⼀个简单的javaweb项⽬模板Controller包：表现层（视图）层。
⽤来显⽰数据和接收⽤户数据Service包：业务逻辑层，⽤来处理页⾯。
先写接⼝，后写实现类Dao包：持久层（数据访问层）。
⽤来操作数据库其中Dao包处于最底层，对于⽤户处于隐藏状态，对于开发者处于固定状态，其中包括Con_CloseSql类（数据库连接与关闭）、UserDao 类（进⾏增删改查）与UserBeans（数据库数据）Con_CloseSql类：package dao;import java.sql.*;public class Con_CloseSql {final String JDBC_DRIVER = "com.mysql.cj.jdbc.Driver";final String DB_URL = "jdbc:mysql://localhost:3306/表名?serverTimezone=GMT&characterEncoding=utf-8&useSSL=false";final String USER = "root";final String PASS = "密码";Statement stmt = null;public Connection getConnect(){Connection conn = null;try{Class.forName(JDBC_DRIVER);String url = DB_URL;conn = DriverManager.getConnection(url, USER, PASS);return conn;}catch(ClassNotFoundException nfe) {nfe.printStackTrace();}catch(SQLException e) {e.printStackTrace();}return conn;}public static void closeConnection(Connection connection) {if(connection != null) {try{connection.close();}catch(SQLException sqle) {sqle.printStackTrace();}}}}UserDao类：package dao;import erBean;import java.sql.*;import java.util.ArrayList;import java.util.List;public class UserDao { //保存⽤户数据public void saveUser(UserBean userBean) throws SQLException {Connection connect = new Con_CloseSql().getConnect();Statement statement = connect.createStatement();String sql = "insert into 表名 values (?,?,?,?,?,?,?,?,?)";try {PreparedStatement pr = connect.prepareStatement(sql);pr.setString(1, userBean.getHutype());pr.setString(2, userBean.getHousetype());pr.setString(3, userBean.getArea());pr.setString(4, userBean.getNum());pr.setString(5, userBean.getName());pr.setString(6, userBean.getId());pr.setString(7, userBean.getSex());pr.setString(8, userBean.getNation());pr.setString(9, userBean.getEducation());pr.execute();} catch (Exception e) {e.printStackTrace();} finally {Con_CloseSql.closeConnection(connect);}} //通过name删除该⾏public void deleteUser(UserBean userBean) {Connection connect = new Con_CloseSql().getConnect();String sql = "delete from 表名 where name=? ";try {PreparedStatement pr = connect.prepareStatement(sql);pr.setString(1, userBean.getName());pr.executeUpdate();} catch (SQLException throwables) {throwables.printStackTrace();}} //查询数据库中消息并从前端输出表格public List<UserBean> query() {Connection connect = new Con_CloseSql().getConnect();String sql = "select * from 表名";List<UserBean> userBeans = new ArrayList<>();try {try (PreparedStatement ps = connect.prepareStatement(sql)) { ResultSet resultSet = ps.executeQuery(sql);UserBean userBean = null;while (resultSet.next()) {String hutype = resultSet.getString("...");String housetype = resultSet.getString("...");String area = resultSet.getString("...");//表头关键字userBean = new UserBean(..., ..., ...,...);//表中元素userBeans.add(userBean);}}} catch (SQLException e) {// TODO Auto-generated catch blocke.printStackTrace();} finally {Con_CloseSql.closeConnection(connect);}return userBeans;} //通过名字来展⽰信息public UserBean queryByName(String name) {Connection connect = new Con_CloseSql().getConnect();String sql = "select * from census where 户主姓名 = '"+name+"' "; UserBean userBean = null;//Object[] params = {name};try {try (PreparedStatement ps = connect.prepareStatement(sql)) { ResultSet resultSet = ps.executeQuery(sql);if (resultSet.next()) {String hutype = resultSet.getString("户别");String housetype = resultSet.getString("住房类型");String area = resultSet.getString("本户现住房⾯积");String num = resultSet.getString("本户现住房间数");String name1 = resultSet.getString("户主姓名");String id = resultSet.getString("⾝份证号码");String sex = resultSet.getString("性别");String nation = resultSet.getString("民族");String education = resultSet.getString("受教育程度");userBean = new UserBean(hutype, housetype, area, num, name1, id, sex, nation, education); }}} catch (SQLException e) {// TODO Auto-generated catch blocke.printStackTrace();} finally {Con_CloseSql.closeConnection(connect);}return userBean;} //通过名字更新其他信息public void upDate(UserBean user){Connection connect = new Con_CloseSql().getConnect();String sql="update census set ⾝份证号码=?,性别=?,民族=?,受教育程度=? where 户主姓名=?";try {PreparedStatement ps = connect.prepareStatement(sql);ps.setString(1, user.getId());ps.setString(2, user.getSex());ps.setString(3,user.getNation());ps.setString(4,user.getEducation());ps.setString(5,user.getName());int i= ps.executeUpdate();} catch (SQLException e) {// TODO Auto-generated catch blocke.printStackTrace();}finally{Con_CloseSql.closeConnection(connect);}} //判断是否为该⽤户public boolean isUser(String name) {Connection connect = new Con_CloseSql().getConnect();try {String sql = "select * from census where 户主姓名 = '" + name + "'";// 执⾏查询语句，并把结果集返回给ResultSetPreparedStatement pr = connect.prepareStatement(sql);ResultSet rs = pr.executeQuery();if (rs.next())return true;elsereturn false;} catch (SQLException e) {// TODO Auto-generated catch blockreturn false;}}public ArrayList<String> findDate() {Connection conn = new Con_CloseSql().getConnect();String sql = "select * from census";PreparedStatement pr;try {pr = (PreparedStatement)conn.prepareStatement(sql);ResultSet rs = pr.executeQuery();int col = rs.getMetaData().getColumnCount();ArrayList<String> m = new ArrayList<String>();int n = 0;while (rs.next()) {for (int i = 1; i <= col; i++) {m.add(rs.getString(i) + "<br>");System.out.print(rs.getString(i) + "\t");if ((i == 2) && (rs.getString(i).length() < 8)) {m.add("<br>");}}System.out.println("");}return m;} catch (SQLException e) {e.printStackTrace();}return null;}}Service包主要包括各种servletXXXServlet类：package service;import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import java.io.IOException;public class XXXServlet extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { req.setCharacterEncoding("utf-8");resp.setCharacterEncoding("utf-8");resp.setContentType("text/html;utf-8");}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { doGet(req, resp);}}pom.xml常⽤配置为：<dependency><groupId>javax.servlet</groupId><artifactId>servlet-api</artifactId><version>2.5</version></dependency><dependency><groupId>javax.servlet.jsp</groupId><artifactId>javax.servlet.jsp-api</artifactId><version>2.3.3</version></dependency><dependency><groupId>mysql</groupId><artifactId>mysql-connector-java</artifactId><version>8.0.13</version></dependency><!-- https:///artifact/javax.servlet/jstl --><dependency><groupId>javax.servlet</groupId><artifactId>jstl</artifactId><version>1.2</version></dependency><!-- https:///artifact/taglibs/standard --><dependency><groupId>taglibs</groupId><artifactId>standard</artifactId><version>1.1.2</version></dependency>web.xml为：<?xml version="1.0" encoding="UTF-8"?><web-app xmlns="/xml/ns/javaee"xmlns:xsi="/2001/XMLSchema-instance"xsi:schemaLocation="/xml/ns/javaee/xml/ns/javaee/web-app_4_0.xsd"version="4.0"metadata-complete="true"><welcome-file-list><welcome-file>index.html</welcome-file></welcome-file-list></web-app>jsp基础配置为：<%@ page contentType="text/html;charset=UTF-8" language="java" %> <%@taglib prefix="c" uri="/jsp/jstl/core" %><html><head><title>Title</title></head><body></body></html>。
