JDBC——java连接MySQL封装处理

MySQL 内  Learn数据库中的 student_info表 中的字段信息为：

将字段数据封装，StudentInfo.java

package com.jdbc.model;
/*
 * student_info表的实体类
 * */
public class StudentInfo {
	public StudentInfo() {
		
	}

	public StudentInfo(Integer id, String name, String sex, Double score, String birthday) {
		this.id = id;
		this.name = name;
		this.sex = sex;
		this.score = score;
		this.birthday = birthday;
	}
	
	public StudentInfo(String name, String sex, Double score, String birthday) {
		this.name = name;
		this.sex = sex;
		this.score = score;
		this.birthday = birthday;
	}

	private Integer id;
	private String name;
	private String sex;
	private Double score;
	private String birthday;
	
	public Integer getId() {
		return id;
	}
	public void setId(Integer id) {
		this.id = id;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public String getSex() {
		return sex;
	}
	public void setSex(String sex) {
		this.sex = sex;
	}
	public Double getScore() {
		return score;
	}
	public void setScore(Double score) {
		this.score = score;
	}
	public String getBirthday() {
		return birthday;
	}
	public void setBirthday(String birthday) {
		this.birthday = birthday;
	}
	
	//重写显示
	@Override
	public String toString() {
		return "StudentInfo [id=" + id + ", name=" + name + ", sex=" + sex + ", score=" + score + ", birthday="
				+ birthday + "]";
	}
	
}

将数据库连接方法封装，为静态方法，可直接类名调用。ConnectionDB.java

package com.jdbc;

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

public class ConnectionDB {
	private static String url = "jdbc:mysql://localhost:3306/learn?useUnicode=true&characterEncoding=utf-8";
	private static String username = "root";  //MySQL账号
	private static String password = "123456";	 //MySQL密码
	private static Connection conn;
	
	/**
	 * 获取数据库连接
	 * @return
	 */
	public static Connection getConn() {
		try {
			Class.forName("com.mysql.jdbc.Driver");
		} catch (ClassNotFoundException e) {
			e.printStackTrace();
		}
		
		try {
			conn = DriverManager.getConnection(url, username, password);
		} catch (SQLException e) {
			e.printStackTrace();
		}
		return conn;
	}
	
	
}

接下来不利用任何框架，封装数据库增删改查方法，并做测试。StudentInfoDao.java

package com.jdbc.dao;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Date;
import java.util.List;

import com.jdbc.ConnectionDB;
import com.jdbc.model.StudentInfo;

/**
 * StudentInfo<->student_info  
 * O(Object)<->R(Relation)映射    不使用Mybatis,jpa ....框架
 */

public class StudentInfoDao {
	/**
	 *   新增学生
	 * @param studentInfo
	 */
	public void add(StudentInfo studentInfo) {
		// 连接数据库
		Connection conn = ConnectionDB.getConn();
		
		String sql = "insert into student_info(name,sex,birthday,score) values(?,?,?,?)";
		try {
			// 绑定
			PreparedStatement pst = conn.prepareStatement(sql); 
			
			// 通过对象往数据库中add数据
			// 几个问号几句 (从1开始)
			pst.setString(1, studentInfo.getName());
			pst.setString(2, studentInfo.getSex());
			pst.setString(3, studentInfo.getBirthday());
			pst.setDouble(4, studentInfo.getScore());
			
			pst.executeUpdate();
			
			// 关闭数据库
			pst.close();
			conn.close();
		} catch (SQLException e) {
			e.printStackTrace();
		}
	}
	
	/**
	 * 根据主键删除相应数据库中的数据
	 * @param id
	 */
	public void delById(Integer id) {
		// 连接数据库
		Connection conn = ConnectionDB.getConn();
		
		String sql = "delete from student_info where id=?";
		try {
			// 绑定
			PreparedStatement pst = conn.prepareStatement(sql);
			
			// 几个问号几句(从1开始)
			pst.setInt(1, id);
			
			pst.executeUpdate();
			
			// 关闭数据库
			pst.close();
			conn.close();
		} catch (SQLException e) {
			e.printStackTrace();
		}
		
	}
	
	/**
	 * 根据主键加载学生
	 * @param id
	 * @return
	 */
	public StudentInfo selById(Integer id) {
		// 连接数据库
		Connection conn = ConnectionDB.getConn();
		
