使用java连接mysql数据库并实现增删改查等操作

package com.cn.edu;import java.beans.Statement;import java.sql.Connection;import java.sql.DriverManager;import java.sql.PreparedStatement;import java.sql.ResultSet;import java.sql.SQLException;public class helloworld {  private Connection conn = null;  PreparedStatement statement = null;  // connect to MySQL  void connSQL() {    String url = "jdbc:mysql://localhost:3306/hello?characterEncoding=UTF-8";    String username = "root";    String password = "root"; // 加载驱动程序以连接数据库    try {      Class.forName("com.mysql.jdbc.Driver" );      conn = DriverManager.getConnection( url,username, password );      }    //捕获加载驱动程序异常     catch ( ClassNotFoundException cnfex ) {       System.err.println(       "装载 JDBC/ODBC 驱动程序失败。" );       cnfex.printStackTrace();     }     //捕获连接数据库异常     catch ( SQLException sqlex ) {       System.err.println( "无法连接数据库" );       sqlex.printStackTrace();     }  }  // disconnect to MySQL  void deconnSQL() {    try {      if (conn != null)        conn.close();    } catch (Exception e) {      System.out.println("关闭数据库问题 ：");      e.printStackTrace();    }  }  // execute selection language  ResultSet selectSQL(String sql) {    ResultSet rs = null;    try {      statement = conn.prepareStatement(sql);      rs = statement.executeQuery(sql);    } catch (SQLException e) {      e.printStackTrace();    }    return rs;  }  // execute insertion language  boolean insertSQL(String sql) {    try {      statement = conn.prepareStatement(sql);      statement.executeUpdate();      return true;    } catch (SQLException e) {      System.out.println("插入数据库时出错：");      e.printStackTrace();    } catch (Exception e) {      System.out.println("插入时出错：");      e.printStackTrace();    }    return false;  }  //execute delete language  boolean deleteSQL(String sql) {    try {      statement = conn.prepareStatement(sql);      statement.executeUpdate();      return true;    } catch (SQLException e) {      System.out.println("插入数据库时出错：");      e.printStackTrace();    } catch (Exception e) {      System.out.println("插入时出错：");      e.printStackTrace();    }    return false;  }  //execute update language  boolean updateSQL(String sql) {    try {      statement = conn.prepareStatement(sql);      statement.executeUpdate();      return true;    } catch (SQLException e) {      System.out.println("插入数据库时出错：");      e.printStackTrace();    } catch (Exception e) {      System.out.println("插入时出错：");      e.printStackTrace();    }    return false;  }  // show data in ju_users  void layoutStyle2(ResultSet rs) {    System.out.println("-----------------");    System.out.println("执行结果如下所示:");    System.out.println("-----------------");    System.out.println(" 用户ID" + "/t/t" + "淘宝ID" + "/t/t" + "用户名"+ "/t/t" + "密码");    System.out.println("-----------------");    try {      while (rs.next()) {        System.out.println(rs.getInt("ju_userID") + "/t/t"            + rs.getString("taobaoID") + "/t/t"            + rs.getString("ju_userName")             + "/t/t"+ rs.getString("ju_userPWD"));      }    } catch (SQLException e) {      System.out.println("显示时数据库出错。");      e.printStackTrace();    } catch (Exception e) {      System.out.println("显示出错。");      e.printStackTrace();    }  }  public static void main(String args[]) {    helloworld h = new helloworld();    h.connSQL();    String s = "select * from ju_users";    String insert = "insert into ju_users(ju_userID,TaobaoID,ju_userName,ju_userPWD) values("+8329+","+34243+",'mm','789')";    String update = "update ju_users set ju_userPWD =123 where ju_userName= 'mm'";    String delete = "delete from ju_users where ju_userName= 'mm'";    if (h.insertSQL(insert) == true) {      System.out.println("insert successfully");      ResultSet resultSet = h.selectSQL(s);      h.layoutStyle2(resultSet);    }    if (h.updateSQL(update) == true) {      System.out.println("update successfully");      ResultSet resultSet = h.selectSQL(s);      h.layoutStyle2(resultSet);    }    if (h.insertSQL(delete) == true) {      System.out.println("delete successfully");      ResultSet resultSet = h.selectSQL(s);      h.layoutStyle2(resultSet);    }    h.deconnSQL();  }}