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 bean.UserBean;
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 block
            e.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 block
            e.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 block
            e.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ResultSet
            PreparedStatement pr = connect.prepareStatement(sql);
            ResultSet rs = pr.executeQuery();
            if (rs.next())
                return true;
            else
                return false;

        } catch (SQLException e) {
            // TODO Auto-generated catch block
            return 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servlet

XXXServlet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 {

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

        req.setCharacterEncoding("utf-8");
        resp.setCharacterEncoding("utf-8");
        resp.setContentType("text/html;utf-8");

    }

    @Override
    protected 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://mvnrepository.com/artifact/javax.servlet/jstl -->
    <dependency>
      <groupId>javax.servlet</groupId>
      <artifactId>jstl</artifactId>
      <version>1.2</version>
    </dependency>

    <!-- https://mvnrepository.com/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="http://xmlns.jcp.org/xml/ns/javaee"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee
                      http://xmlns.jcp.org/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="http://java.sun.com/jsp/jstl/core" %>
<html>
<head>
    <title>Title</title>
</head>
<body>

</body>
</html>