本文主要是介绍Apache Torque实现分页查询，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！
- 1.分页查询工具类
- 2.测试类
Apache Torque实现分页查询
Torque的初始化参见Apache Torque连接多个数据库及其使用
1.分页查询工具类
import java.util.List;
import org.apache.torque.TorqueException;
import org.apache.torque.util.LargeSelectExtend;
import com.workingdogs.village.Record;public class TorqueQueryByPageUtils {private static LargeSelectExtend largeSelect;/*** 查询分页结果* @param isFirstQuery 是否是第一次查询* @param pageConstant* @param countSql* @param querySql* @param dbName* @return*/@SuppressWarnings("unchecked")public static List<Record> getResultsWithSql(boolean isFirstQuery, PageConstant pageConstant, String countSql, String querySql, String dbName) {List<Record> results = null;try {int pageSize = pageConstant.getPageSize() <= 0 ? 10 : pageConstant.getPageSize();/**默认的读入内存的页数，数据读入内存，可以提高前台响应用户请求数据的速度，但如果读入内存的数据太多，会占用服务器过多内存*/int memoryPageLimit = pageConstant.getMemoryPageLimit() <= 0 ? 10 : pageConstant.getMemoryPageLimit();if (isFirstQuery) {/**使用标准的大查询器查询，标准的大查询器返回的List里都是具体的数据对象的集合*/largeSelect = new LargeSelectExtend(countSql, querySql, pageSize,memoryPageLimit, dbName);results = largeSelect.getPage(pageConstant.getPageIndex());largeSelectExtendProperties();/**数据库里的总页数*/int realTotalPages = largeSelect.getRealTotalPages();System.out.println("realTotalPages:"+realTotalPages);} else {/**数据库里的总页数*/int realTotalPages = largeSelect.getRealTotalPages();System.out.println("realTotalPages:"+realTotalPages);if (!(pageConstant.getPageIndex() > realTotalPages)) {/**获取某页数的结果*/results = largeSelect.getPage(pageConstant.getPageIndex());largeSelectExtendProperties();}}} catch (TorqueException e) {e.printStackTrace();}return results;}@SuppressWarnings("unchecked")private static void largeSelectExtendProperties() {try {/**当前页码数*/int currentPageNumber = largeSelect.getCurrentPageNumber();/**读入内存的页数*/int memoryTotalPages = largeSelect.getMemoryTotalPages();/**读入内存的总记录数*/int memoryTotalRecords = largeSelect.getMemoryTotalRecords();/**数据库实际总记录数*/int realTotalCount = largeSelect.getRealTotalCount();/**是否有上一页结果*/boolean previousResultsAvailable = largeSelect.getPreviousResultsAvailable();if (previousResultsAvailable) {/**上一页数据结果*/List<Record> previousResults = largeSelect.getPreviousResults();System.out.println("previousResults:"+previousResults);}/**是否有下一页结果*/boolean nextResultsAvailable = largeSelect.getNextResultsAvailable();if (nextResultsAvailable) {/**下一页数据结果*/List<Record> nextResults = largeSelect.getNextResults();System.out.println("nextResults:"+nextResults);}System.out.println("currentPageNumber:"+currentPageNumber);System.out.println("memoryTotalPages:"+memoryTotalPages);System.out.println("memoryTotalRecords:"+memoryTotalRecords);System.out.println("realTotalCount:"+realTotalCount);System.out.println("previousResultsAvailable:"+previousResultsAvailable);System.out.println("nextResultsAvailable:"+nextResultsAvailable);} catch (Exception e) {e.printStackTrace();}}}注：上述若能执行getPreviousResults()，说明已经翻页到上一页了，那么执行到getNextResultsAvailable()和getNextResults()就是按照上一页的结果进行的，反之亦然，此处只是显示largeSelectExtend的一些属性数据。
思考：上述getResultsWithSql()方法中间部分代码块改写为如下代码，打印出的realTotalPages一直是-1；将休眠的代码注释打开，realTotalPages能正常获取到数值。所以先进行一次页数的查询，就可以正常获取到realTotalPages的数值。
if (isFirstQuery) {/**使用标准的大查询器查询，标准的大查询器返回的List里都是具体的数据对象的集合*/largeSelect = new LargeSelectExtend(countSql, querySql, pageSize,memoryPageLimit, dbName);
}
//try {
// Thread.sleep(1000);
//} catch (InterruptedException e) {
