Servlet简单分页

本文是参照易百教程上的例子，觉得很有收藏价值，于是特记录一份

数据库示例数据：

DROP TABLE IF EXISTS `employees`;
CREATE TABLE `employees` (
  `id` int(10) unsigned NOT NULL AUTO_INCREMENT,
  `name` varchar(64) NOT NULL DEFAULT '',
  `age` int(3) unsigned NOT NULL DEFAULT '0',
  `education` varchar(32) DEFAULT '' COMMENT '学历',
  `address` varchar(254) DEFAULT NULL,
  `salary` float(8,2) unsigned DEFAULT NULL,
  PRIMARY KEY (`id`)
) ENGINE=MyISAM AUTO_INCREMENT=11 DEFAULT CHARSET=utf8;

SELECT * FROM employees;
-- ----------------------------
-- Records of employees
-- ----------------------------
INSERT INTO `employees` VALUES ('1', '李小春', '23', '其它', '海口市人民大道1800号', '8900.00');
INSERT INTO `employees` VALUES ('2', '张辉', '28', '本科', '广州天河区珠村市场', '15800.98');
INSERT INTO `employees` VALUES ('3', '林贤弟', '29', '博士', '广州白云区龙塘村120号', '18990.99');
INSERT INTO `employees` VALUES ('4', '王小简', '23', '本科', '海口人民大道1688号', '899.98');
INSERT INTO `employees` VALUES ('5', '蔡世杰', '27', '专科', '上海市宝山区联杨路2211弄26号', '15800.00');
INSERT INTO `employees` VALUES ('6', '张承龙', '30', '本科', '上海市虹口区虬江路522号', '23000.00');
INSERT INTO `employees` VALUES ('7', '李林奕', '26', '本科', '上海市徐汇区漕宝路440号', '32600.00');
INSERT INTO `employees` VALUES ('8', '刘皓轩', '28', '研究生', '上海松江九亭立同商务广场', '29000.00');
INSERT INTO `employees` VALUES ('9', '周佳豪', '36', '博士', '深圳市宝安区沙井街道办107国道富达工业区B栋', '48000.00');
INSERT INTO `employees` VALUES ('10', '陈聪', '23', '本科', '福田区文蔚大厦19层', '9800.00');

paging.html：

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Servlet分页示例</title>
</head>
<body>
    <div style="text-align: center;">
        <a href="PagingServlet">点击查看分页效果</a>
    </div>
</body>
</html>

Employees.java：

public class Employees {
	private int id;
	private String name;
	private int age;
	private String address;
	private String education;
	private float salary;

	public int getId() {
		return id;
	}

	public String getEducation() {
		return education;
	}

	public void setEducation(String education) {
		this.education = education;
	}

	public void setId(int id) {
		this.id = id;
	}

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

	public int getAge() {
		return age;
	}

	public void setAge(int age) {
		this.age = age;
	}

	public String getAddress() {
		return address;
	}

	public void setAddress(String address) {
		this.address = address;
	}

	public float getSalary() {
		return salary;
	}

	public void setSalary(float salary) {
		this.salary = salary;
	}

}

EmpDao.java：

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;

import com.hthk.login.bean.Employees;

public class EmpDao {
	public static Connection getConnection() {
		Connection con = null;
		try {
			Class.forName("com.mysql.jdbc.Driver");
			con = DriverManager.getConnection("jdbc:mysql://localhost/mydb?useSSL=false&characterEncoding=utf8", "root",
					"520520t");
		} catch (ClassNotFoundException e) {
			e.printStackTrace();
		} catch (SQLException e) {
			e.printStackTrace();
		}
		return con;
	}

	public static int totalPages(int pageSize) {
		int total = getTotal();
		int totalPages = (total % pageSize == 0) ? (total / pageSize) : (total / pageSize) + 1;
		return totalPages;
	}

	private static int getTotal() {
		try {
			Connection con = getConnection();
			PreparedStatement ps = con.prepareStatement("SELECT COUNT(1) AS total FROM EMPLOYEES");
			ResultSet rs = ps.executeQuery();
			while (rs.next()) {
				return rs.getInt("total");
			}

		} catch (Exception e) {
			e.printStackTrace();
		}
		return 0;
	}

	public static List<Employees> getRecords(int currentPage, int pageSize) {
		List<Employees> list = new ArrayList<Employees>();
		int start = 0;
		if (currentPage > 0) {
			start = (currentPage - 1) * pageSize;
		}

		try {
			Connection con = getConnection();
			String sql = "SELECT * FROM EMPLOYEES ORDER BY ID LIMIT " + start + "," + pageSize;
			PreparedStatement ps = con.prepareStatement(sql);
			ResultSet rs = ps.executeQuery();
			while (rs.next()) {
				Employees e = new Employees();
				e.setId(rs.getInt(1));
				e.setName(rs.getString(2));
				e.setSalary(rs.getFloat("salary"));
				list.add(e);
			}
			con.close();

		} catch (Exception e) {
			e.printStackTrace();
		}
		return list;
	}

}

PagingServlet.java：

import java.io.IOException;
import java.io.PrintWriter;
import java.util.List;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.hthk.login.bean.Employees;
import com.hthk.login.dao.EmpDao;

@WebServlet("/PagingServlet")
public class PagingServlet extends HttpServlet {

	private static final long serialVersionUID = 1L;

	@Override
	protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
		resp.setCharacterEncoding("UTF-8");
		resp.setContentType("text/html;charset=utf-8");
		req.setCharacterEncoding("UTF-8");
		PrintWriter out = resp.getWriter();
		// 每页3条记录
		int pageSize = 3;
		String spage = req.getParameter("page");
		if (spage == null || spage == "") {
			spage = "1";
		}
		int currentPage = Integer.parseInt(spage);
		int totalPage = EmpDao.totalPages(pageSize);

		List<Employees> list = EmpDao.getRecords(currentPage, pageSize);
		
		out.print("<h1>当前第: " + spage + "/" + totalPage + " 页</h1>");
		out.print("<table border='1' cellpadding='4' width='60%'>");
		out.print("<tr><th>编号</th><th>姓名</th><th>薪水</th>");
		for (Employees e : list) {
			out.print("<tr><td>" + e.getId() + "</td><td>" + e.getName() + "</td><td>" + e.getSalary() + "</td></tr>");
		}
		out.print("</table>");

		out.print("<a href='PagingServlet?page=1'>首页</a> ");
		for (int i = 1; i <= totalPage; i++) {
			out.print("<a href='PagingServlet?page=" + i + "'>" + i + "</a> ");
		}
		out.print("<a href='PagingServlet?page=" + totalPage + "'>最后一页</a> ");
		out.close();
	}

}

运行页面展示：

第1，2，3，4页所执行的SQL语句分别如下：

SELECT * FROM employees ORDER BY id LIMIT 0,3
SELECT * FROM employees ORDER BY id LIMIT 3,3
SELECT * FROM employees ORDER BY id LIMIT 6,3
SELECT * FROM employees ORDER BY id LIMIT 9,3

注意：

这里不用配置web.xml，使用的是：

@WebServlet("/PagingServlet")

如果使用这个注解，应该在tomcat7以上版本中部署运行，tomcat7之前的版本是不支持注解的。 @WebServlet注释用于将servlet映射到指定的名称，这是Servlet3的特性，所以在创建项目时要指定Servlet的版本为3.0以上。

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