JDBC的学习--尚硅谷

 

 

1.数据库的连接

/**
     * DriverManager 是驱动的管理类.
     * 1). 可以通过重载的 getConnection() 方法获取数据库连接. 较为方便
     * 2). 可以同时管理多个驱动程序: 若注册了多个数据库连接, 则调用 getConnection()
     * 方法时传入的参数不同, 即返回不同的数据库连接。
     * @throws Exception
     */



@Test
    public void testGetConnection2() throws Exception{
        System.out.println(getConnection2());
    }

    public Connection getConnection2() throws Exception{
        //1. 准备连接数据库的 4 个字符串.
        //1). 创建 Properties 对象
        Properties properties = new Properties();

        //2). 获取 jdbc.properties 对应的输入流
        InputStream in =
                this.getClass().getClassLoader().getResourceAsStream("jdbc.properties");

        //3). 加载 2） 对应的输入流
        properties.load(in);

        //4). 具体决定 user, password 等4 个字符串.
        String user = properties.getProperty("user");
        String password = properties.getProperty("password");
        String jdbcUrl = properties.getProperty("jdbcUrl");
        String driver = properties.getProperty("driver");

        //2. 加载数据库驱动程序(对应的 Driver 实现类中有注册驱动的静态代码块.)
        Class.forName(driver);

        //3. 通过 DriverManager 的 getConnection() 方法获取数据库连接.
        return DriverManager.getConnection(jdbcUrl, user, password);
    }

2.statement 和prepareStatement

@Test
public void testPreparedStatement() {
    Connection connection = null;
    PreparedStatement preparedStatement = null;

    try {
        connection = JDBCTools.getConnection();
        String sql = "INSERT INTO customers (name, email, birth) "
                + "VALUES(?,?,?)";

        preparedStatement = connection.prepareStatement(sql);
        preparedStatement.setString(1, "ATGUIGU");
        preparedStatement.setString(2, "simpleit@163.com");
        preparedStatement.setDate(3,
                new Date(new java.util.Date().getTime()));

        preparedStatement.executeUpdate();
    } catch (Exception e) {
        e.printStackTrace();
    } finally {
        JDBCTools.releaseDB(null, preparedStatement, connection);
    }
}

/**
 * SQL 注入.
 */
@Test
public void testSQLInjection() {
    String username = "a' OR PASSWORD = ";
    String password = " OR '1'='1";

    String sql = "SELECT * FROM users WHERE username = '" + username
            + "' AND " + "password = '" + password + "'";

    System.out.println(sql);

    Connection connection = null;
    Statement statement = null;
    ResultSet resultSet = null;

    try {
        connection = JDBCTools.getConnection();
        statement = connection.createStatement();
        resultSet = statement.executeQuery(sql);

        if (resultSet.next()) {
            System.out.println("登录成功!");
        } else {
            System.out.println("用户名和密码不匹配或用户名不存在. ");
        }

    } catch (Exception e) {
        e.printStackTrace();
    } finally {
        JDBCTools.releaseDB(resultSet, statement, connection);
    }
}

3.JDBCTools

package com.atguigu.jdbc;

import java.io.IOException;
import java.io.InputStream;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Properties;

public class JDBCTools {

    /**
     * 执行 SQL 语句, 使用 PreparedStatement
     * @param sql
     * @param args: 填写 SQL 占位符的可变参数
     */
    public static void update(String sql, Object ... args){
        Connection connection = null;
        PreparedStatement preparedStatement = null;

        try {
            connection = JDBCTools.getConnection();
            preparedStatement = connection.prepareStatement(sql);

            for(int i = 0; i < args.length; i++){
                preparedStatement.setObject(i + 1, args[i]);
            }

            preparedStatement.executeUpdate();

        } catch (Exception e) {
            e.printStackTrace();
        } finally{
            JDBCTools.releaseDB(null, preparedStatement, connection);
        }
    }

    /**
     * 执行 SQL 的方法
     *
     * @param sql: insert, update 或 delete。 而不包含 select
     */
    public static void update(String sql) {
        Connection connection = null;
        Statement statement = null;

        try {
            // 1. 获取数据库连接
            connection = getConnection();

            // 2. 调用 Connection 对象的 createStatement() 方法获取 Statement 对象
            statement = connection.createStatement();

            // 4. 发送 SQL 语句: 调用 Statement 对象的 executeUpdate(sql) 方法
            statement.executeUpdate(sql);

