java-programmer >>How do i do if-else condition in Struts ?

How do i do if-else condition in Struts ?

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  - Reset button cannot clear fields after displaying error messagesHello
    
    my form extends from ValidatorForm
    and making use of validator.xml and validator-rules.xml,
    
    The reset button can clear fields within form
    if the submit is not pressed.
    
    If I pressed the submit button and
    error messages display on the top of the form.
    And then now I click the reset button again,
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    Why is it so?
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    that is on a jpeg or bmp/gif/tiff ? is there any java package doing this?
    
    thanks
- 1
  - jtreetabledear java professional,
    
    i want to create a grid using jtreetable. i find the sample code in
    the java.sun.com. but it is trickly to understand for me. do you
    have any code
    (simple code) for using the jtreetable ? i want to simple jtreetable
    example program with sample data. do you have the code please send me
    to my mail id
    email***@***.com.
    
    i also search in the net. but i only very less no. sample code related
    to jtreetable. that code also so tricky. do you know any link that
    contains simple
    jtreetable program?
    
    with regards,
    balamurugan se
- 7
  - UTF 16 (byte[]) <--> String?Hi,
    
    is there a convenient way to convert unicode that's stored in byte array to
    java String?
    and vice-versa?
    
    e.g. for a single single unicode,
    the higher byte would be in byte[0],
    lower byte[1]
    and byte[2], byte[3] = 0. null terminated
    
    the byte array of unicode is generated from a C program and transfered over
    the network ..
    
    looking over the String API doesn't reveal much ... or am I overlooking
    something?
    
    Thanks in advance.
- 7
  - How to get current jar pathHi! I'm working on an application that should run on an usb pen using
    an embedded Derby DB. I need the DB to be on the USB pendrive with the
    application.
    Pen filesystem should look like this:
    
    /
    - application/
    - application.jar
    - lib/
    - embeddedDB
    
    using "user.dir" system property i get the path from where the jar has
    been launched, while I need the path where the jar is. How can I do?
- 7
  - package and jar filesHi,
    
    I am new to Java. I hope someone can give me a hint.
    
    What is the difference between package and jar files and do you use them ?
    
    thanks
    
    John
- 7
  - ToolTip for Graphical ItemsHello,
    
    I'm trying to make a tool tip pop up whenever the user does a
    mouse-over on a filled rectangle that I've drawn on the screen. I have
    no trouble creating the rectangle
    
    Rectangle test = new Rectangle();
    
    And it seems like there should be something like
    test.setToolTipText("rectangle"), but as far as I can tell, there's
    nothing like that. Is there some way to do this?
    
    Thanks,
    Ben
- 8
  - Just a Great Big Scrollable LineHello,
    I am a bit new to java and the java swing GUI.
    I am writing a JApplet.
    What I am trying to do is draw a line (say from (0, 0) to (1000, 1000)) and
    have the applet supply automatic scrollbars so that the user can see the
    whole line (sounds stupid - I know, but its a step in my direction).
    Anyway, I tried to inherit from a JLabel, change the inherited comopnent's
    paintComponent method to draw a line and put the inherited component in a
    JScrollPane. However, this only resulted in a Line which was only partially
    seen and no scrollbars. Moreover, I discovered that if I just add text to
    my label with the setText method then I get auto scrollbars if I make the
    applet smaller than the text size. This means that the setText method is
    doing something that defines it's boundaries for the JScrollPane to react
    to. So, my question is: How do I tell the JScrollPane that my inherited
    JLabel is 1000x1000 (and not just the size of the text)?
    Thanks,
    Aviv.
- 8
  - Ant Javadoc failure when building help.I'm getting this error when trying to compile javadoc in ant from my
    buildxml:
    Any ideas?
    
