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• unable to format usb 1204 [daemon inhibited ]

  - by santosamaru

  i try to format my usb 1st time its work all data gone but i can't save any file at this usb . then i try to check is it working or broken here the report santos@santos:~$ sudo badblocks -v /dev/sdb [sudo] password for santos: Sorry, try again. [sudo] password for santos: Checking blocks 0 to 7824383 Checking for bad blocks (read-only test): 0.00% done, 0:00 elapsed. (0/0/0 errdone Pass completed, 0 bad blocks found. (0/0/0 errors) santos@santos:~$ sudo badblocks -v -w /dev/sdb [sudo] password for santos: Sorry, try again. [sudo] password for santos: /dev/sdb is apparently in use by the system; it's not safe to run badblocks! santos@santos:~$ how to format and fix this issues? i have read this link Formatting Pen Drive causes 'Daemon Is Inhibited' Error and it said like this when i try to move any items from desktop " the destination is read only also in this case i use google and find this http://ubuntuforums.org/showthread.php?t=1955353 article as same its not helped following user13509 suggestion ..

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• how to install flash for opera browser? ubuntu 12 04

  - by santosamaru

  for the opera:plugins setting its had been setup as enable to use the flash player .. and also i do trying to follow the instruction from I am testing the new Opera 11, but it keeps telling me I need to install flash player it still not help me .. what i have after following that link instructions is root@santos:/home/santos# cp /usr/lib/flashplugin-installer/libflashplayer.so ~/.opera/plugins/libflashplayer.so cp: cannot create regular file `/root/.opera/plugins/libflashplayer.so': No such file or directory root@santos:/home/santos# sudo apt-get gecko-mediaplayer E: Invalid operation gecko-mediaplayer root@santos:/home/santos# cp /usr/lib/flashplugin-installer/libflashplayer.so ~/.opera/plugins/libflashplayer.so cp: cannot create regular file `/root/.opera/plugins/libflashplayer.so': No such file or directory anyone can help me to solve this ?

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• CMOTECH D-50 modem installation in Ubuntu 12.04

  - by Ricardo

  I have recently upgraded from 10.04 to 12.04. I had installed a 3G D-50 modem from CMOTECH. The program for Debian is provided by a Swedish company (ice.net). Usually after some mambo jambo of installung the libg++ libraries requested you can install it and runned in Ubuntu 8.04, 9.04, 10.04 and as far as I know in 11.04. When I upgraded and I click on the icon of ice.net it worked. However, I noticed that the usb D-50 modem was never mounted as usb and it didn't show up in the Lauchnpad or workspace (as when you plug a usb memory stick or another HD). I moved the icon from place in the launchpad and since when I click on the ice.net icon the same message appears: "please plug in your modem". The modem works (I've tested in Windows after this) and it blinks blue (sign that it works and picks up signal). If I type lsusb then I see that Ubuntu sees it on BUS address 006: Bus 006 Device 003: ID 16d8:6803 CMOTECH Co., Ltd. CNU-680 CDMA EV-DO modem I've tried wvdial without success. How can I get the D-50 usb modem mounted as in the previous versions of Ubuntu ?. Any help will be much appreciated. bests. Ricardo

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• Calculating the Size (in Bytes and MB) of a Oracle Coherence Cache

