What can possible go wrong with this:
public void Main()
{
var input = new StringReader(Document);
var deserializer = new Deserializer(namingConvention: new CamelCaseNamingConvention());
var p = deserializer.Deserialize<Person>(input);
Console.WriteLine(p.Name);
}
public class Person
{
public string Name {get;set;}
}
private const string Document = #"Name: Peter";
A serialization exception is thrown:
Property 'Name' not found on type 'YamlDotNet.Samples.DeserializeObjectGraph+Person'
The same happens if I first serialize a Person object using the Serializer.
While the online sample for deserialization works just fine - this trivial code does not. What am I missing? It must be a stupid little detail. (But it happened before with other data structures I tried.)
As it seems, the problem is with the namingConvention parameter. If I don't set it to an instance of CamelCaseNamingConvention all is fine.
Unfortunately the "canonical" example (https://dotnetfiddle.net/HD2JXM) uses it and thus suggests it is important.
For any reason the CamelCaseNamingConvention converts the fields to lowercase in the class (ie. 'Name' to 'name'). As the string is 'Name' and not 'name' the deserialization fails. The example uses lower-case therefore it works....
I had the same problem....
Related
I'm having some trouble getting typing to work with the JsonSlurper in Groovy. I'm fairly new to Groovy, and even newer to adding strong types to it - bear with me.
Right now I've created a trait which defines the general shape of my JSON object, and I'm trying to cast the results of parseText to it.
import groovy.json.JsonSlurper
trait Person {
String firstname
String lastname
}
def person = (Person)(new JsonSlurper().parseText('{"firstname": "Lando", "lastname": "Calrissian"}'))
println person.lastname
This throws
Exception in thread "main" org.codehaus.groovy.runtime.typehandling.GroovyCastException: Cannot cast object '{firstname=Lando, lastname=Calrissian}' with class 'org.apache.groovy.json.internal.LazyMap' to class 'Person' due to: groovy.lang.GroovyRuntimeException: Could not find matching constructor for: Person(org.apache.groovy.json.internal.LazyMap)
...
I can see why my code doesn't make sense, I'm not trying to change the type of the data (casting), I'm just trying to let my IDE know that this is what's inside of my object.
Is it possible to at least add code completion to my JSON objects? I'd love to get runtime type checking, as well, but it's not necessary.
you could try to use delegate
this allows to wrap class around map
import groovy.json.JsonSlurper
class Person {
#Delegate Map delegate
String getFirstname(){ delegate.get('firstname') }
String getLastname(){ delegate.get('lastname') }
}
def person = new Person(delegate:new JsonSlurper().parseText('{"firstname": "Lando", "lastname": "Calrissian"}'))
println person.lastname
or for example use Gson for parsing:
#Grab(group='com.google.code.gson', module='gson', version='2.8.5')
import com.google.gson.Gson
class Person {
String firstname
String lastname
}
def person = new Gson().fromJson('{"firstname": "Lando", "lastname": "Calrissian"}', Person.class)
assert person instanceof Person
println person.lastname
This actually is a cast and Groovy will try to turn your Map into said object.
From the docs:
The coercion operator (as) is a variant of casting. Coercion converts object from one type to another without them being compatible for assignment.
The way this works for a POJO is to construct a new object using the Map-c'tor. This will either unroll into calling setters or works directly with static compilation.
Be aware, that using maps with excess keys will lead to errors. So I'd only use this for toy projects. Use a proper JSON-mapper like e.g. Jackson instead.
So the solution here is to not use a trait (which is basically a interface) but a regular class.
I want to use ServiceStack JsonSerializer.
I am setting IncludeTypeInfo property true before I serialize my object.And my serialized string contains all type informations like "__type":".Interfacesb,....
When I want to deserialize string that time my interface property null even though I have type information in my serialized string.Is there any other configuration need when deserializing object.
I use two methods
JsonSerializer.SerializeToString and JsonSerializer.DeSerializeFromString
Example:
JsConfig.IncludeTypeInfo = true;
Public Class MyObject
{
Public string a{get;set;}
Public interface b{get;Set;}
}
First, the version 4.* is the continued developed version. 3.9 is not actively maintained by anyone.
Test on servicestack.text 4.50
Secondly i don't think this this property was made to de-serialize it back practical objects.
i did the same in 4.50 and it just doesn't deserialize:
Alternative solutions
Here you can read what to if you want the types from the json: https://stackoverflow.com/a/21603948/1275832.
When you have the type:
I use the following code as an alternative solution (note its an extension method) as a solution for run-time dynamic types (v4.50):
public static object FromJson(this string json, Type deserializeType)
{
return typeof(JsonSerializer).GetMethod("DeserializeFromString", BindingFlags.Static)
.MakeGenericMethod(deserializeType)
.Invoke(null, new[] { json });
}
and usage as: var object = (MyInterface)jsonString.FromJson(Type.GetType(AssemblyQualifiedNameString));
In jcouchdb I used to extend BaseDocument and then, in a transparent manner, mix Annotations and not declared fields.
Example:
import org.jcouchdb.document.BaseDocument;
public class SiteDocument extends BaseDocument {
private String site;
#org.svenson.JSONProperty(value = "site", ignoreIfNull = true)
public String getSite() {
return site;
}
public void setSite(String name) {
site = name;
}
}
and then use it:
// Create a SiteDocument
SiteDocument site2 = new SiteDocument();
site2.setProperty("site", "http://www.starckoverflow.com/index.html");
// Set value using setSite
site2.setSite("www.stackoverflow.com");
// and using setProperty
site2.setProperty("description", "Questions & Answers");
db.createOrUpdateDocument(site2);
Where I use both a document field (site) that is defined via annotation and a property field (description) not defined, both get serialized when I save document.
