Question

我正在做以下事情：

@Entity
@SqlResultSetMapping(name="getxxxx",
        entities=@EntityResult(xxxx.class,
            fields = {
                    @FieldResult(name="x1", column = "x1"),
                    @FieldResult(name="x2", column = "x2")}))

@NamedNativeQuery(name=" getxxxx ",
    query="select x1, x2 from yyyy", 
    resultSetMapping=" getxxxx ")

} )public class xxxx{

    .
    .
    .
    public xxxx() {

}

我收到一个错误： “表”xxxx“无法解析”，类xxxx不是映射到我的源的表，我正在尝试查询数据库并将结果返回到我的班级有可能吗？

Answer 1

在这种情况下，我要尝试的第一件事就是删除@Entity注释。然后更改类名或本机查询名，以便其中一个是“xxxx”，其中一个是“zzzz”，这样我就确定我知道运行时抱怨的是什么。

Answer 2

听起来 xxxx 不应该是实体bean，因为JPA不满意在非实体bean中返回结果。您只需使用SQL字符串调用 createNativeQuery 。然后调用 query.getResultList（）以 List（Object []）的形式获取结果，并使用它来填充非实体结果bean。

几年前我写了blog post，这可能会帮助您使用JPA执行高级本机查询。

Answer 3

是的，这是可能的，但有点棘手。这是一个复杂的例子，应涵盖大部分基础。在这个例子中：

您有一个具有截止日期的INVOICE对象;
每个INVOICE都与公司有多对一的关系;
每个INVOICE与一组ITEMS之间也有零或一对多的关系

这是架构：

CREATE TABLE "public"."invoice" (
  id SERIAL, 
  company_id int, 
  due_date date, 
  PRIMARY KEY(id)
);
CREATE TABLE "public"."item" (
  id SERIAL, 
  invoice_id int,
  description text,
  PRIMARY KEY(id)
);
CREATE TABLE "public"."company" (
  id SERIAL,
  name text,
  PRIMARY KEY(id)
);

INVOICE对象（为了完整性而令人费解的例子）：

@Entity
@Table(name = "invoice")
@Loader(namedQuery = "loadInvoiceObject")
@NamedNativeQuery(name="loadInvoiceObject",
  query="SELECT " +
        "inv.id," +
        "inv.due_date," +
        "co.*," +
        "it.*," +
        "FROM invoice inv " +
        "JOIN company co ON co.id = inv.company_id " +
        "LEFT OUTER JOIN item it ON it.invoice_id = inv.id " +
        "WHERE inv.id = :id",
  resultSetMapping = "invoicemap")
@SqlResultSetMapping(name = "invoicemap",
  entities = {
    @EntityResult(entityClass = Invoice.class),
    @EntityResult(entityClass = Company.class),
    @EntityResult(entityClass = Item.class)
  }
)
public class Invoice {

  private Integer id;
  private Date dueDate;
  private Company company;
  private List<Item> items = new ArrayList<Item>();

  public Invoice() { /* no-args constructor */ }

  @Id
  @Column(name = "id", nullable = false)
  public Integer getId() { return id; }
  public void setId(Integer id) { this.id = id; }

  @Column(name = "due_date")
  @Temporal(TemporalType.DATE)
  public Date getDueDate() { return dueDate; }
  public void setDueDate(Date dueDate) { this.dueDate = dueDate; }

  @ManyToOne(optional = false)
  @JoinColumn(name = "company_id", nullable = false)
  public Company getCompany() { return company; }
  public void setCompany(Company company) { this.company = company; }

  @OneToMany(mappedBy = "invoice")
  public List<Item> getItems() { return items; }
  public void setItems(List<Item> items) { this.items = items; }

}

ITEM对象：

@Entity
@Table(name = "item")
public class Item {

  private Integer id;
  private String description;
  private Invoice invoice;

  public Item() { /* no-args constructor */ }

  @Id
  @Column(name = "id", nullable = false)
  public Integer getId() { return id; }
  public void setId(Integer id) { this.id = id; }

  @Column(name = "description")
  public String getDescription() { return description; }
  public void setDescription(String description) { this.description = description; }

  @ManyToOne(optional = false)
  @JoinColumn(name = "invoice_id", nullable = false)
  public Invoice getInvoice() { return invoice; }
  public void setInvoice(Invoice invoice) { this.invoice = invoice; }

}

COMPANY对象：

@Entity
@Table(name = "company")
public class Company {

  private Integer id;
  private String name;
  private List<Invoice> invoices = new ArrayList<Invoice>();

  public Company() { /* no-args constructor */ }

  @Id
  @Column(name = "id", nullable = false)
  public Integer getId() { return id; }
  public void setId(Integer id) { this.id = id; }

  @Column(name = "name")
  public String getName() { return name; }
  public void setName(String name) { this.name = name; }

  @OneToMany(mappedBy = "company")
  public List<Invoice> getInvoices() { return invoices; }
  public void setInvoices(List<Invoice> invoices) { this.invoices = invoices; }

}

尝试运行命名查询

3 个答案: