jdbc

1、传统方式

一、src目录下

 二、

//普通的增，改，删         查
public class Demo1 {
    public static void main(String[] args)throws ClassNotFoundException, SQLException {
        Class.forName("com.mysql.jdbc.Driver");                //加载驱动类
        Connection con = DriverManager.getConnection(        //建立连接
                "jdbc:mysql://localhost:3306/shujuku",
                "root","123");
        System.out.println(con);                            //得到语句发送器
        
        Statement statement = con.createStatement();        //导Java.sql.statement
        
        //String s1 = "insert into sp(bianhao,mingcheng,danjia,geshu)values('05','huotuichang','5.5','30')";//增加
        //String s1 = "update sp set mingcheng='huotui' where bianhao='05'";//改变
        //String s1 = "delete from sp where bianhao='05'";                //删除
        //int a = statement.executeUpdate(s1);
        //System.out.println(a);
        String s2 = "select * from sp";
        ResultSet rs = statement.executeQuery(s2);
        while(rs.next()){
            System.out.println(rs.getString(1)+"  "+rs.getString(2)+"  "+rs.getString(3)+"  "+rs.getString(4));
        }
        rs.close();
        statement.close();
        con.close();
    }
}

/**
 *得到语句发送器Statement发送查询语句，获得 结果集 和行光标（操纵行光标看有多少行，得到每行有多少列进行遍历），
 *creatstatement();（重载形式传参）创建什么样的语句发送器就注定了会得到什么样的结果集（结果集的特性）
 */
public class Demo2 {
    public static void main(String[] args) throws SQLException {
        Connection con = null;
        Statement stmt = null;
        ResultSet rs = null;
        try{
            con = DriverManager.getConnection("jdbc:mysql://localhost:3306/shujuku", "root", "123");
                System.out.println(con);        
            stmt = con.createStatement();        //生成的结果集不滚动
                String s1 = "select * from sp";            //查询语句    
            rs = stmt.executeQuery(s1);                //操作结果集要学习移动ResultSet内部的“行光标”，以及获取当前行上的每一列上的数据：
            
            Boolean b = rs.last();    //把行光标放在最后一行
            int a = rs.getRow();    //得到当前多少行
            System.out.println("一共有"+a+"行");
            rs.beforeFirst();        //挪到第一行上面
            
            int count = rs.getMetaData().getColumnCount();//得到查询结果有多少列
            
            while(rs.next()){
                for (int i = 1; i <= count; i++) {
                    if(i==count){
                        System.out.println(rs.getString(i));
                    }else{
                        System.out.print(rs.getString(i)+",   ");
                    }
                }
            }
        }catch(Exception e){
            throw new RuntimeException();
        }finally{
            if(rs!=null)rs.close();
            if(stmt!=null)stmt.close();
            if(con!=null)con.close();
        }
    }
}

/**
 * 演示不安全的statement
 */
public class Demo3 {

    public static void main(String[] args) throws ClassNotFoundException, SQLException {
        Boolean b1 = Demo3.fun("张三","123");
        Boolean b2 = Demo3.fun("李四", "123");
        //Boolean b3 = Demo3.fun("a' or 'a' = 'a","a' or 'a' ='a ");
        System.out.println(b1);
        System.out.println(b2);
        //System.out.println(b3);
    }
    public static boolean fun(String username,String password) throws ClassNotFoundException, SQLException{
        String driverClassName = "com.mysql.jdbc.Driver";
        String mysqlusername = "root";
        String mysqlpassword = "123";
        String url = "jdbc:mysql://localhost:3306/shujuku";
        
        Class.forName(driverClassName);
        Connection con = DriverManager.getConnection(url, mysqlusername, mysqlpassword);
            System.out.println(con);
        Statement stmt = con.createStatement();
            String sql = "select * from login where username = ' "+username+" ' and password = ' "+password+" '";
        ResultSet rs = stmt.executeQuery(sql);
        return rs.next();
    }
}

