- servlet代码
package com.dl.controller; import com.dl.entity.Student; import com.dl.service.StudentService; import com.dl.service.impl.StudentServiceImpl; import com.dl.utils.PageUtil; 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 java.io.IOException; import java.util.List; /** * @公司 DL19121630工作室 * @作者 代先生 * @日期 2021/1/12 -- 16:58 * @微信 D19121630L * @温馨提示：原创代码，翻版必究！如需代写，微信联系！ */ @WebServlet("/studentByPageServlet") public class StudentByPageServlet extends HttpServlet { @Override protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { doGet(req,resp); } @Override protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { //设置请求的编码 req.setCharacterEncoding("utf-8"); //设置响应的编码 resp.setContentType("text/html;charset=utf-8"); //获取前端请求的参数 String no = req.getParameter("pageNo"); //判断是否为空，如果为空，则，默认显示第一页 if (no == null){ no = "1"; } //将 no 转成int类型 int pageNo = Integer.parseInt(no); //定义每页显示的条数，这里规定每页显示3条数据 int pageSize = 3; //调用方法查询数据 -- 分页查询 StudentService studentService = new StudentServiceImpl(); List<Student> studentByPage = studentService.getStudentByPage(pageNo, pageSize); //计算总记录数 -- 因为这里的BaseDao里面封装的方法不全，所以这里间接的求取总记录数 List<Student> allStudents = studentService.getAll(); int size = allStudents.size(); //创建一个PageUtil对象 -- 目的是为了通过其获取分页的总数量。一共有多少页 PageUtil pageUtil = new PageUtil(); //设置总记录数 pageUtil.setDataCount(size); //设置每页显示的条数 pageUtil.setPageSize(pageSize); //通过上面的两步的设置我们可以通过PageUtil对象获得总页数 int pageCount = pageUtil.getPageCount(); //将pageCount存入到request域对象中 req.setAttribute("pageCount",pageCount); //将查询到的额分页的数据添加的request域对象中 req.setAttribute("students",studentByPage); //将当前的页码数也存到request域对象中 req.setAttribute("pageNo",pageNo); //转发到指定的页面 req.getRequestDispatcher("studentByPage.jsp").forward(req,resp); } } - studentDao代码
package com.dl.dao; import com.dl.entity.Student; import java.util.List; /** * @公司 DL19121630工作室 * @作者 代先生 * @日期 2021/1/12 -- 16:24 * @微信 D19121630L * @温馨提示：原创代码，翻版必究！如需代写，微信联系！ */ public interface StudentDao { /** * 查询所有学生信息 * @return */ public List<Student> selectAll(); /** * 分页查询 * @param pageNo 当前的页码数 * @param pageSize 每页显示的条数 * @return */ public List<Student> selectStudentByPage(int pageNo, int pageSize); } - studentDaoImpl代码
package com.dl.dao.impl; import com.dl.dao.StudentDao; import com.dl.entity.Student; import com.dl.utils.BaseDao; import java.lang.reflect.InvocationTargetException; import java.sql.SQLException; import java.util.List; /** * @公司 DL19121630工作室 * @作者 代先生 * @日期 2021/1/12 -- 16:24 * @微信 D19121630L * @温馨提示：原创代码，翻版必究！如需代写，微信联系！ */ public class StudentDaoImpl extends BaseDao implements StudentDao { @Override public List<Student> selectAll() { //定义sql语句 String sql = "select * from student"; //定义一个参数数组，类型Object Object[] objects ={}; try { List<Student> students = super.query(sql, objects, Student.class); return students; } catch (SQLException throwables) { throwables.printStackTrace(); } catch (NoSuchMethodException e) { e.printStackTrace(); } catch (IllegalAccessException e) { e.printStackTrace(); } catch (InvocationTargetException e) { e.printStackTrace(); } catch (InstantiationException e) { e.printStackTrace(); } return null; } @Override public List<Student> selectStudentByPage(int pageNo, int pageSize) { //定义sql语句 String sql = "select * from student limit ?,?"; //定义参数数组，类型Object。 Object[] objects ={(pageNo-1)*pageSize,pageSize}; //执行sql语句 try { List<Student> students = super.query(sql, objects, Student.class); return students; } catch (SQLException throwables) { throwables.printStackTrace(); } catch (NoSuchMethodException e) { e.printStackTrace(); } catch (IllegalAccessException e) { e.printStackTrace(); } catch (InvocationTargetException e) { e.printStackTrace(); } catch (InstantiationException e) { e.printStackTrace(); } return null; } } - student实体类
