Java IoT Authors: Liz McMillan, Kevin Benedict, Elizabeth White, Pat Romanski, Jack Jachner

Related Topics: Java IoT, Recurring Revenue

Java IoT: Blog Feed Post

The Magic Sauce for Multi-Browser-Tab Support in JDeveloper ADF Apps

PageFlowScope with Unbounded Task Flows

Within JDev 11g+ experienced ADF programmers will be familiar with PageFlowScope beans used by tasks flows, in particular Bounded Task Flows (BTFs) where they provide the equivalent of session scope for variables for the life of the BTF for a specific user session. Indeed the Oracle documentation says the following about PageFlowScope beans:

Choose this scope if you want the managed bean to be accessible across the activities within a task flow. A managed bean that has a pageFlow scope shares state with pages from the task flow that access it. A managed bean that has a pageFlow scope exists for the life span of the task flow

Source: Oracle Fusion Dev Guide 11.2.1 Section 18.2.4 What You May Need to Know About Memory Scope for Task Flows

Given we know BTFs have a distinct beginning and end for each user session, a "life span" as such, and conversely Unbounded Task Flows (UTFs) live for the life of the application which is nearly forever, it would appear that PageFlowScope beans only apply to BTFs. However PageFlowScope beans provide some magic sauce with UTFs that shouldn't be ignored. Before we can have a look at this magic sauce we need to cover some background on modern browsers.

Multi-tab browsers and the challenge for web applications
Readers will be familiar that over the last several years browsers have increased in sophistication, providing users with more and more features. One such feature is that of tabs, more commonly referred to as multi-tab browsing. Back in the dim dark ages of the Internet (circa 2005?) if users wanted to surf more than one website at a time they needed to open multiple instances of their browser. Typically each browser instance took out a single connection and server-side session (assuming a stateful application) with whichever server they were visiting. If the user had multiple instances open to the same website this resulted in the same amount of connections and sessions.

At some point in time web browsers introduced the support for tabs, allowing within the one browser instance the user to surf multiple websites in separate tabs. I'll take a guess and say the browser authors when introducing this feature had a careful think about how users visit websites, and they realized users when searching for information on websites might spawn several tabs all visiting the same website but each tab viewing different pages within that single website.

So browsers introduced a feature set to give users the ability to search for information even faster, yet the browser vendors also recognized an issue. Potentially users were now relatively free to spawn lots of tabs (and if you're like some users you keep on spawning tabs, never closing any, until you shut down the browser). If the old regime of a connection per tab was followed at the client (browser) side, and a session per connection at the server (website) side, computing resources would be strained.

How to fix? Simple really, per website on the browser side, regardless the number of tabs open to a website via a browser, it should share the connections across the tabs. Result? Instant resource saving on the client. In turn on the server side as there isn't any default way to identify the different tabs as their separate requests hit the server through the same connection, the server too need only store 1 session.

Today from the users' perspective (at least the tech savvy users) multi-browser tabs is an expected feature and one when not available for whatever reason causes frustration either with the browser or the website they are using. This implies any web application we build really needs to support (or at least not hinder) this functionality.

What's this got to do with ADF?
The question is probably rhetorical for readers at this point, but what's this got to with ADF?

Traditionally JavaServer Faces (JSF) programmers and ADF programmers have been taught if you want to maintain state (variables) for the life of a user's session you put it in a SessionScope bean. Examples of such variables include the time the user first accessed the system, the customer ID of the current customer that the user is working with on the phone, or the items in a shopping cart. Definitely these should go in SessionScope.

Or should they?

With modern browsers what should happen with these variables when the user spawns two tabs to our application sharing the same connection/session? Looking at our previous examples it's easy to agree the time the user first accessed the system would be one and the same across both tabs. But what about our other examples?

