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• Should business services cross bounded contexts?

  - by Paul T Davies

  Firstly, I am following the convention that a bounded context is synonymous to a department, or possibly one department has 1 to many bounded contexts. We have a client consultancy department that has a Documentation Service. Documents are stored in the Document Store Service (which is where all documents in the company are stored - it is a utility service), and the Documentation Service stores information about that document (a business service). As it was designed for the client consultancy, it is information relevant to them. Now health and safety need somewhere to store information about a document. This is different information to client consultancy, but I have been instructed to extend the existing service to account for this extra information. I feel this service is now crossing a bounded context. My worry is that all departments will eventually store there information in here and the service will become bloated, trying to be all things to all departments. Each document record will only store a subset of the information because it will only belong to one department. It will get worse when different departments want to store the same information but refer to it in a diferent ways, or when two departments want to store different information that they refer to in the same way. In my understanding, this is exactly the reason for bounded contexts. I feel each department should have it's own business service for information about a document, but use the same utility service to actually store the document. What would be the correct approach?

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• How do you formulate the Domain Model in Domain Driven Design properly (Bounded Contexts, Domains)?

  - by lko

  Say you have a few applications which deal with a few different Core Domains. The examples are made up and it's hard to put a real example with meaningful data together (concisely). In Domain Driven Design (DDD) when you start looking at Bounded Contexts and Domains/Sub Domains, it says that a Bounded Context is a "phase" in a lifecycle. An example of Context here would be within an ecommerce system. Although you could model this as a single system, it would also warrant splitting into separate Contexts. Each of these areas within the application have their own Ubiquitous Language, their own Model, and a way to talk to other Bounded Contexts to obtain the information they need. The Core, Sub, and Generic Domains are the area of expertise and can be numerous in complex applications. Say there is a long process dealing with an Entity for example a Book in a core domain. Now looking at the Bounded Contexts there can be a number of phases in the books life-cycle. Say outline, creation, correction, publish, sale phases. Now imagine a second core domain, perhaps a store domain. The publisher has its own branch of stores to sell books. The store can have a number of Bounded Contexts (life-cycle phases) for example a "Stock" or "Inventory" context. In the first domain there is probably a Book database table with basically just an ID to track the different book Entities in the different life-cycles. Now suppose you have 10+ supporting domains e.g. Users, Catalogs, Inventory, .. (hard to think of relevant examples). For example a DomainModel for the Book Outline phase, the Creation phase, Correction phase, Publish phase, Sale phase. Then for the Store core domain it probably has a number of life-cycle phases. public class BookId : Entity { public long Id { get; set; } } In the creation phase (Bounded Context) the book could be a simple class. public class Book : BookId { public string Title { get; set; } public List<string> Chapters { get; set; } //... } Whereas in the publish phase (Bounded Context) it would have all the text, release date etc. public class Book : BookId { public DateTime ReleaseDate { get; set; } //... } The immediate benefit I can see in separating by "life-cycle phase" is that it's a great way to separate business logic so there aren't mammoth all-encompassing Entities nor Domain Services. A problem I have is figuring out how to concretely define the rules to the physical layout of the Domain Model. A. Does the Domain Model get "modeled" so there are as many bounded contexts (separate projects etc.) as there are life-cycle phases across the core domains in a complex application? Edit: Answer to A. Yes, according to the answer by Alexey Zimarev there should be an entire "Domain" for each bounded context. B. Is the Domain Model typically arranged by Bounded Contexts (or Domains, or both)? Edit: Answer to B. Each Bounded Context should have its own complete "Domain" (Service/Entities/VO's/Repositories) C. Does it mean there can easily be 10's of "segregated" Domain Models and multiple projects can use it (the Entities/Value Objects)? Edit: Answer to C. There is a complete "Domain" for each Bounded Context and the Domain Model (Entity/VO layer/project) isn't "used" by the other Bounded Contexts directly, only via chosen paths (i.e. via Domain Events). The part that I am trying to figure out is how the Domain Model is actually implemented once you start to figure out your Bounded Contexts and Core/Sub Domains, particularly in complex applications. The goal is to establish the definitions which can help to separate Entities between the Bounded Contexts and Domains.

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• Converting a bounded knapsack problem to 0/1 knapsack problem

  - by Ants

  I ran across a problem where goal was to use dynamic programming (instead of other approaches). There is a distance to be spanned, and a set of cables of different lengths. What is the minimum number of cables needed to span the distance exactly? To me this looked like a knapsack problem, but since there could be multiples of a particular length, it was a bounded knapsack problem, rather than a 0/1 knapsack problem. (Treat the value of each item to be its weight.) Taking the naive approach (and not caring about the expansion of the search space), the method I used to convert the bounded knapsack problem into a 0/1 knapsack problem, was simply break up the multiples into singles and apply the well-known dynamic programming algorithm. Unfortunately, this leads to sub-optimal results. For example, given cables: 1 x 10ft, 1 x 7ft, 1 x 6ft, 5 x 3ft, 6 x 2ft, 7 x 1ft If the target span is 13ft, the DP algorithm picks 7+6 to span the distance. A greedy algorithm would have picked 10+3, but it's a tie for minimum number of cables. The problem arises, when trying to span 15ft. The DP algorithm ended up picking 6+3+3+3 to get 4 cables, while the greedy algorithm correctly picks 10+3+2 for only 3 cables. Anyway, doing some light scanning of converting bounded to 0/1, it seems like the well-known approach to convert multiple items to { p, 2p, 4p ... }. My question is how does this conversion work if p+2p+4p does not add up to the number of multiple items. For example: I have 5 3ft cables. I can't very well add { 3, 2x3, 4x3 } because 3+2x3+4x3 5x3. Should I add { 3, 4x3 } instead? [I'm currently trying to grok the "Oregon Trail Knapsack Problem" paper, but it currently looks like the approach used there is not dynamic programming.]

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• PTLQueue : a scalable bounded-capacity MPMC queue

