JAVA学习笔记(五十)- JDBC Java数据库连接

JDBC操作步骤

/*
 * JDBC操作步骤
 *  
 */
public class Test01 {
    public static void main(String[] args) {
        try {
            //1.加载并注册驱动
            Class.forName("com.mysql.jdbc.Driver");
            //DriverManager.registerDriver(new com.mysql.jdbc.Driver());
            System.out.println("注册驱动成功！");
            //2.获取数据库连接Connection
            String url="jdbc:mysql://localhost:3306/test";
            String user="root";
            String password="123456";
            Connection conn=DriverManager.getConnection(url, user, password);
            System.out.println("连接数据库成功！");
            //3.创建Statement，并执行sql语句
            Statement stmt=conn.createStatement();
            String sql="insert into user values (null,‘蒋输‘,‘111111‘,21,‘2012-1-11‘)";
            int num=stmt.executeUpdate(sql);
            //4.处理执行结果 
            if(num>0){
                System.out.println("插入成功！");
            }else{
                System.out.println("插入失败！");
            }
            //5.关闭资源
            stmt.close();
            conn.close();
        } catch (ClassNotFoundException e) {
            System.out.println("驱动没找到！");
            e.printStackTrace();
        } catch (SQLException e) {
            System.out.println("数据库连接失败！");
            e.printStackTrace();
        }
    }
}

JDBC实现查询操作

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Date;

/*
 * JDBC实现查询操作
 */
public class Test02 {
    Connection conn = null;
    Statement stmt = null;
    ResultSet rs = null;

    // 查询用户信息
        public void queryUsers() {
            try {
                //1.加载并注册驱动
                Class.forName("com.mysql.jdbc.Driver");
                //2.获取数据库连接
                conn = DriverManager.getConnection(
                        "jdbc:mysql://localhost:3306/test", "root", "123456");
                //3.创建Statement对象并执行SQL语句
                stmt = conn.createStatement();
                String sql = "select * from user";
                //调用executeQuery()方法执行查询操作，返回一个ResultSet结果集，包含查询的结果
                rs = stmt.executeQuery(sql);
                //4.操作ResultSet结果集
                while (rs.next()) { //将指针向前移动一行，判断是否有记录
                    int id = rs.getInt("id"); //根据列名获取值
                    String name = rs.getString("name");
                    String password = rs.getString(3);//根据列的索引获取值
                    java.sql.Date birthday=rs.getDate(5);
                    System.out.println("编号:" + id + ",姓名：" + name + ",密码："
                            + password+" 生日："+birthday);
                }
            } catch (ClassNotFoundException e) {
                e.printStackTrace();
            } catch (SQLException e) {
                e.printStackTrace();
            } finally {
                //5.关闭资源
                try {
                    rs.close();
                    stmt.close();
                    conn.close();
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            }
        }


    //查询用户数量
    public void queryUserCount() {
        try {
            //1.加载并注册驱动
            Class.forName("com.mysql.jdbc.Driver");
            //2.获取数据库连接
            conn = DriverManager.getConnection(
                    "jdbc:mysql://localhost:3306/test", "root", "123456");
            //3.创建Statement对象并执行SQL语句
            stmt = conn.createStatement();
            String sql = "select count(id) from user";
            //调用executeQuery()方法执行查询操作，返回一个ResultSet结果集，包含查询的结果
            rs = stmt.executeQuery(sql);
            //4.操作ResultSet结果集
            int count=0;
            if (rs.next()) { //将指针向前移动一行，判断是否有记录
                count=rs.getInt(1);
            }
            System.out.println("共有"+count+"个用户！");
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            //5.关闭资源
            try {
                rs.close();
                stmt.close();
                conn.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }


    public static void main(String[] args) {
        new Test02().queryUserCount();
    }
}

将数据库连接信息保存在文件中

import java.io.FileInputStream;
import java.io.IOException;
import java.sql.Connection;
import java.sql.DriverManager;
import java.util.Properties;

/*
 * 将数据库连接信息保存在文件中
 */
public class Test03 {
    public static void main(String[] args) throws Exception {
        Properties p=new Properties();
        p.load(new FileInputStream("jdbc.properties"));
        Class.forName("com.mysql.jdbc.Driver");
        Connection conn=DriverManager.getConnection("jdbc:mysql://localhost:3306/test", p);
        System.out.println("连接数据库成功！ ");
    }
}