  - by Ricardo Ferreira

  The concept and usage of data grids are becoming very popular in this days since this type of technology are evolving very fast with some cool lead products like Oracle Coherence. Once for a while, developers need an programmatic way to calculate the total size of a specific cache that are residing in the data grid. In this post, I will show how to accomplish this using Oracle Coherence API. This example has been tested with 3.6, 3.7 and 3.7.1 versions of Oracle Coherence. To start the development of this example, you need to create a POJO ("Plain Old Java Object") that represents a data structure that will hold user data. This data structure will also create an internal fat so I call that should increase considerably the size of each instance in the heap memory. Create a Java class named "Person" as shown in the listing below. package com.oracle.coherence.domain; import java.io.Serializable; import java.util.ArrayList; import java.util.HashMap; import java.util.List; import java.util.Random; @SuppressWarnings("serial") public class Person implements Serializable { private String firstName; private String lastName; private List<Object> fat; private String email; public Person() { generateFat(); } public Person(String firstName, String lastName, String email) { setFirstName(firstName); setLastName(lastName); setEmail(email); generateFat(); } private void generateFat() { fat = new ArrayList<Object>(); Random random = new Random(); for (int i = 0; i < random.nextInt(18000); i++) { HashMap<Long, Double> internalFat = new HashMap<Long, Double>(); for (int j = 0; j < random.nextInt(10000); j++) { internalFat.put(random.nextLong(), random.nextDouble()); } fat.add(internalFat); } } public String getFirstName() { return firstName; } public void setFirstName(String firstName) { this.firstName = firstName; } public String getLastName() { return lastName; } public void setLastName(String lastName) { this.lastName = lastName; } public String getEmail() { return email; } public void setEmail(String email) { this.email = email; } } Now let's create a Java program that will start a data grid into Coherence and will create a cache named "People", that will hold people instances with sequential integer keys. Each person created in this program will trigger the execution of a custom constructor created in the People class that instantiates an internal fat (the random amount of data generated to increase the size of the object) for each person. Create a Java class named "CreatePeopleCacheAndPopulateWithData" as shown in the listing below. package com.oracle.coherence.demo; import com.oracle.coherence.domain.Person; import com.tangosol.net.CacheFactory; import com.tangosol.net.NamedCache; public class CreatePeopleCacheAndPopulateWithData { public static void main(String[] args) { // Asks Coherence for a new cache named "People"... NamedCache people = CacheFactory.getCache("People"); // Creates three people that will be putted into the data grid. Each person // generates an internal fat that should increase its size in terms of bytes... Person pessoa1 = new Person("Ricardo", "Ferreira", "ricardo[email protected]"); Person pessoa2 = new Person("Vitor", "Ferreira", "[email protected]"); Person pessoa3 = new Person("Vivian", "Ferreira", "[email protected]"); // Insert three people at the data grid... people.put(1, pessoa1); people.put(2, pessoa2); people.put(3, pessoa3); // Waits for 5 minutes until the user runs the Java program // that calculates the total size of the people cache... try { System.out.println("---> Waiting for 5 minutes for the cache size calculation..."); Thread.sleep(300000); } catch (InterruptedException ie) { ie.printStackTrace(); } } } Finally, let's create a Java program that, using the Coherence API and JMX, will calculate the total size of each cache that the data grid is currently managing. The approach used in this example was retrieve every cache that the data grid are currently managing, but if you are interested on an specific cache, the same approach can be used, you should only filter witch cache will be looked for. Create a Java class named "CalculateTheSizeOfPeopleCache" as shown in the listing below. package com.oracle.coherence.demo; import java.text.DecimalFormat; import java.util.Map; import java.util.Set; import java.util.TreeMap; import javax.management.MBeanServer; import javax.management.MBeanServerFactory; import javax.management.ObjectName; import com.tangosol.net.CacheFactory; public class CalculateTheSizeOfPeopleCache { @SuppressWarnings({ "unchecked", "rawtypes" }) private void run() throws Exception { // Enable JMX support in this Coherence data grid session... System.setProperty("tangosol.coherence.management", "all"); // Create a sample cache just to access the data grid... CacheFactory.getCache(MBeanServerFactory.class.getName()); // Gets the JMX server from Coherence data grid... MBeanServer jmxServer = getJMXServer(); // Creates a internal data structure that would maintain // the statistics from each cache in the data grid... Map cacheList = new TreeMap(); Set jmxObjectList = jmxServer.queryNames(new ObjectName("Coherence:type=Cache,*"), null); for (Object jmxObject : jmxObjectList) { ObjectName jmxObjectName = (ObjectName) jmxObject; String cacheName = jmxObjectName.getKeyProperty("name"); if (cacheName.equals(MBeanServerFactory.class.getName())) { continue; } else { cacheList.put(cacheName, new Statistics(cacheName)); } } // Updates the internal data structure with statistic data // retrieved from caches inside the in-memory data grid... Set<String> cacheNames = cacheList.keySet(); for (String cacheName : cacheNames) { Set resultSet = jmxServer.queryNames( new ObjectName("Coherence:type=Cache,name=" + cacheName + ",*"), null); for (Object resultSetRef : resultSet) { ObjectName objectName = (ObjectName) resultSetRef; if (objectName.getKeyProperty("tier").equals("back")) { int unit = (Integer) jmxServer.getAttribute(objectName, "Units"); int size = (Integer) jmxServer.getAttribute(objectName, "Size"); Statistics statistics = (Statistics) cacheList.get(cacheName); statistics.incrementUnit(unit); statistics.incrementSize(size); cacheList.put(cacheName, statistics); } } } // Finally... print the objects from the internal data // structure that represents the statistics from caches... cacheNames = cacheList.keySet(); for (String cacheName : cacheNames) { Statistics estatisticas = (Statistics) cacheList.get(cacheName); System.out.println(estatisticas); } } public MBeanServer getJMXServer() { MBeanServer jmxServer = null; for (Object jmxServerRef : MBeanServerFactory.findMBeanServer(null)) { jmxServer = (MBeanServer) jmxServerRef; if (jmxServer.getDefaultDomain().equals(DEFAULT_DOMAIN) || DEFAULT_DOMAIN.length() == 0) { break; } jmxServer = null; } if (jmxServer == null) { jmxServer = MBeanServerFactory.createMBeanServer(DEFAULT_DOMAIN); } return jmxServer; } private class Statistics { private long unit; private long size; private String cacheName; public Statistics(String cacheName) { this.cacheName = cacheName; } public void incrementUnit(long unit) { this.unit += unit; } public void incrementSize(long size) { this.size += size; } public long getUnit() { return unit; } public long getSize() { return size; } public double getUnitInMB() { return unit / (1024.0 * 1024.0); } public double getAverageSize() { return size == 0 ? 