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• How to maxmise the largest contiguous block of memory in the Large Object Heap

  - by Unsliced

  The situation is that I am making a WCF call to a remote server which is returns an XML document as a string. Most of the time this return value is a few K, sometimes a few dozen K, very occasionally a few hundred K, but very rarely it could be several megabytes (first problem is that there is no way for me to know). It's these rare occasions that are causing grief. I get a stack trace that starts: System.OutOfMemoryException: Exception of type 'System.OutOfMemoryException' was thrown. at System.Xml.BufferBuilder.AddBuffer() at System.Xml.BufferBuilder.AppendHelper(Char* pSource, Int32 count) at System.Xml.BufferBuilder.Append(Char[] value, Int32 start, Int32 count) at System.Xml.XmlTextReaderImpl.ParseText() at System.Xml.XmlTextReaderImpl.ParseElementContent() at System.Xml.XmlTextReaderImpl.Read() at System.Xml.XmlTextReader.Read() at System.Xml.XmlReader.ReadElementString() at Microsoft.Xml.Serialization.GeneratedAssembly.XmlSerializationReaderMDRQuery.Read2_getMarketDataResponse() at Microsoft.Xml.Serialization.GeneratedAssembly.ArrayOfObjectSerializer2.Deserialize(XmlSerializationReader reader) at System.Xml.Serialization.XmlSerializer.Deserialize(XmlReader xmlReader, String encodingStyle, XmlDeserializationEvents events) at System.Xml.Serialization.XmlSerializer.Deserialize(XmlReader xmlReader, String encodingStyle) at System.Web.Services.Protocols.SoapHttpClientProtocol.ReadResponse(SoapClientMessage message, WebResponse response, Stream responseStream, Boolean asyncCall) at System.Web.Services.Protocols.SoapHttpClientProtocol.Invoke(String methodName, Object[] parameters) I've read around and it is because the Large Object Heap is just getting too fragmented, so even preceding the call with a quick check to StringBuilder.EnsureCapacity just causes the OutOfMemoryException to be thrown earlier (and because I'm guessing at what's needed, it might not actually need that much so my check is causing more problems than it is solving). Some opinions are that there's not much I can do about it. Some of the questions I've asked myself: Use less memory - have you checked for leaks? Yes. The memory usage goes up and down, but there's no fundamental growth that guarantees this to happen. Some of the times it fails, it succeeded at that stage previously. Transfer smaller amounts Not an option, this is a third party web service over which I have no control (or at least it would take a long time to resolve, in the meantime I still have a problem) Can you do something to the LOH to make it less likely to fail? ... now this is most fruitful course. It's a 32-bit process (it has to be for various political, technical and boring reasons) but there's normally hundreds of meg free (multiples of the largest amount for which we've seen failures). Can we monitor the LOH? Using perfmon I can track the size of the heaps, but I don't think there's a way to monitor the largest available contiguous block of memory. Question is: any advice or suggestions for things to try?

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• Sorting a list of colors in one dimension?

  - by Ptah- Opener of the Mouth

  I would like to sort a one-dimensional list of colors so that colors that a typical human would perceive as "like" each other are near each other. Obviously this is a difficult or perhaps impossible problem to get "perfectly", since colors are typically described with three dimensions, but that doesn't mean that there aren't some sorting methods that look obviously more natural than others. For example, sorting by RGB doesn't work very well, as it will sort in the following order, for example: (1) R=254 G=0 B=0 (2) R=254 G=255 B=0 (3) R=255 G=0 B=0 (4) R=255 G=255 B=0 That is, it will alternate those colors red, yellow, red, yellow, with the two "reds" being essentially imperceivably different than each other, and the two yellows also being imperceivably different from each other. But sorting by HLS works much better, generally speaking, and I think HSL even better than that; with either, the reds will be next to each other, and the yellows will be next to each other. But HLS/HSL has some problems, too; things that people would perceive as "black" could be split far apart from each other, as could things that people would perceive as "white". Again, I understand that I pretty much have to accept that there will be some splits like this; I'm just wondering if anyone has found a better way than HLS/HSL. And I'm aware that "better" is somewhat arbitrary; I mean "more natural to a typical human". For example, a vague thought I've had, but have not yet tried, is perhaps "L is the most important thing if it is very high or very low", but otherwise it is the least important. Has anyone tried this? Has it worked well? What specifically did you decide "very low" and "very high" meant? And so on. Or has anyone found anything else that would improve upon HSL? I should also note that I am aware that I can define a space-filling curve through the cube of colors, and order them one-dimensionally as they would be encountered while travelling along that curve. That would eliminate perceived discontinuities. However, it's not really what I want; I want decent overall large-scale groupings more than I want perfect small-scale groupings. Thanks in advance for any help.

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• Measure width() with jQuery after DOM refresh

  - by o_O Tync

  My script dynamically creates a <ul> width left-floating <li>s inside: it's a paginator. Afterwards, the script measures width of all <li>s and summs them up. The problem is that after the nodes are injected into the document — the browser refreshed DOM and applies CSS styles which takes a while. It has a negative effect on my script: when these operations are not complete before I measure the width — my script gets a wrong value. If I perform the measure in a second — everything is ok. The thing I'm looking for is a way to detect the moment when the <ul> is fully drawn, styles applied and the width has stabilizes. Or at least a way to detect every dimensions changes. Of course I can use setTimeout(..., 100) but it's ugly and I guess — not a solution at all. If there's a way to detect width stabilization — I would do the measuring right after it to get the correct values. HTML code generated by the DOM <div> <ul> <li><a href="...">1</a></li> <li><a href="...">2</a></li> .... </ul> </div> P.S. Why I need this. My paginator's left-floating <li> items tend to move to the next line when the <ul> tries to become wider than the page itself. Even though most of <li>s are invisible because of parent <div>'s width restriction: div { width: 500px; overflow: hidden; } div ul { width: 100%; white-space: nowrap; } div ul li { display: block; float: left; } they still go down unless I specify the actual summed width of the <ul> with the script.

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• What are the weaknesses of this user authentication method?

  - by byronh

  I'm developing my own PHP framework. It seems all the security articles I have read use vastly different methods for user authentication than I do so I could use some help in finding security holes. Some information that might be useful before I start. I use mod_rewrite for my MVC url's. Passwords are sha1 and md5 encrypted with 24 character salt unique to each user. mysql_real_escape_string and/or variable typecasting on everything going in, and htmlspecialchars on everything coming out. Step-by step process: Top of every page: session_start(); session_regenerate_id(); If user logs in via login form, generate new random token to put in user's MySQL row. Hash is generated based on user's salt (from when they first registered) and the new token. Store the hash and plaintext username in session variables, and duplicate in cookies if 'Remember me' is checked. On every page, check for cookies. If cookies set, copy their values into session variables. Then compare $_SESSION['name'] and $_SESSION['hash'] against MySQL database. Destroy all cookies and session variables if they don't match so they have to log in again. If login is valid, some of the user's information from the MySQL database is stored in an array for easy access. So far, I've assumed that this array is clean so when limiting user access I refer to user.rank and deny access if it's below what's required for that page. I've tried to test all the common attacks like XSS and CSRF, but maybe I'm just not good enough at hacking my own site! My system seems way too simple for it to actually be secure (the security code is only 100 lines long). What am I missing? I've also spent alot of time searching for the vulnerabilities with mysql_real_escape string but I haven't found any information that is up-to-date (everything is from several years ago at least and has apparently been fixed). All I know is that the problem was something to do with encoding. If that problem still exists today, how can I avoid it? Any help will be much appreciated.

