HIbernate：選擇多個不同的列會導致錯誤

Question

我正在嘗試執行查詢

Hibernate: select distinct this_.platform as y0_, this_.device as y1_, this_.date as y2_ from my_lab this_ where this_.brand=? and this_.network=?

使用代碼：

    Criteria crit = entityManager.unwrap(Session.class).createCriteria(Lab.class);

    ProjectionList projList = Projections.projectionList();

    if (platform == null) {
        projList.add(Projections.property("platform"));
    } else {

        crit.add(Restrictions.eq("platform", platform));
    }

    if (device == null) {
        projList.add(Projections.property("device"));
    } else {

        crit.add(Restrictions.eq("device", device));
    }

    if (date == null) {
        projList.add(Projections.property("date"));
    } else {
        crit.add(Restrictions.eq("date", dateOfVideo));
    }

    if (brand == null) {
        projList.add(Projections.property("brand"));
    } else {
        crit.add(Restrictions.eq("brand", brand));
    }


    if (network == null) {
        projList.add(Projections.property("network"));
    } else {
        crit.add(Restrictions.eq("network", network));
    }

    crit.setProjection(Projections.distinct(projList));

    List<String> list = crit.list();
    return list;

但是當我調用此服務時，它給了我以下錯誤：

 "Could not write content: [Ljava.lang.Object; cannot be cast to java.lang.String; nested exception is com.fasterxml.jackson.databind.JsonMappingException: [Ljava.lang.Object; cannot be cast to java.lang.String",

無法理解原因。 在get請求中也提到了produces={MediaType.APPLICATION_JSON_VALUE} 。

Answer 1

我認為問題是線

List<String> list = crit.list();

實際上，對於多個投影，您應該期望List<Object>並訪問像這樣的值

List<Object> rows = crit.list();
for(Object r: rows){
  Object[] row = (Object[]) r;
}