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• Halloween: Season for Java Embedded Internet of Spooky Things (IoST) (Part 4)

  - by hinkmond

  And now here's the Java code that you'll need to read your ghost sensor on your Raspberry Pi The general idea is that you are using Java code to access the GPIO pin on your Raspberry Pi where the ghost sensor (JFET trasistor) detects minute changes in the electromagnetic field near the Raspberry Pi and will change the GPIO pin to high (+3 volts) when something is detected, otherwise there is no value (ground). Here's that Java code: try { /*** Init GPIO port(s) for input ***/ // Open file handles to GPIO port unexport and export controls FileWriter unexportFile = new FileWriter("/sys/class/gpio/unexport"); FileWriter exportFile = new FileWriter("/sys/class/gpio/export"); for (String gpioChannel : GpioChannels) { System.out.println(gpioChannel); // Reset the port File exportFileCheck = new File("/sys/class/gpio/gpio"+gpioChannel); if (exportFileCheck.exists()) { unexportFile.write(gpioChannel); unexportFile.flush(); } // Set the port for use exportFile.write(gpioChannel); exportFile.flush(); // Open file handle to input/output direction control of port FileWriter directionFile = new FileWriter("/sys/class/gpio/gpio" + gpioChannel + "/direction"); // Set port for input directionFile.write(GPIO_IN); } /*** Read data from each GPIO port ***/ RandomAccessFile[] raf = new RandomAccessFile[GpioChannels.length]; int sleepPeriod = 10; final int MAXBUF = 256; byte[] inBytes = new byte[MAXBUF]; String inLine; int zeroCounter = 0; // Get current timestamp with Calendar() Calendar cal; DateFormat dateFormat = new SimpleDateFormat("yyyy/MM/dd HH:mm:ss.SSS"); String dateStr; // Open RandomAccessFile handle to each GPIO port for (int channum=0; channum And, then we just load up our Java SE Embedded app, place each Raspberry Pi with a ghost sensor attached in strategic locations around our Santa Clara office (which apparently is very haunted by ghosts from the Agnews Insane Asylum 1906 earthquake), and watch our analytics for any ghosts. Easy peazy. See the previous posts for the full series on the steps to this cool demo: Halloween: Season for Java Embedded Internet of Spooky Things (IoST) (Part 1) Halloween: Season for Java Embedded Internet of Spooky Things (IoST) (Part 2) Halloween: Season for Java Embedded Internet of Spooky Things (IoST) (Part 3) Halloween: Season for Java Embedded Internet of Spooky Things (IoST) (Part 4) Hinkmond

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• When to use functional programming approach and when not? (in Java)

  - by john smith optional

  let's assume I have a task to create a Set of class names. To remove duplication of .getName() method calls for each class, I used org.apache.commons.collections.CollectionUtils and org.apache.commons.collections.Transformer as follows: Snippet 1: Set<String> myNames = new HashSet<String>(); CollectionUtils.collect( Arrays.<Class<?>>asList(My1.class, My2.class, My3.class, My4.class, My5.class), new Transformer() { public Object transform(Object o) { return ((Class<?>) o).getName(); } }, myNames); An alternative would be this code: Snippet 2: Collections.addAll(myNames, My1.class.getName(), My2.class.getName(), My3.class.getName(), My4.class.getName(), My5.class.getName()); So, when using functional programming approach is overhead and when it's not and why? Isn't my usage of functional programming approach in snippet 1 is an overhead and why?

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• What is the best way to have the same website in multiple domains?

  - by Daniel Magliola

  I would like to have the same website to sell a specific product, in multiple domains , to take advantage of keywords matching the domain name, for several different searches. However, I understand that having the same content in multiple sites will unleash the wrath of Google. If I have a redirect from all domains minus one, to that last one, do I still get any bonus for the "magic exact domain match jackpot"? Same question applies to canonical URLs... What's the best way to approach this? Thanks!

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• Creating Rectangle-based buttons with OnClick events

  - by Djentleman

  As the title implies, I want a Button class with an OnClick event handler. It should fire off connected events when it is clicked. This is as far as I've made it: public class Button { public event EventHandler OnClick; public Rectangle Rec { get; set; } public string Text { get; set; } public Button(Rectangle rec, string text) { this.Rec = rec; this.Text = text; } } I have no clue what I'm doing with regards to events. I know how to use them but creating them myself is another matter entirely. I've also made buttons without using events that work on a case-by-case basis. So basically, I want to be able to attach methods to the OnClick EventHandler that will fire when the Button is clicked (i.e., the mouse intersects Rec and the left mouse button is clicked).