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• WPF/C#: How to simplify the use of codes when calling a function (Generating Images)

  - by eibhrum

  I created a function in one of my application that allows to generate an image (in WPF) by getting the 'source path' from the database that I am using: public void ShowImageThumb() { try { cn = new MySqlConnection(); cn.ConnectionString = ConfigurationManager.AppSettings["MyConnection"]; cn.Open(); MySqlCommand cmd = new MySqlCommand(); cmd.Connection = cn; cmd.CommandType = CommandType.Text; cmd.CommandText = "SELECT thumb FROM album WHERE thumbNo=1"; MySqlDataAdapter adp = new MySqlDataAdapter(); adp.SelectCommand = cmd; DataTable dt = new DataTable(); adp.Fill(dt); MySqlDataReader r = cmd.ExecuteReader(); while (r.Read()) { BitmapImage bmi1 = new BitmapImage(new Uri(r[0].ToString(), UriKind.Relative)); image1.Source = bmi1; } r.Close(); cn.Close(); } catch (Exception err){ System.Windows.MessageBox.Show(err.Message); } finally { } } Take a look on my SQL statement. I put a WHERE thumbNo=1 which allows the function to get 1 record. You see, I do have at least 10 records - file paths listed in that table. I just wanna ask if there's a possible way to make my SQL statement something like this: SELECT thumb FROM album; while having this piece of code inserted in my function: BitmapImage bmi2 = new BitmapImage(new Uri(r["second record?"].ToString(), UriKind.Relative)); image2.Source = bmi2; //something like this BitmapImage bmi3 = new BitmapImage(new Uri(r["third record?"].ToString(), UriKind.Relative)); image3.Source = bmi3; //something like this and so on and so forth, without ending up creating 10 different functions for 10 records. ShowImageThumb2(); . . // will not do this . ShowImageThumb10(); Sorry for the lengthy post. I hope somebody could answer back. Thanks!

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• Parallel Task Library WaitAny Design

  - by colithium

  I've just begun to explore the PTL and have a design question. My Scenario: I have a list of URLs that each refer to an image. I want each image to be downloaded in parallel. As soon as at least one image is downloaded, I want to execute a method that does something with the downloaded image. That method should NOT be parallelized -- it should be serial. I think the following will work but I'm not sure if this is the right way to do it. Because I have separate classes for collecting the images and for doing "something" with the collected images, I end up passing around an array of Tasks which seems wrong since it exposes the inner workings of how images are retrieved. But I don't know a way around it. In reality there is more to both of these methods but that's not important for this. Just know that they really shouldn't be lumped into one large method that both retrieves and does something with the image. Task<Image>[] downloadTasks = collector.RetrieveImages(listOfURLs); for (int i = 0; i < listOfURLs.Count; i++) { //Wait for any of the remaining downloads to complete int completedIndex = Task<Image>.WaitAny(downloadTasks); Image completedImage = downloadTasks[completedIndex].Result; //Now do something with the image (this "something" must happen serially) } /////////////////////////////////////////////////// public Task<Image>[] RetrieveImages(List<string> urls) { Task<Image>[] tasks = new Task<Image>[urls.Count]; int index = 0; foreach (string url in urls) { string lambdaVar = url; //Required... Bleh tasks[index] = Task<Image>.Factory.StartNew(() => { using (WebClient client = new WebClient()) { //TODO: Replace with live image locations string fileName = String.Format("{0}.png", i); client.DownloadFile(lambdaVar, Path.Combine(Application.StartupPath, fileName)); } return Image.FromFile(Path.Combine(Application.StartupPath, fileName)); }, TaskCreationOptions.LongRunning | TaskCreationOptions.AttachedToParent); index++; } return tasks; }

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• Using pointers, references, handles to generic datatypes, as generic and flexible as possible

  - by Patrick

  In my application I have lots of different data types, e.g. Car, Bicycle, Person, ... (they're actually other data types, but this is just for the example). Since I also have quite some 'generic' code in my application, and the application was originally written in C, pointers to Car, Bicycle, Person, ... are often passed as void-pointers to these generic modules, together with an identification of the type, like this: Car myCar; ShowNiceDialog ((void *)&myCar, DATATYPE_CAR); The 'ShowNiceDialog' method now uses meta-information (functions that map DATATYPE_CAR to interfaces to get the actual data out of Car) to get information of the car, based on the given data type. That way, the generic logic only has to be written once, and not every time again for every new data type. Of course, in C++ you could make this much easier by using a common root class, like this class RootClass { public: string getName() const = 0; }; class Car : public RootClass { ... }; void ShowNiceDialog (RootClass *root); The problem is that in some cases, we don't want to store the data type in a class, but in a totally different format to save memory. In some cases we have hundreds of millions of instances that we need to manage in the application, and we don't want to make a full class for every instance. Suppose we have a data type with 2 characteristics: A quantity (double, 8 bytes) A boolean (1 byte) Although we only need 9 bytes to store this information, putting it in a class means that we need at least 16 bytes (because of the padding), and with the v-pointer we possibly even need 24 bytes. For hundreds of millions of instances, every byte counts (I have a 64-bit variant of the application and in some cases it needs 6 GB of memory). The void-pointer approach has the advantage that we can almost encode anything in a void-pointer and decide how to use it if we want information from it (use it as a real pointer, as an index, ...), but at the cost of type-safety. Templated solutions don't help since the generic logic forms quite a big part of the application, and we don't want to templatize all this. Additionally, the data model can be extended at run time, which also means that templates won't help. Are there better (and type-safer) ways to handle this than a void-pointer? Any references to frameworks, whitepapers, research material regarding this?

