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Search found 283 results on 12 pages for 'benjamin dobnikar'.

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  • Installing Mercurial on Mac OS X 10.6 Snow Leopard

    - by Matthew Rankin
    Installing Mercurial on Mac OS X 10.6 Snow Leopard I installed Mercurial 1.3.1 on Mac OS X 10.6 Snow Leopard from source using the following: cd ~/src curl -O http://mercurial.selenic.com/release/mercurial-1.3.1.tar.gz tar xzvf mercurial-1.3.1.tar.gz cd mercurial-1.3.1 make ALL sudo make install This installs the site-packages files for Mercurial in /usr/local/lib/python2.6/site-packages/. I know that installing Mercurial from the Mac Disk Image will install the files into /Library/Python/2.6/site-packages/, which is the site-packages directory for the Mac OS X default Python install. I have Python 2.6.2+ installed as a Framework with its site-packages directory in: /Library/Frameworks/Python.framework/Versions/2.6/lib/python2.6/site-packages With Mercurial installed this way, I have to issue: PYTHONPATH=/usr/local/lib/python2.6/site-packages:"${PYTHONPATH}" in order to get Mercurial to work. Questions How can I install Mercurial from source with the site-packages in a different directory? Is there an advantage or disadvantage to having the site-packages in the current location? Would it be better in one of the Python site-package directories that already exist? Do I need to be concerned about virtualenv working correctly since I have modified PYTHONPATH (or any other conflicts for that matter)? Reasons for Installing from Source Dan Benjamin of Hivelogic provides the benefits of and instructions for installing Mercurial from source in his article Installing Mercurial on Snow Leopard.

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  • Saxon XSLT-Transformation: How to change serialization of an empty tag from <x/> to <x></x>?

    - by Ben
    Hello folks! I do some XSLT-Transformation using Saxon HE 9.2 with the output later being unmarshalled by Castor 1.3.1. The whole thing runs with Java at the JDK 6. My XSLT-Transformation looks like this: <xsl:transform version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform" xmlns:ns="http://my/own/custom/namespace/for/the/target/document"> <xsl:output method="xml" encoding="UTF-8" indent="no" /> <xsl:template match="/"> <ns:item> <ns:property name="id"> <xsl:value-of select="/some/complicated/xpath" /> </ns:property> <!-- ... more ... --> </xsl:template> So the thing is: if the XPath-expression /some/complicated/xpath evaluates to an empty sequence, the Saxon serializer writes <ns:property/> instead of <ns:property></ns:property>. This, however, confuses the Castor unmarshaller, which is next in the pipeline and which unmarshals the output of the transformation to instances of XSD-generated Java-code. So my question is: How can I tell the Saxon-serializer to output empty tags not as standalone tags? Here is what I am proximately currently doing to execute the transformation: import net.sf.saxon.s9api.*; import javax.xml.transform.*; import javax.xml.transform.sax.SAXSource; // ... // read data XMLReader xmlReader = XMLReaderFactory.createXMLReader(); // ... there is some more setting up the xmlReader here ... InputStream xsltStream = new FileInputStream(xsltFile); InputStream inputStream = new FileInputStream(inputFile); Source xsltSource = new SAXSource(xmlReader, new InputSource(xsltStream)); Source inputSource = new SAXSource(xmlReader, new InputSource(inputStream)); XdmNode input = processor.newDocumentBuilder().build(inputSource); // initialize transformation configuration Processor processor = new Processor(false); XsltCompiler compiler = processor.newXsltCompiler(); compiler.setErrorListener(this); XsltExecutable executable = compiler.compile(xsltSource); Serializer serializer = new Serializer(); serializer.setOutputProperty(Serializer.Property.METHOD, "xml"); serializer.setOutputProperty(Serializer.Property.INDENT, "no"); serializer.setOutputStream(output); // execute transformation XsltTransformer transformer = executable.load(); transformer.setInitialContextNode(input); transformer.setErrorListener(this); transformer.setDestination(serializer); transformer.setSchemaValidationMode(ValidationMode.STRIP); transformer.transform(); I'd appreciate any hint pointing in the direction of a solution. :-) In case of any unclarity I'd be happy to give more details. Nightly greetings from Germany, Benjamin

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  • Subband decomposition using Daubechies filter

    - by misha
    I have the following two 8-tap filters: h0 ['-0.010597', '0.032883', '0.030841', '-0.187035', '-0.027984', '0.630881', '0.714847', '0.230378'] h1 ['-0.230378', '0.714847', '-0.630881', '-0.027984', '0.187035', '0.030841', '-0.032883', '-0.010597'] Here they are on a graph: I'm using it to obtain the approximation (lower subband of an image). This is a(m,n) in the following diagram: I got the coefficients and diagram from the book Digital Image Processing, 3rd Edition, so I trust that they are correct. The star symbol denotes one dimensional convolution (either over rows or over columns). The down arrow denotes downsampling in one dimension (either over rows, or columns). My problem is that the filter coefficients for h0 and h1 sum to greater than 1 (approximately 1.4 or sqrt(2) to be exact). Naturally, if I convolve any image with the filter, the image will get brighter. Indeed, here's what I get (expected result on right): Can somebody suggest what the problem is here? Why should it work if the convolution filter coefficients sum to greater than 1? I have the source code, but it's quite long so I'm hoping to avoid posting it here. If it's absolutely necessary, I'll put it up later. EDIT What I'm doing is: Decompose into subbands Filter one of the subbands Recompose subbands into original image Note that the point isn't just to have a displayable subband-decomposed image -- I have to be able to perfectly reconstruct the original image from the subbands as well. So if I scale the filtered image in order to compensate for my decomposition filter making the image brighter, this is what I will have to do: Decompose into subbands Apply intensity scaling Filter one of the subbands Apply inverse intensity scaling Recompose subbands into original image Step 2 performs the scaling. This is what @Benjamin is suggesting. The problem is that then step 4 becomes necessary, or the original image will not be properly reconstructed. This longer method will work. However, the textbook explicitly says that no scaling is performed on the approximation subband. Of course, it's possible that the textbook is wrong. However, what's more possible is I'm misunderstanding something about the way this all works -- this is why I'm asking this question.

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  • Sharing A Stage: JDeveloper/ADF & NetBeans/Java EE 6?

    - by Geertjan
    A highlight for me during last week's Oracle Developer Day in Romania (which I blogged about here) was meeting Jernej Kaše (who is from Slovenia, just like my philosopher hero Slavoj Žižek), who is an Oracle Fusion Middleware evangelist. At the conference, while I was presenting NetBeans and Java EE 6 in one room, Jernej was presenting JDeveloper and ADF in another room. The application he created looks as follows, i.e., a realistic CRUD app, with a master/detail view, a search feature, and validation: In a conversation during a break, we started imagining a scenario where the two of us would be on the same stage, taking turns talking about NetBeans/Java EE and JDeveloper/ADF. In that way, attendees at a conference wouldn't need to choose which of the two topics to attend, because they'd be handled in the same session, with the session possibly being longer so that sufficient time could be spent on the respective technologies. (The JDeveloper/ADF session would then not be competing with the NetBeans/Java EE 6 session, since they'd be handled simultaneously.) The session would focus on the similarities/differences between the two respective tools/solutions, which would be extremely interesting and also unique. The crucial question in making this kind of co-presentation possible is whether (and how quickly) an application such as the one created above with JDeveloper/ADF could be created with NetBeans/Java EE 6. The NetBeans/Java EE 6 story is extremely strong on the model and controler levels, but less strong on the view layer. Though there are choices between using PrimeFaces, RichFaces, and IceFaces, that support is quite limited in the absence of a visual designer or of other specific tools (e.g., code generators to generate snippets of PrimeFaces) connected to JSF component libraries. However, it so happens that in recent months we at NetBeans have established really good connections with the PrimeFaces team (more about that another time). So I asked them what it would take to write the above UI in PrimeFaces. The PrimeFaces team were very helpful. They sent me the following screenshot, which is of the UI they created in PrimeFaces, reproducing the ADF screenshot above: Of course, the above is purely the UI layer, there's no EJB and entity classes and data connection hooked into it yet. However, this is the Facelets file that the PrimeFaces team sent me, i.e., using the PrimeFaces component library, that produces the above result: <?xml version="1.0" encoding="UTF-8"?> <!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> <html xmlns="http://www.w3.org/1999/xhtml" xmlns:h="http://java.sun.com/jsf/html" xmlns:f="http://java.sun.com/jsf/core" xmlns:p="http://primefaces.org/ui"> <f:view> <h:head> <style type="text/css"> .alignRight { text-align: right; } .alignLeft { text-align: left; } .alignTop { vertical-align: top; } .ui-validation-required { color: red; font-size: 14px; margin-right: 5px; position: relative; vertical-align: top; } .ui-selectonemenu .ui-selectonemenu-trigger .ui-icon { margin-top: 7px !important; } </style> </h:head> <h:body> <h:form prependId="false" id="form"> <p:panel header="Employees"> <h:panelGrid columns="4" id="searchPanel"> Search <p:selectOneMenu> <f:selectItem itemLabel="FirstName" itemValue="FirstName" /> <f:selectItem itemLabel="LastName" itemValue="LastName" /> <f:selectItem itemLabel="Email" itemValue="Email" /> <f:selectItem itemLabel="PhoneNumber" itemValue="PhoneNumber" /> </p:selectOneMenu> <p:inputText /> <p:commandLink process="searchPanel" update="@form"> <h:graphicImage name="next.gif" library="img" /> </p:commandLink> </h:panelGrid> <h:panelGrid columns="3" columnClasses="alignTop,,alignTop" style="width:90%;margin-left:10%"> <h:panelGrid columns="2" columnClasses="alignRight,alignLeft"> <h:outputLabel for="firstName">FirstName</h:outputLabel> <p:inputText id="firstName" /> <h:outputLabel for="lastName"> <sup class="ui-validation-required">*</sup>LastName </h:outputLabel> <p:inputText id="lastName" style="width:250px;" /> <h:outputLabel for="email"> <sup class="ui-validation-required">*</sup>Email </h:outputLabel> <p:inputText id="email" style="width:250px;" /> <h:outputLabel for="phoneNumber" value="PhoneNumber" /> <p:inputMask