/**
 * 防sql攻击的语句发送器，PreparedStatement,一出生就和sql语句绑定在一起，想赋值调用一系列setXXX（）方法
 */
public class Demo4 {
    public static void main(String[] args) throws ClassNotFoundException, SQLException {
        Boolean b1 = Demo4.fun("李四","123");
        Boolean b2 = Demo4.fun("a' or 'a' = 'a", "a' or 'a'='a");
        Boolean b3 = Demo4.fun("a' or 'a' = 'a", "a' or 'a'='a");
        System.out.println(b1);
        System.out.println(b2);
        System.out.println(b3);
    }
    public static boolean fun(String username,String password) throws ClassNotFoundException, SQLException{
        String driverClassName = "com.mysql.jdbc.Driver";
        String url = "jdbc:mysql://localhost:3306/shujuku";
        String mysqlusername = "root";
        String mysqlpassword = "123";
        Class.forName(driverClassName);
        Connection con = DriverManager.getConnection(url, mysqlusername, mysqlpassword);
            String sql = "select * from login where username =? and password =?";
        PreparedStatement pstmt = con.prepareStatement(sql);//语句发送器一出生就和模板绑定在一起，sql语句必须遵循这个模板
                pstmt.setString(1, username);
                pstmt.setString(2, password);
        ResultSet rs = pstmt.executeQuery();
                /*rs.last();int a = rs.getRow();//先到最后一行然后获取一共有多少行
                rs.beforeFirst();
                int cols = rs.getMetaData().getColumnCount();
                while(rs.next()){
                    for (int i = 1; i <=cols; i++) {
                        if (i==cols) {
                            System.out.println(rs.getString(i));
                        }
                        System.out.print(rs.getString(i)+",  ");
                    }
                }*/
        /*rs.close();
        pstmt.close();
        con.close();*/
        return rs.next();
    }
}

 java中虽然没有提供连接池，但是提供了连接池的接口DataSource，所有的连接池必须要实现这一接口

2、dbcp连接池

 

 3、c3p0连接池

 或者准备一个必须取名为c3p0-config.xml的配置文件，必须放在src下，然后可根据传入的参数不同，随意切换数据库

 

-------------------------------------------------------------

以上操作需要的jar包

大数据

一、图片存入数据库，当然实际将图片的路径存入数据库

public class DemoBlobTu {
    @Test
    public void fun1() throws Exception{            //将图片存入数据库中
        Connection con = JdbcUtils.getConnection();
        String sql = "insert into dashuju (id,filename,data) values(?,?,?)";
        PreparedStatement pstmt = con.prepareStatement(sql);        //语句发送器
        pstmt.setInt(1, 1);
        pstmt.setString(2,"link.jpg");
        
        InputStream is = new FileInputStream("F:\link.jpg");
        pstmt.setBinaryStream(3,is);
        int a = pstmt.executeUpdate();
        System.out.println(a);
    }
    public void funn2() throws Exception{
        Connection con = JdbcUtils.getConnection();
        String sql = "select filename,data from dashuju where id=?";
        PreparedStatement pstmt = con.prepareStatement(sql);
        
        pstmt.setInt(1, 1);
        ResultSet rs = pstmt.executeQuery();
        rs.next();
        
        String filename = rs.getString("filename");
        OutputStream out = new FileOutputStream("E:\" + filename);
        
        InputStream in = rs.getBinaryStream("data");
        IOUtils.copy(in, out);
    }
}

二、音乐存入数据库

public class DemoBlobYing {
    public void fun1() throws Exception{    //把音乐保存到数据库
        Connection con = JdbcUtils.getConnection();
        System.out.println(con);
        String sql = "insert into dashuju (id,filename,data) values(?,?,?)";
        PreparedStatement pstmt = con.prepareStatement(sql);
        pstmt.setInt(1, 4);
        pstmt.setString(2, "李琦 - 金玉良缘.mp3");
        InputStream os = new FileInputStream("F://李琦 - 金玉良缘.mp3");
        pstmt.setBinaryStream(3, os,1024500);
        int a = pstmt.executeUpdate();
        System.out.println(a);
    }
    @Test
    public void fun2() throws Exception{
        Connection con = JdbcUtils.getConnection();
        String sql = "select * from dashuju where id='4'";
        PreparedStatement pstmt = con.prepareStatement(sql);
        ResultSet rs = pstmt.executeQuery();
        rs.next();
        String filename=rs.getString("filename");
        OutputStream os = new FileOutputStream("E://"+filename);
        InputStream is = rs.getBinaryStream("data");
        IOUtils.copy(is,os);    
        os.close();
        is.close();
    /*    rs.next();
        
