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Defining a package to read JSON documents of unknown structure Description The package 'json' defines the new types 'jobj',
'jarr', 'jval' and 'jnull' for representing JSON documents
of unknown structure and provides parsing functionality for
reading JSON documents into these structures. Like jparse.mos it relies on the callback-based 'jsonparse' functionality of mmxnl. The model file 'readjson.mos' shows three different methods of reading the JSON database file 'bookexamplesl.json' (documenting the example models from the book 'Applications of optimization with Xpress-MP') into Mosel structures, namely (1) representation as 'xmldoc' using mmxml functionality for loading JSON documents, (2) representation via specific user-defined record structures that are populated by a call to the mmhttp routine 'jsonread', and (3) using the types defined by the package 'json'. To run this example, you first need to compile the package (resulting in the BIM file 'json.bim'). You may then execute the example in the same directory that contains this BIM file.
Source Files By clicking on a file name, a preview is opened at the bottom of this page.
readjson.mos (!****************************************************** Mosel Example Programs ====================== file readjson.mos ````````````````` Alternative JSON reading methods, working with * an xmldoc structure, or * specific user-defined record structures, or * union-based types defined by the package json.mos -- Note: The package 'json' (file json.mos) needs to be compiled before executing this model -- (c) 2022 Fair Isaac Corporation author: S.Heipcke, Mar 2022, rev. Dec. 2022 *******************************************************!) model "Read book examples from JSON" uses "mmxml", "mmsystem", "mmhttp" uses ":json.bim" ! Uncomment the following line in place of the previous if you see the ! compilation error message "Package ':json.bim' not found" ! uses "json" FNAME:="bookexamplesl.json" !**** Using mmxml functionality to read the JSON file into an xmldoc structure declarations exampleDB,newdoc: xmldoc dirs,expls,files: list of integer end-declarations writeln("****Reading JSON into xmldoc structure****") jsonload(exampleDB,FNAME) save(exampleDB,"") ! Display in XML format to visualize xmldoc representation root:=getnode(exampleDB,"*") if root>0 and getattr(exampleDB,root,"jst")="arr" then getnodes(exampleDB, "jsv/jsv[@jst='obj']", dirs) forall(d in dirs) do writeln(getvalue(exampleDB,getnode(exampleDB,d,"directory")), " - ", getvalue(exampleDB,getnode(exampleDB,d,"title")) ) getnodes(exampleDB, d, "models/jsv[@jst='obj']", expls) forall(m in expls) if getnode(exampleDB,m,"modFile")>0 then writeln(" "*10, getvalue(exampleDB,getnode(exampleDB,m,"modTitle")), ": ", getvalue(exampleDB,getnode(exampleDB,m,"modFile")) ) else getnodes(exampleDB,m,"modFileL/jsv",files) writeln(" "*10, getvalue(exampleDB,getnode(exampleDB,m,"modTitle")), ": ", union(f in files) [getvalue(exampleDB,f)] ) end-if end-do asproc(copynode(exampleDB, getnode(exampleDB,"jsv/jsv[1]/models/jsv[1]"), newdoc,0,XML_FIRSTCHILD)) write("First example: "); jsonsave(newdoc,"") asproc(copynode(exampleDB, getnode(exampleDB,"jsv/jsv[2]"), newdoc,0,XML_FIRSTCHILD)) write("Second directory: "); jsonsave(newdoc,"") end-if !**** User type definitions of specific record structures for reading !**** the JSON file via jsonread of mmhttp public declarations expl=public record id,modTitle,modType,modFeatures: text modFileL,modDataL: list of text modFile,modData: text modRating:integer end-record chap=public record id,title,directory: text models: list of expl end-record examples: list of chap end-declarations writeln("\n****Reading JSON into record structures via jsonread****") setparam("ioctrl",true) jsonread(FNAME,examples) setparam("ioctrl",false) if getparam("iostatus")=0 then forall(dir in examples) do writeln(dir.directory, " - ", dir.title) forall(j in dir.models) writeln(" "*10, j.modTitle,": ", if(j.modFile<>"", j.modFile, text(j.modFileL)) ) end-do writeln("First example: ", jsontext(examples(1).models(1))) writeln("Second directory: ", jsontext(examples(2), HTTP_SKIP_EMPTYCOL+HTTP_INDENT)) end-if !**** Reading JSON file into generic structures based on union types defined !**** by the package 'json' declarations expldb: jval end-declarations writeln("\n****Reading JSON into union type structures****") if loadjson(FNAME,expldb)=0 and expldb is jarr then forall(i in expldb.jarr.range) with dir=expldb.jarr(i).jobj do writeln(dir("directory")," - ", dir("title")) with modexpl=dir("models").jarr do forall(j in modexpl.range) with ex=modexpl(j).jobj do writeln(" "*10, ex("modTitle"),": ", if(isdefined(ex("modFile")), text(ex("modFile")), text(ex("modFileL")))) end-do end-do end-do writeln("First example: ", jsontext(expldb.jarr(1).jobj("models").jarr(1))) writeln("Models in second directory: ") setparam("jcolmaxw",35) ! Max. column width for table format display displaytable(expldb.jarr(2).jobj("models").jarr, ["id","modTitle","modType"]) end-if end-model | |||||||||||||
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