For our customer ID example, reasonably in some applications you might want two different tabs to show two different pages for information on the same customer, so SessionScope seems reasonable enough. But alternatively imagine you're a call centre operator, taking a call from one customer while finishing recording data about the previous customer. It would be mighty handy to have two browser tabs to do this. As a result the separate tabs really require their own SessionScope customer ID. How to do that?

The question gets murkier when considering shopping carts. For an Amazon user having two separate carts on two separate browser tabs would seem undesirable. But let's take another call centre example where an operator is taking a phone call from a customer wanting to place two separate orders. Things get tricky if the customer is moving items between the orders, so different tabs supporting different orders could be desirable. Again the vanilla SessionScope bean won't solve this.

So we can see sometimes depending on the needs of the application, we need to provision session state for separate browser tabs. At the moment JSF1.X/2.0 has no inbuilt solution for this problem (there's been much discussion about including a new ConversationScope bean in the past), but as you can probably guess a PageFlowScope at the UTF level in ADF solves this problem. For every browser tab opening a page in the UTF that references a managed PageFlowScope bean a separate instance of the bean will be created.

The hint of the secret life of the PageFlowScope is revealed in Section 5.7 Passing Values Between Pages of the JDev Web Guide 11.1.2 where it states:

The ADF Faces pageFlowScope scope makes it easier to pass values from one page to another, thus enabling you to develop master-detail pages more easily. Values added to the pageFlowScope scope automatically continue to be available as the user navigates from one page to another, even if you use a redirect directive. But unlike session scope, these values are visible only in the current page flow or process. If the user opens a new window and starts navigating, that series of windows will have its own process. Values stored in each window remain independent.

Specifically note the last 2 sentences.

How does ADF technically solve identifying the separate tabs?

Earlier on we mentioned from the server's point of view, because multi-browser tabs share the same connection with the server, by default the server has no inherit mechanism to differentiate the separate browser tabs and therefore no mechanism to know when to spawn separate PageFlowScope beans. So how does ADF actually technically solve identifying the separate tabs?

Imagine you've created an ADF application to lodge infringements. Some infringements take seconds to fill out and complete, others take time to gather the data, requiring multiple tabs to enter more than one infringement at a time.

For such an ADF application we could serve the service via a link on our portal such as:


In this case ticket represents a JSPX file in our UTF of our application.

On accessing the URL for the first time regular ADF users will know the server in responding with the required page will also replace the URL with something like the following:


This parameter and its value is also buried in the HTML source to be used on the next request. Also inside the page source is a form parameter Adf-Window-Id with a unique value given by the server.

When the page is submitted along with the hidden _adf.ctrl-state and Adf-Window-Id parameter gained from the previous server response, this gives ADF a mechanism for tracking the current session and current page instance.

(Side note: Behind the scenes the server is smart enough to check the session parameters against the previous known connection/session to stop intruders impersonating another user's session ... you can test this by intercepting the next request before it goes out and changing the _adf.ctrl-state parameter before it hits the server. ADF will complain displaying the following error message "ADFC-12000: State ID in request is invalid for the current session.")

If the server receives another request for the same "naked" URL from the same connection/session, ADF simply assumes a new tab instance, spawns a separate PageFlowScope bean instance, and returns separate _adf.ctrl-state and Adf-Window-Id values in the response. Any subsequent requests to the server from separate multiple tabs for the same user connection are therefore easily separated and the correct PageFlowScope bean instance used.

Alternatively if the user tries to trick the server by copying the URL from another tab with the _adf.ctrl-state variable in the URL, but obviously missing a payload containing the _adf.ctrl-state form parameter and the Adf-Window-Id parameter, again ADF is smart enough to detect this as a new browser tab and spawns a new PageFlowScope bean. This piece of logic is important because it's possible for users to bookmark the current page's URL with the URL parameter, and attempt to come back to it after a spawning a new tab. As such we wouldn't want ADF to be tricked by this simple common use case into thinking the user is in the same original tab when in fact they're launching the application from an old bookmark.

