基于java線程池讀取單個SQL數(shù)據(jù)庫表

更新時間：2019年08月29日 16:18:42 作者：Cedric是陳大澤

這篇文章主要為大家詳細(xì)介紹了基于java線程池讀取單個SQL數(shù)據(jù)庫表，具有一定的參考價值，感興趣的小伙伴們可以參考一下

任務(wù)：基于線程池來操作MySQL，測試單臺機(jī)器讀寫MySQL單表的效率。

思路：創(chuàng)建一個大小合適的線程池，讓每個線程分別連接到數(shù)據(jù)庫并進(jìn)行讀取輸出操作。

連接到數(shù)據(jù)庫

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); //加載驅(qū)動類
  con = DriverManager.getConnection(url, username, password); //連接數(shù)據(jù)庫
  if (!con.isClosed()) 
  System.out.println("***數(shù)據(jù)庫成功連接***");
 } catch (ClassNotFoundException e) {
  System.out.println("找不到驅(qū)動程序類，加載驅(qū)動失敗");
  e.printStackTrace();
 } catch (SQLException e) {
  System.out.println("數(shù)據(jù)庫連接失敗");
  e.printStackTrace();
 }
 }
}

利用statement類中的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()循環(huán)遍歷取出想要的數(shù)據(jù)

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);
}

以上就已經(jīng)實現(xiàn)了主線程訪問并操作數(shù)據(jù)庫的相應(yīng)內(nèi)容。

創(chuàng)建線程池，設(shè)置好相應(yīng)參數(shù)

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

利用for循環(huán)去創(chuàng)建線程即可。

計算效率

long start = System.currentTimeMillis();
long end = System.currentTimeMillis();
System.out.println("平均每秒可輸出: " + 100000 / (end - start) + " 條");

要注意主線程創(chuàng)建好其他線程后就繼續(xù)往下執(zhí)行了，所以要有一個判斷其他線程是否結(jié)束的語句

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

可以利用Thread.activeCount()看一還有多少活躍的線程。

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

主要的思路就再上面，現(xiàn)在貼出整理好的代碼：

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("線程池中線程數(shù)目：" + executor.getPoolSize() + "，隊列中等待執(zhí)行的任務(wù)數(shù)目：" + executor.getQueue().size()
   + "，已執(zhí)行玩別的任務(wù)數(shù)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("平均每秒可輸出: " + 100000 / (end - start) + " 條");
 }
}
 
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); //加載驅(qū)動類
  con = DriverManager.getConnection(url, username, password); //連接數(shù)據(jù)庫
  if (!con.isClosed())
  System.out.println("***數(shù)據(jù)庫成功連接***");
  Statement state = (Statement) con.createStatement();
  return state;
 } catch (ClassNotFoundException e) {
  System.out.println("找不到驅(qū)動程序類，加載驅(qū)動失敗");
  e.printStackTrace();
 } catch (SQLException e) {
  System.out.println("數(shù)據(jù)庫連接失敗");
  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 + "正在執(zhí)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 + "執(zhí)行完畢---------");
 }
}

以上就是本文的全部內(nèi)容，希望對大家的學(xué)習(xí)有所幫助，也希望大家多多支持腳本之家。

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