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  • How to know file type without extension

    - by Ayusman
    While trying to come-up with a servlet based application to read files and manipulate them (image type conversion) here is a question that came up to me: Is it possible to inspect a file content and know the filetype? Is there a standard that specifies that each file MUST provide some type of marker in their content so that the application will not have to rely on the file extension constraints? Consider an application scenario: I am creating an application that will be able to convert different file formats to a set of output formats. Say user uploads an PDF, my application can suggest that the possible conversion formats are microsoft word or TIFF or JPEG etc. As my application will gradually support different file formats (over a period of time), I want my application to inspect the input file instead of having the user to specify the format. And suggest to user the possible formats of output. I understand this is an open ended, broad question. Please let me know if it needs to be modified. Thanks, Ayusman

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  • Strategies for dealing with Circular references caused by JPA relationships?

    - by ams
    I am trying to partition my application into modules by features packaged into separate jars such as feature-a.jar, feature-b.jar, ... etc. Individual feature jars such as feature-a.jar should contain all the code for a feature a including jpa entities, business logic, rest apis, unit tests, integration test ... etc. The problem I am running into is that bi-directional relationships between JPA entities cause circular references between the jar files. For example Customer entity should be in customer.jar and the Order should be in order.jar but Customer references order and order references customer making it hard to split them into separate jars / eclipse projects. Options I see for dealing with the circular dependencies in JPA entities: Option 1: Put all the entities into one jar / one project Option 2: Don't map certain bi-directianl relationships to avoid circular dependencies across projects. Questions: What rules / principles have you used to decide when to do bi-directional mapping vs. not? Have you been able to break jpa entities into their own projects / jar by features if so how did you avoid the circular dependencies issues?

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  • In this example, would Customer or AccountInfo properly be the entity group parent?

    - by Badhu Seral
    In this example, the Google App Engine documentation makes the Customer the entity group parent of the AccountInfo entity. Wouldn't AccountInfo encapsulate Customer rather than the other way around? Normally I would think of an AccountInfo class as including all of the information about the Customer. import javax.jdo.annotations.IdGeneratorStrategy; import javax.jdo.annotations.PersistenceCapable; import javax.jdo.annotations.Persistent; import javax.jdo.annotations.PrimaryKey; import com.google.appengine.api.datastore.Key; import com.google.appengine.api.datastore.KeyFactory; @PersistenceCapable public class AccountInfo { @PrimaryKey @Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY) private Key key; public void setKey(Key key) { this.key = key; } } // ... KeyFactory.Builder keyBuilder = new KeyFactory.Builder(Customer.class.getSimpleName(), "custid985135"); keyBuilder.addChild(AccountInfo.class.getSimpleName(), "acctidX142516"); Key key = keyBuilder.getKey(); AccountInfo acct = new AccountInfo(); acct.setKey(key); pm.makePersistent(acct);

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  • Is it bad practice to change state inside of an if statement?

    - by Benjamin
    I wrote some code that looks similar to the following: String SKIP_FIRST = "foo"; String SKIP_SECOND = "foo/bar"; int skipFooBarIndex(String[] list){ int index; if (list.length >= (index = 1) && list[0].equals(SKIP_FIRST) || list.length >= (index = 2) && (list[0] + "/" + list[1]).equals(SKIP_SECOND)){ return index; } return 0; } String[] myArray = "foo/bar/apples/peaches/cherries".split("/"); print(skipFooBarIndex(myArray); This changes state inside of the if statement by assigning index. However, my coworkers disliked this very much. Is this a harmful practice? Is there any reason to do it?

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  • how to Solve the "Digg" problem in MongoDB

    - by user193116
    A while back,a Digg developer had posted this blog ,"http://about.digg.com/blog/looking-future-cassandra", where the he described one of the issues that were not optimally solved in MySQL. This was cited as one of the reasons for their move to Cassandra. I have been playing with MongoDB and I would like to understand how to implement the MongoDB collections for this problem From the article, the schema for this information in MySQL : CREATE TABLE Diggs ( id INT(11), itemid INT(11), userid INT(11), digdate DATETIME, PRIMARY KEY (id), KEY user (userid), KEY item (itemid) ) ENGINE=InnoDB DEFAULT CHARSET=utf8; CREATE TABLE Friends ( id INT(10) AUTO_INCREMENT, userid INT(10), username VARCHAR(15), friendid INT(10), friendname VARCHAR(15), mutual TINYINT(1), date_created DATETIME, PRIMARY KEY (id), UNIQUE KEY Friend_unique (userid,friendid), KEY Friend_friend (friendid) ) ENGINE=InnoDB DEFAULT CHARSET=utf8; This problem is ubiquitous in social networking scenario implementation. People befriend a lot of people and they in turn digg a lot of things. Quickly showing a user what his/her friends are up to is very critical. I understand that several blogs have since then provided a pure RDBMs solution with indexes for this issue; however I am curious as to how this could be solved in MongoDB.