  - by Dave

  Title: Fast concurrent MPMC queue -- I've used the following concurrent queue algorithm enough that it warrants a blog entry. I'll sketch out the design of a fast and scalable multiple-producer multiple-consumer (MPSC) concurrent queue called PTLQueue. The queue has bounded capacity and is implemented via a circular array. Bounded capacity can be a useful property if there's a mismatch between producer rates and consumer rates where an unbounded queue might otherwise result in excessive memory consumption by virtue of the container nodes that -- in some queue implementations -- are used to hold values. A bounded-capacity queue can provide flow control between components. Beware, however, that bounded collections can also result in resource deadlock if abused. The put() and take() operators are partial and wait for the collection to become non-full or non-empty, respectively. Put() and take() do not allocate memory, and are not vulnerable to the ABA pathologies. The PTLQueue algorithm can be implemented equally well in C/C++ and Java. Partial operators are often more convenient than total methods. In many use cases if the preconditions aren't met, there's nothing else useful the thread can do, so it may as well wait via a partial method. An exception is in the case of work-stealing queues where a thief might scan a set of queues from which it could potentially steal. Total methods return ASAP with a success-failure indication. (It's tempting to describe a queue or API as blocking or non-blocking instead of partial or total, but non-blocking is already an overloaded concurrency term. Perhaps waiting/non-waiting or patient/impatient might be better terms). It's also trivial to construct partial operators by busy-waiting via total operators, but such constructs may be less efficient than an operator explicitly and intentionally designed to wait. A PTLQueue instance contains an array of slots, where each slot has volatile Turn and MailBox fields. The array has power-of-two length allowing mod/div operations to be replaced by masking. We assume sensible padding and alignment to reduce the impact of false sharing. (On x86 I recommend 128-byte alignment and padding because of the adjacent-sector prefetch facility). Each queue also has PutCursor and TakeCursor cursor variables, each of which should be sequestered as the sole occupant of a cache line or sector. You can opt to use 64-bit integers if concerned about wrap-around aliasing in the cursor variables. Put(null) is considered illegal, but the caller or implementation can easily check for and convert null to a distinguished non-null proxy value if null happens to be a value you'd like to pass. Take() will accordingly convert the proxy value back to null. An advantage of PTLQueue is that you can use atomic fetch-and-increment for the partial methods. We initialize each slot at index I with (Turn=I, MailBox=null). Both cursors are initially 0. All shared variables are considered "volatile" and atomics such as CAS and AtomicFetchAndIncrement are presumed to have bidirectional fence semantics. Finally T is the templated type. I've sketched out a total tryTake() method below that allows the caller to poll the queue. tryPut() has an analogous construction. Zebra stripping : alternating row colors for nice-looking code listings. See also google code "prettify" : https://code.google.com/p/google-code-prettify/ Prettify is a javascript module that yields the HTML/CSS/JS equivalent of pretty-print. -- pre:nth-child(odd) { background-color:#ff0000; } pre:nth-child(even) { background-color:#0000ff; } border-left: 11px solid #ccc; margin: 1.7em 0 1.7em 0.3em; background-color:#BFB; font-size:12px; line-height:65%; " // PTLQueue : Put(v) : // producer : partial method - waits as necessary assert v != null assert Mask = 1 && (Mask & (Mask+1)) == 0 // Document invariants // doorway step // Obtain a sequence number -- ticket // As a practical concern the ticket value is temporally unique // The ticket also identifies and selects a slot auto tkt = AtomicFetchIncrement (&PutCursor, 1) slot * s = &Slots[tkt & Mask] // waiting phase : // wait for slot's generation to match the tkt value assigned to this put() invocation. // The "generation" is implicitly encoded as the upper bits in the cursor // above those used to specify the index : tkt div (Mask+1) // The generation serves as an epoch number to identify a cohort of threads // accessing disjoint slots while s-Turn != tkt : Pause assert s-MailBox == null s-MailBox = v // deposit and pass message Take() : // consumer : partial method - waits as necessary auto tkt = AtomicFetchIncrement (&TakeCursor,1) slot * s = &Slots[tkt & Mask] // 2-stage waiting : // First wait for turn for our generation // Acquire exclusive "take" access to slot's MailBox field // Then wait for the slot to become occupied while s-Turn != tkt : Pause // Concurrency in this section of code is now reduced to just 1 producer thread // vs 1 consumer thread. // For a given queue and slot, there will be most one Take() operation running // in this section. // Consumer waits for producer to arrive and make slot non-empty // Extract message; clear mailbox; advance Turn indicator // We have an obvious happens-before relation : // Put(m) happens-before corresponding Take() that returns that same "m" for T v = s-MailBox if v != null : s-MailBox = null ST-ST barrier s-Turn = tkt + Mask + 1 // unlock slot to admit next producer and consumer return v Pause tryTake() : // total method - returns ASAP with failure indication for auto tkt = TakeCursor slot * s = &Slots[tkt & Mask] if s-Turn != tkt : return null T v = s-MailBox // presumptive return value if v == null : return null // ratify tkt and v values and commit by advancing cursor if CAS (&TakeCursor, tkt, tkt+1) != tkt : continue s-MailBox = null ST-ST barrier s-Turn = tkt + Mask + 1 return v The basic idea derives from the Partitioned Ticket Lock "PTL" (US20120240126-A1) and the MultiLane Concurrent Bag (US8689237). The latter is essentially a circular ring-buffer where the elements themselves are queues or concurrent collections. You can think of the PTLQueue as a partitioned ticket lock "PTL" augmented to pass values from lock to unlock via the slots. Alternatively, you could conceptualize of PTLQueue as a degenerate MultiLane bag where each slot or "lane" consists of a simple single-word MailBox instead of a general queue. Each lane in PTLQueue also has a private Turn field which acts like the Turn (Grant) variables found in PTL. Turn enforces strict FIFO ordering and restricts concurrency on the slot mailbox field to at most one simultaneous put() and take() operation. PTL uses a single "ticket" variable and per-slot Turn (grant) fields while MultiLane has distinct PutCursor and TakeCursor cursors and abstract per-slot sub-queues. Both PTL and MultiLane advance their cursor and ticket variables with atomic fetch-and-increment. PTLQueue borrows from both PTL and MultiLane and has distinct put and take cursors and per-slot Turn fields. Instead of a per-slot queues, PTLQueue uses a simple single-word MailBox field. PutCursor and TakeCursor act like a pair of ticket locks, conferring "put" and "take" access to a given slot. PutCursor, for instance, assigns an incoming put() request to a slot and serves as a PTL "Ticket" to acquire "put" permission to that slot's MailBox field. To better explain the operation of PTLQueue we deconstruct the operation of put() and take() as follows. Put() first increments PutCursor obtaining a new unique ticket. That ticket value also identifies a slot. Put() next waits for that slot's Turn field to match that ticket value. This is tantamount to using a PTL to acquire "put" permission on the slot's MailBox field. Finally, having obtained exclusive "put" permission on the slot, put() stores the message value into the slot's MailBox. Take() similarly advances TakeCursor, identifying a slot, and then acquires and secures "take" permission on a slot by waiting for Turn. Take() then waits for the slot's MailBox to become non-empty, extracts the message, and clears MailBox. Finally, take() advances the slot's Turn field, which releases both "put" and "take" access to the slot's MailBox. Note the asymmetry : put() acquires "put" access to the slot, but take() releases that lock. At any given time, for a given slot in a PTLQueue, at most one thread has "put" access and at most one thread has "take" access. This restricts concurrency from general MPMC to 1-vs-1. We have 2 ticket locks -- one for put() and one for take() -- each with its own "ticket" variable in the form of the corresponding cursor, but they share a single "Grant" egress variable in the form of the slot's Turn variable. Advancing the PutCursor, for instance, serves two purposes. First, we obtain a unique ticket which identifies a slot. Second, incrementing the cursor is the doorway protocol step to acquire the per-slot mutual exclusion "put" lock. The cursors and operations to increment those cursors serve double-duty : slot-selection and ticket assignment for locking the slot's MailBox field. At any given time a slot MailBox field can be in one of the following states: empty with no pending operations -- neutral state; empty with one or more waiting take() operations pending -- deficit; occupied with no pending operations; occupied with one or more waiting put() operations -- surplus; empty with a pending put() or pending put() and take() operations -- transitional; or occupied with a pending take() or pending put() and take() operations -- transitional. The partial put() and take() operators can be implemented with an atomic fetch-and-increment operation, which may confer a performance advantage over a CAS-based loop. In addition we have independent PutCursor and TakeCursor cursors. Critically, a put() operation modifies PutCursor but does not access the TakeCursor and a take() operation modifies the TakeCursor cursor but does not access the PutCursor. This acts to reduce coherence traffic relative to some other queue designs. It's worth noting that slow threads or obstruction in one slot (or "lane") does not impede or obstruct operations in other slots -- this gives us some degree of obstruction isolation. PTLQueue is not lock-free, however. The implementation above is expressed with polite busy-waiting (Pause) but it's trivial to implement per-slot parking and unparking to deschedule waiting threads. It's also easy to convert the queue to a more general deque by replacing the PutCursor and TakeCursor cursors with Left/Front and Right/Back cursors that can move either direction. Specifically, to push and pop from the "left" side of the deque we would decrement and increment the Left cursor, respectively, and to push and pop from the "right" side of the deque we would increment and decrement the Right cursor, respectively. We used a variation of PTLQueue for message passing in our recent OPODIS 2013 paper. ul { list-style:none; padding-left:0; padding:0; margin:0; margin-left:0; } ul#myTagID { padding: 0px; margin: 0px; list-style:none; margin-left:0;} -- -- There's quite a bit of related literature in this area. I'll call out a few relevant references: Wilson's NYU Courant Institute UltraComputer dissertation from 1988 is classic and the canonical starting point : Operating System Data Structures for Shared-Memory MIMD Machines with Fetch-and-Add. Regarding provenance and priority, I think PTLQueue or queues effectively equivalent to PTLQueue have been independently rediscovered a number of times. See CB-Queue and BNPBV, below, for instance. But Wilson's dissertation anticipates the basic idea and seems to predate all the others. Gottlieb et al : Basic Techniques for the Efficient Coordination of Very Large Numbers of Cooperating Sequential Processors Orozco et al : CB-Queue in Toward high-throughput algorithms on many-core architectures which appeared in TACO 2012. Meneghin et al : BNPVB family in Performance evaluation of inter-thread communication mechanisms on multicore/multithreaded architecture Dmitry Vyukov : bounded MPMC queue (highly recommended) Alex Otenko : US8607249 (highly related). John Mellor-Crummey : Concurrent queues: Practical fetch-and-phi algorithms. Technical Report 229, Department of Computer Science, University of Rochester Thomasson : FIFO Distributed Bakery Algorithm (very similar to PTLQueue). Scott and Scherer : Dual Data Structures I'll propose an optimization left as an exercise for the reader. Say we wanted to reduce memory usage by eliminating inter-slot padding. Such padding is usually "dark" memory and otherwise unused and wasted. But eliminating the padding leaves us at risk of increased false sharing. Furthermore lets say it was usually the case that the PutCursor and TakeCursor were numerically close to each other. (That's true in some use cases). We might still reduce false sharing by incrementing the cursors by some value other than 1 that is not trivially small and is coprime with the number of slots. Alternatively, we might increment the cursor by one and mask as usual, resulting in a logical index. We then use that logical index value to index into a permutation table, yielding an effective index for use in the slot array. The permutation table would be constructed so that nearby logical indices would map to more distant effective indices. (Open question: what should that permutation look like? Possibly some perversion of a Gray code or De Bruijn sequence might be suitable). As an aside, say we need to busy-wait for some condition as follows : "while C == 0 : Pause". Lets say that C is usually non-zero, so we typically don't wait. But when C happens to be 0 we'll have to spin for some period, possibly brief. We can arrange for the code to be more machine-friendly with respect to the branch predictors by transforming the loop into : "if C == 0 : for { Pause; if C != 0 : break; }". Critically, we want to restructure the loop so there's one branch that controls entry and another that controls loop exit. A concern is that your compiler or JIT might be clever enough to transform this back to "while C == 0 : Pause". You can sometimes avoid this by inserting a call to a some type of very cheap "opaque" method that the compiler can't elide or reorder. On Solaris, for instance, you could use :"if C == 0 : { gethrtime(); for { Pause; if C != 0 : break; }}". It's worth noting the obvious duality between locks and queues. If you have strict FIFO lock implementation with local spinning and succession by direct handoff such as MCS or CLH,then you can usually transform that lock into a queue. Hidden commentary and annotations - invisible : * And of course there's a well-known duality between queues and locks, but I'll leave that topic for another blog post. * Compare and contrast : PTLQ vs PTL and MultiLane * Equivalent : Turn; seq; sequence; pos; position; ticket * Put = Lock; Deposit Take = identify and reserve slot; wait; extract & clear; unlock * conceptualize : Distinct PutLock and TakeLock implemented as ticket lock or PTL Distinct arrival cursors but share per-slot "Turn" variable provides exclusive role-based access to slot's mailbox field put() acquires exclusive access to a slot for purposes of "deposit" assigns slot round-robin and then acquires deposit access rights/perms to that slot take() acquires exclusive access to slot for purposes of "withdrawal" assigns slot round-robin and then acquires withdrawal access rights/perms to that slot At any given time, only one thread can have withdrawal access to a slot at any given time, only one thread can have deposit access to a slot Permissible for T1 to have deposit access and T2 to simultaneously have withdrawal access * round-robin for the purposes of; role-based; access mode; access role mailslot; mailbox; allocate/assign/identify slot rights; permission; license; access permission; * PTL/Ticket hybrid Asymmetric usage ; owner oblivious lock-unlock pairing K-exclusion add Grant cursor pass message m from lock to unlock via Slots[] array Cursor performs 2 functions : + PTL ticket + Assigns request to slot in round-robin fashion Deconstruct protocol : explication put() : allocate slot in round-robin fashion acquire PTL for "put" access store message into slot associated with PTL index take() : Acquire PTL for "take" access // doorway step seq = fetchAdd (&Grant, 1) s = &Slots[seq & Mask] // waiting phase while s-Turn != seq : pause Extract : wait for s-mailbox to be full v = s-mailbox s-mailbox = null Release PTL for both "put" and "take" access s-Turn = seq + Mask + 1 * Slot round-robin assignment and lock "doorway" protocol leverage the same cursor and FetchAdd operation on that cursor FetchAdd (&Cursor,1) + round-robin slot assignment and dispersal + PTL/ticket lock "doorway" step waiting phase is via "Turn" field in slot * PTLQueue uses 2 cursors -- put and take. Acquire "put" access to slot via PTL-like lock Acquire "take" access to slot via PTL-like lock 2 locks : put and take -- at most one thread can access slot's mailbox Both locks use same "turn" field Like multilane : 2 cursors : put and take slot is simple 1-capacity mailbox instead of queue Borrow per-slot turn/grant from PTL Provides strict FIFO Lock slot : put-vs-put take-vs-take at most one put accesses slot at any one time at most one put accesses take at any one time reduction to 1-vs-1 instead of N-vs-M concurrency Per slot locks for put/take Release put/take by advancing turn * is instrumental in ... * P-V Semaphore vs lock vs K-exclusion * See also : FastQueues-excerpt.java dice-etc/queue-mpmc-bounded-blocking-circular-xadd/ * PTLQueue is the same as PTLQB - identical * Expedient return; ASAP; prompt; immediately * Lamport's Bakery algorithm : doorway step then waiting phase Threads arriving at doorway obtain a unique ticket number Threads enter in ticket order * In the terminology of Reed and Kanodia a ticket lock corresponds to the busy-wait implementation of a semaphore using an eventcount and a sequencer It can also be thought of as an optimization of Lamport's bakery lock was designed for fault-tolerance rather than performance Instead of spinning on the release counter, processors using a bakery lock repeatedly examine the tickets of their peers --

