线程“主”中的异常java.security.NoSuchAlgorithmException：找不到支持MyCipher的任何提供程序

Question

我想添加一个自我实现的提供程序（java.security.provider）并对其进行测试。我遵循了oracle docs的指示（但？），但我陷入了步骤3：

Exception in thread "main" java.security.NoSuchAlgorithmException: Cannot find any provider supporting MyCipher
    at javax.crypto.Cipher.getInstance(Cipher.java:539)
    at Test.main(Test.java:16)

这是我的代码：

-MyProvider：

public final class MyProvider extends Provider{
/**
 * 
 */
private static final long serialVersionUID = 1L;

public MyProvider() {
    super("MyProvider", 0.1, "test");
    //put("Cipher.MyCipher","MyCipher");
    putService(new ProviderService(this, "Cipher", "MyCipher", "p.MyCipher"));
}

private static final class ProviderService extends Provider.Service {
    ProviderService(Provider p, String type, String algo, String cn) {
        super(p, type, algo, cn, null, null);
    }

    @Override
    public Object newInstance(Object ctrParamObj) throws NoSuchAlgorithmException {
        String type = getType();
        String algo = getAlgorithm();
        try {
            if (type.equals("Cipher")) {
                if (algo.equals("MyCipher")) {
                    return new MyCipher();
                }
            }
        } catch (Exception ex) {
            throw new NoSuchAlgorithmException(
                "Error constructing " + type + " for "
                + algo + " using SunMSCAPI", ex);
        }
        throw new ProviderException("No impl for " + algo + " " + type);
        }
    }

}

-MyCipher：

package p;
public class MyCipher extends CipherSpi{
     .....//just default functions need to be overrided.
}

-测试：

public class Test {
public static void main (String[] args) throws NoSuchAlgorithmException, NoSuchPaddingException {
    Provider mp = new MyProvider();
    Security.addProvider(mp);
    System.out.println(Security.getProvider("MyProvider").getInfo());
    System.out.println(Security.getProvider("MyProvider").getServices().toString());

    Cipher c = Cipher.getInstance("MyCipher"); //exception here
    }
}

我真的不明白为什么会出现这种异常。我有误会吗？预先非常感谢。