I am creating a service that aggregates data and will need to be able to read any unknown JSON document. I have the pipeline defined as follows:
private def pipeline = (
addHeader("Accept", "application/json")
~> sendReceive
~> unmarshal[JsObject] // Need this to work for JsObject or JsArray //
~> recover
)
This will work with a JsObject but not a JsArray. If I change it to a JsArray then it will not (of course) work with a JsObject. My recover method returns a JsObject.
I would love to be able to define this as a JsValue or enforce a Root format, but for JsValue I get the following compiler error:
could not find implicit value for evidence parameter of type spray.httpx.unmarshalling.FromResponseUnmarshaller[spray.json.JsValue]
And Root Formats also error.
I am not sure how to accomplish what I need, any help would be appreciated.
Use Either, Eric! :) If the response will be either JsObject or JsArray then Either is good solution.
private def pipeline =
addHeader("Accept", "application/json")
~> sendReceive
~> unmarshal[Either[JsObject, JsArray]]
~> recover
However, beware that unmarshal[Either[JsObject, JsArray]] tries to parse response as JsObject first and if it fails, tries to parse it as JsArray. This may lead some performance issues.
After reviewing #Mustafa's answer I created the following to avoid the potential performance hit. In the end, I really only need a JSON AST to pass on.
In the most simple terms, I simply created a function to handle it:
def unmarshalJSON(httpResponse: HttpResponse): JsValue = {
httpResponse.entity.asString.parseJson
}
and altered below:
private def pipeline = {
addHeader("Accept", "application/json")
~> sendReceive
~> unmarshalJSON
~> recover
}
I would of course want to beef this up a bit for production level code, but this could be another alternative and allows me to return a JsValue. #Mustafa I would be interested to hear your thoughts.
Related
we are trying to add parameters to a transformation at the runtime. The only possible way to do so, is to set every single parameter and not a node. We don't know yet how to create a node for the setParameter.
Current setParameter:
QName TEST XdmAtomicValue 24
Expected setParameter:
<TempNode> <local>Value1</local> </TempNode>
We searched and tried to create a XdmNode and XdmItem.
If you want to create an XdmNode by parsing XML, the best way to do it is:
DocumentBuilder db = processor.newDocumentBuilder();
XdmNode node = db.build(new StreamSource(
new StringReader("<doc><elem/></doc>")));
You could also pass a string containing lexical XML as the parameter value, and then convert it to a tree by calling the XPath parse-xml() function.
If you want to construct the XdmNode programmatically, there are a number of options:
DocumentBuilder.newBuildingStreamWriter() gives you an instance of BuildingStreamWriter which extends XmlStreamWriter, and you can create the document by writing events to it using methods such as writeStartElement, writeCharacters, writeEndElement; at the end call getDocumentNode() on the BuildingStreamWriter, which gives you an XdmNode. This has the advantage that XmlStreamWriter is a standard API, though it's not actually a very nice one, because the documentation isn't very good and as a result implementations vary in their behaviour.
Another event-based API is Saxon's Push class; this differs from most push-based event APIs in that rather than having a flat sequence of methods like:
builder.startElement('x');
builder.characters('abc');
builder.endElement();
you have a nested sequence:
Element x = Document.elem('x');
x.text('abc');
x.close();
As mentioned by Martin, there is the "sapling" API: Saplings.doc().withChild(elem(...).withChild(elem(...)) etc. This API is rather radically different from anything you might be familiar with (though it's influenced by the LINQ API for tree construction on .NET) but once you've got used to it, it reads very well. The Sapling API constructs a very light-weight tree in memory (hance the name), and converts it to a fully-fledged XDM tree with a final call of SaplingDocument.toXdmNode().
If you're familiar with DOM, JDOM2, or XOM, you can construct a tree using any of those libraries and then convert it for use by Saxon. That's a bit convoluted and only really intended for applications that are already using a third-party tree model heavily (or for users who love these APIs and prefer them to anything else).
