Question

我使用hibernate one-to-one映射来构建Stock和Category之间的关系。当我的网络应用程序开始使用以下Category语句时，会导入sql表的数据。

insert into Category (name, created_time) values ('top', now()), ('recommend', now()), ('editor choice', now()), ('random', now());

首先，我可以通过执行CategoryDAOImpl.getCategories获取类别列表，但在执行CategoryDAOImpl.getCategorybyName(String name)之后，方法CategoryDAOImpl.getCategories无法正常工作，输出消息显示hibernate sql执行不返回。

我实施one-to-one映射时是否存在错误？

我该如何解决这个问题？

Stock.java

@Entity
public class Stock {

    @Id
    @GeneratedValue
    @Column(name = "id")
    private long id;

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

    @OneToOne
    private Category category;

    @Column(name = "created_time")
    private Date date;

    /**
     * @return the id
     */
    public long getId() {
       return id;
    }

    /**
     * @param id the id to set
     */
    public void setId(long id) {
        this.id = id;
    }

    /**
     * @return the name
     */
    public String getName() {
        return name;
    }

    /**
     * @param name the name to set
     */
    public void setName(String name) {
        this.name = name;
    }

    /**
     * @return the category
     */
    public Category getCategory() {
        return category;
    }

    /**
     * @param category the category to set
     */
    public void setCategory(Category category) {
        this.category = category;
    }

    /**
     * @return the date
     */
    public Date getDate() {
        return date;
    }

    /**
     * @param date the date to set
     */
    public void setDate(Date date) {
        this.date = date;
    }

}

Category.java

@Entity
public class Category {

@Id
@GeneratedValue
@Column(name = "id")
private long id;

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

@Temporal(TemporalType.TIMESTAMP)
@Column(name = "created_time")
private Date date;

@OneToOne(mappedBy = "category")
private Stock stock;

/**
 * @return the id
 */
public long getId() {
    return id;
}

/**
 * @param id the id to set
 */
public void setId(long id) {
    this.id = id;
}

/**
 * @return the name
 */
public String getName() {
    return name;
}

/**
 * @param name the name to set
 */
public void setName(String name) {
    this.name = name;
}

/**
 * @return the date
 */
public Date getDate() {
    return date;
}

/**
 * @param date the date to set
 */
public void setDate(Date date) {
    this.date = date;
}

/**
 * @return the stock
 */
public Stock getStock() {
    return stock;
}

/**
 * @param stock the stock to set
 */
public void setStock(Stock stock) {
    this.stock = stock;
}

}

CategoryDAOImpl.java

@Repository
@Transactional
public class CategoryDAOImpl implements CategoryDAO {

@Autowired
private SessionFactory sessionFactory;

/*
 * (non-Javadoc)
 * 
 * @see com.example.mywebapp.dao.CategoryDAO#getCategories()
 */
@Override
public List<Category> getCategories() {
    // TODO Auto-generated method stub
    return sessionFactory.getCurrentSession()
            .createCriteria(Category.class).list();
}

/*
 * (non-Javadoc)
 * 
 * @see
 * com.example.mywebapp.dao.CategoryDAO#getCategorybyName(java.lang.String)
 */
@Override
public Category getCategorybyName(String name) {
    // TODO Auto-generated method stub
    List<Category> categories = sessionFactory.getCurrentSession()
            .createCriteria(Category.class)
            .add(Restrictions.eq("name", name)).list();
    if (categories != null && categories.size() > 0) {
        return categories.get(0);
    }
    return null;
}

/**
 * @return the sessionFactory
 */
public SessionFactory getSessionFactory() {
    return sessionFactory;
}

/**
 * @param sessionFactory
 *            the sessionFactory to set
 */
public void setSessionFactory(SessionFactory sessionFactory) {
    this.sessionFactory = sessionFactory;
}

}

Answer 1

从hibernate的调试输出中，我找出了导致问题的原因。当来自Category的查询时，hibernate将使用Stock加入表，因为它们之间存在one-to-one映射关系，因此结果不正确。通过在Category查询上设置投影和相应的结果转换器，它可以正常工作。

@Override
public List<Category> getCategories() {
    // TODO Auto-generated method stub
    ProjectionList projectionList = Projections.projectionList();
    projectionList.add(Projections.property("id"), "id");
    projectionList.add(Projections.property("name"), "name");
    projectionList.add(Projections.property("date"), "date");
    return sessionFactory.getCurrentSession()
            .createCriteria(Category.class).setProjection(projectionList)
            .setResultTransformer(Transformers.aliasToBean(Category.class))
            .list();
}

插入数据后暂停一对一查询错误

1 个答案: