How to get content as JSON - an overview

This page provides an overview of the different ways of retrieving JSON for JCR-based content in Magnolia as well as listing their respective advantages and disadvantages. 

Magnolia REST delivery API

The delivery API is a Magnolia REST resource introduced with version 2.0 of the Magnolia REST modules. We recommend you use delivery endpoint API v2 to benefit from all the latest features.

This REST resource is highly customizable. You can define multiple endpoint configurations to serve different needs. Each configured endpoint is accessed through a distinct  endpointPath  and provides two sub-resources. The sub-resources can be called with HTTP GET both to read a node (and its subnodes) by a given path and to query nodes.

Example: Find a tour with the word "Japan" in its description. Return only the variant in the German language:

curl -g -G 'http://localhost:8080/magnoliaAuthor/.rest/tours' --data-urlencode "description[like]=%Japan%" \
 -H "Accept-Language: de-DE" -u superuser:superuser

{
  "results": [
    {
      "@name": "Kyoto",
      "@path": "/magnolia-travels/Kyoto",
      "@id": "b475f27e-2929-427b-9517-815118a3b36e",
      "@nodeType": "mgnl:content",
      "body": "<p>Erleben Sie die Sch&ouml;nheit, die Kyoto durchdringt und umgibt. Kyoto ist ber&uuml;hmt f&uuml;r viele Dinge, darunter unz&auml;hlige <a href=\"http://www.japan-guide.com/e/e2058.html\" target=\"_blank\">Tempel</a>, <a href=\"http://www.japan-guide.com/e/e2059.html\" target=\"_blank\">Schreine</a> und andere faszinierende historische Bauwerke.</p>\n<p>Kommen Sie mit uns auf einen Besuch der Stadt der zehntausend Schreine. Wir besuchen To-ji, Ginkaku-ji, Kōzan-ji und ihre bemerkenswerten G&auml;rten, bevor wir einen Abstecher zu den Bergen in der Umgebung der Stadt machen. Sie werden es genie&szlig;en, einen Tag im gr&uuml;nen Miyama und einen Tag mit Wandern in Shizuhara zu verbringen. Sie werden nie wieder wie bisher &uuml;ber Japan denken.</p> ",
      "name": "Kyoto",
      "description": "Die natürliche Seite Japans",
      "destination": [
        "7ec72c48-c33f-418e-b2ff-44cfb4bbb1f2"
      ],
      "location": "Kyoto, Japan",
      "tourTypes": [
        "d2245867-ecaa-4b4e-8743-e0c939be68b7",
        "415025c6-e4b5-4506-9384-34f428a52104"
      ],
      "author": "Magnolia Travels",
      "duration": "7",
      "image": "jcr:44689d29-5966-4d41-8fd4-2dc7da783528",
      "@nodes": []
    }
  ]
}

class: info.magnolia.rest.delivery.jcr.v2.JcrDeliveryEndpointDefinition
workspace: tours
includeSystemProperties: false

Pros

• Convenient and simple to use JSON structure.
• Supports RESTful URLs.
• Highly configurable via YAML file in a light module or in the JCR configuration workspace.
• Supports multiple endpoint configurations to serve different needs.
• Provides a fine-grained security.
• Supports localization.
• Can resolve referenced nodes from other workspaces,including image renditions, within one request.

Cons

• Read-only. 
• Cannot fetch personalized variants of pages or components.

Magnolia REST nodes and properties endpoints

Magnolia endpoints for nodes and properties - available since version 1.0 of the Magnolia REST modules.

Example: Read JCR content of the /magnolia-travels/Kyoto tour from the Tours content app in the demo.

curl -H "Accept: application/json" http://localhost:8080/magnoliaAuthor/.rest/nodes/v1/tours/magnolia-travels/Kyoto  \
  -u superuser:superuser

For more information and examples, see their API pages:

• Nodes endpoint API
• Properties endpoint API

Pros

• Complete API to create, read, update and delete (CRUD) JCR data.
• Supports RESTful URLs.
• Provides a fine-grained security.