        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            // 5. 关闭数据库资源: 由里向外关闭.
            releaseDB(null, statement, connection);
        }
    }

    /**
     * 释放数据库资源的方法
     *
     * @param resultSet
     * @param statement
     * @param connection
     */
    public static void releaseDB(ResultSet resultSet, Statement statement,
            Connection connection) {

        if (resultSet != null) {
            try {
                resultSet.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }

        if (statement != null) {
            try {
                statement.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }

        if (connection != null) {
            try {
                connection.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }

    }

    /**
     * 获取数据库连接的方法
     */
    public static Connection getConnection() throws IOException,
            ClassNotFoundException, SQLException {
        // 0. 读取 jdbc.properties
        /**
         * 1). 属性文件对应 Java 中的 Properties 类 2). 可以使用类加载器加载 bin 目录(类路径下)的文件
         */
        Properties properties = new Properties();
        InputStream inStream = ReviewTest.class.getClassLoader()
                .getResourceAsStream("jdbc.properties");
        properties.load(inStream);

        // 1. 准备获取连接的 4 个字符串: user, password, jdbcUrl, driverClass
        String user = properties.getProperty("user");
        String password = properties.getProperty("password");
        String jdbcUrl = properties.getProperty("jdbcUrl");
        String driverClass = properties.getProperty("driverClass");

        // 2. 加载驱动: Class.forName(driverClass)
        Class.forName(driverClass);

        // 3. 调用
        // DriverManager.getConnection(jdbcUrl, user, password)
        // 获取数据库连接
        Connection connection = DriverManager.getConnection(jdbcUrl, user,
                password);
        return connection;
    }

}

4.DAO

package com.atguigu.jdbc;

import java.lang.reflect.InvocationTargetException;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

import org.apache.commons.beanutils.BeanUtils;

public class DAO {

    // INSERT, UPDATE, DELETE 操作都可以包含在其中
    public void update(String sql, Object... args) {
        Connection connection = null;
        PreparedStatement preparedStatement = null;

        try {
            connection = JDBCTools.getConnection();
            preparedStatement = connection.prepareStatement(sql);

            for (int i = 0; i < args.length; i++) {
                preparedStatement.setObject(i + 1, args[i]);
            }

            preparedStatement.executeUpdate();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            JDBCTools.releaseDB(null, preparedStatement, connection);
        }
    }

    // 查询一条记录, 返回对应的对象
    public <T> T get(Class<T> clazz, String sql, Object... args) {
        List<T> result = getForList(clazz, sql, args);
        if(result.size() > 0){
            return result.get(0);
        }

        return null;
    }

    /**
     * 传入 SQL 语句和 Class 对象, 返回 SQL 语句查询到的记录对应的 Class 类的对象的集合
     * @param clazz: 对象的类型
     * @param sql: SQL 语句
     * @param args: 填充 SQL 语句的占位符的可变参数.
     * @return
     */
    public <T> List<T> getForList(Class<T> clazz,
            String sql, Object... args) {

        List<T> list = new ArrayList<>();

        Connection connection = null;
        PreparedStatement preparedStatement = null;
        ResultSet resultSet = null;

        try {
            //1. 得到结果集
            connection = JDBCTools.getConnection();
            preparedStatement = connection.prepareStatement(sql);

            for (int i = 0; i < args.length; i++) {
                preparedStatement.setObject(i + 1, args[i]);
            }

            resultSet = preparedStatement.executeQuery();

            //2. 处理结果集, 得到 Map 的 List, 其中一个 Map 对象
            //就是一条记录. Map 的 key 为 reusltSet 中列的别名, Map 的 value
            //为列的值.
            List<Map<String, Object>> values =
                    handleResultSetToMapList(resultSet);

            //3. 把 Map 的 List 转为 clazz 对应的 List
            //其中 Map 的 key 即为 clazz 对应的对象的 propertyName,
            //而 Map 的 value 即为 clazz 对应的对象的 propertyValue
            list = transfterMapListToBeanList(clazz, values);

        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            JDBCTools.releaseDB(resultSet, preparedStatement, connection);
        }

        return list;
    }

    public <T> List<T> transfterMapListToBeanList(Class<T> clazz,
            List<Map<String, Object>> values) throws InstantiationException,
            IllegalAccessException, InvocationTargetException {

        List<T> result = new ArrayList<>();