This is convenient for me since I can work with semi-structured documents.
When I try to do the same with Ektorp I have documents using annotations and Documents using HashMap BUT I couldn't find an easy way of getting the mix of both (I've tried using my own serializers but this seems to much work for something that I get for free in jcouchdb). Also tried to annotate a HashMap field but then is serialized as an object and I get the fields automatically saved BUT inside an object with the name of the HashMap field.
Is it possible to do (easily/for free) using Ektorp?
It is definitely possible. You have two options:
Base your class on org.ektorp.support.OpenCouchDbDocument
Annotate the you class with #JsonAnySetter and #JsonAnyGetter. Red more here: http://wiki.fasterxml.com/JacksonFeatureAnyGetter
This is how I used to utilize inheritance in Entity Framework (POCO):
ctx.Animals // base class instances (all instances)
ctx.Animals.OfType<Cat> // inherited class Cat's instances only
ctx.Animals.OfType<Dog> // inherited class Dog's instances only
This is the only similar way I found in MongoDb (MongoDb reference):
var query = Query.EQ("_t", "Cat");
var cursor = collection.FindAs<Animal>(query);
Note in the latter case I have to deal with discriminator ("_t") and hardcode my class name, that is not quite convenient and looks awful. If I miss the query I got an exception on enumeration attempt. Have I missed something? My suggestion was the document Db which stores objects 'as is' should handle inheritance easily.
Assuming your discriminators are functioning (_t is stored correctly for each document) then I think this is what you are looking for.
var results = collection.AsQueryable<Animal>().OfType<Cat>
Returns only those documents that are of type 'Cat'.
Well, a document db does in fact store objects "as is" - i.e. without the notion of objects belonging to some particular class. That's why you need _t when you want the deserializer to know which subclass to instantiate.
In your case, I suggest you come up with a discriminator for each subclass, instead of relying on the class name. This way, you can rename classes etc. without worrying about a hardcoded string somewhere.
You could do something like this:
public abstract class SomeBaseClass
{
public const string FirstSubClass = "first";
public const string SecondSubClass = "second";
}
[BsonDiscriminator(SomeBaseClass.FirstSubClass)]
public class FirstSubClass { ... }
and then
var entireCollection = db.GetCollection<FirstSubClass>("coll");
var subs = entireCollection.Find(Query.Eq("_t", SomeBaseClass.FirstSubClass));
From your link:
The one case where you must call RegisterClassMap yourself (even without arguments) is when you are using a polymorphic class hierarchy: in this case you must register all the known subclasses to guarantee that the discriminators get registered.
Register class maps for your base class and each one of your derived classes:
BsonClassMap.RegisterClassMap<Animal>();
BsonClassMap.RegisterClassMap<Cat>();
BsonClassMap.RegisterClassMap<Dog>();
Make sure that your collection is of type of your base class:
collection = db.GetCollection<Animal>("Animals");
Find using your query. The conversion to the corresponding child class is done automatically:
var query = Query.EQ("_t", "Cat");
var cursor = collection.Find(query);
If the only concern is hardcoding class name, you can do something like this:
collection = db.GetCollection<Animal>("Animals");
var query = Query.EQ("_t", typeof(Cat).Name);
var cursor = collection.Find(query);
Take a look on the documentation
http://docs.mongodb.org/ecosystem/tutorial/serialize-documents-with-the-csharp-driver/#scalar-and-hierarchical-discriminators
The main reason you might choose to use hierarchical discriminators is because it makes it possibly to query for all instances of any class in the hierarchy. For example, to read all the Cat documents we can write:
var query = Query.EQ("_t", "Cat");
var cursor = collection.FindAs<Animal>(query);
foreach (var cat in cursor) {
// process cat
}
I am currently using CSS to change everything I write to upperCase when I create an entry, but that is not enough. When I save things, the text shown in the text fields is upper case, but the real value that Grails stores stays in lower case.
I am assuming I'd need to change something in the controller or anything.
Maybe transforming the $fieldValue CSS could work??
Any ideas would help!
Thnks!
You could just write setters for your domain object?
class Domain {
String aField
void setAField( String s ){
aField = s?.toUpperCase()
}
}
I think you are asking how to change values on your domain objects to uppercase. If this is not the case please clarify the question.
You have a bunch of options. I would recommend
1) In a service method, before you save, using String.toUpperCase() to modify the appropriate values on the domain object.
or
2) You can use the underlying Hibernate interceptors by defining a beforeInsert method on your domain object, and doing the toUpperCase there. (see 5.5.1 of the grails documentation)
or
3) You could do this client side. However, if it is a "business requirement" that the values are stored as upper, then I recommend doing the translation server side. It is easier to wrap tests around that code....
Using annotations is cleanest approach
import org.grails.databinding.BindingFormat
class Person {
#BindingFormat('UPPERCASE')
String someUpperCaseString
#BindingFormat('LOWERCASE')
String someLowerCaseString
}
Here is link for it: Grails doc for data binding
You can use Groovy metaprogramming to change the setter for all domain class String-typed properties without actually writing a custom setter for each property.
To do this, add something like the following to the init closure of Bootstrap.groovy
def init = { servletContext ->
for (dc in grailsApplication.domainClasses) {
dc.class.metaClass.setProperty = { String name, value ->
def metaProperty = delegate.class.metaClass.getMetaProperty(name)
if (metaProperty) {
// change the property value to uppercase if it's a String property
if (value && metaProperty.type == String) {
value = value.toUpperCase()
}
metaProperty.setProperty(delegate, value)
} else {
throw new MissingPropertyException(name, delegate.class)
}
}
}
}