hibernate乐观锁例子

1.在数据表中新建一个version字段，可以是int或者是bigint

2.在javabean中增加个version字段

package net.spring.model;

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.Table;
import javax.persistence.Version;

@Entity
@Table(name = "t_concurrency")
public class Concurrency {

	@Id
	private int id;
	
    @Version
	private int version;

	public int getId() {
		return id;
	}

	public void setId(int id) {
		this.id = id;
	}

	public int getCount() {
		return count;
	}

	public void setCount(int count) {
		this.count = count;
	}

	@Column
	private int count;

	public int getVersion() {
		return version;
	}

	public void setVersion(int version) {
		this.version = version;
	}

}

3.dao

	@Transactional(rollbackFor = RuntimeException.class,timeout=10)
	@Override
	public void subtract(int id) {
		
		Session session = null;
		
		try {
			session = this.getHibernateTemplate().getSessionFactory().getCurrentSession();

			Query query = session.createQuery("from Concurrency as u where u.id = '" + id + "'");
			
			Concurrency c = new Concurrency();
			c = (Concurrency) query.uniqueResult();

			
			if (c.getCount() > 0) {
				//第一种不行的，没有被hibernate管理，hibernate三种状态符合才行，直接hql更新乐观锁不起效
				//SQLQuery sqlQuery = session.createSQLQuery("update t_concurrency set count=count-1 where id = '"+ id + "'");
				//sqlQuery.executeUpdate(); 
				
				c.setCount(c.getCount()-1);
			}

		} catch (RuntimeException re) {
			throw new RuntimeException();
			
		} finally {
			if (session != null && session.isOpen()) {
				session.flush();
				session.clear();
			}
		}
	}