How to create BLOB object in java?

问题:

1.How to create BLOB object in java?
2.How to set the BLOB value from db?
3.How to set the BLOB value in DB?

I have create the BLOB object like

byte [] fileId=b.toByteArray();
    Blob blob=new SerialBlob(fileId);

But it gives me error..So please any one help me. Thanks in advance.

回答1:

1) to create BLOB use Connection.createBlob

2) to write BLOB to DB use PreparedStatement.setBlob

3) to read BLOB from DB use ResultSet.getBlob

Assuming you have table t1 with BLOB column b1:

    Connection conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/test", "root", "root");
    Blob b1 = conn.createBlob();
    b1.setBytes(1, new byte[10]); // first position is 1. Otherwise you get: Value of offset/position/start should be in the range [1, len] where len is length of Large Object[LOB]

    PreparedStatement ps = conn.prepareStatement("update t1 set c1 = ?");
    ps.setBlob(1, b1);
    ps.executeUpdate();

    Statement st = conn.createStatement();
    ResultSet rs = st.executeQuery("select c1 from t1");
    Blob b2 = rs.getBlob(1);