hibernate的檢索方式

1、導(dǎo)航對(duì)象檢索方式：根據(jù)已經(jīng)加載的對(duì)象導(dǎo)航到其他對(duì)象

Customer customer = session.get(Customer.class, 1);
customer.getOrders();//獲得客戶的訂單    

2、OID檢索方式：按照對(duì)象的OID來(lái)檢索

get()/load():

3、HQL檢索方式：使用面向?qū)ο蟮腍QL語(yǔ)言

Query query = session.createQuery("HQL");

4、QBC檢索方式：使用QBC(Query by Criteria)API來(lái)檢索對(duì)象。這種API封裝了基于字符串形式的查詢語(yǔ)句，提供類更加面向?qū)ο蟮牟樵兘涌凇?/p>

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

5、本地sql檢索方式：使用本地?cái)?shù)據(jù)庫(kù)的sql查詢語(yǔ)句
SQLQuery query = session.createSQLQuery("SQL")

HQL

查詢所有

public void queryAll(){
        Session session = HBUtils.getSession();
        Transaction transaction = session.beginTransaction();
        
        Query query = session.createQuery("from Customer");
        List<Customer> customers = query.list();
        
        transaction.commit();session.close();
    }

使用別名，并加參數(shù)（as可以省略）

public void queryAll(){
        Session session = HBUtils.getSession();
        Transaction transaction = session.beginTransaction();
        
        Query query = session.createQuery("from Customer as c where id = ?").setInteger(0, 1);
        List<Customer> customers = query.list();
        
        transaction.commit();
        session.close();
    }

多態(tài)查詢(查詢繼承自某個(gè)類的所有對(duì)象)

public void queryAll(){
        Session session = HBUtils.getSession();
        Transaction transaction = session.beginTransaction();
        
        List<Object> objects = session.createQuery("from java.lang.Object").list();
            
        transaction.commit();
        session.close();
    }

排序

List<Customer> customers= session.createQuery("from Customer c order by c.id desc").list();

分頁(yè)查詢

List<Customer> customers= session.createQuery("from Customer").setFirstResult(0).setMaxResults(10).list();

獲取單個(gè)對(duì)象

Customer customer= (Customer) session.createQuery("from Customer where id = ?").setInteger(0, 1).uniqueResult();

參數(shù)綁定

？綁定
Customer customer= (Customer) session.createQuery("from Customer where id = ?").setInteger(0, 1).uniqueResult();
名稱綁定        
Customer customer= (Customer) session.createQuery("from Customer where id = :id").setInteger("id", 1).uniqueResult();

投影查詢

List<String> names = session.createQuery("select c.name from Customer as c").list();
List<Object[]> objects = session.createQuery("select c.id, c.name from Customer as c").list();

List<Customer> customers = session.createQuery("select new Customer(c.id, c.name) from Customer as c").list();//這種方式的前提是必須有new Customer(c.id, c.name) 構(gòu)造函數(shù)      

綁定實(shí)體

Customer customer = new Customer();
        customer.setCid(1);
        List<Order> orders = session.createQuery("from Order o where o.customer = ?").setEntity(0, customer).list();

模糊查詢

List<Customer> customers = session.createQuery("from Customer where name like ?").setParameter(0, "小%").list();

內(nèi)鏈接

List<Customer> customers = session.createQuery("from Customer c inner join c.orders").list();

迫切內(nèi)鏈接

List<Customer> customers = session.createQuery("from Customer c inner join fetch c.orders").list();

內(nèi)鏈接和迫切內(nèi)鏈接的區(qū)別：
內(nèi)鏈接：將數(shù)據(jù)封裝到一個(gè)List<Object[]>中
迫切內(nèi)鏈接：將數(shù)據(jù)封裝到一個(gè)List<Customer>中，，并且迫切內(nèi)鏈接會(huì)有重復(fù)的記錄，需要使用distinct去重。

QBC

查詢所有

public void queryAll(){
        Session session = HBUtils.getSession();
        Transaction transaction = session.beginTransaction();
        