0 : unit / size; } public String toString() { StringBuffer sb = new StringBuffer(); sb.append("\nCache Statistics of '").append(cacheName).append("':\n"); sb.append(" - Total Entries of Cache -----> " + getSize()).append("\n"); sb.append(" - Used Memory (Bytes) --------> " + getUnit()).append("\n"); sb.append(" - Used Memory (MB) -----------> " + FORMAT.format(getUnitInMB())).append("\n"); sb.append(" - Object Average Size --------> " + FORMAT.format(getAverageSize())).append("\n"); return sb.toString(); } } public static void main(String[] args) throws Exception { new CalculateTheSizeOfPeopleCache().run(); } public static final DecimalFormat FORMAT = new DecimalFormat("###.###"); public static final String DEFAULT_DOMAIN = ""; public static final String DOMAIN_NAME = "Coherence"; } I've commented the overall example so, I don't think that you should get into trouble to understand it. Basically we are dealing with JMX. The first thing to do is enable JMX support for the Coherence client (ie, an JVM that will only retrieve values from the data grid and will not integrate the cluster) application. This can be done very easily using the runtime "tangosol.coherence.management" system property. Consult the Coherence documentation for JMX to understand the possible values that could be applied. The program creates an in memory data structure that holds a custom class created called "Statistics". This class represents the information that we are interested to see, which in this case are the size in bytes and in MB of the caches. An instance of this class is created for each cache that are currently managed by the data grid. Using JMX specific methods, we retrieve the information that are relevant for calculate the total size of the caches. To test this example, you should execute first the CreatePeopleCacheAndPopulateWithData.java program and after the CreatePeopleCacheAndPopulateWithData.java program. The results in the console should be something like this: 2012-06-23 13:29:31.188/4.970 Oracle Coherence 3.6.0.4 <Info> (thread=Main Thread, member=n/a): Loaded operational configuration from "jar:file:/E:/Oracle/Middleware/oepe_11gR1PS4/workspace/calcular-tamanho-cache-coherence/lib/coherence.jar!/tangosol-coherence.xml" 2012-06-23 13:29:31.219/5.001 Oracle Coherence 3.6.0.4 <Info> (thread=Main Thread, member=n/a): Loaded operational overrides from "jar:file:/E:/Oracle/Middleware/oepe_11gR1PS4/workspace/calcular-tamanho-cache-coherence/lib/coherence.jar!/tangosol-coherence-override-dev.xml" 2012-06-23 13:29:31.219/5.001 Oracle Coherence 3.6.0.4 <D5> (thread=Main Thread, member=n/a): Optional configuration override "/tangosol-coherence-override.xml" is not specified 2012-06-23 13:29:31.266/5.048 Oracle Coherence 3.6.0.4 <D5> (thread=Main Thread, member=n/a): Optional configuration override "/custom-mbeans.xml" is not specified Oracle Coherence Version 3.6.0.4 Build 19111 Grid Edition: Development mode Copyright (c) 2000, 2010, Oracle and/or its affiliates. All rights reserved. 2012-06-23 13:29:33.156/6.938 Oracle Coherence GE 3.6.0.4 <Info> (thread=Main Thread, member=n/a): Loaded Reporter configuration from "jar:file:/E:/Oracle/Middleware/oepe_11gR1PS4/workspace/calcular-tamanho-cache-coherence/lib/coherence.jar!/reports/report-group.xml" 2012-06-23 13:29:33.500/7.282 Oracle Coherence GE 3.6.0.4 <Info> (thread=Main Thread, member=n/a): Loaded cache configuration from "jar:file:/E:/Oracle/Middleware/oepe_11gR1PS4/workspace/calcular-tamanho-cache-coherence/lib/coherence.jar!/coherence-cache-config.xml" 2012-06-23 13:29:35.391/9.173 Oracle Coherence GE 3.6.0.4 <D4> (thread=Main Thread, member=n/a): TCMP bound to /192.168.177.133:8090 using SystemSocketProvider 2012-06-23 13:29:37.062/10.844 Oracle Coherence GE 3.6.0.4 <Info> (thread=Cluster, member=n/a): This Member(Id=2, Timestamp=2012-06-23 13:29:36.899, Address=192.168.177.133:8090, MachineId=55685, Location=process:244, Role=Oracle, Edition=Grid Edition, Mode=Development, CpuCount=2, SocketCount=2) joined cluster "cluster:0xC4DB" with senior Member(Id=1, Timestamp=2012-06-23 13:29:14.031, Address=192.168.177.133:8088, MachineId=55685, Location=process:1128, Role=CreatePeopleCacheAndPopulateWith, Edition=Grid Edition, Mode=Development, CpuCount=2, SocketCount=2) 2012-06-23 13:29:37.172/10.954 Oracle Coherence GE 3.6.0.4 <D5> (thread=Cluster, member=n/a): Member 1 joined Service Cluster with senior member 1 2012-06-23 13:29:37.188/10.970 Oracle Coherence GE 3.6.0.4 <D5> (thread=Cluster, member=n/a): Member 1 joined Service Management with senior member 1 2012-06-23 13:29:37.188/10.970 Oracle Coherence GE 3.6.0.4 <D5> (thread=Cluster, member=n/a): Member 1 joined Service DistributedCache with senior member 1 2012-06-23 13:29:37.188/10.970 Oracle Coherence GE 3.6.0.4 <Info> (thread=Main Thread, member=n/a): Started cluster Name=cluster:0xC4DB Group{Address=224.3.6.0, Port=36000, TTL=4} MasterMemberSet ( ThisMember=Member(Id=2, Timestamp=2012-06-23 13:29:36.899, Address=192.168.177.133:8090, MachineId=55685, Location=process:244, Role=Oracle) OldestMember=Member(Id=1, Timestamp=2012-06-23 13:29:14.031, Address=192.168.177.133:8088, MachineId=55685, Location=process:1128, Role=CreatePeopleCacheAndPopulateWith) ActualMemberSet=MemberSet(Size=2, BitSetCount=2 Member(Id=1, Timestamp=2012-06-23 13:29:14.031, Address=192.168.177.133:8088, MachineId=55685, Location=process:1128, Role=CreatePeopleCacheAndPopulateWith) Member(Id=2, Timestamp=2012-06-23 13:29:36.899, Address=192.168.177.133:8090, MachineId=55685, Location=process:244, Role=Oracle) ) RecycleMillis=1200000 RecycleSet=MemberSet(Size=0, BitSetCount=0 ) ) TcpRing{Connections=[1]} IpMonitor{AddressListSize=0} 2012-06-23 13:29:37.891/11.673 Oracle Coherence GE 3.6.0.4 <D5> (thread=Invocation:Management, member=2): Service Management joined the cluster with senior service member 1 2012-06-23 13:29:39.203/12.985 Oracle Coherence GE 3.6.0.4 <D5> (thread=DistributedCache, member=2): Service DistributedCache joined the cluster with senior service member 1 2012-06-23 13:29:39.297/13.079 Oracle Coherence GE 3.6.0.4 <D4> (thread=DistributedCache, member=2): Asking member 1 for 128 primary partitions Cache Statistics of 'People': - Total Entries of Cache -----> 3 - Used Memory (Bytes) --------> 883920 - Used Memory (MB) -----------> 0.843 - Object Average Size --------> 294640 I hope that this post could save you some time when calculate the total size of Coherence cache became a requirement for your high scalable system using data grids. See you!

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• Enhanced Dynamic Filtering

