RESTFUL WEB API PDF
Praise for RESTful Web APIs. “This book is the best place to start learning the essential craft of API Design.” —Matt McLarty. Cofounder, API. RESTful Web APIs was designed as a complete replacement for RESTful Web Download RESTful Web Services (PDF) · Read RESTful Web Services online. A. Some Resources for REST and Some RESTful Resources. . that fall short of RESTfulness, like the zetom.info social bookmarking API, and.
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With this free book, you'll learn what it takes to design usable REST APIs that eBook Multiple Formats: HTML, PDF, ePub, Mobi (Kindle), Daisy; Language. This essay does not attempt to explain the basics about REST, Before we dive fully into RESTful API design, it makes sense to look in a little. scalable and maintainable and are very commonly used to create APIs for web- based applications. This tutorial will teach you the basics of RESTful Web.
The server processes the patch document to perform the update. The patch document doesn't describe the whole resource, only a set of changes to apply. The format must be inferred from the media type in the request. JSON merge patch is somewhat simpler. The patch document has the same structure as the original JSON resource, but includes just the subset of fields that should be changed or added.
In addition, a field can be deleted by specifying null for the field value in the patch document. That means merge patch is not suitable if the original resource can have explicit null values. This tells the server to update price , delete color , and add size — name and category are not modified.
Merge patch is not suitable if the original resource can contain explicit null values, due to the special meaning of null in the patch document. Also, the patch document doesn't specify the order that the server should apply the updates. That may or may not matter, depending on the data and the domain. It specifies the changes as a sequence of operations to apply. Operations include add, remove, replace, copy, and test to validate values. If the delete operation is successful, the web server should respond with HTTP status code , indicating that the process has been successfully handled, but that the response body contains no further information.
If you wait for completion before sending a response to the client, it may cause unacceptable latency. If so, consider making the operation asynchronous. Return HTTP status code Accepted to indicate the request was accepted for processing but is not completed. You should expose an endpoint that returns the status of an asynchronous request, so the client can monitor the status by polling the status endpoint. Include the URI of the status endpoint in the Location header of the response.
If the client sends a GET request to this endpoint, the response should contain the current status of the request.
Optionally, it could also include an estimated time to completion or a link to cancel the operation. If the asynchronous operation creates a new resource, the status endpoint should return status code See Other after the operation completes. In the response, include a Location header that gives the URI of the new resource:.
Exposing a collection of resources through a single URI can lead to applications fetching large amounts of data when only a subset of the information is required. For example, suppose a client application needs to find all orders with a cost over a specific value.
Clearly this process is highly inefficient. It wastes network bandwidth and processing power on the server hosting the web API. The web API is then responsible for parsing and handling the minCost parameter in the query string and returning the filtered results on the server side. GET requests over collection resources can potentially return a large number of items. You should design a web API to limit the amount of data returned by any single request.
Consider supporting query strings that specify the maximum number of items to retrieve and a starting offset into the collection.
Also consider imposing an upper limit on the number of items returned, to help prevent Denial of Service attacks. To assist client applications, GET requests that return paginated data should also include some form of metadata that indicate the total number of resources available in the collection.
However, this approach can have a negative effect on caching, because query string parameters form part of the resource identifier used by many cache implementations as the key to cached data.
You can extend this approach to limit the fields returned for each item, if each item contains a large amount of data. Give all optional parameters in query strings meaningful defaults. For example, set the limit parameter to 10 and the offset parameter to 0 if you implement pagination, set the sort parameter to the key of the resource if you implement ordering, and set the fields parameter to all fields in the resource if you support projections. A resource may contain large binary fields, such as files or images.
To overcome problems caused by unreliable and intermittent connections and to improve response times, consider enabling such resources to be retrieved in chunks.
This header indicates that the GET operation supports partial requests. The client application can submit GET requests that return a subset of a resource, specified as a range of bytes. The Content-Length header gives the total size of the resource, and the Accept-Ranges header indicates that the corresponding GET operation supports partial results.
The client application can use this information to retrieve the image in smaller chunks. The first request fetches the first bytes by using the Range header:. The response message indicates that this is a partial response by returning HTTP status code The Content-Length header specifies the actual number of bytes returned in the message body not the size of the resource , and the Content-Range header indicates which part of the resource this is bytes out of One of the primary motivations behind REST is that it should be possible to navigate the entire set of resources without requiring prior knowledge of the URI scheme.
Each HTTP GET request should return the information necessary to find the resources related directly to the requested object through hyperlinks included in the response, and it should also be provided with information that describes the operations available on each of these resources. The system is effectively a finite state machine, and the response to each request contains the information necessary to move from one state to another; no other information should be necessary.
The examples shown in this section illustrate one possible solution.
For example, to handle the relationship between an order and a customer, the representation of an order could include links that identify the available operations for the customer of the order. Here is a possible representation:. In this example, the links array has a set of links.
Each link represents an operation on a related entity.
The data for each link includes the relationship "customer" , the URI https: This is all the information that a client application needs to be able to invoke the operation.
The links array also includes self-referencing information about the resource itself that has been retrieved. These have the relationship self. The set of links that are returned may change, depending on the state of the resource. This is what is meant by hypertext being the "engine of application state.
It is highly unlikely that a web API will remain static. As business requirements change new collections of resources may be added, the relationships between resources might change, and the structure of the data in resources might be amended.