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• How to get started with testing(jMock)

  - by London

  Hello, I'm trying to learn how to write tests. I'm also learning Java, I was told I should learn/use/practice jMock, I've found some articles online that help to certain extend like : http://www.theserverside.com/news/1365050/Using-JMock-in-Test-Driven-Development http://jeantessier.com/SoftwareEngineering/Mocking.html#jMock And most articles I found was about test driven development, write tests first then write code to make the test pass. I'm not looking for that at the moment, I'm trying to write tests for already existing code with jMock. The official documentation is vague to say the least and just too hard for me. Does anybody have better way to learn this. Good books/links/tutorials would help me a lot. thank you EDIT - more concrete question : http://jeantessier.com/SoftwareEngineering/Mocking.html#jMock - from this article Tried this to mock this simple class : import java.util.Map; public class Cache { private Map<Integer, String> underlyingStorage; public Cache(Map<Integer, String> underlyingStorage) { this.underlyingStorage = underlyingStorage; } public String get(int key) { return underlyingStorage.get(key); } public void add(int key, String value) { underlyingStorage.put(key, value); } public void remove(int key) { underlyingStorage.remove(key); } public int size() { return underlyingStorage.size(); } public void clear() { underlyingStorage.clear(); } } Here is how I tried to create a test/mock : public class CacheTest extends TestCase { private Mockery context; private Map mockMap; private Cache cache; @Override @Before public void setUp() { context = new Mockery() { { setImposteriser(ClassImposteriser.INSTANCE); } }; mockMap = context.mock(Map.class); cache = new Cache(mockMap); } public void testCache() { context.checking(new Expectations() {{ atLeast(1).of(mockMap).size(); will(returnValue(int.class)); }}); } } It passes the test and basically does nothing, what I wanted is to create a map and check its size, and you know work some variations try to get a grip on this. Understand better trough examples, what else could I test here or any other exercises would help me a lot. tnx

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• Simplifying a four-dimensional rule table in Matlab: addressing rows and columns of each dimension

  - by Cate

  Hi all. I'm currently trying to automatically generate a set of fuzzy rules for a set of observations which contain four values for each observation, where each observation will correspond to a state (a good example is with Fisher's Iris Data). In Matlab I am creating a four dimensional rule table where a single cell (a,b,c,d) will contain the corresponding state. To reduce the table I am following the Hong and Lee method of row and column similarity checking but I am having difficulty understanding how to address the third and fourth dimensions' rows and columns. From the method it is my understanding that each dimension is addressed individually and if the rule is true, the table is simplified. The rules for merging are as follows: If all cells in adjacent columns or rows are the same. If two cells are the same or if either of them is empty in adjacent columns or rows and at least one cell in both is not empty. If all cells in a column or row are empty and if cells in its two adjacent columns or rows are the same, merge the three. If all cells in a column or row are empty and if cells in its two adjacent columns or rows are the same or either of them is empty, merge the three. If all cells in a column or row are empty and if all the non-empty cells in the column or row to its left have the same region, and all the non-empty cells in the column or row to its right have the same region, but one different from the previously mentioned region, merge these three columns into two parts. Now for the confusing bit. Simply checking if the entire row/column is the same as the adjacent (rule 1) seems simple enough: if (a,:,:,:) == (a+1,:,:,:) (:,b,:,:) == (:,b+1,:,:) (:,:,c,:) == (:,:,c+1,:) (:,:,:,d) == (:,:,:,d+1) is this correct? but to check if the elements in the row/column match, or either is zero (rules 2 and 4), I am a bit lost. Would it be something along these lines: for a = 1:20 for i = 1:length(b) if (a+1,i,:,:) == (a,i,:,:) ... else if (a+1,i,:,:) == 0 ... else if (a,i,:,:) == 0 etc. and for the third and fourth dimensions: for c = 1:20 for i = 1:length(a) if (i,:,c,:) == (i,:,c+1,:) ... else if (i,:,c+1,:) == 0 ... else if (i,:,c,:) == 0 etc. for d = 1:20 for i = 1:length(a) if (i,:,:,d) == (i,:,:,d+1) ... else if (i,:,:,d+1) == 0 ... else if (i,:,:,d) == 0 etc. even any help with four dimensional arrays would be useful as I'm so confused by the thought of more than three! I would advise you look at the paper to understand my meaning - they themselves have used the Iris data but only given an example with a 2D table. Thanks in advance, hopefully!

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• Runtime.exec causes duplicate JVM to hang indefinitely until killed (Solaris 10)

  - by John

  All, We are running a J2EE application on WebLogic server 9.2 MP2 with a jrockit 64-bit JVM (27.3.1) on Solaris 10. We call use runtime.exec to call an executable called jfmerge to create PDF documents. We have found that in Solaris, when runtime.exec is called, a duplicate JVM is temporarily spawned to kick off the jfmerge process. While this is inefficient (our JVM is 5 GB, thus the duplicated shell JVM is also 5 GB), the major problem lies in the fact that when there is heavy load on this functionality (PDF generation) in our application, sometimes the duplicated JVM never exits. When the JVM hangs, the servers create large issues (extreme application slowness and terminated user sessions) as the entire duplicate JVM get's all of its 5 GB of process size written to disk swap. We have noted the following hung thread correlated with a hung JVM process until the process is manually killed: "[STUCK] ExecuteThread: '17' for queue: 'weblogic.kernel.Default (self-tuning)'" id=3463 idx=0x158 tid=3460 prio=1 alive, in native, daemon at jrockit/io/FileNativeIO.readBytesPinned(Ljava/io/FileDescriptor;[BII)I(Native Method) at jrockit/io/FileNativeIO.readBytes(FileNativeIO.java:30) at java/io/FileInputStream.readBytes([BII)I(FileInputStream.java) at java/io/FileInputStream.read(FileInputStream.java:194) at java/lang/UNIXProcess$DeferredCloseInputStream.read(UNIXProcess.java:227) at java/io/BufferedInputStream.fill(BufferedInputStream.java:218) at java/io/BufferedInputStream.read(BufferedInputStream.java:235) ^-- Holding lock: java/io/BufferedInputStream@0xfffffffec6510470[thin lock] at gov/v3/common/formgeneration/sessionbean/FormsBean.getProcessStatus(FormsBean.java:809) at gov/v3/common/formgeneration/sessionbean/FormsBean.createPDF(FormsBean.java:750) at gov/v3/common/formgeneration/sessionbean/FormsBean.getTemplateDetails(FormsBean.java:450) at gov/v3/common/formgeneration/sessionbean/FormsBean.generateSinglePDF(FormsBean.java:1371) at gov/v3/common/formgeneration/sessionbean/FormsBean.generatePDF(FormsBean.java:263) at gov/v3/common/formgeneration/sessionbean/FormsBean.endorseDocument(FormsBean.java:2377) at gov/v3/common/formgeneration/sessionbean/Forms_qaco28_EOImpl.endorseDocument(Forms_qaco28_EOImpl.java:214) at gov/v3/delegates/common/FormsAndNoticesDelegate.endorseDocument(FormsAndNoticesDelegate.java:128) at gov/v3/actions/common/EndorseDocumentAction.executeRequest(EndorseDocumentAction.java:68) at gov/v3/fwk/controller/struts/action/V3CommonDispatchAction.dispatchToExecuteMethod(V3CommonDispatchAction.java:532) at gov/v3/fwk/controller/struts/action/V3CommonDispatchAction.executeBaseAction(V3CommonDispatchAction.java:336) at gov/v3/fwk/controller/struts/action/V3BaseDispatchAction.execute(V3BaseDispatchAction.java:69) at org/apache/struts/action/RequestProcessor.processActionPerform(RequestProcessor.java:484) at gov/v3/fwk/controller/struts/requestprocessor/V3TilesRequestProcessor.processActionPerform(V3TilesRequestProcessor.java:384) at org/apache/struts/action/RequestProcessor.process(RequestProcessor.java:274) at org/apache/struts/action/ActionServlet.process(ActionServlet.java:1482) at org/apache/struts/action/ActionServlet.doGet(ActionServlet.java:507) at gov/v3/fwk/controller/struts/servlet/V3ControllerServlet.doGet(V3ControllerServlet.java:110) at javax/servlet/http/HttpServlet.service(HttpServlet.java:743) at javax/servlet/http/HttpServlet.service(HttpServlet.java:856) at weblogic/servlet/internal/StubSecurityHelper$ServletServiceAction.run(StubSecurityHelper.java:227) at weblogic/servlet/internal/StubSecurityHelper.invokeServlet(StubSecurityHelper.java:125) at weblogic/servlet/internal/ServletStubImpl.execute(ServletStubImpl.java:283) at weblogic/servlet/internal/ServletStubImpl.execute(ServletStubImpl.java:175) at weblogic/servlet/internal/WebAppServletContext$ServletInvocationAction.run(WebAppServletContext.java:3231) at weblogic/security/acl/internal/AuthenticatedSubject.doAs(AuthenticatedSubject.java:321) at weblogic/security/service/SecurityManager.runAs(SecurityManager.java:121) at weblogic/servlet/internal/WebAppServletContext.securedExecute(WebAppServletContext.java:2002) at weblogic/servlet/internal/WebAppServletContext.execute(WebAppServletContext.java:1908) at weblogic/servlet/internal/ServletRequestImpl.run(ServletRequestImpl.java:1362) at weblogic/work/ExecuteThread.execute(ExecuteThread.java:209) at weblogic/work/ExecuteThread.run(ExecuteThread.java:181) at jrockit/vm/RNI.c2java(JJJJJ)V(Native Method) -- end of trace We would like to do a couple of things: 1.) Prevent the spawning of a duplicate JVM, as we do not need any of it's functions when executing the simple jfmerge executable, and it creates massive overhead. 2.) In the short term at least prevent this duplicate JVM from handing indefinitely.

