预编译sql

package JDBC;

import java.io.InputStream;
import java.sql.Connection;
import java.sql.DriverManager;
import java.util.Properties;

/*
* 改进DBUtil,使得connection不需要传参
* */
public class DBUtil2 {
    //数据库驱动
    private static String driver;
    //连接数据库的路径
    private static String url;
    //连接数据库的用户名
    private static String user;
    //连接数据库的密码
    private static String pwd;
    //用于管理不同线程所获取的连接
    private static ThreadLocal<Connection> threadLocal = new ThreadLocal<Connection>();

    //静态块：类被虚拟机加载时执行一次
    static {
        try {
            //读取配置文件
            Properties properties = new Properties();

            //更加推荐的相对路径写法
            InputStream inputStream = JDBCDemon4.class.getClassLoader()
                    .getResourceAsStream("JDBC/config.properties");
            properties.load(inputStream);
            driver = properties.getProperty("driver").trim();
            url = properties.getProperty("url").trim();
            pwd = properties.getProperty("pwd").trim();
            user = properties.getProperty("user").trim();
//            System.out.println("Driver:" + driver);
//            System.out.println("user:" + user);
//            System.out.println("url:" + url);
//            System.out.println("pwd:" + pwd);
            inputStream.close();
            //获取驱动
            Class.forName(driver);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    /**
     * 获取一个连接
     */
    public static Connection getConnection() throws Exception{
        try {
            /*
             * 通过DriverManager创建一个数据库连接并返回
             * */
            Connection connection =  DriverManager.getConnection(url,user,pwd);
            /*
             * ThreadLocal的set方法会将当前线程作为key
             * 并将给定的值作为value存入内部的map中保存
             * */
            threadLocal.set(connection);
            return connection;
        } catch (Exception e) {
            e.printStackTrace();
            //通知调用者，创建连接出错
            throw e;
        }
    }

    /**
     *  关闭给定的连接
     */
    public static void closeConnection(){
        try{
            //在ThreadLocal中获取connection即（value值）
            Connection connection = threadLocal.get();
            if(connection != null){
                connection.close();
                //删除value值，防止污染
                threadLocal.remove();
            }
        }catch (Exception e){
            e.printStackTrace();
        }
    }
}

package JDBC;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.Statement;

/**
 * Statment主要用于执行静态的sql语句，，内容不变的sql，每执行一次都要对sql语句进行编译
 *
 *  sql语句中只是其中参数有所不同，则适用于preparedStament,sql语句提前编译
 *  继承与Statment，其中execute，executeQuery，executeUpdate被更改，不需要参数
 * */

//使用预编译sql提高执行效率
public class JDBCPreSta1 {
    public static void main(String[] args) {
        try{
            //建立连接
            Connection connection = DBUtil2.getConnection();
 /*
 * 使用preparedAtatment，预编译sql
 * */
//            String sql = "insert into user_demon values (?,?,'123456',?,?)";
//            //System.out.println(sql);
//            PreparedStatement preparedStatement = connection.prepareStatement(sql);
//            //记录开始时间
//            long start = System.currentTimeMillis();
//            for(int i = 2000;i < 2100;i++){
//                preparedStatement.setInt(1,i);
//                preparedStatement.setString(2,"test"+i);
//                preparedStatement.setInt(3,5000);
//                preparedStatement.setString(4,"test"+i+"qq.com");
//                preparedStatement.executeUpdate();
//            }
//            //结束时间
//            long end = System.currentTimeMillis();
//            //输出插入完毕总耗时
//            System.out.println("执行完毕，耗时："+(end - start) +"秒");


/*
* 使用Statment未经过预编译的sql
* */
            //获取Statment
            Statement statement = connection.createStatement();
            long start = System.currentTimeMillis();
            for(int i = 3000;i <3100;i++){
                //String sql = "insert into user_demon values(1,'test"+i+"','12345',5000,'test"+i+"@qq.com')";
                String sql ="insert into user_demon " +
                        "values " +
                        "("+i+","+
                        "'test"+i+"',"+
                        "'12345',"+
                        "5000,"+
                        "'test"+i+"@qq.com'" +
                        ")";
                statement.executeUpdate(sql);
            }
            long end = System.currentTimeMillis();
            System.out.println("执行完毕，耗时："+(end - start) +"秒");
        }catch (Exception e){
            e.printStackTrace();
        }finally {
            DBUtil2.closeConnection();
        }
    }
}