  - by Ricardo Peres

  Remember my last post on dynamic filtering? Well, this time I'm extending the code in order to allow two levels of querying: Match type, represented by the following options: public enum MatchType { StartsWith = 0, Contains = 1 } And word match: public enum WordMatch { AnyWord = 0, AllWords = 1, ExactPhrase = 2 } You can combine the two levels in order to achieve the following combinations: MatchType.StartsWith + WordMatch.AnyWord Matches any record that starts with any of the words specified MatchType.StartsWith + WordMatch.AllWords Not available: does not make sense, throws an exception MatchType.StartsWith + WordMatch.ExactPhrase Matches any record that starts with the exact specified phrase MatchType.Contains + WordMatch.AnyWord Matches any record that contains any of the specified words MatchType.Contains + WordMatch.AllWords Matches any record that contains all of the specified words MatchType.Contains + WordMatch.ExactPhrase Matches any record that contains the exact specified phrase Here is the code: public static IList Search(IQueryable query, Type entityType, String dataTextField, String phrase, MatchType matchType, WordMatch wordMatch, Int32 maxCount) { String [] terms = phrase.Split(' ').Distinct().ToArray(); StringBuilder result = new StringBuilder(); PropertyInfo displayProperty = entityType.GetProperty(dataTextField); IList searchList = null; MethodInfo orderByMethod = typeof(Queryable).GetMethods(BindingFlags.Public | BindingFlags.Static).Where(m = m.Name == "OrderBy").ToArray() [ 0 ].MakeGenericMethod(entityType, displayProperty.PropertyType); MethodInfo takeMethod = typeof(Queryable).GetMethod("Take", BindingFlags.Public | BindingFlags.Static).MakeGenericMethod(entityType); MethodInfo whereMethod = typeof(Queryable).GetMethods(BindingFlags.Public | BindingFlags.Static).Where(m = m.Name == "Where").ToArray() [ 0 ].MakeGenericMethod(entityType); MethodInfo distinctMethod = typeof(Queryable).GetMethods(BindingFlags.Public | BindingFlags.Static).Where(m = m.Name == "Distinct" && m.GetParameters().Length == 1).Single().MakeGenericMethod(entityType); MethodInfo toListMethod = typeof(Enumerable).GetMethod("ToList", BindingFlags.Static | BindingFlags.Public).MakeGenericMethod(entityType); MethodInfo matchMethod = typeof(String).GetMethod ( (matchType == MatchType.StartsWith) ? "StartsWith" : "Contains", new Type [] { typeof(String) } ); MemberExpression member = Expression.MakeMemberAccess ( Expression.Parameter(entityType, "n"), displayProperty ); MethodCallExpression call = null; LambdaExpression where = null; LambdaExpression orderBy = Expression.Lambda ( member, member.Expression as ParameterExpression ); switch (matchType) { case MatchType.StartsWith: switch (wordMatch) { case WordMatch.AnyWord: call = Expression.Call ( member, matchMethod, Expression.Constant(terms [ 0 ]) ); where = Expression.Lambda ( call, member.Expression as ParameterExpression ); for (Int32 i = 1; i ()); where = Expression.Lambda ( Expression.Or ( where.Body, exp ), where.Parameters.ToArray() ); } break; case WordMatch.ExactPhrase: call = Expression.Call ( member, matchMethod, Expression.Constant(phrase) ); where = Expression.Lambda ( call, member.Expression as ParameterExpression ); break; case WordMatch.AllWords: throw (new Exception("The match type StartsWith is not supported with word match AllWords")); } break; case MatchType.Contains: switch (wordMatch) { case WordMatch.AnyWord: call = Expression.Call ( member, matchMethod, Expression.Constant(terms [ 0 ]) ); where = Expression.Lambda ( call, member.Expression as ParameterExpression ); for (Int32 i = 1; i ()); where = Expression.Lambda ( Expression.Or ( where.Body, exp ), where.Parameters.ToArray() ); } break; case WordMatch.ExactPhrase: call = Expression.Call ( member, matchMethod, Expression.Constant(phrase) ); where = Expression.Lambda ( call, member.Expression as ParameterExpression ); break; case WordMatch.AllWords: call = Expression.Call ( member, matchMethod, Expression.Constant(terms [ 0 ]) ); where = Expression.Lambda ( call, member.Expression as ParameterExpression ); for (Int32 i = 1; i ()); where = Expression.Lambda ( Expression.AndAlso ( where.Body, exp ), where.Parameters.ToArray() ); } break; } break; } query = orderByMethod.Invoke(null, new Object [] { query, orderBy }) as IQueryable; query = whereMethod.Invoke(null, new Object [] { query, where }) as IQueryable; if (maxCount != 0) { query = takeMethod.Invoke(null, new Object [] { query, maxCount }) as IQueryable; } searchList = toListMethod.Invoke(null, new Object [] { query }) as IList; return (searchList); } And this is how you'd use it: IQueryable query = ctx.MyEntities; IList list = Search(query, typeof(MyEntity), "Name", "Ricardo Peres", MatchType.Contains, WordMatch.ExactPhrase, 10 /*0 for all*/); SyntaxHighlighter.config.clipboardSwf = 'http://alexgorbatchev.com/pub/sh/2.0.320/scripts/clipboard.swf'; SyntaxHighlighter.brushes.CSharp.aliases = ['c#', 'c-sharp', 'csharp']; SyntaxHighlighter.all();

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• Can't ping some IP addresses in the same subnet (LAN) Windows 2011 Server

  - by Ricardo

  Hi I’m running in Windows Small Server 2011 server standard (192.168.1.108), it’s my dhcp and dns server too, but suddenly all other users can’t get internet. My gateway is 192.168.1.1. After a lots of tested I can saw that my server can’t get into the router (192.168.1.1), and also into some others computers, but some other computers answer the ping command. In fact the same computer with the IP 192.168.1.9 didn't answer, but with the IP 192.168.1.63, it response! I have no routers, firewall, vlans or anything that disallow the traffic between computers, in fact when I changed the server IP address (192.168.1.109), I be able to ping the other computers and gateway, but if a back to the 192.168.1.108 the trouble comeback. I hope you can help me with this issue Ricardo

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• What are the best ways to cope with «one of those days»? [closed]

  - by Júlio Santos

  I work in a fast-paced startup and am absolutely in love with what I do. Still, I wake up to a bad mood as often as the next guy. I find that forcing myself to play out my day as usual doesn't help — in fact, it only makes it worse, possibly ruining my productivity for the rest of the week. There are several ways I can cope with this, for instance: dropping the current task for the day and getting that awesome but low-priority feature in place; doing some pending research for future development (i.e. digging up ruby gems); spending the day reading and educating myself; just taking the day off. The first three items are productive in themselves, and taking the day off recharges my coding mana for the rest of the week. Being a young developer, I'm pretty sure there's a multitude of alternatives that I haven't come across yet. How can programmers cope with off days? Edit: I am looking for answers related specifically to this profession. I therefore believe that coping with off days in our field is fundamentally different that doing so in other areas. Programmers (especially in a start-up) are a unique breed in this context in the sense that they tend to have a multitude of tasks at hand on any given moment, so they can easily switch between these without wreaking too much havoc. Programmers also tend to work based on clear, concise objectives — provided they are well managed either by themselves or a third party — and hence have a great deal of flexibility when it comes to managing their time. Finally, our line of work creates the opportunity — necessity, if you will — to fit a plethora of tasks not directly related to the current one, such as research and staying on top of new releases and software updates.

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• Is Oracle WebCenter 11g a big SharePoint ?

  - by Guilherme J Santos

  Hi there. I have some experience with SharePoint. Now my company will use Oracle WebCenter to create a internal portal. Nobody of IT team have experience with Oracle WebCenter, and I think we could use SharePoint, as we did until now. So, what are the advantages to use Oracle WebCenter? Wich are your experiences with Oracle WebCenter 11g? And how much it is different from SharePoint. What can I do with Oracle WebCenter that I cannot do with Microsoft SharePoint?

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• Dell XPS L502Xnot detecting monitor-TV

  - by Guilherme Z. Santos

  I'm running Ubuntu 12.04 LTS on a Dell XPS L502X and when I connect the HDMI cable from the TV to the computer Ubuntu detects nothing at all, It works perfectly fine in Windows 7 though. I've already went to the Display control, plugged and unplugged the TV, clicked the Detect Displays button, and nothing. Do I have to activate the HDMI output or something? Because I used another computer with a VGA output and it worked perfectly.

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• Am I allowed to display a small image on top of a Google Maps Static Api map?

  - by Fábio Santos

  I am the webmaster to my company's website. I was asked to make the Google Map on this page smaller, but the interactive map doesn't work well at all at 300x200. I was asked to place a screenshot there but since that seems to be a violation of Google's terms I decided to use the Static Maps API. As you can see, on the page, I have a custom pointer icon. I don't want to lose it, so I intend to use HTML and CSS to place the pointer over the map, thus replacing the original pointer on the client side. Am I allowed to do that?

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• How does key-based caching work?

  - by Dominic Santos

  I recently read an article on the 37Signals blog and I'm left wondering how it is that they get the cache key. It's all well and good having a cache key that includes the object's timestamp (this means that when you update the object the cache will be invalidated); but how do you then use the cache key in a template without causing a DB hit for the very object that you are trying to fetch from the cache. Specifically, how does this affect One to Many relations where you are rendering a Post's Comments for example. Example in Django: {% for comment in post.comments.all %} {% cache comment.pk comment.modified %} <p>{{ post.body }}</p> {% endcache %} {% endfor %} Is caching in Rails different to just requests to memcached for example (I know that they convert your cache key to something different). Do they also cache the cache key?

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• Is it a good idea to put all assembly: WebResource in the same cs file?

  - by Guilherme J Santos

  I have a .NET library, with some WebControls. These webControls have Embed Resources. And we declare them like it, in all webcontrols for each cs file: Something like this: [assembly: WebResource("IO.Css.MyCSS.css", "text/css")] namespace MyNamespace.MyClass { [ParseChildren(true)] [PersistChildren(false)] [Designer(typeof(MyNamespace.MyClassDesigner))] public class QuickTip : Control, INamingContainer { //My code... } } Would it be a good idea to create a cs file and include all WebResource declarations there? Example a cs file with just: [assembly: WebResource("IO.Css.MyCSS.css", "text/css")] [assembly: WebResource("IO.Image.MyImage.png", "image/png")] //And many other WebResources of all WebControls of the Assembly

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• Abierta la temporada Otoñal de Eventos en Oracle

  - by Sofia Santos

  Muchas son las sorpresas que hemos preparado para los próximos meses. Con mucha ilusión, desde Oracle os enseñaremos TODO lo que hay de nuevo en Aplicaciones y sí, para todos los gustos!!! Para empezar y estar al tanto de todo, debéis guardar esta URL: events.oracle.com. Allí encontraréis lo último en eventos Oracle, desde el internacional y espectacular Oracle Open World, hasta los eventos que estamos realizando por toda Europa. Una atención especial para los eventos de España: Oracle Customer Experience y Oracle Citizen Experience, 10 de Octubre, no lo puedes perder!!! Hay que inscribirse ya porque las plazas son limitadas y ya tenemos mucha gente inscrita. Más sobre Oracle Customer Experience aquí. En Octubre también estamos preparando unos desayunos exclusivos sobre Oracle DRM y no sólo para Madrid, en Barcelona también podéis asistir… Llega Noviembre y a principios de mes, tenemos dos eventos Exclusivos, uno es el Oracle Aplications Strategy Day, un evento en el que se atiende sólo por invitación y dónde hablaremos de estrategia además de hacer una entrega de premios a nuestros clientes de Aplicaciones. El segundo es el Oracle HCM Summit que tiene lugar en París, un evento único especialmente dedicado a los Directores de Recursos Humanos. El Oracle Performance Management Summit se realiza en el día 20 de Noviembre. Se trata de un evento dedicado a los Directores Financieros y que viene con nuevo formato que engloba una sesión plenaria, mesas redondas (Solvencia, Fatca, Planing y Cierre), además de los testimonios de nuestros clientes en vivo, listos para contestar vuestras preguntas. Hay que esperar unos días y ya veréis la agenda publicada… Nos quedamos por aquí, porque toda la pagina no llegaría para exponer todo lo que vamos a hacer. No dejes de inscribirte, nuestros eventos son gratuitos pero como siempre… las plazas son limitadas. Allí os esperamos!!!

