Without having spent a lot of time on this subject, I'm curious what might be the most straightforward way to allow my existing code to serialize to json in addition to xml. The existing code uses a xmlwriter to perform some sophisticated serialization for a specific purpose, so ultimately I'd like to be able to pass a jsonserializer in place of the xml one and have it produce json instead of xml.
Do any of the json libs handle something like this?
No, there's no direct drop-in replacement. The APIs for existing JSON serializers is much different. They need to have the entire model in memory and serialize it in one step. For example with JSON.NET you would use:
string json = JsonConvert.SerializeObject(product);
The correct way to achieve what you are looking for is to abstract the actual serialization of the object behind an interface:
public interface IMySerializer
{
void Serialize(MyObject instance, Stream stream);
}
Now you could have multiple implementations of this interface such as MySerializerXml, MySerializerJson, MySerializerCsv, ...
Now the code that depends on the serialization would simply work with an IMySerializer. So when you need to handle a new format all you have to do is drop-in an implementation of this interface.
There is no direct replacement for an XmlWriter. If you want to support both XML and JSON, I would suggest serialising via data-contracts, i.e. use attributes on your data objects to indicate the desired serialised format. Take a look at DataContractJsonSerializer for JSON and DataCOntractSerializer for XML.
Your model objects would look something like this:
[DataContract(Name = "Customer", Namespace = "http://www.contoso.com")]
class Person
{
[DataMember()]
public string FirstName;
[DataMember]
public string LastName;
[DataMember()]
public int ID;
}
Related
I searched, but couldn't find a satisfying answer. I know there are serializers like: DataContractJsonSerializer, JavaScriptSerializer to do that. But these required a weird requirement of specifying 'KnownType', which is not possible in my scenario as object i am serializing belongs to generic library, and actual implementations of interface could come from client.
Any suggestions ?
ServiceStack has a JSON serializer which doesn't require specifying the known types:
var json = JsonSerializer.SerializeToString(myObj);
Or using extension methods you can call ToJson on any object:
var json = myObj.ToJson();
Json.Net has a method SerializeObject. This would do the job for you.
It's signature is:
public static string SerializeObject(object value);
usage:
using Newtonsoft.Json;
...
string jsonData = JsonConvert.SerializeObject(obj);
I just learned how to serialize and deserialize objects to XML in C#.
Now I would like to add this functionality to my application, I have a class for the object. Should I create a class that contains the serialize and deserialize methods? Or, should there be an Interface or something?
How is this normally done?
You would be best keeping your object and serialisation mechanism seperate DataContractSerializers are good for this in .Net. They allow data annotations (as mentioned in the comment above) to be specified on properties and automate the actual serialisation for you.
There is an interface (ISerializable), but you also have generic classes that exist and can do the job for you. In that cas you'd have to place the right Attributes for the propertyies you want get serialized.
take a look here if you want the documentation about this.
.Net has some built-in serializers (BinaryFormatter and XmlSerializer
if you go with the interface you'll have to write your own methods
Provided your classes are simple enough for serialization you can do this:
using (FileStream stream = File.Create(filename)){
XmlSerializer serializer = new XmlSerializer(typeof(MyRootClassHere));
serializer .Serialize(stream, yourRootInstance);
}
You may need to take a look at XmlElement, XmlAttribute, XmlIgnore, XmlText attributes to control the output better:
[XmlIgnore]
public bool IgnoredBool{ get; set; }
[XmlAttribute("NewXmlName")]
public string RenamedProperty{ get; set; }
This should get you going for the most part.
I have an object that I want to create an XML from, what's the best way to do this in ASP.NET 3.5?
I want to save it to a file also (web application).
I don't want to serialize the object, since I will have some custom element names and attributes and values that will be modified during XML creation.
It is a bit hard to answer without knowing how "custom" is "custom", but LINQ-to-XML is a good bet since you have .NET 3.5:
// using variables here to show how the names etc can be decided at runtime
string elName = "Fred";
DateTime when = DateTime.Today;
int id = 123;
string idName = "id";
var el = new XElement(elName, new XAttribute(idName, id), when);
el.Save("out.xml");
Giving the xml:
<Fred id=\"123\">2010-03-01T00:00:00+00:00</Fred>
If the file is huge, then XmlWriter may be more efficient, but the code is harder.
If you don't want to serialize you could use XmlWriter.
You should use System.Xml.Linq, which is the easiest way to manipulate XML by far.
Since you will have dynamic document, I'd suggest System.Xml.Linq.XDocument to generate it. Then you just use XDocument.Save to save it.
You can use the System.Xml namespace.
using System.Xml;
XmlDocument document = new XmlDocument();
XmlNode rootNode = document.CreateElement("root");
document.AppendChild(rootNode);
// Create other nodes related to your object and append them to the root node.
document.Save("path/to/your/xml/file.xml");
I used XmlDocument before I learned about serialization.
Why not implement the ISerializable interface? Then you have full control over the serialization process yourself...
See examples here:
http://msdn.microsoft.com/en-us/library/system.runtime.serialization.iserializable.aspx
and here:
http://msdn.microsoft.com/en-us/library/ms182342(VS.80).aspx
You can combine this with XmlSerializer, if you have a complex object you need to serialize, an you don't want to write all of the serialization yourself.
If it's just part of the object (i.e. some properties) you want to do special serialization of, you can make these objects that implements ISerializable, and change the value to whatever you need it to be, during serialization.
