jdbc连接及封装

爱被打了一巴掌 2024-03-30 14:34 192阅读 0赞

jdbc连接

  1. //1.查询所有
  2.      public static void main(String[] args) {
  4.         //1. 导入数据库对应的jar包
  5.         //String url = "jdbc:mysql:///test?userSSL=false";//当前主机简写
  6.         //String url = "jdbc:mysql://127.0.0.1/test?userSSL=false";
  7.         String url = "jdbc:mysql://localhost:3306/test?userSSL=false";";
  8.         String username = "root";
  9.         String password = "1234";
  10.         try {
  12.             //2. 注册驱动
  13.             Class.forName("com.mysql.cj.jdbc.Driver");
  14.             //3. 获取数据库连接对象
  15.             Connection conn = DriverManager.getConnection(url, username, password);
  16.             //4. 定义sql语句
  17.             String sql = "select * from qh_student";
  18.             //5. 获取执行sql的对象 Statement
  19.             Statement stmt = conn.createStatement();
  20.             //6. 执行sq
  21.             ResultSet rs = stmt.executeQuery(sql);
  22.             //7. 对结果进行处理
  23.             while (rs.next()){
  25.                 String id = rs.getString("sid");
  26.                 String name = rs.getString("username");
  27.                 String pwd = rs.getString("password");
  28.                 System.out.println(id+"-"+name+"-"+pwd);
  29.             }
  30.             //8. 释放资源
  31.             rs.close();
  32.             stmt.close();
  33.             conn.close();
  34.         } catch (Exception e) {
  36.             System.out.println("数据库连接失败!");
  37.             e.printStackTrace();
  38.         }
  39.     }
  40. //2.添加
  41.     public static void main(String[] args) {
  43.         String url = "jdbc:mysql:///test?userSSL=false";
  44.         String username = "root";
  45.         String password = "1234";
  46.         try {
  48.             Class.forName("com.mysql.cj.jdbc.Driver");;
  49.             Connection conn = DriverManager.getConnection(url, username, password);
  50.             String sql = "insert into qh_student(username,password)" +
  51.                     "values ('朱八','zb')";
  52.             Statement stmt = conn.createStatement();
  53.             int count = stmt.executeUpdate(sql);
  54.             System.out.println("影响的行数= " + count);
  55.             stmt.close();
  56.             conn.close();
  57.         } catch (Exception e) {
  59.             System.out.println("数据库连接失败!");
  60.             e.printStackTrace();
  61.         }
  62.     }
  63. //3/删除
  64.     public static void main(String[] args) {
  66.         String url = "jdbc:mysql:///test?userSSL=false";
  67.         String username = "root";
  68.         String password = "1234";
  69.         try {
  71.             Class.forName("com.mysql.cj.jdbc.Driver");
  72.             Connection conn = DriverManager.getConnection(url, username, password);
  73.             String sql = "delete from qh_student where sid='6'";
  74.             Statement stmt = conn.createStatement();
  75.             int count = stmt.executeUpdate(sql);
  76.             System.out.println("影响的行数= " + count);
  77.             stmt.close();
  78.             conn.close();
  79.         } catch (Exception e) {
  81.             System.out.println("数据库连接失败!");
  82.             e.printStackTrace();
  83.         }
  84.     }