        Criteria criteria = session.createCriteria(Customer.class);
        List<Customer> customers = criteria.list();
        
        transaction.commit();session.close();
    }

排序

List<Customer> customers= session.createCriteria(Customer.class).addOrder(org.hibernate.criterion.Order.desc("cid")).list();

分頁(yè)查詢

List<Customer> customers= session.createCriteria(Customer.class).setFirstResult(0).setMaxResults(10).list();

獲取單個(gè)對(duì)象

Customer customer= (Customer) session.createCriteria(Customer.class).add(Restrictions.eq("id", 1)).uniqueResult();

模糊查詢

Customer customer= (Customer) session.createCriteria(Customer.class).add(Restrictions.like("name", "小%")).list();

離線的條件查詢

DetachedCriteria criteria = DetachedCriteria.forClass(Customer.class);
criteria.add(Restrictions.eq("", ""));
Criteria c = criteria.getExecutableCriteria(session);
List<Customer> customers = c.list();

QBC函數(shù)

HQL和QBC比較

鏈接查詢

離線的條件查詢

SQL

查詢所有

public void queryAll(){
        Session session = HBUtils.getSession();
        Transaction transaction = session.beginTransaction();
        
//      List<Object[]> customers = session.createSQLQuery("select * from customer").list();
        List<Customer> customers = session.createSQLQuery("select * from customer").addEntity(Customer.class).list();
        
        transaction.commit();
        session.close();
    }

延遲檢索

get()/load()
延遲檢索失效：
1、檢索的對(duì)象用filan修飾，此時(shí)不能生成代理對(duì)象
2、將映射文件中的class標(biāo)簽的的lazy屬性改為false。

類級(jí)別的檢索和關(guān)聯(lián)級(jí)別的檢索

類級(jí)別的檢索：在<class>上配置lazy
關(guān)聯(lián)級(jí)別的檢索：在<set>/<many-to-one>上設(shè)置lazy

從一的一方關(guān)聯(lián)多的一方，在<set>上進(jìn)行配置

fetch：控制sql語(yǔ)句的類型

join：發(fā)送迫切左外鏈接
select：默認(rèn)值
subselect：發(fā)送子查詢語(yǔ)句，查詢關(guān)聯(lián)對(duì)象。如果查詢一個(gè)則會(huì)使用“=”，如果多個(gè)，則發(fā)送子查詢，使用“in”

lazy：控制關(guān)系對(duì)象的檢索是否采用延遲

true：默認(rèn)值：使用延遲檢索
false：不使用延遲檢索
extra：及其懶惰，使用什么信息，就發(fā)送什么sql
如果fetch是join的情況，lazy屬性將會(huì)被忽略

在多的一方關(guān)聯(lián)一的一方，在<many-to-one>上進(jìn)行配置

fetch

join：發(fā)送迫切左外鏈接，fatch=join，lazy屬性將會(huì)被忽略
select：發(fā)送多條sql檢索關(guān)聯(lián)對(duì)象

lazy

false：不延遲
proxy：使用代理。檢索訂單的時(shí)候，是否馬上檢索客戶，有customer對(duì)象的映射文件中<class>上的lazy屬性決定。
no-proxy：不使用代理

批量抓取

抓取客戶的訂單：在客戶的<set>集合上配置batch-size = "3",即一次抓取三條。
抓取訂單的客戶：在客戶的<class>標(biāo)簽上配置batch-size

事物隔離

在核心配置文件中配置。

<property name = "hibernate.connection.isolation">4</property>
1-Read uncommitted isolation(最低)
2-Read committed isolation
3-Repeattable read isolation
4-Serializable isolation(最高)

線程綁定session

在hibernate核心配置文件中配置

<property name = "hibernate.current_session_context_class">thread</property>

使用Sessionactory中的getCurrentSession方法
底層就是ThreadLocal
當(dāng)前線程中的session不需要關(guān)閉，線程結(jié)束就會(huì)自動(dòng)關(guān)閉