Cons

• Can only fetch content from one workspace per single request.
• Rigid and verbose JSON structure.
• Poor localization support.
• Cannot fetch personalized variants of pages or components (see personalization).

Custom Java endpoints

Create a custom REST endpoint depending on your needs.

The following example snippet is taken from the  CameraCollectionEndpoint .

    @Path("/allCameras")
    @GET
    @Produces(MediaType.APPLICATION_JSON)
    @ApiOperation(value = "Get all cameras.", notes = "Returns json for the list of all a camera objects.")
    @ApiResponses(value = {
            @ApiResponse(code = 200, message = STATUS_MESSAGE_OK, response = List.class),
            @ApiResponse(code = 401, message = STATUS_MESSAGE_UNAUTHORIZED),
            @ApiResponse(code = 404, message = STATUS_MESSAGE_NODE_NOT_FOUND),
            @ApiResponse(code = 500, message = STATUS_MESSAGE_ERROR_OCCURRED)
    })
    public List<Camera> getAllCameras() {
        List<Camera> result = null;
        try {
            result = cameraCollectionPojoService.getAllCameras();
        } catch (RepositoryException e) {
            log.warn("Could not compute the list of all cameras.");
        }
        return result;
    }

To explore the complete example, clone the camera-collection module from git and read Camera Collection module on Magnolia Community Wiki.

Also read How to create a custom Java-based REST endpoint.

Pros

• Highly configurable.
• Provides a fine-grained security.
• When using com.wordnik.swagger.annotations.* , endpoints are automatically exposed in the Swagger tool for testing (see Swagger API explorer).
  
• Delivery of personalized variants of pages or components is possible (see personalization).
  

Cons

• Requires Java skills.
• Must be deployed in a Maven module.

FreeMarker template

You can implement a custom JSON provider in a FreeMarker template script. Use templating functions such as cmsfn , damfn and others to read data from JCR and render JSON in your preferred manner.

Approaches: A pure JSON provider or an HTML-mixed one

Pure JSON

You can write a FreeMarker template in a way that its response is pure JSON. This is what we consider as a template script based or FreeMarker based JSON provider. To go for this approach, do the following:

1. Create a page template. A dialog is not required.
2. Write FreeMarker code that renders JSON.
3. Create a page with this new template. 
4. Request the new page to get JSON in the response.

Step 2 can go from very simple to very complex. 

Mixed with HTML

You also can write a template that renders HTML and assigns JSON to JavaScript variables:

<!DOCTYPE html>
<html xml:lang="${cmsfn.language()}" lang="${cmsfn.language()}">
  <head>
    [@cms.page /]
    <meta charset="utf-8" />
    [#assign pageNode = cmsfn.contentByPath("/magnolia-travels/Kyoto", "tours")]
    <script>
    var someJson = '${jsonfn.from(pageNode).add("@path", "name", "description").wrapForI18n().inline().print()}';
    </script>
  </head>
  <body class="mixed ${cmsfn.language()}">

    <div class="container ">
      <h1>Find a better title later on ;-)</h1>
    </div>
  </body>
</html>

Assembling JSON manually

Here is a simple example of how you can assemble JSON structure in FreeMarker:

[#assign pageNode = cmsfn.contentByPath("/magnolia-travels/Kyoto", "tours")]
{
"path" : "${pageNode.@path}",
"name" : "${pageNode.name}",
"description" : "${pageNode.description}"
}

The sample project camera-collection provides a more sophisticated FreeMarker-based JSON provider, see simple-json-provider.ftl and json-provider-utils.ftl on git.

Assembling JSON with jsonfn

jsonfn templating functions generate JSON from JCR nodes in any workspace. jsonfn helps you assemble JSON within a FreeMaker template script and provides powerful methods to generate JSON in a flexible way. It can resolve references to nodes of other workspaces and it also provides links to renditions of assets in one request. See resolving referenced nodes and renditions.