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• HttpWebResponse get mixed up when used inside multiple threads

  - by Holli

  In my Application I have a few threads who will get data from a web service. Basically I just open an URL and get an XML output. I have a few threads who do this continuously but with different URLs. Sometimes the results are mixed up. The XML output doesn't belong to the URL of a thread but to the URL of another thread. In each thread I create an instance of the class GetWebPage and call the method Get from this instance. The method is very simple and based mostly on code from the MSDN documentation. (See below. I removed my error handling here!) public string Get(string userAgent, string url, string user, string pass, int timeout, int readwriteTimeout, WebHeaderCollection whc) { string buffer = string.Empty; HttpWebRequest myWebRequest = (HttpWebRequest)WebRequest.Create(url); if (!string.IsNullOrEmpty(userAgent)) myWebRequest.UserAgent = userAgent; myWebRequest.Timeout = timeout; myWebRequest.ReadWriteTimeout = readwriteTimeout; myWebRequest.Credentials = new NetworkCredential(user, pass); string[] headers = whc.AllKeys; foreach (string s in headers) { myWebRequest.Headers.Add(s, whc.Get(s)); } using (HttpWebResponse myWebResponse = (HttpWebResponse)myWebRequest.GetResponse()) { using (Stream ReceiveStream = myWebResponse.GetResponseStream()) { Encoding encode = Encoding.GetEncoding("utf-8"); StreamReader readStream = new StreamReader(ReceiveStream, encode); // Read 1024 characters at a time. Char[] read = new Char[1024]; int count = readStream.Read(read, 0, 1024); int break_counter = 0; while (count > 0 && break_counter < 10000) { String str = new String(read, 0, count); buffer += str; count = readStream.Read(read, 0, 1024); break_counter++; } } } return buffer; As you can see I have no public properties or any other shared resources. At least I don't see any. The url is the service I call in the internet and buffer is the XML Output from the server. Like I said I have multiple instances of this class/method in a few threads (10 to 12) and sometimes buffer does not belong the the url of the same thread but another thread.

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• A better way to delete a list of elements from multiple tables

  - by manyxcxi

  I know this looks like a 'please write the code' request, but some basic pointer/principles for doing this the right way should be enough to get me going. I have the following stored procedure: CREATE PROCEDURE `TAA`.`runClean` (IN idlist varchar(1000)) BEGIN DECLARE EXIT HANDLER FOR NOT FOUND ROLLBACK; DECLARE EXIT HANDLER FOR SQLEXCEPTION ROLLBACK; DECLARE EXIT HANDLER FOR SQLWARNING ROLLBACK; START TRANSACTION; DELETE FROM RunningReports WHERE run_id IN (idlist); DELETE FROM TMD_INDATA_INVOICE WHERE run_id IN (idlist); DELETE FROM TMD_INDATA_LINE WHERE run_id IN (idlist); DELETE FROM TMD_OUTDATA_INVOICE WHERE run_id IN (idlist); DELETE FROM TMD_OUTDATA_LINE WHERE run_id IN (idlist); DELETE FROM TMD_TEST WHERE run_id IN (idlist); DELETE FROM RunHistory WHERE id IN (idlist); COMMIT; END $$ It is called by a PHP script to clean out old run history. It is not particularly efficient as you can see and I would like to speed it up. The PHP script gathers the ids to remove from the tables with the following query: $query = "SELECT id, stop_time FROM RunHistory WHERE config_id = $configId AND save = 0 AND NOT(stop_time IS NULL) ORDER BY stop_time"; It keeps the last five run entries and deletes all the rest. So using this query to bring back all the IDs, it determines which ones to delete and keeps the 'newest' five. After gathering the IDs it sends them to the stored procedure to remove them from the associated tables. I'm not very good with SQL, but I ASSUME that using an IN statement and not joining these tables together is probably the least efficient way I can do this, but I don't know enough to ask anything but "how do I do this better?" If possible, I would like to do this all in my stored procedure using a query to gather all the IDs except for the five 'newest', then delete them. Another twist, run entries can be marked save (save = 1) and should not be deleted. The RunHistory table looks like this: CREATE TABLE `TAA`.`RunHistory` ( `id` int(11) NOT NULL auto_increment, `start_time` datetime default NULL, `stop_time` datetime default NULL, `config_id` int(11) NOT NULL, [...] `save` tinyint(1) NOT NULL default '0', PRIMARY KEY (`id`) ) ENGINE=InnoDB AUTO_INCREMENT=0 DEFAULT CHARSET=utf8;

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• How to fine tune FluentNHibernate's auto mapper?

