I've read many tutorials showing how to use json with grails using templates, but what the utility of doing so? why would I want to show plain json page? ? what the utility of json templates ? like : (from grails official documentation)
model {
Person person
}
json {
name person.name
age person.age
}
since they're not allowing ANY styling ?
Thank you
The reason for this (as pointed out in the comments by dmahapatro) is for use with a REST API.
It makes no sense in the context of displaying this directly to an end-user. However, in the context of a REST API used by another system or by AJAX calls from within a HTML/GSP page it makes a lot of sense.
Since a REST API can be based on HTTP requests made to send/receive JSON data, having the configuration on how a domain class is represented in JSON as a part of the domain class itself helps keep things centralized and tidy. Instead of JSON being manually created or configuration for representing your domain classes in JSON kept somewhere else.
Related
I am looking for either guidance or a good example where I can map data coming from rest services to JSON "type" object which can then be used in a number of different react components.
The JSON Object will be used to map data from a few different rest services, which essentially hold very similar data which makes it better to use one object and then to bind the data to the respective React Components.
I am fairly new to React.JS and I have googled around to find a data mapper to JSON from Rest Service example.
Can anyone help?
You typically don't have to do too much, at least on the front end side. As long as the REST endpoint can return JSON responses you'll be fine. Just make sure you set the appropriate Content-Type headers in the request. Note that setting the header doesn't guarantee a JSON response, the server has to be able to send it in that format.
If you're creating the REST service yourself, you have many options. If you're using node, you can simply return a javascript object. If you're using some other language like Java, C#, etc., they come with libraries that can serialize objects into JSON for you. I use JSON.net when working with C#. In these cases, because the data will be returned as a string, you'll just need to JSON.parse() it upon receiving it and then set it to the appropriate React component's state.
I am developing a small web api in PHP and try to make it as restful as possible.
Currently i'm working on some kind of a "homepage" which should be a json represented overview of what the client can do without having to read a documentation. I discovered the json-home format (see draft-nottingham-json-home-02) what seems to be quite useful in my case. But since it's not spread that much it's hard to find examples. What I don't understand is what the "href-vars" - attribute is (see 4.1. Resolving Templated Links).
For example I have a route /api/documents/{id} what gives me the json representation for one single document. Obviously this is a template-link resource in json-home format, but what would be my href-vars : { id: } ?
HREF-VARS is used to specify a parameter for URL Templating.
The URI is firstly a unique identifier for the parameter. The URL could contain documentation regarding the type of the parameter.
An automated system is going to feed the application[Play with Scala] with JSON's and the contract of the integration is that there would be no validation required on JSON's since it will be always deemed right. But for testing purposes when we seed the data more often than not we are not able to send the correct JSONs. We would like to validate the JSON's we receive based on a set of grammars. Is there a library that already does this. Or is there a better way to do this?
Example: Grammar for valid Json :
"header"->[String, mandatory],
"footer"->[String],
"someArray"->Array[String, mandatory],
"someArrayObject"->Array[
{
{"key1"->Int, mandatory},
{"key2"->String}
},
mandatory
]
and passing,
{
"header":"headerContent",
"footer":"footerContent",
"someArray":["str1", "str2"],
"someArrayObject"->[
{"key1":4, "key2":"someStringValue"},
{"key1":5, "key2":"someOtherStringValue"}
]
} // would pass
{
"header":"headerContent",
"footer":"footerContent",
"someArray":["str1", "str2"]
} // would notpass since someArrayObject though declared mandatory is not provided in the sample json
I think play-json will satisfy you play-json
In play-json you don't create a validator as it is, but a json transformer which is a validator in itself. The author of the framework wrote a series of blog-posts to show how to work with it: json-transformers
* Haven't noticed you use play) Play has play-json included by default.
You don't have to roll out your own DSLs. This is why we have schemas. Just like using XML schemas to validate your XML docs, you can define a JSON schema to validate your JSON objects. I had a similar requirement when building a RESTful web service using Play. I solved it by using the JSON Schema Validator library.
I have used the JSON Schema draft v3. The library supports draft v3 and draft v4. You can validate your schemas against possible JSON inputs using a web application that uses the same library. The web app is hosted here.
Also there are pretty nice examples that use the draft v4. You can check them out from here.
In Play 2, I have composed an action that takes the schema resource file name as input. This keeps away a lot of JSON validation code from the controller action itself.
#JsonValidate("user-register.json")
public static Result create() {
...
}
This way, all JSON Validation code stays in one place. Pretty neat :)
I'm developing a RESTful interface which is used to provide JSON data for a JavaScript application.
On the server side I use Grails 1.3.7 and use GORM Domain Objects for persistence. I implemented a custom JSON Marshaller to support marshalling the nested domain objects
Here are sample domain objects:
class SampleDomain {
static mapping = { nest2 cascade: 'all' }
String someString
SampleDomainNested nest2
}
and
class SampleDomainNested {
String someField
}
The SampleDomain resource is published under the URL /rs/sample/ so /rs/sample/1 points to the SampleDomain object with ID 1
When I render the resource using my custom json marshaller (GET on /rs/sample/1), I get the following data:
{
"someString" : "somevalue1",
"nest2" : {
"someField" : "someothervalue"
}
}
which is exactly what I want.