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• Stuck With grub rescue> console

  - by rej santos

  Here is the background of my issue: I just recently installed the latest version of Ubuntu along side with Windows 8 Enterprise. However upon checking the disk size, it seems that some of the portions of the hd memory were gone so I decided to check the disk partition and have seen that is was being used by another file system. Thinking that the Ubuntu takes it boots stuff from my drive C: , I deleted that partition and formated so I can use it to store some movies, music etc. Now, as I switch on my machine, I am stucked with: error: unknown filesystem grub rescue> I googled a lot and saw the following command which seems no to me like sudo, chainloader etc, all of these command only returns unknown command in the console. What I just wanted is to boot from my Windows 8 OS. Just to add, I can't open the BIOS menu so I could choose what media to boot. As I open my machine it automatically takes me to grub rescue console. Here are the thing I already have: Ubuntu Installation Disk Windows 8 System repair Disk I just don't know how to boot into these things. Let me know what to do.

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• Finding a mentor online [closed]

  - by Athena Santos

  Possible Duplicate: How to find programming mentor? I'm a programming intern, but I want to "transition" into a product manager role after graduation. I just know that I will never be a super A++ Rockstar programmer, but from my internship I know that I can be a great program manager..one of those presumably rare people who can code well (enough)/speak programmer-ese and management-ese. Being a girl, I am looking for both male and female mentors. Female, because they know what its like to be a minority, and male, because..well, you guys are tough, and I believe to succeed in tech, a girl's gotta know how to act like a man (when appropriate). I've found some really amazing people I'd like to ask to be my mentor (in blogs, magazines, etc), but sadly, I live far, far away from them. Will be awkward/rude if I shoot them an email about being a mentor? What is the best way to establish a relationship with people like these that I admire? Any volunteers? :) Thank you in advance, and I hope you all have a great day/night.

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• When must I turn my business idea into a formal Company? [closed]

  - by Sony Santos

  I'm a programmer, I have an idea, I know how to implement it, it will be a website, and that site will be my business. My question is very basic: where in timeline must I register my business as an official Company (ie, according Government laws)? Here there are some options to debate or to help answer me: Now - or as soon as I have the idea; When looking for investors (e.g., when a prototype or business plan is ready); When implementing the website; At site's launch; I must launch the website as a personal informal business and, when the business gets success and turns into a more solid and self-running one, only then I must formalize it; It doesn't matter; I can create the company when I want. Nobody talks about that. If I just have an idea, must I run into an office to create a Company? I don't think so. When I'll look for investors, the Company must to pre-exist? Or will the Company be formed with the investor? I'm looking for a generic, country-independent answer, but may the answer for your country can be useful to me. I'm Brazilian, and I believe that the country doesn't matter to this question. (Sorry if this is off-topic, but I coudn't find a batter stackexchange site to ask this.)

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• Read a variable in bash with a default value

  - by rmarimon

  I need to read a value from the terminal in a bash script. I would like to be able to provide a default value that the user can change. # Please enter your name: Ricardo^ In this script the prompt is "Please enter your name: " the default value is "Ricardo" and the cursor would be after the default value. Is there a way to do this in a bash script?

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• ASP.NET MVC 2 Released

  - by Ricardo Peres

  Get it while it’s hot from here. Also read the release notes.

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• Differences Between NHibernate and Entity Framework

  - by Ricardo Peres

  Introduction NHibernate and Entity Framework are two of the most popular O/RM frameworks on the .NET world. Although they share some functionality, there are some aspects on which they are quite different. This post will describe this differences and will hopefully help you get started with the one you know less. Mind you, this is a personal selection of features to compare, it is by no way an exhaustive list. History First, a bit of history. NHibernate is an open-source project that was first ported from Java’s venerable Hibernate framework, one of the first O/RM frameworks, but nowadays it is not tied to it, for example, it has .NET specific features, and has evolved in different ways from those of its Java counterpart. Current version is 3.3, with 3.4 on the horizon. It currently targets .NET 3.5, but can be used as well in .NET 4, it only makes no use of any of its specific functionality. You can find its home page at NHForge. Entity Framework 1 came out with .NET 3.5 and is now on its second major version, despite being version 4. Code First sits on top of it and but came separately and will also continue to be released out of line with major .NET distributions. It is currently on version 4.3.1 and version 5 will be released together with .NET Framework 4.5. All versions will target the current version of .NET, at the time of their release. Its home location is located at MSDN. Architecture In NHibernate, there is a separation between the Unit of Work and the configuration and model instances. You start off by creating a Configuration object, where you specify all global NHibernate settings such as the database and dialect to use, the batch sizes, the mappings, etc, then you build an ISessionFactory from it. The ISessionFactory holds model and metadata that is tied to a particular database and to the settings that came from the Configuration object, and, there will typically be only one instance of each in a process. Finally, you create instances of ISession from the ISessionFactory, which is the NHibernate representation of the Unit of Work and Identity Map. This is a lightweight object, it basically opens and closes a database connection as required and keeps track of the entities associated with it. ISession objects are cheap to create and dispose, because all of the model complexity is stored in the ISessionFactory and Configuration objects. As for Entity Framework, the ObjectContext/DbContext holds the configuration, model and acts as the Unit of Work, holding references to all of the known entity instances. This class is therefore not lightweight as its NHibernate counterpart and it is not uncommon to see examples where an instance is cached on a field. Mappings Both NHibernate and Entity Framework (Code First) support the use of POCOs to represent entities, no base classes are required (or even possible, in the case of NHibernate). As for mapping to and from the database, NHibernate supports three types of mappings: XML-based, which have the advantage of not tying the entity classes to a particular O/RM; the XML files can be deployed as files on the file system or as embedded resources in an assembly; Attribute-based, for keeping both the entities and database details on the same place at the expense of polluting the entity classes with NHibernate-specific attributes; Strongly-typed code-based, which allows dynamic creation of the model and strongly typing it, so that if, for example, a property name changes, the mapping will also be updated. Entity Framework can use: Attribute-based (although attributes cannot express all of the available possibilities – for example, cascading); Strongly-typed code mappings. Database Support With NHibernate you can use mostly any database you want, including: SQL Server; SQL Server Compact; SQL Server Azure; Oracle; DB2; PostgreSQL; MySQL; Sybase Adaptive Server/SQL Anywhere; Firebird; SQLLite; Informix; Any through OLE DB; Any through ODBC. Out of the box, Entity Framework only supports SQL Server, but a number of providers exist, both free and commercial, for some of the most used databases, such as Oracle and MySQL. See a list here. Inheritance Strategies Both NHibernate and Entity Framework support the three canonical inheritance strategies: Table Per Type Hierarchy (Single Table Inheritance), Table Per Type (Class Table Inheritance) and Table Per Concrete Type (Concrete Table Inheritance). Associations Regarding associations, both support one to one, one to many and many to many. However, NHibernate offers far more collection types: Bags of entities or values: unordered, possibly with duplicates; Lists of entities or values: ordered, indexed by a number column; Maps of entities or values: indexed by either an entity or any value; Sets of entities or values: unordered, no duplicates; Arrays of entities or values: indexed, immutable. Querying NHibernate exposes several querying APIs: LINQ is probably the most used nowadays, and really does not need to be introduced; Hibernate Query Language (HQL) is a database-agnostic, object-oriented SQL-alike language that exists since NHibernate’s creation and still offers the most advanced querying possibilities; well suited for dynamic queries, even if using string concatenation; Criteria API is an implementation of the Query Object pattern where you create a semi-abstract conceptual representation of the query you wish to execute by means of a class model; also a good choice for dynamic querying; Query Over offers a similar API to Criteria, but using strongly-typed LINQ expressions instead of strings; for this, although more refactor-friendlier that Criteria, it is also less suited for dynamic queries; SQL, including stored procedures, can also be used; Integration with Lucene.NET indexer is available. As for Entity Framework: LINQ to Entities is fully supported, and its implementation is considered very complete; it is the API of choice for most developers; Entity-SQL, HQL’s counterpart, is also an object-oriented, database-independent querying language that can be used for dynamic queries; SQL, of course, is also supported. Caching Both NHibernate and Entity Framework, of course, feature first-level cache. NHibernate also supports a second-level cache, that can be used among multiple ISessionFactorys, even in different processes/machines: Hashtable (in-memory); SysCache (uses ASP.NET as the cache provider); SysCache2 (same as above but with support for SQL Server SQL Dependencies); Prevalence; SharedCache; Memcached; Redis; NCache; Appfabric Caching. Out of the box, Entity Framework does not have any second-level cache mechanism, however, there are some public samples that show how we can add this. ID Generators NHibernate supports different ID generation strategies, coming from the database and otherwise: Identity (for SQL Server, MySQL, and databases who support identity columns); Sequence (for Oracle, PostgreSQL, and others who support sequences); Trigger-based; HiLo; Sequence HiLo (for databases that support sequences); Several GUID flavors, both in GUID as well as in string format; Increment (for single-user uses); Assigned (must know what you’re doing); Sequence-style (either uses an actual sequence or a single-column table); Table of ids; Pooled (similar to HiLo but stores high values in a table); Native (uses whatever mechanism the current database supports, identity or sequence). Entity Framework only supports: Identity generation; GUIDs; Assigned values. Properties NHibernate supports properties of entity types (one to one or many to one), collections (one to many or many to many) as well as scalars and enumerations. It offers a mechanism for having complex property types generated from the database, which even include support for querying. It also supports properties originated from SQL formulas. Entity Framework only supports scalars, entity types and collections. Enumerations support will come in the next version. Events and Interception NHibernate has a very rich event model, that exposes more than 20 events, either for synchronous pre-execution or asynchronous post-execution, including: Pre/Post-Load; Pre/Post-Delete; Pre/Post-Insert; Pre/Post-Update; Pre/Post-Flush. It also features interception of class instancing and SQL generation. As for Entity Framework, only two events exist: ObjectMaterialized (after loading an entity from the database); SavingChanges (before saving changes, which include deleting, inserting and updating). Tracking Changes For NHibernate as well as Entity Framework, all changes are tracked by their respective Unit of Work implementation. Entities can be attached and detached to it, Entity Framework does, however, also support self-tracking entities. Optimistic Concurrency Control NHibernate supports all of the imaginable scenarios: SQL Server’s ROWVERSION; Oracle’s ORA_ROWSCN; A column containing date and time; A column containing a version number; All/dirty columns comparison. Entity Framework is more focused on Entity Framework, so it only supports: SQL Server’s ROWVERSION; Comparing all/some columns. Batching NHibernate has full support for insertion batching, but only if the ID generator in use is not database-based (for example, it cannot be used with Identity), whereas Entity Framework has no batching at all. Cascading Both support cascading for collections and associations: when an entity is deleted, their conceptual children are also deleted. NHibernate also offers the possibility to set the foreign key column on children to NULL instead of removing them. Flushing Changes NHibernate’s ISession has a FlushMode property that can have the following values: Auto: changes are sent to the database when necessary, for example, if there are dirty instances of an entity type, and a query is performed against this entity type, or if the ISession is being disposed; Commit: changes are sent when committing the current transaction; Never: changes are only sent when explicitly calling Flush(). As for Entity Framework, changes have to be explicitly sent through a call to AcceptAllChanges()/SaveChanges(). Lazy Loading NHibernate supports lazy loading for Associated entities (one to one, many to one); Collections (one to many, many to many); Scalar properties (thing of BLOBs or CLOBs). Entity Framework only supports lazy loading for: Associated entities; Collections. Generating and Updating the Database Both NHibernate and Entity Framework Code First (with the Migrations API) allow creating the database model from the mapping and updating it if the mapping changes. Extensibility As you can guess, NHibernate is far more extensible than Entity Framework. Basically, everything can be extended, from ID generation, to LINQ to SQL transformation, HQL native SQL support, custom column types, custom association collections, SQL generation, supported databases, etc. With Entity Framework your options are more limited, at least, because practically no information exists as to what can be extended/changed. It features a provider model that can be extended to support any database. Integration With Other Microsoft APIs and Tools When it comes to integration with Microsoft technologies, it will come as no surprise that Entity Framework offers the best support. For example, the following technologies are fully supported: ASP.NET (through the EntityDataSource); ASP.NET Dynamic Data; WCF Data Services; WCF RIA Services; Visual Studio (through the integrated designer). Documentation This is another point where Entity Framework is superior: NHibernate lacks, for starters, an up to date API reference synchronized with its current version. It does have a community mailing list, blogs and wikis, although not much used. Entity Framework has a number of resources on MSDN and, of course, several forums and discussion groups exist. Conclusion Like I said, this is a personal list. I may come as a surprise to some that Entity Framework is so behind NHibernate in so many aspects, but it is true that NHibernate is much older and, due to its open-source nature, is not tied to product-specific timeframes and can thus evolve much more rapidly. I do like both, and I chose whichever is best for the job I have at hands. I am looking forward to the changes in EF5 which will add significant value to an already interesting product. So, what do you think? Did I forget anything important or is there anything else worth talking about? Looking forward for your comments!

