java基础笔记（9）

通过JDBC像数据库实现CRUD操作，这里通过一个存储查看人员的案例来了解java是如何通过JDBC实现与数据库的连接，三层结构中的模型层（数据访问），控制层（业务逻辑）、以及视图层（表示层）又是怎么进行一个交互实现业务需求的。

模型层：

package com.jdbc;

import java.util.Date;

public class laoren {
    private Integer id;
    private String username;
    private Integer sex;
    private Integer age;
    private String hobby;
    private String create_user;
    private Date create_date;
    private String update_user;
    private Date update_date;
    public Integer getId() {
        return id;
    }
    public void setId(Integer id) {
        this.id = id;
    }
    public String getUsername() {
        return username;
    }
    public void setUsername(String username) {
        this.username = username;
    }
    public Integer getSex() {
        return sex;
    }
    public void setSex(Integer sex) {
        this.sex = sex;
    }
    public Integer getAge() {
        return age;
    }
    public void setAge(Integer age) {
        this.age = age;
    }
    public String getHobby() {
        return hobby;
    }
    public void setHobby(String hobby) {
        this.hobby = hobby;
    }
    public String getCreate_user() {
        return create_user;
    }
    public void setCreate_user(String create_user) {
        this.create_user = create_user;
    }
    public Date getCreate_date() {
        return create_date;
    }
    public void setCreate_date(Date create_date) {
        this.create_date = create_date;
    }
    public String getUpdate_user() {
        return update_user;
    }
    public void setUpdate_user(String update_user) {
        this.update_user = update_user;
    }
    public Date getUpdate_date() {
        return update_date;
    }
    public void setUpdate_date(Date update_date) {
        this.update_date = update_date;
    }
    @Override
    public String toString() {
        return "laoren [id=" + id + ", username=" + username + ", sex=" + sex + ", age=" + age + ", hobby=" + hobby
                + ", create_user=" + create_user + ", create_date=" + create_date + ", update_user=" + update_user
                + ", update_date=" + update_date + "]";
    }

}

模型实现增删查改：

package com.jdbc;

import java.sql.Connection;
import java.sql.Date;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ArrayList;

import java.util.List;

import com.jdbc.DBUtil;

public class laorenDao {
    public void addLaoren(laoren l) throws SQLException {
        Connection conn = DBUtil.getConnection();
        String sql = "insert into laoren "+"(username,sex,age,hobby,create_user,create_date,update_user,update_date)"+
                      "values(?,?,?,?,?,current_date(),?,current_date())";
        PreparedStatement ptmt = conn.prepareStatement(sql);
        ptmt.setString(1, l.getUsername());
        ptmt.setLong(2, l.getSex());
        ptmt.setLong(3, l.getAge());
        ptmt.setString(4, l.getHobby());
        ptmt.setString(5, l.getCreate_user());
        ptmt.setString(6, l.getUpdate_user());
        ptmt.execute();
    }
    public void delLaoren(Integer id) throws SQLException {
        Connection conn = DBUtil.getConnection();
        String sql = "delete from laoren "+
        " where id = ?";
        PreparedStatement ptmt = conn.prepareStatement(sql);
        ptmt.setLong(1, id);
        ptmt.execute();
    }
    public List<laoren> query() throws SQLException{
        Connection conn = DBUtil.getConnection();
        Statement stmt = conn.createStatement();
        ResultSet rs = stmt.executeQuery("select * from laoren");
        List<laoren> lr = new ArrayList<laoren>();
        laoren l = null;
        while(rs.next()){
            l = new laoren();
            l.setUsername(rs.getString("username"));
            l.setId(rs.getInt("id"));
            l.setAge(rs.getInt("age"));
            l.setHobby(rs.getString("hobby"));
            l.setCreate_user(rs.getString("create_user"));
            l.setCreate_date(rs.getDate("create_date"));
            l.setUpdate_user(rs.getString("update_user"));
            l.setUpdate_date(rs.getDate("update_date"));
            lr.add(l);

