java串行和并行两种方式实现读取mysql数据到文本文档

首先，使用串行方式实现读取MySQL数据到文本文档的代码如下：

import java.io.FileWriter;
import java.io.IOException;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

public class SerialReadData {

    public static void main(String[] args) {

        Connection conn = null;
        Statement stmt = null;
        ResultSet rs = null;
        FileWriter fw = null;

        try {
            // 1. 获取数据库连接
            Class.forName("com.mysql.cj.jdbc.Driver");
            conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/test?useSSL=false&serverTimezone=UTC", "root", "123456");

            // 2. 创建Statement对象
            stmt = conn.createStatement();

            // 3. 查询数据
            rs = stmt.executeQuery("SELECT * FROM student");

            // 4. 将数据写入文本文件
            fw = new FileWriter("student.txt");
            while (rs.next()) {
                String id = rs.getString("id");
                String name = rs.getString("name");
                int age = rs.getInt("age");
                fw.write(id + ", " + name + ", " + age + "\n");
            }
            fw.flush();

            System.out.println("数据导出成功！");

        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (SQLException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                if (rs != null) rs.close();
                if (stmt != null) stmt.close();
                if (conn != null) conn.close();
                if (fw != null) fw.close();
            } catch (SQLException | IOException e) {
                e.printStackTrace();
            }
        }
    }
}

接下来，使用并行方式实现读取MySQL数据到文本文档的代码如下：

import java.io.FileWriter;
import java.io.IOException;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

public class ParallelReadData {

    static class Task implements Runnable {
        private ResultSet rs;
        private FileWriter fw;

        public Task(ResultSet rs, FileWriter fw) {
            this.rs = rs;
            this.fw = fw;
        }

        @Override
        public void run() {
            try {
                while (rs.next()) {
                    String id = rs.getString("id");
                    String name = rs.getString("name");
                    int age = rs.getInt("age");
                    synchronized (fw) {
                        fw.write(id + ", " + name + ", " + age + "\n");
                    }
                }
            } catch (SQLException | IOException e) {
                e.printStackTrace();
            }
        }
    }

    public static void main(String[] args) {

        Connection conn = null;
        Statement stmt = null;
        ResultSet rs = null;
        FileWriter fw = null;

        try {
            // 1. 获取数据库连接
            Class.forName("com.mysql.cj.jdbc.Driver");
            conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/test?useSSL=false&serverTimezone=UTC", "root", "123456");

            // 2. 创建Statement对象
            stmt = conn.createStatement();

            // 3. 查询数据
            rs = stmt.executeQuery("SELECT * FROM student");

            // 4. 将数据写入文本文件
            fw = new FileWriter("student.txt");
            ExecutorService executorService = Executors.newFixedThreadPool(10);
            int count = Runtime.getRuntime().availableProcessors();
            for (int i = 0; i < count; i++) {
                executorService.execute(new Task(rs, fw));
            }
            executorService.shutdown();
            while(!executorService.isTerminated()) {
                Thread.sleep(1000);
            }

            System.out.println("数据导出成功！");

        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        } catch (SQLException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } catch (InterruptedException e) {
            e.printStackTrace();
        } finally {
            try {
                if (rs != null) rs.close();
                if (stmt != null) stmt.close();
                if (conn != null) conn.close();
                if (fw != null) fw.close();
            } catch (SQLException | IOException e) {
                e.printStackTrace();
            }
        }
    }
}

在并行方式中，我们使用了线程池来创建多个线程并发读取数据库，同时使用了同步锁来保证写入文件的安全性。