angular-spring-data-rest

An AngularJS module with an additional interceptor which eases the work with a Spring Data REST backend.

See how it works

If you want to see the module in action, then check out the sample application which runs with Spring Boot and is super easy to setup: angular-spring-data-rest-sample

Table of contents

• Quick start
• Overview
• The SpringDataRestAdapter
  • Usage of SpringDataRestAdapter
  • Usage of _resources method
    • The _resources method parameters and return type
    • _resources usage example
    • Exchange the underlying Angular $resource function
  • Usage of _embeddedItems property
    • _embeddedItems usage example
  • How to automatically fetch links
    • Fetch multiple or all links
    • Exchange the underlying fetch function
    • The fetch method parameters
  • How to use SpringDataRestAdapter with promises
  • Configuration of the SpringDataRestAdapter
• The SpringDataRestInterceptor
• Dependencies
• Release notes
• Acknowledgements
• License

Quick start

To use the SpringDataRestAdapter Angular module with bower execute the following command to install the package:

bower install angular-spring-data-rest

or with npm:

npm install angular-spring-data-rest

Overview

Spring Data REST integrates Spring HATEOAS by default. This simplifies the creation of REST presentations which are generated with the HATEOAS principle.

Therefore the Spring Data REST responses have resources and embedded resources like in the following JSON response example:

{
    "_links": {
        "self": {
            "href": "http://localhost:8080/categories{?page,size,sort}",
            "templated": true
        }
    },
    "_embedded": {
        "categories": [
            {
                "name": "Test category 1",
                "_links": {
                    "self": {
                        "href": "http://localhost:8080/categories/1"
                    },
                    "parentCategory": {
                        "href": "http://localhost:8080/categories/1/parentCategory"
                    }
                }
            },
            {
                "name": "Test category 2",
                "_links": {
                    "self": {
                        "href": "http://localhost:8080/categories/2"
                    },
                    "parentCategory": {
                        "href": "http://localhost:8080/categories/2/parentCategory"
                    }
                }
            }
        ]
    },
    "page": {
        "size": 20,
        "totalElements": 2,
        "totalPages": 1,
        "number": 0
    }
}

The above response is the result of calling the endpoint to get all categories(http://localhost:8080/categories). It contains the _links property which holds an object with several named resources(e.g. self). These resources are used to navigate to a related entity(e.g. parentCategory) or to a specific endpoint defined by the backend.

The _embedded property holds an array of the requested items, and each of the items has again a _links property which defines the resources for the specific item. You can find more about how the responses of Spring Data REST look like here.

This Angular module provides two ways of processing a response from the Spring Data REST backend and ease the usage with the resources and embedded items:

1. Using an instance of the SpringDataRestAdapter.
2. Add the SpringDataRestInterceptor to the Angular $httpProvider.interceptors such that all responses are processed.

The SpringDataRestAdapter

The spring-data-rest Angular module provides a provider for the SpringDataRestAdapter object. This object is the core of the module and it processes a given response and adds the following additional properties/methods to it:

1. _resources: this method wraps the Angular $resource function by default (this is exchangeable) and adds an easy way to retrieve the resources defined in the _links property. It is also used to retrieve all available resources of the given object. Read more about this method here.
2. _embeddedItems: this property replaces the _embedded property and sets the named array (categories in the upper example response) with the embedded items as its value. Read more about this property here.

Spring Data REST also generates an index response when you make a GET response to the configured base url of the dispatcher servlet. This response looks like the following example:

{
  "_links" : {
    "users" : {
      "href" : "http://localhost:8080/users{?page,size,sort}",
      "templated" : true
    },
    "categories" : {
      "href" : "http://localhost:8080/categories{?page,size,sort}",
      "templated" : true
    },
    "accounts" : {
      "href" : "http://localhost:8080/accounts{?page,size,sort}",
      "templated" : true
    },
    ...
  }
}

This response shows all configured Spring Data REST repositories and the links to these resources. The SpringDataRestAdapter is also able to handle this response and to provide an easy method to retrieve all the available resources with the _resources method. Please read more about this here.

Another feature is that the SpringDataRestAdapter is able to automatically fetch the links of a resource and adds the response of the link as a property to the main response. Please read more about this here.

