java - Hibernate Criteria API 和字段选择器？

Question

在 Hibernate 中，我喜欢 Criteria API，但它似乎不允许您为特定实体类指定某些列。例如，给定下表：

log_entries
    id : PRIMARY KEY AUTO INCREMENT INTEGER
    timestamp : datetime
    log_level : varchar(25)
    originator : varchar(200)
    message : text

如何使用 Criteria API 编写以下 SQL 查询：

SELECT
    timestamp,
    log_level
FROM
    log_entries
WHERE
    timestamp > '2013-06-05 00:00:00'
    AND
    originator <> 'com.me.myapp.SomeObject'

Answer 1

您需要使用 ProjectionList 来获取特定的列记录，请按照以下步骤操作

Criteria criteria  = session.createCriteria(LogEntries.class);

//select columns
ProjectionList columns = Projections.projectionList();
columns.add(Projections.property("timestamp"));
columns.add(Projections.property("log_level"));
criteria.setProjection(columns);

//conditions
Criterion timestamp = Restrictions.gt("timestamp", "2013-06-05 00:00:00");
Criterion originator = Restrictions.not(Restrictions.eq("originator", "com.me.myapp.SomeObject"));
LogicalExpression condition = Restrictions.and(timestamp, originator);

criteria.add(condition);
List results = criteria.list();