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  • Partner Blog Series: PwC Perspectives - The Gotchas, The Do's and Don'ts for IDM Implementations

    - by Tanu Sood
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mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Arial; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;} table.MsoTableMediumList1Accent6 {mso-style-name:"Medium List 1 - Accent 6"; mso-tstyle-rowband-size:1; mso-tstyle-colband-size:1; mso-style-priority:65; mso-style-unhide:no; border-top:solid #E0301E 1.0pt; mso-border-top-themecolor:accent6; border-left:none; border-bottom:solid #E0301E 1.0pt; mso-border-bottom-themecolor:accent6; border-right:none; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:10.0pt; font-family:"Georgia","serif"; color:black; mso-themecolor:text1; mso-ansi-language:EN-GB;} table.MsoTableMediumList1Accent6FirstRow {mso-style-name:"Medium List 1 - Accent 6"; mso-table-condition:first-row; mso-style-priority:65; mso-style-unhide:no; mso-tstyle-border-top:cell-none; mso-tstyle-border-bottom:1.0pt solid #E0301E; mso-tstyle-border-bottom-themecolor:accent6; font-family:"Arial Narrow","sans-serif"; mso-ascii-font-family:Georgia; mso-ascii-theme-font:major-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:major-fareast; mso-hansi-font-family:Georgia; mso-hansi-theme-font:major-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:major-bidi;} table.MsoTableMediumList1Accent6LastRow {mso-style-name:"Medium List 1 - Accent 6"; mso-table-condition:last-row; mso-style-priority:65; mso-style-unhide:no; mso-tstyle-border-top:1.0pt solid #E0301E; mso-tstyle-border-top-themecolor:accent6; mso-tstyle-border-bottom:1.0pt solid #E0301E; mso-tstyle-border-bottom-themecolor:accent6; color:#968C6D; mso-themecolor:text2; mso-ansi-font-weight:bold; mso-bidi-font-weight:bold;} table.MsoTableMediumList1Accent6FirstCol {mso-style-name:"Medium List 1 - Accent 6"; mso-table-condition:first-column; mso-style-priority:65; mso-style-unhide:no; mso-ansi-font-weight:bold; mso-bidi-font-weight:bold;} table.MsoTableMediumList1Accent6LastCol {mso-style-name:"Medium List 1 - Accent 6"; mso-table-condition:last-column; mso-style-priority:65; mso-style-unhide:no; mso-tstyle-border-top:1.0pt solid #E0301E; mso-tstyle-border-top-themecolor:accent6; mso-tstyle-border-bottom:1.0pt solid #E0301E; mso-tstyle-border-bottom-themecolor:accent6; mso-ansi-font-weight:bold; mso-bidi-font-weight:bold;} table.MsoTableMediumList1Accent6OddColumn {mso-style-name:"Medium List 1 - Accent 6"; mso-table-condition:odd-column; mso-style-priority:65; mso-style-unhide:no; mso-tstyle-shading:#F7CBC7; mso-tstyle-shading-themecolor:accent6; mso-tstyle-shading-themetint:63;} table.MsoTableMediumList1Accent6OddRow {mso-style-name:"Medium List 1 - Accent 6"; mso-table-condition:odd-row; mso-style-priority:65; mso-style-unhide:no; mso-tstyle-shading:#F7CBC7; mso-tstyle-shading-themecolor:accent6; mso-tstyle-shading-themetint:63;} It is generally accepted among business communities that technology by itself is not a silver bullet to all problems, but when it is combined with leading practices, strategy, careful planning and execution, it can create a recipe for success. This post attempts to highlight some of the best practices along with dos & don’ts that our practice has accumulated over the years in the identity & access management space in general, and also in the context of R2, in particular. Best Practices The following section illustrates the leading practices in “How” to plan, implement and sustain a successful OIM deployment, based on our collective experience. Planning is critical, but often overlooked A common approach to planning an IAM program that we identify with our clients is the three step process involving a current state assessment, a future state roadmap and an executable strategy to get there. It is extremely beneficial for clients to assess their current IAM state, perform gap analysis, document the recommended controls to address the gaps, align future state roadmap to business initiatives and get buy in from all stakeholders involved to improve the chances of success. When designing an enterprise-wide solution, the scalability of the technology must accommodate the future growth of the enterprise and the projected identity transactions over several years. Aligning the implementation schedule of OIM to related information technology projects increases the chances of success. As a baseline, it is recommended to match hardware specifications to the sizing guide for R2 published by Oracle. Adherence to this will help ensure that the hardware used to support OIM will not become a bottleneck as the adoption of new services increases. If your Organization has numerous connected applications that rely on reconciliation to synchronize the access data into OIM, consider hosting dedicated instances to handle reconciliation. Finally, ensure the use of clustered environment for development and have at least three total environments to help facilitate a controlled migration to production. If your Organization is planning to implement role based access control, we recommend performing a role mining exercise and consolidate your enterprise roles to keep them manageable. In addition, many Organizations have multiple approval flows to control access to critical roles, applications and entitlements. If your Organization falls into this category, we highly recommend that you limit the number of approval workflows to a small set. Most Organizations have operations managed across data centers with backend database synchronization, if your Organization falls into this category, ensure that the overall latency between the datacenters when replicating the databases is less than ten milliseconds to ensure that there are no front office performance impacts. Ingredients for a successful implementation During the development phase of your project, there are a number of guidelines that can be followed to help increase the chances for success. Most implementations cannot be completed without the use of customizations. If your implementation requires this, it’s a good practice to perform code reviews to help ensure quality and reduce code bottlenecks related to performance. We have observed at our clients that the development process works best when team members adhere to coding leading practices. Plan for time to correct coding defects and ensure developers are empowered to report their own bugs for maximum transparency. Many organizations struggle with defining a consistent approach to managing logs. This is particularly important due to the amount of information that can be logged by OIM. We recommend Oracle Diagnostics Logging (ODL) as an alternative to be used for logging. ODL allows log files to be formatted in XML for easy parsing and does not require a server restart when the log levels are changed during troubleshooting. Testing is a vital part of any large project, and an OIM R2 implementation is no exception. We suggest that at least one lower environment should use production-like data and connectors. Configurations should match as closely as possible. For example, use secure channels between OIM and target platforms in pre-production environments to test the configurations, the migration processes of certificates, and the additional overhead that encryption could impose. Finally, we ask our clients to perform database backups regularly and before any major change event, such as a patch or migration between environments. In the lowest environments, we recommend to have at least a weekly backup in order to prevent significant loss of time and effort. Similarly, if your organization is using virtual machines for one or more of the environments, it is recommended to take frequent snapshots so that rollbacks can occur in the event of improper configuration. Operate & sustain the solution to derive maximum benefits When migrating OIM R2 to production, it is important to perform certain activities that will help achieve a smoother transition. At our clients, we have seen that splitting the OIM tables into their own tablespaces by categories (physical tables, indexes, etc.) can help manage database growth effectively. If we notice that a client hasn’t enabled the Oracle-recommended indexing in the applicable database, we strongly suggest doing so to improve performance. Additionally, we work with our clients to make sure that the audit level is set to fit the organization’s auditing needs and sometimes even allocate UPA tables and indexes into their own table-space for better maintenance. Finally, many of our clients have set up schedules for reconciliation tables to be archived at regular intervals in order to keep the size of the database(s) reasonable and result in optimal database performance. For our clients that anticipate availability issues with target applications, we strongly encourage the use of the offline provisioning capabilities of OIM R2. This reduces the provisioning process for a given target application dependency on target availability and help avoid broken workflows. To account for this and other abnormalities, we also advocate that OIM’s monitoring controls be configured to alert administrators on any abnormal situations. Within OIM R2, we have begun advising our clients to utilize the ‘profile’ feature to encapsulate multiple commonly requested accounts, roles, and/or entitlements into a single item. By setting up a number of profiles that can be searched for and used, users will spend less time performing the same exact steps for common tasks. We advise our clients to follow the Oracle recommended guides for database and application server tuning which provides a good baseline configuration. It offers guidance on database connection pools, connection timeouts, user interface threads and proper handling of adapters/plug-ins. All of these can be important configurations that will allow faster provisioning and web page response times. Many of our clients have begun to recognize the value of data mining and a remediation process during the initial phases of an implementation (to help ensure high quality data gets loaded) and beyond (to support ongoing maintenance and business-as-usual processes). A successful program always begins with identifying the data elements and assigning a classification level based on criticality, risk, and availability. It should finish by following through with a remediation process. Dos & Don’ts Here are the most common dos and don'ts that we socialize with our clients, derived from our experience implementing the solution. Dos Don’ts Scope the project into phases with realistic goals. Look for quick wins to show success and value to the stake holders. Avoid “boiling the ocean” and trying to integrate all enterprise applications in the