序

本文主要研究一下spring data jpa的JpaQueryLookupStrategy

QueryLookupStrategy

spring-data-commons-2.1.6.RELEASE-sources.jar!/org/springframework/data/repository/query/QueryLookupStrategy.java

public interface QueryLookupStrategy {

	public static enum Key {

		CREATE, USE_DECLARED_QUERY, CREATE_IF_NOT_FOUND;

		/**
		 * Returns a strategy key from the given XML value.
		 *
		 * @param xml
		 * @return a strategy key from the given XML value
		 */
		@Nullable
		public static Key create(String xml) {

			if (!StringUtils.hasText(xml)) {
				return null;
			}

			return valueOf(xml.toUpperCase(Locale.US).replace("-", "_"));
		}
	}

	/**
	 * Resolves a {@link RepositoryQuery} from the given {@link QueryMethod} that can be executed afterwards.
	 *
	 * @param method will never be {@literal null}.
	 * @param metadata will never be {@literal null}.
	 * @param factory will never be {@literal null}.
	 * @param namedQueries will never be {@literal null}.
	 * @return
	 */
	RepositoryQuery resolveQuery(Method method, RepositoryMetadata metadata, ProjectionFactory factory,
			NamedQueries namedQueries);
}
 

• QueryLookupStrategy定義了Key列舉，有CREATE, USE_DECLARED_QUERY, CREATE_IF_NOT_FOUND這些型別
• QueryLookupStrategy有一個抽象類為AbstractQueryLookupStrategy，它有三個實現子類，分別是CreateQueryLookupStrategy、DeclaredQueryLookupStrategy、CreateIfNotFoundQueryLookupStrategy
• QueryLookupStrategy還定義了resolveQuery方法用於將QueryMethod解析為RepositoryQuery

RepositoryQuery

spring-data-commons-2.1.6.RELEASE-sources.jar!/org/springframework/data/repository/query/RepositoryQuery.java

public interface RepositoryQuery {

	/**
	 * Executes the {@link RepositoryQuery} with the given parameters.
	 *
	 * @param parameters must not be {@literal null}.
	 * @return execution result. Can be {@literal null}.
	 */
	@Nullable
	Object execute(Object[] parameters);

	/**
	 * Returns the related {@link QueryMethod}.
	 *
	 * @return never {@literal null}.
	 */
	QueryMethod getQueryMethod();
}
 

• RepositoryQuery介面定義了兩個方法分別是execute、getQueryMethod；它有2個抽象類，一個是AbstractJpaQuery、另外一個是繼承AbstractJpaQuery的AbstractStringBasedJpaQuery；AbstractJpaQuery有3個實現子類，分別是NamedQuery、PartTreeJpaQuery、StoredProcedureJpaQuery；AbstractStringBasedJpaQuery有兩個實現子類，分別是SimpleJpaQuery及NativeJpaQuery

AbstractQueryLookupStrategy

spring-data-jpa-2.1.6.RELEASE-sources.jar!/org/springframework/data/jpa/repository/query/JpaQueryLookupStrategy.java

	/**
	 * Base class for {@link QueryLookupStrategy} implementations that need access to an {@link EntityManager}.
	 *
	 * @author Oliver Gierke
	 * @author Thomas Darimont
	 */
	private abstract static class AbstractQueryLookupStrategy implements QueryLookupStrategy {

		private final EntityManager em;
		private final QueryExtractor provider;

		/**
		 * Creates a new {@link AbstractQueryLookupStrategy}.
		 *
		 * @param em
		 * @param extractor
		 */
		public AbstractQueryLookupStrategy(EntityManager em, QueryExtractor extractor) {

			this.em = em;
			this.provider = extractor;
		}

		/*
		 * (non-Javadoc)
		 * @see org.springframework.data.repository.query.QueryLookupStrategy#resolveQuery(java.lang.reflect.Method, org.springframework.data.repository.core.RepositoryMetadata, org.springframework.data.projection.ProjectionFactory, org.springframework.data.repository.core.NamedQueries)
		 */
		@Override
		public final RepositoryQuery resolveQuery(Method method, RepositoryMetadata metadata, ProjectionFactory factory,
				NamedQueries namedQueries) {
			return resolveQuery(new JpaQueryMethod(method, metadata, factory, provider), em, namedQueries);
		}

		protected abstract RepositoryQuery resolveQuery(JpaQueryMethod method, EntityManager em, NamedQueries namedQueries);
	}

• AbstractQueryLookupStrategy實現了QueryLookupStrategy介面定義的resolveQuery方法，不過它呼叫了自己定義的抽象方法resolveQuery

CreateQueryLookupStrategy

spring-data-jpa-2.1.6.RELEASE-sources.jar!/org/springframework/data/jpa/repository/query/JpaQueryLookupStrategy.java

