268 lines
11 KiB
C++
Executable File
268 lines
11 KiB
C++
Executable File
/******************************************************************************
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Copyright (c) 2009-2010, Terry Caton
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All rights reserved.
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Redistribution and use in source and binary forms, with or without
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modification, are permitted provided that the following conditions are met:
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* Redistributions of source code must retain the above copyright
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notice, this list of conditions and the following disclaimer.
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* Redistributions in binary form must reproduce the above copyright
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notice, this list of conditions and the following disclaimer in the
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documentation and/or other materials provided with the distribution.
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* Neither the name of the projecct nor the names of its contributors
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may be used to endorse or promote products derived from this software
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without specific prior written permission.
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THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
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ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR
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ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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(INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
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ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
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SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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******************************************************************************/
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#include "json/reader.h"
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#include "json/writer.h"
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#include "json/elements.h"
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#include <sstream>
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int main()
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{
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using namespace json;
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/* we'll generate:
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{
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"Delicious Beers" : [
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{
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"Name" : "Schlafly American Pale Ale",
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"Origin" : "St. Louis, MO, USA",
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"ABV" : 5.9,
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"BottleConditioned" : true
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},
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{
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"Name" : "John Smith's Extra Smooth",
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"Origin" : "Tadcaster, Yorkshire, UK",
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"ABV" : 3.8,
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"Bottle Conditioned" : false
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}
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]
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}
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*/
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////////////////////////////////////////////////////////////////////
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// construction
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// we can build a document piece by piece...
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Object objAPA;
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objAPA["Name"] = String("Schlafly American Pale Ale");
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objAPA["Origin"] = String("St. Louis, MO, USA");
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objAPA["ABV"] = Number(3.8);
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objAPA["BottleConditioned"] = Boolean(true);
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Array arrayBeer;
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arrayBeer.Insert(objAPA);
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Object objDocument;
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objDocument["Delicious Beers"] = arrayBeer;
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Number numDeleteThis = objDocument["AnotherMember"];
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// ...or, we can use UnknownElement's chaining child element access to quickly
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// construct the remainder
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objDocument["Delicious Beers"][1]["Name"] = String("John Smith's Extra Smooth");
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objDocument["Delicious Beers"][1]["Origin"] = String("Tadcaster, Yorkshire, UK");
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objDocument["Delicious Beers"][1]["ABV"] = Number(3.8);
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objDocument["Delicious Beers"][1]["BottleConditioned"] = Boolean(false);
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////////////////////////////////////////////////////////////////////
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// interpretation
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// perform all read operations on a const ref, otherwise we may end up
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// manipulating the document instead of catching errors
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const Object& objRoot = objDocument;
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// the return type of Object::operator[string] & Array::operator[size_t] is UnknownElement, which
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// provides implicit casting to any of the other element types...
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const Array& arrayBeers = objRoot["Delicious Beers"];
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const Object& objBeer0 = arrayBeers[0];
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const String& strName0 = objBeer0["Name"];
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// ...it also supports operator[string] & operator[size_t] itself, which takes the implicit casting
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// one step further. operator[string] implicitly casts to Object, and operator[size_t] to Array.
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// the return value is another UnknownElement, so these operations can be strung together
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const Number numAbv1 = objRoot["Delicious Beers"][1]["ABV"];
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std::cout << "First beer name: " << strName0.Value() << std::endl;
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std::cout << "First beer ABV: " << numAbv1.Value() << std::endl;
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// we can also iterate through the child elements of an array or object, which is necessary
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// when we don't know the structure of the document
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Array::const_iterator itBeers(arrayBeers.Begin()),
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itBeersEnd(arrayBeers.End());
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for (; itBeers != itBeersEnd; ++itBeers)
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{
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// remember, *itArray is an UnknownElement, which can be implicitly cast to another element type
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const Object& objBeer = *itBeers;
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Object::const_iterator itBeerFacts(objBeer.Begin()),
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itBeerFactsEnd(objBeer.End());
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for (; itBeerFacts != itBeerFactsEnd; ++itBeerFacts)
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{
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const Object::Member& member = *itBeerFacts;
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const std::string& name = member.name;
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const UnknownElement& element = member.element;
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// if we didn't know the structure of the itBeerFacts subtree, we could visit it
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// element.Accept(nonExistantVisitor);
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}
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}
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// everything's cool until we try to access a non-existent array element
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try
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{
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std::cout << "Expecting exception: Array out of bounds" << std::endl;
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const String& strName2 = arrayBeers[2];
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}
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catch (const Exception& e)
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{