first phase. Establish an enterprise ID (universal unique ID across the enterprise) earlier in the program. Avoid major UI customizations that require code changes. Have a plan in place to patch during the project, which helps alleviate any major issues or roadblocks (product and database). Avoid publishing all the target entitlements if you don't anticipate their usage during access request. Assess your current state and prepare a roadmap to address your operations, tactical and strategic goals, align it with your business priorities. Avoid integrating non-production environments with your production target systems. Defer complex integrations to the later phases and take advantage of lessons learned from previous phases Avoid creating multiple accounts for the same user on the same system, if there is an opportunity to do so. Have an identity and access data quality initiative built into your plan to identify and remediate data related issues early on. Avoid creating complex approval workflows that would negative impact productivity and SLAs. Identify the owner of the identity systems with fair IdM knowledge and empower them with authority to make product related decisions. This will help ensure overcome any design hurdles. Avoid creating complex designs that are not sustainable long term and would need major overhaul during upgrades. Shadow your internal or external consulting resources during the implementation to build the necessary product skills needed to operate and sustain the solution. Avoid treating IAM as a point solution and have appropriate level of communication and training plan for the IT and business users alike. Conclusion In our experience, Identity programs will struggle with scope, proper resourcing, and more. We suggest that companies consider the suggestions discussed in this post and leverage them to help enable their identity and access program. This concludes PwC blog series on R2 for the month and we sincerely hope that the information we have shared thus far has been beneficial. For more information or if you have questions, you can reach out to Rex Thexton, Senior Managing Director, PwC and or Dharma Padala, Director, PwC. We look forward to hearing from you. Normal 0 false false false EN-US X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin-top:0in; mso-para-margin-right:0in; mso-para-margin-bottom:12.0pt; mso-para-margin-left:0in; line-height:12.0pt; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Arial","sans-serif"; mso-ascii-font-family:Arial; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Arial; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;} Meet the Writers: Dharma Padala is a Director in the Advisory Security practice within PwC.  He has been implementing medium to large scale Identity Management solutions across multiple industries including utility, health care, entertainment, retail and financial sectors.   Dharma has 14 years of experience in delivering IT solutions out of which he has been implementing Identity Management solutions for the past 8 years. Praveen Krishna is a Manager in the Advisory Security practice within PwC.  Over the last decade Praveen has helped clients plan, architect and implement Oracle identity solutions across diverse industries.  His experience includes delivering security across diverse topics like network, infrastructure, application and data where he brings a holistic point of view to problem solving. Scott MacDonald is a Director in the Advisory Security practice within PwC.  He has consulted for several clients across multiple industries including financial services, health care, automotive and retail.   Scott has 10 years of experience in delivering Identity Management solutions. John Misczak is a member of the Advisory Security practice within PwC.  He has experience implementing multiple Identity and Access Management solutions, specializing in Oracle Identity Manager and Business Process Engineering Language (BPEL).

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  • Capturing and Transforming ASP.NET Output with Response.Filter

    - by Rick Strahl
    During one of my Handlers and Modules session at DevConnections this week one of the attendees asked a question that I didn’t have an immediate answer for. Basically he wanted to capture response output completely and then apply some filtering to the output – effectively injecting some additional content into the page AFTER the page had completely rendered. Specifically the output should be captured from anywhere – not just a page and have this code injected into the page. Some time ago I posted some code that allows you to capture ASP.NET Page output by overriding the Render() method, capturing the HtmlTextWriter() and reading its content, modifying the rendered data as text then writing it back out. I’ve actually used this approach on a few occasions and it works fine for ASP.NET pages. But this obviously won’t work outside of the Page class environment and it’s not really generic – you have to create a custom page class in order to handle the output capture. [updated 11/16/2009 – updated ResponseFilterStream implementation and a few additional notes based on comments] Enter Response.Filter However, ASP.NET includes a Response.Filter which can be used – well to filter output. Basically Response.Filter is a stream through which the OutputStream is piped back to the Web Server (indirectly). As content is written into the Response object, the filter stream receives the appropriate Stream commands like Write, Flush and Close as well as read operations although for a Response.Filter that’s uncommon to be hit. The Response.Filter can be programmatically replaced at runtime which allows you to effectively intercept all output generation that runs through ASP.NET. A common Example: Dynamic GZip Encoding A rather common use of Response.Filter hooking up code based, dynamic  GZip compression for requests which is dead simple by applying a GZipStream (or DeflateStream) to Response.Filter. The following generic routines can be used very easily to detect GZip capability of the client and compress response output with a single line of code and a couple of library helper routines: WebUtils.GZipEncodePage(); which is handled with a few lines of reusable code and a couple of static helper methods: /// <summary> ///Sets up the current page or handler to use GZip through a Response.Filter ///IMPORTANT:  ///You have to call this method before any output is generated! /// </summary> public static void GZipEncodePage() {     HttpResponse Response = HttpContext.Current.Response;     if(IsGZipSupported())     {         stringAcceptEncoding = HttpContext.Current.Request.Headers["Accept-Encoding"];         if(AcceptEncoding.Contains("deflate"))         {             Response.Filter = newSystem.IO.Compression.DeflateStream(Response.Filter,                                        System.IO.Compression.CompressionMode.Compress);             Response.AppendHeader("Content-Encoding", "deflate");         }         else        {             Response.Filter = newSystem.IO.Compression.GZipStream(Response.Filter,                                       System.IO.Compression.CompressionMode.Compress);             Response.AppendHeader("Content-Encoding", "gzip");                            }     }     // Allow proxy servers to cache encoded and unencoded versions separately    Response.AppendHeader("Vary", "Content-Encoding"); } /// <summary> /// Determines if GZip is supported /// </summary> /// <returns></returns> public static bool IsGZipSupported() { string AcceptEncoding = HttpContext.Current.Request.Headers["Accept-Encoding"]; if (!string.IsNullOrEmpty(AcceptEncoding) && (AcceptEncoding.Contains("gzip") || AcceptEncoding.Contains("deflate"))) return true; return false; } GZipStream and DeflateStream are streams that are assigned to Response.Filter and by doing so apply the appropriate compression on the active Response. Response.Filter content is chunked So to implement a Response.Filter effectively requires only that you implement a custom stream and handle the Write() method to capture Response output as it’s written. At first blush this seems very simple – you capture the output in Write, transform it and write out the transformed content in one pass. And that indeed works for small amounts of content. But you see, the problem is that output is written in small buffer chunks (a little less than 16k it appears) rather than just a single Write() statement into the stream, which makes perfect sense for ASP.NET to stream data back to IIS in smaller chunks to minimize memory usage en route. Unfortunately this also makes it a more difficult to implement any filtering routines since you don’t directly get access to all of the response content which is problematic especially if those filtering routines require you to look at the ENTIRE response in order to transform or capture the output as is needed for the solution the gentleman in my session asked for. So in order to address this a slightly different approach is required that basically captures all the Write() buffers passed into a cached stream and then making the stream available only when it’s complete and ready to be flushed. As I was thinking about the implementation I also started thinking about the few instances when I’ve used Response.Filter implementations. Each time I had to create a new Stream subclass and create my custom functionality but in the end each implementation did the same thing – capturing output and transforming it. I thought there should be an easier way to do this by creating a re-usable Stream class that can handle stream transformations that are common to Response.Filter implementations. Creating a semi-generic Response Filter Stream Class What I ended up with is a ResponseFilterStream class that provides a handful of Events that allow you to capture and/or transform Response content. The class implements a subclass of Stream and then overrides Write() and Flush() to handle capturing and transformation operations. By exposing events it’s easy to hook up capture or transformation operations via single focused methods. ResponseFilterStream exposes the following events: CaptureStream, CaptureString Captures the output only and provides either a MemoryStream or String with the final page output. Capture is hooked to the Flush() operation of the stream. TransformStream, TransformString Allows you to transform the complete response output with events that receive a MemoryStream or String respectively and can you modify the output then return it back as a return value. The transformed output is then written back out in a single chunk to the response output stream. These events capture all output internally first then write the entire buffer into the response. TransformWrite, TransformWriteString