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How to manipulate a BLOB in Java?
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Solved javablob
L

5

11

I have a DB procedure which returns a BLOB. Can anyone tell me how to manipulate the BLOB? Is there any specific API for this?

Leticialetisha answered 17/10, 2011 at 7:9 Comment(1)
Such as the API for java.sql.Blob? – Apprentice
H
16

Is there any specific API for this ?

Sure, the JDBC API.

You get hold of the Blob instance just as you get hold of any value from a result set. You should then use the get...- and set... methods on this Blob.

Here you basically have two options:

An alternative approach is to skip messing with Blob in the first place, and instead use the second approach (with streams) directly through the ResultSet-interface.

Harebrained answered 17/10, 2011 at 7:12 Comment(3)
My experience is that ResultSet.getBinaryStream() is more robust than working with instances of Blob – Parietal
@Harebrained : Thanks for the responses. But can anyone tell me how 'ResultSet.getBinaryStream()' is robust compared to 'Blob.getBinaryStream' ? – Leticialetisha
If your driver supports ResultSet.getBlob and Blob.getBinaryStream, and you're fairly confident that you won't switch to another database, just go with the one you find most readable. – Harebrained
C
5

It depends on which kind of blob contains (image, video) and it's extension. I wrote a simple program to retrieve an image from DB and show it in JSP page. Hope it helps.

JSP Page

<html>
<head>
    <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
    <title>JSP Page</title>
</head>
<body>                            
    <image src="blobAction"/> 
</body>

Servlet Page

byte[] imgData = blobDao.getInstance().getPhoto();
        response.setContentType("image/gif");
        OutputStream o = response.getOutputStream();
        o.write(imgData);
        o.flush();
        o.close();

Calling Procedure 

public byte[] getPhoto() {

    byte[] imgData = null;
    Blob img = null;
    ResultSet rs = null;
    Statement stmt = null;

    try {

        conn = getConnection();
        String sqlQ = "SELECT CONTENT_FILE FROM CONTENT where id = 'something';
        stmt = conn.createStatement();
        rs = stmt.executeQuery(sqlQ);

        while (rs.next()) {
            img = rs.getBlob("CONTENT_FILE");
            imgData = img.getBytes(1, (int) img.length());
        }
        rs.close();
        stmt.close();
        conn.close();
    } catch (Exception ex) {
        ex.printStackTrace();
    } finally {           
        return imgData;
    }
}
Conventicle answered 22/12, 2011 at 13:39 Comment(0)
P
3

With Simple Java JDBC Api, you can get a java.sql.Blob back from a ResultSet.

  1. ResultSet.getBlob(index) or
  2. ResultSet.getBlob(String columnName).

Both returns a Blob.

Once you get a Blob, you can get the byte[] back from the Blob.getBytes() method or set using setBytes() method.

Update: Seeing that some Database driver vendors don't support Blob, you can use ResultSet.getBinaryStream().

Philanthropy answered 17/10, 2011 at 7:14 Comment(3)
Why pointless? The existence of a BLOB datatype in the database has nothing to do with the support by the driver. Not all drivers support ResultSet.getBlob() some only support ResultSet.getInputStream() – Parietal
@All : Thanks guys for the responses. If getBlob() is not supported by all then which method is good to use ? Blob.getBinaryStream() ? – Leticialetisha
I usually do ResultSet.getBytes() and work with byte[] instead. – Philanthropy
E
0

You can use javax.sql.rowset.serial.SerialBlob.

I'm using it in my SpringBoot & Angular4 application like this:

  • get Base64String from Angular4 app
  • decode Base64String to byte[]
  • create SerialBlob like this: SerialBlob serialBlob = new SerialBlob(byte[])
  • store it in the database with JpaRepository
Electrokinetics answered 9/1, 2018 at 15:48 Comment(0)
M
0

Example

public void Insert(Object obj){
        try {
            ByteArrayOutputStream byteArray = new ByteArrayOutputStream();
            ObjectOutputStream oos=new ObjectOutputStream(byteArray);
            oos.writeObject(obj);
            PreparedStatement ps= conn1.prepareStatement("insert into vehiculos values(?)");    
            ps.setBytes(1, byteArray.toByteArray());  
            ps.execute();
            ps.close();
        } catch (SQLException ex) {
            System.out.println("ERROR:al hacer un Insert");   
            ex.printStackTrace();
        } catch (IOException ex) {
            Logger.getLogger(Conexion.class.getName()).log(Level.SEVERE, null, ex);
        }
    }
    public void ShowData(){
        try {
            Statement stmt = conn1.createStatement();
            String query = "SELECT * FROM vehiculos";
            ResultSet rs = stmt.executeQuery(query);
            Object obj;
            while(rs.next()){
                //Coche c = (Coche)rs.getBlob("coches");
                Blob blob = rs.getBlob("coches");
                ObjectInputStream ois = new ObjectInputStream(blob.getBinaryStream());
                obj = ois.readObject();
                System.out.println(obj.toString());
                System.out.println("");
                /*Blob blob = rs.getBlob("coches");
                byte[] data = blob.getBytes(1, (int)blob.length());*/
                
            }
            rs.close();
            stmt.close();
        
      } catch (SQLException ex) {
            System.out.println("ERROR:al consultar");
            ex.printStackTrace();
      } catch (IOException ex) {
            Logger.getLogger(Conexion.class.getName()).log(Level.SEVERE, null, ex);
        } catch (ClassNotFoundException ex) {
            Logger.getLogger(Conexion.class.getName()).log(Level.SEVERE, null, ex);
        }
    }
    public void cerrar_Conexion (){
       
        try {  
        conn1.close();
      } catch (SQLException ex) {
            System.out.println("ERROR:al cerrar la conexión");
            ex.printStackTrace();
      }
    }
Margerymarget answered 7/2, 2022 at 0:53 Comment(0)

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