我有这个实体

@Entity
@Table(name = "DOCUMENT")
public class Document {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "ID",nullable = false)
    private Long id;

    @Column(name = "NAME",nullable = false)
    private String name;

    @Column(name = "BROKER_ID",nullable = true)
    private String brokerId;

    @ManyToOne
    @JoinColumn(name = "TYPE_ID",nullable = false)
    private DocumentType type;

    @Column(name = "UPLOAD_DATE",nullable = false)
    private Date uploadDate;

    @Column(name = "LANGUAGE",nullable = false)
    @Enumerated(EnumType.STRING)
    private Language language;

    @ElementCollection
    @CollectionTable(name = "DOCUMENT_VIEWED_BY",joinColumns = @JoinColumn(name = "DOCUMENT_ID",referencedColumnName = "ID"))
    @Column(name = "VIEWED_BY",nullable = false)
    private Set<String> viewedBy;

    @Column(name = "DOCUMENT_REFERENCE",nullable = false)
    private String documentReference;

//constructors getters setters

然后我试图通过 brokerId、类型和分页从数据库中获取所有文档。一切正常，唯一的问题是我想获取一个带有这样的 case 表达式的额外列

final BooleanExpression b = new CaseBuilder()
      .when(document.viewedBy.contains(brokerId)).then(true).otherwise(false);

final JPAQuery<DocumentProjection> query = new JPAQuery<>(this.em);
      query.select(Projections.constructor(DocumentProjection.class,document.brokerId,document.documentReference,document.name,document.uploadDate,document.type.id,document.language,b));

获取此查询

Hibernate: 
    select
        document0_.BROKER_ID as col_0_0_,document0_.DOCUMENT_REFERENCE as col_1_0_,document0_.NAME as col_2_0_,document0_.UPLOAD_DATE as col_3_0_,document0_.TYPE_ID as col_4_0_,document0_.LANGUAGE as col_5_0_,case 
            when ? in (viewedby1_.VIEWED_BY) then ? 
            else 0 
        end as col_6_0_ 
    from
        DOCUMENT document0_ cross 
    join
        DOCUMENT_VIEWED_BY viewedby1_ 
    where
        document0_.ID=viewedby1_.DOCUMENT_ID 
        and (
            document0_.BROKER_ID=? 
            or document0_.BROKER_ID is null
        ) 
        and (
            document0_.TYPE_ID in (
                ?,?,?
            )
        ) 
    order by
        document0_.UPLOAD_DATE desc limit ?

这很好，唯一的问题是在 case 子句中......我想要类似 when viewedby1_.VIEWED_BY = ? then 而不是 when ? in (viewedby1_.VIEWED_BY) then 的东西，所以我试图从 {{1} 更改行} 到 document.viewedBy.contains(brokerId) 因为这是我在代码其他部分的 document.viewedBy.any().eq(brokerId) 子句中这样做的方式，它为我提供了我想要的语法，但是当谈到 where 在 {{ 1}} 它给了我一个错误

case

谢谢。