JDBC之Java连接mysql实现增删改查

使用软件：mysql、eclipse

链接步骤：

1.注册驱动

2.创建一个连接对象

3.写sql语句

4.执行sql语句并返回一个结果或者结果集

5.关闭链接（一般就是connection、statement、setresult）这三个连接对象，关闭顺序一般是（setresult    --->  statement  -->  setresult  ）

一、直接连接方法：（这种方法就是讲sql语句和结果所有的步骤写在一起） 不建议使用该方法

 public static void main(String[] args) {
         String url = "jdbc:mysql://localhost:3306/students";
         String user = "root";
         String password = "admin";
         Connection conn = null;
         Statement st = null;

         try {
             // 1. 注册驱动
             Class.forName("com.mysql.jdbc.Driver");
             // 2. 创建一个链接对象
             conn = DriverManager.getConnection(url,user,password);
             // 3. 创建一个sql语句的发送命令对象
             String sql = "insert into student values('2001','Tom','20','7000')";
             st= conn.createStatement();
             // 4. 执行sql语句，拿到查询的结果集对象
             st.executeQuery(sql);         } catch (Exception e) {
             e.printStackTrace();
         }finally {
             // 5. 关闭链接 ，命令对象 ，结果集
             if(st != null) {
                 try {
                     st.close();
                 } catch (Exception e) {
                     e.printStackTrace();
                 }
             }
             if(conn != null) {
                 try {
                     conn.close();
                 } catch (Exception e) {
                     e.printStackTrace();
                 }
             }
         }

二、建立工具类方法，将必要的几步写一个类，使用的时候直接调用（建议使用）

1.注册驱动、创建连接对象、关闭资源    这三部一般可以写一个类，由于写sql语句和执行sql语句的结果不一致，所以可以将其在用到的时候在写

2.一般写工具类都是写成静态方法，以方便调用

//这是工具类：

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

public class JdbcUtils {
	private static String driverName = "com.mysql.jdbc.Driver";
	private static String url = "jdbc:mysql://localhost:3306/student_achievement_system";
	private static String user = "root";
	private static String password = "admin";
	/**
	 * 链接数据库
	 */
	static {
		try {
			Class.forName(JdbcUtils.driverName);
		} catch (Exception e) {
			e.printStackTrace();
		}
	}
	/**
	 * 获取链接对象connection
	 * @return
	 */
	public static Connection getConnection() {
		try {
			return DriverManager.getConnection(JdbcUtils.url, JdbcUtils.user, JdbcUtils.password);
		} catch (Exception e) {
			e.printStackTrace();
		}
		return null;
	}
	/**
	 * 关闭资源
	 * @param conn
	 * @param st
	 * @param rs
	 */
	public static void close(Connection conn,Statement st,ResultSet rs) {
		if(rs != null) {
			try {
				rs.close();
			} catch (Exception e) {
				e.printStackTrace();
			}
		}
		if(st != null) {
			try {
				st.close();
			} catch (Exception e) {
				e.printStackTrace();
			}
		}
		if(conn != null) {
			try {
				conn.close();
			} catch (Exception e) {
				e.printStackTrace();
			}
		}
	}
}

　　

//这是对数据库的基本操作类

// 增加、删除、更新、查找一条、查找所有的方法

public class StudentsDaoImpl implements IStudentsDao {
　　　　//增加
	@Override
	public int save(Students student) {
		Connection conn = null;
		PreparedStatement ps = null;
		try {
			conn = JdbcUtils.getConnection();
			String sql = "insert into students values(?,?,?,?,?,?)";
			ps = conn.prepareStatement(sql);
			ps.setInt(1, student.getStudentId());
			ps.setString(2, student.getStudentName());
			ps.setString(3, student.getSex());
			ps.setString(4, student.getPhoneNo());
			ps.setString(5, student.getAddress());
			ps.setDate(6, (Date) student.getBirthday());
			int row = ps.executeUpdate();
			return row;
		} catch (Exception e) {
			e.printStackTrace();
		}finally {
			JdbcUtils.close(conn, ps, null);
		}
		return 0;
	}
　　　　　　//删除
	@Override
	public int delete(int studentId) {
		Connection conn = null;
		PreparedStatement ps = null;
		try {
			conn = JdbcUtils.getConnection();
			String sql = "delete from students where studentId=?";
			ps = conn.prepareStatement(sql);
			ps.setInt(1, studentId);
			int row = ps.executeUpdate();
			return row;
		} catch (Exception e) {
			e.printStackTrace();
		}finally {
			JdbcUtils.close(conn, ps, null);
		}
		return 0;
	}
　　　　//更新
	@Override
	public int update(int studentId, Students student) {
		Connection conn = null;
		PreparedStatement ps = null;
		try {
			conn = JdbcUtils.getConnection();
			String sql = "update students set studentName=?,sex=?,phoneNo=?,address=?,birthday=? where studentId=?";
			ps = conn.prepareStatement(sql);
			ps.setString(1, student.getStudentName());
			ps.setString(2, student.getSex());
			ps.setString(3, student.getPhoneNo());
			ps.setString(4, student.getAddress());
			ps.setDate(5, ((Date) student.getBirthday()));
			ps.setInt(6, studentId);
			int row = ps.executeUpdate();
			return row;
		} catch (Exception e) {
			e.printStackTrace();
		}finally {
			JdbcUtils.close(conn, ps, null);
		}
		return 0;
	}
　　　　　　//查找一条数据
	@Override
	public Students getByStudentId(int studentId) {
		Connection conn = null;
		PreparedStatement ps = null;
		ResultSet rs = null;
		try {
			conn = JdbcUtils.getConnection();
			String sql = "select * from students where studentId=?";
			ps = conn.prepareStatement(sql);
			ps.setInt(1, studentId);
			rs = ps.executeQuery();
			if(rs.next()) {
				Students student = new Students();
				student.setStudentId(rs.getInt("studentId"));
				student.setStudentName(rs.getString("studentName"));
				student.setSex(rs.getString("sex"));
				student.setPhoneNo(rs.getString("phoneNo"));
				student.setAddress(rs.getString("address"));
				student.setBirthday(rs.getDate("birthday"));
				return student;
			}
		} catch (Exception e) {
			e.printStackTrace();
		}finally {
			JdbcUtils.close(conn, ps, rs);
		}
		return null;
	}
　　　　　　//查找所有数据
	@Override
	public List<Students> getAll() {
		Connection conn = null;
		PreparedStatement ps = null;
		ResultSet rs = null;
		try {
			conn = JdbcUtils.getConnection();
			String sql = "select * from students";
			ps = conn.prepareStatement(sql);
			rs = ps.executeQuery();
			List<Students> studentsList = new ArrayList<>();
			while(rs.next()) {
				Students student = new Students();
				student.setStudentId(rs.getInt("studentId"));
				student.setStudentName(rs.getString("studentName"));
				student.setSex(rs.getString("sex"));
				student.setPhoneNo(rs.getString("phoneNo"));
				student.setAddress(rs.getString("address"));
				student.setBirthday(rs.getDate("birthday"));
				studentsList.add(student);
			}
			return studentsList;
		} catch (Exception e) {
			e.printStackTrace();
		}finally {
			JdbcUtils.close(conn, ps, rs);
		}
		return null;
	}
}