  - by Venemo

  Okay, so yesterday I managed to get the latest trunk builds of NHibernate and FluentNHibernate to work with my latest little project. (I'm working on a bug tracking application.) I created a nice data access layer using the Repository pattern. I decided that my entities are nothing special, and also that with the current maturity of ORMs, I don't want to hand-craft the database. So, I chose to use FluentNHibernate's auto mapping feature with NHibernate's "hbm2ddl.auto" property set to "create". It really works like a charm. I put the NHibernate configuration in my app domain's config file, set it up, and started playing with it. (For the time being, I created some unit tests only.) It created all tables in the database, and everything I need for it. It even mapped my many-to-many relationships correctly. However, there are a few small glitches: All of the columns created in the DB allow null. I understand that it can't predict which properties should allow null and which shouldn't, but at least I'd like to tell it that it should allow null only for those types for which null makes sense in .NET (eg. non-nullable value types shouldn't allow null). All of the nvarchar and varbinary columns it created, have a default length of 255. I would prefer to have them on max instead of that. Is there a way to tell the auto mapper about the two simple rules above? If the answer is no, will it work correctly if I modify the tables it created? (So, if I set some columns not to allow null, and change the allowed length for some other, will it correctly work with them?) EDIT: I managed to achieve the above by using Fluent NHibernate's convention API. Thanks to everyone who helped! However, there is one more thing: after checking out the convention API, I really would like my IDs to be calld "ID", not "Id", but it seems to me that the PrimaryKey.Name.Is(x => "ID") is not working at all. If I add it to the conventions collection and rewrite my entities' properties to "ID" instead of "Id", it throws an exception that there is no primary key mapped. Any thoughts on this?

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• If we don't like it for the presentation layer, then why do we tolerate it for the behavior layer?

  - by greim

  Suppose CSS as we know it had never been invented, and the closest we could get was to do this: <script> // this is the page's stylesheet $(document).ready(function(){ $('.error').css({'color':'red'}); $('a[href]').css({'textDecoration':'none'}); ... }); </script> If this was how we were forced to write code, would we put up with it? Or would every developer on Earth scream at browser vendors until they standardized upon CSS, or at least some kind of declarative style language? Maybe CSS isn't perfect, but hopefully it's obvious how it's better than the find things, do stuff method shown above. So my question is this. We've seen and tasted of the glory of declarative binding with CSS, so why, when it comes to the behavioral/interactive layer, does the entire JavaScript community seem complacent about continuing to use the kludgy procedural method described above? Why for example is this considered by many to be the best possible way to do things: <script> $(document).ready(function(){ $('.widget').append("<a class='button' href='#'>...</div>"); $('a[href]').click(function(){...}); ... }); </script> Why isn't there a massive push to get XBL2.0 or .htc files or some kind of declarative behavior syntax implemented in a standard way across browsers? Is this recognized as a need by other web development professionals? Is there anything on the horizon for HTML5? (Caveats, disclaimers, etc: I realize that it's not a perfect world and that we're playing the hand we've been dealt. My point isn't to criticize the current way of doing things so much as to criticize the complacency that exists about the current way of doing things. Secondly, event delegation, especially at the root level, is a step closer to having a declarative behavior layer. It solves a subset of the problem, but it can't create UI elements, so the overall problem remains.)

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• How to check for palindrome using Python logic

  - by DrOnline

  My background is only a 6 month college class in basic C/C++, and I'm trying to convert to Python. I may be talking nonsense, but it seems to me C, at least at my level, is very for-loop intensive. I solve most problems with these loops. And it seems to me the biggest mistake people do when going from C to Python is trying to implement C logic using Python, which makes things run slowly, and it's just not making the most of the language. I see on this website: http://hyperpolyglot.org/scripting (serach for "c-style for", that Python doesn't have C-style for loops. Might be outdated, but I interpret it to mean Python has its own methods for this. I've tried looking around, I can't find much up to date (Python 3) advice for this. How can I solve a palindrome challenge in Python, without using the for loop? I've done this in C in class, but I want to do it in Python, on a personal basis. The problem is from the Euler Project, great site btw. def isPalindrome(n): lst = [int(n) for n in str(n)] l=len(lst) if l==0 || l==1: return True elif len(lst)%2==0: for k in range (l) ##### else: while (k<=((l-1)/2)): if (list[]): ##### for i in range (999, 100, -1): for j in range (999,100, -1): if isPalindrome(i*j): print(i*j) break I'm missing a lot of code here. The five hashes are just reminders for myself. Concrete questions: 1) In C, I would make a for loop comparing index 0 to index max, and then index 0+1 with max-1, until something something. How to best do this in Python? 2) My for loop (in in range (999, 100, -1), is this a bad way to do it in Python? 3) Does anybody have any good advice, or good websites or resources for people in my position? I'm not a programmer, I don't aspire to be one, I just want to learn enough so that when I write my bachelor's degree thesis (electrical engineering), I don't have to simultaneously LEARN an applicable programming language while trying to obtain good results in the project. "How to go from basic C to great application of Python", that sort of thing. 4) Any specific bits of code to make a great solution to this problem would also be appreciated, I need to learn good algorithms.. I am envisioning 3 situations. If the value is zero or single digit, if it is of odd length, and if it is of even length. I was planning to write for loops... PS: The problem is: Find the highest value product of two 3 digit integers that is also a palindrome.

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• Internationalization of static pages with Rails

  - by Gavin

  I feel like I'm missing something really simple and I keep spinning my wheels on this problem. I currently have internationalization working throughout my app. The translations work and the routes work perfectly. At least, most of the site works with the exception of the routes to my two static pages, my "About" and "FAQ" pages. Every other link throughout the app points to the proper localized route. For example if I select "french" as my language, links point to the appropriate "(/:locale)/controller(.:format)." However, despite the changes I make throughout the app my links for the "About" and "FAQ" refuse to point to "../fr/static/about" and always point to "/static/about." To make matters stranger, when I run rake routes I see: "GET (/:locale)/static/:permalink(.:format) pages#show {:locale=/en|fr/}" and when I manually type in "../fr/static/about" the page translates perfectly. My Routes file: devise_for :users scope "(:locale)", :locale => /en|fr/ do get 'static/:permalink', :controller => 'pages', :action => 'show' resources :places, only: [:index, :show, :destroy] resources :homes, only: [:index, :show] match '/:locale' => 'places#index' get '/'=>'places#index',:as=>"root" end My ApplicationController: before_filter :set_locale def set_locale I18n.locale=params[:locale]||I18n.default_locale end def default_url_options(options={}) logger.debug "default_url_options is passed options: #{options.inspect}\n" { :locale => I18n.locale } end and My Pages Controller: class PagesController < ApplicationController before_filter :validate_page PAGES = ['about_us', 'faq'] def show render params[:permalink] end def validate_page redirect_to :status => 404 unless PAGES.include?(params[:permalink]) end end I'd be very grateful for any help ... it's just been one of those days. Edit: Thanks to Terry for jogging me to include views. <div class="container-fluid nav-collapse"> <ul class="nav"> <li class="dropdown"> <a href="#" class="dropdown-toggle" data-toggle="dropdown"><%= t(:'navbar.about') %><b class="caret"></b></a> <ul class="dropdown-menu"> <li><%=link_to t(:'navbar.about_us'), "/static/about_us"%></li> <li><%=link_to t(:'navbar.faq'), "/static/faq"%></li> <li><%=link_to t(:'navbar.blog'), '#' %></li> </ul> </li>

