Java - JDBC PostgreSQL Read Image Example

In the previous example, we have inserted an image into the database table. Now we are going to read the image back from the table.

PostgreSQL is a powerful, open-source object-relational database system. It is a multi-user database management system. It runs on multiple platforms including Linux, FreeBSD, Solaris, Microsoft Windows, and Mac OS X. PostgreSQL is developed by the PostgreSQL Global Development Group.

Check out all Java PostgreSQL examples at Java PostgreSQL Tutorial.

Technologies used

We use below technologies in this tutorial:

• JDK - 1.8 or later
• PostgreSQL- 42.2.9
• IDE - Eclipse Neon
• JDBC - 4.2

Download PostgreSQL JDBC Driver

To connect to the PostgreSQL database server from a Java program, you need to have a PostgreSQL JDBC driver. You can download the latest version of the driver on the postgresql.org website via the download page.

Add the PostgreSQL JDBC driver jar file to the project classpath.

For maven users:

<!-- https://mvnrepository.com/artifact/org.postgresql/postgresql -->
<dependency>
    <groupId>org.postgresql</groupId>
    <artifactId>postgresql</artifactId>
    <version>42.2.9</version>
</dependency>

For Gradle users:

// https://mvnrepository.com/artifact/org.postgresql/postgresql
compile group: 'org.postgresql', name: 'postgresql', version: '42.2.9'

PostgreSQL Database Setup

In the previous example, we have inserted an image into the database table. Now we are going to read the image back from the table.

Java - JDBC PostgreSQL Read Image Example

package net.javaguides.postgresql.tutorial;

import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.logging.Level;
import java.util.logging.Logger;

public class JavaPostgreSqlReadImage {

    public static void main(String[] args) {

        String url = "jdbc:postgresql://localhost:5432/mydb";
        String user = "postgres";
        String password = "root";

        String query = "SELECT data, LENGTH(data) FROM images WHERE id = 1";

        try (Connection con = DriverManager.getConnection(url, user, password); PreparedStatement pst = con.prepareStatement(query); ResultSet rs = pst.executeQuery()) {

            rs.next();

            File myFile = new File("java-logo1.jpg");

            try (FileOutputStream fos = new FileOutputStream(myFile)) {

                int len = rs.getInt(2);
                byte[] buf = rs.getBytes("data");
                fos.write(buf, 0, len);
            }

        } catch (IOException | SQLException ex) {

            Logger lgr = Logger.getLogger(JavaPostgreSqlReadImage.class.getName());
            lgr.log(Level.SEVERE, ex.getMessage(), ex);
        }
    }
}

Check out all Java PostgreSQL examples at Java PostgreSQL Tutorial.