How do I read CLOBs data from database?

package org.kodejava.jdbc;

import java.nio.charset.StandardCharsets;
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, StandardCharsets.UTF_8)) {
                    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`)
) ENGINE = InnoDB;

Maven dependencies


Maven Central


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


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