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• RAD Visual Web Application Creator/ Builder/ Designer for PHP

  - by inhoue

  Hi all, I want to see if any of you know a (free and open source will be ideal) tool/ app that can help build a php web application very quickly without investing too much time on writing codes, preferring drag and drop/ point and click work-flow designer for logic design (see Agile from Outsystems below). Plus, visual designer for the business logic is great since it can help a developer visualize the logic better. There are a lot of GUI builders, form builders out there, but I am looking for one app for the entire web application development process. My goal is to find an application that a team of developers can use together and use the build-in code of the app as much as possible. E.g. the app will provide a modular just for handle user login or a shopping cart; a developer just need to drag and drop the modular to the logic designer and the code will be generated. This way the functionality will be in a module and code will always be standard across developers. So if a new developer get on-board, he will just need to use the system and get up and running quickly. To explain this better: there is a lot php frameworks, e.g. cakephp, CodeIgniter, etc which I can use to help coding, but still I need to create (code) the GUI, writing quite a bit of codes. I am looking for a tool/ app that is a little more high level than those frameworks. Here is 2 examples apps I found during my google search which they have visual logic designer and gui builder in one single app. Also a single click deployment (but I need it to be php apps or at least I can deploy the (php) code to a LAMP/ WAMP server): Wavemaker: for JAVA Agile from Outsystems: for JAVA or .net (This one is really good, with work-flow drag and drop logic designer!) Talend: it is just an ETL tool, but the concept is what I want to bring up. Drag and drop, point and click logic design. Custom code can be added if it is needed, but the drag and drop process already finished the structure and most of the coding of the web app one needs to build. I want to list Adobe Flex, but it is more like a GUI designer + IDE, not exactly what I want to describe here. The drag and drop/ work-flow logic designer is a key for the app. I could go for the CMS route by learning how to extend them, but it is not that flexible for me and is a long learning curve. Anybody came across this type of app before? Or any idea of how can I find those apps? I googled them for long time, I don't see any of them for php and just few (just 2) for Java. Thanks in advance!

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• Estimating the boundary of arbitrarily distributed data

  - by Dave

  I have two dimensional discrete spatial data. I would like to make an approximation of the spatial boundaries of this data so that I can produce a plot with another dataset on top of it. Ideally, this would be an ordered set of (x,y) points that matplotlib can plot with the plt.Polygon() patch. My initial attempt is very inelegant: I place a fine grid over the data, and where data is found in a cell, a square matplotlib patch is created of that cell. The resolution of the boundary thus depends on the sampling frequency of the grid. Here is an example, where the grey region are the cells containing data, black where no data exists. OK, problem solved - why am I still here? Well.... I'd like a more "elegant" solution, or at least one that is faster (ie. I don't want to get on with "real" work, I'd like to have some fun with this!). The best way I can think of is a ray-tracing approach - eg: from xmin to xmax, at y=ymin, check if data boundary crossed in intervals dx y=ymin+dy, do 1 do 1-2, but now sample in y An alternative is defining a centre, and sampling in r-theta space - ie radial spokes in dtheta increments. Both would produce a set of (x,y) points, but then how do I order/link neighbouring points them to create the boundary? A nearest neighbour approach is not appropriate as, for example (to borrow from Geography), an isthmus (think of Panama connecting N&S America) could then close off and isolate regions. This also might not deal very well with the holes seen in the data, which I would like to represent as a different plt.Polygon. The solution perhaps comes from solving an area maximisation problem. For a set of points defining the data limits, what is the maximum contiguous area contained within those points To form the enclosed area, what are the neighbouring points for the nth point? How will the holes be treated in this scheme - is this erring into topology now? Apologies, much of this is me thinking out loud. I'd be grateful for some hints, suggestions or solutions. I suspect this is an oft-studied problem with many solution techniques, but I'm looking for something simple to code and quick to run... I guess everyone is, really! Cheers, David

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• Copying metadata over a database link in Oracle 10g

  - by Tunde

  Thanks in advance for your help experts. I want to be able to copy over database objects from database A into database B with a procedure created on database B. I created a database link between the two and have tweaked the get_ddl function of the dbms_metadata to look like this: create or replace function GetDDL ( p_name in MetaDataPkg.t_string p_type in MetaDataPkg.t_string ) return MetaDataPkg.t_longstring is -- clob v_clob clob; -- array of long strings c_SYSPrefix constant char(4) := 'SYS_'; c_doublequote constant char(1) := '"'; v_longstrings metadatapkg.t_arraylongstring; v_schema metadatapkg.t_string; v_fullength pls_integer := 0; v_offset pls_integer := 0; v_length pls_integer := 0; begin SELECT DISTINCT OWNER INTO v_schema FROM all_objects@ENTORA where object_name = upper(p_name); -- get DDL v_clob := dbms_metadata.get_ddl(p_type, upper(p_name), upper(v_schema)); -- get CLOB length v_fullength := dbms_lob.GetLength(v_clob); for nIndex in 1..ceil(v_fullength / 32767) loop v_offset := v_length + 1; v_length := least(v_fullength - (nIndex - 1) * 32767, 32767); dbms_lob.read(v_clob, v_length, v_offset, v_longstrings(nIndex)); -- Remove table’s owner from DDL string: v_longstrings(nIndex) := replace( v_longstrings(nIndex), c_doublequote || user || c_doublequote || '.', '' ); -- Remove the following from DDL string: -- 1) "new line" characters (chr(10)) -- 2) leading and trailing spaces v_longstrings(nIndex) := ltrim(rtrim(replace(v_longstrings(nIndex), chr(10), ''))); end loop; -- close CLOB if (dbms_lob.isOpen(v_clob) > 0) then dbms_lob.close(v_clob); end if; return v_longstrings(1); end GetDDL; so as to remove the schema prefix that usually comes with metadata. I get a null value whenever I run this function over the database link with the following queries. select getddl( 'TABLE', 'TABLE1') from user_tables@ENTORA where table_name = 'TABLE1'; select getddl( 'TABLE', 'TABLE1') from dual@ENTORA; t_string is varchar2(30) t_longstring is varchar2(32767) and type t_ArrayLongString is table of t_longstring I would really appreciate it if any one could help. Many thanks.