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• Oracle Coherence, Split-Brain and Recovery Protocols In Detail

  - by Ricardo Ferreira

  This article provides a high level conceptual overview of Split-Brain scenarios in distributed systems. It will focus on a specific example of cluster communication failure and recovery in Oracle Coherence. This includes a discussion on the witness protocol (used to remove failed cluster members) and the panic protocol (used to resolve Split-Brain scenarios). Note that the removal of cluster members does not necessarily indicate a Split-Brain condition. Oracle Coherence does not (and cannot) detect a Split-Brain as it occurs, the condition is only detected when cluster members that previously lost contact with each other regain contact. Cluster Topology and Configuration In order to create an good didactic for the article, let's assume a cluster topology and configuration. In this example we have a six member cluster, consisting of one JVM on each physical machine. The member IDs are as follows: Member ID  IP Address  1  10.149.155.76  2  10.149.155.77  3  10.149.155.236  4  10.149.155.75  5  10.149.155.79  6  10.149.155.78 Members 1, 2, and 3 are connected to a switch, and members 4, 5, and 6 are connected to a second switch. There is a link between the two switches, which provides network connectivity between all of the machines. Member 1 is the first member to join this cluster, thus making it the senior member. Member 6 is the last member to join this cluster. Here is a log snippet from Member 6 showing the complete member set: 2010-02-26 15:27:57.390/3.062 Oracle Coherence GE 3.5.3/465p2 <Info> (thread=main, member=6): Started DefaultCacheServer... SafeCluster: Name=cluster:0xDDEB Group{Address=224.3.5.3, Port=35465, TTL=4} MasterMemberSet ( ThisMember=Member(Id=6, Timestamp=2010-02-26 15:27:58.635, Address=10.149.155.78:8088, MachineId=1102, Location=process:228, Role=CoherenceServer) OldestMember=Member(Id=1, Timestamp=2010-02-26 15:27:06.931, Address=10.149.155.76:8088, MachineId=1100, Location=site:usdhcp.oraclecorp.com,machine:dhcp-burlington6-4fl-east-10-149,process:511, Role=CoherenceServer) ActualMemberSet=MemberSet(Size=6, BitSetCount=2 Member(Id=1, Timestamp=2010-02-26 15:27:06.931, Address=10.149.155.76:8088, MachineId=1100, Location=site:usdhcp.oraclecorp.com,machine:dhcp-burlington6-4fl-east-10-149,process:511, Role=CoherenceServer) Member(Id=2, Timestamp=2010-02-26 15:27:17.847, Address=10.149.155.77:8088, MachineId=1101, Location=site:usdhcp.oraclecorp.com,machine:dhcp-burlington6-4fl-east-10-149,process:296, Role=CoherenceServer) Member(Id=3, Timestamp=2010-02-26 15:27:24.892, Address=10.149.155.236:8088, MachineId=1260, Location=site:usdhcp.oraclecorp.com,machine:dhcp-burlington6-4fl-east-10-149,process:32459, Role=CoherenceServer) Member(Id=4, Timestamp=2010-02-26 15:27:39.574, Address=10.149.155.75:8088, MachineId=1099, Location=process:800, Role=CoherenceServer) Member(Id=5, Timestamp=2010-02-26 15:27:49.095, Address=10.149.155.79:8088, MachineId=1103, Location=site:usdhcp.oraclecorp.com,machine:dhcp-burlington6-4fl-east-10-149,process:3229, Role=CoherenceServer) Member(Id=6, Timestamp=2010-02-26 15:27:58.635, Address=10.149.155.78:8088, MachineId=1102, Location=process:228, Role=CoherenceServer) ) RecycleMillis=120000 RecycleSet=MemberSet(Size=0, BitSetCount=0 ) ) At approximately 15:30, the connection between the two switches is severed: Thirty seconds later (the default packet timeout in development mode) the logs indicate communication failures across the cluster. In this example, the communication failure was caused by a network failure. In a production setting, this type of communication failure can have many root causes, including (but not limited to) network failures, excessive GC, high CPU utilization, swapping/virtual memory, and exceeding maximum network bandwidth. In addition, this type of failure is not necessarily indicative of a split brain. Any communication failure will be logged in this fashion. Member 2 logs a communication failure with Member 5: 2010-02-26 15:30:32.638/196.928 Oracle Coherence GE 3.5.3/465p2 <Warning> (thread=PacketPublisher, member=2): Timeout while delivering a packet; requesting the departure confirmation for Member(Id=5, Timestamp=2010-02-26 15:27:49.095, Address=10.149.155.79:8088, MachineId=1103, Location=site:usdhcp.oraclecorp.com,machine:dhcp-burlington6-4fl-east-10-149,process:3229, Role=CoherenceServer) by MemberSet(Size=2, BitSetCount=2 Member(Id=1, Timestamp=2010-02-26 15:27:06.931, Address=10.149.155.76:8088, MachineId=1100, Location=site:usdhcp.oraclecorp.com,machine:dhcp-burlington6-4fl-east-10-149,process:511, Role=CoherenceServer) Member(Id=4, Timestamp=2010-02-26 15:27:39.574, Address=10.149.155.75:8088, MachineId=1099, Location=process:800, Role=CoherenceServer) ) The Coherence clustering protocol (TCMP) is a reliable transport mechanism built on UDP. In order for the protocol to be reliable, it requires an acknowledgement (ACK) for each packet delivered. If a packet fails to be acknowledged within the configured timeout period, the Coherence cluster member will log a packet timeout (as seen in the log message above). When this occurs, the cluster member will consult with other members to determine who is at fault for the communication failure. If the witness members agree that the suspect member is at fault, the suspect is removed from the cluster. If the witnesses unanimously disagree, the accuser is removed. This process is known as the witness protocol. Since Member 2 cannot communicate with Member 5, it selects two witnesses (Members 1 and 4) to determine if the communication issue is with Member 5 or with itself (Member 2). However, Member 4 is on the switch that is no longer accessible by Members 1, 2 and 3; thus a packet timeout for member 4 is recorded as well: 2010-02-26 15:30:35.648/199.938 Oracle Coherence GE 3.5.3/465p2 <Warning> (thread=PacketPublisher, member=2): Timeout while delivering a packet; requesting the departure confirmation for Member(Id=4, Timestamp=2010-02-26 15:27:39.574, Address=10.149.155.75:8088, MachineId=1099, Location=process:800, Role=CoherenceServer) by MemberSet(Size=2, BitSetCount=2 Member(Id=1, Timestamp=2010-02-26 15:27:06.931, Address=10.149.155.76:8088, MachineId=1100, Location=site:usdhcp.oraclecorp.com,machine:dhcp-burlington6-4fl-east-10-149,process:511, Role=CoherenceServer) Member(Id=6, Timestamp=2010-02-26 15:27:58.635, Address=10.149.155.78:8088, MachineId=1102, Location=process:228, Role=CoherenceServer) ) Member 1 has the ability to confirm the departure of member 4, however Member 6 cannot as it is also inaccessible. At the same time, Member 3 sends a request to remove Member 6, which is followed by a report from Member 3 indicating that Member 6 has departed the cluster: 2010-02-26 15:30:35.706/199.996 Oracle Coherence GE 3.5.3/465p2 <D5> (thread=Cluster, member=2): MemberLeft request for Member 6 received from Member(Id=3, Timestamp=2010-02-26 15:27:24.892, Address=10.149.155.236:8088, MachineId=1260, Location=site:usdhcp.oraclecorp.com,machine:dhcp-burlington6-4fl-east-10-149,process:32459, Role=CoherenceServer) 2010-02-26 15:30:35.709/199.999 Oracle Coherence GE 3.5.3/465p2 <D5> (thread=Cluster, member=2): MemberLeft notification for Member 6 received from Member(Id=3, Timestamp=2010-02-26 15:27:24.892, Address=10.149.155.236:8088, MachineId=1260, Location=site:usdhcp.oraclecorp.com,machine:dhcp-burlington6-4fl-east-10-149,process:32459, Role=CoherenceServer) The log for Member 3 determines how Member 6 departed the cluster: 2010-02-26 15:30:35.161/191.694 Oracle Coherence GE 3.5.3/465p2 <Warning> (thread=PacketPublisher, member=3): Timeout while delivering a packet; requesting the departure confirmation for Member(Id=6, Timestamp=2010-02-26 15:27:58.635, Address=10.149.155.78:8088, MachineId=1102, Location=process:228, Role=CoherenceServer) by MemberSet(Size=2, BitSetCount=2 Member(Id=1, Timestamp=2010-02-26 15:27:06.931, Address=10.149.155.76:8088, MachineId=1100, Location=site:usdhcp.oraclecorp.com,machine:dhcp-burlington6-4fl-east-10-149,process:511, Role=CoherenceServer) Member(Id=2, Timestamp=2010-02-26 15:27:17.847, Address=10.149.155.77:8088, MachineId=1101, Location=site:usdhcp.oraclecorp.com,machine:dhcp-burlington6-4fl-east-10-149,process:296, Role=CoherenceServer) ) 2010-02-26 15:30:35.165/191.698 Oracle Coherence GE 3.5.3/465p2 <Info> (thread=Cluster, member=3): Member departure confirmed by MemberSet(Size=2, BitSetCount=2 Member(Id=1, Timestamp=2010-02-26 15:27:06.931, Address=10.149.155.76:8088, MachineId=1100, Location=site:usdhcp.oraclecorp.com,machine:dhcp-burlington6-4fl-east-10-149,process:511, Role=CoherenceServer) Member(Id=2, Timestamp=2010-02-26 15:27:17.847, Address=10.149.155.77:8088, MachineId=1101, Location=site:usdhcp.oraclecorp.com,machine:dhcp-burlington6-4fl-east-10-149,process:296, Role=CoherenceServer) ); removing Member(Id=6, Timestamp=2010-02-26 15:27:58.635, Address=10.149.155.78:8088, MachineId=1102, Location=process:228, Role=CoherenceServer) In this case, Member 3 happened to select two witnesses that it still had connectivity with (Members 1 and 2) thus resulting in a simple decision to remove Member 6. Given the departure of Member 6, Member 2 is left with a single witness to confirm the departure of Member 4: 2010-02-26 15:30:35.713/200.003 Oracle Coherence GE 3.5.3/465p2 <Info> (thread=Cluster, member=2): Member departure confirmed by MemberSet(Size=1, BitSetCount=2 Member(Id=1, Timestamp=2010-02-26 15:27:06.931, Address=10.149.155.76:8088, MachineId=1100, Location=site:usdhcp.oraclecorp.com,machine:dhcp-burlington6-4fl-east-10-149,process:511, Role=CoherenceServer) ); removing Member(Id=4, Timestamp=2010-02-26 15:27:39.574, Address=10.149.155.75:8088, MachineId=1099, Location=process:800, Role=CoherenceServer) In the meantime, Member 4 logs a missing heartbeat from the senior member. This message is also logged on Members 5 and 6. 