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聊聊spring data jpa的SimpleJpaRepository

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

JpaRepositoryImplementation

spring-data-jpa-2.1.6.RELEASE-sources.jar!/org/springframework/data/jpa/repository/support/JpaRepositoryImplementation.java

/**
 * SPI interface to be implemented by {@link JpaRepository} implementations.
 *
 * @author Oliver Gierke
 * @author Stefan Fussenegger
 */
@NoRepositoryBean
public interface JpaRepositoryImplementation<T, ID> extends JpaRepository<T, ID>, JpaSpecificationExecutor<T> {

    /**
     * Configures the {@link CrudMethodMetadata} to be used with the repository.
     *
     * @param crudMethodMetadata must not be {@literal null}.
     */
    void setRepositoryMethodMetadata(CrudMethodMetadata crudMethodMetadata);
}

JpaRepositoryImplementation接口继承了JpaRepository及JpaSpecificationExecutor，它是JpaRepository接口实现类的SPI interface；它定义了setRepositoryMethodMetadata方法

SimpleJpaRepository

spring-data-jpa-2.1.6.RELEASE-sources.jar!/org/springframework/data/jpa/repository/support/SimpleJpaRepository.java

@Repository
@Transactional(readOnly = true)
public class SimpleJpaRepository<T, ID> implements JpaRepositoryImplementation<T, ID> {

    private static final String ID_MUST_NOT_BE_NULL = "The given id must not be null!";

    private final JpaEntityInformation<T, ?> entityInformation;
    private final EntityManager em;
    private final PersistenceProvider provider;

    private @Nullable CrudMethodMetadata metadata;

    /**
     * Creates a new {@link SimpleJpaRepository} to manage objects of the given {@link JpaEntityInformation}.
     *
     * @param entityInformation must not be {@literal null}.
     * @param entityManager must not be {@literal null}.
     */
    public SimpleJpaRepository(JpaEntityInformation<T, ?> entityInformation, EntityManager entityManager) {

        Assert.notNull(entityInformation, "JpaEntityInformation must not be null!");
        Assert.notNull(entityManager, "EntityManager must not be null!");

        this.entityInformation = entityInformation;
        this.em = entityManager;
        this.provider = PersistenceProvider.fromEntityManager(entityManager);
    }

    /**
     * Creates a new {@link SimpleJpaRepository} to manage objects of the given domain type.
     *
     * @param domainClass must not be {@literal null}.
     * @param em must not be {@literal null}.
     */
    public SimpleJpaRepository(Class<T> domainClass, EntityManager em) {
        this(JpaEntityInformationSupport.getEntityInformation(domainClass, em), em);
    }

    /**
     * Configures a custom {@link CrudMethodMetadata} to be used to detect {@link LockModeType}s and query hints to be
     * applied to queries.
     *
     * @param crudMethodMetadata
     */
    public void setRepositoryMethodMetadata(CrudMethodMetadata crudMethodMetadata) {
        this.metadata = crudMethodMetadata;
    }

    @Nullable
    protected CrudMethodMetadata getRepositoryMethodMetadata() {
        return metadata;
    }

    //......

    /*
     * (non-Javadoc)
     * @see org.springframework.data.repository.CrudRepository#delete(java.io.Serializable)
     */
    @Transactional
    public void deleteById(ID id) {

        Assert.notNull(id, ID_MUST_NOT_BE_NULL);

        delete(findById(id).orElseThrow(() -> new EmptyResultDataAccessException(
                String.format("No %s entity with id %s exists!", entityInformation.getJavaType(), id), 1)));
    }

    /*
     * (non-Javadoc)
     * @see org.springframework.data.repository.CrudRepository#delete(java.lang.Object)
     */
    @Transactional
    public void delete(T entity) {

        Assert.notNull(entity, "The entity must not be null!");
        em.remove(em.contains(entity) ? entity : em.merge(entity));
    }

    /*
     * (non-Javadoc)
     * @see org.springframework.data.repository.CrudRepository#delete(java.lang.Iterable)
     */
    @Transactional
    public void deleteAll(Iterable<? extends T> entities) {

