JavaWeb分页展示数据（含AJAX/JSTL/EL表达式等知识点）

package com.csdn.selma003.dao.impl; import java.sql.Connection; import java.sql.PreparedStatement; import java.sql.ResultSet; import java.util.ArrayList; import java.util.List; import com.csdn.selma003.dao.ProblemDao; import com.csdn.selma003.db.DBHelper; import com.csdn.selma003.pojo.Problem; import net.sf.json.JSONArray; public class ProblemDaoImpl implements ProblemDao { @Override public List<Problem> queryProblemByPageSplit(int pageNum, int pageSize) { List<Problem> list = new ArrayList<Problem>(); //sql:SELECT * FROM problem LIMIT ?, ? //LIMIT语法：从某个数 + 1开始， 找多少条记录 //所以当第pageNum页时，第一个?填(pageNum - 1) * pageSize，第二个?填pageSize Connection connection = DBHelper.getConnection(); String sql = "SELECT * FROM problem LIMIT ?, ?"; try { PreparedStatement preStatement = connection.prepareStatement(sql); preStatement.setInt(1, (pageNum - 1) * pageSize); preStatement.setInt(2, pageSize); ResultSet resultSet = preStatement.executeQuery(); while(resultSet.next()) { Problem problem = new Problem(); problem.setProblemId(resultSet.getInt("problem_id")); problem.setProblemName(resultSet.getString("problem_name")); problem.setProblemDifficulty(resultSet.getString("problem_difficulty")); problem.setProblemPassPercent(resultSet.getString("problem_pass_percent")); list.add(problem); } }catch (Exception e) { e.printStackTrace(); }finally { DBHelper.closeConnection(connection); } return list; } @Override public int getMaxPage(int pageSize) { Connection connection = DBHelper.getConnection(); String sql = "SELECT COUNT(*) FROM problem"; int totalNum = 0; try { PreparedStatement preStatement = connection.prepareStatement(sql); ResultSet resultSet = preStatement.executeQuery(); if(resultSet.next()) { totalNum = resultSet.getInt("COUNT(*)"); } }catch (Exception e) { e.printStackTrace(); }finally { DBHelper.closeConnection(connection); } //巧技：(totalNum - 1) / (pageSize + 1) return totalNum % pageSize == 0 ? totalNum / pageSize : totalNum / pageSize + 1; } public String listToJson(List<Problem> list) { return JSONArray.fromObject(list).toString(); } }