Allows you to transform the Response data as it is written in its original chunk size in the Stream’s Write() method. Unlike TransformStream/TransformString which operate on the complete output, these events only see the current chunk of data written. This is more efficient as there’s no caching involved, but can cause problems due to searched content splitting over multiple chunks. Using this implementation, creating a custom Response.Filter transformation becomes as simple as the following code. To hook up the Response.Filter using the MemoryStream version event: ResponseFilterStream filter = new ResponseFilterStream(Response.Filter); filter.TransformStream += filter_TransformStream; Response.Filter = filter; and the event handler to do the transformation: MemoryStream filter_TransformStream(MemoryStream ms) { Encoding encoding = HttpContext.Current.Response.ContentEncoding; string output = encoding.GetString(ms.ToArray()); output = FixPaths(output); ms = new MemoryStream(output.Length); byte[] buffer = encoding.GetBytes(output); ms.Write(buffer,0,buffer.Length); return ms; } private string FixPaths(string output) { string path = HttpContext.Current.Request.ApplicationPath; // override root path wonkiness if (path == "/") path = ""; output = output.Replace("\"~/", "\"" + path + "/").Replace("'~/", "'" + path + "/"); return output; } The idea of the event handler is that you can do whatever you want to the stream and return back a stream – either the same one that’s been modified or a brand new one – which is then sent back to as the final response. The above code can be simplified even more by using the string version events which handle the stream to string conversions for you: ResponseFilterStream filter = new ResponseFilterStream(Response.Filter); filter.TransformString += filter_TransformString; Response.Filter = filter; and the event handler to do the transformation calling the same FixPaths method shown above: string filter_TransformString(string output) { return FixPaths(output); } The events for capturing output and capturing and transforming chunks work in a very similar way. By using events to handle the transformations ResponseFilterStream becomes a reusable component and we don’t have to create a new stream class or subclass an existing Stream based classed. By the way, the example used here is kind of a cool trick which transforms “~/” expressions inside of the final generated HTML output – even in plain HTML controls not HTML controls – and transforms them into the appropriate application relative path in the same way that ResolveUrl would do. So you can write plain old HTML like this: <a href=”~/default.aspx”>Home</a>  and have it turned into: <a href=”/myVirtual/default.aspx”>Home</a>  without having to use an ASP.NET control like Hyperlink or Image or having to constantly use: <img src=”<%= ResolveUrl(“~/images/home.gif”) %>” /> in MVC applications (which frankly is one of the most annoying things about MVC especially given the path hell that extension-less and endpoint-less URLs impose). I can’t take credit for this idea. While discussing the Response.Filter issues on Twitter a hint from Dylan Beattie who pointed me at one of his examples which does something similar. I thought the idea was cool enough to use an example for future demos of Response.Filter functionality in ASP.NET next I time I do the Modules and Handlers talk (which was great fun BTW). How practical this is is debatable however since there’s definitely some overhead to using a Response.Filter in general and especially on one that caches the output and the re-writes it later. Make sure to test for performance anytime you use Response.Filter hookup and make sure it' doesn’t end up killing perf on you. You’ve been warned :-}. How does ResponseFilterStream work? The big win of this implementation IMHO is that it’s a reusable  component – so for implementation there’s no new class, no subclassing – you simply attach to an event to implement an event handler method with a straight forward signature to retrieve the stream or string you’re interested in. The implementation is based on a subclass of Stream as is required in order to handle the Response.Filter requirements. What’s different than other implementations I’ve seen in various places is that it supports capturing output as a whole to allow retrieving the full response output for capture or modification. The exception are the TransformWrite and TransformWrite events which operate only active chunk of data written by the Response. For captured output, the Write() method captures output into an internal MemoryStream that is cached until writing is complete. So Write() is called when ASP.NET writes to the Response stream, but the filter doesn’t pass on the Write immediately to the filter’s internal stream. The data is cached and only when the Flush() method is called to finalize the Stream’s output do we actually send the cached stream off for transformation (if the events are hooked up) and THEN finally write out the returned content in one big chunk. Here’s the implementation of ResponseFilterStream: /// <summary> /// A semi-generic Stream implementation for Response.Filter with /// an event interface for handling Content transformations via /// Stream or String. /// <remarks> /// Use with care for large output as this implementation copies /// the output into a memory stream and so increases