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• Using the @ in SQL Azure Connections

  - by BuckWoody

  The other day I was working with a client on an application they were changing to a hybrid architecture – some data on-premise and other data in SQL Azure and Windows Azure Blob storage. I had them make a couple of corrections - the first was that all communications to SQL Azure need to be encrypted. It’s a simple addition to the connection string, depending on the library you use. Which brought up another interesting point. They had been using something that looked like this, using the .NET provider: Server=tcp:[serverName].database.windows.net;Database=myDataBase; User ID=LoginName;Password=myPassword; Trusted_Connection=False;Encrypt=True; This includes most of the formatting needed for SQL Azure. It specifies TCP as the transport mechanism, the database name is included, Trusted_Connection is off, and encryption is on. But it needed one more change: Server=tcp:[serverName].database.windows.net;Database=myDataBase; User ID=[LoginName]@[serverName];Password=myPassword; Trusted_Connection=False;Encrypt=True; Notice the difference? It’s the User ID parameter. It includes the @ symbol and the name of the server – not the whole DNS name, just the server name itself. The developers were a bit surprised, since it had been working with the first format that just used the user name. Why did both work, and why is one better than the other? It has to do with the connection library you use. For most libraries, the user name is enough. But for some libraries (subject to change so I don’t list them here) the server name parameter isn’t sent in the way the load balancer understands, so you need to include the server name right in the login, so the system can parse it correctly. Keep in mind, the string limit for that is 128 characters – so take the @ symbol and the server name into consideration for user names. The user connection info is detailed here: http://msdn.microsoft.com/en-us/library/ee336268.aspx Upshot? Include the @servername on your connection string just to be safe. And plan for that extra space…  

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• How to show pending messages using WLST?

  - by lmestre

  Here are the steps: 1. . ./setDomainEnv.sh2. java weblogic.WLST3. connect('weblogic','welcome1','t3://localhost:7001')4. domainRuntime()5. cd('ServerRuntimes/MS1/JMSRuntime/MS1.jms/JMSServers/JMSServer1/Destinations/JMSModule1!Queue1')6. cursor1=cmo.getMessages('true',9999999,10)                                                 **String(selector),Integer(timeout),Integer(state)7. msgs = cmo.getNext(cursor1, 10)                  ** This step gets 10 messages, you can call again cmo.getNext(cursor1, 10) to get the next 10 msgs8. print(msgs)My assumption, is that you had created:a. Managed Server MS1.b. JMS Server JMSServer1.c. Module called JMSModule1.d. Inside of JMSModule1, a Queue called Queue1.If you read my previous post:How to get Messages Pending Count from a Queue using WLST? https://blogs.oracle.com/LuzMestre/entry/how_to_get_messages_pendingYou can see that both are very similar.  Sometimes it is difficult to get a WLST Script sample, but you can use ls() function to know about other functionalities you don't have a sample code.***Until step 5, nothing new comparing to my previous post.5. cd('ServerRuntimes/MS1/JMSRuntime/MS1.jms/JMSServers/JMSServer1/Destinations/JMSModule1!Queue1')6. ls()You will see, MessagesPendingCount, getMessages along a lot of other functionalities available in this Queue. e.g, you can see:-r-x   getMessages                                  String : String(selector),Integer(timeout),Integer(state)Here you can check the complete MBean Reference:http://docs.oracle.com/cd/E23943_01/apirefs.1111/e13951/core/index.htmlSee JMSDestinationRuntimeMBean.Enjoy!

