1. get() and load()
Java代碼
session.get(Clazz, id);
session.load(Clazz, id);
session.get(Clazz, id);
session.load(Clazz, id);
說(shuō)明: load()與get()的區(qū)別
請(qǐng)注意如果沒(méi)有匹配的數(shù)據(jù)庫(kù)記錄，load()方法可能拋出無(wú)法恢復(fù)的異常(unrecoverable exception)。 如果類的映射使用了代理(proxy)，load()方法會(huì)返回一個(gè)未初始化的代理，直到你調(diào)用該代理的某方法時(shí)才會(huì)去訪問(wèn)數(shù)據(jù)庫(kù)。 若你希望在某對(duì)象中創(chuàng)建一個(gè)指向另一個(gè)對(duì)象的關(guān)聯(lián)，又不想在從數(shù)據(jù)庫(kù)中裝載該對(duì)象時(shí)同時(shí)裝載相關(guān)聯(lián)的那個(gè)對(duì)象，那么這種操作方式就用得上的了。 如果為相應(yīng)類映射關(guān)系設(shè)置了batch-size， 那么使用這種操作方式允許多個(gè)對(duì)象被一批裝載（因?yàn)榉祷氐氖谴恚瑹o(wú)需從數(shù)據(jù)庫(kù)中抓取所有對(duì)象的數(shù)據(jù)）。
如果你不確定是否有匹配的行存在，應(yīng)該使用get()方法，它會(huì)立刻訪問(wèn)數(shù)據(jù)庫(kù)，如果沒(méi)有對(duì)應(yīng)的行，會(huì)返回null。
2. HQL
Java代碼
復(fù)制代碼 代碼如下:
// 返回一行記錄
String hql = "from TOrder o where o.id = ?";
TOrder o = (TOrder) s.createQuery(hql)
.setParameter(0, orderId)
.uniqueResult();
// 命名參數(shù)
Query q = sess.createQuery("from DomesticCat cat where cat.name = :name");
q.setString("name", "Fritz");
// 位置參數(shù)
Query q = sess.createQuery("from DomesticCat cat where cat.name = ?");
q.setString(0, "Izi");
// 命名參數(shù)列表
Query q = sess.createQuery("from DomesticCat cat where cat.name in (:namesList)");
q.setParameterList("namesList", names);
// 分頁(yè)查詢
Query q = sess.createQuery("from DomesticCat cat");
q.setFirstResult(20);
q.setMaxResults(10);
List cats = q.list();
3. Criteria
List cats = sess.createCriteria(Cat.class)
.add( Restrictions.like("name", "Fritz%") )
.add( Restrictions.or(
Restrictions.eq( "age", new Integer(0) ),
Restrictions.isNull("age")
) )
.addOrder( Order.asc("name") )
.addOrder( Order.desc("age") )
.list();
// 返回一行記錄
String hql = "from TOrder o where o.id = ?";
TOrder o = (TOrder) s.createQuery(hql)
.setParameter(0, orderId)
.uniqueResult();
// 命名參數(shù)
Query q = sess.createQuery("from DomesticCat cat where cat.name = :name");
q.setString("name", "Fritz");
// 位置參數(shù)
Query q = sess.createQuery("from DomesticCat cat where cat.name = ?");
q.setString(0, "Izi");
// 命名參數(shù)列表
Query q = sess.createQuery("from DomesticCat cat where cat.name in (:namesList)");
q.setParameterList("namesList", names);
// 分頁(yè)查詢
Query q = sess.createQuery("from DomesticCat cat");
q.setFirstResult(20);
q.setMaxResults(10);
List cats = q.list();
3. Criteria
復(fù)制代碼 代碼如下:
List cats = sess.createCriteria(Cat.class)
.add( Restrictions.like("name", "Fritz%") )
.add( Restrictions.or(
Restrictions.eq( "age", new Integer(0) ),
Restrictions.isNull("age")
) )
.addOrder( Order.asc("name") )
.addOrder( Order.desc("age") )
.list();
4. Native SQL
Java代碼
復(fù)制代碼 代碼如下:
String treeSql = "" +
"select , level from tree t " +
" start with t.parent_id = 0 " +
" connect by prior t.id = t.parent_id";
List result = session.createSQLQuery(treeSql)
.addEntity("t", Tree.class)
.addScalar("level", Hibernate.INTEGER)
.list();
String treeSql = "" +
"select , level from tree t " +
" start with t.parent_id = 0 " +
" connect by prior t.id = t.parent_id";
List result = session.createSQLQuery(treeSql)
.addEntity("t", Tree.class)
.addScalar("level", Hibernate.INTEGER)
.list();
5. Named SQL queries(不推薦)
6. filter(不推薦)
7. Detached queries(還沒(méi)測(cè)試)
The DetachedCriteria class lets you create a query outside the scope of a session, and then later execute it using some arbitrary Session
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