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  • Multi-module Maven build

    - by Don
    Hi, My project has a fairly deep graph of Maven modules. The root POM has the following plugin configured <plugins> <plugin> <groupId>org.jvnet</groupId> <artifactId>animal-sniffer</artifactId> <version>1.2</version> <configuration> <signature> <groupId>org.jvnet.animal-sniffer</groupId> <artifactId>java1.4</artifactId> <version>1.0</version> </signature> </configuration> </plugin> </plugins> If I invoke this target from the command line in the root directory via: mvn animal-sniffer:check Then it works fine as long as the current module extends (either directly or indirectly) from the root POM. However there are many children (or grandchildren) of the root module, which do not inherit from that module's POM. In this case, the goal fails because it cannot find the necessary configuration [ERROR] BUILD ERROR [INFO] ------------------------------------------------------------------------ [INFO] One or more required plugin parameters are invalid/missing for 'animal-sniffer:check' [0] Inside the definition for plugin 'animal-sniffer' specify the following: <configuration> ... <signature>VALUE</signature> </configuration>. When configuring this plugin in the root module, is there any way to exclude a list of sub-modules either by name, or by packaging type? Thanks, Donal

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  • I18n - JSF variable value translation

    - by Yurish
    Hi! I am using Bundle Internationalization in my project. I have initialized bundle via <f:loadBundle basename="ui.all.bundles.AppResources_en" var="msg"/> When i need to translate some text, i am using a key to resourceBundle, to get a value of it, for example: #{msg.someText}. But, now i want to translate text, which key is a value of another variable. For example: I have variable String textToTransl. It`s value is status_booked. In my AppResources is defined, that status_booked means "It is booked!", so, when i am pointing it to #{msg.textToTransl} i need to see "It is booked!" How can i make it work?

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  • Scanner cuts off my String after about 2400 characters

    - by Ventrue
    I've got some very basic code like while (scan.hasNextLine()) { String temp = scan.nextLine(); System.out.println(temp); } where scan is a Scanner over a file. However, on one particular line, which is about 6k chars long, temp cuts out after something like 2470 characters. There's nothing special about when it cuts out; it's in the middle of the word "Australia." If I delete characters from the line, the place where it cuts out changes; e.g. if I delete characters 0-100 in the file then Scanner will get what was previously 100-2570. I've used Scanner for larger strings before. Any idea what could be going wrong?

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  • Hibernate: how to maintain insertion order

    - by jwaddell
    I have a list of entities where creation order is important, but they do not contain a timestamp to use for sorting. Entities are added to the end of the list as they are created so they will be ordered correctly in the list itself. After persisting the list using Hibernate the entities appear in the database table in the order that they were created. However when retrieving the list using a new Hibernate session the list is now in reverse order of insertion/creation. Is this expected behaviour? Is there any way to retrieve the list in the same order as it appears in the table? The primary key is a UUID, and the list of entities should always have been created on the same IP address and JVM. This mean sorting by UUID is a possibility but I'd rather not make assumptions. Another possibility is if the list is guaranteed to always come out in reverse order I could always just work through it backwards.

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  • JBoss envers and huge audit tables

    - by LeChe
    All, I am auditing my JEE application with JBoss Evers and the nature of my application causes the audit table to grow very fast. The historic data is queried infrequently and access time is not really an issue, apart from the data from the last week. This data IS queried frequently and access needs to be fast. Ideally, I would split the data and distribute it over two tables, with the older data in compressed format. Unfortunately, Envers does not allow spreading data over multiple tables as far as I can tell from the docs. Does somebody have any idea what would be the best way to achieve this (if possible while still using Envers)? Cheers, LeChe

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  • How to schedule an alarm so that the intent is broadcast everytime the date changes?