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• Neo4j 1.9.4 (REST Server,CYPHER) performance issue

  - by user2968943

  I have Neo4j 1.9.4 installed on 24 core 24Gb ram (centos) machine and for most queries CPU usage spikes goes to 200% with only few concurrent requests. Domain: some sort of social application where few types of nodes(profiles) with 3-30 text/array properties and 36 relationship types with at least 3 properties. Most of nodes currently has ~300-500 relationships. Current data set footprint(from console): LogicalLogSize=4294907 (32MB) ArrayStoreSize=1675520 (12MB) NodeStoreSize=1342170 (10MB) PropertyStoreSize=1739548 (13MB) RelationshipStoreSize=6395202 (48MB) StringStoreSize=1478400 (11MB) which is IMHO really small. most queries looks like this one(with more or less WITH .. MATCH .. statements and few queries with variable length relations but the often fast): START targetUser=node({id}), currentUser=node({current}) MATCH targetUser-[contact:InContactsRelation]->n, n-[:InLocationRelation]->l, n-[:InCategoryRelation]->c WITH currentUser, targetUser,n, l,c, contact.fav is not null as inFavorites MATCH n<-[followers?:InContactsRelation]-() WITH currentUser, targetUser,n, l,c,inFavorites, COUNT(followers) as numFollowers RETURN id(n) as id, n.name? as name, n.title? as title, n._class as _class, n.avatar? as avatar, n.avatar_type? as avatar_type, l.name as location__name, c.name as category__name, true as isInContacts, inFavorites as isInFavorites, numFollowers it runs in ~1s-3s(for first run) and ~1s-70ms (for consecutive and it depends on query) and there is about 5-10 queries runs for each impression. Another interesting behavior is when i try run query from console(neo4j) on my local machine many consecutive times(just press ctrl+enter for few seconds) it has almost constant execution time but when i do it on server it goes slower exponentially and i guess it somehow related with my problem. Problem: So my problem is that neo4j is very CPU greedy(for 24 core machine its may be not an issue but its obviously overkill for small project). First time i used AWS EC2 m1.large instance but over all performance was bad, during testing, CPU always was over 100%. Some relevant parts of configuration: neostore.nodestore.db.mapped_memory=1280M wrapper.java.maxmemory=8192 note: I already tried configuration where all memory related parameters where HIGH and it didn't worked(no change at all). Question: Where to digg? configuration? scheme? queries? what i'm doing wrong? if need more info(logs, configs) just ask ;)

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• How to set which version of the VC++ runtime Visual Studio 2005 targets

  - by TallGuy

  I have an application that contains a VC++ project (along with C# projects). Previously, (i.e. during the last year or so) when a build has been done, Visual Studio 2005 appears to be targeting the VC++ runtime version 8.0.50727.762. At least, that is what the Assembly.dll.intermediate.manifest file is telling me: <?xml version='1.0' encoding='UTF-8' standalone='yes'?> <assembly xmlns='urn:schemas-microsoft-com:asm.v1' manifestVersion='1.0'> <dependency> <dependentAssembly> <assemblyIdentity type='win32' name='Microsoft.VC80.CRT' version='8.0.50727.762' processorArchitecture='x86' publicKeyToken='1fc8b3b9a1e18e3b' /> </dependentAssembly> </dependency> </assembly> This version number matches the Visual Studio 2005 version number. The application worked fine when deployed to the webserver. The sun was shining, the birds were singing and all was right with the world. Now something has changed. I don't know what - a security patch, an obscure Visual Studio setting or something. Now Visual Studio 2005 seems to be targeting the wrong version of the VC++ runtime: <?xml version='1.0' encoding='UTF-8' standalone='yes'?> <assembly xmlns='urn:schemas-microsoft-com:asm.v1' manifestVersion='1.0'> <dependency> <dependentAssembly> <assemblyIdentity type='win32' name='Microsoft.VC80.CRT' version='8.0.50727.4053' processorArchitecture='x86' publicKeyToken='1fc8b3b9a1e18e3b' /> </dependentAssembly> </dependency> </assembly> When I deploy the application to the webserver, I get the dreaded This application has failed to start because the application configuration is incorrect. Reinstalling the application may fix this problem. (Exception from HRESULT: 0x800736B1) error. This problem occurs even when I recompile previous versions of the application. I can absolutely guarantee that nothing at all has changed in the solution - we zip up the entire contents of the solution as part of the build process and archive it. I have unzipped a number of these to a temp directory, verified that the previous manifest file refers to 8.0.50727.762, recompiled using exactly the same command at the command line and then verified that the new manifest file now refers to 8.0.50727.4053. I am using Microsoft Visual Studio 2005 Version 8.0.50727.762 (SP.050727-7600) and Microsoft Visual C++ 2005 77646-008-0000007-41610. Why would Visual Studio revert to a previous version of the VC++ runtime? How do I specify which version it should use? What is going wrong here?

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• Exporting classes containing std:: objects (vector, map, etc) from a dll

  - by RnR

  I'm trying to export classes from a DLL that contain objects such as std::vectors and std::stings - the whole class is declared as dll export through: class DLL_EXPORT FontManager { The problem is that for members of the complex types I get this warning: warning C4251: 'FontManager::m__fonts' : class 'std::map<_Kty,_Ty' needs to have dll-interface to be used by clients of class 'FontManager' with [ _Kty=std::string, _Ty=tFontInfoRef ] I'm able to remove some of the warnings by putting the following forward class declaration before them even though I'm not changing the type of the member variables themselves: template class DLL_EXPORT std::allocator<tCharGlyphProviderRef>; template class DLL_EXPORT std::vector<tCharGlyphProviderRef,std::allocator<tCharGlyphProviderRef> >; std::vector<tCharGlyphProviderRef> m_glyphProviders; Looks like the forward declaration "injects" the DLL_EXPORT for when the member is compiled but is it safe? Does it realy change anything when the client compiles this header and uses the std container on his side? Will it make all future uses of such a container DLL_EXPORT (and possibly not inline?)? And does it really solve the problem that the warning tries to warn about? Is this warning anything I should be worried about or would it be best to disable it in the scope of these constructs? The clients and the dll will always be built using the same set of libraries and compilers and those are header only classes... I'm using Visual Studio 2003 with the standard STD library. ---- Update ---- I'd like to target you more though as I see the answers are general and here we're talking about std containers and types (such as std::string) - maybe the question really is: Can we disable the warning for standard containers and types available to both the client and the dll through the same library headers and treat them just as we'd treat an int or any other built-in type? (It does seem to work correctly on my side.) If so would should be the conditions under which we can do this? Or should maybe using such containers be prohibited or at least ultra care taken to make sure no assignment operators, copy constructors etc will get inlined into the dll client? In general I'd like to know if you feel designing a dll interface having such objects (and for example using them to return stuff to the client as return value types) is a good idea or not and why - I'd like to have a "high level" interface to this functionality... maybe the best solution is what Neil Butterworth suggested - creating a static library?

