I am new to ANTLR and trying to see if ANTLR fit into my scenario or I should stick to JSON deserialization library and write some custom code.
Input text is a JSON which represents an expression like
{
"Operator":"ADD",
"Operands": [{"Operator":"ADD", "Operands":[{"OperandValue":23},{"OperandValue":32} ]},
{"Operator":"ADD", "Operands":[{"OperandValue":11},{"OperandValue":12} ]}]}
}
list of Operators can evolve
JSON is created programmatically and not manually created by users by hand.
I have to read this JSON and validate it and give meaningful error messages to my client.
If JSON in valid/parsed, I have to translate JSON to TSQL code and execute on SQL server.
All my code will be in C# and I need:
max Debug support and ease
unit testability
less custom code
min. learning
With above two needs, I tried to write a rough ANTLR grammar and custom code and below are my observation
ANTLR in a way my logic will reside grammar file, which might be difficult to
debug writing grammar for new comer. and unit test. for doing my grammar POC I was relying only context.GetText() property to figure out where I am currently and change my grammar.
I have to write a modularized grammar(building blocks), so that I can have visitor for my smallest part and more manageable visitor class.
How can I give more meaning full messages to my clients, with them having least knowledge of my grammar parsing engine?
custom JSON deserialization (JSON.NET)
code easy to debug, and everyone understands. I get a JSON reader and write condition to check if JSON Object or JsonArray and if it has Property Operator with value ADD and similar.
custom code I can give more meaningful validation failure messages.
To me ANTLR seems to have high value when your input is not highly structured and you don't have available parsers, but in case of JSON it doesn't give much value add over JSON parsers.
Is ANTLR meant for this scenario?
Related
Is there any way of matching non JSON bodies (either XML, byte or whatever). Looking for the Python solution, however will appreciate any ideas behind that (even monkeypatching).
It's possible, but not directly supported.
Currently there's only the ability to match JSON. You can fake non-JSON matching by expecting a string body, but then you won't be able to use pact's built in matchers- which might mean your tests will be data dependent unless you do a bit of leg work.
There is a stub for xml support, but it's not currently implemented.
If you're willing to get your hands dirty in Ruby (not that different to Python!) you can write your own matcher. I can show you how to configure the pact-provider-verifier to use the custom matching code. Currently, if you use a content type that is not JSON, as J_A_X says, it will do an exact string diff.
I used the following - https://developer.xamarin.com/guides/xamarin-forms/application-fundamentals/custom-renderer/hybridwebview/ to implement a hybrid webview. All works fine expect the part where I need to call the C# function from Javascript. The C# handler gets called but from the article, it seems like I can only get a single parameter passed to C#. So message.Body.ToString() gives me the arguments passed from Javascript. I however want to pass atleast to arguments. Can anybody please show me how I can achieve this.
It looks like you can only pass one parameter through. Hence you just need to develop your own way to pass more information through. You could for example create a class and serialize it in JSON, then deserialize it at the other end. JSON serializers and deserializers are widely available in .NET and JS, this shouldn't be much of a problem at all.
Or if the data is really simple, e.g. 2 numbers, you could do 1#4, and split via the hash at the other end.
Is there any way to parse source string with custom (e)bnf and get AST as json?
Let me explain what do i need:
I have source string and bnf grammar (as string too).
I put EBNF as lexer.
Add source.
Get AST and save it as JSON.
"EBNF as lexer" is nonsensical. But the rest of your question can be interpreted as, "can I get a parser driven by an EBNF to produce an AST in JSON form?"
Sure.
Most parser generators accept (E)BNF and "parse". Most of them don't automatically produce an AST; they make the programmer define how each rule should generate tree nodes. Those won't work for your task.
Some do generate ASTs as data structures automatically using just the BNF and a source file: ANTLR4 (I think), and our DMS Software Reengineering Toolkit. Neither of these produce JSON directly, but in both cases it should be straighforward to write (once) a generic tree-walker that spits JSON.
DMS's BNF will handle any context-free grammar using just BNF rules. ANTLR4 handles most grammars but has restrictions on what you can write (e.g., certain kinds of left recursion are verboten), and requirements for you to add extra disambiguating information where the grammar isn't LL(1).
DMS will export XML directly. See this example.
I'm writing an API that converts actions performed by a non-technical user into Salesforce.com SOQL 'SELECT', 'UPSERT', and 'DELETE' statements. Is there any resource, library, etc. out there that could validate the syntax of the generated SOQL? I'm the only one at my company with any experience with SOQL, so I'd love to place it into a set of automated tests so that other developers enhancing (or fixing) the SOQL generation algorithm know if it's still functioning properly.
