Writing data from database to .csv file

You can write data into a .csv file using the OpenCSV library and, you can communicate with MySQL database through a Java program using the mysql-java-connector.

Maven dependency

The following are the dependencies you need to include in your pom.xml file to write data to a .csv file from a database table.

<dependency>
   <groupId>com.opencsv</groupId>
   <artifactId>opencsv</artifactId>
   <version>4.4</version>
</dependency>
<dependency>
   <groupId>org.apache.commons</groupId>
   <artifactId>commons-lang3</artifactId>
   <version>3.9</version>
</dependency>
<dependency>
   <groupId>mysql</groupId>
   <artifactId>mysql-connector-java</artifactId>
   <version>5.1.6</version>
</dependency>

Writing data to a CSV file

The CSVWriter class of the com.opencsv package represents a simple CSV writer. While instantiating this class you need to pass a Writer object representing the file, to which you want to write the data, as a parameter to its constructor. It provides methods named writeAll() and writeNext() to write data to a .csv file

Using the writeNext() method

The writeNext() method of the CSVWriter class writes the next line to the .csv file

Example

Assume we have created a table with name empDetails and populated it using the following queries −

CREATE TABLE empDetails (ID INT, Name VARCHAR(255), Salary INT, start_date VARCHAR(255), Dept VARCHAR(255));
Insert INTO empDetails values (1, 'Krishna', 2548, '2012-01-01', 'IT');
Insert INTO empDetails values (2, 'Vishnu', 4522, '2013-02-26', 'Operations');
Insert INTO empDetails values (3, 'Raja', 3021, '2016-10-10', 'HR');
Insert INTO empDetails values (4, 'Raghav', 6988, '2012-01-01', 'IT');

The following Java program creates a csv file from the above-created table.

import java.io.FileWriter;
import java.io.IOException;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.SQLException;
import java.sql.Statement;
import com.opencsv.CSVWriter;
public class DbToCSV {
   public static void main(String args[]) throws SQLException, IOException {
      //Getting the connection
      String url = "jdbc:mysql://localhost/mydb";
      Connection con = DriverManager.getConnection(url, "root", "password");
      System.out.println("Connection established......");
      //Creating the Statement
      Statement stmt = con.createStatement();
      //Query to retrieve records
      String query = "Select * from empDetails";
      //Executing the query
      stmt.executeQuery("use mydb");
      ResultSet rs = stmt.executeQuery(query);
      //Instantiating the CSVWriter class
      CSVWriter writer = new CSVWriter(new FileWriter("D://output.csv"));
      ResultSetMetaData Mdata = rs.getMetaData();
      Mdata.getColumnName(1);
      //Writing data to a csv file
      String line1[] = {Mdata.getColumnName(1), Mdata.getColumnName(2), Mdata.getColumnName(3), Mdata.getColumnName(4), Mdata.getColumnName(5)};
      writer.writeNext(line1);
      String data[] = new String[5];
      while(rs.next()) {
         data[0] = new Integer(rs.getInt("ID")).toString();
         data[1] = rs.getString("Name");
         data[2] = new Integer(rs.getInt("Salary")).toString();
         data[3] = rs.getString("start_date");
         data[4] = rs.getString("Dept");
         writer.writeNext(data);
      }
      //Flushing data from writer to file
      writer.flush();
      System.out.println("Data entered");
   }
}

Output

Connection established......
Data entered

If you verify the generated .csv file you can observe its contents as follows −

"ID","Name","Salary","start_date","Dept"
"1","Krishna","2548","2012-01-01","IT"
"2","Vishnu","4522","2013-02-26","Operations"
"3","Raja","3021","2016-10-10","HR"
"4","Raghav","6988","2012-01-01","IT"