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  • Can getAttribute() method of Tomcat ServletContext implementation be called without synchronization?

    - by oo_olo_oo
    I would like to read some parameters during servlet initializtion (in init() method), and store them among servlet context attributes (using getServletContext().setAttribute()). I would like to read these parameters later - during some request processing (using getServletContext().getAttribute()). So, the multiple threads could do this simultaneously. My question is if such an attempt is safe? Could I be sure that multi threaded calls to the getAttribute() don't mess up any internal state of the servlet context? Please take into account that I'm not going to call the setAttribute() anywhere besides the initialization. So, only calls to the getAttribute() are going to be done from multiple threads. But depending on the internal implementation, this also could be dangerous. So, any information about Tomcat's implementation would be appreciated.

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  • How do I prevent JDialog from showing in gnome-panel(Linux)?

    - by aeter
    I have a class: public class ANote extends JDialog{...} In GNOME(Linux) it shows an entry in the gnome-panel. I want it to show nothing (the same way it does in the taskbar in Windows), because there may be present several instances of the class simultaneously, and this overcrowds the gnome-panel. How do I prevent it from showing an instance in the gnome-panel? EDIT: So far I have tried playing with the modality, which hides it from the gnome-panel, but blocks the main frame of the application behind the ANote instances.

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  • Casting of object for a class loaded at runtime

    - by Steven
    hi, i load a class using Class.forName(klassname,false,loader) After this i create an instance using klass.newInstance(); It returns an object type.I want to cast it to specific type(ie.Klassnamw instance).I used normal casting but it gets hung because it is not resolved during runtime.How can i cast it?Hellp

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  • log4j rootLogger seems to inherit log level of other logger. Why?

    - by AndrewR
    I've got a log4J setup in which the root logger is supposed to log ERROR level messages and above to the console and another logger logs everything to syslog. log4j.properties is: # Root logger option log4j.rootLogger=ERROR,R log4j.appender.R=org.apache.log4j.ConsoleAppender log4j.appender.R.layout=org.apache.log4j.PatternLayout log4j.appender.R.layout.ConversionPattern=%d %p %t %c - %m%n log4j.logger.SGSearch=DEBUG,SGSearch log4j.appender.SGSearch=org.apache.log4j.net.SyslogAppender log4j.appender.SGSearch.SyslogHost=localhost log4j.appender.SGSearch.Facility=LOCAL6 log4j.appender.SGSearch.layout=org.apache.log4j.PatternLayout log4j.appender.SGSearch.layout.ConversionPattern=[%-5p] %m%n In code I do private static final Logger logger = Logger.getLogger("SGSearch"); . . . logger.info("Commencing snapshot index [" + args[1] + " -> " + args[2] + "]"); What is happening is that I get the console logging for all logging levels. What seems to be happening is that the level for SGSearch overrides the level set for the root logger somehow. I can't figure it out. I have confirmed that Log4J is reading then properties file I think it is, and no other (via the -Dlog4j.debug option)

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  • displaying data from database in to text box

    - by srinayak
    I have 2 JSP pages as below: projectcategory.jsp <% Connection con = DbConnect.connect(); Statement s = con.createStatement(); ResultSet rs = s.executeQuery("select * from projectcategory"); %> <DIV class="TabbedPanelsContent" align="center"> <TABLE border="1"> <TR> <TH>CATEGORY ID</TH> <TH>CATEGORY NAME</TH> <TH>Edit/Update</TH> </TR> <% while (rs.next()) { %> <%String p=rs.getString(1);%> <TR> <TD><%=rs.getString(1)%></TD> <TD><%=rs.getString(2)%></TD> <TD> <FORM action="EditPcat.jsp?pcatid=p"><INPUT type="submit" value='edit/update'></INPUT> </FORM> </TD> </TR> <% } %> </TABLE> </DIV> another is Editpcat.jsp: </head> <body> <%String s=request.getParameter("p"); %> <form action="ProjCatServlet" method="post"> <div align="right"><a href="projectcategory.jsp">view</a></div> <fieldset> <legend>Edit category</legend> <table cellspacing="2" cellpadding="2" border="0"> <tr> <td align="left">Category Id</td> <td><input type="text" name="pcatid" value="<%=s%>" ></td> </tr> <tr> <td align="right">Category Name</td> <td><input type="text" name="pcatname"></td> </tr> <tr> <td><input type="submit" value="submit"></td> </tr> </table> <input type="hidden" name="FUNCTION_ID" value="UPDATE"> </fieldset> </form> How to display value from one JSP page which we get from database in to text box of another JSP?

