JavaWeb项目开发案例精粹-第6章报价管理系统-03Dao层

1.

package com.sanqing.dao;

import java.io.Serializable;
import java.util.LinkedHashMap;

import com.sanqing.util.QueryResult;


public interface DAO<T> {
    public long getCount();//获得记录总数
    public void clear();//清除一级缓存的数据
    public void save(Object entity);//保存记录
    public void update(Object entity);//更新记录
    public void delete(Serializable ... entityids);//删除记录
    public T find(Serializable entityId);//通过主键获得记录
    public QueryResult<T> getScrollData(int firstindex, int maxresult, String wherejpql, 
                    Object[] queryParams,LinkedHashMap<String, String> orderby);//获得分页记录
    public QueryResult<T> getScrollData(int firstindex, int maxresult,
                                        String wherejpql, Object[] queryParams);//获得分页记录
    public QueryResult<T> getScrollData(int firstindex, int maxresult,
                                        LinkedHashMap<String, String> orderby);//获得分页记录
    public QueryResult<T> getScrollData(int firstindex, int maxresult);        //获得分页记录
    public QueryResult<T> getScrollData();//获得分页记录
}

2.

package com.sanqing.dao;

import java.beans.Introspector;
import java.beans.PropertyDescriptor;
import java.io.Serializable;
import java.lang.reflect.Method;
import java.util.LinkedHashMap;

import javax.persistence.EmbeddedId;
import javax.persistence.Entity;
import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;
import javax.persistence.Query;

import org.springframework.transaction.annotation.Propagation;
import org.springframework.transaction.annotation.Transactional;

import com.sanqing.util.GenericsUtils;
import com.sanqing.util.QueryResult;

@SuppressWarnings("unchecked")
@Transactional
public abstract class DaoSupport<T> implements DAO<T>{
    protected Class<T> entityClass = GenericsUtils.getSuperClassGenricType(this.getClass());//获得该类的父类的泛型参数的实际类型
    @PersistenceContext protected EntityManager em;
    public void clear(){//清除一级缓存的数据
        em.clear();
    }
    public void delete(Serializable ... entityids) {//删除记录
        for(Object id : entityids){
            em.remove(em.getReference(this.entityClass, id));
        }
    }
    @Transactional(readOnly=true,propagation=Propagation.NOT_SUPPORTED)
    public T find(Serializable entityId) {//通过主键获得记录
        if(entityId==null) throw new RuntimeException(this.entityClass.getName()+ ":传入的实体id不能为空");
        return em.find(this.entityClass, entityId);
    }
    public void save(Object entity) {//保存记录
        em.persist(entity);
    }
    @Transactional(readOnly=true,propagation=Propagation.NOT_SUPPORTED)
    public long getCount() {    //获得记录总数
        return (Long)em.createQuery("select count("+ getCountField(this.entityClass) +") from "+ getEntityName(this.entityClass)+ " o").getSingleResult();
    }
    
    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;
    }
    
    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+1, queryParams[i]);
            }
        }
    }
    protected static String buildOrderby(LinkedHashMap<String, String> orderby){//组装order by语句
        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();
    }
    protected static <E> String getEntityName(Class<E> clazz){//获取实体的名称
        String entityname = clazz.getSimpleName();
        Entity entity = clazz.getAnnotation(Entity.class);
        if(entity.name()!=null && !"".equals(entity.name())){
            entityname = entity.name();
        }
        return entityname;
    }
    
    public void update(Object entity) {//更新记录
        em.merge(entity);
    }
    @Transactional(readOnly=true,propagation=Propagation.NOT_SUPPORTED)
    public QueryResult<T> getScrollData(int firstindex, 
                int maxresult, LinkedHashMap<String, String> orderby) {//获得分页记录
        return getScrollData(firstindex,maxresult,null,null,orderby);
    }
    @Transactional(readOnly=true,propagation=Propagation.NOT_SUPPORTED)
    public QueryResult<T> getScrollData(int firstindex, 
            int maxresult, String wherejpql, Object[] queryParams) {//获得分页记录
        return getScrollData(firstindex,maxresult,wherejpql,queryParams,null);
    }
    @Transactional(readOnly=true,propagation=Propagation.NOT_SUPPORTED)
    public QueryResult<T> getScrollData(int firstindex, int maxresult) {//获得分页记录
        return getScrollData(firstindex,maxresult,null,null,null);
    }
    @Transactional(readOnly=true,propagation=Propagation.NOT_SUPPORTED)
    public QueryResult<T> getScrollData() {
        return getScrollData(-1, -1);
    }
    @Transactional(readOnly=true,propagation=Propagation.NOT_SUPPORTED)
    public QueryResult<T> getScrollData(int firstindex, int maxresult, String wherejpql,
            Object[] queryParams,LinkedHashMap<String, String> orderby) {//获得分页记录
        QueryResult qr = new QueryResult<T>();//查询记录结果
        String entityname = getEntityName(this.entityClass);//获得实体名称
        Query query = em.createQuery("select o from "+ 
                entityname+ " o "+(wherejpql==null 
                || "".equals(wherejpql.trim())? "":
                "where "+ wherejpql)+ buildOrderby(orderby));//执行查询
        setQueryParams(query, queryParams);//设置查询参数
        if(firstindex!=-1 && maxresult!=-1) //两个参数都不是-1的时候才分页
            query.setFirstResult(firstindex).
            setMaxResults(maxresult);//设置查询记录的起始位置和查询最大数
        qr.setResultlist(query.getResultList());//设置查询的记录
        query = em.createQuery("select count(" +
                getCountField(this.entityClass)+ ") " +
                "from "+ entityname+ " o "+(wherejpql==null ||
                "".equals(wherejpql.trim())? "": "where "+ wherejpql));
        setQueryParams(query, queryParams);//设置查询参数
        qr.setTotalrecord((Long)query.getSingleResult());//设置查询记录总数
        return qr;//返回查询记录结果
    }

    
}