        T bean = null;

        if (values.size() > 0) {
            for (Map<String, Object> m : values) {
                bean = clazz.newInstance();
                for (Map.Entry<String, Object> entry : m.entrySet()) {
                    String propertyName = entry.getKey();
                    Object value = entry.getValue();

                    BeanUtils.setProperty(bean, propertyName, value);
                }
                // 13. 把 Object 对象放入到 list 中.
                result.add(bean);
            }
        }

        return result;
    }

    /**
     * 处理结果集, 得到 Map 的一个 List, 其中一个 Map 对象对应一条记录
     *
     * @param resultSet
     * @return
     * @throws SQLException
     */
    public List<Map<String, Object>> handleResultSetToMapList(
            ResultSet resultSet) throws SQLException {
        // 5. 准备一个 List<Map<String, Object>>:
        // 键: 存放列的别名, 值: 存放列的值. 其中一个 Map 对象对应着一条记录
        List<Map<String, Object>> values = new ArrayList<>();

        List<String> columnLabels = getColumnLabels(resultSet);
        Map<String, Object> map = null;

        // 7. 处理 ResultSet, 使用 while 循环
        while (resultSet.next()) {
            map = new HashMap<>();

            for (String columnLabel : columnLabels) {
                Object value = resultSet.getObject(columnLabel);
                map.put(columnLabel, value);
            }

            // 11. 把一条记录的一个 Map 对象放入 5 准备的 List 中
            values.add(map);
        }
        return values;
    }

    /**
     * 获取结果集的 ColumnLabel 对应的 List
     *
     * @param rs
     * @return
     * @throws SQLException
     */
    private List<String> getColumnLabels(ResultSet rs) throws SQLException {
        List<String> labels = new ArrayList<>();

        ResultSetMetaData rsmd = rs.getMetaData();
        for (int i = 0; i < rsmd.getColumnCount(); i++) {
            labels.add(rsmd.getColumnLabel(i + 1));
        }

        return labels;
    }

    // 返回某条记录的某一个字段的值 或 一个统计的值(一共有多少条记录等.)
    public <E> E getForValue(String sql, Object... args) {

        //1. 得到结果集: 该结果集应该只有一行, 且只有一列
        Connection connection = null;
        PreparedStatement preparedStatement = null;
        ResultSet resultSet = null;

        try {
            //1. 得到结果集
            connection = JDBCTools.getConnection();
            preparedStatement = connection.prepareStatement(sql);

            for (int i = 0; i < args.length; i++) {
                preparedStatement.setObject(i + 1, args[i]);
            }

            resultSet = preparedStatement.executeQuery();

            if(resultSet.next()){
                return (E) resultSet.getObject(1);
            }
        } catch(Exception ex){
            ex.printStackTrace();
        } finally{
            JDBCTools.releaseDB(resultSet, preparedStatement, connection);
        }
        //2. 取得结果

        return null;
    }

}

5.事务和事务的隔离级别

package com.atguigu.jdbc;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

import org.junit.Test;

public class TransactionTest {

    /**
     * 测试事务的隔离级别 在 JDBC 程序中可以通过 Connection 的 setTransactionIsolation 来设置事务的隔离级别.
     */
    @Test
    public void testTransactionIsolationUpdate() {

        Connection connection = null;

        try {
            connection = JDBCTools.getConnection();
            connection.setAutoCommit(false);

            String sql = "UPDATE users SET balance = "
                    + "balance - 500 WHERE id = 1";
            update(connection, sql);

            connection.commit();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {

        }
    }

    @Test
    public void testTransactionIsolationRead() {
        String sql = "SELECT balance FROM users WHERE id = 1";
        Integer balance = getForValue(sql);
        System.out.println(balance);
    }

    // 返回某条记录的某一个字段的值 或 一个统计的值(一共有多少条记录等.)
    public <E> E getForValue(String sql, Object... args) {

        // 1. 得到结果集: 该结果集应该只有一行, 且只有一列
        Connection connection = null;
        PreparedStatement preparedStatement = null;
        ResultSet resultSet = null;

        try {
            // 1. 得到结果集
            connection = JDBCTools.getConnection();
            System.out.println(connection.getTransactionIsolation());