While updating a web API to handle new or differing requirements is a relatively straightforward process, you must consider the effects that such changes will have on client applications consuming the web API.
The issue is that although the developer designing and implementing a web API has full control over that API, the developer does not have the same degree of control over client applications which may be built by third party organizations operating remotely.
The primary imperative is to enable existing client applications to continue functioning unchanged while allowing new client applications to take advantage of new features and resources. Versioning enables a web API to indicate the features and resources that it exposes, and a client application can submit requests that are directed to a specific version of a feature or resource.
The following sections describe several different approaches, each of which has its own benefits and trade-offs. This is the simplest approach, and may be acceptable for some internal APIs. Big changes could be represented as new resources or new links. Adding content to existing resources might not present a breaking change as client applications that are not expecting to see this content will simply ignore it.
For example, a request to the URI https: If the DateCreated field is added to the schema of the customer resource, then the response would look like this:.
Existing client applications might continue functioning correctly if they are capable of ignoring unrecognized fields, while new client applications can be designed to handle this new field.
However, if more radical changes to the schema of resources occur such as removing or renaming fields or the relationships between resources change then these may constitute breaking changes that prevent existing client applications from functioning correctly. In these situations you should consider one of the following approaches. Each time you modify the web API or change the schema of resources, you add a version number to the URI for each resource. The previously existing URIs should continue to operate as before, returning resources that conform to their original schema.
Extending the previous example, if the address field is restructured into sub-fields containing each constituent part of the address such as streetAddress , city , state , and zipCode , this version of the resource could be exposed through a URI containing a version number, such as https: This versioning mechanism is very simple but depends on the server routing the request to the appropriate endpoint.
However, it can become unwieldy as the web API matures through several iterations and the server has to support a number of different versions. Rather than providing multiple URIs, you can specify the version of the resource by using a parameter within the query string appended to the HTTP request, such as https: The version parameter should default to a meaningful value such as 1 if it is omitted by older client applications. This approach has the semantic advantage that the same resource is always retrieved from the same URI, but it depends on the code that handles the request to parse the query string and send back the appropriate HTTP response.
Some older web browsers and web proxies will not cache responses for requests that include a query string in the URI. This can degrade performance for web applications that use a web API and that run from within such a web browser.
Rather than appending the version number as a query string parameter, you could implement a custom header that indicates the version of the resource.
This approach requires that the client application adds the appropriate header to any requests, although the code handling the client request could use a default value version 1 if the version header is omitted. The following examples use a custom header named Custom-Header. The value of this header indicates the version of web API.
When a client application sends an HTTP GET request to a web server it should stipulate the format of the content that it can handle by using an Accept header, as described earlier in this guidance.
Frequently the purpose of the Accept header is to allow the client application to specify whether the body of the response should be XML, JSON, or some other common format that the client can parse.
However, it is possible to define custom media types that include information enabling the client application to indicate which version of a resource it is expecting. The vnd. The code handling the request is responsible for processing the Accept header and honoring it as far as possible the client application may specify multiple formats in the Accept header, in which case the web server can choose the most appropriate format for the response body. The web server confirms the format of the data in the response body by using the Content-Type header:.
If the Accept header does not specify any known media types, the web server could generate an HTTP Not Acceptable response message or return a message with a default media type. When you select a versioning strategy, you should also consider the implications on performance, especially caching on the web server.
The Header versioning and Media Type versioning mechanisms typically require additional logic to examine the values in the custom header or the Accept header. In a large-scale environment, many clients using different versions of a web API can result in a significant amount of duplicated data in a server-side cache. This issue can become acute if a client application communicates with a web server through a proxy that implements caching, and that only forwards a request to the web server if it does not currently hold a copy of the requested data in its cache.
As part of this initiative, the Swagger 2. That has advantages for interoperability, but requires more care when designing your API to conform to the specification. OpenAPI promotes a contract-first approach, rather than an implementation-first approach.
Contract-first means you design the API contract the interface first and then write code that implements the contract. Tools like Swagger can generate client libraries or documentation from API contracts.
For example, see ASP.
Web API Checklist. A useful list of items to consider when designing and implementing a web API.
Open API Initiative. Documentation and implementation details on Open API. Exit focus mode. In this article. A well-designed web API should aim to support: This guidance describes issues that you should consider when designing a web API.
For example, the URI for a particular customer order might be: Level 0: Partial download involves downloading only a specified portion of a file. You can specify the portion of the file you want to dowload by using a byte range with the Range header. Download Google Documents using the files. The about resource contains additional information about available export formats for each file type.
If you want to allow a user to view a file directly in a web browser instead of through the API, use the webContentLink.
You can either redirect a user to this URL, or offer it as a clickable link.
The file must be either owned by or shared with the user in order to view it. Except as otherwise noted, the content of this page is licensed under the Creative Commons Attribution 3. For details, see our Site Policies. Last updated April 1, Depending on the type of download you'd like to perform — a file, a Google Document, or a content link — you'll use one of the following URLs: Download a file — files.
For example: GET https: Send feedback about Documentation feedback.This issue can become acute if a client application communicates with a web server through a proxy that implements caching, and that only forwards a request to the web server if it does not currently hold a copy of the requested data in its cache.
Instead, try to keep URIs relatively simple. Entities are often grouped together into collections orders, customers. WriteLine "Download complete. Create separate URIs for individual resources.
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