package cn.itcast.jdbc; /* jdbc快速入门 */ import java.sql.Connection; import java.sql.DriverManager; import java.sql.Statement; public class jdbcDemo01 { public static void main(String[] args) throws Exception { //1.导入驱动jar包 //2.注册驱动 Class.forName("com.mysql.jdbc.Driver"); //3获取数据库连接对象 Connection connection = DriverManager.getConnection("jdbc:mysql://localhost:3306/db3", "root", "root"); //4定义sql语句 String sql = "update emp set salary = 1000.0 where id = 1001"; //5.获取执行sql的对象 statement Statement stmt = connection.createStatement(); //6.执行sql int count = stmt.executeUpdate(sql); //7.处理结果 System.out.println(count); //8.释放资源 stmt.close(); connection.close(); } }
inser into
package cn.itcast.jdbc; /* 添加记录 */ import java.sql.Connection; import java.sql.DriverManager; import java.sql.SQLException; import java.sql.Statement; public class jdbcDemo02 { public static void main(String[] args) { Statement stmt = null; Connection conn = null; //1,注册驱动 try { Class.forName("com.mysql.jdbc.Driver"); //2,定义sql String sql = "insert into account(id,balance) values(3,600) "; try { //3,获取数据库连接对象 conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/db3", "root", "root"); //4,获取sql执行对象 stmt = conn.createStatement(); //5.执行sql int i = stmt.executeUpdate(sql); if (i > 0) { System.out.println("添加成功"); } else { System.out.println("添加失败"); } } catch (SQLException e) { e.printStackTrace(); } } catch (ClassNotFoundException e) { e.printStackTrace(); } finally { //释放资源 避免空指针异常 if (stmt != null) { try { stmt.close(); } catch (SQLException e) { e.printStackTrace(); } } if (stmt != null) { try { conn.close(); } catch (SQLException e) { e.printStackTrace(); } } } } }
修改
package cn.itcast.jdbc; /* 修改记录 */ import java.sql.Connection; import java.sql.DriverManager; import java.sql.SQLException; import java.sql.Statement; public class jdbcDemo03 { public static void main(String[] args) { Statement stmt = null; Connection conn = null; try { //1注册驱动 Class.forName("com.mysql.jdbc.Driver"); try { //获取数据库连接对象 conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/db3", "root", "root"); //定义sql语句 String sql = "Update account set balance = 6666 where id = 2"; //获取执行sql的对象 stmt = conn.createStatement(); //执行sql int i = stmt.executeUpdate(sql); if (i > 0) { System.out.println("修改成功"); } else { System.out.println("修改失败"); } } catch (SQLException e) { e.printStackTrace(); } } catch (ClassNotFoundException e) { e.printStackTrace(); } finally { //释放资源 if (stmt != null) { try { stmt.close(); } catch (SQLException e) { e.printStackTrace(); } } if (conn != null) { try { conn.close(); } catch (SQLException e) { e.printStackTrace(); } } } } }
删除记录
package cn.itcast.jdbc; /* 删除一条记录 */ import java.sql.Connection; import java.sql.DriverManager; import java.sql.SQLException; import java.sql.Statement; public class jdbcDemo04 { public static void main(String[] args) { Statement stmt = null; Connection conn = null; //1，注册驱动，导入驱动字节码 try { Class.forName("com.mysql.jdbc.Driver"); //2,创建数据库连接对象 try { conn = DriverManager.getConnection("jdbc:mysql://localhost/db3", "root", "root"); //3,定义sql语句 String sql = "delete from account where id = 3"; //创建执行sql的对象 stmt = conn.createStatement(); //执行sql int i = stmt.executeUpdate(sql); System.out.println(i); } catch (SQLException e) { e.printStackTrace(); } } catch (ClassNotFoundException e) { e.printStackTrace(); } finally { if(stmt != null) { try { stmt.close(); } catch (SQLException e) { e.printStackTrace(); } } if(conn != null) { try { conn.close(); } catch (SQLException e) { e.printStackTrace(); } } } } }
查询练习
package cn.itcast.domain; import java.sql.*; import java.util.ArrayList; import java.util.List; public class jdbcDemo07 { public static void main(String[] args) { Listemps = findAll(); for (Emp emp : emps) { System.out.println(emp); } System.out.println(emps.size()); } public static List findAll() { Connection conn = null; Statement stmt = null; ResultSet rs = null; List list = null; //注册驱动 try { Class.forName("com.mysql.jdbc.Driver"); //获取数据库连接 try { conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/db3","root","root"); //获取执行sql的对象 stmt = conn.createStatement(); String sql = "select * from emp"; //执行sql rs = stmt.executeQuery(sql); Emp emp = null; list = new ArrayList (); //遍历结果集对象 while (rs.next()) { int id = rs.getInt("id"); String ename = rs.getString("ename"); int job_id = rs.getInt("job_id"); int mgr = rs.getInt("mgr"); Date joindate = rs.getDate("joindate"); double salary = rs.getDouble("salary"); double bonus = rs.getDouble("bonus"); int dept_id = rs.getInt("dept_id"); emp = new Emp(); emp.setId(id); emp.setEname(ename); emp.setJob_id(job_id); emp.setMgr(mgr); emp.setJoindate(joindate); emp.setSalary(salary); emp.setBonus(bonus); emp.setDept_id(dept_id); list.add(emp); } } catch (SQLException e) { e.printStackTrace(); } } catch (ClassNotFoundException e) { e.printStackTrace(); } finally { if (rs != null) { try { rs.close(); } catch (SQLException e) { e.printStackTrace(); } } if (stmt != null) { try { stmt.close(); } catch (SQLException e) { e.printStackTrace(); } } if (conn != null) { try { conn.close(); } catch (SQLException e) { e.printStackTrace(); } } } return list; } }
