java - 条件查询返回[]

Question

当某些类字段可能为空时，我尝试使用条件存储库按类字段查找数据库记录。我正在检查字符串、整数，并且使用 SQL 中的“like”来检查二进制字中的位。

我的实体类和元模型都在单独的包中:

-metapackage
    |
    +-MyEntity1.java
    |
    +-MyEntity1_.java

这是我的元模型:

    public static volatile SingularAttribute< MyEntity1, String> country;
    public static volatile SingularAttribute< MyEntity1, String> city;
    public static volatile SingularAttribute< MyEntity1, LocalDate> added;
    public static volatile SingularAttribute< MyEntity1, String> address;
    public static volatile SingularAttribute< MyEntity1, UserJPA> userJpa;
    public static volatile SingularAttribute< MyEntity1, String> title;
    public static volatile SingularAttribute< MyEntity1, Integer> size;
    public static volatile SingularAttribute< MyEntity1, String> sizeUnit;
    public static volatile SingularAttribute< MyEntity1, String> flags;// <<<<<<< this is a binary word of 8 bits
    public static volatile SingularAttribute< MyEntity1, Long> id;

这是我的标准代码:

    CriteriaBuilder builder = entityManagerFactory.getCriteriaBuilder();
    
    CriteriaQuery< MyEntity1> cquery = builder.createQuery( MyEntity1.class);
    Root< MyEntity1> croot = cquery.from( MyEntity1.class);
    
    cquery.select(croot);
    Predicate pred = builder.isNotNull(croot.<String>get( MyEntity1_.flags));
    
    if(RestPreconditions.checkString(model.getCity())) {
        pred = builder.and(pred, builder.equal(croot.get( MyEntity1_.city), model.getCity()));
    }
    if(RestPreconditions.checkString(model.getCountry())) {
        pred = builder.and(pred, builder.equal(croot.get( MyEntity1_.country), model.getCountry()));
    }
    if(RestPreconditions.checkString(model.getAddress())) {
        pred = builder.and(pred, builder.equal(croot.get( MyEntity1_.address), model.getAddress()));
    }
    
    if(model.getMaxSize()!=null) {
        pred = builder.and(pred, builder.lessThanOrEqualTo(croot.get( MyEntity1_.size), model.convertSizeToM2(model.getMaxSize())));
    }
    if(model.getMinSize()!=null) {
        pred = builder.and(pred, builder.greaterThanOrEqualTo(croot.get( MyEntity1_.size), model.convertSizeToM2(model.getMinSize())));
    }
    // .flagsToBword() always returns something
    String bword = model.flagsToBWord();
    if(!bword.matches("0{8}")){
        pred = builder.and(pred, builder.like(croot.<String>get( MyEntity1_.flags), bword.replaceAll("0", "_")));
    }
    
    return entityManagerFactory.createEntityManager()
            .createQuery(cquery.where(pred))
            .getResultList();
        

问题是我不断收到空列表作为响应，即使我知道数据库中有匹配的对象。

我做错了什么？

编辑:

例如，如果我想查找名为伦敦的城市的记录，这就是我发送的对象:

{
    "city":"London"
}

我有一个与该城市连续的数据库记录。

此外，当我构造谓词时，开头的这行代码:

谓词 pred = builder.isNotNull(croot.get( MyEntity1_.flags));

是否只是为了启动合相；标志永远不会为空

Answer 1

您走在正确的道路上。您犯的唯一错误是您每次都覆盖 pred 的值。

If you want to chain where statements, you have to reassign pred value with itself + where clause.

Specification<MyEntity1> spec = Specification.where(
    (root, cb, cq) -> cb.isNotNull(root.get(MyEntity1_.flags)));

if (RestPreconditions.checkString(model.getCity())) 
    spec = spec.and(
        (root, cb, cq) -> cb.equal(root.get(MyEntity1_.city), model.getCity()))

return yourRepository.findAll(spec);