        }
        return lr;
    }
    public laoren getlaoren(Integer id) throws SQLException {
        laoren l = null;
        Connection conn = DBUtil.getConnection();
        String sql = "select * from laoren"+
        " where id = ?";
        PreparedStatement ptmt = conn.prepareStatement(sql);
        ptmt.setLong(1, id);
        ResultSet rs = ptmt.executeQuery();
        while(rs.next()) {
            l = new laoren();
            l.setId(rs.getInt("id"));
            l.setUsername(rs.getString("username"));
            l.setAge(rs.getInt("age"));
            l.setHobby(rs.getString("hobby"));
            l.setCreate_user(rs.getString("create_user"));
            l.setCreate_date(rs.getDate("create_date"));
            l.setUpdate_user(rs.getString("update_user"));
            l.setUpdate_date(rs.getDate("update_date"));
        }
        return l;
    }
    public laoren getlaoren(String username) throws SQLException {
        laoren l = null;
        Connection conn = DBUtil.getConnection();
        String sql = "select * from laoren"+
        " where username = ?";
        PreparedStatement ptmt = conn.prepareStatement(sql);
        ptmt.setString(1, username);
        ResultSet rs = ptmt.executeQuery();
        while(rs.next()) {
            l = new laoren();
            l.setId(rs.getInt("id"));
            l.setUsername(rs.getString("username"));
            l.setAge(rs.getInt("age"));
            l.setHobby(rs.getString("hobby"));
            l.setCreate_user(rs.getString("create_user"));
            l.setCreate_date(rs.getDate("create_date"));
            l.setUpdate_user(rs.getString("update_user"));
            l.setUpdate_date(rs.getDate("update_date"));
        }
        return l;
    }
    public void updateLaoren(laoren l) throws SQLException {
        Connection conn = DBUtil.getConnection();
        String sql = "update laoren "+" set username=?,sex=?,age=?,hobby=?,update_user=?,update_date=current_date()"+
        " where id = ?";
        PreparedStatement ptmt = conn.prepareStatement(sql);
        ptmt.setString(1, l.getUsername());
        ptmt.setLong(2, l.getSex());
        ptmt.setLong(3, l.getAge());
        ptmt.setString(4, l.getHobby());
        ptmt.setString(5, l.getUpdate_user());
        ptmt.setLong(6, l.getId());
        ptmt.execute();
    }
}

注：这里的数据库连接通过一个自定好的数据库工具类来实现：

package com.jdbc;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

public class DBUtil {
    private static final String URL="jdbc:mysql://127.0.0.1:3306/laoguai?useUnicode=true&characterEncoding=utf8";//useUnicode表示允许使用自定义的Unicode,characterEncoding是给定自定义的Unicode是什么
    private static final String user="root";
    private static final String password="123456";
    private static Connection conn = null;
    static {
        try {
            Class.forName("com.mysql.jdbc.Driver");//加载驱动程序
            conn = DriverManager.getConnection(URL, user, password);//获得数据库的连接
        } catch (ClassNotFoundException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
    public static Connection getConnection() {
        return conn;
    }

}

控制层：

package com.jdbc;
import java.sql.SQLException;
import java.util.List;

import com.jdbc.*;
public class laorenCon {
    public void add(laoren lr) throws SQLException{
        laorenDao dao = new laorenDao();
        dao.addLaoren(lr);
    }
    public void deit(laoren lr) throws SQLException{
        laorenDao dao = new laorenDao();
        dao.updateLaoren(lr);
    }
    public void del(Integer id) throws SQLException{
        laorenDao dao = new laorenDao();
        dao.delLaoren(id);
    }
    public void read(Integer id) throws SQLException{
        laorenDao dao = new laorenDao();
        System.out.println(dao.getlaoren(id).toString());

    }
    public void read(String name) throws SQLException{
        laorenDao dao = new laorenDao();
        laoren y = dao.getlaoren(name);
        System.out.println(y.toString());
    }
    public void readall() throws SQLException{
        laorenDao dao = new laorenDao();
        List<laoren> list = dao.query();
        for(laoren y:list) {
            System.out.println(y.toString());
        }

    }

}

视图层；

package com.jdbc;

import java.sql.SQLException;
import java.util.Scanner;
import java.util.regex.Pattern;