// e.printStackTrace();
//}
/**数据库里的总页数*/
int realTotalPages = largeSelect.getRealTotalPages();
System.out.println("realTotalPages:"+realTotalPages);
if (!(pageConstant.getPageIndex() > realTotalPages)) {/**获取某页数的结果*/results = largeSelect.getPage(pageConstant.getPageIndex());largeSelectExtendProperties();
}public class PageConstant {/*** 页码*/private int pageIndex;/*** 每页包含记录条数*/private int pageSize;/*** 每次读入内存的页数*/private int memoryPageLimit;/*** 已经读入到内存的页数*/private int memoryTotalPages;/*** 下一页*/private int nextPage;/*** 上一页*/private int previousPage;/*** 数据库总记录数*/private int totalCount;/*** 数据库总页数*/private int totalPages;/*** 当前页*/private int currentPage;public int getPageIndex() {return pageIndex;}public void setPageIndex(int pageIndex) {this.pageIndex = pageIndex;}public int getPageSize() {return pageSize;}public void setPageSize(int pageSize) {this.pageSize = pageSize;}public int getMemoryPageLimit() {return memoryPageLimit;}public void setMemoryPageLimit(int memoryPageLimit) {this.memoryPageLimit = memoryPageLimit;}public int getMemoryTotalPages() {return memoryTotalPages;}public void setMemoryTotalPages(int memoryTotalPages) {this.memoryTotalPages = memoryTotalPages;}public int getNextPage() {return nextPage;}public void setNextPage(int nextPage) {this.nextPage = nextPage;}public int getPreviousPage() {return previousPage;}public void setPreviousPage(int previousPage) {this.previousPage = previousPage;}public int getTotalCount() {return totalCount;}public void setTotalCount(int totalCount) {this.totalCount = totalCount;}public int getTotalPages() {return totalPages;}public void setTotalPages(int totalPages) {this.totalPages = totalPages;}public int getCurrentPage() {return currentPage;}public void setCurrentPage(int currentPage) {this.currentPage = currentPage;}@Overridepublic String toString() {return "PageConstant [pageIndex=" + pageIndex + ", pageSize=" + pageSize + ", memoryPageLimit=" + memoryPageLimit+ ", memoryTotalPages=" + memoryTotalPages + ", nextPage=" + nextPage + ", previousPage=" + previousPage+ ", totalCount=" + totalCount + ", totalPages=" + totalPages + ", currentPage=" + currentPage + "]";}}2.测试类
import java.util.Iterator;
import java.util.List;
import org.apache.torque.Torque;
import com.ideal.server.InitServer;
import com.workingdogs.village.Record;public class Test {public static void main(String[] args) {InitServer.init();try {PageConstant pageConstant = new PageConstant();pageConstant.setPageSize(10);pageConstant.setMemoryPageLimit(1);boolean isWhile = true;List<Record> results = null;int index = 1;String countSql = "select count(1) from user where status = 'A'";String querySql = "select * from user where status = 'A'";String dbName = Torque.getDefaultDB();while (isWhile) {pageConstant.setPageIndex(index);if (1 == index) {results = TorqueQueryByPageUtils.getResultsWithSql(true, pageConstant, countSql, querySql, dbName);} else {results = TorqueQueryByPageUtils.getResultsWithSql(false, pageConstant, countSql, querySql, dbName);}if (null == results || results.size() <= 0) {isWhile = false;break;} else {Iterator<Record> it = results.iterator();while (it.hasNext()) {Record rc = (Record) it.next();//columnNameString name= rc.getValue("name").toString();String password= rc.getValue("password").toString();System.out.println(name+":"+password);}}index = index + 1;} } catch (Exception e) {e.printStackTrace();}}}这篇关于Apache Torque实现分页查询的文章就介绍到这儿，希望我们推荐的文章对编程师们有所帮助！