    - by rogerstone
    I want to schedule an alarm which throws an intent when the date changes. I know that this would do this the job alarms.setRepeating(AlarmManager.RTC_WAKEUP,triggerAtTime, interval,alarmIntent); But what is confusing me is what to put in the triggerAtTime and the interval.It says System.currentTimeMillis() timebase. I might be installing the app on any day so the TriggerAtTime should be midnight of that day and the interval would be 24 hours from there on. How can I acheive this.Can someone tell me what to put in TriggerAtTime and interval in the required format. Thanks

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  • Why is BorderLayout calling setSize() and setBounds()?

    - by ags
    I'm trying to get my head around proper use of the different LayoutManagers to make my GUI design skills more efficient and effective. For me, that usually requires a detailed understanding of what is going on under the hood. I've found some good discussion of the interaction and consequences of a Container using BorderLayout containing a Container using FlowLayout. I understand it for the most part, but wanted to confirm my mental model and to do so I am looking at the code for BorderLayout. In the code snippet below taken from BorderLayout.layoutContainer(), note the calls to the child Component's setSize() method followed by setBounds(). Looking at the source for these methods of Component, setSize() actually calls setBounds() with the current values for Component.x and Component.y. Why is this done (and not entirely redudant?) Doesn't the setBounds() call completely overwrite the results of the setSize() call? if ((c=getChild(NORTH,ltr)) != null) { c.setSize(right - left, c.height); Dimension d = c.getPreferredSize(); c.setBounds(left, top, right - left, d.height); top += d.height + vgap; } I'm also tring to understand where/when the child Component's size is initially set (before the LayoutManager.layoutContainer() method is called). Finally, this post itself raises a "meta-question": in a situation like this, where the source is available elsewhere, is the accepteed protocol to include the entire method? Or some other way to make it easier for folks to participate in the thread? Thanks.

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  • Getting field of type bytea in helper table when using GenerationType.IDENTITY

    - by dtrunk
    I'm creating my db scheme using Hibernate. There's a Table called "tbl_articles" and another one called "tbl_categories". To have a n-n relationship a helper table ("tbl_articles_categories") is needed. Here are all necessary Entities: @Entity @Table( name = "tbl_articles" ) public class Article implements Serializable { private static final long serialVersionUID = 1L; @Id @Column( nullable = false ) @GeneratedValue( strategy = GenerationType.IDENTITY ) private Integer id; // other fields... public Integer getId() { return id; } public void setId( Integer id ) { this.id = id; } // other fields... } @Entity @Table( name = "tbl_categories" ) public class Category implements Serializable { private static final long serialVersionUID = 1L; @Id @Column( nullable = false ) @GeneratedValue( strategy = GenerationType.IDENTITY ) private Integer id; // other fields public Integer getId() { return id; } public void setId( Integer id ) { this.id = id; } // other fields... } @Entity @Table( name = "tbl_articles_categories" ) @AssociationOverrides({ @AssociationOverride( name = "pk.article", joinColumns = @JoinColumn( name = "article_id" ) ), @AssociationOverride( name = "pk.category", joinColumns = @JoinColumn( name = "category_id" ) ) }) public class ArticleCategory { private ArticleCategoryPK pk = new ArticleCategoryPK(); public void setPk( ArticleCategoryPK pk ) { this.pk = pk; } @EmbeddedId public ArticleCategoryPK getPk() { return pk; } @Transient public Article getArticle() { return pk.getArticle(); } public void setArticle( Article article ) { pk.setArticle( article ); } @Transient public Category getCategory() { return pk.getCategory(); } public void setCategory( Category category ) { pk.setCategory( category ); } } @Embeddable public class ArticleCategoryPK implements Serializable { private static final long serialVersionUID = 1L; @ManyToOne @ForeignKey( name = "tbl_articles_categories_fkey_article_id" ) private Article article; @ManyToOne @ForeignKey( name = "tbl_articles_categories_fkey_category_id" ) private Category category; public ArticleCategoryPK( Article article, Category category ) { setArticle( article ); setCategory( category ); } public ArticleCategoryPK() { } public Article getArticle() { return article; } public void setArticle( Article article ) { this.article = article; } public Category getCategory() { return category; } public void setCategory( Category category ) { this.category = category; } } Now, I'm getting a serial type what I wanted in my articles table as well as in my categories table. But looking into my helper table, there aren't the expected fields article_id and category_id each of type integer - instead there are article and category of type bytea. What's wrong here? EDIT: Sorry, forgot to mention that I'm using PostgreSQL.

