Implement EQL parser.

Implement support for EclipseLink Query Language (EQL), handling the various extensions it offers.

See #3170

spring-data-jpa/src/main/java/org/springframework/data/jpa/repository/query/EqlQueryParser.java

@@ -0,0 +1,132 @@
+/*
+ * Copyright 2022-2023 the original author or authors.
+ *
+ * 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
+ *
+ *      https://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.
+ */
+package org.springframework.data.jpa.repository.query;
+
+import java.util.List;
+
+import org.antlr.v4.runtime.CharStreams;
+import org.antlr.v4.runtime.CommonTokenStream;
+import org.antlr.v4.runtime.ParserRuleContext;
+import org.springframework.data.domain.Sort;
+import org.springframework.lang.Nullable;
+
+/**
+ * Implements the {@code EQL} parsing operations of a {@link JpaQueryParserSupport} using the ANTLR-generated
+ * {@link EqlParser} and {@link EqlQueryTransformer}.
+ *
+ * @author Greg Turnquist
+ * @since 3.2
+ */
+class EqlQueryParser extends JpaQueryParserSupport {
+
+	EqlQueryParser(String query) {
+		super(query);
+	}
+
+	/**
+	 * Convenience method to parse a EQL query. Will throw a {@link BadJpqlGrammarException} if the query is invalid.
+	 *
+	 * @param query
+	 * @return a parsed query, ready for postprocessing
+	 */
+	public static ParserRuleContext parseQuery(String query) {
+
+		EqlLexer lexer = new EqlLexer(CharStreams.fromString(query));
+		EqlParser parser = new EqlParser(new CommonTokenStream(lexer));
+
+		configureParser(query, lexer, parser);
+
+		return parser.start();
+	}
+
+	/**
+	 * Parse the query using {@link #parseQuery(String)}.
+	 *
+	 * @return a parsed query
+	 */
+	@Override
+	protected ParserRuleContext parse(String query) {
+		return parseQuery(query);
+	}
+
+	/**
+	 * Use the {@link EqlQueryTransformer} to transform the original query into a query with the {@link Sort} applied.
+	 *
+	 * @param parsedQuery
+	 * @param sort can be {@literal null}
+	 * @return list of {@link JpaQueryParsingToken}s
+	 */
+	@Override
+	protected List<JpaQueryParsingToken> applySort(ParserRuleContext parsedQuery, Sort sort) {
+		return new EqlQueryTransformer(sort).visit(parsedQuery);
+	}
+
+	/**
+	 * Use the {@link EqlQueryTransformer} to transform the original query into a count query.
+	 *
+	 * @param parsedQuery
+	 * @param countProjection
+	 * @return list of {@link JpaQueryParsingToken}s
+	 */
+	@Override
+	protected List<JpaQueryParsingToken> doCreateCountQuery(ParserRuleContext parsedQuery,
+			@Nullable String countProjection) {
+		return new EqlQueryTransformer(true, countProjection).visit(parsedQuery);
+	}
+
+	/**
+	 * Run the parsed query through {@link EqlQueryTransformer} to find the primary FROM clause's alias.
+	 *
+	 * @param parsedQuery
+	 * @return can be {@literal null}
+	 */
+	@Override
+	protected String doFindAlias(ParserRuleContext parsedQuery) {
+
+		EqlQueryTransformer transformVisitor = new EqlQueryTransformer();
+		transformVisitor.visit(parsedQuery);
+		return transformVisitor.getAlias();
+	}
+
+	/**
+	 * Use {@link EqlQueryTransformer} to find the projection of the query.
+	 *
+	 * @param parsedQuery
+	 * @return
+	 */
+	@Override
+	protected List<JpaQueryParsingToken> doFindProjection(ParserRuleContext parsedQuery) {
+
+		EqlQueryTransformer transformVisitor = new EqlQueryTransformer();
+		transformVisitor.visit(parsedQuery);
+		return transformVisitor.getProjection();
+	}
+
+	/**
+	 * Use {@link EqlQueryTransformer} to detect if the query uses a {@code new com.example.Dto()} DTO constructor in the
+	 * primary select clause.
+	 *
+	 * @param parsedQuery
+	 * @return Guaranteed to be {@literal true} or {@literal false}.
+	 */
+	@Override
+	protected boolean doCheckForConstructor(ParserRuleContext parsedQuery) {
+
+		EqlQueryTransformer transformVisitor = new EqlQueryTransformer();
+		transformVisitor.visit(parsedQuery);
+		return transformVisitor.hasConstructorExpression();
+	}
+}