Sample for persisting CLOB with pure JDBC

DocumentDAO.java

package example.clob001;

import java.math.BigDecimal;
import java.nio.file.FileSystems;
import java.nio.file.Files;
import java.nio.file.Path;
import java.sql.Clob;
import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.Statement;

public class DocumentDAO {
	private Connection conn;
	
	public DocumentDAO(Connection conn) {
		this.conn = conn;
	}
	
	public void persistDocument(String name, String filePath) throws Exception {
		System.out.println("Name: "+ name);
		System.out.println("File path: " + filePath);
		
		BigDecimal documentId = generateDocumentId();
		insertRecord(documentId, name);
		String documentContent = getDocumentContentFromFile(filePath);
		persistContent(documentId, documentContent);
	}
	
	private BigDecimal generateDocumentId() throws Exception {
		BigDecimal documentId = null;
		
		String seqSql = "SELECT DOCUMENT_ID_SEQ.NEXTVAL FROM DUAL";
		try (Statement statement = conn.createStatement()) {
			try (ResultSet resultSet = statement.executeQuery(seqSql)) {
				resultSet.next();
				documentId = resultSet.getBigDecimal(1);
				System.out.println("Document id: " + documentId);
			}
		}
		
		return documentId;
	}
	
	private void insertRecord(BigDecimal documentId, String name) throws Exception {
		String insertSql = "INSERT INTO DOCUMENT (ID, NAME, CONTENT) VALUES (?, ?, EMPTY_CLOB())";
		try (PreparedStatement q = conn.prepareStatement(insertSql)) {
			q.setBigDecimal(1, documentId);
			q.setString(2, name);
			q.executeUpdate();
		}
	}
	
	private String getDocumentContentFromFile(String filePath) throws Exception {
		Path path = FileSystems.getDefault().getPath(filePath);
		byte[] bytes = Files.readAllBytes(path);
		String documentContent = new String(bytes, "utf-8");
		System.out.println("*********************");
		System.out.println("Document content:");
		System.out.println(documentContent);
		System.out.println("*********************");
		
		return documentContent;
	}
	
	private void persistContent(BigDecimal documentId, String documentContent) throws Exception {
		String selectSql = "SELECT CONTENT FROM DOCUMENT WHERE ID = ?";
		try (PreparedStatement q = conn.prepareStatement(selectSql)) {
			q.setBigDecimal(1, documentId);
			try (ResultSet resultSet = q.executeQuery()) {
				resultSet.next();
				Clob clob = resultSet.getClob(1);
				clob.setString(1, documentContent);
				
				String updateSql = "UPDATE DOCUMENT SET CONTENT = ? WHERE ID = ?";
				try (PreparedStatement q2 = conn.prepareStatement(updateSql)) {
					q2.setClob(1, clob);
					q2.setBigDecimal(2, documentId);
					q2.executeUpdate();
				}
			}
		}
	}
}