public class view {
    private static final String CONTEXT = "欢迎来到功能选择区: \n"+
            "下面是功能列表: \n"+
            "[MAIN/M]:主菜单 \n"+
            "[QUERY/Q]:查看捞人的全部信息 \n"+
            "[GET/G]:查看某个捞人的信息（根据id或名字）\n"+
            "[ADD/A]添加某个捞人 \n"+
            "[UPDATE/U]:更新某个捞人的信息 \n"+
            "[DELETE/D]:删除某个捞人的信息 \n"+
            "[EXIT/E]:离开 \n"+
            "[BREAK/B]:后退，返回功能选择区";
    private static final String MAIN = "MAIN";
    private static final String QUERY = "QUERY";
    private static final String GET = "GET";
    private static final String ADD = "ADD";
    private static final String UPDATE = "UPDATE";
    private static final String DELETE = "DELETE";
    private static final String EXIT = "EXIT";
    public static void main(String[] args) throws SQLException {
        System.out.println(CONTEXT);
        Scanner scan = new Scanner(System.in);
        laoren lr =new laoren();
        laorenCon lc = new laorenCon();
        String pren = null;
        Integer step = 1;
        while(scan.hasNext()) {
            String in = scan.next().toString();
            if(EXIT.equals(in.toUpperCase())||EXIT.substring(0, 1).equals(in.toUpperCase())) {
                System.out.println("您已退出系统");
                break;
            }else if(QUERY.equals(in.toUpperCase())||QUERY.substring(0, 1).equals(in.toUpperCase())) {
                lc.readall();
            }else if(MAIN.equals(in.toUpperCase())||MAIN.substring(0, 1).equals(in.toUpperCase())) {
                System.out.println(CONTEXT);
                pren = null;
                step = 1;

            }else if(GET.equals(in.toUpperCase())||GET.substring(0, 1).equals(in.toUpperCase())||GET.equals(pren)) {
                //if(in.matches("\\d+"));
                pren = GET;
                if(step == 1) {

                    System.out.println("请输入要查询的捞人名字或ID：");
                }else if (step == 2) {
                    Pattern pattern = Pattern.compile("^[-\\+]?[\\d]*$");
                    if( pattern.matcher(in).matches())
                    lc.read(Integer.valueOf(in));
                    else {
                        lc.read(in);
                    }
                }
                if(GET.equals(pren)) {
                    step++;
                }
            }else if(DELETE.equals(in.toUpperCase())||DELETE.substring(0, 1).equals(in.toUpperCase())||DELETE.equals(pren)) {
                //if(in.matches("\\d+"));
                pren = DELETE;
                if(step == 1) {

                    System.out.println("请输入要删除的捞人的ID：");
                }else if (step == 2) {
                    lc.del(Integer.valueOf(in));

                }
                if(DELETE.equals(pren)) {
                    step++;
                }
            }else if(ADD.equals(in.toUpperCase())||ADD.substring(0, 1).equals(in.toUpperCase())||ADD.equals(pren)) {
                pren = ADD;
                if(step == 1) {
                    System.out.println("请输入新增捞人的姓名：");

                }else if(step == 2){
                    lr.setUsername(in);
                    System.out.println("请输入新增捞人的年龄：");
                }else if(step == 3) {
                    lr.setAge(Integer.valueOf(in));
                    System.out.println("请输入新增捞人的爱好：");
                }else if(step == 4) {
                    lr.setHobby(in);
                    System.out.println("请输入新增捞人的性别：");
                }else if(step == 5) {
                    lr.setSex(Integer.valueOf(in));
                    System.out.println("请问这个捞人的创建人是谁：");
                }else if(step == 6) {
                    lr.setCreate_user(in);
                    System.out.println("请问这个捞人的更新人是谁：");
                }else if(step == 7) {
                    lr.setUpdate_user(in);
                    try {
                        lc.add(lr);
                        System.out.println("新增捞人成功");
                    } catch (SQLException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                        System.out.println("新增捞人失败");
                    }
                }
                if(ADD.equals(pren)) {
                    step++;
                }
            }else if(UPDATE.equals(in.toUpperCase())||UPDATE.substring(0, 1).equals(in.toUpperCase())||UPDATE.equals(pren)) {
                pren = UPDATE;
                if(step == 1) {
                    System.out.println("请输入更新捞人的姓名：");

                }else if(step == 2){
                    lr.setUsername(in);
                    System.out.println("请输入更新捞人的年龄：");
                }else if(step == 3) {
                    lr.setAge(Integer.valueOf(in));
                    System.out.println("请输入更新捞人的爱好：");
                }else if(step == 4) {
                    lr.setHobby(in);
                    System.out.println("请输入更新捞人的性别：");
                }else if(step == 5) {
                    lr.setSex(Integer.valueOf(in));
                    System.out.println("请问更新这个捞人的更新人是谁：");
                }else if(step == 6) {
                    lr.setUpdate_user(in);
                    System.out.println("请问更新这个捞人ID是多少：");
                }else if(step == 7) {
                    lr.setId(Integer.valueOf(in));
                    try {
                        lc.deit(lr);
                        System.out.println("更新捞人成功");
                    } catch (SQLException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                        System.out.println("更新捞人失败");
                    }
                }
                if(UPDATE.equals(pren)) {
                    step++;
                }
            }
            else {
                System.out.println("您输入的值为："+in);
            }

        }
    }
}