package com.dl.entity; /** * @公司 DL19121630工作室 * @作者 代先生 * @日期 2021/1/12 -- 16:19 * @微信 D19121630L * @温馨提示：原创代码，翻版必究！如需代写，微信联系！ */ public class Student { private int id; private String name; private int age; private String sex; public Student() { } public Student(int id, String name, int age, String sex) { this.id = id; this.name = name; this.age = age; this.sex = sex; } public int getId() { return id; } 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 getSex() { return sex; } public void setSex(String sex) { this.sex = sex; } @Override public String toString() { return "Student{" + "id=" + id + ", name='" + name + '\'' + ", age=" + age + ", sex='" + sex + '\'' + '}'; } } - studentService代码
package com.dl.service; import com.dl.entity.Student; import java.util.List; /** * @公司 DL19121630工作室 * @作者 代先生 * @日期 2021/1/12 -- 16:24 * @微信 D19121630L * @温馨提示：原创代码，翻版必究！如需代写，微信联系！ */ public interface StudentService { /** * 获取全部的学生信息 * @return */ public List<Student> getAll(); /** * 分页获取学生的信息 * @param pageNo * @param pageSize * @return */ public List<Student> getStudentByPage(int pageNo, int pageSize); } - studentServiceImpl代码
package com.dl.service.impl; import com.dl.dao.StudentDao; import com.dl.dao.impl.StudentDaoImpl; import com.dl.entity.Student; import com.dl.service.StudentService; import java.util.List; /** * @公司 DL19121630工作室 * @作者 代先生 * @日期 2021/1/12 -- 16:25 * @微信 D19121630L * @温馨提示：原创代码，翻版必究！如需代写，微信联系！ */ public class StudentServiceImpl implements StudentService { private StudentDao studentDao; @Override public List<Student> getAll() { studentDao = new StudentDaoImpl(); List<Student> students = studentDao.selectAll(); return students; } @Override public List<Student> getStudentByPage(int pageNo, int pageSize) { studentDao = new StudentDaoImpl(); List<Student> students = studentDao.selectStudentByPage(pageNo, pageSize); return students; } } - BaseDao代码
package com.dl.utils; import org.apache.commons.beanutils.BeanUtils; import java.lang.reflect.InvocationTargetException; import java.sql.*; import java.util.ArrayList; import java.util.List; /** * 这个类是对数据库进行增删改查的 */ public class BaseDao { /** * 统一的修改方法，处理增删改的 * @param sql 需要执行的sql语句 * @param parameters 对应的sql语句的参数，现在弄成数组了 * @return */ public int update(String sql, Object[] parameters) throws SQLException{ if (sql == null) { throw new SQLException("sql is null"); } //1.获取数据库的连接 Connection connection = JdbcUtil.getConnection(); //2.使用对应的sql获取对应预处理的搬运工 PreparedStatement preparedStatement = connection.prepareStatement(sql); //3.开始处理参数Object[] obj = new Object[]{"宝强", 12, "经纪人"}; // String sql = "insert into work (name, age, info) values (?, ?, ?)"; //获取是参数的个数 int parameterCount = preparedStatement.getParameterMetaData().getParameterCount();//3 //4.使用预处理的搬运工对象对咱们的sql语句进行赋值操作 if (parameters != null && parameters.length == parameterCount) { for (int i = 1; i <= parameterCount; i++) { preparedStatement.setObject(i, parameters[i -1]); } } //5执行了sql语句 int i = preparedStatement.executeUpdate(); //6.