如何使用@ConstructorResult注释

Question

我有一些本地查询，并希望将查询结果映射到非实体POJO类的列表中：

@SqlResultSetMapping(
    name = "SomeMapping",
    classes = {
        @ConstructorResult(targetClass = SomeClass.class,
            columns = {
                @ColumnResult(name = "id", type = Integer.class),
                @ColumnResult(name = "NAME", type = String.class),
                @ColumnResult(name = "DATE_BEGIN", type = java.util.Date.class)
            }
        )
    }
)

public class SomeClass{
    private Integer id;
    private String name;
    private java.util.Date begDate;
    private java.util.Date endDate;

    public SomeClass(Integer id, String name, Date begDate){
        this.id = id;
        this.name = name;
        this.begDate = begDate;
    }

    //Getters & Setters ...
}

一般我想要检索查询执行的结果：

String query = "SELECT " +
"A.id AS 'id', " +
"A.name AS 'NAME', " +
"A.begDate AS 'DATE_BEGIN' " + 
"FROM " +
"SomeTable A " +
"WHERE A.endDate < '2014-01-01'";

List<SomeClass> result = em.createNativeQuery(query, "SomeMapping").getResultList();

但我总是得到对象列表。如何检索我的 POJO 列表？

- Silence

---

那是问题的一个好解释。 - Eugene Gorelik

Answer 1

无法复现，但是你的代码存在一些问题。

• 在实体类上添加@SqlResultSetMapping
• 不要用'引用列别名

import java.util.Date;
import lombok.AllArgsConstructor;
import lombok.Data;
import lombok.NoArgsConstructor;

@NoArgsConstructor
@AllArgsConstructor
@Data
public class SomeClass {
    private int id;
    private String name;
    private Date dateBegin;
}

import java.util.Date;
import javax.persistence.Column;
import javax.persistence.ColumnResult;
import javax.persistence.ConstructorResult;
import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.SqlResultSetMapping;
import javax.persistence.Table;
import lombok.Getter;

@SqlResultSetMapping(
    name = "SomeMapping",
    classes = {
        @ConstructorResult(targetClass = SomeClass.class,
            columns = {
                @ColumnResult(name = "id", type = Integer.class),
                @ColumnResult(name = "NAME", type = String.class),
                @ColumnResult(name = "DATE_BEGIN", type = java.util.Date.class)
            })
    })
@Entity
@Table(name = "sometable")
@Getter
public class SomeEntity {

    @Id
    @Column(name = "id")
    private Integer id;

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

    @Column(name = "begdate")
    private Date begDate;

    @Column(name = "enddate")
    private Date endDate;
}

        final String query = "SELECT " +
            "A.id AS id, " +
            "A.name AS NAME, " +
            "A.begDate AS DATE_BEGIN " +
            "FROM " +
            "SomeTable A " +
            "WHERE A.endDate < '2014-01-01'";

        final List<SomeClass> result = em.createNativeQuery(query, "SomeMapping").getResultList();

- DEWA Kazuyuki - 出羽和之

Answer 2

尝试将@SqlResultSetMapping实体移至实体上。

- V G

---

这并没有回答问题。如果您想批评或请求作者澄清，请在他们的帖子下留言。 - serejja

我还没有尝试过，但我相信这就是答案。我像“尝试”一样制定它的事实与其正确性无关。附言：如果我从OP那里得到任何反应，我会相应地更改文本，你可以放心。 - V G

如果我将"@SqlResultSetMapping"注释移动到另一个带有"@Entity"注释的实体类中，我会收到空列表。但在HeidySQL中执行相同的查询会返回多行。 - Silence