        String filename = rs.getString("filename");
        OutputStream out = new FileOutputStream("E:\" + filename);
        
        InputStream in = rs.getBinaryStream("data");
        IOUtils.copy(in, out);*/
    }
}

批处理

public class Demo {
    public void fun1() throws Exception{
        Connection con = JdbcUtils.getConnection();
        Statement stmt = con.createStatement();
        for (int i = 0; i <10000; i++) {
            
            String name = "stu_name"+i;
            int age = 10+i;
            String number = "stu"+i;
            String gender = i%2==0 ? "男":"女";
            
            String sql = "insert into student values('"+name+"','"+number+"','"+gender+"','"+age+"')";
            stmt.addBatch(sql);
        }
        stmt.executeBatch();
    }
    @Test
    public void fun2() throws Exception{
        Connection con = JdbcUtils.getConnection();
        String sql = "insert into student values(?,?,?,?)";
        PreparedStatement pstmt = con.prepareStatement(sql);
        for (int i = 0; i < 1000; i++) {
            pstmt.setString(1, "stu_name"+i);
            pstmt.setString(2, "PreparedStatement_number"+i);
            pstmt.setString(3, i%2==0 ? "男":"女");
            pstmt.setInt(4, i);
            pstmt.addBatch();
        }
        pstmt.executeBatch();
    }
}

事务

首先准备一个账户直接操作数据库

public class JdbcUtils {
    // 配置文件的默认配置！要求你必须给出c3p0-config.xml！！！
    private static ComboPooledDataSource dataSource = new ComboPooledDataSource();
    
    // 它是事务专用连接！
    private static ThreadLocal<Connection> tl = new ThreadLocal<Connection>();
    //使用连接池返回一个连接对象
    public static Connection getConnection() throws SQLException {
        Connection con = tl.get();
        // 当con不等于null，说明已经调用过beginTransaction()，表示开启了事务！
        if(con != null) return con;
        return dataSource.getConnection();
    }
    
    //返回连接池对象！
    public static DataSource getDataSource() {
        return dataSource;
    }
    /**
     * 开启事务
     * 1. 获取一个Connection，设置它的setAutoComnmit(false)
     * 2. 还要保证dao中使用的连接是我们刚刚创建的！
     * --------------
     * 1. 创建一个Connection，设置为手动提交
     * 2. 把这个Connection给dao用！
     * 3. 还要让commitTransaction或rollbackTransaction可以获取到！
     * @throws SQLException 
     */
    public static void beginTransaction() throws SQLException {
        Connection con = tl.get();
        if(con != null) throw new SQLException("已经开启了事务，就不要重复开启了！");
        /*
         * 1. 给con赋值！
         * 2. 给con设置为手动提交！
         */
        con = getConnection();//给con赋值，表示事务已经开始了
        con.setAutoCommit(false);
        
        tl.set(con);//把当前线程的连接保存起来！
    }
     //提交事务
     //1. 获取beginTransaction提供的Connection，然后调用commit方法
    public static void commitTransaction() throws SQLException {
        Connection con = tl.get();//获取当前线程的专用连接
        if(con == null) throw new SQLException("还没有开启事务，不能提交！");
        /*
         * 1. 直接使用con.commit()
         */
        con.commit();
        con.close();
        // 把它设置为null，表示事务已经结束了！下次再去调用getConnection()返回的就不是con了
        tl.remove();//从tl中移除连接
    }
     //提交事务
     //1. 获取beginTransaction提供的Connection，然后调用rollback方法
    public static void rollbackTransaction() throws SQLException {
        Connection con = tl.get();
        if(con == null) throw new SQLException("还没有开启事务，不能回滚！");
        /*
         * 1. 直接使用con.rollback()
         */
        con.rollback();
        con.close();
        tl.remove();
    }
    //释放连接　
    public static void releaseConnection(Connection connection) throws SQLException {
        Connection con = tl.get();
        /*
         * 判断它是不是事务专用，如果是，就不关闭！
         * 如果不是事务专用，那么就要关闭！
         */
        // 如果con == null，说明现在没有事务，那么connection一定不是事务专用的！
        if(con == null) connection.close();
        // 如果con != null，说明有事务，那么需要判断参数连接是否与con相等，若不等，说明参数连接不是事务专用连接
        if(con != connection) connection.close();
    }
}

 judi略