2010-02-26 15:30:07.906/150.453 Oracle Coherence GE 3.5.3/465p2 <Info> (thread=PacketListenerN, member=4): Scheduled senior member heartbeat is overdue; rejoining multicast group. Next, Member 4 logs a TcpRing failure with Member 2, thus resulting in the termination of Member 2: 2010-02-26 15:30:21.421/163.968 Oracle Coherence GE 3.5.3/465p2 <D4> (thread=Cluster, member=4): TcpRing: Number of socket exceptions exceeded maximum; last was "java.net.SocketTimeoutException: connect timed out"; removing the member: 2 For quick process termination detection, Oracle Coherence utilizes a feature called TcpRing which is a sparse collection of TCP/IP-based connections between different members in the cluster. Each member in the cluster is connected to at least one other member, which (if at all possible) is running on a different physical box. This connection is not used for any data transfer, only heartbeat communications are sent once a second per each link. If a certain number of exceptions are thrown while trying to re-establish a connection, the member throwing the exceptions is removed from the cluster. Member 5 logs a packet timeout with Member 3 and cites witnesses Members 4 and 6: 2010-02-26 15:30:29.791/165.037 Oracle Coherence GE 3.5.3/465p2 <Warning> (thread=PacketPublisher, member=5): Timeout while delivering a packet; requesting the departure confirmation for Member(Id=3, Timestamp=2010-02-26 15:27:24.892, Address=10.149.155.236:8088, MachineId=1260, Location=site:usdhcp.oraclecorp.com,machine:dhcp-burlington6-4fl-east-10-149,process:32459, Role=CoherenceServer) by MemberSet(Size=2, BitSetCount=2 Member(Id=4, Timestamp=2010-02-26 15:27:39.574, Address=10.149.155.75:8088, MachineId=1099, Location=process:800, Role=CoherenceServer) Member(Id=6, Timestamp=2010-02-26 15:27:58.635, Address=10.149.155.78:8088, MachineId=1102, Location=process:228, Role=CoherenceServer) ) 2010-02-26 15:30:29.798/165.044 Oracle Coherence GE 3.5.3/465p2 <Info> (thread=Cluster, member=5): Member departure confirmed by MemberSet(Size=2, BitSetCount=2 Member(Id=4, Timestamp=2010-02-26 15:27:39.574, Address=10.149.155.75:8088, MachineId=1099, Location=process:800, Role=CoherenceServer) Member(Id=6, Timestamp=2010-02-26 15:27:58.635, Address=10.149.155.78:8088, MachineId=1102, Location=process:228, Role=CoherenceServer) ); removing Member(Id=3, Timestamp=2010-02-26 15:27:24.892, Address=10.149.155.236:8088, MachineId=1260, Location=site:usdhcp.oraclecorp.com,machine:dhcp-burlington6-4fl-east-10-149,process:32459, Role=CoherenceServer) Eventually we are left with two distinct clusters consisting of Members 1, 2, 3 and Members 4, 5, 6, respectively. In the latter cluster, Member 4 is promoted to senior member. The connection between the two switches is restored at 15:33. Upon the restoration of the connection, the cluster members immediately receive cluster heartbeats from the two senior members. In the case of Members 1, 2, and 3, the following is logged: 2010-02-26 15:33:14.970/369.066 Oracle Coherence GE 3.5.3/465p2 <Warning> (thread=Cluster, member=1): The member formerly known as Member(Id=4, Timestamp=2010-02-26 15:30:35.341, Address=10.149.155.75:8088, MachineId=1099, Location=process:800, Role=CoherenceServer) has been forcefully evicted from the cluster, but continues to emit a cluster heartbeat; henceforth, the member will be shunned and its messages will be ignored. Likewise for Members 4, 5, and 6: 2010-02-26 15:33:14.343/336.890 Oracle Coherence GE 3.5.3/465p2 <Warning> (thread=Cluster, member=4): The member formerly known as Member(Id=1, Timestamp=2010-02-26 15:30:31.64, Address=10.149.155.76:8088, MachineId=1100, Location=site:usdhcp.oraclecorp.com,machine:dhcp-burlington6-4fl-east-10-149,process:511, Role=CoherenceServer) has been forcefully evicted from the cluster, but continues to emit a cluster heartbeat; henceforth, the member will be shunned and its messages will be ignored. This message indicates that a senior heartbeat is being received from members that were previously removed from the cluster, in other words, something that should not be possible. For this reason, the recipients of these messages will initially ignore them. After several iterations of these messages, the existence of multiple clusters is acknowledged, thus triggering the panic protocol to reconcile this situation. When the presence of more than one cluster (i.e. Split-Brain) is detected by a Coherence member, the panic protocol is invoked in order to resolve the conflicting clusters and consolidate into a single cluster. The protocol consists of the removal of smaller clusters until there is one cluster remaining. In the case of equal size clusters, the one with the older Senior Member will survive. Member 1, being the oldest member, initiates the protocol: 2010-02-26 15:33:45.970/400.066 Oracle Coherence GE 3.5.3/465p2 <Warning> (thread=Cluster, member=1): An existence of a cluster island with senior Member(Id=4, Timestamp=2010-02-26 15:27:39.574, Address=10.149.155.75:8088, MachineId=1099, Location=process:800, Role=CoherenceServer) containing 3 nodes have been detected. Since this Member(Id=1, Timestamp=2010-02-26 15:27:06.931, Address=10.149.155.76:8088, MachineId=1100, Location=site:usdhcp.oraclecorp.com,machine:dhcp-burlington6-4fl-east-10-149,process:511, Role=CoherenceServer) is the senior of an older cluster island, the panic protocol is being activated to stop the other island's senior and all junior nodes that belong to it. Member 3 receives the panic: 2010-02-26 15:33:45.803/382.336 Oracle Coherence GE 3.5.3/465p2 <Error> (thread=Cluster, member=3): Received panic from senior Member(Id=1, Timestamp=2010-02-26 15:27:06.931, Address=10.149.155.76:8088, MachineId=1100, Location=site:usdhcp.oraclecorp.com,machine:dhcp-burlington6-4fl-east-10-149,process:511, Role=CoherenceServer) caused by Member(Id=4, Timestamp=2010-02-26 15:27:39.574, Address=10.149.155.75:8088, MachineId=1099, Location=process:800, Role=CoherenceServer) Member 4, the senior member of the younger cluster, receives the kill message from Member 3: 2010-02-26 15:33:44.921/367.468 Oracle Coherence GE 3.5.3/465p2 <Error> (thread=Cluster, member=4): Received a Kill message from a valid Member(Id=3, Timestamp=2010-02-26 15:27:24.892, Address=10.149.155.236:8088, MachineId=1260, Location=site:usdhcp.oraclecorp.com,machine:dhcp-burlington6-4fl-east-10-149,process:32459, Role=CoherenceServer); stopping cluster service. In turn, Member 4 requests the departure of its junior members 5 and 6: 2010-02-26 15:33:44.921/367.468 Oracle Coherence GE 3.5.3/465p2 <Error> (thread=Cluster, member=4): Received a Kill message from a valid Member(Id=3, Timestamp=2010-02-26 15:27:24.892, Address=10.149.155.236:8088, MachineId=1260, Location=site:usdhcp.oraclecorp.com,machine:dhcp-burlington6-4fl-east-10-149,process:32459, Role=CoherenceServer); stopping cluster service. 2010-02-26 15:33:43.343/349.015 Oracle Coherence GE 3.5.3/465p2 <Error> (thread=Cluster, member=6): Received a Kill message from a valid Member(Id=4, Timestamp=2010-02-26 15:27:39.574, Address=10.149.155.75:8088, MachineId=1099, Location=process:800, Role=CoherenceServer); stopping cluster service. Once Members 4, 5, and 6 restart, they rejoin the original cluster with senior member 1. The log below is from Member 4. Note that it receives a different member id when it rejoins the cluster. 2010-02-26 15:33:44.921/367.468 Oracle Coherence GE 3.5.3/465p2 <Error> (thread=Cluster, member=4): Received a Kill message from a valid Member(Id=3, Timestamp=2010-02-26 15:27:24.892, Address=10.149.155.236:8088, MachineId=1260, Location=site:usdhcp.oraclecorp.com,machine:dhcp-burlington6-4fl-east-10-149,process:32459, Role=CoherenceServer); stopping cluster service. 2010-02-26 15:33:46.921/369.468 Oracle Coherence GE 3.5.3/465p2 <D5> (thread=Cluster, member=4): Service Cluster left the cluster 2010-02-26 15:33:47.046/369.593 Oracle Coherence GE 3.5.3/465p2 <D5> (thread=Invocation:InvocationService, member=4): Service InvocationService left the cluster 2010-02-26 15:33:47.046/369.593 Oracle Coherence GE 3.5.3/465p2 <D5> (thread=OptimisticCache, member=4): Service OptimisticCache left the cluster 2010-02-26 15:33:47.046/369.593 Oracle Coherence GE 3.5.3/465p2 <D5> (thread=ReplicatedCache, member=4): Service ReplicatedCache left the cluster 2010-02-26 15:33:47.046/369.593 Oracle Coherence GE 3.5.3/465p2 <D5> (thread=DistributedCache, member=4): Service DistributedCache left the cluster 2010-02-26 15:33:47.046/369.593 Oracle Coherence GE 3.5.3/465p2 <D5> (thread=Invocation:Management, member=4): Service Management left the cluster 2010-02-26 15:33:47.046/369.593 Oracle Coherence GE 3.5.3/465p2 <D5> (thread=Cluster, member=4): Member 6 left service Management with senior member 5 2010-02-26 15:33:47.046/369.593 Oracle Coherence GE 3.5.3/465p2 <D5> (thread=Cluster, member=4): Member 6 left service DistributedCache with senior member 5 2010-02-26 15:33:47.046/369.593 Oracle Coherence GE 3.5.3/465p2 <D5> (thread=Cluster, member=4): Member 6 left service ReplicatedCache with senior member 5 2010-02-26 15:33:47.046/369.593 Oracle Coherence GE 3.5.3/465p2 <D5> (thread=Cluster, member=4): Member 6 left service OptimisticCache with senior member 5 2010-02-26 15:33:47.046/369.593 Oracle Coherence GE 3.5.3/465p2 <D5> (thread=Cluster, member=4): Member 6 left service InvocationService with senior member 5 2010-02-26 15:33:47.046/369.593 Oracle Coherence GE 3.5.3/465p2 <D5> (thread=Cluster, member=4): Member(Id=6, Timestamp=2010-02-26 15:33:47.046, Address=10.149.155.78:8088, MachineId=1102, Location=process:228, Role=CoherenceServer) left Cluster with senior member 4 2010-02-26 15:33:49.218/371.765 Oracle Coherence GE 3.5.3/465p2 <Info> (thread=main, member=n/a): Restarting cluster 2010-02-26 15:33:49.421/371.968 Oracle Coherence GE 3.5.3/465p2 <D5> (thread=Cluster, member=n/a): Service Cluster joined the cluster with senior service member n/a 2010-02-26 15:33:49.625/372.172 Oracle Coherence GE 3.5.3/465p2 <Info> (thread=Cluster, member=n/a): This Member(Id=5, Timestamp=2010-02-26 15:33:50.499, Address=10.149.155.75:8088, MachineId=1099, Location=process:800, Role=CoherenceServer, Edition=Grid Edition, Mode=Development, CpuCount=2, SocketCount=1) joined cluster "cluster:0xDDEB" with senior Member(Id=1, Timestamp=2010-02-26 15:27:06.931, Address=10.149.155.76:8088, MachineId=1100, Location=site:usdhcp.oraclecorp.com,machine:dhcp-burlington6-4fl-east-10-149,process:511, Role=CoherenceServer, Edition=Grid Edition, Mode=Development, CpuCount=2, SocketCount=2) Cool isn't it?