        Assert.notNull(entities, "The given Iterable of entities not be null!");

        for (T entity : entities) {
            delete(entity);
        }
    }

    /*
     * (non-Javadoc)
     * @see org.springframework.data.jpa.repository.JpaRepository#deleteInBatch(java.lang.Iterable)
     */
    @Transactional
    public void deleteInBatch(Iterable<T> entities) {

        Assert.notNull(entities, "The given Iterable of entities not be null!");

        if (!entities.iterator().hasNext()) {
            return;
        }

        applyAndBind(getQueryString(DELETE_ALL_QUERY_STRING, entityInformation.getEntityName()), entities, em)
                .executeUpdate();
    }

    /*
     * (non-Javadoc)
     * @see org.springframework.data.repository.Repository#deleteAll()
     */
    @Transactional
    public void deleteAll() {

        for (T element : findAll()) {
            delete(element);
        }
    }

    /*
     * (non-Javadoc)
     * @see org.springframework.data.jpa.repository.JpaRepository#deleteAllInBatch()
     */
    @Transactional
    public void deleteAllInBatch() {
        em.createQuery(getDeleteAllQueryString()).executeUpdate();
    }

    //......

    /*
     * (non-Javadoc)
     * @see org.springframework.data.repository.CrudRepository#save(java.lang.Object)
     */
    @Transactional
    public <S extends T> S save(S entity) {

        if (entityInformation.isNew(entity)) {
            em.persist(entity);
            return entity;
        } else {
            return em.merge(entity);
        }
    }

    /*
     * (non-Javadoc)
     * @see org.springframework.data.jpa.repository.JpaRepository#saveAndFlush(java.lang.Object)
     */
    @Transactional
    public <S extends T> S saveAndFlush(S entity) {

        S result = save(entity);
        flush();

        return result;
    }

    /*
     * (non-Javadoc)
     * @see org.springframework.data.jpa.repository.JpaRepository#save(java.lang.Iterable)
     */
    @Transactional
    public <S extends T> List<S> saveAll(Iterable<S> entities) {

        Assert.notNull(entities, "The given Iterable of entities not be null!");

        List<S> result = new ArrayList<S>();

        for (S entity : entities) {
            result.add(save(entity));
        }

        return result;
    }

    /*
     * (non-Javadoc)
     * @see org.springframework.data.jpa.repository.JpaRepository#flush()
     */
    @Transactional
    public void flush() {
        em.flush();
    }

    //......

    /*
     * (non-Javadoc)
     * @see org.springframework.data.repository.CrudRepository#findById(java.io.Serializable)
     */
    public Optional<T> findById(ID id) {

        Assert.notNull(id, ID_MUST_NOT_BE_NULL);

        Class<T> domainType = getDomainClass();

        if (metadata == null) {
            return Optional.ofNullable(em.find(domainType, id));
        }

        LockModeType type = metadata.getLockModeType();

        Map<String, Object> hints = getQueryHints().withFetchGraphs(em).asMap();

        return Optional.ofNullable(type == null ? em.find(domainType, id, hints) : em.find(domainType, id, type, hints));
    }

    /*
     * (non-Javadoc)
     * @see org.springframework.data.jpa.repository.JpaRepository#getOne(java.io.Serializable)
     */
    @Override
    public T getOne(ID id) {

        Assert.notNull(id, ID_MUST_NOT_BE_NULL);
        return em.getReference(getDomainClass(), id);
    }

    /**
     * Applies the given {@link Specification} to the given {@link CriteriaQuery}.
     *
     * @param spec can be {@literal null}.
     * @param domainClass must not be {@literal null}.
     * @param query must not be {@literal null}.
     * @return
     */
    private <S, U extends T> Root<U> applySpecificationToCriteria(@Nullable Specification<U> spec, Class<U> domainClass,
            CriteriaQuery<S> query) {