I know one solution here is to just make these integration tests. However, I'd rather avoid that for three reasons:
I'd need to maintain another Salesforce.com account just for tests so we don't go over our API request cap.
We'll end up chasing false positives whenever there are connectivity issues with Salesforce.com.
Those other developers without experience will potentially need to figure out how to clean up the test Salesforce.com instance after DML operation test failures (which really means I'll need to clean up the instance whenever this occurs).
You might solve your problem by using the SoqlBuilder library. It generates SOQL for you and is capable of producing SOQL statements that would be quite error prone to create manually. The syntax is straight forward and I've used it extensively with very few issues.
I found another way to do this.
Salesforce.com posted their SOQL notation in Backus-Noir Form (BNF) here:
http://www.salesforce.com/us/developer/docs/api90/Content/sforce_api_calls_soql_bnf_notation.htm
This means you can use a BNF-aware language recognition tool to parse the SOQL. One of the most common tools, ANTLR, does this and is free. Following the ANTLR example, pass the SOQL grammar into its grammar compiler to get a Lexer and a Parser in your desired language (C#, Java, Python, etc.). Then you can pass the actual SOQL statements you want to validate into the Lexer, and then your Lexer tokens into your Parser, to break apart the SOQL statements. If your Lexer or Parser fails, you have invalid SOQL.
I can't think of a way to do this from outside of Salesforce (and even in Apex I've only got one idea right now that may not work), but I can think of two suggestions that may be of help:
Validate queries by running them, but do them in batches using a custom web service. i.e. write a web service in Apex that can accept up to 100 query strings at once, have it run them and return the results. This would drastically reduce the number of API calls but of course it won't work if you're expecting a trial-and-error type setup in the UI.
Use the metadata API to pull down information on all objects and their fields, and use those to validate that at least the fields in the query are correct. Validating other query syntax should be relatively straight forward, though conditionals may get a little tricky.
You can make use of the salesforce develop nuget packages that leverages SOAP API
Our Flex app would like to work with requests and responses as object graphs (nothing unusual there) e.g. response becomes the model of some view, and would be a structure with several layers of nesting.
** Now, ideally we would like to use the same client (and server) side objects for different message formats e.g. XML and AMF, and have a pluggable serialization/de-serialization layer (!)
AMF has serialization and matching of client to server using
[RemoteClass(alias="samples.contact.Contact")]
but it seems there is no equivalent for XML.
I am (somewhat optimistically) looking for a neat way of serializing the object graph to XML, to send through a HTTPService from the client.
For responses, the default 'object' and 'E4X' provide some de-serialization. This is handy, but of course we don't have the niceties of unpacking the XML back into specific AS classes like we do with AMF.
Any suggestions?
(did have one idea come through about wrapping/casting object as XML or XMLList - this does not seem to work, however)
Update:
Both these libraries look useful, and I will very likely use them at some point.
For now, I really need the simplicity of re-using the metadata set for the AMF3 serialization which we are using in any case ([RemoteClass],[Transient])
.. so the best option at the moment is AMFX - used Flex Data Services for AMF transfer using XML - classes in mx.messaging.channels.amfx package - only drawback at the moment is any Externalizable class is transformed into a Hex byte stream - and ArrayCollection is Externalizable! (hoping to workaround by serializing the internal Array in a subclass ..)
Hope that's useful to someone ..
Regarding the Xml serialization I can give you a starting point (as biased as it may be, though :D).
I am working on a project that allows for automatic conversion of AS3 objects to and from xml. It basically uses annotations on the model objects you use for communication in order to construct the xml structure or populating an object from xml.
It is called FlexXB and you can check it out at http://code.google.com/p/flexxb/.
I started this project cos I got into the same issues at work (namely I have a server that communicates through xml) and I hoped it be of use to someone else.
Cheers,
Alex
Yet another project: FleXMLer (http://code.google.com/p/flexmler/).
It has both the straightforward attitude of asx3m where you can just call:
new FleXMLer().serialize(obj);
Or you can customize XML element names, skip elements and tweak the way arrays and hash tables are serialized.
Would appreciate your input.
checkout asx3m project at http://code.google.com/p/asx3m
It's an AS3 port of Java XStream serialization library and works pretty well.
I made it because I had to connect to a server platform that used XStream for exchanging data objects and put a lot of work in it.
It can be extended to serialize AS3 objects to any format (JSON for example) and could leverage power of user defined metatags.
Cheers,
Tomislav
There's a library including JSON available from Adobe, too. And since ActionScript is a superset of JavaScript ... and JSON is increasingly supported cross-framework ...