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• How to install Juniper VPN on Ubuntu 14.04 LTS?

  - by Max Ricardo Mercurio Ribeiro

  Could you please help me ? On my old Ubuntu 13.10 I was able to run Juniper VPN (on Firefox only) using a workaround which requires you to install the missing 32libs and IcedTea (32bits). However, I recently upgraded from Ubuntu 13.10 to 14.04 (both 64 bits) and my Juniper VPN does not work anymore because it fails during startup showing the following message: "Please ensure that necessary 32 bit libraries are installed. For more details, refer KB article KB25230" "Setup failed. Please install 32 bit Java and update alternatives links using update-alternatives command. For more details, refer KB article KB25230" For some odd reason, it seems the 14.04 upgrade do not work anymore with the openjdk-7:386 and consequently the Juniper VPN as well. Any ideas ? Thanks

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• Sending Messages to SignalR Hubs from the Outside

  - by Ricardo Peres

  Introduction You are by now probably familiarized with SignalR, Microsoft’s API for real-time web functionality. This is, in my opinion, one of the greatest products Microsoft has released in recent time. Usually, people login to a site and enter some page which is connected to a SignalR hub. Then they can send and receive messages – not just text messages, mind you – to other users in the same hub. Also, the server can also take the initiative to send messages to all or a specified subset of users on its own, this is known as server push. The normal flow is pretty straightforward, Microsoft has done a great job with the API, it’s clean and quite simple to use. And for the latter – the server taking the initiative – it’s also quite simple, just involves a little more work. The Problem The API for sending messages can be achieved from inside a hub – an instance of the Hub class – which is something that we don’t have if we are the server and we want to send a message to some user or group of users: the Hub instance is only instantiated in response to a client message. The Solution It is possible to acquire a hub’s context from outside of an actual Hub instance, by calling GlobalHost.ConnectionManager.GetHubContext<T>(). This API allows us to: Broadcast messages to all connected clients (possibly excluding some); Send messages to a specific client; Send messages to a group of clients. So, we have groups and clients, each is identified by a string. Client strings are called connection ids and group names are free-form, given by us. The problem with client strings is, we do not know how these map to actual users. One way to achieve this mapping is by overriding the Hub’s OnConnected and OnDisconnected methods and managing the association there. Here’s an example: 1: public class MyHub : Hub 2: { 3: private static readonly IDictionary<String, ISet<String>> users = new ConcurrentDictionary<String, ISet<String>>(); 4:  5: public static IEnumerable<String> GetUserConnections(String username) 6: { 7: ISet<String> connections; 8:  9: users.TryGetValue(username, out connections); 10:  11: return (connections ?? Enumerable.Empty<String>()); 12: } 13:  14: private static void AddUser(String username, String connectionId) 15: { 16: ISet<String> connections; 17:  18: if (users.TryGetValue(username, out connections) == false) 19: { 20: connections = users[username] = new HashSet<String>(); 21: } 22:  23: connections.Add(connectionId); 24: } 25:  26: private static void RemoveUser(String username, String connectionId) 27: { 28: users[username].Remove(connectionId); 29: } 30:  31: public override Task OnConnected() 32: { 33: AddUser(this.Context.Request.User.Identity.Name, this.Context.ConnectionId); 34: return (base.OnConnected()); 35: } 36:  37: public override Task OnDisconnected() 38: { 39: RemoveUser(this.Context.Request.User.Identity.Name, this.Context.ConnectionId); 40: return (base.OnDisconnected()); 41: } 42: } As you can see, I am using a static field to store the mapping between a user and its possibly many connections – for example, multiple open browser tabs or even multiple browsers accessing the same page with the same login credentials. The user identity, as is normal in .NET, is obtained from the IPrincipal which in SignalR hubs case is stored in Context.Request.User. Of course, this property will only have a meaningful value if we enforce authentication. Another way to go is by creating a group for each user that connects: 1: public class MyHub : Hub 2: { 3: public override Task OnConnected() 4: { 5: this.Groups.Add(this.Context.ConnectionId, this.Context.Request.User.Identity.Name); 6: return (base.OnConnected()); 7: } 8:  9: public override Task OnDisconnected() 10: { 11: this.Groups.Remove(this.Context.ConnectionId, this.Context.Request.User.Identity.Name); 12: return (base.OnDisconnected()); 13: } 14: } In this case, we will have a one-to-one equivalence between users and groups. All connections belonging to the same user will fall in the same group. So, if we want to send messages to a user from outside an instance of the Hub class, we can do something like this, for the first option – user mappings stored in a static field: 1: public void SendUserMessage(String username, String message) 2: { 3: var context = GlobalHost.ConnectionManager.GetHubContext<MyHub>(); 4: 5: foreach (String connectionId in HelloHub.GetUserConnections(username)) 6: { 7: context.Clients.Client(connectionId).sendUserMessage(message); 8: } 9: } And for using groups, its even simpler: 1: public void SendUserMessage(String username, String message) 2: { 3: var context = GlobalHost.ConnectionManager.GetHubContext<MyHub>(); 4:  5: context.Clients.Group(username).sendUserMessage(message); 6: } Using groups has the advantage that the IHubContext interface returned from GetHubContext has direct support for groups, no need to send messages to individual connections. Of course, you can wrap both mapping options in a common API, perhaps exposed through IoC. One example of its interface might be: 1: public interface IUserToConnectionMappingService 2: { 3: //associate and dissociate connections to users 4:  5: void AddUserConnection(String username, String connectionId); 6:  7: void RemoveUserConnection(String username, String connectionId); 8: } SignalR has built-in dependency resolution, by means of the static GlobalHost.DependencyResolver property: 1: //for using groups (in the Global class) 2: GlobalHost.DependencyResolver.Register(typeof(IUserToConnectionMappingService), () => new GroupsMappingService()); 3:  4: //for using a static field (in the Global class) 5: GlobalHost.DependencyResolver.Register(typeof(IUserToConnectionMappingService), () => new StaticMappingService()); 6:  7: //retrieving the current service (in the Hub class) 8: var mapping = GlobalHost.DependencyResolver.Resolve<IUserToConnectionMappingService>(); Now all you have to do is implement GroupsMappingService and StaticMappingService with the code I shown here and change SendUserMessage method to rely in the dependency resolver for the actual implementation. Stay tuned for more SignalR posts!

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• NHibernate 2 Beginner's Guide Review

  - by Ricardo Peres

  OK, here's the review I promised a while ago. This is a beginner's introduction to NHibernate, so if you have already some experience with NHibernate, you will notice it lacks a lot of concepts and information. It starts with a good description of NHibernate and why would we use it. It goes on describing basic mapping scenarios having primary keys generated with the HiLo or Identity algorithms, without actually explaining why would we choose one over the other. As for mapping, the book talks about XML mappings and provides a simple example of Fluent NHibernate, comparing it to its XML counterpart. When it comes to relations, it covers one-to-many/many-to-one and many-to-many, not one-to-one relations, but only talks briefly about lazy loading, which is, IMO, an important concept. Only Bags are described, not any of the other collection types. The log4net configuration description gets it's own chapter, which I find excessive. The chapter on configuration merely lists the most common properties for configuring NHibernate, both in XML and in code. Querying only talks about loading by ID (using Get, not Load) and using Criteria API, on which a paging example is presented as well as some common filtering options (property equals/like/between to, no examples on conjunction/disjunction, however). There's a chapter fully dedicated to ASP.NET, which explains how we can use NHibernate in web applications. It basically talks about ASP.NET concepts, though. Following it, another chapter explains how we can build our own ASP.NET providers using NHibernate (Membership, Role). The available entity generators for NHibernate are referred and evaluated on a chapter of their own, the list is fine (CodeSmith, nhib-gen, AjGenesis, Visual NHibernate, MyGeneration, NGen, NHModeler, Microsoft T4 (?) and hbm2net), examples are provided whenever possible, however, I have some problems with some of the evaluations: for example, Visual NHibernate scores 5 out of 5 on Visual Studio integration, which simply does not exist! I suspect the author means to say that it can be launched from inside Visual Studio, but then, what can't? Finally, there's a chapter I really don't understand. It seems like a bag where a lot of things are thrown in, like NHibernate Burrow (which actually isn't explained at all), Blog.Net components, CSS template conversion and web.config settings related to the maximum request length for file uploads and ending with XML configuration, with the help of GhostDoc. Like I said, the book is only good for absolute beginners, it does a fair job in explaining the very basics, but lack a lot of not-so-basic concepts. Among other things, it lacks: Inheritance mapping strategies (table per class hierarchy, table per class, table per concrete class) Load versus Get usage Other usefull ISession methods First level cache (Identity Map pattern) Other collection types other that Bag (Set, List, Map, IdBag, etc Fetch options User Types Filters Named queries LINQ examples HQL examples And that's it! I hope you find this review useful. The link to the book site is https://www.packtpub.com/nhibernate-2-x-beginners-guide/book

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• Exam 71-515: TS: Web Applications Development with Microsoft .NET Framework 4

  - by Ricardo Peres

  I took the 71-515 exam today. 85 questions, 240 minutes. Here are some notes: Great number of jQuery questions, mostly having to do with AJAX Lots of MVC 2 questions also A number of classic ASP.NET web forms, of which only a few were related with the new 4 features Some Entity Framework Some plain old JavaScript, like, changing an image dynamically I think I did OK. As with my previous exam, I still don't know if I passed or not, will have to wait for the end of the beta period.

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• Windows Presentation Foundation 4.5 Cookbook Review

  - by Ricardo Peres

  As promised, here’s my review of Windows Presentation Foundation 4.5 Cookbook, that Packt Publishing kindly made available to me. It is an introductory book, targeted at WPF newcomers or users with few experience, following the typical recipes or cookbook style. Like all Packt Publishing books on development, each recipe comes with sample code that is self-sufficient for understanding the concepts it tries to illustrate. It starts on chapter 1 by introducing the most important concepts, the XAML language itself, what can be declared in XAML and how to do it, what are dependency and attached properties as well as markup extensions and events, which should give readers a most required introduction to how WPF works and how to do basic stuff. It moves on to resources on chapter 2, which also makes since, since it’s such an important concept in WPF. Next, chapter 3, come the panels used for laying controls on the screen, all of the out of the box panels are described with typical use cases. Controls come next in chapter 4; the difference between elements and controls is introduced, as well as content controls, headered controls and items controls, and all standard controls are introduced. The book shows how to change the way they look by using templates. The next chapter, 5, talks about top level windows and the WPF application object: how to access startup arguments, how to set the main window, using standard dialogs and there’s even a sample on how to have a irregularly-shaped window. This is one of the most important concepts in WPF: data binding, which is the theme for the following chapter, 6. All common scenarios are introduced, the binding modes, directions, triggers, etc. It talks about the INotifyPropertyChanged interface and how to use it for notifying data binding subscribers of changes in data sources. Data templates and selectors are also covered, as are value converters and data triggers. Examples include master-detail and sorting, grouping and filtering collections and binding trees and grids. Last it covers validation rules and error templates. Chapter 7 talks about the current trend in WPF development, the Model View View-Model (MVVM) framework. This is a well known pattern for connecting things interface to actions, and it is explained competently. A typical implementation is presented which also presents the command pattern used throughout WPF. A complete application using MVVM is presented from start to finish, including typical features such as undo. Style and layout is covered on chapter 8. Why/how to use styles, applying them automatically,  using the many types of triggers to change styles automatically, using Expression Blend behaviors and templates are all covered. Next chapter, 9, is about graphics and animations programming. It explains how to create shapes, transform common UI elements, apply special effects and perform simple animations. The following chapter, 10, is about creating custom controls, either by deriving from UserControl or from an existing control or framework element class, applying custom templates for changing the way the control looks. One useful example is a custom layout panel that arranges its children along a circumference. The final chapter, 11, is about multi-threading programming and how one can integrate it with WPF. Includes how to invoke methods and properties on WPF classes from threads other than the main UI, using background tasks and timers and even using the new C# 5.0 asynchronous operations. It’s an interesting book, like I said, mostly for newcomers. It provides a competent introduction to WPF, with examples that cover the most common scenarios and also give directions to more complex ones. I recommend it to everyone wishing to learn WPF.

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