        Assert.notNull(domainClass, "Domain class must not be null!");
        Assert.notNull(query, "CriteriaQuery must not be null!");

        Root<U> root = query.from(domainClass);

        if (spec == null) {
            return root;
        }

        CriteriaBuilder builder = em.getCriteriaBuilder();
        Predicate predicate = spec.toPredicate(root, query, builder);

        if (predicate != null) {
            query.where(predicate);
        }

        return root;
    }
    //......
}

SimpleJpaRepository实现了JpaRepositoryImplementation接口，它是CrudRepository的默认实现；它的构造器都要求传入EntityManager
它的类上注解了@Transactional(readOnly = true)；而对deleteById、delete、deleteAll、deleteInBatch、deleteAllInBatch、save、saveAndFlush、saveAll、flush都添加了@Transactional注解
从各个方法的实现可以看到SimpleJpaRepository是使用EntityManager来完成具体的方法功能，对于查询功能很多都借助了applySpecificationToCriteria方法，将spring data的Specification转换为javax.persistence的CriteriaQuery

JpaRepositoryFactory

spring-data-jpa-2.1.6.RELEASE-sources.jar!/org/springframework/data/jpa/repository/support/JpaRepositoryFactory.java

public class JpaRepositoryFactory extends RepositoryFactorySupport {

    private final EntityManager entityManager;
    private final QueryExtractor extractor;
    private final CrudMethodMetadataPostProcessor crudMethodMetadataPostProcessor;

    private EntityPathResolver entityPathResolver;
    private EscapeCharacter escapeCharacter = EscapeCharacter.of('//');

    /**
     * Creates a new {@link JpaRepositoryFactory}.
     *
     * @param entityManager must not be {@literal null}
     */
    public JpaRepositoryFactory(EntityManager entityManager) {

        Assert.notNull(entityManager, "EntityManager must not be null!");

        this.entityManager = entityManager;
        this.extractor = PersistenceProvider.fromEntityManager(entityManager);
        this.crudMethodMetadataPostProcessor = new CrudMethodMetadataPostProcessor();
        this.entityPathResolver = SimpleEntityPathResolver.INSTANCE;

        addRepositoryProxyPostProcessor(crudMethodMetadataPostProcessor);

        if (extractor.equals(PersistenceProvider.ECLIPSELINK)) {
            addQueryCreationListener(new EclipseLinkProjectionQueryCreationListener(entityManager));
        }
    }

    //......

    /*
     * (non-Javadoc)
     * @see org.springframework.data.repository.core.support.RepositoryFactorySupport#getTargetRepository(org.springframework.data.repository.core.RepositoryMetadata)
     */
    @Override
    protected final JpaRepositoryImplementation<?, ?> getTargetRepository(RepositoryInformation information) {

        JpaRepositoryImplementation<?, ?> repository = getTargetRepository(information, entityManager);
        repository.setRepositoryMethodMetadata(crudMethodMetadataPostProcessor.getCrudMethodMetadata());

        return repository;
    }

    /**
     * Callback to create a {@link JpaRepository} instance with the given {@link EntityManager}
     *
     * @param information will never be {@literal null}.
     * @param entityManager will never be {@literal null}.
     * @return
     */
    protected JpaRepositoryImplementation<?, ?> getTargetRepository(RepositoryInformation information,
            EntityManager entityManager) {

        JpaEntityInformation<?, Serializable> entityInformation = getEntityInformation(information.getDomainType());
        Object repository = getTargetRepositoryViaReflection(information, entityInformation, entityManager);

        Assert.isInstanceOf(JpaRepositoryImplementation.class, repository);

        return (JpaRepositoryImplementation<?, ?>) repository;
    }

    //......
}

JpaRepositoryFactory的getTargetRepository会根据RepositoryInformation创建JpaRepositoryImplementation，这里默认创建的是SimpleJpaRepository实例

RepositoryFactorySupport

spring-data-commons-2.1.6.RELEASE-sources.jar!/org/springframework/data/repository/core/support/RepositoryFactorySupport.java

public abstract class RepositoryFactorySupport implements BeanClassLoaderAware, BeanFactoryAware {

    //......

