/*******************************************************************************
* Copyright (c) 2011, 2015 Oracle and/or its affiliates. All rights reserved.
* This program and the accompanying materials are made available under the
* terms of the Eclipse Public License v1.0 and Eclipse Distribution License v. 1.0
* which accompanies this distribution.
* The Eclipse Public License is available at http://www.eclipse.org/legal/epl-v10.html
* and the Eclipse Distribution License is available at
* http://www.eclipse.org/org/documents/edl-v10.php.
*
* Contributors:
* Oracle - initial API and implementation
*
******************************************************************************/
package org.eclipse.persistence.jpa.jpql.parser;
import org.eclipse.persistence.jpa.jpql.JPAVersion;
/**
* <p>The abstract definition of a {@link JPQLGrammar}. The grammar defines how a JPQL query is parsed,
* which is based on the BNF defined for that grammar.</p>
*
* <p>Provisional API: This interface is part of an interim API that is still under development and
* expected to change significantly before reaching stability. It is available at this early stage
* to solicit feedback from pioneering adopters on the understanding that any code that uses this
* API will almost certainly be broken (repeatedly) as the API evolves.</p>
*
* @version 2.5
* @since 2.4
* @author Pascal Filion
*/
public abstract class AbstractJPQLGrammar implements JPQLGrammar {
/**
* The base {@link JPQLGrammar} this one extends or <code>null</code> if this is the base grammar.
*/
private JPQLGrammar jpqlGrammar;
/**
* The registry contains the {@link JPQLQueryBNF JPQLQueryBNFs} and the {@link ExpressionFactory
* ExpressionFactories} and the support JPQL identifiers.
*/
private ExpressionRegistry registry;
/**
* Creates a new <code>AbstractJPQLGrammar</code>.
*/
protected AbstractJPQLGrammar() {
super();
initialize();
}
/**
* Creates a new <code>AbstractJPQLGrammar</code>.
*
* @param jpqlGrammar The {@link JPQLGrammar} to extend with the content of this one without
* instantiating the base {@link JPQLGrammar}
*/
protected AbstractJPQLGrammar(AbstractJPQLGrammar jpqlGrammar) {
super();
initialize(jpqlGrammar);
}
/**
* Adds to the given query BNF a child BNF.
*
* @param queryBNFId The unique identifier of the parent BNF to add a child BNF
* @param childQueryBNFId The unique identifier of the child to add to the parent BNF
*/
public void addChildBNF(String queryBNFId, String childQueryBNFId) {
registry.addChildBNF(queryBNFId, childQueryBNFId);
}
/**
* Adds to the given unique identifier of an {@link ExpressionFactory} to the given query BNF.
*
* @param queryBNFId The unique identifier of the parent BNF
* @param childExpressionFactoryId The unique identifier of the {@link ExpressionFactory} to add
* to the given query BNF
*/
public void addChildFactory(String queryBNFId, String childExpressionFactoryId) {
registry.addChildFactory(queryBNFId, childExpressionFactoryId);
}
/**
* Adds the given JPQL identifier to this factory.
*
* @param expressionFactoryId The unique identifier of the {@link ExpressionFactory} to add more
* JPQL identifiers
* @param identifier The JPQL identifier this factory will parse
*/
public void addIdentifier(String expressionFactoryId, String identifier) {
registry.addIdentifier(expressionFactoryId, identifier);
}
/**
* Adds the given JPQL identifiers to this factory.
*
* @param expressionFactoryId The unique identifier of the {@link ExpressionFactory} to add more
* JPQL identifiers
* @param identifiers The JPQL identifiers this factory will parse
*/
public void addIdentifiers(String expressionFactoryId, String... identifiers) {
registry.addIdentifiers(expressionFactoryId, identifiers);
}
/**
* Creates the base {@link JPQLGrammar} this one extends, if one exists.
* <p>
* <b>IMPORTANT:</b> The singleton instance of any {@link JPQLGrammar} (for example {@link
* JPQLGrammar1_0#instance() JPQLGrammar1_0.instance()} cannot be used, the API does not support
* extending it, a new instance has to be created.