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• ADF Bounded Taskflow Activation

  - by Vijay Mohan

  hey guys, It's really been a while since I last blogged. Just came across a hard-to-debug scenario, so thought of sharing it for the benefit of ADF developers.I had a page fragment(jsff) wrapped inside a  bounded taskflow, for which the activation was conditional and was based on a requestScope property (be it a requestScope variable or a property coming from a requestScope bean). As soon as the taskflow activates and page renders the requestScope parameters life span ends. After that, when you raise an event inside the page (click of commandLink, moseHover, valueChange event etc) then for the first time the event gets fired but it fails to affect the change in the page, moreover, for the subsequent times the event itself doesn't get fired. Any guesses as to what could be the culprit..?I guess, I already gave the reason in the initial paragraph. For the first time when the event gets fired, the fwk sees that the page is already lying in inactivate state, so it fails to affect the change and for subsequent times it doesn't even fire the event because it already knew that the page/region is inactive. So, in such a scenario we must use either a pageFlowScope property or transientVO property which could exist till the page's life span.

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• Refresh bounded taskflows across regions using InputParameters

  - by raghu.yadav

  Usecase1 : Selecting record from table in left region reflects dependent detail form of same table in right region using InputParameters Here is the example given by Andre Example Three important crux to be known from above example. 1) create primary key attribute in pagedef of the table in region1 2) add inputparameter name in taskflow inputparameters of region2 3) bind primary key attribute from page definition to above inputparameters in main page where above 2 regions dropped. UseCase2 : Selecting record from location table in left region reflects corresponding department records from department table in right regions. 1) create bind variable on location id in departmentVO. 2) create inputparameter say LocationParam, with type Number, value as #{pageFlowScope.LocationParam} 3) assign LocationId param from pagedef to LocationParam in taskflow2 4) create ExecuteWithParam action in region2 pagedef and invoke the same on IfRefresh condition. during run time - steps executes in backwards (3,2,1)..i,e as user selects column in location table, it assigns location from pagedef to locationParam and then to PageFlowScope and from there to view criteria.

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• Refresh bounded taskflows across regions using Contextual Events

  - by raghu.yadav

  Usecases: 1) Data Change in left region inputText field reflect changes in right region using contextual event. example by Frank Nimphius :Value change event refresh across regions using Contextual Events 2) Select Tree node in left region reflects dependent detail form in right region using dynamic regions and Contextual Events. example by Frank Nimphius:Example6-RangeCtx.unzip More related examples: http://thepeninsulasedge.com/frank_nimphius/2008/02/07/adf-faces-rc-refreshing-a-table-ui-from-a-contextual-event/ http://www.oracle.com/technology/products/jdev/tips/fnimphius/generictreeselectionlistener/index.html http://www.oracle.com/technology/products/jdev/tips/fnimphius/syncheditformwithtree/index.html http://biemond.blogspot.com/2009/01/passing-adf-events-between-task-flow.html http://www.oracle.com/technology/products/jdev/tips/fnimphius/opentaskflowintab/index.html http://lucbors.blogspot.com/2010/03/adf-11g-contextual-event-framework.html http://thepeninsulasedge.com/blog/?cat=2 http://www.ora600.be/news/adf-contextual-events-11g-r1-ps1

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• get all geolocations from a polygon bounded region?

  - by soden

  get all geolocations from a polygon bounded region?

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• Filling up bounded form with information from another table while creating new record

  - by amir shadaab

  I have an excel sheet with information about each employee. I keep getting new updated spreadsheet every month. I have to create a database managing cases related to the employees. I have a database and the bounded form already created for the cases which also contain emp info fields. What I am trying to do is to only type in the emp id in the form and want the form to look up in the spreadsheet(which can be a table in the cases db) and populate other fields in the form and that information can go into the cases db. Can this be done?

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• Having Issue with Bounded Wildcards in Generic

  - by Sanjiv

  I am new to Java Generics, and I'm currently experimenting with Generic Coding....final goal is to convert old Non-Generic legacy code to generic one... I have defined two Classes with IS-A i.e. one is sub-class of other. public class Parent { private String name; public Parent(String name) { super(); this.name = name; } } public class Child extends Parent{ private String address; public Child(String name, String address) { super(name); this.address = address; } } Now, I am trying to create a list with bounded Wildcard. and getting Compiler Error. List<? extends Parent> myList = new ArrayList<Child>(); myList.add(new Parent("name")); // compiler-error myList.add(new Child("name", "address")); // compiler-error myList.add(new Child("name", "address")); // compiler-error Bit confused. please help me on whats wrong with this ?

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• Moving Javascript object with all bounded events to other variable

  - by Saif Bechan

  Let's say I have an anchor tag, with some events. <a id="clickme" href="/endpoint">clickme</a> <a id="clickme2" href="/endpoint2">clickme2</a> Let's use jquery for simplicity: $('#clickme').on('click', function(){.....}) I also have a variable: var myActiveVar = $('#clickme'); When I want to remove the element an every trace of it I can do this: myActiveVar.off().remove(); Here comes the problem, I want to reuse the variable. Something like this: var oldAcriveVar = myActiveVar; myActiveVar = $('#clickme2'); // Now I want to do some operations // both of the elements are still on // the page, when I'm done: oldActiveVar.off().remove(); Comeplete code: var myActiveVar = $('#clickme'); // Operate on myActiveVar var oldAcriveVar = myActiveVar; myActiveVar = $('#clickme2'); // Operate on myActiveVar which is // the new element. // Old element stays visible oldActiveVar.off().remove(); // Old element and all traces are gone Edit: Maybe the above code will work, but my problem goes beyond. I just gave a simplified example. I am using Backbone events that are bounded to object. They need to be removed when I am done with the object.

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• What would be a good opensource software for graphing circles, circular regions, and regions bounded by curves and/or arcs?