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  • Android app crashes on Async Task

    - by Telmo Vaz
    why is my APP crashing when I invoke the AsyncTask? public class Login extends Activity { String mail; EditText mailIn; Button btSubmit; @Override protected void onCreate(Bundle tokenArg) { super.onCreate(tokenArg); setContentView(R.layout.login); mailIn = (EditText)findViewById(R.id.usermail); btSubmit = (Button)findViewById(R.id.submit); btSubmit.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View thisView) { new LoginProc().execute(); } }); } public class LoginProc extends AsyncTask<String, Void, Void> { @Override protected void onPreExecute() { mailIn = (EditText)findViewById(R.id.usermail); mail = mailIn.getText().toString(); super.onPreExecute(); } @Override protected Void doInBackground(String... params) { Toast.makeText(getApplicationContext(), mail, Toast.LENGTH_SHORT).show(); return null; } } } I'm trying to make the String name get it's value on the preExecute method, but it happens that the app crashes on that point. Even if I take the preExecute and do that on the doInBrackground, it still crashes. What's wrong?

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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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  • Does importing of packages change visibility of classes?

    - by Roman
    I jsut learned that A class may be declared with the modifier public, in which case that class is visible to all classes everywhere. If a class has no modifier (the default, also known as package-private), it is visible only within its own package. This is a clear statement. But this information interfere with my understanding of importing of packages (which easily can be wrong). I thought that importing a package I make classes from the imported package visible to the importing class. So, how does it work? Are public classes visible to all classes everywhere under condition that the package containing the public class is imported? Or there is not such a condition? What about the package-private classes? They are invisible no mater if the containing package was imported or not? ADDED: It seems to me that I got 2 answers which are marked as good (up-voted) and which contradict eachother.

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  • Image Uploading in a web aplication.

    - by sandeep manglani
    actually i m devloping a web application that provides facility to users upload the image as we see in orkut and facebook through a form and a upload button.but the actually problem I am facing is : 1.should i store the image in database using Large data objects ie BLOB and the problem arises of retrieving it back from the database and then displaying it on the form. 2.sholud i store the absolute path of the the image in database and provide it to the source tag of the image in the html form.

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  • Problem in setting backgound color to my TreeCellRenderer

    - by Sunil Kumar Sahoo
    Hi I have cretaed my own renderer. I want the back ground should be blue. I have set background color as blue also. But I donot know what is tha problem that the background color of my renderer always seems to be white. I have post the code. please help where I am wrong so that the background color becomes white. class CheckTreeCellRenderer extends JPanel implements TreeCellRenderer { private CheckTreeSelectionModel selectionModel; private MyRenderer delegate; private TristateCheckBox checkBox = new TristateCheckBox("", null, true); public static final State NOT_SELECTED = new State(); public static final State SELECTED = new State(); public static final State DONT_CARE = new State(); public CheckTreeCellRenderer(MyRenderer delegate, CheckTreeSelectionModel selectionModel) { this.delegate = delegate; this.selectionModel = selectionModel; setLayout(new BorderLayout()); setOpaque(true); setBackground(new Color(207, 219, 234)); checkBox.setState(Boolean.TRUE); checkBox.setOpaque(true); checkBox.setBackground(new Color(207, 219, 234)); } public Component getTreeCellRendererComponent(JTree tree, Object value, boolean selected, boolean expanded, boolean leaf, int row, boolean hasFocus) { Component renderer = delegate.getTreeCellRendererComponent(tree, value, selected, expanded, leaf, row, hasFocus); TreePath path = tree.getPathForRow(row); if (path != null) { if (selectionModel.isPathSelected(path, true)) { checkBox.setState(Boolean.TRUE); } else { checkBox.setState(selectionModel.isPartiallySelected(path) ? null : Boolean.FALSE); } } renderer.setBackground(new Color(207, 219, 234)); tree.setOpaque(true); tree.setBackground(new Color(207, 219, 234)); this.setOpaque(true); this.setBackground(new Color(207, 219, 234)); add(checkBox, BorderLayout.WEST); add(renderer, BorderLayout.CENTER); return this; } }

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  • Problem at JUnit test with generics

    - by Tom Brito
    In my utility method: public static <T> T getField(Object obj, Class c, String fieldName) { try { Field field = c.getDeclaredField(fieldName); field.setAccessible(true); return (T) field.get(obj); } catch (Exception e) { e.printStackTrace(); fail(); return null; } } The line return (T) field.get(obj); gives the warning "Type safety: Unchecked cast from Object to T"; but I cannot perform instanceof check against type parameter T, so what am I suppose to do here?

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