Does the YouTube Data API Client Library for Java use Etags and/or gzip, as described at Getting started page?
Documentation is short (only find java docs) and don't say anything about it, so i guess is just a wrapper.
Based from this link, Etags are supported by youtube but it depends on what kind of data you are asking.
To use the etag, create a header request and put "If-None-Match" equal to your etag value. Note this should be a request header and not appended to the endpoint call. You can also use "If-Match".
Depending on what kind of API you are using, the way of inserting a new value to the request header may differ slightly. The ETag response-header field provides the current value of the entity tag for the requested variant.
You may also check on this related thread.
Related
Given a known OData endpoint, what's the best way to determine the version of the OData service? The client in this scenario can support any version (1-4) but I need to know how to format the request.
For example, the OData-Version returns "4.0" for a V4 service, but a V3 service wouldn't even have that header.
In addition, querying the service root URL could be quite expensive for a service with a large number of entities. For example, a basic Dynamics 2016 Online service with no custom objects returns 2.7KB of data, when all I really want is the version header.
So what is the lightest-weight solution for getting a reliable version number? It's ok if the solution is "check this or, if missing, then check that". What's the "this" and "that"?
I found one question (How to find OData version from metadata) which seemed to get me partly there, but there are some issues with the answer.
First, it's focused on finding min/max version numbers where I would really prefer the max.
Second, it requires querying metadata, but that's a potentially massive load. /$metadata on Dynamics CRM 2016 Online results in a 3.7MB response (that takes 30 seconds to download on my current connection). I thought about requesting a dummy entity, like /dummy__entity and then examining the headers, but that seems a bit iffy to me because it would unnecessarily trigger error logging on the server and I'm not sure that an error response is always likely to have the headers I'm looking for.
OData 1.0/2.0/3.0
According to MS-ODATA 1.7 Versioning and Capability Negotiation:
The OData protocol that is defined in this document enables limited capability negotiation using the DataServiceVersion (section 2.2.5.3) and MaxDataServiceVersion (section 2.2.5.7) version request headers and the DataServiceVersion (section 2.2.5.3) response header.
When it says "limited", it means limited:
In a response from the server to the client, the DataServiceVersion (section 2.2.5.3) header is specified. The value states the version of the protocol that the server used in the request to generate the response and that is used by the client to determine if it can correctly interpret the response (that is, the value is not larger than the value of the MaxDataServiceVersion (section 2.2.5.7) header sent in the associated request). The value of the header is the lowest version of the protocol the server can use to fulfill the request.
So, basically, a conformant service capable of handling OData versions 1.0 to 3.0 would return "1.0" for features defined by OData 1.0, "2.0" for features defined by OData 2.0 and not present in OData 1.0, etc.
OData 4.0
According to OData Version 4.0 Part 1: Protocol, Section 8.1.5 Header OData-Version
OData services MUST include the OData-Version header on a response to specify the version of the protocol used to generate the response. The client MUST interpret the response according to the rules defined in the specified version of the protocol.
According to What's New in OData Version 4.0, Section 2.1.1 Improved: Protocol Versioning
Services now respond with the maximum protocol version supported by the server and indicated acceptable by the client.
Also "downgrade" to versions prior to 4.0 is not covered, and service publishers are advised to use new service root URLs for 4.0 services.
So for future versions of OData, from 4.0 onward, it seems that I can reliably get the maximum version I was seeking.
Conclusion
There is no apparent way to get the maximum version of OData supported by a pre-4.0 service. The DataServiceVersion response header will contain the lowest possible version number based on the URL features present, the version of OData that the service supports and the client-requested version.
However, beginning with OData 4.0, the OData-Version response header will always contain the maximum version based on what the service supports and what the client requested.
Unfortunately, in every instance I've tried so far, passing a "DataServiceVersion" header to an OData 4.0 service results in a 500 Internal Server Error response (with no OData-Version header). So it would seem that sending both OData-Version and DataServiceVersion headers isn't guaranteed to work.