Usage of SpringDataRestAdapter

To use the SpringDataRestAdapter object you need to include the angular-spring-data-rest.js file (or the minified version) and add the spring-data-rest module as a dependency in your module declaration:

var myApp = angular.module("myApplication", ["ngResource", "spring-data-rest"]);

Now you are able use the SpringDataRestAdapter object and process a given response and you will get a promise back which resolves with the processes response:

SpringDataRestAdapter.process(response).then(function(processedResponse) {
  ...
});

The response can be a String or a promise from an $http.get() call (or any other promise which resolves the response) like in the following example:

var httpPromise = $http.get('/rest/categories');

SpringDataRestAdapter.process(httpPromise).then(function (processedResponse) {
    $scope.categories = processedResponse._embeddedItems;
});

For simplicity the rest of the examples assume that you already have the response present. Please read on on how to use the _resources method and the _embeddedItems property to ease the handling of resources and embedded items.

Usage of _resources method

The _resources property is added on the same level of the JSON response object where a _links property exists. When for example the following JSON response object is given:

var response = {
    "_links": {
        "self": {
            "href": "http://localhost:8080/categories{?page,size,sort}",
            "templated": true
        }
    },
    "_embedded": {
        ...
    }
    ...
}

Then the SpringDataRestAdapter will add the _resources method to the same level such that you can call it the following way (inside the then function of the promise):

SpringDataRestAdapter.process(response).then(function(processedResponse) {
  processedResponse._resources(linkName, paramDefaults, actions, options);
});

This _resources method is added recursively to all the properties of the JSON response object where a _links property exists.

The _resources method parameters and return type

The _resources method takes the following four parameters:

• linkName: the name of the link's href you want to call with the underlying Angular $resource function. You can also pass in a resource object with parameters in the following way:

SpringDataRestAdapter.process(response).then(function(processedResponse) {
  var resourceObject = {
    "name": "self",
    "parameters": {
        "size": 20,
        "sort": "asc"
    }
  }
  processedResponse._resources(resourceObject, paramDefaults, actions, options);
});

This will call Angular $resource method by default (this is exchangeable) with the href of the self resource and will add the parameters size and sort as query string to the URL. If the resource object parameters and the paramDefaults parameters are set, then these two objects are merged such that the resource object parameters appear first in the new object and the paramDefaults parameters last.

• paramDefaults: the default values for url parameters. Read more here.
• actions: custom action that should extend the default set of the $resource actions. Read more here.
• options: custom settings that should extend the default $resourceProvider behavior Read more here.

You are also able to add URL templates to the passed in linkName parameter. (This just works if you pass a string and not a resource object) The following example explains the usage:

SpringDataRestAdapter.process(response).then(function(processedResponse) {
  var resources = processedResponse._resources("self/:id", {id: "@id"});
  var item = resources.get({id: 1}).then(function(data) {
    item = data;
  };
});

The _resources method returns the Angular resource "class" object with methods for the default set of resource actions. Read more here.

If no parameter is given the _resources method will return all available resources objects of the given object. When for example the following JSON response object is given:

var response = {
    "_links": {
        "self": {
            "href": "http://localhost:8080/categories{?page,size,sort}",
            "templated": true
        },
        "parentCategory": {
            "href": "http://localhost:8080/categories/1/parentCategory"
        }
    },
    "_embedded": {
        ...
    }
    ...
}

Then the following call to the _resources method without any parameter will return an array of all available resource objects.

SpringDataRestAdapter.process(response).then(function(processedResponse) {
  var availableResources = processedResponse._resources();
});

The above call will result in the following return value:

[
    {
        "name":"self",
        "parameters": {
            "page": "",
            "size": "",
            "sort": ""
        }
    },
    {
        "name":"parentCategory"
    }
]

This functionality is useful if you want to first check all available resources before using the _resources method to retrieve the specific resource.

_resources usage example

This example refers to the JSON response in the Overview. If you want to get the parent category of a category you would call the _resources method the following way:

SpringDataRestAdapter.process(response).then(function(processedResponse) {
  var parentCategoryResource = processedResponse._embeddedItems[0]._resources("parentCategory");

  // create a GET request, with the help of the Angular resource class, to the parent category
  // url and log the response to the console
  var parentCategory = parentCategoryResource.get(function() {
    console.log("Parent category name: " + parentCategory.name);
  });
});

Exchange the underlying Angular $resource function

If you want to exchange the underlying call to the Angular $resource method then you are able to do this within the configuration of the SpringDataRestAdapter. By default it will use the Angular $resource function.

