Java 类org.hibernate.jpa.criteria.CriteriaBuilderImpl 实例源码

/**
 * 使用动态更新的方法更新数据库简单映射字段的内容
 * @param entity
 * @param updateFieldsName
 * @return
 */
public T updateSimpleField(T entity , Collection<String> updateFieldsName){
    Assert.notEmpty(updateFieldsName , entity.getClass()+"更新字段不能为空。");

    Assert.isTrue(!entityInformation.hasCompositeId() , "不支持组合ID更新。");
    CriteriaUpdate<T> criteriaUpdate = new CriteriaUpdateImpl<T>(
            (CriteriaBuilderImpl) entityManager.getCriteriaBuilder()) ;
    //更新的实体对象
    Root<T> root = criteriaUpdate.from(getDomainClass()) ;
    for (String fieldName : updateFieldsName) {
        try {
            //通过反射读取属性的值
            PropertyDescriptor propertyDescriptor = new PropertyDescriptor(fieldName, entity.getClass()) ;
            criteriaUpdate.set(fieldName, propertyDescriptor.getReadMethod().invoke(entity,null)) ;
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
    //构造更新过滤条件
    String idField = entityInformation.getIdAttributeNames().iterator().next() ;
    Predicate predicate = entityManager.getCriteriaBuilder().equal(
            root.get(idField) , entityInformation.getId(entity)) ;
    criteriaUpdate.where(predicate) ;
    //执行更新
    entityManager.createQuery(criteriaUpdate).executeUpdate() ;

    return entity ;
}

@Before
public void setup() {
    cb = spy(new CriteriaBuilderImpl(null));
}

/**
 * 查询单个字段
 * @param field 字段名称
 * @param spec 查询条件
    * @return
    */
public List<String> querySingleFields(String field , Specification<T> spec){
    if(StringUtils.isBlank(field)){
        return null ;
    }

    CriteriaBuilder criteriaBuilder = entityManager.getCriteriaBuilder() ;

    CriteriaQuery<Object[]> query = criteriaBuilder.createQuery(Object[].class) ;

    Root<T> root = applySpecificationToCriteria(spec , query) ;

    //创建对字段的选择
    List<Selection<?>> selectionItems = new ArrayList<>(1) ;
    selectionItems.add(root.get(field)) ;

    CompoundSelection<Object[]> compoundSelection = null ;

    if(criteriaBuilder instanceof CriteriaBuilderImpl){
        compoundSelection = ((CriteriaBuilderImpl)criteriaBuilder).array(selectionItems) ;
    }

    query.select(compoundSelection) ;

    TypedQuery<Object[]> typedQuery = entityManager.createQuery(query) ;

    applySecondLevelCache(typedQuery , spec) ;

    List<Object[]> list = typedQuery.getResultList() ;

    //转换查询结果
    List<String> resultList = null ;

    if(list!=null && list.size()>0){
        resultList = new ArrayList<>(list.size()) ;
        //构造查询结果
        for (Object object : list) {
            if(object!=null){
                resultList.add(object.toString()) ;
            }
        }
    }


    return resultList ;
}