//          connection.setTransactionIsolation(Connection.TRANSACTION_READ_UNCOMMITTED);
            connection.setTransactionIsolation(Connection.TRANSACTION_READ_COMMITTED);

            preparedStatement = connection.prepareStatement(sql);

            for (int i = 0; i < args.length; i++) {
                preparedStatement.setObject(i + 1, args[i]);
            }

            resultSet = preparedStatement.executeQuery();

            if (resultSet.next()) {
                return (E) resultSet.getObject(1);
            }
        } catch (Exception ex) {
            ex.printStackTrace();
        } finally {
            JDBCTools.releaseDB(resultSet, preparedStatement, connection);
        }
        // 2. 取得结果

        return null;
    }

    /**
     * Tom 给 Jerry 汇款 500 元.
     *
     * 关于事务: 1. 如果多个操作, 每个操作使用的是自己的单独的连接, 则无法保证事务. 2. 具体步骤: 1). 事务操作开始前, 开始事务:
     * 取消 Connection 的默认提交行为. connection.setAutoCommit(false); 2). 如果事务的操作都成功,
     * 则提交事务: connection.commit(); 3). 回滚事务: 若出现异常, 则在 catch 块中回滚事务:
     */
    @Test
    public void testTransaction() {

        Connection connection = null;

        try {

            connection = JDBCTools.getConnection();
            System.out.println(connection.getAutoCommit());

            // 开始事务: 取消默认提交.
            connection.setAutoCommit(false);

            String sql = "UPDATE users SET balance = "
                    + "balance - 500 WHERE id = 1";
            update(connection, sql);

            int i = 10 / 0;
            System.out.println(i);

            sql = "UPDATE users SET balance = " + "balance + 500 WHERE id = 2";
            update(connection, sql);

            // 提交事务
            connection.commit();
        } catch (Exception e) {
            e.printStackTrace();

            // 回滚事务
            try {
                connection.rollback();
            } catch (SQLException e1) {
                e1.printStackTrace();
            }
        } finally {
            JDBCTools.releaseDB(null, null, connection);
        }

        /*
         * try {
         *
         * //开始事务: 取消默认提交. connection.setAutoCommit(false);
         *
         * //...
         *
         * //提交事务 connection.commit(); } catch (Exception e) { //...
         *
         * //回滚事务 try { connection.rollback(); } catch (SQLException e1) {
         * e1.printStackTrace(); } } finally{ JDBCTools.releaseDB(null, null,
         * connection); }
         */

        // DAO dao = new DAO();
        //
        // String sql = "UPDATE users SET balance = " +
        // "balance - 500 WHERE id = 1";
        // dao.update(sql);
        //
        // int i = 10 / 0;
        // System.out.println(i);
        //
        // sql = "UPDATE users SET balance = " +
        // "balance + 500 WHERE id = 2";
        // dao.update(sql);

    }

    public void update(Connection connection, String sql, Object... args) {
        PreparedStatement preparedStatement = null;

        try {
            preparedStatement = connection.prepareStatement(sql);

            for (int i = 0; i < args.length; i++) {
                preparedStatement.setObject(i + 1, args[i]);
            }

            preparedStatement.executeUpdate();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            JDBCTools.releaseDB(null, preparedStatement, null);
        }
    }

}

6.批量处理sql语句

@Test
public void testBatch(){
    Connection connection = null;
    PreparedStatement preparedStatement = null;
    String sql = null;

    try {
        connection = JDBCTools.getConnection();
        JDBCTools.beginTx(connection);
        sql = "INSERT INTO customers VALUES(?,?,?)";
        preparedStatement = connection.prepareStatement(sql);
        Date date = new Date(new java.util.Date().getTime());

        long begin = System.currentTimeMillis();
        for(int i = 0; i < 100000; i++){
            preparedStatement.setInt(1, i + 1);
            preparedStatement.setString(2, "name_" + i);
            preparedStatement.setDate(3, date);

            //"积攒" SQL
            preparedStatement.addBatch();

            //当 "积攒" 到一定程度, 就统一的执行一次. 并且清空先前 "积攒" 的 SQL
            if((i + 1) % 300 == 0){
                preparedStatement.executeBatch();
                preparedStatement.clearBatch();
            }
        }

        //若总条数不是批量数值的整数倍, 则还需要再额外的执行一次.
        if(100000 % 300 != 0){
            preparedStatement.executeBatch();
            preparedStatement.clearBatch();
        }

        long end = System.currentTimeMillis();

        System.out.println("Time: " + (end - begin)); //569

        JDBCTools.commit(connection);
    } catch (Exception e) {
        e.printStackTrace();
        JDBCTools.rollback(connection);
    } finally{
        JDBCTools.releaseDB(null, preparedStatement, connection);
    }
}