The following example shows how to set a custom function:

myApp.config(function (SpringDataRestAdapterProvider) {

    // set the new resource function
    SpringDataRestAdapterProvider.config({
        'resourcesFunction': function (url, paramDefaults, actions, options) {
            // do the call to the backend and return your desired object
        }
    });
});

The description of the parameters you will find here. You can also read more about the configuration of the SpringDataRestAdapter here (and how to use the $http service in the configuration phase)

Usage of _embeddedItems property

The _embeddedItems property is just a convention property created by the SpringDataRestAdapter to easily iterate over the _emebedded items in the response. Like with the _resources method, the SpringDataRestAdapter will recursively create an _embeddedItems property on the same level as a _embedded property exists for all the JSON response properties.

_embeddedItems usage example

This example refers to the JSON response in the Overview. If you want to iterate over all categories in the response you would do it in the following way:

SpringDataRestAdapter.process(response).then(function(processedResponse) {

  // log the name of all categories contained in the response to the console
  angular.forEach(processedResponse._embeddedItems, function (category, key) {
    console.log("Category name: " + category.name);
  });
});

Be aware that the original _embedded property gets deleted after the SpringDataRestAdapter processed the response.

How to automatically fetch links

The SpringDataRestAdapter is able to fetch specified links automatically. This means that if you have the following response:

{
    "_links": {
        "self": {
            "href": "http://localhost:8080/categories{?page,size,sort}",
            "templated": true
        },
        "anotherLink": {
            "href": "http://localhost:8080/anotherLink"
        }
    },
    ...
}

and you want to fetch the data from the anotherLink link then you just need to pass the link name to the SpringDataRestAdapter process function:

SpringDataRestAdapter.process(response, 'anotherLink').then(function(processedResponse) {
  var fetchedObject = processedResponse.anotherLink;
});

Now you are able to get the data from the processed resource by just accessing the property named anotherLink.

The SpringDataRestAdapter by default adds the response of the link to a property in the original response with the same name as the link.

If you want to process the returned response again with the SpringDataRestAdapter then you are able to set the recursive flag when creating it:

SpringDataRestAdapter.process(response, 'anotherLink', true).then(function(processedResponse) {
  ...
});

Now the response of the anotherLink will be processed the same way as the main response was processed. But be aware when setting the recursive flag to true, because when your responses of the links contain the same link name again, then it will end up in a infinite loop.

It will not fetch the self link as this would make no sense because the data is already in the response. The self key is also configurable. Read more here.

As a last configuration option you are able to set the fourth parameter called fetchMultiple of the process method which is used to define if a link is fetched multiple times if the same link is contained in multiple links and you want to resolve each one of them. The drawbackis that it won't cache the responses in any way. So if you enable this then multiple network calls will be made. Here an example:

SpringDataRestAdapter.process(response, 'anotherLink', true, true).then(function(processedResponse) {
  ...
});

⚠️ If you set the fetchMultiple to true you could end up in an infinite loop if you have circular dependencies in your _links.

Fetch multiple or all links

If you want to fetch multiple links then you are able to add an array of strings with the given link names:

SpringDataRestAdapter.process(response, ['anotherLink', 'testLink']).then(function(processedResponse) {
  ...
});

and if you want to fetch all links, then you can use the predefined and also configurable fetchAllLinkNamesKey:

SpringDataRestAdapter.process(response, '_allLinks').then(function(processedResponse) {
  ...
});

Please read more here on how to configure the fetchAllLinkNamesKey.

Exchange the underlying fetch function

If you want to exchange the underlying function to fetch the links then you are able to do this within the configuration of the SpringDataRestAdapter. By default it will use the Angular $http function.

The following example shows how to set a custom function:

myApp.config(function (SpringDataRestAdapterProvider) {

    // set the new resource function
    SpringDataRestAdapterProvider.config({
        'fetchFunction': function (url, key, data, fetchLinkNames, recursive) {
            // fetch the url and add the key to the data object
        }
    });
});

The description of the parameters you will find here. You can also read more about the configuration of the SpringDataRestAdapter here (and how to use the $http service in the configuration phase)

The fetch method parameters

The parameters for the fetch method are the following:

• url: The url of the link from which to fetch the data.
• key: The name of the link which is used to name the property in the data object.
• data: The data object in which the new property is created with the response of the called url.
• fetchLinkNames: The fetch link names to allow to process the fetched response recursiveley
• recursive: True if the fetched response should be processed recursively, false otherwise.

