数据库连接池Demo（1）单线程初步

简介

在上周阅读Alibaba Druid数据库连接池后，感觉光看有点领会不到精髓，后面这几篇文章将尝试自己实现一个数据库连接池Demo

原生JDBC与Alibaba Druid使用

我们先把相关的测试给搭建起来，把JDBC、Druid的相关示例代码跑起来，看看效果和性能

在实现一个最简单的自定义连接池，然后运行三者进行对比

原生JDBC

我们先使用原生JDBC将数据库数据初始化，然后去查询，代码如下：

public class Main {static final String DB_URL = "jdbc:h2:file:./demo-db";static final String USER = "sa";static final String PASS = "sa";/*** 生成数据*/private static void initData() {final String drop = "drop table `user_example` if exists;";final String createTable = "CREATE TABLE IF NOT EXISTS `user_example` (" +"`id` bigint NOT NULL AUTO_INCREMENT, " +"`name` varchar(100) NOT NULL" +");";final String addUser = "insert into user_example (name) values(%s)";try(Connection conn = DriverManager.getConnection(DB_URL, USER, PASS);Statement stmt = conn.createStatement()) {stmt.execute(drop);stmt.execute(createTable);for (int i=0; i<10; i++) {stmt.execute(String.format(addUser, i));}conn.commit();} catch (SQLException e) {e.printStackTrace();}}
}

然后原始暴力查询：

public class Main {/*** 原生JDBC查询*/private static void rawExample() {for (int i=0; i<queryAmount; i++) {// Open a connectiontry(Connection conn = DriverManager.getConnection(DB_URL, USER, PASS);Statement stmt = conn.createStatement();ResultSet rs = stmt.executeQuery(QUERY);) {// Extract data from result setwhile (rs.next()) {// Retrieve by column nameSystem.out.print("ID: " + rs.getInt("id"));System.out.print(", name: " + rs.getString("name"));System.out.print(";");}System.out.println();} catch (SQLException e) {e.printStackTrace();}}}
}

Alibaba Druid查询

使用Alibaba Druid进行相同的查询操作：

public class Main {/*** Alibaba Druid查询*/private static void druidExample() throws Exception {DruidDataSource dataSource = new DruidDataSource();dataSource.setInitialSize(1);dataSource.setMaxActive(1);dataSource.setMinIdle(1);dataSource.setDriverClassName("org.h2.Driver");dataSource.setUrl(DB_URL);dataSource.setUsername(USER);dataSource.setPassword(PASS);for (int i=0; i<queryAmount; i++) {// Open a connectiontry(Connection conn = dataSource.getConnection();Statement stmt = conn.createStatement();ResultSet rs = stmt.executeQuery(QUERY)) {// Extract data from result setwhile (rs.next()) {// Retrieve by column nameSystem.out.print("ID: " + rs.getInt("id"));System.out.print(", name: " + rs.getString("name"));System.out.print(";");}System.out.println();} catch (SQLException e) {e.printStackTrace();}}}
}

自写最简单版本查询

自定义Database

列出来的就是要进行自己实现，其他方法暂时默认：

在测试代码中，就涉及到一个getConnection函数，以及自定义的连接池复用相关

public class SelfDataSource implements DataSource {/*** 放置空闲可用的连接*/private final Queue<SelfPoolConnection> idle = new LinkedList<>();/*** 放置正在使用的连接*/private final Set<SelfPoolConnection> running = new HashSet<>();private final String url;private final String username;private final String password;public SelfDataSource(final String url, final String username, final String password) {this.url = url;this.username = username;this.password = password;}/*** 初步将Connection从运行池中异常，放入空闲池* 从正在使用连接池中移除，放入空闲连接池中* @param selfPoolConnection 自定义Connection*/public void recycle(final SelfPoolConnection selfPoolConnection) {running.remove(selfPoolConnection);idle.add(selfPoolConnection);System.out.println("回收连接");}/*** 自定义的获取数据库物理连接* 1.无空闲连接则生成新的物理连接，并且放入正在使用连接池中* 2.如果有空闲连接，则获取，并放入正在使用连接池中* @return 自定义的数据库物理连接（自定义以能够自定义Close方法）* @throws SQLException*/@Overridesynchronized public Connection getConnection() throws SQLException {if (idle.isEmpty()) {System.out.println("生成新物理连接");SelfPoolConnection conn = new SelfPoolConnection(this, url, username, password);running.add(conn);return conn.getConnection();}SelfPoolConnection conn = idle.poll();running.add(conn);return conn.getConnection();}
}