jdbc连接封装

  1. //1.JdbcUtils : 
  2.     public class JdbcUtils {
  4.         private static final String DRIVERCLASSNAME = "com.mysql.cj.jdbc.Driver";
  5.         private static final String URL = "jdbc:mysql://localhost:3306/test?useSSL=false&useUnicode=true&characterEncoding=utf8&serverTimezone=Asia/Shanghai";
  6.         private static final String USERNAME = "root";
  7.         private static final String PASSWORD = "1234";
  8.         private JdbcUtils() {
  10.         }
  11.         //获取连接对象
  12.         public static Connection getConnnection() {
  14.             try {
  16.                 Class.forName("com.mysql.cj.jdbc.Driver");
  17.                 Connection connection = DriverManager.getConnection(
  18.                         URL,
  19.                         USERNAME,
  20.                         PASSWORD
  21.                 );
  22.                 return connection;
  23.             } catch (SQLException e) {
  25.                 e.printStackTrace();
  26.             }
  27.             return  null ;
  28.         }
  29.         //释放资源
  30.         //如果是针对ddl语句或者dml语句,Statement对象以及Connection对象关闭
  31.         public static void close(Statement stmt, Connection conn) {
  33.             close(null, stmt, conn);
  34.         }
  35.         //如果是针对DQL语句,ResultSet对象以及Statement以及Connection对象关闭
  36.         public static void close(ResultSet rs, Statement stmt, Connection conn) {
  38.             if (rs != null) {
  40.                 try {
  42.                     rs.close();
  43.                 } catch (SQLException e) {
  45.                     e.printStackTrace();
  46.                 }
  47.             }
  48.             if (stmt != null) {
  50.                 try {
  52.                     stmt.close();
  53.                 } catch (SQLException e) {
  55.                     e.printStackTrace();
  56.                 }
  57.             }
  58.             if (conn != null) {
  60.                 try {
  62.                     conn.close();
  63.                 } catch (SQLException e) {
  65.                     e.printStackTrace();
  66.                 }
  67.             }
  68.         }
  69.     }
  70. //2.JdbcUtilsProperties
  71. jdbc.properties : 
  72.     driverClassName=com.mysql.cj.jdbc.Driver
  73.     url=jdbc:mysql://localhost:3306/数据库?useSSL=false&useUnicode=true&characterEncoding=utf8&serverTimezone=Asia/Shanghai
  74.     username=root
  75.     password=123456
  76. JdbcUtilsProperties : 
  77.     public class JdbcUtilsProperties {
  79.         //jdbc.properties路径
  80.         private static final String PROPERTIESPATH="com\\qh\\jdbc\\jdbc.properties";
  81.         private static String DRIVERCLASSNAME = null;
  82.         private static String URL = null;
  83.         private static String USERNAME = null;
  84.         private static String PASSWORD = null;
  85.         //静态代码块
  86.         static {
  88.             try {
  90.                 Properties prop = new Properties();
  91.                 InputStream inputStream = JdbcUtilsProperties.class.getClassLoader().getResourceAsStream(PROPERTIESPATH);
  92.                 prop.load(inputStream);
  93.                 DRIVERCLASSNAME = prop.getProperty("driverClassName"); //获取驱动类
  94.                 URL = prop.getProperty("url");  //获取url
  95.                 USERNAME = prop.getProperty("username"); //用户名username
  96.                 PASSWORD = prop.getProperty("password");//密码password
  97.                 //注册驱动
  98.                 Class.forName(DRIVERCLASSNAME);
  99.             } catch (Exception e) {
  101.                 e.printStackTrace();
  102.             } 
  103.         }
  104.         private JdbcUtilsProperties() {
  106.         }
  107.         //获取连接对象
  108.         public static Connection getConnnection() {
  110.             try {
  112.                 Class.forName("com.mysql.cj.jdbc.Driver");
  113.                 Connection connection = DriverManager.getConnection(
  114.                         URL,
  115.                         USERNAME,
  116.                         PASSWORD
  117.                 );
  118.                 return connection;
  119.             } catch (SQLException e) {
  121.                 e.printStackTrace();
  122.             }
  123.             return  null ;
  124.         }
  125.         //释放资源
  126.         //如果是针对ddl语句或者dml语句,Statement对象以及Connection对象关闭
  127.         public static void close(Statement stmt, Connection conn) {
  129.             close(null, stmt, conn);
  130.         }
  131.         //如果是针对DQL语句,ResultSet对象以及Statement以及Connection对象关闭
  132.         public static void close(ResultSet rs, Statement stmt, Connection conn) {
  134.             if (rs != null) {
  136.                 try {
  138.                     rs.close();
  139.                 } catch (SQLException e) {
  141.                     e.printStackTrace();
  142.                 }
  143.             }
  144.             if (stmt != null) {
  146.                 try {
  148.                     stmt.close();
  149.                 } catch (SQLException e) {
  151.                     e.printStackTrace();
  152.                 }
  153.             }
  154.             if (conn != null) {
  156.                 try {
  158.                     conn.close();
  159.                 } catch (SQLException e) {
  162.                     e.printStackTrace();
  163.                 }
  164.             }
  165.         }
  166.     }
  167. //使用 : 
  168. Test :
  169.     public class Test {
  171.         public static void main(String[] args) throws SQLException {
  173.             Connection conn = JdbcUtils.getConnnection();
  174.             String sql="select * from student where username=? and password=?";
  175.             PreparedStatement ps = conn.prepareStatement(sql);
  176.             ps.setString(1,"张三");
  177.             ps.setString(2,"zs");
  178.             ResultSet rs = ps.executeQuery();
  179.             if (rs.next()) {
  181.                 System.out.println("登陆成功!");
  182.             }else{
  184.                 System.out.println("登录失败!");
  185.             }
  186.             JdbcUtils.close(rs,ps,conn);
  187.         }
  188.     }

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