corda/docs/source/blob-inspector.rst

Blob Inspector
==============

There are many benefits to having a custom binary serialisation format (see :doc:`serialization` for details) but one
disadvantage is the inability to view the contents in a human-friendly manner. The Corda Blob Inspector tool alleviates
this issue by allowing the contents of a binary blob file (or URL end-point) to be output in either YAML or JSON. It
uses ``JacksonSupport`` to do this (see :doc:`json`).

The tool can be downloaded from `here <https://corda.net/resources>`_.

To run simply pass in the file or URL as the first parameter::

    java -jar blob-inspector.jar <file or URL>

Use the ``--help`` flag for a full list of command line options.

When inspecting your custom data structures, there's no need to include the jars containing the class definitions for them
in the classpath. The blob inspector (or rather the serialization framework) is able to synthesize any classes found in the
blob that aren't on the classpath.

Supported formats
~~~~~~~~~~~~~~~~~

The inspector can read **input data** in three formats: raw binary, hex encoded text and base64 encoded text. For instance
if you have retrieved your binary data and it looks like this::

    636f7264610100000080c562000000000001d0000030720000000300a3226e65742e636f7264613a38674f537471464b414a5055...

then you have hex encoded data. If it looks like this it's base64 encoded::

    Y29yZGEBAAAAgMViAAAAAAAB0AAAMHIAAAADAKMibmV0LmNvcmRhOjhnT1N0cUZLQUpQVWVvY2Z2M1NlU1E9PdAAACc1AAAAAgCjIm5l...

And if it looks like something vomited over your screen it's raw binary. You don't normally need to care about these
differences because the tool will try every format until it works.

Something that's useful to know about Corda's format is that it always starts with the word "corda" in binary. Try
hex decoding 636f726461 using the `online hex decoder tool here <https://convertstring.com/EncodeDecode/HexDecode>`_
to see for yourself.

**Output data** can be in either a slightly extended form of YaML or JSON. YaML (Yet another markup language) is a bit
easier to read for humans and is the default. JSON can of course be parsed by any JSON library in any language.

.. note:: One thing to note is that the binary blob may contain embedded ``SerializedBytes`` objects. Rather than printing these
   out as a Base64 string, the blob inspector will first materialise them into Java objects and then output those. You will
   see this when dealing with classes such as ``SignedData`` or other structures that attach a signature, such as the
   ``nodeInfo-*`` files or the ``network-parameters`` file in the node's directory.


Example
~~~~~~~

Here's what a node-info file from the node's data directory may look like:

* YAML:

.. sourcecode:: none

    net.corda.nodeapi.internal.SignedNodeInfo
    ---
    raw:
      class: "net.corda.core.node.NodeInfo"
      deserialized:
        addresses:
        - "localhost:10005"
        legalIdentitiesAndCerts:
        - "O=BankOfCorda, L=London, C=GB"
        platformVersion: 4
        serial: 1527851068715
    signatures:
    - !!binary |-
      VFRy4frbgRDbCpK1Vo88PyUoj01vbRnMR3ROR2abTFk7yJ14901aeScX/CiEP+CDGiMRsdw01cXt\nhKSobAY7Dw==

* JSON:

.. sourcecode:: none

    net.corda.nodeapi.internal.SignedNodeInfo
    {
      "raw" : {
        "class" : "net.corda.core.node.NodeInfo",
        "deserialized" : {
          "addresses" : [ "localhost:10005" ],
          "legalIdentitiesAndCerts" : [ "O=BankOfCorda, L=London, C=GB" ],
          "platformVersion" : 4,
          "serial" : 1527851068715
        }
      },
      "signatures" : [ "VFRy4frbgRDbCpK1Vo88PyUoj01vbRnMR3ROR2abTFk7yJ14901aeScX/CiEP+CDGiMRsdw01cXthKSobAY7Dw==" ]
    }

Notice the file is actually a serialised ``SignedNodeInfo`` object, which has a ``raw`` property of type ``SerializedBytes<NodeInfo>``.
This property is materialised into a ``NodeInfo`` and is output under the ``deserialized`` field.