*
* @return The base {@link JPQLGrammar} or <code>null</code> if there is no base grammar
*/
protected abstract JPQLGrammar buildBaseGrammar();
/**
* Creates a new {@link ExpressionRegistry} that will be used to store the definition of the JPQL
* grammar. This method is invoked if {@link #buildBaseGrammar()} returns <code>null</code>.
*
* @return The registry of {@link JPQLQueryBNF JPQLQueryBNFs}, {@link ExpressionFactory
* ExpressionFactories} and the JPQL identifiers
*/
protected ExpressionRegistry buildExpressionRegistry() {
return new ExpressionRegistry();
}
/**
* Creates the base {@link JPQLGrammar} this one extends.
*
* @return The base {@link JPQLGrammar} or <code>null</code> if this is the base grammar
*/
public JPQLGrammar getBaseGrammar() {
return jpqlGrammar;
}
/**
* {@inheritDoc}
*/
public ExpressionRegistry getExpressionRegistry() {
return registry;
}
/**
* Initializes this JPQL grammar.
*/
protected void initialize() {
// Create the base grammar, if this one is an extension
jpqlGrammar = buildBaseGrammar();
// There is no base grammar, create the local ExpressionRegistry
if (jpqlGrammar == null) {
registry = buildExpressionRegistry();
}
// This grammar extends another grammar, simply use the base grammar's
// ExpressionRegistry so this grammar can modify it
else {
registry = jpqlGrammar.getExpressionRegistry();
}
// Add the support provided by this grammar
initializeIdentifiers();
initializeBNFs();
initializeExpressionFactories();
}
/**
* This method simply retrieves the {@link ExpressionRegistry} from the given {@link JPQLGrammar}
* and extend its grammar by calling the initialize methods from this one.
*
* @param jpqlGrammar The {@link JPQLGrammar} to extend with the content of this one without
* instantiating the base {@link JPQLGrammar}
*/
private void initialize(AbstractJPQLGrammar jpqlGrammar) {
registry = jpqlGrammar.registry;
// Add the support provided by this grammar
initializeIdentifiers();
initializeBNFs();
initializeExpressionFactories();
}
/**
* Registers the JPQL query BNFs defining the JPQL grammar.
*/
protected abstract void initializeBNFs();
/**
* Registers the {@link ExpressionFactory ExpressionFactories} required to properly parse JPQL
* queries. An {@link ExpressionFactory} is responsible to create an {@link Expression} object
* that represents a portion of the JPQL query.
*/
protected abstract void initializeExpressionFactories();
/**
* Registers the JPQL identifiers support by this {@link JPQLGrammar}. The registration
* involves registering the {@link JPAVersion} and the {@link IdentifierRole}.
*/
protected abstract void initializeIdentifiers();
/**
* Registers the given {@link JPQLQueryBNF}. The BNF will be registered using its unique
* identifier.
*
* @param queryBNF The {@link JPQLQueryBNF} to store
*/
protected void registerBNF(JPQLQueryBNF queryBNF) {
registry.registerBNF(queryBNF);
}
/**
* Registers the given {@link ExpressionFactory} by storing it for all its identifiers.
*
* @param expressionFactory The {@link ExpressionFactory} to store
*/
protected void registerFactory(ExpressionFactory expressionFactory) {
registry.registerFactory(expressionFactory);
}
/**
* Registers the {@link IdentifierRole} for the given JPQL identifier.
*
* @param identifier The JPQL identifier to register its role within a JPQL query
* @param role The role of the given JPQL identifier
*/
protected void registerIdentifierRole(String identifier, IdentifierRole role) {
registry.registerIdentifierRole(identifier, role);
}
/**
* Registers the {@link JPAVersion} for which the given JPQL identifier was defined.
*
* @param identifier The JPQL identifier to register in which version it was added to the grammar
* @param version The version when the JPQL identifier was added to the grammar
*/
protected void registerIdentifierVersion(String identifier, JPAVersion version) {
registry.registerIdentifierVersion(identifier, version);
}
/**
* When parsing the query and no {@link JPQLQueryBNF JPQLQueryBNFs} can help to parse the query,
* then it will fall back on the given one.