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• Proxied calls not working as expected

  - by AndyH

  I have been modifying an application to have a cleaner client/server split to allow for load splitting and resource sharing etc. Everything is written to an interface so it was easy to add a remoting layer to the interface using a proxy. Everything worked fine. The next phase was to add a caching layer to the interface and again this worked fine and speed was improved but not as much as I would have expected. On inspection it became very clear what was going on. I feel sure that this behavior has been seen many times before and there is probably a design pattern to solve the problem but it eludes me and I'm not even sure how to describe it. It is easiest explained with an example. Let's imagine the interface is interface IMyCode { List<IThing> getLots( List<String> ); IThing getOne( String id ); } The getLots() method calls getOne() and fills up the list before returning. The interface is implemented at the client which is proxied to a remoting client which then calls the remoting server which in turn calls the implementation at the server. At the client and the server layers there is also a cache. So we have :- Client interface | Client cache | Remote client | Remote server | Server cache | Server interface If we call getOne("A") at the client interface, the call is passed to the client cache which faults. This then calls the remote client which passes the call to the remote server. This then calls the server cache which also faults and so the call is eventually passed to the server interface which actually gets the IThing. In turn the server cache is filled and finally the client cache also. If getOne("A") is again called at the client interface the client cache has the data and it gets returned immediately. If a second client called getOne("B") it would fill the server cache with "B" as well as it's own client cache. Then, when the first client calls getOne("B") the client cache faults but the server cache has the data. This is all as one would expect and works well. Now lets call getLots( [ "C", "D" ] ). This works as you would expect by calling getOne() twice but there is a subtlety here. The call to getLots() cannot directly make use of the cache. Therefore the sequence is to call the client interface which in turn calls the remote client, then the remote server and eventually the server interface. This then calls getOne() to fill the list before returning. The problem is that the getOne() calls are being satisfied at the server when ideally they should be satisfied at the client. If you imagine that the client/server link is really slow then it becomes clear why the client call is more efficient than the server call once the client cache has the data. This example is contrived to illustrate the point. The more general problem is that you cannot just keep adding proxied layers to an interface and expect it to work as you would imagine. As soon as the call goes 'through' the proxy any subsequent calls are on the proxied side rather than 'self' side. Have I failed to learn or not learned something correctly? All this is implemented in Java and I haven't used EJBs. It seems that the example may be confusing. The problem is nothing to do with cache efficiencies. It is more to do with an illusion created by the use of proxies or AOP techniques in general. When you have an object whose class implements an interface there is an assumption that a call on that object might make further calls on that same object. For example, public String getInternalString() { return InetAddress.getLocalHost().toString(); } public String getString() { return getInternalString(); } If you get an object and call getString() the result depends where the code is running. If you add a remoting proxy to the class then the result could be different for calls to getString() and getInternalString() on the same object. This is because the initial call gets 'deproxied' before the actual method is called. I find this not only confusing but I wonder how I can control this behavior especially as the use of the proxy may be by a third party. The concept is fine but the practice is certainly not what I expected. Have I missed the point somewhere?

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• Make Apache encode or replace quotes instead of escaping them?

  - by mplungjan

  In the dcoumentation I read Format Notes For security reasons, starting with version 2.0.46, non-printable and other special characters in %r, %i and %o are escaped using \xhh sequences, where hh stands for the hexadecimal representation of the raw byte. Exceptions from this rule are " and \, which are escaped by prepending a backslash, and all whitespace characters, which are written in their C-style notation (\n, \t, etc). In versions prior to 2.0.46, no escaping was performed on these strings so you had to be quite careful when dealing with raw log files. This is a problem for Analog which is still the handiest analyser I use. I get .... "GET /somerequest?q=\"quoted string\"&someparm=bla" in the logfile and it is of course flagged as corrupt since Analog expects .... "GET /somerequest?q=%22quoted string%22&someparm=bla" or similar. I realise I can pre-process using something like perl -p -i.bak -e 's/\\"/%22/g' logfile But I'd rather not have to add this step to these files which are 50-90MB zipped per day Thanks for any pointers

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• The performance implications of IEnumerable vs. IQueryable

  It all started innocently enough. I was implementing a "Older Posts/Newer Posts" feature for my new web site and was writing code like this:IEnumerable<Post> FilterByCategory(IEnumerable<Post> posts, string category) {  if( !string.IsNullOrEmpty(category) ) { return posts.Where(p => p.Category.Contains(category)); }}...  var posts = FilterByCategory(db.Posts, category);  int count = posts.Count();... The "db" was an EF object context object, but it could just as...Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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• The performance implications of IEnumerable vs. IQueryable

  It all started innocently enough. I was implementing a "Older Posts/Newer Posts" feature for my new web site and was writing code like this:IEnumerable<Post> FilterByCategory(IEnumerable<Post> posts, string category) {  if( !string.IsNullOrEmpty(category) ) { return posts.Where(p => p.Category.Contains(category)); }}...  var posts = FilterByCategory(db.Posts, category);  int count = posts.Count();... The "db" was an EF object context object, but it could just as...Did you know that DotNetSlackers also publishes .net articles written by top known .net Authors? We already have over 80 articles in several categories including Silverlight. Take a look: here.

