http://www.bouncycastle.org/java.html: The Bouncy Castle Java APIs for CMS, PKCS, EAC, TSP, CMP, CRMF, OCSP, and certificate generation. This jar contains APIs for JDK 1.5 to JDK 1.8. The APIs can be used in conjunction with a JCE/JCA provider such as the one provided with the Bouncy Castle Cryptography APIs.
  • The Legion of the Bouncy Castle Inc. 
package org.bouncycastle.cms;

import java.io.IOException;
import java.io.OutputStream;
import java.util.Iterator;

import org.bouncycastle.asn1.ASN1Encodable;
import org.bouncycastle.asn1.ASN1Encoding;
import org.bouncycastle.asn1.ASN1ObjectIdentifier;
import org.bouncycastle.asn1.ASN1Sequence;

public class PKCS7ProcessableObject
    implements CMSTypedData
{
    private final ASN1ObjectIdentifier type;
    private final ASN1Encodable structure;

    public PKCS7ProcessableObject(
        ASN1ObjectIdentifier type,
        ASN1Encodable structure)
    {
        this.type = type;
        this.structure = structure;
    }

    public ASN1ObjectIdentifier getContentType()
    {
        return type;
    }

    public void write(OutputStream cOut)
        throws IOException, CMSException
    {
        if (structure instanceof ASN1Sequence)
        {
            ASN1Sequence s = ASN1Sequence.getInstance(structure);

            for (Iterator it = s.iterator(); it.hasNext();)
            {
                ASN1Encodable enc = (ASN1Encodable)it.next();

                cOut.write(enc.toASN1Primitive().getEncoded(ASN1Encoding.DER));
            }
        }
        else
        {
            byte[] encoded = structure.toASN1Primitive().getEncoded(ASN1Encoding.DER);
            int index = 1;

            while ((encoded[index] & 0xff) > 127)
            {
                index++;
            }

            index++;

            cOut.write(encoded, index, encoded.length - index);
        }
    }

    public Object getContent()
    {
        return structure;
    }
}