Package org.eclipse.aether.spi.connector.checksum

Interface ChecksumPolicy

  • All Known Implementing Classes:
    AbstractChecksumPolicy, FailChecksumPolicy, WarnChecksumPolicy
    public interface ChecksumPolicy
    A checksum policy gets employed by repository connectors to validate the integrity of a downloaded file. For each downloaded file, a checksum policy instance is obtained and presented with the available checksums to conclude whether the download is valid or not. The following pseudo-code illustrates the usage of a checksum policy by a repository connector in some more detail (the retry logic has been omitted for the sake of brevity): 
     void validateChecksums() throws ChecksumFailureException {
   for (checksum : checksums) {
     switch (checksum.state) {
       case MATCH:
         if (policy.onChecksumMatch(...)) {
           return;
         }
         break;
       case MISMATCH:
         policy.onChecksumMismatch(...);
         break;
       case ERROR:
         policy.onChecksumError(...);
         break;
     }
   }
   policy.onNoMoreChecksums();
 }
 
 void downloadFile() throws Exception {
   ...
   policy = newChecksumPolicy();
   try {
     validateChecksums();
   } catch (ChecksumFailureException e) {
     if (!policy.onTransferChecksumFailure(...)) {
       throw e;
     }
   }
 }
    Checksum policies might be stateful and are generally not thread-safe.

    • Field Detail

      • KIND_UNOFFICIAL

        static final int KIND_UNOFFICIAL
        Bit flag indicating a checksum which is not part of the official repository layout/structure.
        See Also:
        Constant Field Values

    • Method Detail

      • onChecksumMatch

        boolean onChecksumMatch​(java.lang.String algorithm,
                        int kind)
        Signals a match between the locally computed checksum value and the checksum value declared by the remote repository.
        Parameters:
        algorithm - The name of the checksum algorithm being used, must not be null.
        kind - A bit field providing further details about the checksum. See the KIND_* constants in this interface for possible bit flags.
        Returns:
        true to accept the download as valid and stop further validation, false to continue validation with the next checksum.

      • onChecksumMismatch

        void onChecksumMismatch​(java.lang.String algorithm,
                        int kind,
                        ChecksumFailureException exception)
                 throws ChecksumFailureException
        Signals a mismatch between the locally computed checksum value and the checksum value declared by the remote repository. A simple policy would just rethrow the provided exception. More sophisticated policies could update their internal state and defer a conclusion until all available checksums have been processed.
        Parameters:
        algorithm - The name of the checksum algorithm being used, must not be null.
        kind - A bit field providing further details about the checksum. See the KIND_* constants in this interface for possible bit flags.
        exception - The exception describing the checksum mismatch, must not be null.
        Throws:
        ChecksumFailureException - If the checksum validation is to be failed. If the method returns normally, validation continues with the next checksum.

      • onChecksumError

        void onChecksumError​(java.lang.String algorithm,
                     int kind,
                     ChecksumFailureException exception)
              throws ChecksumFailureException
        Signals an error while computing the local checksum value or retrieving the checksum value from the remote repository.
        Parameters:
        algorithm - The name of the checksum algorithm being used, must not be null.
        kind - A bit field providing further details about the checksum. See the KIND_* constants in this interface for possible bit flags.
        exception - The exception describing the checksum error, must not be null.
        Throws:
        ChecksumFailureException - If the checksum validation is to be failed. If the method returns normally, validation continues with the next checksum.

      • onNoMoreChecksums

        void onNoMoreChecksums()
                throws ChecksumFailureException
        Signals that all available checksums have been processed.
        Throws:
        ChecksumFailureException - If the checksum validation is to be failed. If the method returns normally, the download is assumed to be valid.

      • onTransferRetry

        void onTransferRetry()
        Signals that the download is being retried after a previously thrown ChecksumFailureException that is retry-worthy. Policies that maintain internal state will usually have to reset some of this state at this point to prepare for a new round of validation.