		// 将查询得的数据存储进对象中，关系到对象的映射
		StudentInfo studentInfo = new StudentInfo();
		
		String sql = "select id,name,sex,birthday,score from student_info where id=?";
		try {
			// 绑定
			PreparedStatement pst = conn.prepareStatement(sql);
			
			// 几个问号几句(从1开始)
			pst.setInt(1, id);
			
			ResultSet rs = pst.executeQuery(); //rs为查询指针，初始指向要查询对象的前一个位置
			if(rs.next()) {
				
				//将查询结果存进对象
				studentInfo.setId(rs.getInt("id"));
				studentInfo.setName(rs.getString("name"));
				studentInfo.setSex(rs.getString("sex"));
				studentInfo.setBirthday(rs.getString("birthday"));
				studentInfo.setScore(rs.getDouble("score"));				
			}
			
			// 关闭数据库
			pst.close();
			conn.close();
		} catch (SQLException e) {
			e.printStackTrace();
		}
		
		return studentInfo;
	}
	
	/**
	 * 修改学生
	 * @param studentInfo
	 */
	public void update(StudentInfo studentInfo) {
		// 连接数据库
		Connection conn = ConnectionDB.getConn();
		
		String sql = "update student_info set name=?,sex=?,birthday=?,score=? where id=?";
		try {
			// 绑定
			PreparedStatement pst = conn.prepareStatement(sql);
			
			// 不修改的保持原数据
			// 几个问号几句(从1开始)
			pst.setString(1, studentInfo.getName());
			pst.setString(2, studentInfo.getSex());
			pst.setString(3, studentInfo.getBirthday());
			pst.setDouble(4, studentInfo.getScore());
			pst.setInt(5, studentInfo.getId());
			
			pst.executeUpdate();
			
			// 关闭数据库
			pst.close();
			conn.close();
		} catch (SQLException e) {
			e.printStackTrace();
		}
	}
	
	/**
	 * 查询所有学生, 所有则通过list返回全部学生
	 * @return
	 */
	public List<StudentInfo> selAll(){
		// 连接数据库
		Connection conn = ConnectionDB.getConn();
		
		// 新建list列表存对象
		List<StudentInfo> list = new ArrayList<>();
		
		String sql = "select id,name,sex,birthday,score from student_info";
		
		PreparedStatement pst;
		
		try {
			// 绑定
			pst = conn.prepareStatement(sql);
			
			ResultSet rs = pst.executeQuery(); //rs指针指向要查询的对象的前一个位置	
			while(rs.next()) {
				// 新建对象
				StudentInfo studentInfo = new StudentInfo();
				
				studentInfo.setId(rs.getInt("id"));
				studentInfo.setName(rs.getString("name"));
				studentInfo.setSex(rs.getString("sex"));
				studentInfo.setBirthday(rs.getString("birthday"));
				studentInfo.setScore(rs.getDouble("score"));	
				
				// 添加进list
				list.add(studentInfo);
			}
			// 关闭数据库
			pst.close();
			conn.close();
			
		} catch (SQLException e) {
			e.printStackTrace();
		}
		
		return list;
	}
	
	//调用测试
	public static void main(String[] args) {			
		// 日期转字符串
		Date date = new Date();
		SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
		String nowDate = sdf.format(date);
			
		StudentInfo si = new StudentInfo("Lily","1",100.0,nowDate);
			
		//new 工具对象
		StudentInfoDao studentDao = new StudentInfoDao();
		
		// 直接调用内部方法
		studentDao.add(si);  // 添加
		studentDao.delById(4); // 删除
			
		si = studentDao.selById(17); // 查询
		
		System.out.println("update 前 " + si); //调用内部的toString方法，输出查询到的数据
			
		si.setName("Jim"); 
		si.setSex("0");
		studentDao.update(si); // 对上面查询到的数据重新设置值
			
		si = studentDao.selById(17);
		System.out.println("update 后 " + si);
		
		List<StudentInfo> list = studentDao.selAll(); // 查询全部
			
		// 范型输出查询到的列表
		System.out.println("输出全部列表：");
		for(StudentInfo item:list) {
			System.out.println(item);
		}
	}
}