分页缓存设置

1，对于分页来说，效率是关键，本例是在分页的时候，缓存5页记录，默认每页20条，缓存大小100，这可以修改的；

2，基本思路是：第一次查的时候，先判断缓存中存不存在当前页的数据，如果存在，查找缓存中的数据，如果不存在，则去数据库中查询5页数据放入缓存中，然后再缓存中读取数据。如果是当前页是前3页，那么读取1-5页的数据，如果当前页是后3页，读取后5页的数据，如果是中间页，读取当前页前两页+当前页+当前页后两页的数据；

一，分页的参数封装类、返回结果封装类；

package com.dg11185.iyw.common;/** * 分页的参数类 *  * @author 黄文韬 * @since 1.0 * @Copyright 2013 东莞市邮政局All rights reserved. */public class PagingParams {private Integer nextPage;// 需要显示内容的页码private Integer pageSize; // 每页的条数private String allSizeHql; // 查询总记录条数的hqlprivate String queryHql; // 查询记录的hqlprivate Class clazz;  //查询对象的class类//设置下一页的页码public Integer getNextPage() {if (nextPage == null || "".equals(nextPage)) {return  1;}else {return nextPage;}}public Class getClazz() {return clazz;}public void setClazz(Class clazz) {this.clazz = clazz;}public void setNextPage(Integer nextPage) {this.nextPage = nextPage;}public Integer getPageSize() {if (pageSize == null || "".equals(pageSize)) {int configSize = Integer.parseInt(SysConfig.getProperty("pageSize"));return configSize;}else {   return pageSize;}}//设置每页条数public void setPageSize(Integer pageSize) {this.pageSize = pageSize;}public String getAllSizeHql() {return allSizeHql;}public void setAllSizeHql(String allSizeHql) {this.allSizeHql = allSizeHql;}public String getQueryHql() {return queryHql;}public void setQueryHql(String queryHql) {this.queryHql = queryHql;}}

package com.dg11185.iyw.common;import java.util.List;/** * 分页结果类 *  * @author 黄文韬 * @since 1.0 * @Copyright 2013 东莞市邮政局All rights reserved. */public class PagingResults {private int currentPage; //当前页码private int totalSize;   //总共条数private int totalPages;  //总共页数private List list;       //结果集public int getCurrentPage() {return currentPage;}public void setCurrentPage(int currentPage) {this.currentPage = currentPage;}public int getTotalSize() {return totalSize;}public void setTotalSize(int totalSize) {this.totalSize = totalSize;}public int getTotalPages() {return totalPages;}public void setTotalPages(int totalPages) {this.totalPages = totalPages;}public List getList() {return list;}public void setList(List list) {this.list = list;}}