自定义Connection

因为在测试代码中，涉及的需要实现的函数如下：

createStatement
close（try自动调用）
getConnection（自定义DataSource调用）

public class SelfPoolConnection implements javax.sql.PooledConnection, Connection {private final SelfDataSource selfDatasource;private Connection connection;public SelfPoolConnection(final SelfDataSource selfDatasource, final String url, final String username, final String password) {this.selfDatasource = selfDatasource;System.out.println("初始化物理连接");try {connection = DriverManager.getConnection(url, username, password);} catch (SQLException e) {e.printStackTrace();}}@Overridepublic Statement createStatement() throws SQLException {return connection.createStatement();}@Overridesynchronized public Connection getConnection() throws SQLException {return this;}/*** 关闭连接，调用自定义DataSource用于复用* 目前感觉这样不规范，但时间紧张，前期先简单实现* @throws SQLException*/@Overridepublic void close() throws SQLException {selfDatasource.recycle(this);}
}

运行对比

运行函数与结果如下：

public class Main {public static void main(String[] args) throws Exception {initData();long current = System.currentTimeMillis();rawExample();System.out.printf("原生查询耗时：%d 毫秒\n", System.currentTimeMillis() - current);current = System.currentTimeMillis();druidExample();System.out.printf("连接池查询耗时：%d 毫秒\n", System.currentTimeMillis() - current);current = System.currentTimeMillis();selfExample();System.out.printf("自写连接池查询耗时：%d 毫秒\n", System.currentTimeMillis() - current);Thread.sleep(3000);}
}