id="phoneNumber" mask="999.999.9999" /> <h:outputLabel for="hireDate"> <sup class="ui-validation-required">*</sup>HireDate</h:outputLabel> <p:calendar id="hireDate" pattern="MM/dd/yyyy" showOn="button" /> </h:panelGrid> <p:outputPanel style="min-width:40px;" /> <h:panelGrid columns="2" columnClasses="alignRight,alignLeft"> <h:outputLabel for="jobId"> <sup class="ui-validation-required">*</sup>JobId </h:outputLabel> <p:selectOneMenu id="jobId" > <f:selectItem itemLabel="Administration Vice President" itemValue="Administration Vice President" /> <f:selectItem itemLabel="Vice President" itemValue="Vice President" /> </p:selectOneMenu> <h:outputLabel for="salary">Salary</h:outputLabel> <p:inputText id="salary" styleClass="alignRight" /> <h:outputLabel for="commissionPct">CommissionPct</h:outputLabel> <p:inputText id="commissionPct" style="width:30px;" maxlength="3" /> <h:outputLabel for="manager">ManagerId</h:outputLabel> <p:selectOneMenu id="manager"> <f:selectItem itemLabel="Steven King" itemValue="Steven" /> <f:selectItem itemLabel="Michael Cook" itemValue="Michael" /> <f:selectItem itemLabel="John Benjamin" itemValue="John" /> <f:selectItem itemLabel="Dav Glass" itemValue="Dav" /> </p:selectOneMenu> <h:outputLabel for="department">DepartmentId</h:outputLabel> <p:selectOneMenu id="department"> <f:selectItem itemLabel="90" itemValue="90" /> <f:selectItem itemLabel="80" itemValue="80" /> <f:selectItem itemLabel="70" itemValue="70" /> <f:selectItem itemLabel="60" itemValue="60" /> <f:selectItem itemLabel="50" itemValue="50" /> <f:selectItem itemLabel="40" itemValue="40" /> <f:selectItem itemLabel="30" itemValue="30" /> <f:selectItem itemLabel="20" itemValue="20" /> </p:selectOneMenu> </h:panelGrid> </h:panelGrid> <p:outputPanel id="buttonPanel"> <p:commandButton value="First" process="@this" update="@form" /> <p:commandButton value="Previous" process="@this" update="@form" style="margin-left:15px;" /> <p:commandButton value="Next" process="@this" update="@form" style="margin-left:15px;" /> <p:commandButton value="Last" process="@this" update="@form" style="margin-left:15px;" /> </p:outputPanel> <p:tabView style="margin-top:25px"> <p:tab title="Job History"> <p:dataTable var="history"> <p:column headerText="StartDate"> <h:outputText value="#{history.startDate}"> <f:convertDateTime pattern="MM/dd/yyyy" /> </h:outputText> </p:column> <p:column headerText="EndDate"> <h:outputText value="#{history.endDate}"> <f:convertDateTime pattern="MM/dd/yyyy" /> </h:outputText> </p:column> <p:column headerText="JobId"> <h:outputText value="#{history.jobId}" /> </p:column> <p:column headerText="DepartmentId"> <h:outputText value="#{history.departmentIdId}" /> </p:column> </p:dataTable> </p:tab> </p:tabView> </p:panel> </h:form> </h:body> </f:view> </html> Right now, NetBeans IDE only has code completion to create the above. So there's not much help for creating such a UI right now. I don't believe that a visual designer is mandatory to create the above. A few code generators and file templates could do the job too. And I'm looking forward to seeing those kinds of tools for PrimeFaces, as well as other JSF component libraries, appearing in NetBeans IDE in upcoming releases. A related option would be for the NetBeans generated CRUD app to include the option of having a master/detail view, as well as the option of having a search feature, i.e., the application generators would provide the option of having additional features typical in Java enterprise apps. In the absence of such tools, there still is room, I believe, for NetBeans/Java EE and JDeveloper/ADF sharing a stage at a conference. The above file would have been prepared up front and the presenter would state that fact. The UI layer is only one aspect of a Java EE 6 application, so that the presenter would have ample other features to show (i.e., the entity class generation, the tools for working with servlets, with session beans, etc) prior to getting to the point where the statement would be made: "On the UI layer, I have prepared this Facelets file, which I will now show you can be connected to the lower layers of the application as follows." At that point, the session beans could be hooked into the Facelets file, the file would be saved, the browser refreshed, and then the whole application would work exactly as the ADF application does. So, Jernej, let's share a stage soon!

