如何使用bouncycastle读取X509主题目录属性扩展i java

Question

我尝试使用以下代码提取主题目录属性扩展中每个属性的String值，但它显示以下错误： getInstance中的未知对象org.bouncycastle.asn1.DEROctetString

encoded = cert.getExtensionValue(X509Extensions.SubjectDirectoryAttributes.toString()));
X509Extension sdaExt = new X509Extension(sdaCritical,new DEROctetString(encoded));
ASN1Object obj = X509Extension.convertValueToObject(sdaExt);
SubjectDirectoryAttributes sda = SubjectDirectoryAttributes.getInstance(obj);
for(Object attribute: sda.getAttributes()) {
     ASN1Set value = ((Attribute)attribute).getAttrValues();
     ASN1ObjectIdentifier attrType = ((Attribute)attribute).getAttrType();
     if(attrType.toString().equals("1.3.6.1.5.5.7.9.1")) {
         access.setDateOfBirth(value.toString());
     }
     else if(attrType.toString().equals("1.3.6.1.5.5.7.9.2")) {
              access.setSubjectDirectoryAttribute(0, value.toString());
          }
          else if(attrType.toString().equals("1.3.6.1.5.5.7.9.4")) {
                   access.setSubjectDirectoryAttribute(1, value.toString());
               }
               else if(attrType.toString().equals("1.3.6.1.5.5.7.9.3")) {
                        access.setGender(value.toString());
                    }

我该如何解决这个问题？