Best bet seems to be sending OData-Version and then looking for a DataServiceVersion response header (which will likely be "1.0" even for a service that supports 3.0). If that header is present in the response, then send a second request with a DataServiceVersion header of "3.0". If you get a 4xx response, then try "2.0" etc.
I'm trying to use etags in order to reduce both my bandwidth and my quota usage but /search returns an new etag even when nothing changed. It also still sends the content if I specify the previous etag in the header.
Is it supported for that api call or am I probably doing something wrong?
Etags are supported by youtube but it depends on what kind of data you are asking
ETags, a standard part of the HTTP protocol, allow applications to refer to a specific version of a particular API resource. The resource could be an entire feed or an item in that feed. This functionality supports the following use cases:
Caching and conditional retrieval – Your application can cache API
resources and their ETags. Then, when your application requests a
stored resource again, it specifies the ETag associated with that
resource. If the resource has changed, the API returns the modified
resource and the ETag associated with that version of the resource. If
the resource has not changed, the API returns an HTTP 304 response
(Not Modified), which indicates that the resource has not changed.
Your application can reduce latency and bandwidth usage by serving
cached resources in this manner.
The client libraries for Google APIs differ in their support of ETags.
For example, the JavaScript client library supports ETags via a
whitelist for allowed request headers that includes If-Match and
If-None-Match. The whitelist allows normal browser caching to occur so
that if a resource's ETag has not changed, the resource can be served
from the browser cache. The Obj-C client, on the other hand, does not
support ETags. Protecting against inadvertent overwrites of changes –
ETags help to ensure that multiple API clients don't inadvertently
overwrite each other's changes. When updating or deleting a resource,
your application can specify the resource's ETag. If the ETag doesn't
match the most recent version of that resource, then the API request
fails.
Using ETags in your application provides several benefits:
The API responds more quickly to requests for cached but unchanged
resources, yielding lower latency and lower bandwidth usage. Your
application will not inadvertently overwrite changes to a resource
that were made from another API client.
https://developers.google.com/youtube/v3/getting-started#etags
I usually scrape Youtube for Videos searches and I just store the Etag that it return. To use the etag, create a header request and put "If-None-Match" equal to your etag value. Note this should be a request header and not appended to the endpoint call. You can also use "If-Match".
Depending on what kind of API you are using, the way of inserting a new value to the request header may differ slightly
I use the youtube api v3 and i would like to understand how does the Etag. I would like to use it for what it takes to cache purpose but I do not know what to do in PHP.
Could you tell me the steps to follow once the etag recovered ? please. Thanks for help.
According to the youtube docs (https://developers.google.com/youtube/v3/getting-started#etags), an eTag is basically used to determine if a resource has changed. Use them for:
Optimization - Caching youtube resources in your app can reduce bandwidth and latency. When caching, store the eTag so that you can include it when getting a resource. If the resource has not changed, you will get a 304 response code (NOT MODIFIED), which means you can use your cached version. Otherwise, you will get the updated version of the resource.
Quota Usage - You can reduce the amount you tap into your quota by caching youtube data. The first time you get the resource, you will tap into your quota. Before displaying the resource, first check to see if your cached resource has changed, which will only cost you 1 quota unit. If the resource has not changed, youtube will return a 304 response. If it has changed, you can get the resource again, costing various quota units depending on what you are getting. For more on your quota: (https://developers.google.com/youtube/v3/getting-started#quota).
Overwrite protection - If you are overwriting a resource, including the eTag will ensure that you are not overwriting a newer version of the resource.
eTags are part of the HTTP 1.1 spec (http://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.19) and are used in the headers of the request/response. Here's a good article that talks about them at a low level: http://www.ibuildings.com/blog/2013/07/etags-uninitiated
As far as using eTags in PHP, I can only suggest a couple things since I've never done it. YouTube returns eTags for feeds AND individual items within a feed, and I'm not sure how to use them for individual items within a feed. But to get the original feed itself, essentially you would use curl and add the eTag to the header of your request (PHP cURL custom headers). You might also want to check out http_cache_etag (http://www.php.net/manual/en/function.http-cache-etag.php)
I was looking for similar information, but I couldn't find a clear example on the youtube website. On the other hand, it seems facebook is using a similar approach (Etags to check whether a resource has changed) and these two links I found on facebook developers area might be of help:
https://developers.facebook.com/docs/reference/ads-api/etags-reference/ and https://developers.facebook.com/blog/post/627/
The first one explains in a simpler and more detailed way how etags are used and provide some request/response examples.