In the Saxon Java s9api, you can construct temporary trees as SaplingNode/SaplingElement/SaplingDocument, see https://www.saxonica.com/html/documentation12/javadoc/net/sf/saxon/sapling/SaplingDocument.html and https://www.saxonica.com/html/documentation12/javadoc/net/sf/saxon/sapling/SaplingElement.html.
To give you a simple example constructing from a Map, as you seem to want to do:
Processor processor = new Processor();
Map<String, String> xsltParameters = new HashMap<>();
xsltParameters.put("foo", "value 1");
xsltParameters.put("bar", "value 2");
SaplingElement saplingElement = new SaplingElement("Test");
for (Map.Entry<String, String> param : xsltParameters.entrySet())
{
saplingElement = saplingElement.withChild(new SaplingElement(param.getKey()).withText(param.getValue()));
}
XdmNode paramNode = saplingElement.toXdmNode(processor);
System.out.println(paramNode);
outputs e.g. <Test><bar>value 2</bar><foo>value 1</foo></Test>.
So the key is to understand that withChild() returns a new SaplingElement.
The code can be compacted using streams e.g.
XdmNode paramNode2 = Saplings.elem("root").withChild(
xsltParameters
.entrySet()
.stream()
.map(p -> Saplings.elem(p.getKey()).withText(p.getValue()))
.collect(Collectors.toList())
.toArray(SaplingElement[]::new))
.toXdmNode(processor);
System.out.println(paramNode2);
I am really stuck at this now..
Essentially I have a Java Map, which I would like to pass it to a Javascript Code, so that in my JS code I can use dot notation to refer the keys in this Map. ( I know I can serialize the map into JSON and deserialize it back and pass it into JS, but I don't like that ) I have this piece of the unit code
#Test
public void mapToJsTest() throws Exception{
Map m = Maps.newHashMap();
m.put("name", "john");
NativeObject nobj = new NativeObject();
for (Object k : m.keySet()) {
nobj.defineProperty((String)k, m.get(k), NativeObject.READONLY);
}
engine.eval("function test(obj){ return obj.name;}");
Object obj = ((Invocable)engine).invokeFunction("test", nobj);
Assert.assertEquals(obj, "john");
}
If I am using
org.mozilla.javascript.NativeObject
then the test won't pass,
However, if I am using
sun.org.mozilla.javascript.internal.NativeObject
then the test will pass.
However, we all know that we shouldn't rely on these internal classes, and when I deploy my code on the server side, trying to access
this internal class will cause other problems.
So how do I achieve this with just "org.mozilla.javascript.NativeObject"?
BTW, I am using Rhino
ScriptEngine engine = new ScriptEngineManager().getEngineByName("JavaScript");
For Nashorn, it is much easier, I can pass Map directly into JS code.
Unless you're stuck with older JDK (jdk7 or below) for some reason, I'd recommend moving to jdk8u. You've ES 5.1 compliant JS implementation (Nashorn) that is bundled with JDK8+.
In a controller I have this finder
User.findByEmail('test#test.com')
And works.
Works even if I write
User.findByEmail(null)
But if i write
User.findByEmail(session.email)
and session.email is not defined (ergo is null) it throw exception
groovy.lang.MissingMethodException: No signature of method: myapp.User.findByEmail() is applicable for argument types: () values: []
Is this behavior right?
If i evaluate "session.email" it give me null so I think it must work as it do when I write
User.findByEmail(null)
Even more strange....
If I run this code in groovy console:
import myapp.User
User.findByEmail(null)
It return a user that has null email but if I run the same code a second time it return
groovy.lang.MissingMethodException: No signature of method: myapp.User.findByEmail() is applicable for argument types: () values: []
You can't use standard findBySomething dynamic finders to search for null values, you need to use the findBySomethingIsNull version instead. Try
def user = (session.email ? User.findByEmail(session.email)
: User.findByEmailIsNull())
Note that even if User.findByEmail(null) worked correctly every time, it would not necessarily give you the correct results on all databases as a findBySomething(null) would translate to
WHERE something = null
in the underlying SQL query, and according to the SQL spec null is not equal to anything else (not even to null). You have to use something is null in SQL to match null values, which is what findBySomethingIsNull() translates to.
