参数值[…]与预期的类型[java.util.Collection(N/A)]不匹配

Question

@ManyToMany(fetch=FetchType.LAZY)
    @JoinTable(name = "form_group",
        joinColumns = @JoinColumn( name = "form_id", referencedColumnName = "id"), 
        inverseJoinColumns = @JoinColumn(name = "group_id", referencedColumnName = "id"))
    @JsonIgnore
    private Collection<Group> groups;

@Query("SELECT new com.nsia.model.Form(f.id, f.name, f.description, f.createdAt, f.groups, COUNT(i.id)) from Form f LEFT JOIN f.instances i WHERE f.groups IN (?1) group by f.id")

java.lang.IllegalArgumentException: Parameter value [Group {id=4, name='DATA_ENTRY_GROUP', description='DATA ENTRY GROUP'}] did not match expected type [java.util.Collection (n/a)]

        Collection<Group> groups = userService.getLoggedInUser().getGroups();
        formsList = formRepository.findByGroups(groups);

Answer 1

你正在尝试的是不可能的。

构造函数表达式不能将集合作为参数，因为under laying SQL select语句的结果始终是一个表。

所以你唯一能做的就是得到一个笛卡尔积，就像这样，加入F组。

@Query("SELECT new com.nsia.model.Form(f.id, f.name, f.description, f.createdAt, g, COUNT(i.id)) from Form f LEFT JOIN f.instances JOIN f.groups g WHERE f.groups IN (?1) group by f.id")