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  • ResultSet and aggregation

    - by kachanov
    Ok, I admit my situation is special There is a data system that supports SQL-92 and JDBC interface However the SQL requets are pretty expensive, and in my application I need to retreive the same data multiple times and aggregate it ("group by") on different fields to show different dimensions of the same data. For example on one screen I have three tables that show the same set or records but aggregated by City (1st grid), by Population (2nd grid), by number of babies (3rd grid) This amounts to 3 SQL queries (which is very slow), UNLESS anyone of you can suggest any idea any library from apache commons or from google code, so that I can select all records into ResultSet and get 3 arrays of data group by different fields from this single ResultSet. Am I'm missing some obvious and unexpected solution to this problem?

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  • JAXB doesn't unmarshal list of interfaces

    - by Joker_vD
    It seems JAXB can't read what it writes. Consider the following code: interface IFoo { void jump(); } @XmlRootElement class Bar implements IFoo { @XmlElement public String y; public Bar() { y = ""; } public Bar(String y) { this.y = y; } @Override public void jump() { System.out.println(y); } } @XmlRootElement class Baz implements IFoo { @XmlElement public int x; public Baz() { x = 0; } public Baz(int x) { this.x = x; } @Override public void jump() { System.out.println(x); } } @XmlRootElement public class Holder { private List<IFoo> things; public Holder() { things = new ArrayList<>(); } @XmlElementWrapper @XmlAnyElement public List<IFoo> getThings() { return things; } public void addThing(IFoo thing) { things.add(thing); } } // ... try { JAXBContext context = JAXBContext.newInstance(Holder.class, Bar.class, Baz.class); Holder holder = new Holder(); holder.addThing(new Bar("1")); holder.addThing(new Baz(2)); holder.addThing(new Baz(3)); for (IFoo thing : holder.getThings()) { thing.jump(); } StringWriter s = new StringWriter(); context.createMarshaller().marshal(holder, s); String data = s.toString(); System.out.println(data); StringReader t = new StringReader(data); Holder holder2 = (Holder)context.createUnmarshaller().unmarshal(t); for (IFoo thing : holder2.getThings()) { thing.jump(); } } catch (Exception e) { System.err.println(e.getMessage()); } It's a simplified example, of course. The point is that I have to store two very differently implemented classes, Bar and Baz, in one collection. Well, I observed that they have pretty similar public interface, so I created an interface IFoo and made them two to implement it. Now, I want to have tools to save and load this collection to/from XML. Unfortunately, this code doesn't quite work: the collection is saved, but then it cannot be loaded! The intended output is 1 2 3 some xml 1 2 3 But unfortunately, the actual output is 1 2 3 some xml com.sun.org.apache.xerces.internal.dom.ElementNSImpl cannot be cast to testapplication1.IFoo Apparently, I need to use the annotations in a different way? Or to give up on JAXB and look for something else? I, well, can write "XMLNode toXML()" method for all classes I wan't to (de)marshal, but...

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  • How to get result size from an SQL query and check size

    - by Jimmy
    Hi I'm trying to write a piece of code for a simple verification method as part of a MVC. At present the SQL is not written as a prepared statement so obviously it is at risk to a SQL injection so any help in regards to writing the SQL as a prepared statement would be really helpful. The method which is in the User model. public boolean getLoginInfo() { try { DBAccess dbAccess = new DBAccess(); String sql = "SELECT username, password FROM owner WHERE username = '" + this.username + "'AND password = '" + this.password + "';"; dbAccess.close();dbAccess.executeQuery(sql); dbAccess.close(); return true; } catch (Exception e) { return false; } } I want to get the size of the result set which is generated by the SQL query and if the size of it is 1 return true else it's false. If you need more info on the rest of the MVC just post and I'll get it up here.

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  • Catching an exception that is nested into another exception

    - by Bernhard V
    Hi, I want to catch an exception, that is nested into another exception. I'm doing it currently this way: } catch (RemoteAccessException e) { if (e != null && e.getCause() != null && e.getCause().getCause() != null) { MyException etrp = (MyException) e.getCause().getCause(); ... } else { throw new IllegalStateException("Error at calling service 'beitragskontonrVerwalten'"); } } Is there a way to do this more efficient and elegant?