The second link provides a PHP example on how to retrieve a resource and extract the etag and use it in a subsequent request.
Of course these links contain information related to facebook website, but for the great part they can be applied to youtube as well.
I am not sure if anyone would still be interested but I have posted an answer on how to use etag in using the youtube api here. The idea works not only for the youtube api. The post is quite long but hope it can help.
Can anyone help me in understanding the differences between JSON, JSONP & CORS, from an asp.net MVC perspective?
JSON is a data format, while JSON-P and CORS are mechanisms/protocols for making cross-domain requests for data.
JSON is a format for representing data. It was first defined in JavaScript, but has grown to become a de facto way for APIs to represent data. Most languages have libraries for parsing JSON. You can learn more about this format here: http://json.org/. Here's an example JSON object:
{
"key": "value"
}
JSON-P is a mechanism for loading data in JavaScript. It bypasses the browser's same-origin policy in order to load data from another domain. It does this by embedding a JavaScript script on the page. This script calls out to the remote domain, which returns data wrapped in a JavaScript function. When this function returns to the browser, it is executed, which allows the calling code to access the data.
Note that while the name has the word "JSON", JSON-P doesn't necessarily have to work with JSON. For example, it could return a string or any other valid JavaScript data type back to the user.
Note that while JSON-P works in every browser, it is a hack to get around the browser's same-origin policy, and it has some limitations. For example, it can only issue a GET request, and the caller doesn't have access to the response headers. Since it is custom to browsers and JavaScript, JSON-P is not really appropriate for accessing data from other languages, like server-side Python.
You can learn more about JSON-P here: http://en.wikipedia.org/wiki/JSONP
CORS is a standardized mechanism for making cross-domain requests. It is supported in most modern browsers. The client uses the standard XmlHttpRequest object to make a CORS request. Upon receiving the request, the server decides whether the cross-domain request is allowed. If it is allowed, the server issues special headers that allows the response to be passed on to the client.
You can find the CORS spec here: http://www.w3.org/TR/cors/
You can learn more about how to use CORS here: http://www.html5rocks.com/en/tutorials/cors/
All these technologies are independent of ASP.NET MVC. If you'd like to use these technologies, you should first ask yourself "Do I need to access data across domains?" If the answer is "yes", you should then ask "What browsers/platforms do I need to support?" If your answer is "most modern browsers", then you should consider implementing CORS. Otherwise you should use JSON-P
CORS is a specification which has nothing to do with JSONP beyond making it obsolete in newer browsers. It enables cross-domain requests using ordinary XMLHttpRequest calls.
Here's an overview of how it works and how to use it. It can be used in Firefox 3.5+, Safari 4+, Chrome 3+, Internet Explorer 8+, and anything else using one of the same engines.
for details go on reading
http://json-p.org/
I'm working a custom SpringSecurityFilter for my Grails application and I'm trying to use the commons upload library to process the request. I'm able to process the request in the filter but once it gets to my controller, none of the values are available.
Can the HttpRequest only be processed once by the upload library? I'm guessing it's cleaning up the temp files. Is there a way to keep them around so they can be processed again at the controller level?
I need to interrogate a form parameter for the security (due to the client I can't add it to the http headers) but once I get the value, it seems to wipe the request for further processing.
Yes. A Request can only be parsed once.
I saw this answer on Apache's FAQ page for FileUpload.
Question: Why is parseRequest() returning no items?
Answer: "This most commonly happens when the request has already been parsed, or processed in some other way. Since the input stream has aleady been consumed by that earlier process, it is no longer available for parsing by Commons FileUpload."
Reference: http://commons.apache.org/fileupload/faq.html