  - by Michael Dykes

  Hullo all. I have just started s job with Chegg, and my 1st assignment has me writign solutions for Stewart's Essential Calculus. I am dealing with the chapter on multiple integration, and need a good open-source software that I can easily use to draw regions (domains) that would require multiple integrals: i.e. circular regions, portions of circles, regions bounded by curves and/or arcs, and at some point 3D pictures. In most of these cases, I am not working with an exact equation or perhaps need to draw the region bounded by r (radius) between 1 and 2, and the angle theta bounded between pi/4 and 3 pi/4. I am not too terribly familiar with programs like Corel Draw, but the documents I have from this company suggest Corel Draw. So I think I am looking for an open-source free program like Corel Draw or something similar. Any additional suggestions would also be appreciated. I know I can do most, if not all of this using TikZ, but the learning curve is a bit steep, and at the moment I an on a time constraint. Thanks.

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• Finding minimum cut-sets between bounded subgraphs

  - by Tore

  If a game map is partitioned into subgraphs, how to minimize edges between subgraphs? I have a problem, Im trying to make A* searches through a grid based game like pacman or sokoban, but i need to find "enclosures". What do i mean by enclosures? subgraphs with as few cut edges as possible given a maximum size and minimum size for number of vertices for each subgraph that act as a soft constraints. Alternatively you could say i am looking to find bridges between subgraphs, but its generally the same problem. Given a game that looks like this, what i want to do is find enclosures so that i can properly find entrances to them and thus get a good heuristic for reaching vertices inside these enclosures. So what i want is to find these colored regions on any given map. My Motivation The reason for me bothering to do this and not just staying content with the performance of a simple manhattan distance heuristic is that an enclosure heuristic can give more optimal results and i would not have to actually do the A* to get some proper distance calculations and also for later adding competitive blocking of opponents within these enclosures when playing sokoban type games. Also the enclosure heuristic can be used for a minimax approach to finding goal vertices more properly. A possible solution to the problem is the Kernighan-Lin algorithm: function Kernighan-Lin(G(V,E)): determine a balanced initial partition of the nodes into sets A and B do A1 := A; B1 := B compute D values for all a in A1 and b in B1 for (i := 1 to |V|/2) find a[i] from A1 and b[i] from B1, such that g[i] = D[a[i]] + D[b[i]] - 2*c[a][b] is maximal move a[i] to B1 and b[i] to A1 remove a[i] and b[i] from further consideration in this pass update D values for the elements of A1 = A1 / a[i] and B1 = B1 / b[i] end for find k which maximizes g_max, the sum of g[1],...,g[k] if (g_max > 0) then Exchange a[1],a[2],...,a[k] with b[1],b[2],...,b[k] until (g_max <= 0) return G(V,E) My problem with this algorithm is its runtime at O(n^2 * lg(n)), i am thinking of limiting the nodes in A1 and B1 to the border of each subgraph to reduce the amount of work done. I also dont understand the c[a][b] cost in the algorithm, if a and b do not have an edge between them is the cost assumed to be 0 or infinity, or should i create an edge based on some heuristic. Do you know what c[a][b] is supposed to be when there is no edge between a and b? Do you think my problem is suitable to use a multi level problem? Why or why not? Do you have a good idea for how to reduce the work done with the kernighan-lin algorithm for my problem?

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• Get the current bounded object in a ListView's ItemTemplate

  - by Andreas Grech

  I want to be able to get the current bound object in the ItemTemplate of a ListView control. Here's an example of what I want to do: <asp:ListView ID="UserList" runat="server"> <LayoutTemplate> <asp:PlaceHolder ID="itemPlaceHolder" runat="server" /> </LayoutTemplate> <ItemTemplate> //How can I get the current bound object in here? </ItemTemplate> </asp:ListView>

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• Is it possible to write a generic +1 method for numeric box types in Java?

  - by polygenelubricants

  This is NOT homework. Part 1 Is it possible to write a generic method, something like this: <T extends Number> T plusOne(T num) { return num + 1; // DOESN'T COMPILE! How to fix??? } Short of using a bunch of instanceof and casts, is this possible? Part 2 The following 3 methods compile: Integer plusOne(Integer num) { return num + 1; } Double plusOne(Double num) { return num + 1; } Long plusOne(Long num) { return num + 1; } Is it possible to write a generic version that bound T to only Integer, Double, or Long?

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• ADF Taskflow Transaction Management

  - by raghu.yadav

  There are four transaction management properties available, please refer the guide http://download.oracle.com/docs/cd/E15523_01/web.1111/b31974/taskflows_complex.htm#BABICCGC for detail description. In short : 1) - does not participate in any transaction management 2) Always Use Existing Transaction - the bounded task flow participates in an existing transaction 3) Use Existing Transaction If Possible - bounded task flow either participates in an existing transaction or starts a new transaction 4) Always Begin New Transaction - new transaction starts when the bounded task flow is entered 2) Always Begin New Transaction : There is already a example exists by andre use existing transaction example

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• ADF Taskflow Reentry-not-allowed and Reentry-allowed

  - by raghu.yadav

  Here is the sample usecase to demonstrate how reentry-not-allowed and reentry-allowed properties works. what doc says about these 2 properties : reentry-allowed: Reentry is allowed on any view activity within the ADF bounded task flow reentry-not-allowed: Reentry of the ADF bounded task flow is not allowed. If you specify reentry-not-allowed on a task flow definition, an end user can still click the browser back button and return to a page within the bounded task flow. However, if the user does anything on the page such as clicking a button, an exception (for example, InvalidTaskFlowReentry) is thrown indicating the bounded task flow was reentered improperly. The actual reentry condition is identified upon the submit of the reentered page. Ingrediants : main.jspx - Jobs_TF - jobs.jspx scenario. click RunTrx button in main.jspx navigates to jobs page by entering into Jobs taskflow. click jobs page back button to navigate back to main.jspx, now click browser back button to navigate jobs.jspx and then click jobs page back Button to see reentry-not-allowed error message.

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• How to test Laptop NIC's throughput using a router and PC - without be bounded?

  - by 0x90

  My setup includes: Cisco router An i-7 PC running windows A laptop with high speed wifi nic, which I want to check its throughput. I would like to run an FTP server on the PC. hook the router over cables to the PC. I would like to have the PC create its own subnet accessible via the cisco router that would be hooked directly to the PC's nic. From the laptop I want to connect via wifi to the PC's wireless router and connect to the ftp server on the PC. is it possible? how do i connect the router to the PC nic and make it broadcast a subnet via wifi for my laptop to connect to? how do i configure an FTP server to operate only on this subnet?

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• a more pythonic way to express conditionally bounded loop?

  - by msw

  I've got a loop that wants to execute to exhaustion or until some user specified limit is reached. I've got a construct that looks bad yet I can't seem to find a more elegant way to express it; is there one? def ello_bruce(limit=None): for i in xrange(10**5): if predicate(i): if not limit is None: limit -= 1 if limit <= 0: break def predicate(i): # lengthy computation return True Holy nesting! There has to be a better way. For purposes of a working example, xrange is used where I normally have an iterator of finite but unknown length (and predicate sometimes returns False).

