How do I read CLOBs data from database?

package org.kodejava.example.jdbc;

import java.sql.*;

public class ClobReadDemo {
    private static final String URL = "jdbc:mysql://localhost/kodejava";
    private static final String USERNAME = "root";
    private static final String PASSWORD = "";

    public static void main(String[] args) {
        try (Connection conn =
                 DriverManager.getConnection(URL, USERNAME, PASSWORD)) {

            String sql = "SELECT book_isbn, data FROM book_excerpts";
            PreparedStatement stmt = conn.prepareStatement(sql);

            ResultSet resultSet = stmt.executeQuery();
            while ( {
                String bookIsbn = resultSet.getString("book_isbn");
                // Get the character stream of our CLOB file
                Reader reader = resultSet.getCharacterStream("data");

                File file = new File(bookIsbn + ".txt");
                try (FileWriter writer = new FileWriter(file)) {
                    char[] buffer = new char[1];
                    while ( > 0) {
        } catch (Exception e) {

The structure of book_excerpts table.

CREATE TABLE `book_excerpts` (
  `id` bigint(20) unsigned NOT NULL AUTO_INCREMENT,
  `book_isbn` varchar(50) NOT NULL,
  `description` varchar(255)  NOT NULL,
  `data` longtext,
  PRIMARY KEY (`id`),
  KEY `book_isbn` (`book_isbn`),
  CONSTRAINT `book_excerpts_ibfk_1` FOREIGN KEY (`book_isbn`) REFERENCES `books` (`isbn`)

Maven dependencies

<!-- -->

Maven Central

Wayan Saryada

Founder at Kode Java Org
I am a programmer, a runner, a recreational diver, currently live in the island of Bali, Indonesia. Mostly programming in Java, Spring Framework, Hibernate / JPA. You can support my works by donating here. Thank you ?


  1. Worked like magic.. Thank you for this great code snippet. Keep posting such nice stuff and keep empowering the community.


Leave a Reply

This site uses Akismet to reduce spam. Learn how your comment data is processed.