jdbc工具类抽取
package cn.itcast.util; import java.io.FileReader; import java.io.IOException; import java.net.URL; import java.sql.*; import java.util.Properties; /** * jdbc工具类 */ public class JDBCutils { private static String url; private static String user; private static String password; private static String driver; /** * 文件的读取只需要一次既可以拿到值，可以使用静态代码块 */ static { //读取资源文件，获取值 try { //创建集合类对象 Properties prop = new Properties(); //获取src目录下的文件的方式--》ClassLoader 类加载器 ClassLoader classLoader = JDBCutils.class.getClassLoader(); URL resource = classLoader.getResource("jdbc.properties"); String path = resource.getPath(); System.out.println(path); //加载配置文件 prop.load(new FileReader(path)); url = prop.getProperty("url"); user = prop.getProperty("user"); password = prop.getProperty("password"); driver = prop.getProperty("driver"); try { Class.forName(driver); } catch (ClassNotFoundException e) { e.printStackTrace(); } } catch (IOException e) { e.printStackTrace(); } } /** * 获取连接对象 * * @return 连接对象 */ public static Connection getConnection() throws SQLException { return DriverManager.getConnection(url, user, password); } /** * 释放资源 * * @param stmt * @param conn */ public static void close(Statement stmt, Connection conn) { if (stmt != null) { try { stmt.close(); } catch (SQLException e) { e.printStackTrace(); } } if (conn != null) { try { conn.close(); } catch (SQLException e) { e.printStackTrace(); } } } /** * 释放资源 * * @param stmt * @param conn */ public static void close(ResultSet rs, Statement stmt, Connection conn) { if (stmt != null) { try { stmt.close(); } catch (SQLException e) { e.printStackTrace(); } } if (conn != null) { try { conn.close(); } catch (SQLException e) { e.printStackTrace(); } } if (rs != null) { try { rs.close(); } catch (SQLException e) { e.printStackTrace(); } } } }
利用jdb工具类c完成模拟登陆练习
jdbc工具类如下：
package cn.itcast.util; import java.io.FileReader; import java.io.IOException; import java.net.URL; import java.sql.*; import java.util.Properties; /** * jdbc工具类 */ public class JDBCutils { private static String url; private static String user; private static String password; private static String driver; /** * 文件的读取只需要一次既可以拿到值，可以使用静态代码块 */ static { //读取资源文件，获取值 try { //创建集合类对象 Properties prop = new Properties(); //获取src目录下的文件的方式--》ClassLoader 类加载器 ClassLoader classLoader = JDBCutils.class.getClassLoader(); URL resource = classLoader.getResource("jdbc.properties"); String path = resource.getPath(); System.out.println(path); //加载配置文件 prop.load(new FileReader(path)); url = prop.getProperty("url"); user = prop.getProperty("user"); password = prop.getProperty("password"); driver = prop.getProperty("driver"); try { Class.forName(driver); } catch (ClassNotFoundException e) { e.printStackTrace(); } } catch (IOException e) { e.printStackTrace(); } } /** * 获取连接对象 * * @return 连接对象 */ public static Connection getConnection() throws SQLException { return DriverManager.getConnection(url, user, password); } /** * 释放资源 * * @param stmt * @param conn */ public static void close(Statement stmt, Connection conn) { if (stmt != null) { try { stmt.close(); } catch (SQLException e) { e.printStackTrace(); } } if (conn != null) { try { conn.close(); } catch (SQLException e) { e.printStackTrace(); } } } /** * 释放资源 * * @param stmt * @param conn */ public static void close(ResultSet rs, Statement stmt, Connection conn) { if (stmt != null) { try { stmt.close(); } catch (SQLException e) { e.printStackTrace(); } } if (conn != null) { try { conn.close(); } catch (SQLException e) { e.printStackTrace(); } } if (rs != null) { try { rs.close(); } catch (SQLException e) { e.printStackTrace(); } } } }
期间利用debug工具判断出错误地点
package cn.itcast.jdbc; /* 通过键盘录入用户名和密码。判断是否登录成功 */ import cn.itcast.util.JDBCutils; import java.sql.Connection; import java.sql.ResultSet; import java.sql.SQLException; import java.sql.Statement; import java.util.Scanner; public class jdbcDemo09 { public static void main(String[] args) throws SQLException { Scanner sc = new Scanner(System.in); System.out.println("请输入用户名"); String inputusername = sc.nextLine(); System.out.println("请输入密码"); String inputpassword = sc.nextLine(); boolean flag = new jdbcDemo09().login(inputusername, inputpassword); if (flag ) { System.out.println("登录成功"); } else { System.out.println("账号或密码错误请重新再试"); } } /** * 登录方法 */ public boolean login(String username, String password) { Connection conn = null; Statement stmt = null; ResultSet rs = null; if (username == null || password == null) { return false; } try { conn = JDBCutils.getConnection(); stmt = conn.createStatement(); rs = stmt.executeQuery("select * from user "); while (rs.next()) { String username1 = rs.getString("username"); String password1 = rs.getString("password"); if (username.equals(username1) && password .equals(password1) ) { return true; } } } catch (SQLException e) { e.printStackTrace(); } finally { JDBCutils.close(rs, stmt, conn); } return false; } }
配置文件
url=jdbc:mysql:///db4 user=root password=root driver=com.mysql.jdbc.Driver