	/**
	 * {@link QueryLookupStrategy} to create a query from the method name.
	 *
	 * @author Oliver Gierke
	 * @author Thomas Darimont
	 */
	private static class CreateQueryLookupStrategy extends AbstractQueryLookupStrategy {

		private final PersistenceProvider persistenceProvider;
		private final EscapeCharacter escape;

		public CreateQueryLookupStrategy(EntityManager em, QueryExtractor extractor, EscapeCharacter escape) {

			super(em, extractor);

			this.persistenceProvider = PersistenceProvider.fromEntityManager(em);
			this.escape = escape;
		}

		@Override
		protected RepositoryQuery resolveQuery(JpaQueryMethod method, EntityManager em, NamedQueries namedQueries) {
			return new PartTreeJpaQuery(method, em, persistenceProvider, escape);
		}
	}

• CreateQueryLookupStrategy繼承了AbstractQueryLookupStrategy，其resolveQuery方法建立的是PartTreeJpaQuery

DeclaredQueryLookupStrategy

spring-data-jpa-2.1.6.RELEASE-sources.jar!/org/springframework/data/jpa/repository/query/JpaQueryLookupStrategy.java

	/**
	 * {@link QueryLookupStrategy} that tries to detect a declared query declared via {@link Query} annotation followed by
	 * a JPA named query lookup.
	 *
	 * @author Oliver Gierke
	 * @author Thomas Darimont
	 */
	private static class DeclaredQueryLookupStrategy extends AbstractQueryLookupStrategy {

		private final QueryMethodEvaluationContextProvider evaluationContextProvider;

		/**
		 * Creates a new {@link DeclaredQueryLookupStrategy}.
		 *
		 * @param em
		 * @param extractor
		 * @param evaluationContextProvider
		 */
		public DeclaredQueryLookupStrategy(EntityManager em, QueryExtractor extractor,
				QueryMethodEvaluationContextProvider evaluationContextProvider) {

			super(em, extractor);
			this.evaluationContextProvider = evaluationContextProvider;
		}

		/*
		 * (non-Javadoc)
		 * @see org.springframework.data.jpa.repository.query.JpaQueryLookupStrategy.AbstractQueryLookupStrategy#resolveQuery(org.springframework.data.jpa.repository.query.JpaQueryMethod, javax.persistence.EntityManager, org.springframework.data.repository.core.NamedQueries)
		 */
		@Override
		protected RepositoryQuery resolveQuery(JpaQueryMethod method, EntityManager em, NamedQueries namedQueries) {

			RepositoryQuery query = JpaQueryFactory.INSTANCE.fromQueryAnnotation(method, em, evaluationContextProvider);

			if (null != query) {
				return query;
			}

			query = JpaQueryFactory.INSTANCE.fromProcedureAnnotation(method, em);

			if (null != query) {
				return query;
			}

			String name = method.getNamedQueryName();
			if (namedQueries.hasQuery(name)) {
				return JpaQueryFactory.INSTANCE.fromMethodWithQueryString(method, em, namedQueries.getQuery(name),
						evaluationContextProvider);
			}

			query = NamedQuery.lookupFrom(method, em);

			if (null != query) {
				return query;
			}

			throw new IllegalStateException(
					String.format("Did neither find a NamedQuery nor an annotated query for method %s!", method));
		}
	}

• DeclaredQueryLookupStrategy繼承了AbstractQueryLookupStrategy，其resolveQuery方法藉助JpaQueryFactory.INSTANCE.fromQueryAnnotation、JpaQueryFactory.INSTANCE.fromProcedureAnnotation、NamedQuery.lookupFrom來生成

CreateIfNotFoundQueryLookupStrategy

spring-data-jpa-2.1.6.RELEASE-sources.jar!/org/springframework/data/jpa/repository/query/JpaQueryLookupStrategy.java

	/**
	 * {@link QueryLookupStrategy} to try to detect a declared query first (
	 * {@link org.springframework.data.jpa.repository.Query}, JPA named query). In case none is found we fall back on
	 * query creation.
	 *
	 * @author Oliver Gierke
	 * @author Thomas Darimont
	 */
	private static class CreateIfNotFoundQueryLookupStrategy extends AbstractQueryLookupStrategy {

		private final DeclaredQueryLookupStrategy lookupStrategy;
		private final CreateQueryLookupStrategy createStrategy;

		/**
		 * Creates a new {@link CreateIfNotFoundQueryLookupStrategy}.
		 *
		 * @param em
		 * @param extractor
		 * @param createStrategy
		 * @param lookupStrategy
		 */
		public CreateIfNotFoundQueryLookupStrategy(EntityManager em, QueryExtractor extractor,
				CreateQueryLookupStrategy createStrategy, DeclaredQueryLookupStrategy lookupStrategy) {

			super(em, extractor);

			this.createStrategy = createStrategy;
			this.lookupStrategy = lookupStrategy;
		}