7.DBCP和C3P0数据库连接池的使用（非配置文件和配置文件）

package com.atguigu.jdbc;

import java.beans.PropertyVetoException;
import java.io.InputStream;
import java.sql.Connection;
import java.sql.Date;
import java.sql.PreparedStatement;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Properties;

import javax.sql.DataSource;

import org.apache.commons.dbcp.BasicDataSource;
import org.apache.commons.dbcp.BasicDataSourceFactory;
import org.junit.Test;

import com.mchange.v2.c3p0.ComboPooledDataSource;

public class JDBCTest {

    @Test
    public void testJdbcTools() throws Exception{
        Connection connection = JDBCTools.getConnection();
        System.out.println(connection);
    }

    /**
     * 1. 创建 c3p0-config.xml 文件,
     * 参考帮助文档中 Appendix B: Configuation Files 的内容
     * 2. 创建 ComboPooledDataSource 实例；
     * DataSource dataSource =
     *          new ComboPooledDataSource("helloc3p0");
     * 3. 从 DataSource 实例中获取数据库连接.
     */
    @Test
    public void testC3poWithConfigFile() throws Exception{
        DataSource dataSource =
                new ComboPooledDataSource("helloc3p0");

        System.out.println(dataSource.getConnection());

        ComboPooledDataSource comboPooledDataSource =
                (ComboPooledDataSource) dataSource;
        System.out.println(comboPooledDataSource.getMaxStatements());
    }

    @Test
    public void testC3P0() throws Exception{
        ComboPooledDataSource cpds = new ComboPooledDataSource();
        cpds.setDriverClass( "com.mysql.jdbc.Driver" ); //loads the jdbc driver
        cpds.setJdbcUrl( "jdbc:mysql:///atguigu" );
        cpds.setUser("root");
        cpds.setPassword("1230");

        System.out.println(cpds.getConnection());
    }

    /**
     * 1. 加载 dbcp 的 properties 配置文件: 配置文件中的键需要来自 BasicDataSource
     * 的属性.
     * 2. 调用 BasicDataSourceFactory 的 createDataSource 方法创建 DataSource
     * 实例
     * 3. 从 DataSource 实例中获取数据库连接.
     */
    @Test
    public void testDBCPWithDataSourceFactory() throws Exception{

        Properties properties = new Properties();
        InputStream inStream = JDBCTest.class.getClassLoader()
                .getResourceAsStream("dbcp.properties");
        properties.load(inStream);

        DataSource dataSource =
                BasicDataSourceFactory.createDataSource(properties);

        System.out.println(dataSource.getConnection());

//      BasicDataSource basicDataSource =
//              (BasicDataSource) dataSource;
//
//      System.out.println(basicDataSource.getMaxWait());
    }

    /**
     * 使用 DBCP 数据库连接池
     * 1. 加入 jar 包(2 个jar 包). 依赖于 Commons Pool
     * 2. 创建数据库连接池
     * 3. 为数据源实例指定必须的属性
     * 4. 从数据源中获取数据库连接
     * @throws SQLException
     */
    @Test
    public void testDBCP() throws SQLException{
        final BasicDataSource dataSource = new BasicDataSource();

        //2. 为数据源实例指定必须的属性
        dataSource.setUsername("root");
        dataSource.setPassword("1230");
        dataSource.setUrl("jdbc:mysql:///atguigu");
        dataSource.setDriverClassName("com.mysql.jdbc.Driver");

        //3. 指定数据源的一些可选的属性.
        //1). 指定数据库连接池中初始化连接数的个数
        dataSource.setInitialSize(5);

        //2). 指定最大的连接数: 同一时刻可以同时向数据库申请的连接数
        dataSource.setMaxActive(5);

        //3). 指定小连接数: 在数据库连接池中保存的最少的空闲连接的数量
        dataSource.setMinIdle(2);

        //4).等待数据库连接池分配连接的最长时间. 单位为毫秒. 超出该时间将抛出异常.
        dataSource.setMaxWait(1000 * 5);

        //4. 从数据源中获取数据库连接
        Connection connection = dataSource.getConnection();
        System.out.println(connection.getClass());

        connection = dataSource.getConnection();
        System.out.println(connection.getClass());

        connection = dataSource.getConnection();
        System.out.println(connection.getClass());

        connection = dataSource.getConnection();
        System.out.println(connection.getClass());