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• Safe and polymorphic toEnum

  - by jetxee

  I'd like to write a safe version of toEnum: safeToEnum :: (Enum t, Bounded t) => Int -> Maybe t A naive implementation: safeToEnum :: (Enum t, Bounded t) => Int -> Maybe t safeToEnum i = if (i >= fromEnum (minBound :: t)) && (i <= fromEnum (maxBound :: t)) then Just . toEnum $ i else Nothing main = do print $ (safeToEnum 1 :: Maybe Bool) print $ (safeToEnum 2 :: Maybe Bool) And it doesn't work: safeToEnum.hs:3:21: Could not deduce (Bounded t1) from the context () arising from a use of `minBound' at safeToEnum.hs:3:21-28 Possible fix: add (Bounded t1) to the context of an expression type signature In the first argument of `fromEnum', namely `(minBound :: t)' In the second argument of `(>=)', namely `fromEnum (minBound :: t)' In the first argument of `(&&)', namely `(i >= fromEnum (minBound :: t))' safeToEnum.hs:3:56: Could not deduce (Bounded t1) from the context () arising from a use of `maxBound' at safeToEnum.hs:3:56-63 Possible fix: add (Bounded t1) to the context of an expression type signature In the first argument of `fromEnum', namely `(maxBound :: t)' In the second argument of `(<=)', namely `fromEnum (maxBound :: t)' In the second argument of `(&&)', namely `(i <= fromEnum (maxBound :: t))' As well as I understand the message, the compiler does not recognize that minBound and maxBound should produce exactly the same type as in the result type of safeToEnum inspite of the explicit type declaration (:: t). Any idea how to fix it?

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• Five hours of Task Flow Overview Recordings Available

  - by Frank Nimphius

  In addition to the ADF Controller task flow documentation in Oracle Fusion Middleware Fusion Developer's Guide for Oracle Application Development Framework 11g Release 1 http://download.oracle.com/docs/cd/E21764_01/web.1111/b31974/partpage3.htm#BABHIIAI The ADF Insider website … http://www.oracle.com/technetwork/developer-tools/adf/learnmore/adfinsider-093342.html … hosts five online videos that explain how to build and work with ADF Controller task flows in Oracle ADF. ADF Task Flow - Overview (Part 1) This 90 minute recording introduces the concept of ADF unbounded and bounded task flows, as well as other ADF Controller features. The session starts with an overview of unbounded task flows, bounded task flows and the different activities that exist for developers to build complex application flows. Exception handling and the Train navigation model is also covered in this first part of a two part series. By example of developing a sample application, the recording guides viewers through building unbounded and bounded task flows. This session is continued in a second part. http://download.oracle.com/otn_hosted_doc/jdeveloper/11gdemos/taskflow-overview-p1/taskflow-overview-p1.html ADF Task Flow - Overview (Part 2) This 75 minute session continues where part 1 ended and completes the sample application that guides viewers through different aspects of unbounded and bounded task flow development. In this recording, memory scopes, save for later, task flow opening in dialogs and remote task flow calls are explained and demonstrated. If you are new to ADF Task Flow, then it is recommended to first watch part 1 of this series to be able to follow the explanation guided by the sample application. http://download.oracle.com/otn_hosted_doc/jdeveloper/11gdemos/taskflow-overview-p2/taskflow-overview-p2.html ADF Region Interaction - An Overview This session covers most of the options that exist for communicating between regions. It briefly discusses what it takes to build regions from bounded task flows before going into details using slides and samples. The following interaction is explained: contextual events, queue action in region, input parameters and PPR, drag and drop, shared Data Controls, parent action and region navigation listener. http://download.oracle.com/otn_hosted_doc/jdeveloper/11gdemos/adf-region-interaction/adf-region-interaction.html ADF Region Interaction - Contextual Events Contextual event is used as a communication channel between a parent view and its contained regions, as well as between regions. By example, this session explains how to set up contextual events, how to define producers and event listeners and how to define the payload message. http://download.oracle.com/otn_hosted_doc/jdeveloper/11gdemos/AdfInsiderContextualEvents/AdfInsiderContextualEvents.html

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• Examples of monoids/semigroups in programming

  - by jkff

  It is well-known that monoids are stunningly ubiquitous in programing. They are so ubiquitous and so useful that I, as a 'hobby project', am working on a system that is completely based on their properties (distributed data aggregation). To make the system useful I need useful monoids :) I already know of these: Numeric or matrix sum Numeric or matrix product Minimum or maximum under a total order with a top or bottom element (more generally, join or meet in a bounded lattice, or even more generally, product or coproduct in a category) Set union Map union where conflicting values are joined using a monoid Intersection of subsets of a finite set (or just set intersection if we speak about semigroups) Intersection of maps with a bounded key domain (same here) Merge of sorted sequences, perhaps with joining key-equal values in a different monoid/semigroup Bounded merge of sorted lists (same as above, but we take the top N of the result) Cartesian product of two monoids or semigroups List concatenation Endomorphism composition. Now, let us define a quasi-property of an operation as a property that holds up to an equivalence relation. For example, list concatenation is quasi-commutative if we consider lists of equal length or with identical contents up to permutation to be equivalent. Here are some quasi-monoids and quasi-commutative monoids and semigroups: Any (a+b = a or b, if we consider all elements of the carrier set to be equivalent) Any satisfying predicate (a+b = the one of a and b that is non-null and satisfies some predicate P, if none does then null; if we consider all elements satisfying P equivalent) Bounded mixture of random samples (xs+ys = a random sample of size N from the concatenation of xs and ys; if we consider any two samples with the same distribution as the whole dataset to be equivalent) Bounded mixture of weighted random samples Which others do exist?

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• Securing an ADF Application using OES11g: Part 2

