I am trying to understand the syntax for boost property tree, but it's not jumping out at me. I am using a boost property_tree to represent a simple json document. In one case, I want to construct such a document, so I have:
property_tree::wptree json;
json.put(_eventName.c_str(), L"");
And this works fine, but sometimes I want to include values underneath the event like:
{ "event_name": {
"time":"4pm",
"day":"saturday" } }
What I want to do is:
property_tree::wptree json;
auto subTree = json.put(_eventName.c_str(), L"");
for(auto val : values)
subTree.put(val->first.c_str(), val->second.c_str());
but this seems to throw an exception. I've attempted to get a handle on this through the online docs, but I'm still a little unsure. I'm thinking maybe the solution is to construct a new wptree with the sub values, and then add that tree to the json document, but that seems a bit counterintuitive to me. Any advice?
Related
I've been working with FlatBuffers as a solution for various things in my project, one of them specifically being JSON support. However, while FB natively supports JSON generation, the documentation for flatbuffers is poor, and the process is somewhat cumbersome. Right now, I am working in the Object->JSON direction. The issue I am having doesn't really arise the other way around (I think).
I currently have JSON generation working per an example I found here (line 630, JsonEnumsTest()) - by parsing a .fbs file into a flattbuffers::Parser, building and packaging my flatbuffer object, then running GenerateText() to generate a JSON string. The code I have is simpler than the example in test.cpp, and looks vaguely like this:
bool MyFBSchemaWrapper::asJson(std::string& jsonOutput)
{
//**This is the section I don't like having to do
std::string schemaFile;
if (flatbuffers::LoadFile((std::string(getenv("FBS_FILE_PATH")) + "MyFBSchema.fbs").c_str(), false, &schemaFile))
{
flatbuffers::Parser parser;
const char *includePaths[] = { getenv("FBS_FILE_PATH");
parser.Parse(schemaFile.c_str(), includePaths);
//**End bad section
parser.opts.strict_json = true;
flatbuffers::FlatBufferBuilder fbBuilder;
auto testItem1 = fbBuilder.CreateString("test1");
auto testItem2 = fbBuilder.CreateString("test2");
MyFBSchemaBuilder myBuilder(fbBuilder);
myBuilder.add_item1(testItem1);
myBuilder.add_item2(testItem2);
FinishMyFBSchemaBuffer(fbBuilder, myBuilder.finish());
auto result = GenerateText(parser, fbBuilder.GetBufferPointer(), &jsonOutput);
return true;
}
return false;
}
Here's my issue: I'd like to avoid having to include the .fbs files to set up my Parser. I don't want to clutter an already large monolithic program by adding even more random folders, directories, environment variables, etc. I'd like to be able to generate JSON from the compiled FlatBuffer schemas, and not have to search for a file to do so.
Is there a way for me to avoid having to read back in my .fbs schemas into the parser? My intuition is pointing to no, but the lack of documentation and community support on the topic of FlatBuffers & JSON is telling me there might be a way. I'm hoping that there's a way to use the already generated MyFBSchema_generated.h to create a JSON string.
Yes, see Mini Reflection in the documentation: http://google.github.io/flatbuffers/flatbuffers_guide_use_cpp.html
I've encountered a problem using the xerces-dom library:
When you're adding a comments to the xml-tree like:
DOMDocument* doc = impl->createDocument(0, L"root", 0);
DOMElement* root = doc->getDocumentElement();
DOMComment* com1 = doc->createComment(L"SetA -- DataA");
DOMComment* com2 = doc->createComment(L"SetB -- DataB");
doc->insertBefore(com1, root);
doc->insertBefore(com2, root);
That will create the following xml-tree:
<?xml version="1.0" encoding="UTF-8" standalone="false"?>
<!--SetA -- DataA-->
<!--SetB -- DataB-->
<root/>
which is indeed invalid xml.
The same can be done with processing instructions by using ?> as data:
DOMProcessingInstruction procInstr = doc->createProcessingInstruction(L"target", L"?>");
My question:
Is there a way i can configure xerces to not create these kind of comments or do i have to check for these things myself?
And my other question: Why isn't it possible to just always escape characters like <>&'", even in comments and processing instructions, in order to avoid these kind of problems?
A DOMDocument is not an XML document. It is supposed to represent one, but it is conceivable that a valid DOM may not be serializable into a valid XML document (the converse should be less likely). Indeed this appears to be the case here:
Neither the Level 1 or Level2 two specs say anything about this, but the Level 3 DOM specification added this sentence about the DOMComment interface:
No lexical check is done on the content of a comment and it is therefore possible to have the character sequence "--" (double-hyphen) in the content, which is illegal in a comment per section 2.5 of [XML 1.0]. The presence of this character sequence must generate a fatal error during serialization.
So Xerces is operating within the DOM Level 3 specification even if it accepts a comment with '--' in it, as long as it bombs if you go to serialize it.
