JavaEE-0-JDBC数据库连接

1、直接在main方法中一步一步连接数据库

具体的每一步的解析都已经写在注释里了，注意这里获取Connection对象的方法已经被抽象出来专门放在一个类里面了

public class JDBCDemo {
    public static void main(String[] args) {
        try {
            
            //注册驱动
            Driver drive= new Driver();
            DriverManager.registerDriver(drive);
            
            //获取数据库连接对象 
            String url="jdbc:mysql://localhost:3306/day04";
            Connection conn=(Connection) DriverManager.getConnection(url,"root","root");
            
            //获取实际的SQL语句执行者对象
            Statement st = (Statement) conn.createStatement();
            //对执行者对象进行操作！然后放入结果集
            ResultSet rs=st.executeQuery("select * from category");
            
            //对结果集进行遍历
            while (rs.next())
            {
                //可以单独获得结果集中的一个字段
                Object cid = rs.getObject("cid");
                Object cname = rs.getObject("cname");
                System.out.println(cid+"\t"+cname); 
            }
            
            //连接对象、结果集、执行者对象都要进行资源释放~~
            rs.close();
            st.close();
            conn.close();
            
            
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
}

专门用于管理Connection对象的一个类：

public class JDBCUtils {
    private static String driverName="com.mysql.jdbc.Driver";
    private static String url="jdbc:mysql://localhost:3306/day04";
    private static String userName="root";
    private static String password="root";

    //静态代码块
    static{
        try {
            Class.forName(driverName);
        } catch (ClassNotFoundException e) {
            //驱动加载失败
            System.out.println("驱动加载失败，请检查驱动包！");
            throw new RuntimeException("驱动加载失败，请检查驱动包！");
        }
    }
    
    public static java.sql.Connection getConnection() throws Exception{
        Class.forName(driverName);
        
        java.sql.Connection connection =DriverManager.getConnection(url,userName,password);
        
        return connection;
    }
    
    public static void closeAll(java.sql.Connection connection,Statement st,ResultSet rs)
    {
        if(connection!=null)
        {
            try {
                connection.close();
            } catch (SQLException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
        if(st!=null)
        {
            try {
                st.close();
            } catch (SQLException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
        if(rs!=null)
        {
            try {
                rs.close();
            } catch (SQLException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
        }
        
    }
}

2、对常用的数据库操作方法进行封装

    public static void insert(){
        Connection connection=null;
        Statement statement=null;
        
        try {
            connection=JDBCUtils.getConnection();
            statement = connection.createStatement();
            int rows = statement.executeUpdate("insert into category (cname) values ('饮料')");
            System.out.println("成功插入"+rows+"行");
            
        } catch (Exception e) {
            // TODO: handle exception
        }finally {
            JDBCUtils.closeAll(connection, statement, null);
        }
        
    }
    
    public static void delete(){
        Connection connection=null;
        Statement statement=null;
        ResultSet ra=null;
        
        try {
            connection=JDBCUtils.getConnection();
            statement = connection.createStatement();
            int rows=statement.executeUpdate("delete from category where cname='饮料'");
            System.out.println("成功删除"+rows+"行");

        } catch (Exception e) {
            // TODO: handle exception
        }finally {
            JDBCUtils.closeAll(connection, statement, ra);
        }
    }
    
    public static void update(){
        Connection connection=null;
        Statement statement=null;
        ResultSet ra=null;
        
        try {
            
        } catch (Exception e) {
            // TODO: handle exception
        }finally {
            JDBCUtils.closeAll(connection, statement, ra);
        }
    }
    
    public static void query(){
        Connection connection=null;
        Statement statement=null;
        ResultSet ra=null;
        
        try {
            
        } catch (Exception e) {
            // TODO: handle exception
        }finally {
            JDBCUtils.closeAll(connection, statement, ra);
        }
    }