基于java线程池读取单个SQL数据库表

任务：基于线程池来操作MySQL，测试单台机器读写MySQL单表的效率。

思路：创建一个大小合适的线程池，让每个线程分别连接到数据库并进行读取输出操作。

连接到数据库

import java.sql.DriverManager;
import java.sql.SQLException;

import com.mysql.jdbc.Statement;

public class TEXT {

}

class MySQLOpen {
private Connection con = null;
private static String driver = "com.mysql.jdbc.Driver";
private static String url = "jdbc:mysql://localhost:3306/phpmyadmin";
private static String username = "root";
private static String password = "root";
private static Statement NULL = null;

public void MysqlOpen() {
try {
 Class.forName(driver); //加载驱动类
 con = DriverManager.getConnection(url, username, password); //连接数据库
 if (!con.isClosed())
 System.out.println("***数据库成功连接***");
} catch (ClassNotFoundException e) {
 System.out.println("找不到驱动程序类，加载驱动失败");
 e.printStackTrace();
} catch (SQLException e) {
 System.out.println("数据库连接失败");
 e.printStackTrace();
}
}
}

利用statement类中的executeQuery方法操作MySQL

Statement state = (Statement) con.createStatement();
ResultSet sql = state.executeQuery("select * from user where id between 1 and 5");

利用sql.next()循环遍历取出想要的数据

while (sql.next()) {
String id = sql.getString(1);
String username = sql.getString(3);
String text = sql.getString(6);
   System.out.println(id+"\t"+username+"\t"+text);
}

以上就已经实现了主线程访问并操作数据库的相应内容。

创建线程池，设置好相应参数

ThreadPoolExecutor executor = new ThreadPoolExecutor(5, 15, 200, TimeUnit.MILLISECONDS,
 new ArrayBlockingQueue<Runnable>(5));

利用for循环去创建线程即可。

计算效率

long start = System.currentTimeMillis();
long end = System.currentTimeMillis();
System.out.println("平均每秒可输出: " + 100000 / (end - start) + " 条");

要注意主线程创建好其他线程后就继续往下执行了，所以要有一个判断其他线程是否结束的语句

while (true) {
if (executor.getActiveCount() == 0)
 break;
}

可以利用Thread.activeCount()看一还有多少 活跃的线程。

System.out.println("activeCountMain1 : " + Thread.activeCount());

主要的思路就再上面，现在贴出整理好的代码：

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.concurrent.ArrayBlockingQueue;
import java.util.concurrent.ThreadPoolExecutor;
import java.util.concurrent.TimeUnit;

import com.mysql.jdbc.Statement;

public class Main {

public static void main(String[] args) {
ThreadPoolExecutor executor = new ThreadPoolExecutor(5, 15, 200, TimeUnit.MILLISECONDS,
 new ArrayBlockingQueue<Runnable>(5));
long start = System.currentTimeMillis();
System.out.println("activeCountMain1 : " + Thread.activeCount());
for (int i = 1; i <= 20; i++) {
 MySQL mysql = new MySQL(i);
 executor.execute(mysql);
 System.out.println("线程池中线程数目：" + executor.getPoolSize() + "，队列中等待执行的任务数目：" + executor.getQueue().size()
  + "，已执行玩别的任务数目：" + executor.getCompletedTaskCount());
}
executor.shutdown();
while (true) {
 if (executor.getActiveCount() == 0)
 break;
}
System.out.println("activeCountMain2 : " + Thread.activeCount());
long end = System.currentTimeMillis();
System.out.println("平均每秒可输出: " + 100000 / (end - start) + " 条");
}
}

class MySQL implements Runnable {
private Connection con = null;
private static String driver = "com.mysql.jdbc.Driver";
private static String url = "jdbc:mysql://localhost:3306/phpmyadmin";
private static String username = "root";
private static String password = "root";
private static Statement NULL = null;
private final int taskNum;

public MySQL(int taskNum) {
this.taskNum = taskNum;
}

public Statement MysqlOpen() {
try {
 Class.forName(driver); //加载驱动类
 con = DriverManager.getConnection(url, username, password); //连接数据库
 if (!con.isClosed())
 System.out.println("***数据库成功连接***");
 Statement state = (Statement) con.createStatement();
 return state;
} catch (ClassNotFoundException e) {
 System.out.println("找不到驱动程序类，加载驱动失败");
 e.printStackTrace();
} catch (SQLException e) {
 System.out.println("数据库连接失败");
 e.printStackTrace();
}
return NULL;
}
@Override
public void run() {
readMySQL();
}

public void readMySQL() {
ResultSet sql = null;
Statement state = MysqlOpen();
try {
 sql = state.executeQuery("select * from sina_user_weibos_1386622641 where id between "
  + ((taskNum - 1) * 5000) + " and " + (taskNum * 5000));
 System.out.println("---------task " + taskNum + "正在执行---------");
 while (sql.next()) {
 String id = sql.getString(1);
 String wid = sql.getString(2);
 String username = sql.getString(3);
 String repostscount = sql.getString(4);
 String commentscount = sql.getString(5);
 String text = sql.getString(6);
 String createat = sql.getString(7);
 String source = sql.getString(15);
 String lasttime = sql.getString(17);
 System.out.println(id + "\t" + wid + "\t" + username + "\t" + repostscount + "\t" + commentscount + "\t"
  + text + "\t" + createat + "\t" + source + "\t" + lasttime);
 }
} catch (SQLException e) {
 e.printStackTrace();
} finally {
 try {
 sql.close();
 state.close();
 con.close();
 } catch (Exception e) {
 e.printStackTrace();
 }
}
System.out.println("---------task " + taskNum + "执行完毕---------");
}
}

来源：https://blog.csdn.net/qq_27075943/article/details/51208503