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• NetBeans 7.3 Beta2 is Out!

  - by Ondrej Brejla

  NetBeans 7.3 Beta2 was published today. You can download it. You could read about the PHP features added to the NetBeans 7.3 release here on the blog, but the main features added or improved are: Parsers for Namespaced Annotations (Symfony 2, Doctrine 2, etc.), Basic Composer Integration (Dependency Manager for PHP), Twig Code Completion (with documentation), Smarty Braces Matching for Related Tags, Smarty Parser Errors of Unmatched Tags. As obvious you can help us to test the build. Just try it and if you find an issue / error, please report it. Thanks for your help.

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• Can I make query strings produce separate pages?

  - by John Smith

  I have a profile page with a URL like so: localhost/profile.php/?username=Bob I was wondering, if I had a separate <title> which changed according to the username, would they produce separate pages in the google search results? How do I tell Google to only use the username string or does it search within the title? On a similar note, how would I create a separate page with the username like so: localhost/bob instead of a query string like facebook does. Do that make a new file for each user?

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• What is the general definition of something that can be included or excluded?

  - by gutch

  When an application presents a user with a list of items, it's pretty common that it permits the user to filter the items. Often a 'filter' feature is implemented as a set of include or exclude rules. For example: include all emails from [email protected], and exclude those emails without attachments I've seen this include/exclude pattern often; for example Maven and Google Analytics filter things this way. But now that I'm implementing something like this myself, I don't know what to call something that could be either included or excluded. In specific terms: If I have a database table of filter rules, each of which either includes or excludes matching items, what is an appropriate name of the field that stores include or exclude? When displaying a list of filters to a user, what is a good way to label the include or exclude value? (as a bonus, can anyone recommend a good implementation of this kind of filtering for inspiration?)

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• PL/SQL to delete invalid data from token Strings

  - by Jie Chen

  Previous article describes how to delete the duplicated values from token string in bulk mode. This one extends it and shows the way to delete invalid data. Scenario Support we have page_two and manufacturers tables in database and the table DDL is: SQL> desc page_two; Name NULL? TYPE ----------------------------------------- -------- ------------------------ MULTILIST04 VARCHAR2(765) SQL> SQL> desc manufacturers; Name NULL? TYPE ----------------------------------------- -------- ------ ID NOT NULL NUMBER NAME VARCHAR In table page_two, column multilist04 stores a token string splitted with common. Each token represent a valid ID in manufacturers table. My expectation is to delete invalid token strings from page_two.multilist04, which have no mapping id in manufacturers.id. For example in below SQL result: ,6295728,33,6295729,6295730,6295731,22, , value 33 and 22 are invalid data because there is no ID equals to 33 or 22 in manufacturers table. So I need to delete 33 and 22. SQL> col rowid format a20; SQL> col multilist04 format a50; SQL> select rowid, multilist04 from page_two; ROWID MULTILIST04 -------------------- -------------------------------------------------- AAB+UrADfAAAAhUAAI ,6295728,6295729,6295730,6295731, AAB+UrADfAAAAhUAAJ ,1111,6295728,6295729,6295730,6295731, AAB+UrADfAAAAhUAAK ,6295728,111,6295729,6295730,6295731, AAB+UrADfAAAAhUAAL ,6295728,6295729,6295730,6295731,22, AAB+UrADfAAAAhUAAM ,6295728,33,6295729,6295730,6295731,22, SQL> select id, encode_name from manufacturers where id in (1111,11,22,33); No rows selected SQL> Solution As there is no existing SPLIT function or related in PL/SQL, I should program it by myself. I code Split intermediate function which is used to get the token value between current splitter and next splitter. Next program is main entry point, it get each column value from page_two.multilist04, process each row based on cursor. When it get each multilist04 value, it uses above Split function to get each token string stored to singValue variant, then check if it exists in manufacturers.id. If not found, set fixFlag to 1, pending to be deleted.