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  • Is it possible to include JButton in a JTable?

    - by Benjamin Confino
    I have a JTable that stores the results of a database query, so far so good. What I want is for the last column in each table to have a clickible JButton that will open the edit screen for the object represented in that row, and that means the button will need to know the details of the first column in the table from its own row (the ID from the database). Any advice? I already tried just adding JButtons but they turned into Text when I tried to run it.

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  • javax.persistence.NoResultException: getSingleResult() did not retrieve any entities

    - by apple1988
    Hello, i have created a namedquery with ejb to check if the username is used. When the singleResult is null, then i get the following Exception : javax.persistence.NoResultException: getSingleResult() did not retrieve any entities But this exception is the result that i want when the username is free. ^^ Here is the code: public User getUserByUsername(String username) throws DAOException{ try{ Query q = em.createNamedQuery(User.getUserByUsername); q.setParameter("username", username); return (User) q.getSingleResult(); }catch(Exception e){ throwException(username, e); return null; } } Does anybody know what the problem is. :( I will return null andy don`t get an Exception. Thank you very much

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  • Maven: Where be the code?

    - by steve
    Greetings, Can anyone tell me how the heck I'm meant to use a maven repository or whatever the term is with a project? I've downloaded the OAuth library from Google. I run mvn compile, test, install, deploy I want to know where the Jar goes so I can just put it into my class path. Any help appreciated!

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  • Performance implications of finalizers on JVM

    - by Alexey Romanov
    According to this post, in .Net, Finalizers are actually even worse than that. Besides that they run late (which is indeed a serious problem for many kinds of resources), they are also less powerful because they can only perform a subset of the operations allowed in a destructor (e.g., a finalizer cannot reliably use other objects, whereas a destructor can), and even when writing in that subset finalizers are extremely difficult to write correctly. And collecting finalizable objects is expensive: Each finalizable object, and the potentially huge graph of objects reachable from it, is promoted to the next GC generation, which makes it more expensive to collect by some large multiple. Does this also apply to JVMs in general and to HotSpot in particular?

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  • stop thread that does not get interrupted

    - by prmatta
    I have a thread that sits and reads objects off of an ObjectInputStream: public void run() { try { ois = new ObjectInputStream(clientSocket.getInputStream()); Object o; while ((o = ois.readObject()) != null) { //do something with object } } catch (Exception ex) { //Log exception } } readObject does not throw InterruptedException and as far as I can tell, no exception is thrown when this thread is interrupted. How do I stop this thread?

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  • How to get value of h:inputText when binded in JSF

    - by Tr?n Minh Phuong
    How can i get 2 h:inputTextValue from this? <h:dataTable cellspacing="0" value="#{managerManagedBean.lstMatch}" var="m" binding="#{managerManagedBean.datatableMatch}"> <!-- cellspacing='0' is important, must stay --> <h:column> <f:facet name="header">Team One</f:facet> <h:outputText value="#{m.teamOneName}"></h:outputText> </h:column> <h:column> <f:facet name="header">Match Score</f:facet> <h:inputText value="#{m.teamOneResult}" style="width: 20px; text-align: center" binding="#{input}"></h:inputText> - <h:inputText value="#{m.teamTwoResult}" style="width: 20px; text-align: center"></h:inputText> </h:column> <h:column> <f:facet name="header">Half Time</f:facet> <h:outputText value="#{m.haveHalfTime}"></h:outputText> </h:column> <h:column> <f:facet name="header">Team Two</f:facet> <h:outputText value="#{m.teamTwoName}"></h:outputText> </h:column> <h:column> <f:facet name="header">Match Date</f:facet> <h:outputText value="#{m.matchDate}"></h:outputText> </h:column> <h:column> <f:facet name="header">Control</f:facet> <h:commandButton action="#{managerManagedBean.update(m, input.value)}" value="Update Match"> </h:commandButton> </h:column> </h:dataTable>

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  • Revalidate JPanel's parent frame

    - by Tom Brito
    I need show/hide some fields of my panel, and I want the panel to fit the frame. How could I notify to the parent frame to revalidate? I think in pass the frame to my panel's constructor, but I think may have a way this is already done. I remember that there was a protected attribute in JPanel, but there isn't.. maybe i remembering the wrong component.

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