dao(数据库通用DAO实现类)

package com.guwenren.service.base;

import java.beans.Introspector;
import java.beans.PropertyDescriptor;
import java.io.Serializable;
import java.lang.reflect.Method;
import java.util.LinkedHashMap;
import javax.annotation.Resource;
import javax.persistence.EmbeddedId;
import javax.persistence.Entity;

import org.hibernate.Query;
import org.hibernate.SessionFactory;
import org.springframework.transaction.annotation.Propagation;
import org.springframework.transaction.annotation.Transactional;

import com.guwenren.bean.QueryResult;
import com.guwenren.utils.GenericsUtils;

@Transactional
public abstract class DaoSupport<T> implements DAO<T> {
    @SuppressWarnings("unchecked")
    protected Class<T> entityClass=GenericsUtils.getSuperClassGenricType(this.getClass());
    @Resource
    protected  SessionFactory factory;
    
    public long getCount() {
        return (Long)factory.getCurrentSession().createQuery("select count("+ getCountField(this.entityClass) +") from "+ getEntityName(this.entityClass)+ " o").uniqueResult();
    }
    public void clear() {
        factory.getCurrentSession().clear();        
    }

    public void save(T entity) {
        factory.getCurrentSession().persist(entity);
    }
    public void update(T entity) {
        factory.getCurrentSession().merge(entity);
    }
    public void delete(Serializable... serializables) {
        for(Object id  : serializables){
            factory.getCurrentSession().delete(factory.getCurrentSession().load(entityClass, (Serializable) id));
        }
    }
    @SuppressWarnings("unchecked")
    @Transactional(readOnly=true,propagation=Propagation.NOT_SUPPORTED)
    public T find(Serializable serializable) {
        if(serializable==null) throw new RuntimeException(this.entityClass.getName()+ ":传入的实体id不能为空");
        return (T) factory.getCurrentSession().get(this.entityClass, serializable);//load
    }

    @Transactional(readOnly=true,propagation=Propagation.NOT_SUPPORTED)
    public QueryResult<T> getScrollData(int firstindex, int maxresult,
            String wherejpql, Object[] queryParams) {
         return getScrollData(firstindex,maxresult,wherejpql,queryParams,null);
    }
    @Transactional(readOnly=true,propagation=Propagation.NOT_SUPPORTED)
    public QueryResult<T> getScrollData(int firstindex, int maxresult,
            LinkedHashMap<String, String> orderby) {
        return getScrollData(firstindex,maxresult,null,null,orderby);
    }
    @Transactional(readOnly=true,propagation=Propagation.NOT_SUPPORTED)
    public QueryResult<T> getScrollData(int firstindex, int maxresult) {
        return getScrollData(firstindex,maxresult,null,null,null);
    }
    @Transactional(readOnly=true,propagation=Propagation.NOT_SUPPORTED)
    public QueryResult<T> getScrollData() {
        return getScrollData(-1,-1);
    }
    @SuppressWarnings("unchecked")
    @Transactional(readOnly=true,propagation=Propagation.NOT_SUPPORTED)
    public QueryResult<T> getScrollData(int firstindex, int maxresult,
            String wherejpql, Object[] queryParams, 
            LinkedHashMap<String, String> orderby) {
        QueryResult<T> qr = new QueryResult<T>();
        String entityname = getEntityName(this.entityClass);
        String wherestr=(wherejpql==null || "".equals(wherejpql.trim())? "": " where "+ wherejpql);    
        String querystr="select o from "+entityname+" o"+wherestr+buildOrderby(orderby);
        Query query = factory.getCurrentSession().createQuery(querystr);
        setQueryParams(query, queryParams);
        if(firstindex!=-1 && maxresult!=-1){
            query.setFirstResult(firstindex).setMaxResults(maxresult);
        }
        qr.setResultlist(query.list());
        if(firstindex!=-1 && maxresult!=-1){
            query=factory.getCurrentSession().createQuery("select count(o) from "+entityname+" o"+wherestr);
            setQueryParams(query, queryParams);
            qr.setTotalrecord((Long)query.uniqueResult());
        }
        return qr;
    }
    /**
     * 组装where 语句
     * @param orderby
     */
    protected static void setQueryParams(Query query, Object[] queryParams){
        if(queryParams!=null && queryParams.length>0){
            for(int i=0; i<queryParams.length; i++){
                query.setParameter(i, queryParams[i]);
            }
        }
    }
    /**
     * 组装order by语句
     * @param orderby
     * @return
     */
    protected static String buildOrderby(LinkedHashMap<String, String> orderby){
        StringBuffer orderbyql = new StringBuffer("");
        if(orderby!=null && orderby.size()>0){
            orderbyql.append(" order by ");
            for(String key : orderby.keySet()){
                orderbyql.append("o.").append(key).append(" ").append(orderby.get(key)).append(",");
            }
            orderbyql.deleteCharAt(orderbyql.length()-1);
        }
        return orderbyql.toString();
    }
    /**
     * 获取实体的名称
     * @param <E>
     * @param clazz 实体类
     * @return
     */
    protected static <E> String getEntityName(Class<E> clazz){
        String entityname = clazz.getSimpleName();
        Entity entity = clazz.getAnnotation(Entity.class);
        if(entity.name()!=null && !"".equals(entity.name())){
            entityname = entity.name();
        }
        return entityname;
    }    
    /**
     * 获取统计属性,该方法是为了解决hibernate解析联合主键select count(o) from Xxx o语句BUG而增加,
     * hibernate对此jpql解析后的sql为select count(field1,field2,...),显示使用count()统计多个字段是错误的
     * @param <E>
     * @param clazz
     * @return
     */
    protected static <E> String getCountField(Class<E> clazz){
        String out = "o";
        try {
            PropertyDescriptor[] propertyDescriptors = Introspector.getBeanInfo(clazz).getPropertyDescriptors();
            for(PropertyDescriptor propertydesc : propertyDescriptors){
                Method method = propertydesc.getReadMethod();
                if(method!=null && method.isAnnotationPresent(EmbeddedId.class)){                    
                    PropertyDescriptor[] ps = Introspector.getBeanInfo(propertydesc.getPropertyType()).getPropertyDescriptors();
                    out = "o."+ propertydesc.getName()+ "." + (!ps[1].getName().equals("class")? ps[1].getName(): ps[0].getName());
                    break;
                }
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
        return out;
    }
    
}