从 Java 类动态创建 spring EnversRevisionRepository

Question

如何在给定 Java Class 对象的情况下动态创建EnversRevisionRepository？

感谢https://stackoverflow.com/a/22342025/3771679 这个答案，人们可​​以成功地动态创建JpaRepository，但我想为相当于以下内容的存储库实现相同的目标：

public interface MyRevisionedRepository extends RevisionRepository<X,Y,Z>, JpaRepository<X,Y> {

}

Answer 1

Spring Data 提供EnversRevisionRepositoryImpl 作为默认的RevisionRepository 实现。

正如您在存储库构造函数中看到的：

    /**
     * Creates a new {@link EnversRevisionRepositoryImpl} using the given {@link JpaEntityInformation},
     * {@link RevisionEntityInformation} and {@link EntityManager}.
     *
     * @param entityInformation must not be {@literal null}.
     * @param revisionEntityInformation must not be {@literal null}.
     * @param entityManager must not be {@literal null}.
     */
    public EnversRevisionRepositoryImpl(JpaEntityInformation<T, ?> entityInformation,
            RevisionEntityInformation revisionEntityInformation, EntityManager entityManager) {

        Assert.notNull(revisionEntityInformation, "RevisionEntityInformation must not be null!");

        this.entityInformation = entityInformation;
        this.entityManager = entityManager;
    }

您需要三件事来创建该存储库的新实例：

• 一个EntityManager，您可以使用@PersistenceContext 或可能（我从未测试过）通过@Autowiring 轻松获得。

• JpaEntityInformation。以SimpleJpaRepository为例：

final JpaEntityInformation<T, ?> entityInformation =
  JpaEntityInformationSupport.getEntityInformation(domainClass, em)

• RevisionEntityInformation。这很奇怪，因为该对象被断言为不为空，但实际上它在其余的实现代码中似乎未使用。这里，我们可以借鉴EnversRevisionRepositoryFactoryBean的例子：

final RevisionEntityInformation revisionEntityInformation =
  Optional.ofNullable(revisionEntityClass) //
    .filter(it -> !it.equals(DefaultRevisionEntity.class))//
    .<RevisionEntityInformation> map(ReflectionRevisionEntityInformation::new) //
    .orElseGet(DefaultRevisionEntityInformation::new); 

DefaultRevisionEntityInformation 是包作用域的，但您可以轻松地复制它：

import org.hibernate.envers.DefaultRevisionEntity;
import org.springframework.data.repository.history.support.RevisionEntityInformation;

/**
 * {@link RevisionEntityInformation} for {@link DefaultRevisionEntity}.
 */
public class DefaultRevisionEntityInformation implements RevisionEntityInformation {

    /*
     * (non-Javadoc)
     * @see org.springframework.data.repository.history.support.RevisionEntityInformation#getRevisionNumberType()
     */
    public Class<?> getRevisionNumberType() {
        return Integer.class;
    }

    /*
     * (non-Javadoc)
     * @see org.springframework.data.repository.history.support.RevisionEntityInformation#isDefaultRevisionEntity()
     */
    public boolean isDefaultRevisionEntity() {
        return true;
    }

    /*
     * (non-Javadoc)
     * @see org.springframework.data.repository.history.support.RevisionEntityInformation#getRevisionEntityClass()
     */
    public Class<?> getRevisionEntityClass() {
        return DefaultRevisionEntity.class;
    }
}

总结：

// Obtain a reference to the underlying EntityManager
final EntityManager entityManager = ...;
// Provide JpaEntityInformation
final JpaEntityInformation<User, ?> entityInformation =
  JpaEntityInformationSupport.getEntityInformation(User.class, entityManager);
// Provide RevisionEntityInformation. The solution is based on 
// DefaultRevisionEntity but you can provide your custom revision entity
// if appropriate
final RevisionEntityInformation revisionEntityInformation =
  new DefaultRevisionEntityInformation();
// Build your custom revision repository, for example:
final RevisionRepository userRevisionRepository =
  new EnversRevisionRepositoryImpl<User, Integer, DefaultRevisionEntity>(
    entityInformation, revisionEntityInformation, entityManager
  )
;