如何使用 JPA 和 Hibernate 通过自定义对象实体属性进行查询

Posted 2023-04-12

【中文标题】如何使用 JPA 和 Hibernate 通过自定义对象实体属性进行查询

【英文标题】：How to query by custom object entity property with JPA and Hibernate

【发布时间】：2014-12-04 00:29:09

【问题描述】：

编写一个 DAO 方法以通过电子邮件检索 appUsers，其中电子邮件属于 EmailAddress 类。一直在寻找如何做到这一点无济于事。有没有办法根据自定义对象的值来检索记录？当我有一个 String 或 int 类型的属性时，这似乎有效，但是如何获取与我的 EmailAddress 对象匹配的记录？

尝试了以下方法但不起作用：

public List<AppUser> findByEmail(EmailAddress email) 
    log.debug("finding " + getTable() + " instance by example");

    AppUser appUser = new AppUser();
    appUser.setEmail(email);

    try 
        List<AppUser> results = this.sessionFactory.getCurrentSession()
                .createCriteria(AppUser.class)
                .add(Example.create(appUser)).list();
        log.debug("find by example successful, result size: "
                + results.size());
        return results;
     catch (RuntimeException re) 
        log.error("find by example failed", re);
        throw re;
    

这是我的 AppUser 类的相关部分

@Entity
@Table(name="AppUser")
public class AppUser extends BaseEntity 
    ...

    @Column(name="Email")
    private EmailAddress email;

    ...

    /**
     * Gets this AppUser's associated email
     * 
     * @return this AppUser's associated email
     */
    public EmailAddress getEmail() 
        return this.email;
    

    /**
     * Sets this AppUser's associated email
     * 
     * @param email this AppUser's associated email
     */
    public void setEmail(EmailAddress email) 
        this.email = email;
       

这是我的 EmailAddress 类

  public class EmailAddress implements Serializable 
    private static final long serialVersionUID = -6999956021169014445L;
    private static final String AT_DELIMTER = "@";
    private String emailAddress;

    public EmailAddress() 

    public EmailAddress(String emailAddress) 
        setEmailAddress(emailAddress);
    

    public String getEmailAddress() 
        return emailAddress;
    

    public void setEmailAddress(String emailAddress) throws IllegalArgumentException 
        if (StringUtils.isEmpty(emailAddress))
            throw new IllegalArgumentException("Parameter emailAddress cannot be blank.");
        else if (!EmailValidator.getInstance(true).isValid(emailAddress))
            throw new IllegalArgumentException("The email address " +  emailAddress + " is not valid.");

        this.emailAddress = emailAddress;
    

    public String getUser() 
        return this.emailAddress.substring(0, this.emailAddress.indexOf(AT_DELIMTER));
    

    public String getDomain() 
        return this.emailAddress.substring(this.emailAddress.indexOf(AT_DELIMTER) + 1);
    

    public String toString() 
        return emailAddress;
    

    @Override
    public int hashCode() 
        final int prime = 31;
        int result = 1;
        result = prime * result
                + ((emailAddress == null) ? 0 : emailAddress.hashCode());
        return result;
    

    @Override
    public boolean equals(Object obj) 
        if (this == obj)
            return true;
        if (obj == null)
            return false;
        if (getClass() != obj.getClass())
            return false;
        EmailAddress other = (EmailAddress) obj;
        if (emailAddress == null) 
            if (other.emailAddress != null)
                return false;
         else if (!emailAddress.equals(other.emailAddress))
            return false;
        return true;
    

谢谢！

【参考方案1】：

将您的查询更改为：

List results = this.sessionFactory.getCurrentSession()
    .createQuery("select au from AppUser au where au.email = :email")
    .setParameter("email", email)
    .list();

您需要实现 Hibernate custom UserType 以在加载时将 DB 字符串转换为 EmailAddress。

使用来自hibernate-types 项目的ImmutableType 作为自定义Hibernate Type 的基类，因为这样更容易实现。

【讨论】：

hmm...这里一定有其他事情发生，因为这仍然没有返回任何结果。这真的很奇怪，因为当我将属性字段作为字符串时，它可以工作，但是一旦我将其更改为 EmailAddress，它就不会返回任何结果。假设 Hibernate 可以进行这种翻译，我错了吗？

【参考方案2】：

将相关更改发布到 EmailAddress 类，以防其他人想看到它们：

public class EmailAddress implements UserType 
    ...
    @Override
    public int[] sqlTypes() 
        return new int[] Types.NVARCHAR;
    

    @Override
    public Class<EmailAddress> returnedClass() 
        return EmailAddress.class;
    

    @Override
    public boolean equals(Object x, Object y) throws HibernateException 
        if (x == y)
            return true;
        if (y == null)
            return false;
        if (getClass() != y.getClass())
            return false;
        EmailAddress emailAddressX = (EmailAddress) x;
        EmailAddress emailAddressY = (EmailAddress) y;
        if (emailAddressX.getEmailAddress() == null) 
            if (emailAddressY.getEmailAddress() != null)
                return false;
         else if (!emailAddressX.getEmailAddress().equals(emailAddressY.getEmailAddress()))
            return false;
        return true;
    

    @Override
    public int hashCode(Object x) throws HibernateException 
        final int prime = 31;
        int result = 1;
        EmailAddress emailAddress = (EmailAddress) x;

        result = prime * result
                + ((emailAddress == null) ? 0 : emailAddress.hashCode());
        return result;
    

    @Override
    public Object nullSafeGet(ResultSet rs, String[] names,
            SessionImplementor session, Object owner)
            throws HibernateException, SQLException 
        EmailAddress emailAddress = null;

        String value = rs.getString(names[0]);
        if (!rs.wasNull()) 
            emailAddress = new EmailAddress(value);
        

        return emailAddress;
    

    @Override
    public void nullSafeSet(PreparedStatement st, Object value, int index,
            SessionImplementor session) throws HibernateException, SQLException 
        EmailAddress emailAddress = (EmailAddress) value;
        st.setString(index, emailAddress.getEmailAddress());
    

    @Override
    public Object deepCopy(Object value) throws HibernateException 
        return value;
    

    @Override
    public boolean isMutable() 
        return false;
    

    @Override
    public Serializable disassemble(Object value) throws HibernateException 
        return (Serializable) deepCopy(value);
    

    @Override
    public Object assemble(Serializable cached, Object owner)
            throws HibernateException 
        return deepCopy(cached);
    

    @Override
    public Object replace(Object original, Object target, Object owner)
            throws HibernateException 
        return deepCopy(original);