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• JQuery validation not working for checkbox group

  - by Chris Halcrow

  I'm having trouble getting JQuery validation to work with a set of checkboxes. I'm generating the checkboxes using an ASP.NET checkboxlist, and I've used JQuery to set the 'name' attribute to the same thing for each checkbox in the list. Here's the code that gets written to the browser. I'm setting the 'validate' attribute on the 1st checkbox to set the rule that at least one checkbox must be selected. The JQuery validation works for all other elements on the form, but not for the checkbox list. I'm also using a JQuery form wizard on the page which triggers validation for each 'page' of the form, so I don't have control over how the validation is called. <input id="ContentPlaceHolder1_MainContent_AreaOfInterest_0" class="ui-wizard-content ui-helper-reset ui-state-default" type="checkbox" value="Famine" name="hello[]" validate="required:true, minlength:1"> <label for="ContentPlaceHolder1_MainContent_AreaOfInterest_0">Famine</label> <br> <input id="ContentPlaceHolder1_MainContent_AreaOfInterest_1" class="ui-wizard-content ui-helper-reset ui-state-default" type="checkbox" value="Events Volunteer" name="hello[]"> <label for="ContentPlaceHolder1_MainContent_AreaOfInterest_1">Events Volunteer</label> Any ideas on what's going wrong? There are lots of examples of JQuery scripts that will do the validation, however I'm trying to avoid this as I'm generating the checkboxlist server side by a custom control so that it can be re-used across different pages that may or may not have JQuery enabled. I'm trying to enable the JQuery validation whilst being as unobtrusive as possible, so that pages will still work even if JQuery is disabled. Here are the relevant JQuery inclusions and JQuery initialisation script for the form wizard. I'm not using any initialisation code for JQuery validation: <script type="text/javascript" src="../js/formwizard/js/bbq.js"></script> <script type="text/javascript" src="../js/formwizard/js/jquery.form.js"></script> <script type="text/javascript" src="../js/formwizard/js/jquery.form.wizard.js"></script> <script type="text/javascript" src="../js/formwizard/js/jquery.validate.js"></script> <script type="text/javascript"> $(document).ready(function () { $("#form1").formwizard({ validationEnabled: true, focusFirstInput: true }); }); </script>

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• Is this a legitimate implementation of a 'remember me' function for my web app?

  - by user246114

  Hi, I'm trying to add a "remember me" feature to my web app to let a user stay logged in between browser restarts. I think I got the bulk of it. I'm using google app engine for the backend which lets me use java servlets. Here is some pseudo-code to demo: public class MyServlet { public void handleRequest() { if (getThreadLocalRequest().getSession().getAttribute("user") != null) { // User already has session running for them. } else { // No session, but check if they chose 'remember me' during // their initial login, if so we can have them 'auto log in' // now. Cookie[] cookies = getThreadLocalRequest().getCookies(); if (cookies.find("rememberMePlz").exists()) { // The value of this cookie is the cookie id, which is a // unique string that is in no way based upon the user's // name/email/id, and is hard to randomly generate. String cookieid = cookies.find("rememberMePlz").value(); // Get the user object associated with this cookie id from // the data store, would probably be a two-step process like: // // select * from cookies where cookieid = 'cookieid'; // select * from users where userid = 'userid fetched from above select'; User user = DataStore.getUserByCookieId(cookieid); if (user != null) { // Start session for them. getThreadLocalRequest().getSession() .setAttribute("user", user); } else { // Either couldn't find a matching cookie with the // supplied id, or maybe we expired the cookie on // our side or blocked it. } } } } } // On first login, if user wanted us to remember them, we'd generate // an instance of this object for them in the data store. We send the // cookieid value down to the client and they persist it on their side // in the "rememberMePlz" cookie. public class CookieLong { private String mCookieId; private String mUserId; private long mExpirationDate; } Alright, this all makes sense. The only frightening thing is what happens if someone finds out the value of the cookie? A malicious individual could set that cookie in their browser and access my site, and essentially be logged in as the user associated with it! On the same note, I guess this is why the cookie ids must be difficult to randomly generate, because a malicious user doesn't have to steal someone's cookie - they could just randomly assign cookie values and start logging in as whichever user happens to be associated with that cookie, if any, right? Scary stuff, I feel like I should at least include the username in the client cookie such that when it presents itself to the server, I won't auto-login unless the username+cookieid match in the DataStore. Any comments would be great, I'm new to this and trying to figure out a best practice. I'm not writing a site which contains any sensitive personal information, but I'd like to minimize any potential for abuse all the same, Thanks

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• Migrating from hand-written persistence layer to ORM

  - by Sergey Mikhanov

  Hi community, We are currently evaluating options for migrating from hand-written persistence layer to ORM. We have a bunch of legacy persistent objects (~200), that implement simple interface like this: interface JDBC { public long getId(); public void setId(long id); public void retrieve(); public void setDataSource(DataSource ds); } When retrieve() is called, object populates itself by issuing handwritten SQL queries to the connection provided using the ID it received in the setter (this usually is the only parameter to the query). It manages its statements, result sets, etc itself. Some of the objects have special flavors of retrive() method, like retrieveByName(), in this case a different SQL is issued. Queries could be quite complex, we often join several tables to populate the sets representing relations to other objects, sometimes join queries are issued on-demand in the specific getter (lazy loading). So basically, we have implemented most of the ORM's functionality manually. The reason for that was performance. We have very strong requirements for speed, and back in 2005 (when this code was written) performance tests has shown that none of mainstream ORMs were that fast as hand-written SQL. The problems we are facing now that make us think of ORM are: Most of the paths in this code are well-tested and are stable. However, some rarely-used code is prone to result set and connection leaks that are very hard to detect We are currently squeezing some additional performance by adding caching to our persistence layer and it's a huge pain to maintain the cached objects manually in this setup Support of this code when DB schema changes is a big problem. I am looking for an advice on what could be the best alternative for us. As far as I know, ORMs has advanced in last 5 years, so it might be that now there's one that offers an acceptable performance. As I see this issue, we need to address those points: Find some way to reuse at least some of the written SQL to express mappings Have the possibility to issue native SQL queries without the necessity to manually decompose their results (i.e. avoid manual rs.getInt(42) as they are very sensitive to schema changes) Add a non-intrusive caching layer Keep the performance figures. Is there any ORM framework you could recommend with regards to that?

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