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:

/* OracleBlobGetBlob.java
 * Copyright (c) HerongYang.com. All Rights Reserved.
 */
import java.io.*;
import java.sql.*;
public class OracleBlobGetBlob {
  public static void main(String [] args) {
    Connection con = null;
    try {
      oracle.jdbc.pool.OracleDataSource ds
        = new oracle.jdbc.pool.OracleDataSource();
      ds.setDriverType("thin");
      ds.setServerName("localhost");
      ds.setPortNumber(1521);
      ds.setDatabaseName("XE");
      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) {
      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:

herong> java -cp .;ojdbc11.jar OracleBlobGetBlob

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: 3
   Subject = Test of setBinaryStream() methods
   Body Size = 2527
   Body in HEX = CAFEBABE000340ABA0370447045A020448046A020478...

Table of Contents

 About This Book

 JDBC (Java Database Connectivity) Introduction

 JDK (Java SE) Installation

 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

 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

 Copying BLOB Values to New Rows

 Archived Tutorials

 References

 Full Version in PDF/EPUB