使用 Criteria API (JPA 2.0) 创建查询

Question

我正在尝试使用 JPA 2.0 中的 Criteria API 创建查询，但无法使其工作。

问题出在“ Between ”条件方法上。我阅读了一些文档来了解我必须如何做到这一点，但自从我发现 JPA 以来，我不明白为什么它不起作用。

首先，我看不到当我写“Transaction_”时应该出现的“creationDate”。

我认为这可能是正常的，因为我读到元模型是在运行时生成的，所以我尝试使用 'Foo_.getDeclaredSingularAttribute("value")' 而不是 'Foo_.value'，但它仍然根本不起作用。

这是我的代码：

public List<Transaction> getTransactions(Date startDate, Date endDate) {
    EntityManager em = getEntityManager();
    try {
        CriteriaBuilder cb = em.getCriteriaBuilder();
        CriteriaQuery<Transaction> cq = cb.createQuery(Transaction.class);
        Metamodel m = em.getMetamodel();
        EntityType<Transaction> Transaction_ = m.entity(Transaction.class);
        Root<Transaction> transaction = cq.from(Transaction.class);

        // Error here. cannot find symbol. symbol: variable creationDate
        cq.where(cb.between(transaction.get(Transaction_.creationDate), startDate, endDate));

        // I also tried this:
        // cq.where(cb.between(Transaction_.getDeclaredSingularAttribute("creationDate"), startDate, endDate));

        List<Transaction> result = em.createQuery(cq).getResultList();
        return result;
    } finally {
        em.close();
    }
}

有人可以帮我解决这个问题吗？谢谢。

编辑：这是事务源（其中几乎没有任何内容，因为它是由 Netbeans 从我的数据库自动生成的）

package projetjava.db;

import java.io.Serializable;
import java.util.Date;
import javax.persistence.Basic;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.NamedQueries;
import javax.persistence.NamedQuery;
import javax.persistence.Table;
import javax.persistence.Temporal;
import javax.persistence.TemporalType;

@Entity
@Table(name = "transaction")
@NamedQueries({
    @NamedQuery(name = "Transaction.findAll", query = "SELECT t FROM Transaction t"),
    @NamedQuery(name = "Transaction.findById", query = "SELECT t FROM Transaction t WHERE t.id = :id"),
    @NamedQuery(name = "Transaction.findByIDAccount", query = "SELECT t FROM Transaction t WHERE t.iDAccount = :iDAccount"),
    @NamedQuery(name = "Transaction.findByDescription", query = "SELECT t FROM Transaction t WHERE t.description = :description"),
    @NamedQuery(name = "Transaction.findByCreationDate", query = "SELECT t FROM Transaction t WHERE t.creationDate = :creationDate"),
    @NamedQuery(name = "Transaction.findByAmount", query = "SELECT t FROM Transaction t WHERE t.amount = :amount")})
public class Transaction implements Serializable {
    private static final long serialVersionUID = 1L;
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Basic(optional = false)
    @Column(name = "ID")
    private Integer id;
    @Basic(optional = false)
    @Column(name = "IDAccount")
    private int iDAccount;
    @Basic(optional = false)
    @Column(name = "Description")
    private String description;
    @Basic(optional = false)
    @Column(name = "CreationDate")
    @Temporal(TemporalType.DATE)
    private Date creationDate;
    @Basic(optional = false)
    @Column(name = "Amount")
    private double amount;

    public Transaction() {
    }

    public Transaction(Integer id) {
        this.id = id;
    }

    public Transaction(Integer id, int iDAccount, String description, Date creationDate, double amount) {
        this.id = id;
        this.iDAccount = iDAccount;
        this.description = description;
        this.creationDate = creationDate;
        this.amount = amount;
    }

    public Integer getId() {
        return id;
    }

    public void setId(Integer id) {
        this.id = id;
    }

    public int getIDAccount() {
        return iDAccount;
    }

    public void setIDAccount(int iDAccount) {
        this.iDAccount = iDAccount;
    }

    public String getDescription() {
        return description;
    }

    public void setDescription(String description) {
        this.description = description;
    }

    public Date getCreationDate() {
        return creationDate;
    }

    public void setCreationDate(Date creationDate) {
        this.creationDate = creationDate;
    }

    public double getAmount() {
        return amount;
    }

    public void setAmount(double amount) {
        this.amount = amount;
    }

    @Override
    public int hashCode() {
        int hash = 0;
        hash += (id != null ? id.hashCode() : 0);
        return hash;
    }

    @Override
    public boolean equals(Object object) {
        // TODO: Warning - this method won't work in the case the id fields are not set
        if (!(object instanceof Transaction)) {
            return false;
        }
        Transaction other = (Transaction) object;
        if ((this.id == null && other.id != null) || (this.id != null && !this.id.equals(other.id))) {
            return false;
        }
        return true;
    }

    @Override
    public String toString() {
        return "projetjava.db.Transaction[id=" + id + "]";
    }

}

Answer 1

我认为这可能是正常的，因为我读到元模型是在运行时生成的（...）

元模型类是在编译时使用注释处理生成的。换句话说，您需要在编译器级别激活注释处理。 Hibernate JPA 2 元模型生成器 文档介绍了如何使用 Ant、Maven 和 Eclipse 或 Idea 等 IDE 来实现这一点（该方法可以移植到其他提供商）。遗憾的是，NetBeans 目前不支持此功能。

因此，要么使用并配置上述构建工具之一，要么切换到另一个 IDE。例如，使用 Eclipse，右键单击项目并转到 Java Compiler >注释处理并启用它：

然后将您的提供商所需的 JAR（请参阅您的 JPA 提供商的文档了解此步骤）添加到工厂路径。

Answer 2

我认为这里令人困惑的部分是
q.where(cb. Between(transaction.get(Transaction_.creationDate), startDate, endDate));

您必须注意，在这种情况下 Transaction_ 是静态实例化的，对应于原始Transaction实体类的规范元模型类。您必须通过使用 JPA 库编译 Transaction 类来生成 Transaction_ 类。
Eclipse 的一个有用链接在这里：
http://wiki.eclipse.org/UserGuide/JPA/Using_the_Canonical_Model_Generator_%28ELUG% 29

对于intellij IDEA

http://blogs.jetbrains.com/idea/2009/11/userfriend-annotation-processing-support-jpa-20-metamodel/

Answer 3

在 JPA 中查询开始日期和结束日期

public List<Student> findStudentByReports(String className, Date startDate, Date endDate) {
    System.out
    .println("call findStudentMethd******************with this pattern"
            + className
            + startDate
            + endDate
            + "*********************************************");

    return em
    .createQuery(
            "select attendence from Attendence attendence where lower(attendence.className) like '"
            + className + "' or attendence.admissionDate BETWEEN : startdate AND endDate " + "'")
            .setParameter("startDate", startDate, TemporalType.DATE)
            .setParameter("endDate", endDate, TemporalType.DATE)
            .getResultList();
}