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std::cout << "Caught json::Exception: " << e.what() << std::endl << std::endl;
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}
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// an exception will be thrown when expected data not found, since "Rice" is never a member of good beer
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try
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{
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std::cout << "Expecting exception: Object member not found" << std::endl;
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const Boolean& boolRice = objRoot["Delicious Beers"][1]["Rice"];
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}
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catch (const Exception& e)
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{
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std::cout << "Caught json::Exception: " << e.what() << std::endl << std::endl;
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}
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// we'll also get an error if the document structure isn't quite what we expect
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try
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{
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// objRoot["Delicious Beers"] is an Array, not another Object, so the second chained operator[string] will fail
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std::cout << "Expecting exception: Bad cast" << std::endl;
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const UnknownElement& elem = objRoot["Delicious Beers"]["Some Object Member"];
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}
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catch (json::Exception& e)
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{
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std::cout << "Caught json::Exception: " << e.what() << std::endl << std::endl;
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}
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////////////////////////////////////////////////////////////////////
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// document deep copying
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// we can make an exact duplicate too
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Object objRoot2 = objRoot;
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// the two documents should start out equal
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bool bEqualInitially = (objRoot == objRoot2);
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std::cout << "Document copies should start out equivalent. operator == returned: "
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<< (bEqualInitially ? "true" : "false") << std::endl;
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// prove objRoot2 is a deep copy of objRoot:
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// remove Beers[1]
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Array& array = objRoot2["Delicious Beers"];
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array.Erase(array.Begin()); // trim it down to one. this leaves elemRoot the same
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// the two documents should start out equal
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bool bEqualNow = (objRoot == objRoot2);
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std::cout << "Document copies should now be different. operator == returned: "
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<< (bEqualNow ? "true" : "false") << std::endl << std::endl;
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////////////////////////////////////////////////////////////////////
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// read/write sanity check
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// write it out to a string stream (file stream would work the same)....
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std::cout << "Writing file out...";
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std::stringstream stream;
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Writer::Write(objRoot, stream);
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// ...then read it back in. we know it's an Object
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std::cout << "then reading it back in." << std::endl;
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Object elemRootFile;
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Reader::Read(elemRootFile, stream);
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// still look right?
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bool bEquals = (objRoot == elemRootFile);
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std::cout << "Original document and streamed document should be equivalent. operator == returned: "
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<< (bEquals ? "true" : "false") << std::endl << std::endl;
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////////////////////////////////////////////////////////////////////
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// document read error handling
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// mis-predicting type type will fail with a parse error. we'll try reading an array into an object
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try
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{
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std::istringstream sBadDocument("[1, 2]"); // missing comma!
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std::cout << "Reading Object-based document into an Array; expecting Parse exception" << std::endl;
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Object objDocument;
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Reader::Read(objDocument, sBadDocument);
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}
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catch (Reader::ParseException& e)
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{
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// lines/offsets are zero-indexed, so bump them up by one for human presentation
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std::cout << "Caught json::ParseException: " << e.what() << ", Line/offset: " << e.m_locTokenBegin.m_nLine + 1
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<< '/' << e.m_locTokenBegin.m_nLineOffset + 1 << std::endl << std::endl;
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}
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// reading in a slightly malformed document may result in a parse error
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try
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{
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std::istringstream sBadDocument("[1, 2 3]"); // missing comma!
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std::cout << "Reading malformed document; expecting Parse exception" << std::endl;
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Array arrayDocument;
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Reader::Read(arrayDocument, sBadDocument);
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}
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catch (Reader::ParseException& e)
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{
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std::cout << "Caught json::ParseException: " << e.what() << ", Line/offset: " << e.m_locTokenBegin.m_nLine + 1
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<< '/' << e.m_locTokenBegin.m_nLineOffset + 1 << std::endl << std::endl;
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}
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// reading in gibberish will generate a scan error
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try
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{
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std::istringstream sBadDocument("[true, false, true, #.&@k*k4L!`1");
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std::cout << "Reading complete garbage; expecting Scan exception" << std::endl;
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Array arrayDocument;
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Reader::Read(arrayDocument, sBadDocument);
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}
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catch (Reader::ScanException& e)
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{
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std::cout << "Caught json::ScanException: " << e.what() << ", Line/offset: " << e.m_locError.m_nLine + 1
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<< '/' << e.m_locError.m_nLineOffset + 1 << std::endl << std::endl;
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}
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try {
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std::istringstream sIncompleteDocument("[ true, ");
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std::cout << "Reading incomplete document; expecting Parse exception" << std::endl;
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json::Array arrayDocument;
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json::Reader::Read(arrayDocument, sIncompleteDocument);
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}
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catch (Reader::ParseException& e)
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{
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std::cout << "Caught json::ParseException: " << e.what() << ", Line/offset: " << e.m_locTokenBegin.m_nLine + 1
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<< '/' << e.m_locTokenBegin.m_nLineOffset + 1 << std::endl << std::endl;
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}
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return 0;
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}
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