Now comes the problem: I try to send the same data to the resource /rs/sample/1 via PUT.
To bind the json data to the Domain Object, the controller handling the request calls def domain = SampleDomain.get(id) and domain.properties = data where data is the unmarshalled object.
The binding for the "someString" field is working just fine, but the nested object is not populated using the nested data so I get an error that the property "nest2" is null, which is not allowed.
I already tried implementing a custom PropertyEditorSupport as well as a StructuredPropertyEditor and register the editor for the class.
Strangely, the editor only gets called when I supply non-nested values. So when I send the following to the server via PUT (which doesn't make any sense ;) )
{
"someString" : "somevalue1",
"nest2" : "test"
}
at least the property editor gets called.
I looked at the code of the GrailsDataBinder. I found out that setting properties of an association seems to work by specifying the path of the association instead of providing a map, so the following works as well:
{
"someString" : "somevalue1",
"nest2.somefield" : "someothervalue"
}
but this doesn't help me since I don't want to implement a custom JavaScript to JSON object serializer.
Is it possible to use Grails data binding using nested maps? Or do I really heave to implement that by hand for each domain class?
Thanks a lot,
Martin
Since this question got upvoted several times I would like to share what I did in the end:
Since I had some more requirements to be implemented like security etc. I implemented a service layer which hides the domain objects from the controllers. I introduced a "dynamic DTO layer" which translates Domain Objects to Groovy Maps which can be serialized easily using the standard serializers and which implements the updates manually. All the semi-automatic/meta-programming/command pattern/... based solutions I tried to implement failed at some point, mostly resulting in strange GORM errors or a lot of configuration code (and a lot of frustration). The update and serialization methods for the DTOs are fairly straightforward and could be implemented very quickly. It does not introduce a lot of duplicate code as well since you have to specify how your domain objects are serialized anyway if you don't want to publish your internal domain object structure. Maybe it's not the most elegant solution but it was the only solution which really worked for me. It also allows me to implement batch updates since the update logic is not connected to the http requests any more.
However I must say that I don't think that grails is the appropriate tech stack best suited for this kind of application, since it makes your application very heavy-weight and inflexbile. My experience is that once you start doing things which are not supported by the framework by default, it starts getting messy. Furthermore, I don't like the fact that the "repository" layer in grails essentially only exists as a part of the domain objects which introduced a lot of problems and resulted in several "proxy services" emulating a repository layer. If you start building an application using a json rest interface, I would suggest to either go for a very light-weight technology like node.js or, if you want to/have to stick to a java based stack, use standard spring framework + spring mvc + spring data with a nice and clean dto layer (this is what I've migrated to and it works like a charm). You don't have to write a lot of boilerplate code and you are completely in control of what's actually happening. Furthermore you get strong typing which increases developer productivity as well as maintainability and which legitimates the additional LOCs. And of course strong typing means strong tooling!
I started writing a blog entry describing the architecture I came up with (with a sample project of course), however I don't have a lot of time right now to finish it. When it's done I'm going to link to it here for reference.
Hope this can serve as inspiration for people experiencing similar problems.
Cheers!
It requires you to provide teh class name:
{ class:"SampleDomain", someString: "abc",
nest2: { class: "SampleDomainNested", someField:"def" }
}
I know, it requires different input that the output it produces.
As I mentioned in the comment earlier, you might be better off using the gson library.
Not sure why you wrote your own json marshaller, with xstream around.
See http://x-stream.github.io/json-tutorial.html
We have been very happy with xstream for our back end (grails based) services and this way you can render marshall in xml or json, or override the default marshalling for a specific object if you like.
Jettison seems to produce a more compact less human readable JSON and you can run into some library collision stuff, but the default internal json stream renderer is decent.
If you are going to publish the service to the public, you will want to take the time to return appropriate HTTP protocol responses for errors etc... ($.02)
I am trying to create a REST web service using JAX-RS. In that, I have PUT method or POST method which consumes the json as mediatype in the REST web service. Can I know how to call these methods from the client side. How do we pass that json as input from client side to those PUT and POST method and how would we consume the json format in the PUT or POST method from server side. If we want to consume xml, then we are using JAXBElement. For consuming json, how to do that ?
This may help get you going: http://blog.sertik.net/labels/jersey.html
From my (extremely rusty) recollection, you sort of treat the #PUT methods the same way you treat #POST methods. So as shown in that blog entry, try using the #FormParam annotations. Also, read over the Jersey API to see if anything looks useful.
The main difference between them (PUT/POST) is in the meaning; PUT typically creates a new resource at the uri, whereas POST can 'append to' it (there are also a few other meanings to what exactly POST does).
PS almost forgot to mention, cURL is so.... nice.
Hey there is a built in support for JSON in JAX-RS.For this you just need to write the POJO class with JAXB annotations. JAX-RS has built in MessageBodyReaders and MessageBodyWriters to support.If you want to POST i.e., sending the Custom Data you need to write your own MessageBodyReaders/Writers and register them with the Client.