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  • The Java Specialist: An Interview with Java Champion Heinz Kabutz

    - by Janice J. Heiss
    Dr. Heinz Kabutz is well known for his Java Specialists’ Newsletter, initiated in November 2000, where he displays his acute grasp of the intricacies of the Java platform for an estimated 70,000 readers; for his work as a consultant; and for his workshops and trainings at his home on the Island of Crete where he has lived since 2006 -- where he is known to curl up on the beach with his laptop to hack away, in between dips in the Mediterranean. Kabutz was born of German parents and raised in Cape Town, South Africa, where he developed a love of programming in junior high school through his explorations on a ZX Spectrum computer. He received a B.S. from the University of Cape Town, and at 25, a Ph.D., both in computer science. He will be leading a two-hour hands-on lab session, HOL6500 – “Finding and Solving Java Deadlocks,” at this year’s JavaOne that will explore what causes deadlocks and how to solve them. Q: Tell us about your JavaOne plans.A: I am arriving on Sunday evening and have just one hands-on-lab to do on Monday morning. This is the first time that a non-Oracle team is doing a HOL at JavaOne under Oracle's stewardship and we are all a bit nervous about how it will turn out. Oracle has been immensely helpful in getting us set up. I have a great team helping me: Kirk Pepperdine, Dario Laverde, Benjamin Evans and Martijn Verburg from jClarity, Nathan Reynolds from Oracle, Henri Tremblay of OCTO Technology and Jeff Genender of Savoir Technologies. Monday will be hard work, but after that, I will hopefully get to network with fellow Java experts, attend interesting sessions and just enjoy San Francisco. Oh, and my kids have already given me a shopping list of things to get, like a GoPro Hero 2 dive housing for shooting those nice videos of Crete. (That's me at the beginning diving down.) Q: What sessions are you attending that we should know about?A: Sometimes the most unusual sessions are the best. I avoid the "big names". They often are spread too thin with all their sessions, which makes it difficult for them to deliver what I would consider deep content. I also avoid entertainers who might be good at presenting but who do not say that much.In 2010, I attended a session by Vladimir Yaroslavskiy where he talked about sorting. Although he struggled to speak English, what he had to say was spectacular. There was hardly anybody in the room, having not heard of Vladimir before. To me that was the highlight of 2010. Funnily enough, he was supposed to speak with Joshua Bloch, but if you remember, Google cancelled. If Bloch has been there, the room would have been packed to capacity.Q: Give us an update on the Java Specialists’ Newsletter.A: The Java Specialists' Newsletter continues being read by an elite audience around the world. The apostrophe in the name is significant.  It is a newsletter for Java specialists. When I started it twelve years ago, I was trying to find non-obvious things in Java to write about. Things that would be interesting to an advanced audience.As an April Fool's joke, I told my readers in Issue 44 that subscribing would remain free, but that they would have to pay US$5 to US$7 depending on their geographical location. I received quite a few angry emails from that one. I would have not earned that much from unsubscriptions. Most readers stay for a very long time.After Oracle bought Sun, the Java community held its breath for about two years whilst Oracle was figuring out what to do with Java. For a while, we were quite concerned that there was not much progress shown by Oracle. My newsletter still continued, but it was quite difficult finding new things to write about. We have probably about 70,000 readers, which is quite a small number for a Java publication. However, our readers are the top in the Java industry. So I don't mind having "only" 70000 readers, as long as they are the top 0.7%.Java concurrency is a very important topic that programmers think they should know about, but often neglect to fully understand. I continued writing about that and made some interesting discoveries. For example, in Issue 165, I showed how we can get thread starvation with the ReadWriteLock. This was a bug in Java 5, which was corrected in Java 6, but perhaps a bit too much. Whereas we could get starvation of writers in Java 5, in Java 6 we could now get starvation of readers. All of these interesting findings make their way into my courseware to help companies avoid these pitfalls.Another interesting discovery was how polymorphism works in the Server HotSpot compiler in Issue 157 and Issue 158. HotSpot can inline methods from interfaces that have only one implementation class in the JVM. When a new subclass is instantiated and called for the first time, the JVM will undo the previous optimization and re-optimize differently.Here is a little memory puzzle for your readers: public class JavaMemoryPuzzle {  private final int dataSize =      (int) (Runtime.getRuntime().maxMemory() * 0.6);  public void f() {    {      byte[] data = new byte[dataSize];    }    byte[] data2 = new byte[dataSize];  }  public static void main(String[] args) {    JavaMemoryPuzzle jmp = new JavaMemoryPuzzle();    jmp.f();  }}When you run this you will always get an OutOfMemoryError, even though the local variable data is no longer visible outside of the code block.So here comes the puzzle, that I'd like you to ponder a bit. If you very politely ask the VM to release memory, then you don't get an OutOfMemoryError: public class JavaMemoryPuzzlePolite {  private final int dataSize =      (int) (Runtime.getRuntime().maxMemory() * 0.6);  public void f() {    {      byte[] data = new byte[dataSize];    }    for(int i=0; i<10; i++) {      System.out.println("Please be so kind and release memory");    }    byte[] data2 = new byte[dataSize];  }  public static void main(String[] args) {    JavaMemoryPuzzlePolite jmp = new JavaMemoryPuzzlePolite();    jmp.f();    System.out.println("No OutOfMemoryError");  }}Why does this work? When I published this in my newsletter, I received over 400 emails from excited readers around the world, most of whom sent me the wrong explanation. After the 300th wrong answer, my replies became unfortunately a bit curt. Have a look at Issue 174 for a detailed explanation, but before you do, put on your thinking caps and try to figure it out yourself. Q: What do you think Java developers should know that they currently do not know?A: They should definitely get to know more about concurrency. It is a tough subject that most programmers try to avoid. Unfortunately we do come in contact with it. And when we do, we need to know how to protect ourselves and how to solve tricky system errors.Knowing your IDE is also useful. Most IDEs have a ton of shortcuts, which can make you a lot more productive in moving code around. Another thing that is useful is being able to read GC logs. Kirk Pepperdine has a great talk at JavaOne that I can recommend if you want to learn more. It's this: CON5405 – “Are Your Garbage Collection Logs Speaking to You?” Q: What are you looking forward to in Java 8?A: I'm quite excited about lambdas, though I must confess that I have not studied them in detail yet. Maurice Naftalin's Lambda FAQ is quite a good start to document what you can do with them. I'm looking forward to finding all the interesting bugs that we will now get due to lambdas obscuring what is really going on underneath, just like we had with generics.I am quite impressed with what the team at Oracle did with OpenJDK's performance. A lot of the benchmarks now run faster.Hopefully Java 8 will come with JSR 310, the Date and Time API. It still boggles my mind that such an important API has been left out in the cold for so long.What I am not looking forward to is losing perm space. Even though some systems run out of perm space, at least the problem is contained and they usually manage to work around it. In most cases, this is due to a memory leak in that region of memory. Once they bundle perm space with the old generation, I predict that memory leaks in perm space will be harder to find. More contracts for us, but also more pain for our customers. Originally published on blogs.oracle.com/javaone.