*
* @param queryBNFId The unique identifier of the BNF to modify its fallback BNF unique identifier
* @param fallbackBNFId The unique identifier of the {@link JPQLQueryBNF} to use in the last resort
*/
public void setFallbackBNFId(String queryBNFId, String fallbackBNFId) {
registry.setFallbackBNFId(queryBNFId, fallbackBNFId);
}
/**
* Sets the unique identifier of the {@link ExpressionFactory} to use when the fall back BNF
* ID is not <code>null</code>. This will be used to parse a portion of the query when the
* registered {@link ExpressionFactory expression factories} cannot parse it.
* <p>
* Note: This method is only called if {@link JPQLQueryBNF#getFallbackBNFId() JPQLQueryBNF.
* getFallbackBNFId()} does not return <code>null</code>.
*
* @param queryBNFId The unique identifier of the BNF to modify its fallback expression factory
* unique identifier
*/
public void setFallbackExpressionFactoryId(String queryBNFId, String fallbackExpressionFactoryId) {
registry.setFallbackExpressionFactoryId(queryBNFId, fallbackExpressionFactoryId);
}
/**
* Determines whether the <code>Expression</code> handles a collection of sub-expressions that
* are separated by commas.
*
* @param queryBNFId The unique identifier of the {@link JPQLQueryBNF}
* @param handleCollection <code>true</code> if the sub-expression to parse might have several
* sub-expressions separated by commas; <code>false</code> otherwise
*/
public void setHandleCollection(String queryBNFId, boolean handleCollection) {
registry.setHandleCollection(queryBNFId, handleCollection);
}
/**
* Sets whether the BNF with the given ID supports nested array or not. A nested array is a sub-
* expression with its child being a collection expression: (item_1, item_2, ..., item_n).
*
* @param queryBNFId The unique identifier of the {@link JPQLQueryBNF}
* @param handleNestedArray <code>true</code> if the expression represented by this BNF can be
* a nested array; <code>false</code> otherwise
* @since 2.5
*/
public void setHandleNestedArray(String queryBNFId, boolean handleNestedArray) {
registry.setHandleNestedArray(queryBNFId, handleNestedArray);
}
/**
* Sets whether the query BNF with the given ID handles parsing a sub-expression, i.e. parsing an
* expression encapsulated by parenthesis. Which in fact would be handled by the fallback {@link
* ExpressionFactory}. The default behavior is to not handle it.
* <p>
* A good example for using this option is when an {@link Expression} cannot use any {@link
* ExpressionFactory} for creating a child object, parsing will use the fallback {@link
* ExpressionFactory}, if one was specified. So when this is set to <code>true</code>, the
* fallback {@link ExpressionFactory} will be immediately invoked.
* <p>
* Let's say we want to parse "SELECT e FROM (SELECT a FROM Address a) e", {@link FromClause}
* cannot use a factory for parsing the entity name (that's what usually the <code>FROM</code>
* clause has) so it uses the fallback factory to create {@link IdentificationVariableDeclaration}.
* Then <code>IdentificationVariableDeclaration</code> also cannot use any factory to create its
* child object so it uses the fallback factory to create {@link RangeVariableDeclaration}.
* By changing the status of for handling the sub-expression for the BNFs for those objects, then
* a subquery can be created by <code>RangeVariableDeclaration</code>.
*
* <pre><code>FromClause
* |- IdentificationVariableDeclaration
* |- RangeVariableDeclaration
* |- SubExpression(subquery)</code></pre>
*
* In order to get this working, the following would have to be done into the grammar:
*
* <pre><code> public class MyJPQLGrammar extends AbstractJPQLGrammar {
* @Override
* protected void initializeBNFs() {
* setHandleSubExpression(InternalFromClauseBNF.ID, true);
* setHandleSubExpression(InternalSimpleFromClauseBNF.ID, true);
* setHandleSubExpression(IdentificationVariableDeclarationBNF.ID, true);
* setHandleSubExpression(RangeVariableDeclarationBNF.ID, true);
* }
* }</code></pre>
*
* @param queryBNFId The unique identifier of the {@link JPQLQueryBNF}
* @param handleSubExpression <code>true</code> to let the creation of a sub-expression be
* created by the fallback {@link ExpressionFactory} registered with this BNF; <code>false</code>
* otherwise (which is the default value)
*/
public void setHandleSubExpression(String queryBNFId, boolean handleSubExpression) {
registry.setHandleSubExpression(queryBNFId, handleSubExpression);
}
}