Finally it should be noted if the user session times out or logs out, the PageFlowScope bean will fall out of scope and any reference to the PageFlowScope there after will result in new instance of the bean created.


The following link provides a small demo application from JDev 11.1.2. To set this application up you need to:

a) unzip it and open it in JDev
b) in your integrated WLS server create a user account which you will use to log in to the application

The application is comprised of 4 pages:

a) an unauthenticated Splash page to start the application
b) 2 separate authenticated pages named FirstPage and SecondPage that will demonstrate the bean scopes during an authenticated session
c) an unauthenticated ExitPage which will be called when the user logs out of SecondPage

From here run the Splash.jsf page. Your browser will eventually open with the following URL:


Select the Go First Page button, at the login enter your credentials, upon which you'll see First Page:

The two fields have default values gathered from two separate beans, one a SessionScope bean and the other a PageFlowScope bean. Note in the JDev log window you'll see log entries from the constructors of both beans, implying they were just instantiated to show the values on the page, and thus why the default values are shown.

Selecting the Go Second Page button takes us to the Second Page where we have the option to change the values:

As example lets change the value for the SessionScope to Alpha and the PageFlowScope value to Beta:

On returning to the first page through the associated button we see that Alpha and Beta values have been successfully carried across requests

Now open a new browser tab to original Splash page using the following URL:


Diagrammatically to show this, what I've done in the following set of pictures is put the original tab to the left of the image, and the new tab to the right of the image so I could show both tabs at the same time. As such we now have:

In the second tab if we then select the Go First Page button we bypass the login screen automatically as the user is already logged in, and we arrive on the SecondPage as follows:

In the JDev log window we see a new instance of the PageFlowScope bean has been created, but not the SessionScope bean. This backs up what is shown in the new second tab because we can see that the SessionScope value is shared across both tabs, but the PageFlowScope value isn't and we've reverted to the default value (provided through the new PageFlowScope instance).

From here in the second tab we can navigate to the Second Page and update the values of the SessionScope and PageFlowScope beans to Charlie and Delta respectively:

In the second tab if we then return to the FirstPage we see that it maintains the Charlie and Delta values:

...and more importantly in the first tab if we then navigate to the Second Page we see:

In this picture we can see that the SessionScope Charlie value has been shared across both tabs, but the first tab has retained it's original Beta values for it's PageFlowScope bean, showing that the PageFlowScopes are indeed separate across browser tabs.

To conclude the examples, if in the first tab we select the Logout button we automatically move to the ExitPage and we see:

This shows both the SessionScope and PageFlowScope bean resetting back to the original values. The JDev log window also logs the constructor calls of both beans verifying that the old beans have been completed and 2 new instances created.

Finally if we return to the second tab that is still sitting on the First Page, any action results in ADF throwing an exception "java.lang.IllegalStateException: No window for windowId:w2". To be honest I expected an error here because the user behind the scenes has logged out, but this error message looks less than useful. Presumably we need to take care of this specific error in some manner, probably with a task flow Exception handler, but is beyond the scope of this post.

Not all things are born equal - final note on SessionScope vs PageFlowScope

Don't get confused on the use of SessionScope and PageFlowScope beans. Not everything you would have traditionally put in SessionScope need now go in a UTF PageFlowScope bean. How many frequent flyer miles the user has left, the user's preferences and their birthday are good candidates for SessionScope. But if across tabs you will allow the user to test separate values for projecting sales figures, a counter for the numbers of steps completed in submitting separate expense reports or even the tiles placed in a game of tic tac toe, PageFlowScope will be more appropriate.

Read the original blog entry...