    C:\umg\java\web\dbtest\WEB-INF\src\build.xml:64: Javadoc failed:
    java.io.IOException: CreateProcess: javadoc.exe -d
    C:\umg\java\web\dbtest\WEB-INF\doc\api -classpath
    C:\umg\java\web\lib\servlet-api.jar;C:\umg\java\web\lib\struts.jar;C:\umg\ja
    va\lib\umg-db.jar -sourcepath
    C:\umg\java\web\dbtest\WEB-INF\src -version -author
    java.com.umusic.ecrm.web.test error=2
    
    what's error=2????
    
    this is in my build.xml:
    
    <target name="javadoc"
    description="Generate JavaDoc API docs">
    <delete dir="./doc"/>
    <mkdir dir="./doc"/>
    <javadoc sourcepath="./src"
    destdir="./doc/api"
    packagenames="*"
    author="true"
    private="true"
    useexternalfile="yes"
    version="true"
    windowtitle="${project.title} API Documentation"
    doctitle="<h1>${project.title} Documentation (Version
    ${project.version})</h1>"
    bottom="Copyright © 2003">
    <classpath refid="compile.classpath"/>
    </javadoc>
    </target>
- 8
  - My bean doesn't APPEAR on my JSP page!Hi, All!
    
    I have this simple bean (below), and i make the .class using JBuilder 7.0.
    
    I tryed to insert this bean into my JSP page:
    
    <%@ page contentType="text/html; charset=windows-1251" %>
    <html>
    <head>
    <title>
    Jsp1
    </title>
    </head>
    <jsp:useBean id="bean0" scope="session" class="bean1.KivaHanTester" />
    <jsp:setProperty name="bean0" property="*" />
    <body>
    <h1>
    JBuilder Generated JSP
    </h1>
    </body>
    </html>
    
    BUT I CAN't see this bean, when i open my JSP (IExplorer + Apache).
    May be i need to init this bean, like init() or show() i don't know.
    
    Thanks.
    
    SOURCE CODE:
    
    package bean1;
    
    import java.awt.*;
    
    public class KivaHan extends Canvas {
    
    private String msg;
    private int width, height;
    
    public KivaHan () {
    this ("Coffee: 10 lira");
    }
    public KivaHan (String s) {
    this (s, 200, 200);
    }
    public KivaHan (String s, int width, int height) {
    msg = s;
    this.width = width;
    this.height = height;
    setForeground (Color.cyan);
    setFont (new Font ("Serif", Font.ITALIC, 24));
    setSize (getPreferredSize());
    }
    public void paint (Graphics g) {
    Dimension d = getSize();
    FontMetrics fm = g.getFontMetrics();
    int len = fm.stringWidth (msg);
    int x = Math.max (((d.width - len) / 2), 0);
    int y = d.height / 2;
    g.drawString (msg, x, y);
    }
    
    public Dimension getPreferredSize () {
    return new Dimension (width, height);
    }
    }
    
    package bean1;
    
    public class KivaHanTester extends java.applet.Applet {
    public void init () {
    add (new KivaHan());
    }
    }
- 13
  - Simple question for those who understand recursion well. Please help.I have a tree represented as a linked list of simple objects
    (nodeId/parentId pairs) where the root node is the 1st element in the
    list. The other nodes are in somewhat random order. The parentId refers
    to the parent node.
    
    I want to convert it into a list where the values are in pre-order.
    I.e., I want to get this list as follows: ABCDEFGHIJ (see graph below).
    I.e., get the 1st node, put in in the list. If it has children, go
    through them one by one, get their child nodes, then put the parent in
    the list, then the leftmost first, and go from there. I.e., so that
    it's ordered in my linked list like this by (letters represent nodeId):
    
    A
    / \
    B J
    / | \
    C H I
    |
    D
    /|\
    E F G
    
    I created the following recursive method but it does not work
    correctly. For example, it places the nodes A then B and then J into
    the list first, rather than getting to J after adding all the child
    nodes. "isOnTheList" checkes whether the item is already in the list.
    "getImmediateChildren" returns the list of immediate child nodes
    ordered by nodeId
    
    Note: the empty list is passed to the method and is populated with the
    result:
    
    public static void orderTree(List list, List treeList) {
    if(treeList == null || treeList.size() == 0)
    return;
    
    Node child = null; List children = null;
    
    for(int i = 0; i < treeList.size(); i++) {
    node = (Node) treeList.get(i);
    // get list of children for this node
    children = getImmediateChildren(node, treeList);
    
    // if the node is not yet on the list, add it
    if(! isOnTheList(node, list) )
    list.add(cat);
    
    // if it has children, recurse to add all other nodes
    if(children.size() > 0) {
    orderTree(list, children);
    }
    }
    }
    
    Any idea what the problem is?
    