Not a great situation, but it makes sense because DOM was originally intended to represent XML Documents that have been read in, not to create new ones. So it is liberal in what it can represent. Fine for reading - a DOMComment can represent anything (and more) the XML document can, but a bit annoying that it doesn't catch the invalid string when you createComment().
Checking DOMDocumentImpl.cpp we see:
DOMComment *DOMDocumentImpl::createComment(const XMLCh *data)
{
return new (this, DOMMemoryManager::COMMENT_OBJECT) DOMCommentImpl(this, data);
}
And in DOMCommentImpl.cpp we have just:
DOMCommentImpl::DOMCommentImpl(DOMDocument *ownerDoc, const XMLCh *dat)
: fNode(ownerDoc), fCharacterData(ownerDoc, dat)
{
fNode.setIsLeafNode(true);
}
Finally we see in DOMCharacterDataImpl.cpp that there is no chance of validation up front - it just saves the user provided string without checking it.
DOMCharacterDataImpl::DOMCharacterDataImpl(DOMDocument *doc, const XMLCh *dat)
{
fDoc = (DOMDocumentImpl*)doc;
XMLSize_t len=XMLString::stringLen(dat);
fDataBuf = fDoc->popBuffer(len+1);
if (!fDataBuf)
fDataBuf = new (fDoc) DOMBuffer(fDoc, len+15);
fDataBuf->set(dat, len);
}
Sadly, no Xerces does not have an option or even a nice hook to check this for you. And because the Level 3 spec seems to demand that "No lexical check is done", it probably isn't even legal to add one.
The answer to your second question is simpler to answer: Because that's the way they wanted it defined it. See the XML 1.1 spec for example:
Comments
[15] Comment ::= '<!--' ((Char - '-') | ('-' (Char - '-')))* '-->'
It is similar for PIs.
The grammar simply does not allow for escapes. Seems about right: baroque and broke.
Maybe there is a way to catch the error on serialization or normalization, but I wasn't able to confirm whether Xerces 3.1 can. To be safe I think the best way is to wrap createComment() and check for it before creating the node, or walk the tree and check it yourself.
I'm trying to use xerces-c in order to parse a rather massive XML document generated from StarUML in order to change some things, but I'm running into issues getting the xpath query to work because it keeps crashing.
To simplify things I split out part of the file into a smaller XML file for testing, which looks like this:
<?xml version="1.0" encoding="utf-8"?>
<XPD:UNIT xmlns:XPD="http://www.staruml.com" version="1">
<XPD:HEADER>
<XPD:SUBUNITS>
</XPD:SUBUNITS>
</XPD:HEADER>
<XPD:BODY>
<XPD:OBJ name="Attributes[3]" type="UMLAttribute" guid="onMjrHQ0rUaSkyFAWtLzKwAA">
<XPD:ATTR name="StereotypeName" type="string">ConditionInteraction</XPD:ATTR>
</XPD:OBJ>
</XPD:BODY>
</XPD:UNIT>
All I'm trying to do for this example is to find all of the XPD:OBJ elements, of which there is only one. The problem seems to stem from trying to query with the namespace. When I pass a very simple xpath query of XPD:OBJ it will crash, but if I pass just OBJ it won't crash but it won't find the XPD:OBJ element.
I assume there's some important property or setting that I'm missing during initialization that I need to set but I have no idea what it might be. I looked up all of the properties of the parser having to do with namespace and enabled the ones I could but it didn't help at all so I'm completely stuck. The initialization code looks something like this, with lots of things removed obviously:
const tXercesXMLCh tXMLManager::kDOMImplementationFeatures[] =
{
static_cast<tXercesXMLCh>('L'),
static_cast<tXercesXMLCh>('S'),
static_cast<tXercesXMLCh>('\0')
};
// Instantiate the DOM parser.
fImplementation = static_cast<tXercesDOMImplementationLS *>(tXercesDOMImplementationRegistry::getDOMImplementation(kDOMImplementationFeatures));
if (fImplementation != nullptr)
{
fParser = fImplementation->createLSParser(tXercesDOMImplementationLS::MODE_SYNCHRONOUS, nullptr);
fConfig = fParser->getDomConfig();
// Let the validation process do its datatype normalization that is defined in the used schema language.
