聊聊spring data jpa的JpaQueryLookupStrategy

jiezi

6 年前

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 {

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 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;
}

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);

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

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