		/*
		 * (non-Javadoc)
		 * @see org.springframework.data.jpa.repository.query.JpaQueryLookupStrategy.AbstractQueryLookupStrategy#resolveQuery(org.springframework.data.jpa.repository.query.JpaQueryMethod, javax.persistence.EntityManager, org.springframework.data.repository.core.NamedQueries)
		 */
		@Override
		protected RepositoryQuery resolveQuery(JpaQueryMethod method, EntityManager em, NamedQueries namedQueries) {

			try {
				return lookupStrategy.resolveQuery(method, em, namedQueries);
			} catch (IllegalStateException e) {
				return createStrategy.resolveQuery(method, em, namedQueries);
			}
		}
	}

• CreateIfNotFoundQueryLookupStrategy繼承了AbstractQueryLookupStrategy，它的構造器要求傳入DeclaredQueryLookupStrategy、CreateQueryLookupStrategy引數，其resolveQuery方法先是藉助DeclaredQueryLookupStrategy來建立RepositoryQuery，如果丟擲的是IllegalStateException，再借助CreateQueryLookupStrategy來建立RepositoryQuery

JpaQueryLookupStrategy

spring-data-jpa-2.1.6.RELEASE-sources.jar!/org/springframework/data/jpa/repository/query/JpaQueryLookupStrategy.java

public final class JpaQueryLookupStrategy {

	/**
	 * Private constructor to prevent instantiation.
	 */
	private JpaQueryLookupStrategy() {}

	//......

	/**
	 * Creates a {@link QueryLookupStrategy} for the given {@link EntityManager} and {@link Key}.
	 *
	 * @param em must not be {@literal null}.
	 * @param key may be {@literal null}.
	 * @param extractor must not be {@literal null}.
	 * @param evaluationContextProvider must not be {@literal null}.
	 * @param escape
	 * @return
	 */
	public static QueryLookupStrategy create(EntityManager em, @Nullable Key key, QueryExtractor extractor,
			QueryMethodEvaluationContextProvider evaluationContextProvider, EscapeCharacter escape) {

		Assert.notNull(em, "EntityManager must not be null!");
		Assert.notNull(extractor, "QueryExtractor must not be null!");
		Assert.notNull(evaluationContextProvider, "EvaluationContextProvider must not be null!");

		switch (key != null ? key : Key.CREATE_IF_NOT_FOUND) {
			case CREATE:
				return new CreateQueryLookupStrategy(em, extractor, escape);
			case USE_DECLARED_QUERY:
				return new DeclaredQueryLookupStrategy(em, extractor, evaluationContextProvider);
			case CREATE_IF_NOT_FOUND:
				return new CreateIfNotFoundQueryLookupStrategy(em, extractor,
						new CreateQueryLookupStrategy(em, extractor, escape),
						new DeclaredQueryLookupStrategy(em, extractor, evaluationContextProvider));
			default:
				throw new IllegalArgumentException(String.format("Unsupported query lookup strategy %s!", key));
		}
	}
}

• JpaQueryLookupStrategy提供一個靜態方法create用於根據不同的QueryLookupStrategy.Key來建立不同的QueryLookupStrategy，預設是Key.CREATE_IF_NOT_FOUND，即建立CreateIfNotFoundQueryLookupStrategy

小結

• QueryLookupStrategy定義了Key列舉，有CREATE, USE_DECLARED_QUERY, CREATE_IF_NOT_FOUND這些型別；QueryLookupStrategy有一個抽象類為AbstractQueryLookupStrategy，它有三個實現子類，分別是CreateQueryLookupStrategy、DeclaredQueryLookupStrategy、CreateIfNotFoundQueryLookupStrategy；QueryLookupStrategy還定義了resolveQuery方法用於將QueryMethod解析為RepositoryQuery
• AbstractQueryLookupStrategy實現了QueryLookupStrategy介面定義的resolveQuery方法，不過它呼叫了自己定義的抽象方法resolveQuery
  • CreateQueryLookupStrategy繼承了AbstractQueryLookupStrategy，其resolveQuery方法建立的是PartTreeJpaQuery(解析方法名)；
  • DeclaredQueryLookupStrategy繼承了AbstractQueryLookupStrategy，其resolveQuery方法藉助JpaQueryFactory.INSTANCE.fromQueryAnnotation(解析@Query註解)、JpaQueryFactory.INSTANCE.fromProcedureAnnotation(解析@Procedure註解)、NamedQuery.lookupFrom(解析@NamedQuery註解)來生成；
  • CreateIfNotFoundQueryLookupStrategy繼承了AbstractQueryLookupStrategy，它的構造器要求傳入DeclaredQueryLookupStrategy、CreateQueryLookupStrategy引數，其resolveQuery方法先是藉助DeclaredQueryLookupStrategy來建立RepositoryQuery，如果丟擲的是IllegalStateException，再借助CreateQueryLookupStrategy來建立RepositoryQuery
• JpaQueryLookupStrategy提供一個靜態方法create用於根據不同的QueryLookupStrategy.Key來建立不同的QueryLookupStrategy，預設是Key.CREATE_IF_NOT_FOUND，即建立CreateIfNotFoundQueryLookupStrategy

doc

• JpaQueryLook