java代码：首先定义一个读取Oracle数据库的Blob字段并把字节写入一个输出流的方法。
 1 public static void writeImg(OutputStream os) {
 2         Connection con;
 3         try {
 4             con = ConnectionFactory.getConnection();
 5             Statement stmt = con.createStatement();
 6             ResultSet rs = stmt.executeQuery("select pic from blob_table where b_id=1");
 7             byte[] b = new byte[1024];
 8             if (rs.next()) {
 9                 Blob blob = rs.getBlob(1);
10                 InputStream is = blob.getBinaryStream();
11                 int i = 0;
12                 while ((i = is.read(b)) != -1) {
13                     os.write(b, 0, i);
14                 }
15                 os.close();
16                 is.close();
17             }
18             rs.close();
19             stmt.close();
20             con.close();
21         } catch (Exception e) {
22             e.printStackTrace();
23         }
24     }

然后做一个servlet，在doGet方法里调用writeImg方法
1 public void doGet(HttpServletRequest request, HttpServletResponse response)  
2             throws ServletException, IOException {  
3           
4         DBOperator.writeImg(response.getOutputStream());  
5           
6     }