true if the grammar pool contains a grammar associated
* to the specified key.
*
* @param key The key of the grammar.
*/
/**********
public boolean containsGrammar(String key) {
synchronized (fGrammarPool) {
return fGrammarPool.containsGrammar(key);
}
} // containsGrammar(String):boolean
********/
} // class SynchronizedGrammarPool
/**
* Shadowed grammar pool.
* This class is predicated on the existence of a concrete implementation;
* so using our own doesn't seem to bad an idea.
*
* @author Andy Clark, IBM
* @author Neil Graham, IBM
*/
public static final class ShadowedGrammarPool
extends XMLGrammarPoolImpl {
//
// Data
//
/** Main grammar pool. */
private XMLGrammarPool fGrammarPool;
//
// Constructors
//
/** Constructs a shadowed grammar pool. */
public ShadowedGrammarPool(XMLGrammarPool grammarPool) {
fGrammarPool = grammarPool;
} // <init>(GrammarPool)
//
// GrammarPool methods
//
/**
* Retrieve the initial set of grammars for the validator to work with.
* REVISIT: does this need to be synchronized since it's just reading?
*
* @param grammarType Type of the grammars to be retrieved.
* @return The initial grammar set the validator may place in its "bucket"
*/
public Grammar [] retrieveInitialGrammarSet(String grammarType ) {
Grammar [] grammars = super.retrieveInitialGrammarSet(grammarType);
if (grammars != null) return grammars;
return fGrammarPool.retrieveInitialGrammarSet(grammarType);
} // retrieveInitialGrammarSet(String): Grammar[]
/**
* Retrieve a particular grammar.
* REVISIT: does this need to be synchronized since it's just reading?
*
* @param gDesc Description of the grammar to be retrieved
* @return Grammar corresponding to gDesc, or null if none exists.
*/
public Grammar retrieveGrammar(XMLGrammarDescription gDesc) {
Grammar g = super.retrieveGrammar(gDesc);
if(g != null) return g;
return fGrammarPool.retrieveGrammar(gDesc);
} // retrieveGrammar(XMLGrammarDesc): Grammar
/**
* Give the grammarPool the option of caching these grammars.
* This certainly must be synchronized.
*
* @param grammarType The type of the grammars to be cached.
* @param grammars The Grammars that may be cached (unordered, Grammars previously
* given to the validator may be included).
*/
public void cacheGrammars(String grammarType, Grammar[] grammars) {
// better give both grammars a shot...
super.cacheGrammars(grammarType, grammars);
fGrammarPool.cacheGrammars(grammarType, grammars);
} // cacheGrammars(grammarType, Grammar[]);
/**
* Returns the grammar associated to the specified description.
*
* @param desc The description of the grammar.
*/
public Grammar getGrammar(XMLGrammarDescription desc) {
if (super.containsGrammar(desc)) {
return super.getGrammar(desc);
}
return null;
} // getGrammar(XMLGrammarDescription):Grammar
/**
* Returns true if the grammar pool contains a grammar associated
* to the specified description.
*
* @param desc The description of the grammar.
*/
public boolean containsGrammar(XMLGrammarDescription desc) {
return super.containsGrammar(desc);
} // containsGrammar(XMLGrammarDescription):boolean
} // class ShadowedGrammarPool
} // class CachingParserPool
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