Application.java

package com.javaxp;

import java.io.BufferedWriter;
import java.io.File;
import java.io.FileWriter;
import java.io.IOException;
import java.util.List;
import java.util.Map;
import java.util.stream.Collectors;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.CommandLineRunner;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.jdbc.core.JdbcTemplate;

@SpringBootApplication
public class Application implements CommandLineRunner {

	@Autowired
	private JdbcTemplate jdbcTemplate;

	public static void main(String[] args) {
		SpringApplication.run(Application.class, args);
	}

	public void run(String... args) throws Exception {
		// Export database table
		export("TABLE_1");
		export("TABLE_2");
	}

	public void export(String tableName) {
		writeCSVFile(tableName + ".csv", getData(tableName));
	}

	public void writeCSVFile(String fileName, List<Map<String, Object>> data) {
		try (BufferedWriter bw = new BufferedWriter(new FileWriter(new File(fileName)))) {
			data.forEach(rowData -> {
				try {
					bw.write(String.join(",", rowData.values().stream().map(Object::toString).collect(Collectors.toList())));
					bw.newLine();
				} catch (IOException e) {
					e.printStackTrace();
				}
			});
			bw.flush();
		} catch (IOException e) {
			e.printStackTrace();
		}
	}

	public List<Map<String, Object>> getData(String tableName) {
		String sqlQuery = "SELECT * FROM " + tableName;
		return jdbcTemplate.queryForList(sqlQuery);
	}
}