二，分页缓存类

package com.dg11185.iyw.common;import java.io.IOException;import java.util.ArrayList;import java.util.List;import javax.annotation.Resource;import org.apache.log4j.Logger;import com.dg11185.iyw.baseDAO.BaseDAOImpl;/** * 分页缓存类 * @author hwt * */public class CachePage {private static final Logger LOGGER = Logger.getLogger(CachePage.class);@Resourceprivate BaseDAOImpl baseDAOImpl;private int pageStart = 1; // 页码private int pageSize = 20; // 每页显示的大小private int pageNum = 0;  //总页数private int totalNum = 0; //总记录条数//private int cacheSize = 100; // 缓存大小private List cacheList = new ArrayList(); // 缓存列表/** * 构造方法 * @param pageSize 每页大小 * @param cacheSize 缓存大小 */public CachePage(Integer pageSize) {this.pageSize = pageSize;}/** * 判断是否存在缓存中 *  * @param page *            页码 * @return */public boolean inCache(int page) {// 当前缓存对象的个数   int cacheNum = cacheList.size();   if (cacheNum > 0) {if (page <= 0) {page = 1;}// 判断当前页是不是在缓存中if (page >= pageStart && (page - pageStart) * pageSize <= cacheNum) {return true;} else {return false;}}else {return false;}}/** * 清空缓存 * @param pageNum 起始页 */public void refleshCache() {//this.isFirst = true;for (int i = cacheList.size() -1 ; i  >= 0; i--) {cacheList.remove(i);}}/** * 新增缓存 *  * @param doc */public void addCache(Object obj) {if (this.cacheList.size() < pageSize*5) {this.cacheList.add(obj);} else {LOGGER.info("缓存池已满");}}/** * 读缓存中的数据 * @param page * @return */public PagingResults readCache(int page) {int start = (page - pageStart) * pageSize;int end = start + pageSize > cacheList.size() ? cacheList.size(): start + pageSize;//缓存中的结果集List cacheRs = new ArrayList();for (int i = start; i < end; i++) {cacheRs.add(cacheList.get(i));}//缓存结果集PagingResults pageResult = new PagingResults();pageResult.setCurrentPage(page); //当前页pageResult.setTotalSize(totalNum); //总记录条数pageResult.setTotalPages(pageNum); //总页数pageResult.setList(cacheRs);return pageResult;}/** * 搜索 * @param query query对象 * @param sort 排序对象 * @param page 页码 * @return */public PagingResults search(PagingParams params) throws IOException{int page = params.getNextPage();if (page < 0) {page = 1;}//如果存在缓存中if (inCache(page)) {return readCache(page);}else {//如果不在缓存中//总共记录条数int totalNum = baseDAOImpl.getSum(params.getAllSizeHql());//总页数int pageNum = totalNum % pageSize == 0 ? totalNum / pageSize : totalNum / pageSize + 1;if (page > pageNum) {page = pageNum;}//保存当前页的前后两页放入缓存中int startPage = 1;int endPage   = 1;if (page <= 5) { //前五页startPage = 1;endPage = startPage + 4 > pageNum ? pageNum : startPage + 4;}else if(page >= pageNum - 4){ //后五页endPage = pageNum ;startPage = endPage - 4 < 0 ? 1 : endPage - 4;} else { //中间页startPage = page - 2 <= 0 ? 1 : page - 2;endPage   = page + 2 > pageNum ? pageNum : page + 2;}//清空缓存refleshCache();//得到缓存结果集List resultList = baseDAOImpl.getAllResults(params.getQueryHql(),startPage,pageSize*5,params.getClazz());//将对象加入缓存中for (int i = 0,len = resultList.size() ; i < len; i++) {addCache(resultList.get(i));}//替换缓存集合this.pageNum = pageNum;this.totalNum = totalNum;this.pageStart = startPage;return readCache(page);}}public Integer getPageSize() {return pageSize;}public void setPageSize(Integer pageSize) {this.pageSize = pageSize;}public Integer getPageStart() {return pageStart;}public void setPageStart(Integer pageStart) {this.pageStart = pageStart;}//public Integer getCacheSize() {//return cacheSize;//}////public void setCacheSize(Integer cacheSize) {//this.cacheSize = cacheSize;//}}

三，dao层的两个方法，其他方法省略....

package com.dg11185.iyw.baseDAO;import java.sql.CallableStatement;import java.sql.Connection;import java.sql.PreparedStatement;import java.sql.ResultSet;import java.sql.ResultSetMetaData;import java.sql.SQLException;import java.util.ArrayList;import java.util.HashMap;import java.util.List;import java.util.Map;import javax.annotation.Resource;import javax.sql.DataSource;import org.springframework.dao.DataAccessException;import org.springframework.jdbc.core.BatchPreparedStatementSetter;import org.springframework.jdbc.core.CallableStatementCallback;import org.springframework.jdbc.core.CallableStatementCreator;import org.springframework.jdbc.core.SqlParameter;import org.springframework.jdbc.core.support.JdbcDaoSupport;import org.springframework.stereotype.Repository;import com.dg11185.iyw.common.ObjectRowMapper;import com.dg11185.iyw.common.PagingParams;/** * BaseDAO的实现类 *  * @author 黄文韬 * @since 1.0 * @Copyright 2013 东莞市邮政局All rights reserved. */@Repositorypublic class BaseDAOImpl extends JdbcDaoSupport implements BaseDAO {@Resource(name = "dataSource")public void setMyDataSource(DataSource dataSource) {super.setDataSource(dataSource);}/** * 根据序列得到记录的ID *  * @param seqName * @return */@Overridepublic int getTableId(String seqName) {String queryId = "select " + seqName + ".nextval from dual";return getJdbcTemplate().queryForInt(queryId);}/** * 得到所有的记录 *  * @param sql 查询sql * @param startPage  起始页 * @param pageSize 每页大小 * @param claszz 查询的类名 * @return */public List getAllResults(String sql, Integer startPage, Integer pageSize,Class claszz) {// 终止位置int start = (startPage - 1) * pageSize + 1;int end = startPage * pageSize;// 得到分页数据String allSQL = "select * from(select rownum rn,e.* from (" + sql+ ") e where rownum <= " + end + ") where rn >= " + start;List locations = getJdbcTemplate().query(allSQL,new ObjectRowMapper(claszz));return locations;}/** * 得到总共的数据 *  * @param sql * @return */@Overridepublic int getSum(String sql, Object... obj) {return getJdbcTemplate().queryForInt(sql, obj);}       //。。。。(其他方法省略)}