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  • The Java Specialist: An Interview with Java Champion Heinz Kabutz

    - by Janice J. Heiss
    Dr. Heinz Kabutz is well known for his Java Specialists’ Newsletter, initiated in November 2000, where he displays his acute grasp of the intricacies of the Java platform for an estimated 70,000 readers; for his work as a consultant; and for his workshops and trainings at his home on the Island of Crete where he has lived since 2006 -- where he is known to curl up on the beach with his laptop to hack away, in between dips in the Mediterranean. Kabutz was born of German parents and raised in Cape Town, South Africa, where he developed a love of programming in junior high school through his explorations on a ZX Spectrum computer. He received a B.S. from the University of Cape Town, and at 25, a Ph.D., both in computer science. He will be leading a two-hour hands-on lab session, HOL6500 – “Finding and Solving Java Deadlocks,” at this year’s JavaOne that will explore what causes deadlocks and how to solve them. Q: Tell us about your JavaOne plans.A: I am arriving on Sunday evening and have just one hands-on-lab to do on Monday morning. This is the first time that a non-Oracle team is doing a HOL at JavaOne under Oracle's stewardship and we are all a bit nervous about how it will turn out. Oracle has been immensely helpful in getting us set up. I have a great team helping me: Kirk Pepperdine, Dario Laverde, Benjamin Evans and Martijn Verburg from jClarity, Nathan Reynolds from Oracle, Henri Tremblay of OCTO Technology and Jeff Genender of Savoir Technologies. Monday will be hard work, but after that, I will hopefully get to network with fellow Java experts, attend interesting sessions and just enjoy San Francisco. Oh, and my kids have already given me a shopping list of things to get, like a GoPro Hero 2 dive housing for shooting those nice videos of Crete. (That's me at the beginning diving down.) Q: What sessions are you attending that we should know about?A: Sometimes the most unusual sessions are the best. I avoid the "big names". They often are spread too thin with all their sessions, which makes it difficult for them to deliver what I would consider deep content. I also avoid entertainers who might be good at presenting but who do not say that much.In 2010, I attended a session by Vladimir Yaroslavskiy where he talked about sorting. Although he struggled to speak English, what he had to say was spectacular. There was hardly anybody in the room, having not heard of Vladimir before. To me that was the highlight of 2010. Funnily enough, he was supposed to speak with Joshua Bloch, but if you remember, Google cancelled. If Bloch has been there, the room would have been packed to capacity.Q: Give us an update on the Java Specialists’ Newsletter.A: The Java Specialists' Newsletter continues being read by an elite audience around the world. The apostrophe in the name is significant.  It is a newsletter for Java specialists. When I started it twelve years ago, I was trying to find non-obvious things in Java to write about. Things that would be interesting to an advanced audience.As an April Fool's joke, I told my readers in Issue 44 that subscribing would remain free, but that they would have to pay US$5 to US$7 depending on their geographical location. I received quite a few angry emails from that one. I would have not earned that much from unsubscriptions. Most readers stay for a very long time.After Oracle bought Sun, the Java community held its breath for about two years whilst Oracle was figuring out what to do with Java. For a while, we were quite concerned that there was not much progress shown by Oracle. My newsletter still continued, but it was quite difficult finding new things to write about. We have probably about 70,000 readers, which is quite a small number for a Java publication. However, our readers are the top in the Java industry. So I don't mind having "only" 70000 readers, as long as they are the top 0.7%.Java concurrency is a very important topic that programmers think they should know about, but often neglect to fully understand. I continued writing about that and made some interesting discoveries. For example, in Issue 165, I showed how we can get thread starvation with the ReadWriteLock. This was a bug in Java 5, which was corrected in Java 6, but perhaps a bit too much. Whereas we could get starvation of writers in Java 5, in Java 6 we could now get starvation of readers. All of these interesting findings make their way into my courseware to help companies avoid these pitfalls.Another interesting discovery was how polymorphism works in the Server HotSpot compiler in Issue 157 and Issue 158. HotSpot can inline methods from interfaces that have only one implementation class in the JVM. When a new subclass is instantiated and called for the first time, the JVM will undo the previous optimization and re-optimize differently.Here is a little memory puzzle for your readers: public class JavaMemoryPuzzle {  private final int dataSize =      (int) (Runtime.getRuntime().maxMemory() * 0.6);  public void f() {    {      byte[] data = new byte[dataSize];    }    byte[] data2 = new byte[dataSize];  }  public static void main(String[] args) {    JavaMemoryPuzzle jmp = new JavaMemoryPuzzle();    jmp.f();  }}When you run this you will always get an OutOfMemoryError, even though the local variable data is no longer visible outside of the code block.So here comes the puzzle, that I'd like you to ponder a bit. If you very politely ask the VM to release memory, then you don't get an OutOfMemoryError: public class JavaMemoryPuzzlePolite {  private final int dataSize =      (int) (Runtime.getRuntime().maxMemory() * 0.6);  public void f() {    {      byte[] data = new byte[dataSize];    }    for(int i=0; i<10; i++) {      System.out.println("Please be so kind and release memory");    }    byte[] data2 = new byte[dataSize];  }  public static void main(String[] args) {    JavaMemoryPuzzlePolite jmp = new JavaMemoryPuzzlePolite();    jmp.f();    System.out.println("No OutOfMemoryError");  }}Why does this work? When I published this in my newsletter, I received over 400 emails from excited readers around the world, most of whom sent me the wrong explanation. After the 300th wrong answer, my replies became unfortunately a bit curt. Have a look at Issue 174 for a detailed explanation, but before you do, put on your thinking caps and try to figure it out yourself. Q: What do you think Java developers should know that they currently do not know?A: They should definitely get to know more about concurrency. It is a tough subject that most programmers try to avoid. Unfortunately we do come in contact with it. And when we do, we need to know how to protect ourselves and how to solve tricky system errors.Knowing your IDE is also useful. Most IDEs have a ton of shortcuts, which can make you a lot more productive in moving code around. Another thing that is useful is being able to read GC logs. Kirk Pepperdine has a great talk at JavaOne that I can recommend if you want to learn more. It's this: CON5405 – “Are Your Garbage Collection Logs Speaking to You?” Q: What are you looking forward to in Java 8?A: I'm quite excited about lambdas, though I must confess that I have not studied them in detail yet. Maurice Naftalin's Lambda FAQ is quite a good start to document what you can do with them. I'm looking forward to finding all the interesting bugs that we will now get due to lambdas obscuring what is really going on underneath, just like we had with generics.I am quite impressed with what the team at Oracle did with OpenJDK's performance. A lot of the benchmarks now run faster.Hopefully Java 8 will come with JSR 310, the Date and Time API. It still boggles my mind that such an important API has been left out in the cold for so long.What I am not looking forward to is losing perm space. Even though some systems run out of perm space, at least the problem is contained and they usually manage to work around it. In most cases, this is due to a memory leak in that region of memory. Once they bundle perm space with the old generation, I predict that memory leaks in perm space will be harder to find. More contracts for us, but also more pain for our customers.