More Stories By Chris Muir

Chris Muir, an Oracle ACE Director, senior developer and trainer, and frequent blogger at http://one-size-doesnt-fit-all.blogspot.com, has been hacking away as an Oracle consultant with Australia's SAGE Computing Services for too many years. Taking a pragmatic approach to all things Oracle, Chris has more recently earned battle scars with JDeveloper, Apex, OID and web services, and has some very old war-wounds from a dark and dim past with Forms, Reports and even Designer 100% generation. He is a frequent presenter and contributor to the local Australian Oracle User Group scene, as well as a contributor to international user group magazines such as the IOUG and UKOUG.

@ThingsExpo Stories
There is only one world-class Cloud event on earth, and that is Cloud Expo – which returns to Silicon Valley for the 21st Cloud Expo at the Santa Clara Convention Center, October 31 - November 2, 2017. Every Global 2000 enterprise in the world is now integrating cloud computing in some form into its IT development and operations. Midsize and small businesses are also migrating to the cloud in increasing numbers. Companies are each developing their unique mix of cloud technologies and service...
WebRTC is great technology to build your own communication tools. It will be even more exciting experience it with advanced devices, such as a 360 Camera, 360 microphone, and a depth sensor camera. In his session at @ThingsExpo, Masashi Ganeko, a manager at INFOCOM Corporation, will introduce two experimental projects from his team and what they learned from them. "Shotoku Tamago" uses the robot audition software HARK to track speakers in 360 video of a remote party. "Virtual Teleport" uses a...
Internet of @ThingsExpo, taking place October 31 - November 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA, is co-located with 21st Cloud Expo and will feature technical sessions from a rock star conference faculty and the leading industry players in the world. The Internet of Things (IoT) is the most profound change in personal and enterprise IT since the creation of the Worldwide Web more than 20 years ago. All major researchers estimate there will be tens of billions devic...
Recently, IoT seems emerging as a solution vehicle for data analytics on real-world scenarios from setting a room temperature setting to predicting a component failure of an aircraft. Compared with developing an application or deploying a cloud service, is an IoT solution unique? If so, how? How does a typical IoT solution architecture consist? And what are the essential components and how are they relevant to each other? How does the security play out? What are the best practices in formulating...
In his session at @ThingsExpo, Arvind Radhakrishnen discussed how IoT offers new business models in banking and financial services organizations with the capability to revolutionize products, payments, channels, business processes and asset management built on strong architectural foundation. The following topics were covered: How IoT stands to impact various business parameters including customer experience, cost and risk management within BFS organizations.
An increasing number of companies are creating products that combine data with analytical capabilities. Running interactive queries on Big Data requires complex architectures to store and query data effectively, typically involving data streams, an choosing efficient file format/database and multiple independent systems that are tied together through custom-engineered pipelines. In his session at @BigDataExpo at @ThingsExpo, Tomer Levi, a senior software engineer at Intel’s Advanced Analytics ...
SYS-CON Events announced today that Elastifile will exhibit at SYS-CON's 21st International Cloud Expo®, which will take place on Oct 31 - Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. Elastifile Cloud File System (ECFS) is software-defined data infrastructure designed for seamless and efficient management of dynamic workloads across heterogeneous environments. Elastifile provides the architecture needed to optimize your hybrid cloud environment, by facilitating efficient...
SYS-CON Events announced today that Golden Gate University will exhibit at SYS-CON's 21st International Cloud Expo®, which will take place on Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. Since 1901, non-profit Golden Gate University (GGU) has been helping adults achieve their professional goals by providing high quality, practice-based undergraduate and graduate educational programs in law, taxation, business and related professions. Many of its courses are taug...
"We provide IoT solutions. We provide the most compatible solutions for many applications. Our solutions are industry agnostic and also protocol agnostic," explained Richard Han, Head of Sales and Marketing and Engineering at Systena America, in this SYS-CON.tv interview at @ThingsExpo, held June 6-8, 2017, at the Javits Center in New York City, NY.