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• Google Analytics: Why does "/" appear in goal funnel visualization?

  - by Lauren

  This is the goal funnel for checkout. Does anyone have any idea where the "/" is coming from? The cart page is at site: game on glove dot com (I don't want this stackoverflow page being indexed in google particularly well). Go to the site, click on the order button, make your selection, and click the button to enter the cart (it resolves to /Cart and /Shop-Cart). I believe I used the regular expression matching to match "cart". So why the "/" (I don't know what is causing the home page to reload when users are on the Cart page within a Colorbox lightbox where the only way back to home or "/" is to hit the exit button in the top right of the lightbox)? Here's my one guess for the former question but it doesn't seem likely: See the "check out with paypal" button? If you hovered over it, it does default to the home page which is what might be the "/"... but it really redirects the user to the paypal.com page so it shouldn't also load the home page.

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• O'Reilly deal of the week to 23:59 PT 4/Sept/2012 - Master Regular Expressions

  - by TATWORTH

  O'Reilly at http://shop.oreilly.com/category/deals/regular-expressions-owo.do?code=WKRGEX are offering 50% off a range of e-books on mastering Regular Expressions "Take the guesswork out of using regular expressions. Learn powerful tips for matching, extracting, and transforming text as well as the gotchas to avoid. For one week only, SAVE 50% on these e-books and discover a whole new world of mastery over your code." I recommend Mastering Regular Expression to Dot Net developer as it covers the use of regular expressions across a number of environments, including Dot Net.

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• Google I/O 2012 - Gaming in the Cloud

  Google I/O 2012 - Gaming in the Cloud "Fred Sauer Many games developers are finding the easy development and deployment experience of Google App Engine ideal for building cloud based state-storage, matching making services and collaborations services. When you have a hit game, the last thing you want to do is worry about your server provisioning. App Engine has an always-free tier to get you started and then scales seamlessly to any size of usage. Game developers also use Google Cloud Storage to easily store and quickly deliver media files to clients around the world. For all I/O 2012 sessions, go to developers.google.com From: GoogleDevelopers Views: 1 0 ratings Time: 01:02:17 More in Science & Technology

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• how to have 'find' not return the current directory

  - by Pinpin

  I'm currently trying to find (and copy) all files and folder structure matching a specific pattern, in a specified directory and I'm so nearly there! Specifically, I want to recursively copy all folders not begining with a '_' character from a specified path. find /source/path/with/directories -maxdepth 1 -type d ! -name _\* -exec cp -R {} /destination/path \; In the /source/path/with/directories/ path are machine-specific directories beginning with '_' and others, and I'm only interested in copying the others. For a reason beyond me, the find command returns the /source/path/with/directories/ directory, and therefore copies its content, directories begining with '_' included. Anyone have a hint as to why that is? Thanks, Pascal

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• A quick list of all SharePoint 2010 Powershell commandlets

  - by Sahil Malik

  SharePoint 2010 Training: more information Ever wonder what powershell commandlets exist on your SharePoint 2010 installation? Easy! Just run the SharePoint 2010 Management Shell, and issue the following command - Get-Command -module Microsoft.SharePoint.PowerShell And if you wish to find matching commands for a certain task, for instance, I wish to know all commands that have anything to do with “Update”, I would issue the following command  - Get-Command -module Microsoft.SharePoint.PowerShell  | where{$_.name -match "Update"} And if you want to do exactly the same for stsadm, you could do something like this - Read full article ....

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• Quick path jumping

  - by Sebastian P.

  I was just at a lecture, where I noticed the lecturer using a command (probably aliased) to jump to a specific folder. Example: ~/code$ j sciproj ~/projects/sciproj2011/$ This looked quite slick, so I started wondering: Is this a standard utility, and if so, what is the name? I have two theories as to how it works: It can both create, delete and jump to aliases directly from the command-line in the style of the example, without having to set up aliases in a configuration file or script or whatnot manually. It searches the home directory for a folder matching the name and jumps to it. The second option seems a bit slow, however, so the first would be preferred.

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• Abandoment to blame for the last JavaScript file not always being loaded?

