public <T> QueryResult<T> getScrollData(Class<T> entityClass,String wherejpql,Object[] queryParams,int firstindex, int maxResult, LinkedHashMap<String, String> orderby) {//for(int i = 0;i<queryParams.length;i++){//System.out.println("=================queryParams is " + i +queryParams[i]);//}String entityName = getEntityName(entityClass);QueryResult qr = new QueryResult<T>();String sql = "select o from "+entityName+" o " + (wherejpql==null?"":"where " + wherejpql) + buildOrderby(orderby);Query query = em.createQuery(sql);setQueryParams(query,queryParams);System.out.println("-------------------in DaoSupport :sql is:" + sql);/** * 1：查询的时候第一步查询到的都是数据表里所有的记录 * 2：再用query.setFirstResult(firstindex).setMaxResults(maxResult) * 方法来设置要显示的首记录（即从哪一条开始显示）和要显示的记录条数 * 3：然后保存相关数据，方便前台页面显示 */if(firstindex != -1 && maxResult != -1){query.setFirstResult(firstindex).setMaxResults(maxResult);}qr.setResultList(query.getResultList());/** * 这里的记录数不是要显示的记录有多少条，而是数据表里一共有多少条记录 */query = em.createQuery("select count(o) from "+entityName+" o " + (wherejpql==null?"":"where " + wherejpql));setQueryParams(query,queryParams);qr.setTotalrecord((Long)query.getSingleResult());return qr;}
/** * 构建order by 语句 * orderby 语句格式：order by key1 asc,key2 asc * @param orderby * @return */protected String buildOrderby(LinkedHashMap<String, String> orderby){StringBuffer orderbySql = new StringBuffer("");if(orderby !=null && orderby.size()>0){orderbySql.append(" order by ");//order by key1 desc,key2 ascfor(String key:orderby.keySet()){orderbySql.append(key).append(" ").append(orderby.get(key)).append(",");}orderbySql.deleteCharAt(orderbySql.length() - 1);}return orderbySql.toString();}
/** * 给where语句设置参数值 * wherejpql 语句格式：where o.property=?1,o.property=?2。 * @param query * @param params */protected void setQueryParams(Query query,Object[] params){if(params != null && params.length > 0){for(int i=0;i<params.length;i++){//System.out.println("i+1 = " + (i+1) + " params[i] " + params[i] );query.setParameter(i+1, params[i]);}}}
QueryResult.java:
package com.itcast.util;
import java.util.List;
public class QueryResult<T>{private List<T> resultList;private long totalrecord;public List<T> getResultList() {return resultList;}public void setResultList(List<T> resultList) {this.resultList = resultList;}public long getTotalrecord() {return totalrecord;}public void setTotalrecord(long totalrecord) {this.totalrecord = totalrecord;}
}