        Connection connection2 = dataSource.getConnection();
        System.out.println(">" + connection2.getClass());

        new Thread(){
            public void run() {
                Connection conn;
                try {
                    conn = dataSource.getConnection();
                    System.out.println(conn.getClass());
                } catch (SQLException e) {
                    e.printStackTrace();
                }
            };
        }.start();

        try {
            Thread.sleep(5500);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }

        connection2.close();
    }

    @Test
    public void testBatch(){
        Connection connection = null;
        PreparedStatement preparedStatement = null;
        String sql = null;

        try {
            connection = JDBCTools.getConnection();
            JDBCTools.beginTx(connection);
            sql = "INSERT INTO customers VALUES(?,?,?)";
            preparedStatement = connection.prepareStatement(sql);
            Date date = new Date(new java.util.Date().getTime());

            long begin = System.currentTimeMillis();
            for(int i = 0; i < 100000; i++){
                preparedStatement.setInt(1, i + 1);
                preparedStatement.setString(2, "name_" + i);
                preparedStatement.setDate(3, date);

                //"积攒" SQL
                preparedStatement.addBatch();

                //当 "积攒" 到一定程度, 就统一的执行一次. 并且清空先前 "积攒" 的 SQL
                if((i + 1) % 300 == 0){
                    preparedStatement.executeBatch();
                    preparedStatement.clearBatch();
                }
            }

            //若总条数不是批量数值的整数倍, 则还需要再额外的执行一次.
            if(100000 % 300 != 0){
                preparedStatement.executeBatch();
                preparedStatement.clearBatch();
            }

            long end = System.currentTimeMillis();

            System.out.println("Time: " + (end - begin)); //569

            JDBCTools.commit(connection);
        } catch (Exception e) {
            e.printStackTrace();
            JDBCTools.rollback(connection);
        } finally{
            JDBCTools.releaseDB(null, preparedStatement, connection);
        }
    }


    @Test
    public void testBatchWithPreparedStatement(){
        Connection connection = null;
        PreparedStatement preparedStatement = null;
        String sql = null;

        try {
            connection = JDBCTools.getConnection();
            JDBCTools.beginTx(connection);
            sql = "INSERT INTO customers VALUES(?,?,?)";
            preparedStatement = connection.prepareStatement(sql);
            Date date = new Date(new java.util.Date().getTime());

            long begin = System.currentTimeMillis();
            for(int i = 0; i < 100000; i++){
                preparedStatement.setInt(1, i + 1);
                preparedStatement.setString(2, "name_" + i);
                preparedStatement.setDate(3, date);

                preparedStatement.executeUpdate();
            }
            long end = System.currentTimeMillis();

            System.out.println("Time: " + (end - begin)); //9819

            JDBCTools.commit(connection);
        } catch (Exception e) {
            e.printStackTrace();
            JDBCTools.rollback(connection);
        } finally{
            JDBCTools.releaseDB(null, preparedStatement, connection);
        }
    }

    /**
     * 向  Oracle 的 customers 数据表中插入 10 万条记录
     * 测试如何插入, 用时最短.
     * 1. 使用 Statement.
     */
    @Test
    public void testBatchWithStatement(){
        Connection connection = null;
        Statement statement = null;
        String sql = null;

        try {
            connection = JDBCTools.getConnection();
            JDBCTools.beginTx(connection);

            statement = connection.createStatement();

            long begin = System.currentTimeMillis();
            for(int i = 0; i < 100000; i++){
                sql = "INSERT INTO customers VALUES(" + (i + 1)
                        + ", 'name_" + i + "', '29-6月 -13')";
                statement.addBatch(sql);
            }
            long end = System.currentTimeMillis();

            System.out.println("Time: " + (end - begin)); //39567

            JDBCTools.commit(connection);
        } catch (Exception e) {
            e.printStackTrace();
            JDBCTools.rollback(connection);
        } finally{
            JDBCTools.releaseDB(null, statement, connection);
        }
    }

