corda/docs/source/blob-inspector.rst

Blob Inspector

There are many benefits to having a custom binary serialisation format (see serialization for details) but one disadvantage is the inability to view the contents in a human-friendly manner. The 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 json).

The latest version of the tool can be downloaded from here.

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 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:

-\-format=YAML :

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==

-\-format=JSON :

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.