Retrieving BLOB Values with getBlob() Method

This section describes how to retrieve BLOB values with the ResultSet.getBlob() method.

If you like to work with java.sql.Blob objects, you can retrieve BLOB values with the getBlob() method on ResultSet objects. The Blob object offers some interesting methods:

Here is my test program on getBlob() method:

/* MySqlBlobGetBlob.java
 - Copyright (c) 2015, HerongYang.com, All Rights Reserved.
 */
import java.io.*;
import java.sql.*;
public class MySqlBlobGetBlob {
  public static void main(String [] args) {
    Connection con = null;
    try {
      com.mysql.jdbc.jdbc2.optional.MysqlDataSource ds 
        = new com.mysql.jdbc.jdbc2.optional.MysqlDataSource();
      ds.setServerName("localhost");
      ds.setPortNumber(3306);
      ds.setDatabaseName("HerongDB");
      ds.setUser("Herong");
      ds.setPassword("TopSecret");
      con = ds.getConnection();

// Retrieving BLOB value with getBlob()
      Statement sta = con.createStatement(); 
      ResultSet res = sta.executeQuery("SELECT * FROM Image"); 
      int i = 0;
      while (res.next() && i<3) {
        i++;
        System.out.println("Record ID: "+res.getInt("ID"));
        System.out.println("   Subject = "+res.getString("Subject"));
        Blob bodyOut = res.getBlob("Body");
        int length = (int) bodyOut.length();
        System.out.println("   Body Size = "+length);
        byte[] body = bodyOut.getBytes(1, length);
        String bodyHex = bytesToHex(body, 32);
        System.out.println("   Body in HEX = "+bodyHex+"...");
//      bodyOut.free(); // new in JDBC 4.0
      }
      res.close();

      sta.close();
      con.close();
    } catch (Exception e) {
      System.err.println("Exception: "+e.getMessage());
      e.printStackTrace();
    }
  }
  public static String bytesToHex(byte[] bytes, int max) {
    StringBuffer buffer = new StringBuffer();
    for (int i=0; i<bytes.length && i<max; i++) {
      buffer.append(Integer.toHexString(bytes[i] & 0xFF)); 
    }
    return buffer.toString().toUpperCase();
  }
}

The output confirms that the getBlob() method and Blob objects are not hard to use:

C:\herong>\Progra~1\java\jdk1.8.0_45\bin\java 
   -cp .;\local\lib\mysql-connector-java-5.1.36-bin.jar 
   MySqlBlobGetBlob

Record ID: 1
   Subject = Test on INSERT statement
   Body Size = 15
   Body in HEX = C9CBBBCCCEB9C8CABCCCCEB9C9CBBB...
Record ID: 2
   Subject = Test of the setBytes() method
   Body Size = 15
   Body in HEX = C9CBBBCCCEB9C8CABCCCCEB9C9CBBB...
Record ID: 4
   Subject = Test of setBinaryStream() methods
   Body Size = 2648
   Body in HEX = CAFEBABE000340B5A03B0487049A02048804AA0204BA...

Last update: 2015.

Table of Contents

 About This Book

 JDBC (Java Database Connectivity) Introduction

 JDK (Java SE) Installation

 Installing and Running Java DB - Derby

 Derby (Java DB) JDBC Driver

 Derby (Java DB) JDBC DataSource Objects

 Java DB (Derby) - DML Statements

 Java DB (Derby) - ResultSet Objects of Queries

 Java DB (Derby) - PreparedStatement

 MySQL Installation on Windows

 MySQL JDBC Driver (MySQL Connector/J)

 MySQL - PreparedStatement

 MySQL - Reference Implementation of JdbcRowSet

 MySQL - JBDC CallableStatement

 MySQL CLOB (Character Large Object) - TEXT

MySQL BLOB (Binary Large Object) - BLOB

 Overview of BLOB (Binary Large Object)

 Create Tables with CLOB Columns

 Inserting BLOB Values with SQL INSERT Statements

 Inserting BLOB Values with setBytes() Method

 Inserting BLOB Values with setBinaryStream() Method

 Closing InputStream Too Early on setBinaryStream()

 Retrieving BLOB Values with getBytes() Method

 Retrieving BLOB Values with getBinaryStream() Method

Retrieving BLOB Values with getBlob() Method

 Inserting BLOB Values with setBlob() Method

 Oracle Express Edition Installation on Windows

 Oracle JDBC Drivers

 Oracle - Reference Implementation of JdbcRowSet

 Oracle - PreparedStatement

 Oracle - JBDC CallableStatement

 Oracle CLOB (Character Large Object) - TEXT

 Oracle BLOB (Binary Large Object) - BLOB

 Microsoft SQL Server 2005 Express Edition

 Microsoft JDBC Driver for SQL Server - sqljdbc42.jar

 Microsoft JDBC Driver - Query Statements and Result Sets

 Microsoft JDBC Driver - DatabaseMetaData Object

 Microsoft JDBC Driver - DDL Statements

 Microsoft JDBC Driver - DML Statements

 SQL Server - PreparedStatement

 SQL Server CLOB (Character Large Object) - TEXT

 SQL Server BLOB (Binary Large Object) - BLOB

 JDBC-ODBC Bridge Driver - sun.jdbc.odbc.JdbcOdbcDriver

 JDBC-ODBC Bridge Driver - Flat Text Files

 JDBC-ODBC Bridge Driver - MS Access

 JDBC-ODBC Bridge Driver - MS SQL Server

 Summary of JDBC Drivers and Database Servers

 Additional Tutorial Notes to Be Added

 Outdated Tutorials

 References

 PDF Printing Version