结果：

ID: 1, name: 0;ID: 2, name: 1;ID: 3, name: 2;ID: 4, name: 3;ID: 5, name: 4;ID: 6, name: 5;ID: 7, name: 6;ID: 8, name: 7;ID: 9, name: 8;ID: 10, name: 9;
ID: 1, name: 0;ID: 2, name: 1;ID: 3, name: 2;ID: 4, name: 3;ID: 5, name: 4;ID: 6, name: 5;ID: 7, name: 6;ID: 8, name: 7;ID: 9, name: 8;ID: 10, name: 9;
ID: 1, name: 0;ID: 2, name: 1;ID: 3, name: 2;ID: 4, name: 3;ID: 5, name: 4;ID: 6, name: 5;ID: 7, name: 6;ID: 8, name: 7;ID: 9, name: 8;ID: 10, name: 9;
ID: 1, name: 0;ID: 2, name: 1;ID: 3, name: 2;ID: 4, name: 3;ID: 5, name: 4;ID: 6, name: 5;ID: 7, name: 6;ID: 8, name: 7;ID: 9, name: 8;ID: 10, name: 9;
ID: 1, name: 0;ID: 2, name: 1;ID: 3, name: 2;ID: 4, name: 3;ID: 5, name: 4;ID: 6, name: 5;ID: 7, name: 6;ID: 8, name: 7;ID: 9, name: 8;ID: 10, name: 9;
原生查询耗时：220 毫秒
11月 15, 2021 10:09:04 下午 com.alibaba.druid.pool.DruidDataSource error
严重: testWhileIdle is true, validationQuery not set
11月 15, 2021 10:09:04 下午 com.alibaba.druid.pool.DruidDataSource info
信息: {dataSource-1} inited
ID: 1, name: 0;ID: 2, name: 1;ID: 3, name: 2;ID: 4, name: 3;ID: 5, name: 4;ID: 6, name: 5;ID: 7, name: 6;ID: 8, name: 7;ID: 9, name: 8;ID: 10, name: 9;
ID: 1, name: 0;ID: 2, name: 1;ID: 3, name: 2;ID: 4, name: 3;ID: 5, name: 4;ID: 6, name: 5;ID: 7, name: 6;ID: 8, name: 7;ID: 9, name: 8;ID: 10, name: 9;
ID: 1, name: 0;ID: 2, name: 1;ID: 3, name: 2;ID: 4, name: 3;ID: 5, name: 4;ID: 6, name: 5;ID: 7, name: 6;ID: 8, name: 7;ID: 9, name: 8;ID: 10, name: 9;
ID: 1, name: 0;ID: 2, name: 1;ID: 3, name: 2;ID: 4, name: 3;ID: 5, name: 4;ID: 6, name: 5;ID: 7, name: 6;ID: 8, name: 7;ID: 9, name: 8;ID: 10, name: 9;
ID: 1, name: 0;ID: 2, name: 1;ID: 3, name: 2;ID: 4, name: 3;ID: 5, name: 4;ID: 6, name: 5;ID: 7, name: 6;ID: 8, name: 7;ID: 9, name: 8;ID: 10, name: 9;
连接池查询耗时：69 毫秒
生成新物理连接
初始化物理连接
ID: 1, name: 0;ID: 2, name: 1;ID: 3, name: 2;ID: 4, name: 3;ID: 5, name: 4;ID: 6, name: 5;ID: 7, name: 6;ID: 8, name: 7;ID: 9, name: 8;ID: 10, name: 9;
回收连接
ID: 1, name: 0;ID: 2, name: 1;ID: 3, name: 2;ID: 4, name: 3;ID: 5, name: 4;ID: 6, name: 5;ID: 7, name: 6;ID: 8, name: 7;ID: 9, name: 8;ID: 10, name: 9;
回收连接
ID: 1, name: 0;ID: 2, name: 1;ID: 3, name: 2;ID: 4, name: 3;ID: 5, name: 4;ID: 6, name: 5;ID: 7, name: 6;ID: 8, name: 7;ID: 9, name: 8;ID: 10, name: 9;
回收连接
ID: 1, name: 0;ID: 2, name: 1;ID: 3, name: 2;ID: 4, name: 3;ID: 5, name: 4;ID: 6, name: 5;ID: 7, name: 6;ID: 8, name: 7;ID: 9, name: 8;ID: 10, name: 9;
回收连接
ID: 1, name: 0;ID: 2, name: 1;ID: 3, name: 2;ID: 4, name: 3;ID: 5, name: 4;ID: 6, name: 5;ID: 7, name: 6;ID: 8, name: 7;ID: 9, name: 8;ID: 10, name: 9;
回收连接
自写连接池查询耗时：6 毫秒
Disconnected from the target VM, address: '127.0.0.1:54211', transport: 'socket'

总结

从接口上看，一部分是符合我们预期的：连接池的性能是远远优于不使用连接池的

但自定义的连接池竟然比Druid还快，是我没有想到的，一度有些怀疑

但相关的地址确实是实现了的，从日志上来看，确实是只初始化了一次，后面没有再初始物理连接

目前的例子是单线程，没有考虑加锁、检查、异常处理等，可能是这些有影响，后面我们再研究研究

代码参考地址：https://github.com/lw1243925457/DataSourcePoolDemo

参考链接

Alibaba Druid 源码阅读（一）数据库连接池初步
Alibaba Druid 源码阅读（二）数据库连接池实现初步探索
Alibaba Druid 源码阅读（三）数据库连接池初始化探索
Alibaba Druid 源码阅读（四）数据库连接池中连接获取探索
Alibaba Druid 源码阅读（五）数据库连接池连接关闭探索