  - by Larsenal

  I have a code snippet for an app that users are loading as a 3rd party script on their site. The general sequence is as follows: Site loads http://www.example.com/foo.js foo.js does stuff 1 to 2 seconds later, foo.js loads bar.js Now in a perfect world, I'd want to see matching counts for the calls to foo.js and bar.js. However, bar.js loads only about 94% of the time. I'm wondering how much of this discrepancy might be attributable to site abandonment given the fact that bar.js is delayed by 1 or 2 seconds. I posted here instead of StackOverflow since I think it's more a question about what would be typical time on page when users abandon the page.

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• How to write comments to explain the "why" behind the callback function when the function and parameter names are insufficient for that?

  - by snowmantw

  How should I approach writing comments for callback functions? I want to explain the "why" behind the function when the function and parameter names are insufficient to explain what's going on. I have always wonder why comments like this can be so ordinary in documents of libraries in dynamic languages: /** * cb: callback // where's the arguments & effects? */ func foo( cb ) Maybe the common attitude is "you can look into source code on your own after all" which pushes people into leaving minimalist comments like this. But it seems like there should be a better way to comment callback functions. I've tried to comment callbacks in Haskell way: /** * cb: Int -> Char */ func foo(cb) And to be fair, it's usually neat enough. But it gets into trouble when I need to pass some complex structure. The problem being partly due to the lack of type system: /** * cb: Int -> { err: String -> (), success: () -> Char } // too long... */ func foo(cb) Or I have tried this too: /** * cb: Int -> { err: String -> (), * success: () -> Char } // better ? */ func bar(cb) The problem is that you may put the structure in somewhere else, but you must give it a name to reference it. But then when you name a structure you're about to use immediately looks so redundant: // Somewhere else... // ResultCallback: { err: String -> (), success: () -> Char } /** * cb: Int -> ResultCallback // better ?? */ func foo(cb) And it bothers me if I follow the Java-doc like commenting style since it still seems incomplete. The comments don't tell you anything that you couldn't immediately see from looking at the function. /** * @param cb {Function} yeah, it's a function, but you told me nothing about it... * @param err {Function} where should I put this callback's argument ?? * Not to mention the err's own arguments... */ func foo(cb) These examples are JavaScript like with generic functions and parameter names, but I've encountered similar problems in other dynamic languages which allow complex callbacks.

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• LibGDX - SpriteBatch's .draw() method requiring float[]

  - by just_a_programmer

  Please excuse my lack of knowledge with LibGDX, as I have just started learning it. I am going through some simple tutorials, and in one of them, I draw a string onto the screen like so: // the following code is in the main file in the core project folder: // this is in the create() method: private SpriteBatch batch; batch = new SpriteBatch(); // this is in the render() method: batch.draw(batch, "Hello world", 200, 200); I am getting an error saying: The method draw(texture, float[], int, int) in the type SpriteBatch is not applicable for the arguments (SpriteBatch, int, int) So, LibGDX wants a float array to draw instead of a string? Thanks in advance.

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• Collaborative Whiteboard using WebSocket in GlassFish 4 - Text/JSON and Binary/ArrayBuffer Data Transfer (TOTD #189)