}

8.DBUtils使用

package com.atguigu.jdbc;

import java.sql.Connection;
import java.sql.Date;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;

import org.apache.commons.dbutils.QueryRunner;
import org.apache.commons.dbutils.ResultSetHandler;
import org.apache.commons.dbutils.handlers.BeanHandler;
import org.apache.commons.dbutils.handlers.BeanListHandler;
import org.apache.commons.dbutils.handlers.MapHandler;
import org.apache.commons.dbutils.handlers.MapListHandler;
import org.apache.commons.dbutils.handlers.ScalarHandler;
import org.junit.Test;

public class DBUtilsTest {



    /**
     * ScalarHandler: 把结果集转为一个数值(可以是任意基本数据类型和字符串， Date 等)返回
     */
    @Test
    public void testScalarHandler(){
        Connection connection = null;

        try {
            connection = JDBCTools.getConnection();
            String sql = "SELECT name, email " +
                    "FROM customers";

            Object result = queryRunner.query(connection,
                    sql, new ScalarHandler());

            System.out.println(result);
        } catch (Exception e) {
            e.printStackTrace();
        } finally{
            JDBCTools.releaseDB(null, null, connection);
        }
    }

    /**
     * MapListHandler: 将结果集转为一个 Map 的 List
     * Map 对应查询的一条记录: 键: SQL 查询的列名(不是列的别名), 值: 列的值.
     * 而 MapListHandler: 返回的多条记录对应的 Map 的集合.
     */
    @Test
    public void testMapListHandler(){
        Connection connection = null;

        try {
            connection = JDBCTools.getConnection();
            String sql = "SELECT id, name, email, birth " +
                    "FROM customers";

            List<Map<String, Object>> result = queryRunner.query(connection,
                    sql, new MapListHandler());

            System.out.println(result);
        } catch (Exception e) {
            e.printStackTrace();
        } finally{
            JDBCTools.releaseDB(null, null, connection);
        }
    }

    /**
     * MapHandler: 返回 SQL 对应的第一条记录对应的 Map 对象.
     * 键: SQL 查询的列名(不是列的别名), 值: 列的值.
     */
    @Test
    public void testMapHandler(){
        Connection connection = null;

        try {
            connection = JDBCTools.getConnection();
            String sql = "SELECT id, name, email, birth " +
                    "FROM customers";

            Map<String, Object> result = queryRunner.query(connection,
                    sql, new MapHandler());

            System.out.println(result);
        } catch (Exception e) {
            e.printStackTrace();
        } finally{
            JDBCTools.releaseDB(null, null, connection);
        }
    }

    /**
     * BeanListHandler: 把结果集转为一个 List, 该 List 不为 null, 但可能为
     * 空集合(size() 方法返回 0)
     * 若 SQL 语句的确能够查询到记录, List 中存放创建 BeanListHandler 传入的 Class
     * 对象对应的对象.
     */
    @Test
    public void testBeanListHandler(){
        Connection connection = null;

        try {
            connection = JDBCTools.getConnection();
            String sql = "SELECT id, name, email, birth " +
                    "FROM customers";

            List<Customer> customers = queryRunner.query(connection,
                    sql, new BeanListHandler(Customer.class));

            System.out.println(customers);
        } catch (Exception e) {
            e.printStackTrace();
        } finally{
            JDBCTools.releaseDB(null, null, connection);
        }
    }

    /**
     * BeanHandler: 把结果集的第一条记录转为创建 BeanHandler 对象时传入的 Class
     * 参数对应的对象.
     */
    @Test
    public void testBeanHanlder(){
        Connection connection = null;

        try {
            connection = JDBCTools.getConnection();
            String sql = "SELECT id, name customerName, email, birth " +
                    "FROM customers WHERE id >= ?";

            Customer customer = queryRunner.query(connection,
                    sql, new BeanHandler(Customer.class), 5);

            System.out.println(customer);
        } catch (Exception e) {
            e.printStackTrace();
        } finally{
            JDBCTools.releaseDB(null, null, connection);
        }
    }

    QueryRunner queryRunner = new QueryRunner();

    class MyResultSetHandler implements ResultSetHandler{

        @Override
        public Object handle(ResultSet resultSet)
                throws SQLException {
//          System.out.println("handle....");
//          return "atguigu";

            List<Customer> customers = new ArrayList<>();

            while(resultSet.next()){
                Integer id = resultSet.getInt(1);
                String name = resultSet.getString(2);
                String email = resultSet.getString(3);
                Date birth = resultSet.getDate(4);