memory usage. /// </remarks> /// </summary> public class ResponseFilterStream : Stream { /// <summary> /// The original stream /// </summary> Stream _stream; /// <summary> /// Current position in the original stream /// </summary> long _position; /// <summary> /// Stream that original content is read into /// and then passed to TransformStream function /// </summary> MemoryStream _cacheStream = new MemoryStream(5000); /// <summary> /// Internal pointer that that keeps track of the size /// of the cacheStream /// </summary> int _cachePointer = 0; /// <summary> /// /// </summary> /// <param name="responseStream"></param> public ResponseFilterStream(Stream responseStream) { _stream = responseStream; } /// <summary> /// Determines whether the stream is captured /// </summary> private bool IsCaptured { get { if (CaptureStream != null || CaptureString != null || TransformStream != null || TransformString != null) return true; return false; } } /// <summary> /// Determines whether the Write method is outputting data immediately /// or delaying output until Flush() is fired. /// </summary> private bool IsOutputDelayed { get { if (TransformStream != null || TransformString != null) return true; return false; } } /// <summary> /// Event that captures Response output and makes it available /// as a MemoryStream instance. Output is captured but won't /// affect Response output. /// </summary> public event Action<MemoryStream> CaptureStream; /// <summary> /// Event that captures Response output and makes it available /// as a string. Output is captured but won't affect Response output. /// </summary> public event Action<string> CaptureString; /// <summary> /// Event that allows you transform the stream as each chunk of /// the output is written in the Write() operation of the stream. /// This means that that it's possible/likely that the input /// buffer will not contain the full response output but only /// one of potentially many chunks. /// /// This event is called as part of the filter stream's Write() /// operation. /// </summary> public event Func<byte[], byte[]> TransformWrite; /// <summary> /// Event that allows you to transform the response stream as /// each chunk of bytep[] output is written during the stream's write /// operation. This means it's possibly/likely that the string /// passed to the handler only contains a portion of the full /// output. Typical buffer chunks are around 16k a piece. /// /// This event is called as part of the stream's Write operation. /// </summary> public event Func<string, string> TransformWriteString; /// <summary> /// This event allows capturing and transformation of the entire /// output stream by caching all write operations and delaying final /// response output until Flush() is called on the stream. /// </summary> public event Func<MemoryStream, MemoryStream> TransformStream; /// <summary> /// Event that can be hooked up to handle Response.Filter /// Transformation. Passed a string that you can modify and /// return back as a return value. The modified content /// will become the final output. /// </summary> public event Func<string, string> TransformString; protected virtual void OnCaptureStream(MemoryStream ms) { if (CaptureStream != null) CaptureStream(ms); } private void OnCaptureStringInternal(MemoryStream ms) { if (CaptureString != null) { string content = HttpContext.Current.Response.ContentEncoding.GetString(ms.ToArray()); OnCaptureString(content); } } protected virtual void OnCaptureString(string output) { if (CaptureString != null) CaptureString(output); } protected virtual byte[] OnTransformWrite(byte[] buffer) { if (TransformWrite != null) return TransformWrite(buffer); return buffer; } private byte[] OnTransformWriteStringInternal(byte[] buffer) { Encoding encoding = HttpContext.Current.Response.ContentEncoding; string output = OnTransformWriteString(encoding.GetString(buffer)); return encoding.GetBytes(output); } private string OnTransformWriteString(string value) { if (TransformWriteString != null) return TransformWriteString(value); return value; } protected virtual MemoryStream OnTransformCompleteStream(MemoryStream ms) { if (TransformStream != null) return TransformStream(ms); return ms; } /// <summary> /// Allows transforming of strings /// /// Note this handler is internal and not meant to be overridden /// as the TransformString Event has to be hooked up in order /// for this handler to even fire to avoid the overhead of string /// conversion on every pass through. /// </summary> /// <param name="responseText"></param> /// <returns></returns> private string OnTransformCompleteString(string responseText) { if (TransformString != null) TransformString(responseText); return responseText; } /// <summary> /// Wrapper method form OnTransformString that handles /// stream to string and vice versa conversions /// </summary> /// <param name="ms"></param> /// <returns></returns> internal MemoryStream OnTransformCompleteStringInternal(MemoryStream ms) { if (TransformString == null) return ms; //string content = ms.GetAsString(); string content = HttpContext.Current.Response.ContentEncoding.GetString(ms.ToArray()); content = TransformString(content); byte[] buffer = HttpContext.Current.Response.ContentEncoding.GetBytes(content); ms = new MemoryStream(); ms.Write(buffer, 0, buffer.Length); //ms.WriteString(content); return ms; } /// <summary> /// /// </summary> public override bool CanRead { get { return true; } } public override bool CanSeek { get { return true; } } /// <summary> /// /// </summary> public override bool CanWrite { get { return true; } } /// <summary> /// /// </summary> public override long Length { get { return 0; } } /// <summary> /// /// </summary> public override long Position { get { return _position; } set { _position = value; } } /// <summary> /// /// </summary> /// <param name="offset"></param> /// <param name="direction"></param> /// <returns></returns> public override long Seek(long offset, System.IO.SeekOrigin direction) { return _stream.Seek(offset, direction); } /// <summary> /// /// </summary> /// <param name="length"></param> public override void SetLength(long length) { _stream.SetLength(length); } /// <summary> /// /// </summary> public override void Close() { _stream.Close(); } /// <summary> /// Override flush by writing out the cached stream data /// </summary> public override void Flush() { if (IsCaptured && _cacheStream.Length > 0) { // Check for transform implementations _cacheStream = OnTransformCompleteStream(_cacheStream); _cacheStream = OnTransformCompleteStringInternal(_cacheStream); OnCaptureStream(_cacheStream); OnCaptureStringInternal(_cacheStream); // write the stream back out if output was delayed if (IsOutputDelayed) _stream.Write(_cacheStream.ToArray(), 0, (int)_cacheStream.Length); // Clear the cache once we've written it out _cacheStream.SetLength(0); } // default flush behavior _stream.Flush(); } /// <summary> /// /// </summary> /// <param name="buffer"></param> /// <param name="offset"></param> /// <param name="count"></param> /// <returns></returns> public override int Read(byte[] buffer, int offset, int count) { return _stream.Read(buffer, offset, count); } /// <summary> /// Overriden to capture output written by ASP.NET and captured /// into a cached stream that is written out later when Flush() /// is called. /// </summary> /// <param name="buffer"></param> /// <param name="offset"></param> /// <param name="count"></param> public override void Write(byte[] buffer, int offset, int count) { if ( IsCaptured ) { // copy to holding buffer only - we'll write out later _cacheStream.Write(buffer, 0, count); _cachePointer += count; } // just transform this buffer if (TransformWrite != null) buffer = OnTransformWrite(buffer); if (TransformWriteString != null) buffer = OnTransformWriteStringInternal(buffer); if (!IsOutputDelayed) _stream.Write(buffer, offset, buffer.Length); } } The key features are the events and corresponding OnXXX methods that handle the event hookups, and the Write() and Flush() methods of the stream implementation. All the rest of the members tend to be plain jane passthrough stream implementation code without much consequence. I do love the way Action<t> and Func<T> make it so easy to create the event signatures for the various events – sweet. A few Things to consider Performance Response.Filter is not great for performance in general as it adds another layer of indirection to the ASP.NET output pipeline, and this implementation in particular adds a memory hit as it basically duplicates the response output into the cached memory stream which is necessary since you may have to look at the entire response. If you have large pages in particular this can cause potentially serious memory pressure in your server application. So be careful of wholesale adoption of this (or other) Response.Filters. Make sure to do some performance testing to ensure it’s not killing your app’s performance. Response.Filter works everywhere A few questions came up in comments and discussion as to capturing ALL output hitting the site and – yes you can definitely do that by assigning a Response.Filter inside of a module. If you do this however you’ll want to be very careful and decide which content you actually want to capture especially in IIS 7 which passes ALL content – including static images/CSS etc. through the ASP.NET pipeline. So it is important to filter only on what you’re looking for – like the page extension or maybe more effectively the Response.ContentType. Response.Filter Chaining Originally I thought that filter chaining doesn’t work at all due to a bug in the stream implementation code. But it’s quite possible to assign multiple filters to the Response.Filter property. So the following actually works to both compress the output and apply the transformed content: WebUtils.GZipEncodePage(); ResponseFilterStream filter = new ResponseFilterStream(Response.Filter); filter.TransformString += filter_TransformString; Response.Filter = filter; However the following does not work resulting in invalid content encoding errors: ResponseFilterStream filter = new ResponseFilterStream(Response.Filter); filter.TransformString += filter_TransformString; Response.Filter = filter; WebUtils.GZipEncodePage(); In other words multiple Response filters can work together but it depends entirely on the implementation whether they can be chained or in which order they can be chained. In this case running the GZip/Deflate stream filters apparently relies on the original content length of the output and chokes when the content is modified. But if attaching the compression first it works fine as unintuitive as that may seem. Resources Download example code Capture Output from ASP.NET Pages © Rick Strahl, West Wind Technologies, 2005-2010Posted in ASP.NET  

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