To achieve the same JSON as in Assembling JSON manually above, write the following code:

[#assign pageNode = cmsfn.contentByPath("/magnolia-travels/Kyoto", "tours")]
${jsonfn.from(pageNode).add("@path", "name", "description").print()}

Setting the proper content type of the response

If your FreeMarker template acts as a pure JSON provider, you may want to set the content type of the response to application/json . You cannot set the content type directly in the template definition. Instead you have to define a new renderer and reference this renderer in the template definition with the renderType property.

However, having the "proper" content type may not be required. In many use cases it is sufficient to use the FreeMarker renderType that responds with text/html .

Renderer configuration

!inherit:freemarker
contentType: application/json

Template definition

title: jsonprovider0815
templateScript: /ftl-json-provider/templates/pages/jsonprovider0815.ftl
renderType: json
#renderType: freemarker
visible: true

Turning a template-based JSON provider into a RESTful API with virtualURIMapping

You can create a template that accepts request parameters to specify the JSON content to be returned. In the example below, you can specify the workspace and the path of the node.

[#assign path = ctx.path!"undefined" /]
[#assign workspace = ctx.workspace!"tours" /]

[#assign response = '{ "error" : "Missing path parameter." }' /]

[#if path!="undefined"]
  [#assign contentNode = cmsfn.contentByPath(path, workspace)]
  [#assign response = jsonfn.from(contentNode).add("@path", "name", "description").wrapForI18n().print() /]
[/#if]

${response}

Pros

• Highly configurable.
  • Fully customizable when assembling JSON manually.
  • Decent customizable when using jsonfn.
• No Java required.
• Localization support.
• Delivery of personalized variants of pages or components is possible (see personalization).

Cons

• Security cannot be set per workspace and path, but only generally for the page that acts as the JSON provider.
• Methods beyond GET (such as PUT, POST or DELETE ) cannot be implemented using just FreeMarker.

Getting localized JSON

If your content is localized, you can also get localized JSON output. See enabling multi-language content about how to create localized content.

Depending on the technique applied to get JSON, you may have to force getting the localized version or you will get a JSON version of the default locale.

With the delivery API

With the delivery endpoint API v2, you can configure multiple endpoints with full content localization support.

To request a specific single language variant, do one of the following:

• Set the Accept-Language header. For example:  Accept-Language: de-DE
• Set the langquery parameter. For example: lang=de-DE

If both are set, the lang parameter takes priority. If neither is set, the decision is delegated to the I18nContentSupport interface.

To return all language variants:

• Set the lang query parameter to all: lang=all

You can use both the Accept-Language header and the lang query parameter for both sub-resources Read node and Query nodes.

See Requesting localized content with the delivery endpoint.

With default endpoints for nodes and properties

Localized properties must be read as <property-name>_<LOCALE>. For example, description_de for the property named description. The default endpoints do not take the client's locale into account. When JSON is generated, the nodes are not wrapped with  I18nNodeWrapper . It is impossible to tell which language is default.

With custom JAVA endpoints

In a custom endpoint, you typically fetch  Node  objects (Java objects representing JCR nodes) that you transform into JSON later on. Make sure you wrap the node with  I18nNodeWrapper  before producing JSON. The following shows a method wrapping a node to make sure it is localized (copied from  TemplatingFunctions , which is the underlying Java class of cmsfn):

public Node wrapForI18n(Node content) {
    return content != null?new I18nNodeWrapper(content):null;
}

In a FreeMarker template

In a FreeMarker template, it is the wrapForI18n method that makes sure the values are returned in their localized form.

With manually assembled JSON

Use cmsfn.wrapForI18n to get a localized version of a content node:

With jsonfn

When using jsonfn, add the wrapForI18n method before calling the print method.

The same-origin policy problem

According to the same-origin policy:

(...) a web browser permits scripts contained in a first web page to access data in a second web page, but only if both web pages have the same origin.

Wikipedia

Therefore, if your application resides within a domain that is different from the domain that hosts your data, the web browser will actively prevent accessing content stored under the host domain.

An elegant solution to solve the same-origin policy without changing Apache configuration is the Magnolia Add HTTP Headers filter. This fiter is available out-of-the-box; you only need to configure it.