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  • Introducing Data Annotations Extensions

    - by srkirkland
    Validation of user input is integral to building a modern web application, and ASP.NET MVC offers us a way to enforce business rules on both the client and server using Model Validation.  The recent release of ASP.NET MVC 3 has improved these offerings on the client side by introducing an unobtrusive validation library built on top of jquery.validation.  Out of the box MVC comes with support for Data Annotations (that is, System.ComponentModel.DataAnnotations) and can be extended to support other frameworks.  Data Annotations Validation is becoming more popular and is being baked in to many other Microsoft offerings, including Entity Framework, though with MVC it only contains four validators: Range, Required, StringLength and Regular Expression.  The Data Annotations Extensions project attempts to augment these validators with additional attributes while maintaining the clean integration Data Annotations provides. A Quick Word About Data Annotations Extensions The Data Annotations Extensions project can be found at http://dataannotationsextensions.org/, and currently provides 11 additional validation attributes (ex: Email, EqualTo, Min/Max) on top of Data Annotations’ original 4.  You can find a current list of the validation attributes on the afore mentioned website. The core library provides server-side validation attributes that can be used in any .NET 4.0 project (no MVC dependency). There is also an easily pluggable client-side validation library which can be used in ASP.NET MVC 3 projects using unobtrusive jquery validation (only MVC3 included javascript files are required). On to the Preview Let’s say you had the following “Customer” domain model (or view model, depending on your project structure) in an MVC 3 project: public class Customer { public string Email { get; set; } public int Age { get; set; } public string ProfilePictureLocation { get; set; } } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } When it comes time to create/edit this Customer, you will probably have a CustomerController and a simple form that just uses one of the Html.EditorFor() methods that the ASP.NET MVC tooling generates for you (or you can write yourself).  It should look something like this: With no validation, the customer can enter nonsense for an email address, and then can even report their age as a negative number!  With the built-in Data Annotations validation, I could do a bit better by adding a Range to the age, adding a RegularExpression for email (yuck!), and adding some required attributes.  However, I’d still be able to report my age as 10.75 years old, and my profile picture could still be any string.  Let’s use Data Annotations along with this project, Data Annotations Extensions, and see what we can get: public class Customer { [Email] [Required] public string Email { get; set; }   [Integer] [Min(1, ErrorMessage="Unless you are benjamin button you are lying.")] [Required] public int Age { get; set; }   [FileExtensions("png|jpg|jpeg|gif")] public string ProfilePictureLocation { get; set; } } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } Now let’s try to put in some invalid values and see what happens: That is very nice validation, all done on the client side (will also be validated on the server).  Also, the Customer class validation attributes are very easy to read and understand. Another bonus: Since Data Annotations Extensions can integrate with MVC 3’s unobtrusive validation, no additional scripts are required! Now that we’ve seen our target, let’s take a look at how to get there within a new MVC 3 project. Adding Data Annotations Extensions To Your Project First we will File->New Project and create an ASP.NET MVC 3 project.  I am going to use Razor for these examples, but any view engine can be used in practice.  Now go into the NuGet Extension Manager (right click on references and select add Library Package Reference) and search for “DataAnnotationsExtensions.”  You should see the following two packages: The first package is for server-side validation scenarios, but since we are using MVC 3 and would like comprehensive sever and client validation support, click on the DataAnnotationsExtensions.MVC3 project and then click Install.  This will install the Data Annotations Extensions server and client validation DLLs along with David Ebbo’s web activator (which enables the validation attributes to be registered with MVC 3). Now that Data Annotations Extensions is installed you have all you need to start doing advanced model validation.  If you are already using Data Annotations in your project, just making use of the additional validation attributes will provide client and server validation automatically.  However, assuming you are starting with a blank project I’ll walk you through setting up a controller and model to test with. Creating Your Model In the Models folder, create a new User.cs file with a User class that you can use as a model.  