  - by arungupta

  This blog has published a few blogs on using JSR 356 Reference Implementation (Tyrus) as its integrated in GlassFish 4 promoted builds. TOTD #183: Getting Started with WebSocket in GlassFish TOTD #184: Logging WebSocket Frames using Chrome Developer Tools, Net-internals and Wireshark TOTD #185: Processing Text and Binary (Blob, ArrayBuffer, ArrayBufferView) Payload in WebSocket TOTD #186: Custom Text and Binary Payloads using WebSocket One of the typical usecase for WebSocket is online collaborative games. This Tip Of The Day (TOTD) explains a sample that can be used to build such games easily. The application is a collaborative whiteboard where different shapes can be drawn in multiple colors. The shapes drawn on one browser are automatically drawn on all other peer browsers that are connected to the same endpoint. The shape, color, and coordinates of the image are transfered using a JSON structure. A browser may opt-out of sharing the figures. Alternatively any browser can send a snapshot of their existing whiteboard to all other browsers. Take a look at this video to understand how the application work and the underlying code. The complete sample code can be downloaded here. The code behind the application is also explained below. The web page (index.jsp) has a HTML5 Canvas as shown: <canvas id="myCanvas" width="150" height="150" style="border:1px solid #000000;"></canvas> And some radio buttons to choose the color and shape. By default, the shape, color, and coordinates of any figure drawn on the canvas are put in a JSON structure and sent as a message to the WebSocket endpoint. The JSON structure looks like: { "shape": "square", "color": "#FF0000", "coords": { "x": 31.59999942779541, "y": 49.91999053955078 }} The endpoint definition looks like: @WebSocketEndpoint(value = "websocket",encoders = {FigureDecoderEncoder.class},decoders = {FigureDecoderEncoder.class})public class Whiteboard { As you can see, the endpoint has decoder and encoder registered that decodes JSON to a Figure (a POJO class) and vice versa respectively. The decode method looks like: public Figure decode(String string) throws DecodeException { try { JSONObject jsonObject = new JSONObject(string); return new Figure(jsonObject); } catch (JSONException ex) { throw new DecodeException("Error parsing JSON", ex.getMessage(), ex.fillInStackTrace()); }} And the encode method looks like: public String encode(Figure figure) throws EncodeException { return figure.getJson().toString();} FigureDecoderEncoder implements both decoder and encoder functionality but thats purely for convenience. But the recommended design pattern is to keep them in separate classes. In certain cases, you may even need only one of them. On the client-side, the Canvas is initialized as: var canvas = document.getElementById("myCanvas");var context = canvas.getContext("2d");canvas.addEventListener("click", defineImage, false); The defineImage method constructs the JSON structure as shown above and sends it to the endpoint using websocket.send(). An instant snapshot of the canvas is sent using binary transfer with WebSocket. The WebSocket is initialized as: var wsUri = "ws://localhost:8080/whiteboard/websocket";var websocket = new WebSocket(wsUri);websocket.binaryType = "arraybuffer"; The important part is to set the binaryType property of WebSocket to arraybuffer. This ensures that any binary transfers using WebSocket are done using ArrayBuffer as the default type seem to be blob. The actual binary data transfer is done using the following: var image = context.getImageData(0, 0, canvas.width, canvas.height);var buffer = new ArrayBuffer(image.data.length);var bytes = new Uint8Array(buffer);for (var i=0; i<bytes.length; i++) { bytes[i] = image.data[i];}websocket.send(bytes); This comprehensive sample shows the following features of JSR 356 API: Annotation-driven endpoints Send/receive text and binary payload in WebSocket Encoders/decoders for custom text payload In addition, it also shows how images can be captured and drawn using HTML5 Canvas in a JSP. How could this be turned in to an online game ? Imagine drawing a Tic-tac-toe board on the canvas with two players playing and others watching. Then you can build access rights and controls within the application itself. Instead of sending a snapshot of the canvas on demand, a new peer joining the game could be automatically transferred the current state as well. Do you want to build this game ? I built a similar game a few years ago. Do somebody want to rewrite the game using WebSocket APIs ? :-) Many thanks to Jitu and Akshay for helping through the WebSocket internals! Here are some references for you: JSR 356: Java API for WebSocket - Specification (Early Draft) and Implementation (already integrated in GlassFish 4 promoted builds) Subsequent blogs will discuss the following topics (not necessary in that order) ... Error handling Interface-driven WebSocket endpoint Java client API Client and Server configuration Security Subprotocols Extensions Other topics from the API

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• Using Google Analytics to determine how much time a visitor spends in each section of my site

  - by flossfan

  I have a site with various pages, like: /about/history /about/team /contact/email-us /contact I want to figure out how much time people are spending on the entire /about section, and how much on the /contact section. If I run a query on the Google Analytics API and set the dimension to ga:pagePathLevel1 and the metric to ga:avgTimeOnPage, I get results like this: { pagePathLevel1: /about, avgTimeOnPage: 28 }, { pagePathLevel1: /contact, avgTimeOnPage: 10 } This looks roughly like what I want, but I'm not sure how to intepret it: Is the value of avgTimeOnPage the average time spent by any user on all pages that match that path? Or is it the average time spent by any user on any single page that matches that path? I'm looking for the average time spent across all pages matching that path, but the time estimates look shorter than I'd expect.

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