关闭资源 JdbcUtil.close(connection, preparedStatement); return i; } /** * * @param sql * @param parameters * @param cls 这个参数需要带泛型，来约束当前方法中使用的泛型 * 这个参数还提供了一个非常重要的信息，指定查询数据的类的对象 * @param <T> * @return */ public <T> List<T> query(String sql, Object[] parameters, Class<T> cls) throws SQLException, NoSuchMethodException, IllegalAccessException, InvocationTargetException, InstantiationException { if (sql == null || cls == null) { throw new NullPointerException(); } //1.获取数据库连接对象 Connection connection = JdbcUtil.getConnection(); //2.使用sql预处理的搬运工 PreparedStatement preparedStatement = connection.prepareStatement(sql); //3.参数的处理，借助于参数元数据 int parameterCount = preparedStatement.getParameterMetaData().getParameterCount(); //4.对sql里面的？进行赋值 if (parameters != null && parameters.length == parameterCount) { for (int i = 1; i <= parameterCount; i++) { preparedStatement.setObject(i, parameters[i - 1]); } } //5.执行查询的sql ResultSet resultSet = preparedStatement.executeQuery(); //6.准备List集合 List<T> list = new ArrayList<>(); //7.获取结果集元数据 ResultSetMetaData metaData = resultSet.getMetaData(); //8.获取字段的个数 int columnCount = metaData.getColumnCount(); //9.遍历 while (resultSet.next()) { //10创建类对象（来接数据查询出来的数据）Work work = new Work() T t = cls.getConstructor(null).newInstance(null); for (int i = 1; i <= columnCount; i++) { //12.获取字段的名字 String columnName = metaData.getColumnName(i);//id, name ,age //13.获取对应字段的数据 Object value = resultSet.getObject(columnName); //14.使用BeanUtils给指定字段的数据在类对象中给赋值 BeanUtils.setProperty(t, columnName, value); } //15.存到list集合中 list.add(t); } JdbcUtil.close(connection, preparedStatement, resultSet); //如果list不为空，就返回list， 如果为空就返回null return list.size() != 0 ? list : null; } }
- jdbcUtil代码
package com.dl.utils; import com.mchange.v2.c3p0.ComboPooledDataSource; import java.io.FileInputStream; import java.io.FileNotFoundException; import java.io.IOException; import java.sql.*; import java.util.Properties; /** * 工具类能干嘛？ * 1.自动完成驱动的加载 * 2.自动完成必要的数据处理 * 3.简化getConnection方法，提供给开发者 * 4.完成统一的close方法 */ public class JdbcUtil { //c3p0的连接池对象，就会加载默认的xml配置文件，配置文件必须写成固定能够c3p0-config.xml //存放的目录必须是srcx下面 private static ComboPooledDataSource pool = new ComboPooledDataSource(); public static Connection getConnection () { Connection connection = null; try { //connection = DriverManager.getConnection(url, user, password); connection = pool.getConnection(); } catch (SQLException e) { e.printStackTrace(); } return connection; } /** * 关闭数据库连接对象 */ //假如statement 是null resultSet是null public static void close(Connection connection) { try { close(connection, null, null); } catch (SQLException e) { e.printStackTrace(); } } //resultSet是null public static void close(Connection connection, Statement statement) { try { close(connection, statement, null); } catch (SQLException e) { e.printStackTrace(); } } public static void close(Connection connection, Statement statement, ResultSet resultSet) throws SQLException { if (connection != null) { try { connection.close(); } catch (SQLException e) { e.printStackTrace(); } } if (statement != null) { try { statement.close(); } catch (SQLException e) { e.printStackTrace(); } } if (resultSet != null) { resultSet.close(); } } }
- PageUtil代码