To start with, I’ll use the following class: public class User { public string Email { get; set; } public string Password { get; set; } public string PasswordConfirm { get; set; } public string HomePage { get; set; } public int Age { get; set; } } Next, create a simple controller with at least a Create method, and then a matching Create view (note, you can do all of this via the MVC built-in tooling).  Your files will look something like this: UserController.cs: public class UserController : Controller { public ActionResult Create() { return View(new User()); }   [HttpPost] public ActionResult Create(User user) { if (!ModelState.IsValid) { return View(user); }   return Content("User valid!"); } } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } Create.cshtml: @model NuGetValidationTester.Models.User   @{ ViewBag.Title = "Create"; }   <h2>Create</h2>   <script src="@Url.Content("~/Scripts/jquery.validate.min.js")" type="text/javascript"></script> <script src="@Url.Content("~/Scripts/jquery.validate.unobtrusive.min.js")" type="text/javascript"></script>   @using (Html.BeginForm()) { @Html.ValidationSummary(true) <fieldset> <legend>User</legend> @Html.EditorForModel() <p> <input type="submit" value="Create" /> </p> </fieldset> } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } In the Create.cshtml view, note that we are referencing jquery validation and jquery unobtrusive (jquery is referenced in the layout page).  These MVC 3 included scripts are the only ones you need to enjoy both the basic Data Annotations validation as well as the validation additions available in Data Annotations Extensions.  These references are added by default when you use the MVC 3 “Add View” dialog on a modification template type. Now when we go to /User/Create we should see a form for editing a User Since we haven’t yet added any validation attributes, this form is valid as shown (including no password, email and an age of 0).  With the built-in Data Annotations attributes we can make some of the fields required, and we could use a range validator of maybe 1 to 110 on Age (of course we don’t want to leave out supercentenarians) but let’s go further and validate our input comprehensively using Data Annotations Extensions.  The new and improved User.cs model class. { [Required] [Email] public string Email { get; set; }   [Required] public string Password { get; set; }   [Required] [EqualTo("Password")] public string PasswordConfirm { get; set; }   [Url] public string HomePage { get; set; }   [Integer] [Min(1)] public int Age { get; set; } } .csharpcode, .csharpcode pre { font-size: small; color: black; font-family: consolas, "Courier New", courier, monospace; background-color: #ffffff; /*white-space: pre;*/ } .csharpcode pre { margin: 0em; } .csharpcode .rem { color: #008000; } .csharpcode .kwrd { color: #0000ff; } .csharpcode .str { color: #006080; } .csharpcode .op { color: #0000c0; } .csharpcode .preproc { color: #cc6633; } .csharpcode .asp { background-color: #ffff00; } .csharpcode .html { color: #800000; } .csharpcode .attr { color: #ff0000; } .csharpcode .alt { background-color: #f4f4f4; width: 100%; margin: 0em; } .csharpcode .lnum { color: #606060; } Now let’s re-run our form and try to use some invalid values: All of the validation errors you see above occurred on the client, without ever even hitting submit.  The validation is also checked on the server, which is a good practice since client validation is easily bypassed. That’s all you need to do to start a new project and include Data Annotations Extensions, and of course you can integrate it into an existing project just as easily. Nitpickers Corner ASP.NET MVC 3 futures defines four new data annotations attributes which this project has as well: CreditCard, Email, Url and EqualTo.  Unfortunately referencing MVC 3 futures necessitates taking an dependency on MVC 3 in your model layer, which may be unadvisable in a multi-tiered project.  Data Annotations Extensions keeps the server and client side libraries separate so using the project’s validation attributes don’t require you to take any additional dependencies in your model layer which still allowing for the rich client validation experience if you are using MVC 3. Custom Error Message and Globalization: Since the Data Annotations Extensions are build on top of Data Annotations, you have the ability to define your own static error messages and even to use resource files for very customizable error messages. Available Validators: Please see the project site at http://dataannotationsextensions.org/ for an up-to-date list of the new validators included in this project.  As of this post, the following validators are available: CreditCard Date Digits Email EqualTo FileExtensions Integer Max Min Numeric Url Conclusion Hopefully I’ve illustrated how easy it is to add server and client validation to your MVC 3 projects, and how to easily you can extend the available validation options to meet real world needs. The Data Annotations Extensions project is fully open source under the BSD license.  Any feedback would be greatly appreciated.  More information than you require, along with links to the source code, is available at http://dataannotationsextensions.org/. Enjoy!

