JDBC之Java连接mysql实现增删改查
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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
1 public static void main(String[] args) { 2 String url = "jdbc:mysql://localhost:3306/students"; 3 String user = "root"; 4 String password = "admin"; 5 Connection conn = null; 6 Statement st = null; 7 8 try { 9 // 1. 注册驱动 10 Class.forName("com.mysql.jdbc.Driver"); 11 // 2. 创建一个链接对象 12 conn = DriverManager.getConnection(url,user,password); 13 // 3. 创建一个sql语句的发送命令对象 14 String sql = "insert into student values(‘2001‘,‘Tom‘,‘20‘,‘7000‘)"; 15 st= conn.createStatement(); 16 // 4. 执行sql语句，拿到查询的结果集对象 17 st.executeQuery(sql);20 } catch (Exception e) { 21 e.printStackTrace(); 22 }finally { 23 // 5. 关闭链接 ，命令对象 ，结果集 24 if(st != null) { 25 try { 26 st.close(); 27 } catch (Exception e) { 28 e.printStackTrace(); 29 } 30 } 31 if(conn != null) { 32 try { 33 conn.close(); 34 } catch (Exception e) { 35 e.printStackTrace(); 36 } 37 } 38 }
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; }
}
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