How to use SpringDataRestAdapter with promises

The SpringDataRestAdapter is also able to process promises instead of data objects. The data object which is passed to the specified promise when it is resolved needs to be in the following formats:

{
    data: {
        "_links": {
            "self": {
                "href": "http://localhost:8080/categories{?page,size,sort}",
                "templated": true
            },
            "anotherLink": {
                "href": "http://localhost:8080/anotherLink"
            }
        },
        // the rest of the JSON response
        ...
    }
}

or

{
    "_links": {
        "self": {
            "href": "http://localhost:8080/categories{?page,size,sort}",
            "templated": true
        },
        "anotherLink": {
            "href": "http://localhost:8080/anotherLink"
        }
    },
    // the rest of the JSON response
    ...
}

The data property of the second format of the promise object is the JSON response of the back end. To process such a promise you need to call the SpringDataRestAdapter like in the following example:

SpringDataRestAdapter.process(promise).then(function(processedResponse) {
    // you can now use the processedResponse as any other processed response from the SpringDataRestAdapter
};

You can also right away use the promise support with the Angular $http.get() method like in the following example:

SpringDataRestAdapter.process($http.get('categories')).then(function(processedResponse) {
    $scope.categories = processedResponse._embeddedItems;
};

Configuration of the SpringDataRestAdapter

The SpringDataRestAdapter is designed to be configurable and you are able to configure the following properties:

• linksKey (default: _links): the property name where the resources are stored.
• linksHrefKey (default: href): the property name where the URL is stored in a link object.
• linksSelfLinkName (default: self): the name of the self link in the links object.
• embeddedKey (default: _embedded): the property name where the embedded items are stored.
• embeddedNewKey (default: _embeddedItems): the property name where the array of embedded items are stored.
• embeddedNamedResources (default: false): true if the embedded resources names (can be more than one) should beleft as is, false if they should be removed and be replaced by the value of the first embedded resource
  • Example if set to true:

  {
      ...
      "_embeddedItems": {
          "categories": [...]
      }
      ...
  }

  • Example if set to false:

  {
      ...
      "_embeddedItems": [...]
      ...
  }

• hrefKey (default: href): the property name where the url is stored under each specific link.
• resourcesKey (default: _resources): the property name where the resource method is stored.
• resourcesFunction (default: undefined): the function to use to call the backend. Read more how to do this here
• fetchFunction (default: undefined): the function to use to fetch data from the backend. Read more how to do this here
• fetchAllKey (default: _allLinks): the key to pass to the SpringDataRestAdapter to fetch all available links

You are able to configure the SpringDataRestAdapter provider in a Angular configuration block in the following way:

myApp.config(function (SpringDataRestAdapterProvider) {

    // set the links key to _myLinks
    SpringDataRestAdapterProvider.config({
        'linksKey': '_myLinks'
    });
});

The config method of the SpringDataRestAdapterProvider takes a configuration object and you are able to override each value or completely replace the whole configuration object. The default configuration object looks like this:

{
    "linksKey": "_links",
    "linksHrefKey": "href",
    "linksSelfLinkName": "self",
    "embeddedKey": "_embedded",
    "embeddedNewKey": "_embeddedItems",
    "embeddedNamedResources": false,
    "resourcesKey": "_resources",
    "resourcesFunction": undefined,
    "fetchFunction": undefined,
    "fetchAllKey": "_allLinks"
}

If you want to use the $http service inside the fetch function in the configuration phase then you need to use the Angular injector to get the $http service:

myApp.config(function (SpringDataRestAdapterProvider) {

    // set the new fetch function
    SpringDataRestAdapterProvider.config({
        fetchFunction: function (url, key, data, fetchLinkNames, recursive) {
            var $http = angular.injector(['ng']).get('$http');

            $http.get('/rest/endpoint').then(function (responseData) {
                console.log(responseData);
            })
        }
    });
});

The SpringDataRestInterceptor

If you want to use the SpringDataRestAdapter for all responses of the Angular $http service then you can add the SpringDataRestInterceptor to the $httpProvider.interceptors in an Angular configuration block:

myApp.config(function (SpringDataRestInterceptorProvider) {
    SpringDataRestInterceptorProvider.apply();
});

The apply method will automatically add the SpringDataRestInterceptor to the $httpProvider.interceptors.

Dependencies

The spring-data-rest Angular module requires the ngResource Angular module.

Release notes

Check them here: Release notes

Acknowledgements

When I first searched for an Angular module for Spring Data REST I just found the marvelous project of Jeremy which is useful if you just use Spring HATEOAS. So please have a look at his angular-hateoas project because he gave me the full permissions to use his code base and project structure for this project here. At this point I want to thank him for his nice work.

License

This Angular module is available under the MIT license.

(c) All rights reserved Guy Brand