Question

我编写了以下代码段，以使用zips作为JPA提供程序从hibernate表中获取某些zip文件的记录。

    public List<ZipEntity> getZipEntityFromZipName(String zipName, String version, String createdBy,
                                                      String type) throws FileException {

        int numAttempts = 0;
        do {
            numAttempts++;
            EntityManager entityManager = getNewEntityManager();
            try {
                TypedQuery<ZipEntity> query = entityManager
                        .createNamedQuery(Constants.Database.Queries.GET_FROM_ZIP_NAME, ZipEntity.class)
                        .setParameter("zipName", zipName)
                        .setParameter("version", version)
                        .setParameter("createdBy", createdBy)
                        .setParameter("type", type);
                return query.getResultList();
            } catch (PersistenceException e) {
                validatePersistenceException(e);
            } finally {
                closeEntityManager(entityManager);
            }
        } while (numAttempts <= maxRetries);
        throw new FileException("Database connection failed.");

以下是相关的实体类

@NamedNativeQueries({
        @NamedNativeQuery(
                name = Constants.Database.Queries.GET_FROM_ZIP_NAME,
                query = Constants.Database.Queries.GET_FROM_ZIP_NAME_QUERY,
                resultClass = ZipEntity.class
        )
})
@Entity
@Table(name = "zips")
public class ZipEntity {

    @EmbeddedId
    private ZipKey ZipKey;

    public ZipEntity() {

    }

    public ZipEntity(String zipName, String version, String createdBy, String file, String type,
                      String extension) {

        this.ZipKey = new ZipKey(zipName, version, createdBy, file, type, extension);
    }
}

@Embeddable
public class ZipKey implements Serializable {

    static final long serialVersionUID = 1L;

    @Column(name = "zip_name")
    private String zipName;

    @Column(name = "version")
    private String version;

    @Column(name = "created_by")
    private String createdBy;

    @Column(name = "filepath")
    private String file;

    @Column(name = "type")
    private String type;

    @Column(name = "extension")
    private String extension;

 // Getter, setters and Constructor
}

Constant类中的查询如下，

public static final String GET_FROM_ZIP_NAME = "getFile";
public static final String GET_FROM_ZIP_NAME_QUERY = "SELECT * FROM zips WHERE zip_name = " +
                    ":zipName AND version = :version AND created_by = :createdBy AND type = :type";

尽管没有为上述查询定义setMaxResults()事件，但是从DB代码执行的相同查询得到35条记录，但从上述代码段获得的结果限制为25条记录。我在这里做错了什么？

Answer 1

请调试您的解决方案，并检查“ zipName”，“版本”，“ createdBy”以及“类型”参数的值，以验证它们是否为您期望的值。此查询包含由AND逻辑组合的条件，这些条件会影响您的结果。要获得35条记录，您的参数应使所有35条记录的条件都成立。

您可以在NamedNativeQuery中限制以下记录，一次可以为您提供35条记录。

 @NamedNativeQuery(
                name = Constants.Database.Queries.GET_FROM_ZIP_NAME,
                query = Constants.Database.Queries.GET_FROM_ZIP_NAME_QUERY,
                fetchSize = 35,
                resultClass = ZipEntity.class
        )

即使未定义setMaxResults，JPA也会限制queryResultList

1 个答案: