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  • Is there a GUI that I can use to create XML documents based on my schema?

    - by David Conlisk
    Hi all, I want to create a simple graphical user interface to allow non-technical users to create an XML file without having to manually edit the XML source. Ideally I'd like a drag and drop interface, but failing that, anything really. The contents of the XML file are similar to an encoded flow chart of a binary tree, so maybe something like Visio, with a save as xml option? Here's a quick sample of the XML output that is required: <?xml version="1.0" encoding="utf-8"?> <steps> <step id="1" type="prompt"> <prompt> Welcome. </prompt> <next>1.1</next> </step> <step id="1.1" type="question"> <prompt> Do you have what you need? </prompt> <yes>1.2</yes> <no>1.1.1</no> </step> ... </steps> Are there any existing tools out there that you can recommend for this purpose? Ideally open-source or with a free personal license, but I'm interested in hearing about all options. Thanks, David

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  • What is the performance penalty of XML data type in SQL Server when compared to NVARCHAR(MAX)?

    - by Piotr Owsiak
    I have a DB that is going to keep log entries. One of the columns in the log table contains serialized (to XML) objects and a guy on my team proposed to go with XML data type rather than NVARCHAR(MAX). This table will have logs kept "forever" (archiving some very old entries may be considered in the future). I'm a little worried about the CPU overhead, but I'm even more worried that DB can grow faster (FoxyBOA from the referenced question got 70% bigger DB when using XML). I have read this question http://stackoverflow.com/questions/514827/microsoft-sql-server-2005-2008-xml-vs-text-varchar-data-type and it gave me some ideas but I am particulairly interrested in clarification on whether the DB size increases or decreases. Can you please share your insight/experiences in that matter. BTW. I don't currently have any need to depend on XML features within SQL Server (there's nearly zero advantage to me in the specific case). Ocasionally log entries will be extracted, but I prefer to handle the XML using .NET (either by writing a small client or using a function defined in a .NET assembly).

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  • How to parse large xml files on google app engine?

    - by Alon Carmel
    Hey, I have fairly large xml file 1mb in size that i host on s3. I need to parse that xml file into my app engine datastore entirely. I have written a simple DOM parser that works fine locally but online it reaches the 30sec error and stops. I tried lowering the xml parsing by downloading the xml file into a BLOB at first before the parser then parse the xml file from blob. problem is that blobs are limited to 1mb. so it fails. I have multiple inserts to the datastore which cause it to fail on 30 sec. i saw somewhere that they recommend using the Mapper class and save some exception where the process stopped but as i am a python n00b i cant figure out how to implement it on a DOM parser or an SAX one (please provide an example?) on how to use it. i'm pretty much doing a bad thing right now and i parse the xml using php outside the app engine and push the data via HTTP post to the app engine using a proprietary API which works fine but is stupid and makes me maintain two codes. can you please help me out?

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  • XSLT question, how to transform xml when I have xslt file stored, but object in mem?

    - by JL
    I have a function that takes 2 parameters : 1 = XML file, 2 = XSLT file, then performs a transformation and returns the resulting HTML. Here is the function: /// <summary> /// Will apply an XSLT style to any XML file and return the rendered HTML. /// </summary> /// <param name="xmlFileName"> /// The file name of the XML document. /// </param> /// <param name="xslFileName"> /// The file name of the XSL document. /// </param> /// <returns> /// The rendered HTML. /// </returns> public string TransformXml(string xmlFileName, string xslFileName) { var xtr = new XmlTextReader(xmlFileName) { WhitespaceHandling = WhitespaceHandling.None }; var xd = new XmlDocument(); xd.Load(xtr); var xslt = new System.Xml.Xsl.XslCompiledTransform(); xslt.Load(xslFileName); var stm = new MemoryStream(); xslt.Transform(xd, null, stm); stm.Position = 1; var sr = new StreamReader(stm); xtr.Close(); return sr.ReadToEnd(); } I want to change the function not to accept a file name, but rather a strongly typed object de-serialized (now in the form of a variable). Is this possible? So keep the xslt coming from a file, but the xml input should be a the serialized xml of the object I pass, and I want to do this without file system IO.

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  • Add namespace to XmlTextWriter using C#

    - by xml
    Hi, I have an serializeable class that his root is serizlized to XmlRootAttribute with namespace. I want to add additional namespace to this root elemt, how can i do it? adding XmlAttribute failed to compile. The code: [System.Xml.Serialization.XmlRootAttribute("Root", Namespace = "http://www.w3.org/2003/05/soap-envelope", IsNullable = false)] public class MyClass { [System.Xml.Serialization.XmlElement("...")] public ClassA A; [System.Xml.Serialization.XmlElement("..")] public ClassB b; } After the serialization i'm getting something like that: <Root xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns="http://www.w3.org/2003/05/soap-envelope"> <ClassA/> <ClassB/> </Envelope> I want to add to the rood additioanl namespace, e.g. i want the xml to be: <Root xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema" **xmlns:tns="anotherXml"** xmlns="http://www.w3.org/2003/05/soap-envelope"> <ClassA/> <ClassB/> </Envelope> Any idea?

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  • Is there an application that can help someone create an XML document based on the Relax NG schema?

    - by meowsqueak
    I've spent a bit of time creating a Relax NG schema for use within our team to validate XML documents we use for exchanging information. The schema is not complicated, but it is reasonably large. I am wondering if there exists a tool that can read in such a Relax NG schema and assist a user in creating a corresponding instance document, using the schema as a template. Perhaps an application with a GUI that creates fields and drop-down selections for each part of the document? For example, the tool might create an outline XML document and prompt the user to select multiples of certain elements, fill in each field, perhaps with permitted values read directly from the schema. It might also show the user via visual feedback when their document is 'complete', or highlight validation problems as they come up. I could anticipate writing a custom GUI tool to create such an XML document, but I'd really like changes to the schema to be automatically reflected by the GUI - and I really wonder if this hasn't already been done. I know some editors can automatically validate an XML document against a schema as it's being written, but I would really like to get my users one step away from the XML so they don't have to worry about the details of the XML syntax.

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  • Why is IE8 on XP not properly reading from XML using JQuery?

    - by dking
    Given this XML in data.xml <?xml version="1.0" encoding="utf-8"?> <data> <bar>100</bar> </data> I want to display the content from the "bar" element using the following code in test.html <html> <head> <script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.3.2/jquery.min.js"></script> </head> <body> <script type="text/javascript"> $.get('data.xml', function(xml) { var foo = $(xml).find('bar').text(); document.write("<span>foo: [" + foo + "]</span>"); }); </script> </body> </html> The output in webkit based browsers: foo: [100] The output in IE8 on XP: foo: [] Why do webkit browsers read the element's content correctly while IE8 interprets it as an empty string?

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  • What's so bad about building XML with string concatenation?

    - by wsanville
    In the thread What’s your favorite “programmer ignorance” pet peeve?, the following answer appears, with a large amount of upvotes: Programmers who build XML using string concatenation. My question is, why is building XML via string concatenation (such as a StringBuilder in C#) bad? I've done this several times in the past, as it's sometimes the quickest way for me to get from point A to point B when to comes to the data structures/objects I'm working with. So far, I have come up with a few reasons why this isn't the greatest approach, but is there something I'm overlooking? Why should this be avoided? Probably the biggest reason I can think of is you need to escape your strings manually, and most programmers will forget this. It will work great for them when they test it, but then "randomly" their apps will fail when someone throws an & symbol in their input somewhere. Ok, I'll buy this, but it's really easy to prevent the problem (SecurityElement.Escape to name one). When I do this, I usually omit the XML declaration (i.e. <?xml version="1.0"?>). Is this harmful? Performance penalties? If you stick with proper string concatenation (i.e. StringBuilder), is this anything to be concerned about? Presumably, a class like XmlWriter will also need to do a bit of string manipulation... There are more elegant ways of generating XML, such as using XmlSerializer to automatically serialize/deserialize your classes. Ok sure, I agree. C# has a ton of useful classes for this, but sometimes I don't want to make a class for something really quick, like writing out a log file or something. Is this just me being lazy? If I am doing something "real" this is my preferred approach for dealing w/ XML.

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  • Ruby - Nokogiri - Parsing XML from memory and putting all same name node values into an array.

    - by r3nrut
    I have an XML I'm trying to parse from memory and get the status of each of my heart beat tests using Nokogiri. Here is the solution I have... xml = <a:HBeat> <a:ElapsedTime>3 ms</a:ElapsedTime> <a:Name>Service 1</a:Name> <a:Status>true</a:Status> </a:HBeat> <a:HBeat> <a:ElapsedTime>4 ms</a:ElapsedTime> <a:Name>Service 2</a:Name> <a:Status>true</a:Status> </a:HBeat> <a:HBeat> I have tried using both css and xpath to pull back the value for each Status and put it into an array. Code is below: doc = Nokogiri::XML.parse(xml) #service_state = doc.css("a:HBeat, a:Status", 'a' => 'http://schemas.datacontract.org/2004/07/OpenAPI.Entity').map {|node| node.children.text} service_state = doc.xpath("//*[@a:Status]", 'a' => 'http://schemas.datacontract.org/2004/07/OpenAPI.Entity').map(&:text) Both will return service_state = []. Any thoughts or recommendations? Also, consider that I have almost identical xml for another test and I used the following snippet of code which does exactly what I wanted but for some reason isn't working with the xml that contains namespaces. service_state = doc.css("HBeat Status").map(&:text) Thanks!

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  • Change XML node element value in PHP and save file.

    - by Hannes
    <testimonials> <testimonial id="4c050652f0c3e"> <nimi>John</nimi> <email>[email protected]</email> <text>Some text</text> <active>1</active> </testimonial> <testimonial id="4c05085e1cd4f"> <name>ats</name> <email>[email protected]</email> <text>Great site!</text> <active>0</akctive> </testimonial> </testimonials> I have this XML strcuture and i need to find a testimonial with specific id and change its value and save file. I have a PHP script deleting specific testimonial according its ID: <?php $xmlFile = file_get_contents('test.xml'); $xml = new SimpleXMLElement($xmlFile); $kust_id = $_GET["id"]; foreach($xml->testimonial as $story) { if($story['id'] == $kust_id) { $dom=dom_import_simplexml($story); $dom->parentNode->removeChild($dom); $xml->asXML('test.xml'); header("Location: newfile.php"); } } ?>

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  • Scala XML API: Why allow NodeSeq as attribute values?

    - by Synesso
    It seems attribute values are of type Seq[Node]. scala> <a b="1"/>.attribute("b") res11: Option[Seq[scala.xml.Node]] = Some(1) This means you can assign XML as an attribute value. scala> <a b={<z><x/></z>}/>.attribute("b") res16: Option[Seq[scala.xml.Node]] = Some(<z><x></x></z>) scala> <a b={<z><x/></z>}/>.attribute("b").map(_ \ "x") res17: Option[scala.xml.NodeSeq] = Some(<x></x>) scala> new xml.PrettyPrinter(120, 2).format(<a b={<z><x/></z>}/>) res19: String = <a b="<z><x></x></z>"></a> This seems funky to me. I've never seen XML as attribute values in the real world. Why is it allowed? Why is an attribute value simply not of type String?

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  • Parsing an XML string containing "&#x20;" (which must be preserved)

    - by Zoodor
    I have code that is passed a string containing XML. This XML may contain one or more instances of &#x20; (an entity reference for the blank space character). I have a requirement that these references should not be resolved (i.e. they should not be replaced with an actual space character). Is there any way for me to achieve this? Basically, given a string containing the XML: <pattern value="[A-Z0-9&#x20;]" /> I do not want it to be converted to: <pattern value="[A-Z0-9 ]" /> (What I am actually trying to achieve is to simply take an XML string and write it to a "pretty-printed" file. This is having the side-effect of resolving occurrences of &#x20; in the string to a single space character, which need to be preserved. The reason for this requirement is that the written XML document must conform to an externally-defined specification.) I have tried creating a sub-class of XmlTextReader to read from the XML string and overriding the ResolveEntity() method, but this isn't called. I have also tried assigning a custom XmlResolver.

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  • jquery XML, i need .html() not .text() but not working?

    - by Xtian
    I need var long to be exported as html and not text. I know I have .text() but when I use .html() it will not work. Also if I take the .text() out when declaring the variable and it will not work in IE? The reason for this is, in the XML certain words will have html tags like or and I need those to be recognized. I thought I solved it when I took out .text() but then i looked at IE and I got nothing. $(document).ready(function(){ $.ajax({ type: "GET", url: "xml/sites.xml", dataType: "xml", success: function(xml) { $(xml).find('site').each(function(){ var id = $(this).attr('id'); var title = $(this).find('title').text(); var class =$(this).find('class').text(); $('<div class="'+class+'" id="link_'+id+'"></div>').html('<h2>'+title+'</h2>').appendTo('#page-wrap'); $(this).find('desc').each(function(){ var long = $(this).find('long'); var url = $(this).find('url').text(); $('<div class="long"></div>').html(long).appendTo('#link_'+id); $('<a href="http://'+url+'"</a>').html(url).appendTo('#link_'+id); }); }); } }); });// JavaScript Document

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  • Ignoring a xml Tag in the middle of the file in Regex (with non capturing group ?)

    - by schmirrwurst
    I have an xml with an embeded tag, and I would like to capture everthing but the FType Tags... in python regex. <xml> <EType> <E></E> <F></F> <FType><E1></E1><E2></E2></FType> <FType><E1></E1><E2></E2></FType> <FType><E1></E1><E2></E2></FType> <G></G> </EType> </xml> I tried : (?P<xml>.*(?=<FType>.*<FType>).*) But it give me everything ;-( I Expect : <xml> <EType> <E></E> <F></F> <G></G> </EType> </xml>

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  • It is possible to hibernate an LXC container?

    - by Jo-Erlend Schinstad
    I know about lxc-freeze and lxc-unfreeze, but as I understand it, these simply pauses the container, similar to sending SIGSTOP and SIGCONT to a process. If I reboot the host, then the containers will cease to exist, right? I would really like a way to save state to persistent storage so that I could resume them at some later time, even the host is rebooted or something like that. I can achieve exactly what I want using VirtualBox by using the "Save machine state" mechanism, but if I could do it with LXC, it would be completely awesome.

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  • Workflow versioning

    - by Nitra
    I believe I have a fundamental misunderstanding when it comes to workflow engines which I would appreciate if you could help me sort out. I'm not sure if my misunderstanding is specific to the workflow engine I'm using, or if it's a general misunderstanding. I happen to use Windows Workflow Foundation (WWF). TLDR-version WWF allows you to implement business processes in long-running workflows (think months or even years). When started, the workflows can't be changed. But what business process can't change at any time? And if a business process changes, wouldn't you want your software to reflect this change for already started 'instances' of the business process? What am I missing? Background In WWF you define a workflow by combining a set of activites. There are different types of activities - some of them are for flow control, such as the IfElseActivity and the WhileActivty while others allows you to perform actual tasks, such as the CodeActivity wich allows you to run .NET code and the InvokeWebServiceActivity which allows you to call web services. The activites are combined to a workflow using a visual designer. You pretty much drag-and-drop activities from a toolbox to a designer area and connect the activites to each other. The workflow and activities have input paramters, output parameters and variables. We have a single workflow which sometimes runs in a matter of a few days, but it may run for 5-6 months. WWF takes care of persisting the workflow state (what activity are we currently executing, what are the variable values and so on). So far I think WWF makes sense. Some people will prefer to implement a software representation of a business process using a visual designer over writing all of it in code. So what's the issue then? What I don't really get is the following: WWF is designed to take care of long-running workflows. But at the same time, WWF has no built-in functionality which allows you to modify the running workflows. So if you model a business process using a workflow and run that for 6 months, you better hope that the business process does not change. Because if it do, you'll have to have multiple versions of the workflow executing at the same time. This seems like a fundamental design mistake to me, but at the same time it seems more likely that I've misunderstood something. For us, this has had some real-world effects: We release new versions every month, but some workflows may run for a year. This means that we have several versions of the workflow running in parallell, in other words several versions of the business logics. This is the same as having many differnt versions of your code running in production in the same system at the same time, which becomes a bit hard to understand for users. (depending on on whether they clicked a 'Start' button 9 or 10 months ago, the software will behave differently) Our workflow refers to different types of entities and since WWF now has persisted and serialized these we can't really refactor the entities since then existing workflows can't be resumed (deserialization will fail We've received some suggestions on how to handle this When we create a new version of the workflow, cancel all running workflows and create new ones. But in our workflows there's a lot of manual work involved and if we start from scratch a lot of people has to re-do their work. Track what has been done in the workflow and when you create a new one skip activites which have already been executed. I feel that this alternative may work for simple workflows, but it becomes hairy to automatically figure out what activities to skip if there's major refactoring done to a workflow. When we create a new version of the workflow, upgrade old versions using the new WWF 4.5 functionality for upgrading workflows. But then we would have to skip using the visual designer and write code to inject activities in the right places in the workflow. According to MSDN, this upgrade functionality is only intended for minor bug fixes and not larger changes. What am I missing?

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  • Strategy for backwards compatibility of persistent storage

    - by Baqueta
    In my experience, trying to ensure that new versions of an application retain compatibility with data storage from previous versions can often be a painful process. What I currently do is to save a version number for each 'unit' of data (be it a file, database row/table, or whatever) and ensure that the version number gets updated each time the data changes in some way. I also create methods to convert from v1 to v2, v2 to v3, and so on. That way, if I'm at v7 and I encounter a v3 file, I can do v3-v4-v5-v6-v7. So far this approach seems to be working out well, but I haven't had to make use of it extensively yet so there may be unforseen problems. I'm also concerned that if the objects I'm loading change significantly, I'll either have to keep around old versions of the classes or face updating all my conversion methods to handle the new class definition. Is my approach sound? Are there other/better approaches I could be using? Are there any design patterns applicable to this problem?

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  • Caching factory design

    - by max
    I have a factory class XFactory that creates objects of class X. Instances of X are very large, so the main purpose of the factory is to cache them, as transparently to the client code as possible. Objects of class X are immutable, so the following code seems reasonable: # module xfactory.py import x class XFactory: _registry = {} def get_x(self, arg1, arg2, use_cache = True): if use_cache: hash_id = hash((arg1, arg2)) if hash_id in _registry: return _registry[hash_id] obj = x.X(arg1, arg2) _registry[hash_id] = obj return obj # module x.py class X: # ... Is it a good pattern? (I know it's not the actual Factory Pattern.) Is there anything I should change? Now, I find that sometimes I want to cache X objects to disk. I'll use pickle for that purpose, and store as values in the _registry the filenames of the pickled objects instead of references to the objects. Of course, _registry itself would have to be stored persistently (perhaps in a pickle file of its own, in a text file, in a database, or simply by giving pickle files the filenames that contain hash_id). Except now the validity of the cached object depends not only on the parameters passed to get_x(), but also on the version of the code that created these objects. Strictly speaking, even a memory-cached object could become invalid if someone modifies x.py or any of its dependencies, and reloads it while the program is running. So far I ignored this danger since it seems unlikely for my application. But I certainly cannot ignore it when my objects are cached to persistent storage. What can I do? I suppose I could make the hash_id more robust by calculating hash of a tuple that contains arguments arg1 and arg2, as well as the filename and last modified date for x.py and every module and data file that it (recursively) depends on. To help delete cache files that won't ever be useful again, I'd add to the _registry the unhashed representation of the modified dates for each record. But even this solution isn't 100% safe since theoretically someone might load a module dynamically, and I wouldn't know about it from statically analyzing the source code. If I go all out and assume every file in the project is a dependency, the mechanism will still break if some module grabs data from an external website, etc.). In addition, the frequency of changes in x.py and its dependencies is quite high, leading to heavy cache invalidation. Thus, I figured I might as well give up some safety, and only invalidate the cache only when there is an obvious mismatch. This means that class X would have a class-level cache validation identifier that should be changed whenever the developer believes a change happened that should invalidate the cache. (With multiple developers, a separate invalidation identifier is required for each.) This identifier is hashed along with arg1 and arg2 and becomes part of the hash keys stored in _registry. Since developers may forget to update the validation identifier or not realize that they invalidated existing cache, it would seem better to add another validation mechanism: class X can have a method that returns all the known "traits" of X. For instance, if X is a table, I might add the names of all the columns. The hash calculation will include the traits as well. I can write this code, but I am afraid that I'm missing something important; and I'm also wondering if perhaps there's a framework or package that can do all of this stuff already. Ideally, I'd like to combine in-memory and disk-based caching.

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  • Alternatives for saving data with jquery

    - by Phil Vallone
    I am not sure if this question is considered too broad, but I would like to reach out to my fellow programmers to see what alternatives are out there for saving data using jquery. I have a content management system that generates an set of HTML pages called an IETM (Interactive Electronic Technical Manual). The HTML pages are written in HTML and uses jquery. The ITEM is meant to be light weight, portable and run on most modern browsers. I am looking for a way to save data. I have considered cookies and sqlite. Are there any other alternatives for saving data using jquery?

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  • Best Practices for serializing/persisting String Object Dictionary entities

    - by Mark Heath
    I'm noticing a trend towards using a dictionary of string to object (or sometimes string to string), instead of strongly typed objects. For example, the new Katana project makes heavy use of IDictionary<string,object>. This approach avoids the need to continually update your entity classes/DTOs and the database tables that persist them with new properties. It also avoids the need to create new derived entity types to support new types of entity, since the Dictionary is flexible enough to store any arbitrary properties. Here's a contrived example: class StorageDevice { public int Id { get; set; } public string Name { get; set; } } class NetworkShare : StorageDevice { public string Path { get; set; } public string LoginName { get; set; } public string Password { get; set; } } class CloudStorage : StorageDevice { public string ServerUri { get; set } public string ContainerName { get; set; } public int PortNumber { get; set; } public Guid ApiKey { get; set; } } versus: class StorageDevice { public IDictionary<string, object> Properties { get; set; } } Basically I'm on the lookout for any talks, books or articles on this approach, so I can pick up on any best practices / difficulties to avoid. Here's my main questions: Does this approach have a name? (only thing I've heard used so far is "self-describing objects") What are the best practices for persisting these dictionaries into a relational database? Especially the challenges of deserializing them successfully with strongly typed languages like C#. Does it change anything if some of the objects in the dictionary are themselves lists of strongly typed entities? Should a second dictionary be used if you want to temporarily store objects that are not to be persisted/serialized across a network, or should you use some kind of namespacing on the keys to indicate this?

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  • Patterns for a tree of persistent data with multiple storage options?

    - by Robin Winslow
    I have a real-world problem which I'll try to abstract into an illustrative example. So imagine I have data objects in a tree, where parent objects can access children, and children can access parents: // Interfaces interface IParent<TChild> { List<TChild> Children; } interface IChild<TParent> { TParent Parent; } // Classes class Top : IParent<Middle> {} class Middle : IParent<Bottom>, IChild<Top> {} class Bottom : IChild<Middle> {} // Usage var top = new Top(); var middles = top.Children; // List<Middle> foreach (var middle in middles) { var bottoms = middle.Children; // List<Bottom> foreach (var bottom in bottoms) { var middle = bottom.Parent; // Access the parent var top = middle.Parent; // Access the grandparent } } All three data objects have properties that are persisted in two data stores (e.g. a database and a web service), and they need to reflect and synchronise with the stores. Some objects only request from the web service, some only write to it. Data Mapper My favourite pattern for data access is Data Mapper, because it completely separates the data objects themselves from the communication with the data store: class TopMapper { public Top FetchById(int id) { var top = new Top(DataStore.TopDataById(id)); top.Children = MiddleMapper.FetchForTop(Top); return Top; } } class MiddleMapper { public Middle FetchById(int id) { var middle = new Middle(DataStore.MiddleDataById(id)); middle.Parent = TopMapper.FetchForMiddle(middle); middle.Children = BottomMapper.FetchForMiddle(bottom); return middle; } } This way I can have one mapper per data store, and build the object from the mapper I want, and then save it back using the mapper I want. There is a circular reference here, but I guess that's not a problem because most languages can just store memory references to the objects, so there won't actually be infinite data. The problem with this is that every time I want to construct a new Top, Middle or Bottom, it needs to build the entire object tree within that object's Parent or Children property, with all the data store requests and memory usage that that entails. And in real life my tree is much bigger than the one represented here, so that's a problem. Requests in the object In this the objects request their Parents and Children themselves: class Middle { private List<Bottom> _children = null; // cache public List<Bottom> Children { get { _children = _children ?? BottomMapper.FetchForMiddle(this); return _children; } set { BottomMapper.UpdateForMiddle(this, value); _children = value; } } } I think this is an example of the repository pattern. Is that correct? This solution seems neat - the data only gets requested from the data store when you need it, and thereafter it's stored in the object if you want to request it again, avoiding a further request. However, I have two different data sources. There's a database, but there's also a web service, and I need to be able to create an object from the web service and save it back to the database and then request it again from the database and update the web service. This also makes me uneasy because the data objects themselves are no longer ignorant of the data source. We've introduced a new dependency, not to mention a circular dependency, making it harder to test. And the objects now mask their communication with the database. Other solutions Are there any other solutions which could take care of the multiple stores problem but also mean that I don't need to build / request all the data every time?

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  • Naming interfaces for persistent values

    - by orip
    I have 2 distinct types of persistent values that I'm having trouble naming well. They're defined with the following Java-esque structure, borrowing Guava's Optional for the example and using generic names to avoid anchoring: interface Foo<T> { T get(); void set(T value); } interface Bar<T> { Optional<T> get(); void set(T value); } With Foo, if the value hasn't been set explicitly then there's some default value available or pre-set. With Bar, if the value hasn't been set explicitly then there's a distinct "no value" state. I'm trying to optimize the names for their call sites. For example, someone using Foo may not care whether there's a default value involved, only that they're guaranteed to always have a value. How would you go about naming these interfaces?

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  • Moving from a traditional in memory Java session to persistent storage sessions

    - by Benju
    We have decided to take the plunge and move from using a typical java session provider in Tomcat/Jetty/etc to persisting everything to a central datastore. We are looking at using MongoDB for this. A few options come to mind... http://wiki.eclipse.org/Jetty/Tutorial/MongoDB_Session_Clustering This is nice because it will "auto-magically" persist our session to a Mongo installation. I am concerned however that we will not have fine grained control of what is happening. https://github.com/mattinsler/com.lowereast.guiceymongo/ GuiceMongo is interesting as it integrates with Guice. Perhaps we could persist everything via this ORM. Has anybody had to deal with this kind of move? It seems that moving from in memory to persistent session storage has a lot of gotchas.

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