//fConfig->setParameter(tXercesXMLUni::fgDOMDatatypeNormalization, true);
// Ignore comments and whitespace so we don't get extra nodes to process that just waste time.
fConfig->setParameter(tXercesXMLUni::fgDOMComments, false);
fConfig->setParameter(tXercesXMLUni::fgDOMElementContentWhitespace, false);
// Setup some properties that look like they might be required to get namespaces to work but doesn't seem to help at all.
fConfig->setParameter(tXercesXMLUni::fgXercesUseCachedGrammarInParse, true);
fConfig->setParameter(tXercesXMLUni::fgDOMNamespaces, true);
fConfig->setParameter(tXercesXMLUni::fgDOMNamespaceDeclarations, true);
// Install our custom error handler.
fConfig->setParameter(tXercesXMLUni::fgDOMErrorHandler, &fErrorHandler);
}
Then later on I parse the document, find the root node, and then run the xpath query to find the node I want. I'll leave out the bulk of that and just show you where I'm running the xpath query in case there's something obviously wrong there:
tXercesDOMDocument * doc; // Comes from parsing the file.
tXercesDOMNode * contextNode; // This is the root node retrieved from the document.
tXercesDOMXPathResult * xPathResult;
doc->evaluate("XPD:OBJ", contextNode, nullptr, tXercesDOMXPathResult::ORDERED_NODE_SNAPSHOT_TYPE), xPathResult);
The call to evaluate() is where it crashes somewhere deep inside xerces that I can't see very clearly, but from what I can see there are a lot of things that look deleted or uninitialized so I'm not sure what's causing the crash exactly.
So is there anything here that looks obviously wrong or missing that is required to make xerces work with XML namespaces?
The solution was right in front of my face the whole time. The problem was that you need to create and pass a resolver to the evaluate() call or else it will not be able to figure out any of the namespaces and will throw an exception. The crash seems to be a bug in xerces since it's crashing on trying to throw the exception when it can't resolve the namespace. I had to debug deep into the xerces code to find it, which gave me the solution.
So to fix the problem I changed the call to evaluate() slightly to create a resolver with the root node and now it works perfectly:
tXercesDOMDocument * doc; // Comes from parsing the file.
tXercesDOMNode * contextNode; // This is the root node retrieved from the document.
tXercesDOMXPathResult * xPathResult;
// Create the resolver with the root node, which contains the namespace definition.
tXercesDOMXPathNSResolver * resolver(doc->createNSResolver(contextNode));
doc->evaluate("XPD:OBJ", contextNode, resolver, tXercesDOMXPathResult::ORDERED_NODE_SNAPSHOT_TYPE), xPathResult);
// Make sure to release the resolver since anything created from a `create___()`
// function has to be manually released.
resolver->release();
I'm trying to use the Code Templates feature with PHP in NetBeans (7.3), however I'm finding it rather limited. Given the following desired output:
public function addFoo(Foo $foo) {
$this->fooCollection[] = $foo;
}
I'm trying to have every instance of "foo"/"Foo" be variable; so I used a variable:
public function add${name}(${name} $$${name}) {
$this->${name}Collection[] = $$${name};
}
Of course, when expanded there isn't any regard given to the desired capitalization rules, because I can't find a way to implement that; the result being (given I populate ${name} with "Foo"):
public function addFoo(Foo $Foo) { // note the uppercase "Foo" in the argument
$this->FooCollection[] = $Foo; // and collection property names...
} // not what I had in mind
Now, I've read that NetBeans supports FreeMarker in it's templates, but that seems to be only for file-templates and not snippet-templates like these.
As far as I can tell, the FreeMarker version would look something like the following; however, it doesn't work, and ${name?capitalize} is simply seen as another variable name.
public function add${name?capitalize}(${name?capitalize} $$${name}) {
$this->${name}Collection[] = $$${name};
}
Passing "foo", allowing capitalize to fix it for type-names, second-words, etc.
Is there any way to get FreeMarker support here, or an alternative?
I'm open to any suggestions really; third-party plugins included. I just don't want to have to abandon NetBeans.
Addendum
The example given is trivial; an obvious solution for it specifically would be:
public function add${upperName}(${upperName} $$${lowerName}) {
$this->${lowerName}Collection[] = $$${lowerName};
}
Where upper/lower would be "Foo"/"foo" respectively. However, it's just an example, and I'm looking for something more robust in general (such as FreeMarker support)
I am working on a small programm written in C++ using the QT Framework (v. 4.7).
The task I want to accomplish is opening an existing xml-document, add a node within its structure and save the document to the file I read it from before. I have tried this using something like that:
QFile xmlIn(AFileName);
QDomDocument doc("report_1");
if (xmlIn.open(QIODevice::ReadOnly)) {
if (doc.setContent(&xmlIn)) {
QDomElement docElem = doc.documentElement();
QDomNode n = docElem.firstChild();
// Do something with the element here
n = n.nextSibling();
}
}
// Code for saving the edited QDomDocument comes here
But I have the strong feeling that I am overseeing an essential part here, because this seems to be a task that is very common and normally the QT Lib should provide everything one could want :D
Please enlighten me :)
Use a "QXmlStreamWriter"...
QXmlStreamWriter lStreamWriter;
if(lProjectFile.open(QIODevice::WriteOnly|QFile::Text))
{
lStreamWriter.setDevice(&lProjectFile);
lStreamWriter.writeStartDocument();
lStreamWriter.writeStartElement("element");
lStreamWriter.writeAttribute("attribute","value");
lStreamWriter.writeEndElement();
lStreamWriter.writeEndDocument();
lProjectFile.close();
}