Hibernate - 查询部分字段

第一种是使用高级查询DetachedCriteria实现，代碼如下：

String alias = "user_"; //查詢時的table別名

DetachedCriteria dc = DetachedCriteria.forClass(User.class,alias);

ProjectionList pList = Projections.projectionList();

pList.add(Projections.property(alias + "." + "id").as("id"));

pList.add(Projections.property(alias + "." + "name").as("name"));

pList.add(Projections.property(alias + "." + "age").as("age"));

pList.add(Projections.property(alias + "." + "sex").as("sex"));

dc.setProjection(pList);

dc.setResultTransformer(Transformers.aliasToBean(User.class));

resultList = memberService.findByDetached(dc).size();

通過HQL语句查询

String hql = "select new Link(id,name) from Link";     

Query query = session.createQuery(hql);

//默认查询出来的list里存放的是一个Object对象，但是在这里list里存放的不再是默认的Object对象了，而是Link对象了

List links = query.list();

for(Link link : links){

    String id = link.getId();

    String name = link.getName();

    System.out.println(id + " : " + name);

}

第三种方式是通过HQL语句实现，类似SQL，方法如下：

String hql = "select id,name from Link";     

Query query = session.createQuery(hql);

//默认查询出来的list里存放的是一个Object数组，还需要转换成对应的javaBean。

List links = query.list();

for(Object[] link : links){

    String id = link[0];

    String name = link[1];

    System.out.println(id + " : " + name);

}