JDBC的几种封装

1、不封装的写法

package jiahanglee;import java.sql.*;/** * Created by jiahang Lee on 2017/5/8. */public class Jdbc {    public static void main(String []args)    {        Connection conn = null;        try {            //加载驱动            Class.forName("com.mysql.jdbc.Driver");            //建立数据库连接            String url = "jdbc:mysql://localhost:3306/jdbc?useUnicode=true&&characterEncoding=UTF-8";            conn = DriverManager.getConnection(url,"root","");            //执行操作数据库            Statement stmt = conn.createStatement();            ResultSet rs = stmt.executeQuery("SELECT * FROM Student ");            while (rs.next()){                System.out.print(rs.getString("name")+"\n");            }            } catch (SQLException e) {                e.printStackTrace();            }         catch (ClassNotFoundException e) {            e.printStackTrace();        }finally {            try {                //关闭                conn.close();            } catch (SQLException e) {                e.printStackTrace();            }        }    }}

2、一部份封装
connection1

package Utils;import java.sql.*;/** * Created by jiahang Lee on 2017/5/8. */public class Connection1 {    public static Connection getConnection(){      Connection conn = null;        try {            //加载驱动            Class.forName("com.mysql.jdbc.Driver");            //连接数据库            String url = "jdbc:mysql://127.0.0.1:3306/jdbc?useUnicode=true&characterEncoding=UTF-8";                conn =  DriverManager.getConnection(url,"root","");            } catch (SQLException e) {            e.printStackTrace();        }         catch (ClassNotFoundException e){            e.printStackTrace();        }        return conn;    }}

test

package jiahanglee;import Utils.Connection1;import java.sql.*;/** * Created by jiahang Lee on 2017/5/8. */public class test {    public static void main(String arg[]){        Connection1 con = new Connection1();        java.sql.Connection conn = (java.sql.Connection) con.getConnection();        try {            Statement stmt = conn.createStatement();            ResultSet rs = stmt.executeQuery("SELECT * FROM Student");            while(rs.next())            {System.out.print(rs.getString(1));}            rs.close();        } catch (SQLException e) {            e.printStackTrace();        }    }}

3、connection2

package Utils;import java.io.File;import java.io.IOException;import java.io.InputStream;import java.sql.Connection;import java.sql.DriverManager;import java.sql.SQLException;import java.util.Properties;/** * Created by jiahang Lee on 2017/5/8. */public class connection2 {    private static Properties properties;    static{        InputStream is = connection2.class.getResourceAsStream("../resource/df.properties");        properties = new Properties();        try {            properties.load(is);        } catch (IOException e) {            e.printStackTrace();        }    }    public static Connection getConnection(){        Connection connection = null;        try {            Class.forName(properties.getProperty("dbDrive"));                connection = DriverManager.getConnection(                        properties.getProperty("dbURL"),                        properties.getProperty("user"),                        properties.getProperty("password"));            } catch (SQLException e) {                e.printStackTrace();            }         catch (ClassNotFoundException e) {            e.printStackTrace();        }        return connection;    }}

test2

package jiahanglee;import Utils.connection2;import java.sql.*;/** * Created by jiahang Lee on 2017/5/8. */public class test2 {    public static void main(String arg[]){        connection2 conr = new connection2();        Connection conn = conr.getConnection();        try {            Statement stmp = conn.createStatement();            ResultSet rs = stmp.executeQuery("SELECT * FROM Student");            while(rs.next())                System.out.print(rs.getString(1)+"\n");            conn.close();        } catch (SQLException e) {            e.printStackTrace();        }    }}

3、完全封装
connection3

package Utils;import en.Student;import java.sql.Connection;import java.sql.ResultSet;import java.sql.SQLException;import java.sql.Statement;import java.util.ArrayList;import java.util.List;/** * Created by jiahang Lee on 2017/5/8. */public class Connection3 {connection2 cm = new connection2();public List<Student> select(){    List<Student> list = new ArrayList<Student>();    Connection conn = cm.getConnection();    try {        Statement statement = conn.createStatement();        ResultSet rs = statement.executeQuery("SELECT *FROM Student");        while(rs.next())        {            Student s = new Student();            s.setName(rs.getString("name"));            list.add(s);        }    } catch (SQLException e) {        e.printStackTrace();    }    try {        conn.close();    } catch (SQLException e) {        e.printStackTrace();    }    return  list;}}

test3

package jiahanglee;import Utils.Connection3;import en.Student;import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import java.io.IOException;import java.io.PrintWriter;import java.sql.Connection;import java.util.ArrayList;import java.util.List;/** * Created by jiahang Lee on 2017/5/8. */public class test3 extends HttpServlet{    @Override    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {        List<Student> list;        resp.setContentType("text/html;charset=utf-8");        Connection3 c3 = new Connection3();        list = c3.select();        for(Student i:list)        {            resp.setContentType("text/html");            resp.setCharacterEncoding("utf-8");            PrintWriter writer=resp.getWriter();            writer.println(i.getName().toString());        }    }    @Override    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {        resp.setContentType("text/html;charset=utf-8");        Connection3 c3 = new Connection3();        List<Student> list ;        list = c3.select();        for(Student i:list)        {            resp.setContentType("text/html");            resp.setCharacterEncoding("utf-8");            PrintWriter writer=resp.getWriter();            writer.println(i.getName().toString());        }    }}