You could write a static utility method in the User class to gather this check into one place
public static User byOptEmail(val) {
if(val == null) {
return User.findByEmailIsNull()
}
User.findByEmail(val)
}
and then use User.byOptEmail(session.email) in your controllers.
Jeff Brown from grails nabble forum has identified my problem. It's a GORM bug. see jira
More info on this thread
This jira too
I tried with debugger and it looks it should be working, as you write. Maybe the groovy itself is a little bit confused here, try to help it this way:
User.findByEmail( session['email'] )
I've written a lexer and parser using scala.util.parsing.combinators.Parsers. I have a bug in at least one of my productions, but I have so many of them that it is difficult to eyeball them to determine the problem.
What I need is a log of every attempt my Parser makes to match the input with any production; logging all the Success and Failure objects when they are instantiated would be lovely. Unfortunately, the only way I can see to do this is to extend a lot of the basic classes provided by the library, then rewriting my massive parser to extend the new classes.
Is there an easy way to get this logging behavior?
You could use the log combinator to wrap productions of your grammar. Here's the definition in Parsers.scala:
def log[T](p: => Parser[T])(name: String): Parser[T] = Parser{ in =>
println("trying "+ name +" at "+ in)
val r = p(in)
println(name +" --> "+ r)
r
}
Otherwise, I think you should be able to override success and failure, but it would be quite uninformative, since you won't know what production called them.
I'm getting started with Irony (version Irony_2012_03_15) but I pretty quickly got stuck when trying to generate an AST. Below is a completely strpped language that throws the exception:
[Language("myLang", "0.1", "Bla Bla")]
public class MyLang: Grammar {
public NModel()
: base(false) {
var number = TerminalFactory.CreateCSharpNumber("number");
var binExpr = new NonTerminal("binExpr", typeof(BinaryOperationNode));
var binOp = new NonTerminal("BinOp");
binExpr.Rule = number + binOp + number;
binOp.Rule = ToTerm("+");
RegisterOperators(1, "+");
//MarkTransient(binOp);
this.Root = binExpr;
this.LanguageFlags = Parsing.LanguageFlags.CreateAst; // if I uncomment this line it throws the error
}
}
As soon as I uncomment the last line it throws a NullReferenceException in the grammar explorer or when i want to parse a test. The error is on AstBuilder.cs line 96:
parseNode.AstNode = config.DefaultNodeCreator();
DefaultNodeCreator is a delegate that has not been set.
I've tried setting things with MarkTransient etc but no dice.
Can someone help me afloat here? I'm proably missing something obvious. Looked for AST tutorials all over the webs but I can't seem to find an explanation on how that works.
Thanks in advance,
Gert-Jan
Once you set the LanguageFlags.CreateAst flag on the grammar, you must provide additional information about how to create the AST.
You're supposed to be able to set AstContext.Default*Type for the whole language, but that is currently bugged.
Set TermFlags.NoAstNode. Irony will ignore this node and its children.
Set AstConfig.NodeCreator. This is a delegate that can do the right thing.
Set AstConfig.NodeType to the type of the AstNode. This type should be accessible, implement IAstInit, and have a public, no-parameters constructor. Accessible in this case means either public or internal with the InternalsVisibleTo attribute.
To be honest, I was facing the same problem and did not understand Jay Bazuzi answer, though it looks like valid one(maybe it's outdated).
If there's anyone like me;
I just inherited my Grammar from Irony.Interpreter.InterpretedLanguageGrammar class, and it works. Also, anyone trying to get AST working, make sure your nodes are "public" :- )
On top of Jay's and Erti-Chris's responses, this thread is also useful:
https://irony.codeplex.com/discussions/361018
The creator of Irony points out the relevant configuration code in InterpretedLanguageGrammar.BuildAst.
HTH