  - by user12587121

  To validate the integration with OES we need a sample ADF Application that is rich enough to allow us to test securing the various ADF elements.  To achieve this we can add some items including bounded task flows to the application developed in this tutorial. A sample JDeveloper 11.1.1.6 project is available here. It depends on the Fusion Order Demo (FOD) database schema which is easily created using the FOD build scripts.In the deployment we have chosen to enable only ADF Authentication as we will delegate Authorization, mostly, to OES.The welcome page of the application with all the links exposed looks as follows: The Welcome, Browse Products, Browse Stock and System Administration links go to pages while the Supplier Registration and Update Stock are bounded task flows.  The Login link goes to a basic login page and once logged in a link is presented that goes to a logout page.  Only the Browse Products and Browse Stock pages are really connected to the database--the other pages and task flows do not really perform any operations on the database. Required Security Policies We make use of a set of test users and roles as decscribed on the welcome page of the application.  In order to exercise the different authorization possibilities we would like to enforce the following sample policies: Anonymous users can see the Login, Welcome and Supplier Registration links. They can also see the Welcome page, the Login page and follow the Supplier Registration task flow.  They can see the icon adjacent to the Login link indicating whether they have logged in or not. Authenticated users can see the Browse Product page. Only staff granted the right can see the Browse Product page cost price value returned from the database and then only if the value is below a configurable limit. Suppliers and staff can see the Browse Stock links and pages.  Customers cannot. Suppliers can see the Update Stock link but only those with the update permission are allowed to follow the task flow that it launches.  We could hide the link but leave it exposed here so we can easily demonstrate the method call activity protecting the task flow. Only staff granted the right can see the System Administration link and the System Administration page it accesses. Implementing the required policies In order to secure the application we will make use of the following techniques: EL Expressions and Java backing beans: JSF has the notion of EL expressions to reference data from backing Java classes.  We use these to control the presentation of links on the navigation page which respect the security contraints.  So a user will not see links that he is not allowed to click on into. These Java backing beans can call on to OES for an authorization decision.  Important Note: naturally we would configure the WLS domain where our ADF application is running as an OES WLS SM, which would allow us to efficiently query OES over the PEP API.  However versioning conflicts between OES 11.1.1.5 and ADF 11.1.1.6 mean that this is not possible.  Nevertheless, we can make use of the OES RESTful gateway technique from this posting in order to call into OES. You can easily create and manage backing beans in Jdeveloper as follows: Custom ADF Phase Listener: ADF extends the JSF page lifecycle flow and allows one to hook into the flow to intercept page rendering.  We use this to put a check prior to rendering any protected pages, again calling on to OES via the backing bean.  Phase listeners are configured in the adf-settings.xml file.  See the MyPageListener.java class in the project.  Here, for example,  is the code we use in the listener to check for allowed access to the sysadmin page, navigating back to the welcome page if authorization is not granted:                         if (page != null && (page.equals("/system.jspx") || page.equals("/system"))){                             System.out.println("MyPageListener: Checking Authorization for /system");                             if (getValue("#{oesBackingBean.UIAccessSysAdmin}").toString().equals("false") ){                                   System.out.println("MyPageListener: Forcing navigation away from system" +                                       "to welcome");                                 NavigationHandler nh = fc.getApplication().getNavigationHandler();                                   nh.handleNavigation(fc, null, "welcome");                               } else {                                 System.out.println("MyPageListener: access allowed");                              }                         } Method call activity: our app makes use of bounded task flows to implement the sequence of pages that update the stock or allow suppliers to self register.  ADF takes care of ensuring that a bounded task flow can be entered by only one page.  So a way to protect all those pages is to make a call to OES in the first activity and then either exit the task flow or continue depending on the authorization decision.  The method call returns a String which contains the name of the transition to effect. This is where we configure the method call activity in JDeveloper: We implement each of the policies using the above techniques as follows: Policies 1 and 2: as these policies concern the coarse grained notions of controlling access to anonymous and authenticated users we can make use of the container’s security constraints which can be defined in the web.xml file.  The allPages constraint is added automatically when we configure Authentication for the ADF application.  We have added the “anonymousss” constraint to allow access to the the required pages, task flows and icons: <security-constraint>    <web-resource-collection>      <web-resource-name>anonymousss</web-resource-name>      <url-pattern>/faces/welcome</url-pattern>      <url-pattern>/afr/*</url-pattern>      <url-pattern>/adf/*</url-pattern>      <url-pattern>/key.png</url-pattern>      <url-pattern>/faces/supplier-reg-btf/*</url-pattern>      <url-pattern>/faces/supplier_register_complete</url-pattern>    </web-resource-collection>  </security-constraint> Policy 3: we can place an EL expression on the element representing the cost price on the products.jspx page: #{oesBackingBean.dataAccessCostPrice}. This EL Expression references a method in a Java backing bean that will call on to OES for an authorization decision.  In OES we model the authorization requirement by requiring the view permission on the resource /MyADFApp/data/costprice and granting it only to the staff application role.  We recover any obligations to determine the limit.  Policy 4: is implemented by putting an EL expression on the Browse Stock link #{oesBackingBean.UIAccessBrowseStock} which checks for the view permission on the /MyADFApp/ui/stock resource. The stock.jspx page is protected by checking for the same permission in a custom phase listener—if the required permission is not satisfied then we force navigation back to the welcome page. Policy 5: the Update Stock link is protected with the same EL expression as the Browse Link: #{oesBackingBean.UIAccessBrowseStock}.  However the Update Stock link launches a bounded task flow and to protect it the first activity in the flow is a method call activity which will execute an EL expression #{oesBackingBean.isUIAccessSupplierUpdateTransition}  to check for the update permission on the /MyADFApp/ui/stock resource and either transition to the next step in the flow or terminate the flow with an authorization error. Policy 6: the System Administration link is protected with an EL Expression #{oesBackingBean.UIAccessSysAdmin} that checks for view access on the /MyADF/ui/sysadmin resource.  The system page is protected in the same way at the stock page—the custom phase listener checks for the same permission that protects the link and if not satisfied we navigate back to the welcome page. Testing the Application To test the application: deploy the OES11g Admin to a WLS domain deploy the OES gateway in a another domain configured to be a WLS SM. You must ensure that the jps-config.xml file therein is configured to allow access to the identity store, otherwise the gateway will not b eable to resolve the principals for the requested users.  To do this ensure that the following elements appear in the jps-config.xml file: <serviceProvider type="IDENTITY_STORE" name="idstore.ldap.provider" class="oracle.security.jps.internal.idstore.ldap.LdapIdentityStoreProvider">             <description>LDAP-based IdentityStore Provider</description>  </serviceProvider> <serviceInstance name="idstore.ldap" provider="idstore.ldap.provider">             <property name="idstore.config.provider" value="oracle.security.jps.wls.internal.idstore.WlsLdapIdStoreConfigProvider"/>             <property name="CONNECTION_POOL_CLASS" value="oracle.security.idm.providers.stdldap.JNDIPool"/></serviceInstance> <serviceInstanceRef ref="idstore.ldap"/> download the sample application and change the URL to the gateway in the MyADFApp OESBackingBean code to point to the OES Gateway and deploy the application to an 11.1.1.6 WLS domain that has been extended with the ADF JRF files. You will need to configure the FOD database connection to point your database which contains the FOD schema. populate the OES Admin and OES Gateway WLS LDAP stores with the sample set of users and groups.  If  you have configured the WLS domains to point to the same LDAP then it would only have to be done once.  To help with this there is a directory called ldap_scripts in the sample project with ldif files for the test users and groups. start the OES Admin console and configure the required OES authorization policies for the MyADFApp application and push them to the WLS SM containing the OES Gateway. Login to the MyADFApp as each of the users described on the login page to test that the security policy is correct. You will see informative logging from the OES Gateway and the ADF application to their respective WLS consoles. Congratulations, you may now login to the OES Admin console and change policies that will control the behaviour of your ADF application--change the limit value in the obligation for the cost price for example, or define Role Mapping policies to determine staff access to the system administration page based on user profile attributes. ADF Development Notes Some notes on ADF development which are probably typical gotchas: May need this on WLS startup in order to allow us to overwrite credentials for the database, the signal here is that there is an error trying to access the data base: -Djps.app.credential.overwrite.allowed=true Best to call Bounded Task flows via a CommandLink (as opposed to a go link) as you cannot seem to start them again from a go link, even having completed the task flow correctly with a return activity. Once a bounded task flow (BTF) is initated it must complete correctly  via a return activity—attempting to click on any other link whilst in the context of a  BTF has no effect.  See here for example: When using the ADF Authentication only security approach it seems to be awkward to allow anonymous access to the welcome and registration pages.  We can achieve anonymous access using the web.xml security constraint shown above (where no auth-constraint is specified) however it is not clear what needs to be listed in there….for example the /afr/* and /adf/* are in there by trial and error as sometimes the welcome page will not render if we omit those items.  I was not able to use the default allPages constraint with for example the anonymous-role or the everyone WLS group in order to be able to allow anonymous access to pages. The ADF security best practice advises placing all pages under the public_html/WEB-INF folder as then ADF will not allow any direct access to the .jspx pages but will only allow acces via a link of the form /faces/welcome rather than /faces/welcome.jspx.  This seems like a very good practice to follow as having multiple entry points to data is a source of confusion in a web application (particulary from a security point of view). In Authentication+Authorization mode only pages with a Page definition file are protected.  In order to add an emty one right click on the page and choose Go to Page Definition.  This will create an empty page definition and now the page will require explicit permission to be seen. It is advisable to give a unique context root via the weblogic.xml for the application, as otherwise the application will clash with any other application with the same context root and it will not deploy