package com.dl.utils; /** * @公司 DL19121630工作室 * @作者 代先生 * @日期 2021/1/12 -- 16:47 * @微信 D19121630L * @温馨提示：原创代码，翻版必究！如需代写，微信联系！ */ public class PageUtil { private int pageNo; private int pageSize; private int pageCount; private int dataCount; public PageUtil(int pageNo, int pageSize, int pageCount, int dataCount) { this.pageNo = pageNo; this.pageSize = pageSize; this.pageCount = pageCount; this.dataCount = dataCount; } public PageUtil() { } public int getPageNo() { return pageNo; } public void setPageNo(int pageNo) { this.pageNo = pageNo; } public int getPageSize() { return pageSize; } public void setPageSize(int pageSize) { this.pageSize = pageSize; } public int getPageCount() { if (dataCount % pageSize ==0){ pageCount = dataCount / pageSize; }else { pageCount = dataCount / pageSize + 1; } return pageCount; } public void setPageCount(int pageCount) { this.pageCount = pageCount; } public int getDataCount() { return dataCount; } public void setDataCount(int dataCount) { this.dataCount = dataCount; } } - index.jsp代码
<%-- Created by IntelliJ IDEA. User: 87421 Date: 2021/1/12 Time: 12:43 To change this template use File | Settings | File Templates. --%> <%@ page contentType="text/html;charset=UTF-8" language="java" %> <html> <head> <title>$Title$</title> </head> <body> <a href="${pageContext.request.contextPath}/studentByPageServlet">分页效果</a> <br> <a href="${pageContext.request.contextPath}/studentServlet">不分页的效果</a> </body> </html> - student.jsp代码
<%-- Created by IntelliJ IDEA. User: 87421 Date: 2021/1/12 Time: 16:39 To change this template use File | Settings | File Templates. --%> <%@ page contentType="text/html;charset=UTF-8" language="java" %> <%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %> <html> <head> <title>Title</title> </head> <body> <table border="1"> <tr> <th>编号</th> <th>姓名</th> <th>年龄</th> <th>性别</th> </tr> <c:forEach var="student" items="${students}"> <tr> <td>${student.id}</td> <td>${student.name}</td> <td>${student.age}</td> <td>${student.sex}</td> </tr> </c:forEach> </table> <br> <br> <br> <a href="${pageContext.request.contextPath}/studentByPageServlet">分页效果</a> </body> </html> - studentByPage.jsp代码
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %> <%-- Created by IntelliJ IDEA. User: 87421 Date: 2021/1/12 Time: 16:59 To change this template use File | Settings | File Templates. --%> <%@ page contentType="text/html;charset=UTF-8" language="java" %> <html> <head> <title>Title</title> </head> <body> <table border="1"> <tr> <th>编号</th> <th>姓名</th> <th>年龄</th> <th>性别</th> </tr> <c:forEach var="student" items="${students}"> <tr> <td>${student.id}</td> <td>${student.name}</td> <td>${student.age}</td> <td>${student.sex}</td> </tr> </c:forEach> <tr> <td colspan="4"> <a href="${pageContext.request.contextPath}/studentByPageServlet?pageNo=1">首页</a> <c:if test="${pageNo==1}"> <a>上一页</a> </c:if> <c:if test="${pageNo>1}"> <a href="${pageContext.request.contextPath}/studentByPageServlet?pageNo=${pageNo-1}">上一页</a> </c:if> <c:if test="${pageNo==pageCount}"> <a>下一页</a> </c:if> <c:if test="${pageNo<pageCount}"> <a href="${pageContext.request.contextPath}/studentByPageServlet?pageNo=${pageNo+1}">下一页</a> </c:if> <a href="${pageContext.request.contextPath}/studentByPageServlet?pageNo=${pageCount}">尾页</a> </td> </tr> </table> <br> <br> <br> <a href="${pageContext.request.contextPath}/studentServlet">不分页的效果</a> </body> </html> - 项目截图
- 项目所用jar包
- 运行截图
基于jsp的原生分页查询。
猜你喜欢
转载自blog.csdn.net/weixin_45634682/article/details/112540437
今日推荐
周排行