                Customer customer =
                        new Customer(id, name, email, birth);
                customers.add(customer);
            }

            return customers;
        }

    }

    /**
     * QueryRunner 的 query 方法的返回值取决于其 ResultSetHandler 参数的
     * handle 方法的返回值
     *
     */
    @Test
    public void testQuery(){
        Connection connection = null;

        try {
            connection = JDBCTools.getConnection();
            String sql = "SELECT id, name, email, birth " +
                    "FROM customers";
            Object obj = queryRunner.query(connection, sql,
                            new MyResultSetHandler());

            System.out.println(obj);
        } catch (Exception e) {
            e.printStackTrace();
        } finally{
            JDBCTools.releaseDB(null, null, connection);
        }
    }

    @Test
    public void testUpdate(){
        Connection connection = null;

        try {
            connection = JDBCTools.getConnection();
            String sql = "UPDATE customers SET name = ? " +
                    "WHERE id = ?";
            queryRunner.update(connection, sql, "MIKE", 11);
        } catch (Exception e) {
            e.printStackTrace();
        } finally{
            JDBCTools.releaseDB(null, null, connection);
        }
    }

}

9.DAO接口

package com.atguigu.jdbc;

import java.sql.Connection;
import java.sql.SQLException;
import java.util.List;

/**
 * 访问数据的 DAO 接口.
 * 里边定义好访问数据表的各种方法
 * @param T: DAO 处理的实体类的类型.
 */
public interface DAO<T> {

    /**
     * 批量处理的方法
     * @param connection
     * @param sql
     * @param args: 填充占位符的 Object [] 类型的可变参数.
     * @throws SQLException
     */
    void batch(Connection connection,
            String sql, Object [] ... args) throws SQLException;

    /**
     * 返回具体的一个值, 例如总人数, 平均工资, 某一个人的 email 等.
     * @param connection
     * @param sql
     * @param args
     * @return
     * @throws SQLException
     */
    <E> E getForValue(Connection connection,
            String sql, Object ... args) throws SQLException;

    /**
     * 返回 T 的一个集合
     * @param connection
     * @param sql
     * @param args
     * @return
     * @throws SQLException
     */
    List<T> getForList(Connection connection,
            String sql, Object ... args) throws SQLException;

    /**
     * 返回一个 T 的对象
     * @param connection
     * @param sql
     * @param args
     * @return
     * @throws SQLException
     */
    T get(Connection connection, String sql,
            Object ... args) throws SQLException;

    /**
     * INSRET, UPDATE, DELETE
     * @param connection: 数据库连接
     * @param sql: SQL 语句
     * @param args: 填充占位符的可变参数.
     * @throws SQLException
     */
    void update(Connection connection, String sql,
            Object ... args) throws SQLException;

}

10.DAO接口的实现类。（通过DBUtils实现）

package com.atguigu.jdbc;

import java.sql.Connection;
import java.sql.SQLException;
import java.util.List;

import org.apache.commons.dbutils.QueryRunner;
import org.apache.commons.dbutils.handlers.BeanHandler;
import org.apache.commons.dbutils.handlers.BeanListHandler;
import org.apache.commons.dbutils.handlers.ScalarHandler;

/**
 * 使用 QueryRunner 提供其具体的实现
 * @param <T>: 子类需传入的泛型类型.
 */
public class JdbcDaoImpl<T> implements DAO<T> {

    private QueryRunner queryRunner = null;
    private Class<T> type;

    public JdbcDaoImpl() {
        queryRunner = new QueryRunner();
        type = ReflectionUtils.getSuperGenericType(getClass());
    }

    @Override
    public void batch(Connection connection, String sql, Object[]... args) throws SQLException {
        queryRunner.batch(connection, sql, args);
    }

    @Override
    public <E> E getForValue(Connection connection, String sql, Object... args) throws SQLException {
        return (E) queryRunner.query(connection, sql, new ScalarHandler(), args);
    }

    @Override
    public List<T> getForList(Connection connection, String sql, Object... args)
            throws SQLException {
        return queryRunner.query(connection, sql,
                new BeanListHandler<>(type), args);
    }

    @Override
    public T get(Connection connection, String sql, Object... args) throws SQLException {
        return queryRunner.query(connection, sql,
                new BeanHandler<>(type), args);
    }

    @Override
    public void update(Connection connection, String sql, Object... args) throws SQLException {
        queryRunner.update(connection, sql, args);
    }

}

11.DAOImpl的继承类，可以再自己定义操作数据库的方法

package com.atguigu.jdbc;

public class CustomerDao
    extends JdbcDaoImpl<Customer>{

}