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• ADF Reusable Artefacts

  - by Arda Eralp

  Primary reusable ADF Business Component: Entity Objects (EOs) View Objects (VOs) Application Modules (AMs) Framework Extensions Classes Primary reusable ADF Controller: Bounded Task Flows (BTFs) Task Flow Templates Primary reusable ADF Faces: Page Templates Skins Declarative Components Utility Classes Certain components will often be used more than once. Whether the reuse happens within the same application, or across different applications, it is often advantageous to package these reusable components into a library that can be shared between different developers, across different teams, and even across departments within an organization. In the world of Java object-oriented programming, reusing classes and objects is just standard procedure. With the introduction of the model-view-controller (MVC) architecture, applications can be further modularized into separate model, view, and controller layers. By separating the data (model and business services layers) from the presentation (view and controller layers), you ensure that changes to any one layer do not affect the integrity of the other layers. You can change business logic without having to change the UI, or redesign the web pages or front end without having to recode domain logic. Oracle ADF and JDeveloper support the MVC design pattern. When you create an application in JDeveloper, you can choose many application templates that automatically set up data model and user interface projects. Because the different MVC layers are decoupled from each other, development can proceed on different projects in parallel and with a certain amount of independence. ADF Library further extends this modularity of design by providing a convenient and practical way to create, deploy, and reuse high-level components. When you first design your application, you design it with component reusability in mind. If you created components that can be reused, you can package them into JAR files and add them to a reusable component repository. If you need a component, you may look into the repository for those components and then add them into your project or application. For example, you can create an application module for a domain and package it to be used as the data model project in several different applications. Or, if your application will be consuming components, you may be able to load a page template component from a repository of ADF Library JARs to create common look and feel pages. Then you can put your page flow together by stringing together several task flow components pulled from the library. An ADF Library JAR contains ADF components and does not, and cannot, contain other JARs. It should not be confused with the JDeveloper library, Java EE library, or Oracle WebLogic shared library. Reusable Component Description Data Control Any data control can be packaged into an ADF Library JAR. Some of the data controls supported by Oracle ADF include application modules, Enterprise JavaBeans, web services, URL services, JavaBeans, and placeholder data controls. Application Module When you are using ADF Business Components and you generate an application module, an associated application module data control is also generated. When you package an application module data control, you also package up the ADF Business Components associated with that application module. The relevant entity objects, view objects, and associations will be a part of the ADF Library JAR and available for reuse. Business Components Business components are the entity objects, view objects, and associations used in the ADF Business Components data model project. You can package business components by themselves or together with an application module. Task Flows & Task Flow Templates Task flows can be packaged into an ADF Library JAR for reuse. If you drop a bounded task flow that uses page fragments, JDeveloper adds a region to the page and binds it to the dropped task flow. ADF bounded task flows built using pages can be dropped onto pages. The drop will create a link to call the bounded task flow. A task flow call activity and control flow will automatically be added to the task flow, with the view activity referencing the page. If there is more than one existing task flow with a view activity referencing the page, it will prompt you to select the one to automatically add a task flow call activity and control flow. If an ADF task flow template was created in the same project as the task flow, the ADF task flow template will be included in the ADF Library JAR and will be reusable. Page Templates You can package a page template and its artifacts into an ADF Library JAR. If the template uses image files and they are included in a directory within your project, these files will also be available for the template during reuse. Declarative Components You can create declarative components and package them for reuse. The tag libraries associated with the component will be included and loaded into the consuming project. You can also package up projects that have several different reusable components if you expect that more than one component will be consumed. For example, you can create a project that has both an application module and a bounded task flow. When this ADF Library JAR file is consumed, the application will have both the application module and the task flow available for use. You can package multiple components into one JAR file, or you can package a single component into a JAR file. Oracle ADF and JDeveloper give you the option and flexibility to create reusable components that best suit you and your organization. You create a reusable component by using JDeveloper to package and deploy the project that contains the components into a ADF Library JAR file. You use the components by adding that JAR to the consuming project. At design time, the JAR is added to the consuming project's class path and so is available for reuse. At runtime, the reused component runs from the JAR file by reference.

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• How to flush DNS cache in Windows Mobile programmatically?

  - by Bounded

  Hello, My windows mobile application (written in C# with the compact framework) needs to know if a particular machine is active or not. To achieve this goal, I thought to use a ping mechanism. I tried to use the Ping class implemented in the opennetcf framework (the System.Net.NetworkInformation.Ping class for the .NET Framework is not part of the compact framework). Because I give to the Ping.Send function a host name, it first tries to resolve this host name and to retrieve an IP address. But i observe the following problem : If the first dns resolution fails (because the network is down at this moment), and if the application tries immediately again to send the ping, it fails too, even if the network is note down anymore. I check with a famous network protocol analyzer and i saw that only the requests concerning the first dns resolution are sent. The requests concerning the dns resolution of the second ping are not sent. Why is the second dns request not sent ? Is there any dns cache mechanism on such Windows Mobile devices ? If yes, can this mechanism beeing flushed programmatically ? EDIT : I gave up finding a solution to this DNS flush. I chose to ping an IP adress instead of a name machine. The problem of pinging an hard coded adress IP is that we have to be 100% sure that this IP will not change. The gateway IP can be used because it's always reachable (if it does not, it means the network is down).

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