    /**
     * Returns a repository instance for the given interface backed by an instance providing implementation logic for
     * custom logic.
     *
     * @param repositoryInterface must not be {@literal null}.
     * @param fragments must not be {@literal null}.
     * @return
     * @since 2.0
     */
    @SuppressWarnings({ "unchecked" })
    public <T> T getRepository(Class<T> repositoryInterface, RepositoryFragments fragments) {

        if (LOG.isDebugEnabled()) {
            LOG.debug("Initializing repository instance for {}…", repositoryInterface.getName());
        }

        Assert.notNull(repositoryInterface, "Repository interface must not be null!");
        Assert.notNull(fragments, "RepositoryFragments must not be null!");

        RepositoryMetadata metadata = getRepositoryMetadata(repositoryInterface);
        RepositoryComposition composition = getRepositoryComposition(metadata, fragments);
        RepositoryInformation information = getRepositoryInformation(metadata, composition);

        validate(information, composition);

        Object target = getTargetRepository(information);

        // Create proxy
        ProxyFactory result = new ProxyFactory();
        result.setTarget(target);
        result.setInterfaces(repositoryInterface, Repository.class, TransactionalProxy.class);

        if (MethodInvocationValidator.supports(repositoryInterface)) {
            result.addAdvice(new MethodInvocationValidator());
        }

        result.addAdvice(SurroundingTransactionDetectorMethodInterceptor.INSTANCE);
        result.addAdvisor(ExposeInvocationInterceptor.ADVISOR);

        postProcessors.forEach(processor -> processor.postProcess(result, information));

        result.addAdvice(new DefaultMethodInvokingMethodInterceptor());

        ProjectionFactory projectionFactory = getProjectionFactory(classLoader, beanFactory);
        result.addAdvice(new QueryExecutorMethodInterceptor(information, projectionFactory));

        composition = composition.append(RepositoryFragment.implemented(target));
        result.addAdvice(new ImplementationMethodExecutionInterceptor(composition));

        T repository = (T) result.getProxy(classLoader);

        if (LOG.isDebugEnabled()) {
            LOG.debug("Finished creation of repository instance for {}.", repositoryInterface.getName());
        }

        return repository;
    }

    //......
}

RepositoryFactorySupport的getRepository方法在调用子类的getTargetRepository创建SimpleJpaRepository实例之后，会对其进行proxy，设置其接口为用户定义的dao接口、Repository、TransactionalProxy，并添加了SurroundingTransactionDetectorMethodInterceptor、DefaultMethodInvokingMethodInterceptor、QueryExecutorMethodInterceptor、ImplementationMethodExecutionInterceptor等MethodInterceptor，最后生成最终的实现类

小结

JpaRepositoryImplementation接口继承了JpaRepository及JpaSpecificationExecutor，它是JpaRepository接口实现类的SPI interface；它定义了setRepositoryMethodMetadata方法
SimpleJpaRepository实现了JpaRepositoryImplementation接口，它是CrudRepository的默认实现；它的构造器都要求传入EntityManager；从各个方法的实现可以看到SimpleJpaRepository是使用EntityManager来完成具体的方法功能，对于查询功能很多都借助了applySpecificationToCriteria方法，将spring data的Specification转换为javax.persistence的CriteriaQuery
JpaRepositoryFactory的getTargetRepository会根据RepositoryInformation创建JpaRepositoryImplementation，这里默认创建的是SimpleJpaRepository实例；RepositoryFactorySupport的getRepository方法在调用子类的getTargetRepository创建SimpleJpaRepository实例之后，会对其进行proxy，设置其接口为用户定义的dao接口、Repository、TransactionalProxy，并添加了SurroundingTransactionDetectorMethodInterceptor、DefaultMethodInvokingMethodInterceptor、QueryExecutorMethodInterceptor、ImplementationMethodExecutionInterceptor等MethodInterceptor，最后生成最终的实现类