Consider creating a helper class that uses XML serialization. That decouples the XML formatting from the main class's design, and generally speaking is in keeping with the idea of adding functionality to classes through composition. (In fact, it's often a good idea to do it this way even if the helper class doesn't use XML serialization.) It also lets you format the XML declaratively without getting having to write a lot of procedural code.
How to do this: design the helper class so that it exposes public properties in a fashion that XmlSerializer likes, and gets those values from an instance of your class that's passed in to a private constructor. Add a static XmlSerializer property, and a public static method that uses the XmlSerializer to write the data to a file or a stream or whatever. Something like:
[XmlRoot("MyClass")]
public class MyClassXmlWriter
{
private static XmlSerializer Serializer = new XmlSerializer(typeof MyClassXmlWriter);
public static void Write(MyClass source, Stream st)
{
Serializer.Serialize(new MyClassXmlWriter(source), st);
}
private MyClass Source;
private MyClassXmlWriter(MyClass source)
{
Source = source;
}
[XmlElement("SomeElement")]
public string SomeProperty { get { return Source.SomeProperty; } }
}
Using this is as simple as:
using (FileStream fs = new FileStream(filename))
{
MyClassXmlWriter.Write(myObject, fs);
}
Note that if you ever need to implement deserialization, you just give its properties public getters and then implement a static Read method that deserializes into a new MyClassXmlWriter object and then creates and populates a MyClass object from its properties. (You'd probably change the name of the class, though.)
What's the simplest way to get XmlSerializer to also serialize private and "public const" properties of a class or struct? Right not all it will output for me is things that are only public. Making it private or adding const is causing the values to not be serialized.
XmlSerializer only looks at public fields and properties. If you need more control, you can implement IXmlSerializable and serialize whatever you would like. Of course, serializing a constant doesn't make much sense since you can't deserialize to a constant.
Even though it's not possible to serialize private properties, you can serialize properties with an internal setter, like this one :
public string Foo { get; internal set; }
To do that, you need to pre-generate the serialization assembly with sgen.exe, and declare this assembly as friend :
[assembly:InternalsVisibleTo("MyAssembly.XmlSerializers")]
Check out DataContractSerializer, introduced in .NET 3.0. It also uses XML format, and in many ways, it is better than XmlSerializer, including dealing with private data.
See http://www.danrigsby.com/blog/index.php/2008/03/07/xmlserializer-vs-datacontractserializer-serialization-in-wcf/ for a full comparison.
If you only have .NET 2.0, there's the BinarySerializer that can deal with private data, but of course it's a binary format.
It doesn't make sense to consider const members, as they aren't per-instance; but if you just mean non-public instance members: consider DataContractSerializer (.NET 3.0) - this is similar to XmlSerializer, but can serialize non-public properties (although it is "opt in").
See here for more.
One other solution the use of Newtonsoft.Json:
var json = Newtonsoft.Json.JsonConvert.SerializeObject(new { root = result });
var xml = (XmlDocument)Newtonsoft.Json.JsonConvert.DeserializeXmlNode(json);
Sure, this one has unfortunately detour via json.
Here's my solution to putting immutable values in a property that will serialize to XML:
[XmlElement]
public string format { get { return "Acme Order Detail XML v3.4.5"; } set { } }
Create a class (call it FormElement). That class should have some properties like the metadata they have with data elements (name, sequence number, value—which is just a string, etc).
This class has as attributes of type Validation Application Block Validation classes.
I want to serialize it to xml and deserialize it. Verify that all properties of the class including the validation application block attributes survive serialization.
some suggestion?
The .NET framework has this built in, using C# you would do it like this:
// This code serializes a class instance to an XML file:
XmlSerializer xs = new XmlSerializer(typeof(objectToSerialize));
using (TextWriter writer = new StreamWriter(xmlFileName))
{
xs.Serialize(writer, InstanceOfObjectToSerialize);
}
And this snippet is an example of how to deserialize an XML file back to a class instance:
// this code creates a class instance from the file we just made:
objectToSerialize newObject;
XmlSerializer xs = new XmlSerializer(typeof(objectToSerialize));
using (TextReader reader = new StreamReader(xmlFileName))
{
newObject = (ObjectToSerialize) xs.Deserialize(reader);
}
You must mark your class with the [Serializable] attribute for these to work. If you want to make your XML output a little more pretty, you can use [XmlElement] and [XmlAttribute] attributes on your class properties to have them serialize into your schema of choice.
By saying serialize, do you mean use the official Serialization mechanism, or achieve a similar effect?
If your objects are beans, you could use reflection to write a general service that takes a class and writes down its class name and properties. It can similarly read materials from the XML and generate the object (which is what Apache Digester essentially does).
What Jonathon Holland said.
However, you also asked about validation. If you use the code Jonathan posted, all of your properties will serialize and de-serialize correctly. But if you really want to check it, there is a property you can set with your XmlSerializer object for a *.xsd schema to validate against. You can create the schema easily enough from your class by using the xsd.exe command-line tool that is included with Visual Studio.
Also, it sounds like you might want to control whether certain properties of your class are serialized as attributes or elements. Jonathon touched on that, but I want to show an example:
[Serializable]
public class FormElement
{
[XmlAttribute]
public string Name {get; set;};
[XmlAttribute]
public int Sequence {get; set;};
[XmlAttribute]
public string Value {get; set;};
[XmlElement]
public Validation OnValidate{get; set;}
[NonSerialized]
public string UnimportantProperty {get; set;};
}
Finally, the type for every property that you want to serialize must also be serializable, and complicated types must be serialized as XmlElements. Otherwise you won't be able to do it.
XStream is a pretty good java library for doing just that.