SYS-CON Events announced today that DXWorldExpo has been named “Global Sponsor” of SYS-CON's 21st International Cloud Expo, which will take place on Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. Digital Transformation is the key issue driving the global enterprise IT business. Digital Transformation is most prominent among Global 2000 enterprises and government institutions.
21st International Cloud Expo, taking place October 31 - November 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA, will feature technical sessions from a rock star conference faculty and the leading industry players in the world. Cloud computing is now being embraced by a majority of enterprises of all sizes. Yesterday's debate about public vs. private has transformed into the reality of hybrid cloud: a recent survey shows that 74% of enterprises have a hybrid cloud strategy. Me...
Recently, WebRTC has a lot of eyes from market. The use cases of WebRTC are expanding - video chat, online education, online health care etc. Not only for human-to-human communication, but also IoT use cases such as machine to human use cases can be seen recently. One of the typical use-case is remote camera monitoring. With WebRTC, people can have interoperability and flexibility for deploying monitoring service. However, the benefit of WebRTC for IoT is not only its convenience and interopera...
SYS-CON Events announced today that Secure Channels, a cybersecurity firm, will exhibit at SYS-CON's 21st International Cloud Expo®, which will take place on Oct 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. Secure Channels, Inc. offers several products and solutions to its many clients, helping them protect critical data from being compromised and access to computer networks from the unauthorized. The company develops comprehensive data encryption security strategie...
From 2013, NTT Communications has been providing cPaaS service, SkyWay. Its customer’s expectations for leveraging WebRTC technology are not only typical real-time communication use cases such as Web conference, remote education, but also IoT use cases such as remote camera monitoring, smart-glass, and robotic. Because of this, NTT Communications has numerous IoT business use-cases that its customers are developing on top of PaaS. WebRTC will lead IoT businesses to be more innovative and address...
When shopping for a new data processing platform for IoT solutions, many development teams want to be able to test-drive options before making a choice. Yet when evaluating an IoT solution, it’s simply not feasible to do so at scale with physical devices. Building a sensor simulator is the next best choice; however, generating a realistic simulation at very high TPS with ease of configurability is a formidable challenge. When dealing with multiple application or transport protocols, you would be...
SYS-CON Events announced today that App2Cloud will exhibit at SYS-CON's 21st International Cloud Expo®, which will take place on Oct. 31 – Nov 2, 2017, at the Santa Clara Convention Center in Santa Clara, CA. App2Cloud is an online Platform, specializing in migrating legacy applications to any Cloud Providers (AWS, Azure, Google Cloud).
IoT is at the core or many Digital Transformation initiatives with the goal of re-inventing a company's business model. We all agree that collecting relevant IoT data will result in massive amounts of data needing to be stored. However, with the rapid development of IoT devices and ongoing business model transformation, we are not able to predict the volume and growth of IoT data. And with the lack of IoT history, traditional methods of IT and infrastructure planning based on the past do not app...
Internet-of-Things discussions can end up either going down the consumer gadget rabbit hole or focused on the sort of data logging that industrial manufacturers have been doing forever. However, in fact, companies today are already using IoT data both to optimize their operational technology and to improve the experience of customer interactions in novel ways. In his session at @ThingsExpo, Gordon Haff, Red Hat Technology Evangelist, shared examples from a wide range of industries – including en...
To get the most out of their data, successful companies are not focusing on queries and data lakes, they are actively integrating analytics into their operations with a data-first application development approach. Real-time adjustments to improve revenues, reduce costs, or mitigate risk rely on applications that minimize latency on a variety of data sources. Jack Norris reviews best practices to show how companies develop, deploy, and dynamically update these applications and how this data-first...
Intelligent Automation is now one of the key business imperatives for CIOs and CISOs impacting all areas of business today. In his session at 21st Cloud Expo, Brian Boeggeman, VP Alliances & Partnerships at Ayehu, will talk about how business value is created and delivered through intelligent automation to today’s enterprises. The open ecosystem platform approach toward Intelligent Automation that Ayehu delivers to the market is core to enabling the creation of the self-driving enterprise.