    Thanks.
- 13
  - Re:Correct use of exceptionsWhen we talk about exception, it means that in some situation which we think
    that it should works this way, but it isn't. For example, when we write
    something to connect to remote SMTP server, we assume that the remote server
    should be available but actually it is down... In this case, the exception
    happened... So we need the exception handling to show our error message to
    user and log the error.
    
    Hope this helps!
    
    Guoqi Zheng
    
    http://www.big8reader.com
- 13
  - struts form population from an object model...flangelli wrote:
    <snip>
    > I have a business object model with attributes throughout that are
    > mapped to different form beans. Every time that a form bean (jsp) is
    > returned to the user's browser, I need to have a place to access my
    > object model to retrieve the data from and populate the bean before it
    > is displayed. So far it seems that the only time an action class is
    > given "command" is AFTER the form submission, I need control on a page
    > by page basis to retrieve the values from the object model into the
    > bean so the jsp can render the beans values.....anyone had a problem
    > similar to this? Thanks in advance - Flangelli
    
    There's nothing which "requires" you to forward to a JSP; you could
    just as easily forward to an action. The hitch here is that the
    ActionForm will be populated according to the request parameters if
    you just perform a forward. The solution is simply to specify
    redirect="true" in the forwarding action so that the request
    parameters get lost.
    Just be careful in your validate method when using this mechanism:
    you're users will be irked if the first time they see a page it
    contains all manner of error messages. Since you often provide a
    reset button on a form, the smart way to approach the situation is
    to hold off generating errors if all form fields are blank (or
    have the default value).
    If this doesn't make perfect sense then repost and I'll dig up
    some sample code. Or contact me off-line.
- 14
  - Infinite loops in hashCode() and equals()What do you think the following fragment prints?:
    
    List l = new ArrayList();
    l.add(l);
    System.out.println(l.hashCode());
    
    Trick question. The result is an infinite recursion (i.e. a stack
    overflow), since the hash code for a List is calculated from the hash codes
    of its members.
    
    Likewise, the following causes an infinite recursion, since lists are
    defined to be equal when they have the same members.
    
    List l1 = new ArrayList();
    List l2 = new ArrayList();
    
    l1.add(l2);
    l2.add(l1);
    
    System.out.println(l1.equals(l2));
    
    These cases are simple to spot, but the same situation could occur with any
    cyclic graph of objects that compute hash code and/or equality based on the
    values of their members. Also, equals() and hashCode() are often called
    implicitly, for instance when adding an object to a HashSet or HashMap.
    
    I don't see any way this could be addressed other than by keeping track of
    which objects have already been processed by the current hashCode() or
    equals() call, and there's no way to do that without changing the method
    signatures, to, say, add a Set:
    
    in Object:
    
    public final int hashCode() {
    return hashCode(new HashSet());
    }
    
    public final int hashCode(Set processed)
    {
    if (processed.contains(this)) {
    return System.identityHashCode(this);
    }
    else {
    processed.add(this);
    return this.calculateHashCode(processed);
    }
    }
    
    public int calculateHashCode(processed) {
    return return System.identityHashCode(this);
    }
    
    with calculateHashCode(Set) being the method that classes can override and
    hashCode(Set) the method List et al. call on their members. And that is a
    pipe dream, since it isn't possible to make this sort of incompatible change
    at this late date.
- 16
  - batch update as a single transactionHi,
    
    I'm doing a JDBC batch update, writing several thousand rows to a single
    table. As I understand it a batch update can partially succeed, so some of
    my rows might get written and some not. I'd like the batch update to either
    fully succeed or completely fail, commit or rollback in other words. Is that
    easy to do? I'm pretty new at this.
    
    Thanks,
    John

Author

Message

Posted: 2006-3-6 2:13:00

Top

java-programmer, How do i do if-else condition in Struts ? How do i do if-else condition in Struts ?

logic:equal does not do it . how struts tag could be used in the JSP
page for an if-else condition ?

how to do it ?

Can anybody provide an example ?

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  - Forcing System.gc()I have an app that, at one point, really bogs down as so many objects are
    created and released in a lengthy process.
    
    I am wondering if I may not be able to improve performance by System.gc() in
    some "right" places in my code (wherever those might be!). It seems to me
    though, that the gc facilities in Java are so good, that this is something
    best left up to the JVM, and NOT mess with putting System.gc() in anyplace?
    
    I am on WinXP / Vista and JRE 1.6.x. TIA, R. Vince