Core API - 3.2

This section describes key classes which are essential while using Slice. They constitute a base for a day-to-day development.

ModelProvider

The com.cognifide.slice.api.provider.ModelProvider interface is a basic interface of Slice. It allows you to fetch an injectable object(s) mapped from specified resource or path. It's very similar to Guice com.google.inject.Injector because it is used for fetching objects of different classes. However it's more Sling-related because it always takes resource (or path) as a parameter, so that an object of the specified class can be mapped. You should use ModelProvider whenever there is a need for injecting a model mapped from a given resource (path).

ModelProvider allows you to fetch either a single object of a specified class or a list of objects of a specified class. During execution of methods of this interface, the execution context is modified, meaning that the specified path is put on the top of the execution stack. This allows other objects to inject the specified resource (or path) and use it as a current resource. Read more about execution stack here.

Below table describes methods of the interface.

Method	Description
`<T> T get(final Class<T> type, final String path);`	Creates an object of class type and maps it from a resource from under specified path
`<T> T get(final Class<T> type, final Resource resource);`	Creates an object of class type and maps it from the resource
`Object get(final String className, final String path) throws ClassNotFoundException;`	Creates an object of a class defined by specified className String and maps it from a resource from under specified path
`<T> List<T> getList(final Class<T> type, final Iterator<String> paths);`	Creates a list of objects of class type and maps them accordingly from resources from under paths defined by paths interator.
`<T> List<T> getList(final Class<T> type, final String[] paths);`	Creates a list of objects of class type and maps them accordingly from resources from under paths defined by paths array.

ModelProvider can be injected to your models, so that you can read a model from an arbitrary resource or path, e.g.:

import com.cognifide.app.util.Currency;

import com.cognifide.slice.api.provider.ModelProvider;
import com.cognifide.slice.mapper.annotation.JcrProperty;
import com.cognifide.slice.mapper.annotation.SliceResource;
import com.google.inject.Inject;

@SliceResource
public class OrderModel {

    private final static String CONFIGURATION_PATH = "/content/app/configuration/jcr:content/currency";

    private final ModelProvider modelProvider;

    @JcrProperty
    private int value;

    @Inject
    public OrderModel(ModelProvider modelProvider) {
        this.modelProvider = modelProvider;
    }

    public int getValue() {
        Currency currency = modelProvider.get(Currency.class, CONFIGURATION_PATH);
        return formatToCurrency(value, currency);
    }
    ...
}

ChildrenProvider

The com.cognifide.slice.api.provider.ChildrenProvider interface allows you to get a list of child resources (paths) from under specified path.

Below table describes methods of the interface.

Method	Description
`List<String> getChildren(final String path);`	Returns paths to child resources of a resource from under specified path. If a resource under specified path doesn't exist, empty list is returned. The method is not recursive - it reads only direct children.
`List<Resource> getChildResources(final String path);`	Returns child resources of a resource from under specified path. If a resource under specified path doesn't exist, empty list is returned. The method is not recursive - it reads only direct children

Link, LinkBuilder

Thanks to com.cognifide.slice.api.link.Link and com.cognifide.slice.api.link.LinkBuilder interfaces you can easily manipulate on Sling links, e.g. setting selectors, extension, query string, path, etc.

They should be used whenever there is a need to modify an existing link (e.g. adding or removing some selectors) or create a new one and then manipulate it.

New link can only be created using LinkBuilder. LinkBuilder can be obtained from LinkBuilderFactory which is injectable. An example usage of it is shown in the listings below:

import com.cognifide.slice.api.link.Link;
import com.cognifide.slice.api.link.LinkBuilder;
import com.cognifide.slice.api.link.LinkBuilderFactory;
import com.cognifide.slice.api.qualifier.CurrentResourcePath;
import com.google.inject.Inject;

public class EventModel {
    private final LinkBuilderFactory linkBuilderFactory;
    private final String currentPath;
    
    @Inject
    public EventModel(LinkBuilderFactory linkBuilderFactory, @CurrentResourcePath String currentPath) {
        this.linkBuilderFactory = linkBuilderFactory;
        this.currentPath = currentPath;
    }

    public Link getPrintLink() {
        LinkBuilder linkBuilder = linkBuilderFactory.getLinkBuilder();
        linkBuilder.setPath(currentPath);
        linkBuilder.setSelectorString("print");
        linkBuilder.setExtension("pdf");
        return linkBuilder.toLink();
    }
    ...
}

import com.cognifide.slice.api.link.Link;
import com.cognifide.slice.api.link.LinkBuilder;
import com.cognifide.slice.api.link.LinkBuilderFactory;
import com.cognifide.slice.cq.qualifier.RequestedLink;
import com.google.inject.Inject;

public class EventModel {
    private final LinkBuilderFactory linkBuilderFactory;
    private final Link requestedLink;

    @Inject
    public EventModel(LinkBuilderFactory linkBuilderFactory, @RequestedLink Link requestedLink) {
        this.linkBuilderFactory = linkBuilderFactory;
        this.requestedLink = requestedLink;
    }
    public String getPrintLink() {
        LinkBuilder linkBuilder = linkBuilderFactory.getLinkBuilder(requestedLink);
        linkBuilder.addSelector("print").setExtension("pdf"); // it will retain query string and suffix
        return linkBuilder.toString();
    }
    ...
}

Best practice

There is no need to create Link objects if you're not going to modify any aspects of link. If you only want to display a link you can build it simply using String concatenation.

ClassToKeyMapper

The com.cognifide.slice.api.provider.ClassToKeyMapper interface allows you to obtain a com.google.inject.Key associated with a class specified by a String value. Thanks to this you can inject objects of classes specified by Strings rather than classes. In general, this interface is not widely used.