聊聊spring data jpa的JpaQueryLookupStrategy

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定义了Key枚举，有CREATE, USE_DECLARED_QUERY, CREATE_IF_NOT_FOUND这些类型
• QueryLookupStrategy有一个抽象类为AbstractQueryLookupStrategy，它有三个实现子类，分别是CreateQueryLookupStrategy、DeclaredQueryLookupStrategy、CreateIfNotFoundQueryLookupStrategy
• QueryLookupStrategy还定义了resolveQuery方法用于将QueryMethod解析为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接口定义了两个方法分别是execute、getQueryMethod；它有2个抽象类，一个是AbstractJpaQuery、另外一个是继承AbstractJpaQuery的AbstractStringBasedJpaQuery；AbstractJpaQuery有3个实现子类，分别是NamedQuery、PartTreeJpaQuery、StoredProcedureJpaQuery；AbstractStringBasedJpaQuery有两个实现子类，分别是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实现了QueryLookupStrategy接口定义的resolveQuery方法，不过它调用了自己定义的抽象方法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 {
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 private final PersistenceProvider persistenceProvider;
 private final EscapeCharacter escape;
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 public CreateQueryLookupStrategy(EntityManager em, QueryExtractor extractor, EscapeCharacter escape) {
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 super(em, extractor);
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 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继承了AbstractQueryLookupStrategy，其resolveQuery方法创建的是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;
 }
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 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继承了AbstractQueryLookupStrategy，其resolveQuery方法借助JpaQueryFactory.INSTANCE.fromQueryAnnotation、JpaQueryFactory.INSTANCE.fromProcedureAnnotation、NamedQuery.lookupFrom来生成

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);
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 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继承了AbstractQueryLookupStrategy，它的构造器要求传入DeclaredQueryLookupStrategy、CreateQueryLookupStrategy参数，其resolveQuery方法先是借助DeclaredQueryLookupStrategy来创建RepositoryQuery，如果抛出的是IllegalStateException，再借助CreateQueryLookupStrategy来创建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提供一个静态方法create用于根据不同的QueryLookupStrategy.Key来创建不同的QueryLookupStrategy，默认是Key.CREATE_IF_NOT_FOUND，即创建CreateIfNotFoundQueryLookupStrategy

小结

• QueryLookupStrategy定义了Key枚举，有CREATE, USE_DECLARED_QUERY, CREATE_IF_NOT_FOUND这些类型；QueryLookupStrategy有一个抽象类为AbstractQueryLookupStrategy，它有三个实现子类，分别是CreateQueryLookupStrategy、DeclaredQueryLookupStrategy、CreateIfNotFoundQueryLookupStrategy；QueryLookupStrategy还定义了resolveQuery方法用于将QueryMethod解析为RepositoryQuery
• AbstractQueryLookupStrategy实现了QueryLookupStrategy接口定义的resolveQuery方法，不过它调用了自己定义的抽象方法resolveQuery
• CreateQueryLookupStrategy继承了AbstractQueryLookupStrategy，其resolveQuery方法创建的是PartTreeJpaQuery(解析方法名)；
• DeclaredQueryLookupStrategy继承了AbstractQueryLookupStrategy，其resolveQuery方法借助JpaQueryFactory.INSTANCE.fromQueryAnnotation(解析@Query注解)、JpaQueryFactory.INSTANCE.fromProcedureAnnotation(解析@Procedure注解)、NamedQuery.lookupFrom(解析@NamedQuery注解)来生成；
• CreateIfNotFoundQueryLookupStrategy继承了AbstractQueryLookupStrategy，它的构造器要求传入DeclaredQueryLookupStrategy、CreateQueryLookupStrategy参数，其resolveQuery方法先是借助DeclaredQueryLookupStrategy来创建RepositoryQuery，如果抛出的是IllegalStateException，再借助CreateQueryLookupStrategy来创建RepositoryQuery
• JpaQueryLookupStrategy提供一个静态方法create用于根据不同的QueryLookupStrategy.Key来创建不同的QueryLookupStrategy，默认是Key.CREATE_IF_NOT_FOUND，即创建CreateIfNotFoundQueryLookupStrategy

doc

• JpaQueryLookupStrategy