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  • Where to find xmoov port to C#? (to make Http Pseudo Streaming from c# app)

    - by Ole Jak
    So I found this beautifull script for FLV video format Http Pseudo Streaming but in is in PHP ( found on http://stream.xmoov.com/ ) So does any one know opensource translations or can translate such PHP code into C#? <?php /* xmoov-php 1.0 Development version 0.9.3 beta by: Eric Lorenzo Benjamin jr. webmaster (AT) xmoov (DOT) com originally inspired by Stefan Richter at flashcomguru.com bandwidth limiting by Terry streamingflvcom (AT) dedicatedmanagers (DOT) com This work is licensed under the Creative Commons Attribution-NonCommercial-ShareAlike 3.0 License. For more information, visit http://creativecommons.org/licenses/by-nc-sa/3.0/ For the full license, visit http://creativecommons.org/licenses/by-nc-sa/3.0/legalcode or send a letter to Creative Commons, 543 Howard Street, 5th Floor, San Francisco, California, 94105, USA. */ // SCRIPT CONFIGURATION //------------------------------------------------------------------------------------------ // MEDIA PATH // // you can configure these settings to point to video files outside the public html folder. //------------------------------------------------------------------------------------------ // points to server root define('XMOOV_PATH_ROOT', ''); // points to the folder containing the video files. define('XMOOV_PATH_FILES', 'video/'); //------------------------------------------------------------------------------------------ // SCRIPT BEHAVIOR //------------------------------------------------------------------------------------------ //set to TRUE to use bandwidth limiting. define('XMOOV_CONF_LIMIT_BANDWIDTH', TRUE); //set to FALSE to prohibit caching of video files. define('XMOOV_CONF_ALLOW_FILE_CACHE', FALSE); //------------------------------------------------------------------------------------------ // BANDWIDTH SETTINGS // // these settings are only needed when using bandwidth limiting. // // bandwidth is limited my sending a limited amount of video data(XMOOV_BW_PACKET_SIZE), // in specified time intervals(XMOOV_BW_PACKET_INTERVAL). // avoid time intervals over 1.5 seconds for best results. // // you can also control bandwidth limiting via http command using your video player. // the function getBandwidthLimit($part) holds three preconfigured presets(low, mid, high), // which can be changed to meet your needs //------------------------------------------------------------------------------------------ //set how many kilobytes will be sent per time interval define('XMOOV_BW_PACKET_SIZE', 90); //set the time interval in which data packets will be sent in seconds. define('XMOOV_BW_PACKET_INTERVAL', 0.3); //set to TRUE to control bandwidth externally via http. define('XMOOV_CONF_ALLOW_DYNAMIC_BANDWIDTH', TRUE); //------------------------------------------------------------------------------------------ // DYNAMIC BANDWIDTH CONTROL //------------------------------------------------------------------------------------------ function getBandwidthLimit($part) { switch($part) { case 'interval' : switch($_GET[XMOOV_GET_BANDWIDTH]) { case 'low' : return 1; break; case 'mid' : return 0.5; break; case 'high' : return 0.3; break; default : return XMOOV_BW_PACKET_INTERVAL; break; } break; case 'size' : switch($_GET[XMOOV_GET_BANDWIDTH]) { case 'low' : return 10; break; case 'mid' : return 40; break; case 'high' : return 90; break; default : return XMOOV_BW_PACKET_SIZE; break; } break; } } //------------------------------------------------------------------------------------------ // INCOMING GET VARIABLES CONFIGURATION // // use these settings to configure how video files, seek position and bandwidth settings are accessed by your player //------------------------------------------------------------------------------------------ define('XMOOV_GET_FILE', 'file'); define('XMOOV_GET_POSITION', 'position'); define('XMOOV_GET_AUTHENTICATION', 'key'); define('XMOOV_GET_BANDWIDTH', 'bw'); // END SCRIPT CONFIGURATION - do not change anything beyond this point if you do not know what you are doing //------------------------------------------------------------------------------------------ // PROCESS FILE REQUEST //------------------------------------------------------------------------------------------ if(isset($_GET[XMOOV_GET_FILE]) && isset($_GET[XMOOV_GET_POSITION])) { // PROCESS VARIABLES # get seek position $seekPos = intval($_GET[XMOOV_GET_POSITION]); # get file name $fileName = htmlspecialchars($_GET[XMOOV_GET_FILE]); # assemble file path $file = XMOOV_PATH_ROOT . XMOOV_PATH_FILES . $fileName; # assemble packet interval $packet_interval = (XMOOV_CONF_ALLOW_DYNAMIC_BANDWIDTH && isset($_GET[XMOOV_GET_BANDWIDTH])) ? getBandwidthLimit('interval') : XMOOV_BW_PACKET_INTERVAL; # assemble packet size $packet_size = ((XMOOV_CONF_ALLOW_DYNAMIC_BANDWIDTH && isset($_GET[XMOOV_GET_BANDWIDTH])) ? getBandwidthLimit('size') : XMOOV_BW_PACKET_SIZE) * 1042; # security improved by by TRUI www.trui.net if (!file_exists($file)) { print('<b>ERROR:</b> xmoov-php could not find (' . $fileName . ') please check your settings.'); exit(); } if(file_exists($file) && strrchr($fileName, '.') == '.flv' && strlen($fileName) > 2 && !eregi(basename($_SERVER['PHP_SELF']), $fileName) && ereg('^[^./][^/]*$', $fileName)) { # stay clean @ob_end_clean(); @set_time_limit(0); # keep binary data safe set_magic_quotes_runtime(0); $fh = fopen($file, 'rb') or die ('<b>ERROR:</b> xmoov-php could not open (' . $fileName . ')'); $fileSize = filesize($file) - (($seekPos > 0) ? $seekPos + 1 : 0); // SEND HEADERS if(!XMOOV_CONF_ALLOW_FILE_CACHE) { # prohibit caching (different methods for different clients) session_cache_limiter("nocache"); header("Expires: Thu, 19 Nov 1981 08:52:00 GMT"); header("Last-Modified: " . gmdate("D, d M Y H:i:s") . " GMT"); header("Cache-Control: no-store, no-cache, must-revalidate, post-check=0, pre-check=0"); header("Pragma: no-cache"); } # content headers header("Content-Type: video/x-flv"); header("Content-Disposition: attachment; filename=\"" . $fileName . "\""); header("Content-Length: " . $fileSize); # FLV file format header if($seekPos != 0) { print('FLV'); print(pack('C', 1)); print(pack('C', 1)); print(pack('N', 9)); print(pack('N', 9)); } # seek to requested file position fseek($fh, $seekPos); # output file while(!feof($fh)) { # use bandwidth limiting - by Terry if(XMOOV_CONF_LIMIT_BANDWIDTH) { # get start time list($usec, $sec) = explode(' ', microtime()); $time_start = ((float)$usec + (float)$sec); # output packet print(fread($fh, $packet_size)); # get end time list($usec, $sec) = explode(' ', microtime()); $time_stop = ((float)$usec + (float)$sec); # wait if output is slower than $packet_interval $time_difference = $time_stop - $time_start; # clean up @flush(); @ob_flush(); if($time_difference < (float)$packet_interval) { usleep((float)$packet_interval * 1000000 - (float)$time_difference * 1000000); } } else { # output file without bandwidth limiting print(fread($fh, filesize($file))); } } } } ?>

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