java-programmer >>struts form population from an object model...

struts form population from an object model...

Index ‹ java-programmer

Previous
- 1
  - 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.
- 3
  - R: JTable and db connectionThere is a good example in JTable example ad www.sun.com. By the way, it is
    based on the idea of copying all the records in a Vector array, and then
    send all to the JTable...
    IMHO this isn't a good approach, but it is a good example to understand the
    JTable
    
    Bye
    
    Giuseppe
    
    Liguori Ferdinando <email***@***.com> wrote in message
    bhl1va$55u$email***@***.com...
    >
    > Could you help me to definy a trouble.
    > I wish see data retring db connection in a JTable.
    > Could you mailing an example.
    > Thanks.
    >
    >
- 4
  - I write Tic-Tac-Toe in JavaThis is the most sophisticated game known to mankind and I'm not sure
    if Java is good enough for it, but I'm trying anyway.
- 5
  - 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
- 5
  - 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
- 6
  - 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
- 6
  - 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>
- 6
  - 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
  - NoClassDefFound puzzleNoClassDefFound is my least favourite error message. This one has me
    stumped. I have been very sick the last few days and my brain in not
    yet fully engaged, so I hope it is something simple.
    
    I compile this fine, but when I run it, it says class
    com.mindprod.example.TestProgessFilter is not defined.
    The program seems too simple to have a NoClassDefFound problem.
    
    package com.mindprod.example;
    
    import java.io.BufferedReader;
    import java.io.File;
    import java.io.FileInputStream;
    import java.io.FilterInputStream;
    import java.io.IOException;
    import java.io.InputStream;
    import java.io.InputStreamReader;
    
    /**
    * @author Roedy Green, Canadian Mind Products
    * @version 1.0, 2007-08-03 Created with IntelliJ IDEA.
    */
    public class TestProgessFilter extends FilterInputStream {
    
    /**
    * tracks how many bytes we have read so far
    */
    long progress;
    
    // -------------------------- PUBLIC INSTANCE METHODS
    --------------------------
    /**
    * Constructor
    *
    * @param in input stream to progress monitor
    */
    public TestProgessFilter( InputStream in )
    {
    super( in );
    }
    
    /**
    * Reads the next byte of data from this input stream.
    */
    public int read() throws IOException
    {
    int ret = super.read();
    progress++;
    reportProgress();
    return ret;
    }
    
    /**
    * Reads up to byte.length bytes of data from this input stream
    into an
    * array of bytes.
    */
    public int read( byte[] b ) throws IOException
    {
    int ret = super.read( b );
    progress += b.length;
    reportProgress();
    return ret;
    }
    
    /**
    * Reads up to len bytes of data from this input stream into an
    array of
    * bytes.
    */
    public int read( byte[] b, int off, int len ) throws IOException
    {
    int ret = super.read( b, off, len );
    progress += len;
    reportProgress();
    return ret;
    }
    
    /**
    * Skips over and discards n bytes of data from this input stream.
    *
    */
    public long skip( long n ) throws IOException
    {
    long ret = super.skip( n );
    progress += n;
    reportProgress();
    return ret;
    }
    
    // -------------------------- OTHER METHODS
    --------------------------
    
    /**
    * report the progress to the user
    */
    private void reportProgress()
    {
    // this is a dummy routine. A real version would send an event
    // to a progress meter.
    System.out.println( progress );
    }
    
    // --------------------------- main() method
    ---------------------------
    /**
    * test driver
    *
    * @param args arg[0] is UTF-8 filename to read
    */
    public static void main( String args[] )
    {
    try
    {
    // O P E N
    FileInputStream fis = new FileInputStream( new File( args[
    0 ] ) );
    TestProgessFilter tpfis = new TestProgessFilter( fis );
    InputStreamReader eisr = new InputStreamReader( tpfis,
    "UTF-8" );
    BufferedReader br = new BufferedReader( eisr, 400/*
    buffsize */ );
    
    // R E A D
    while ( true )
    {
    if ( br.readLine() == null )
    {
    // line == null means EOF
    break;
    }
    }
    
    // C L O S E
    br.close();
    }
    catch ( Exception e )
    {
    System.err.println( e );
    e.printStackTrace( System.err );
    }
    }
    }
    --
    Roedy Green Canadian Mind Products
    The Java Glossary
    http://mindprod.com
- 10
  - portal library needed ?Hi all ,
    
    I am trying to build a portal which will consist of functions like log
    in , user management and some cms stuff and will probably develop more in
    the future. So I am trying to search for some portal building library. Has
    anyone try one of these portal library like jetspeed, jPorta, liferay ... ?
    Is it really that useful ? On what basis should I use one ? As i think the
    learning curve maybe quite large that I am sure i can build faster without
    it. But I am not sure if I would need it when I further develop the site.
    
    And can anyone share some pros and cons of the library.
    
    Thanks.
    
    Perseus
- 12
  - 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
  - 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
- 15
  - 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,
    fields cannot be cleared.
    
    Why is it so?
- 15
  - 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?
- 16
  - 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.

Author

Message

Sudsy

Posted: 2003-7-3 13:18:00

Top

java-programmer, 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.

Index ‹ java-programmer

Next
- 1
  - [Q] Saving imageI am looking for a solution to how to make a background image
    permanent in a Java application.
    
    My application can have a background image, but when it saves its
    file, the background image is not included in the saved file. Is there
    a convenient (or right) way to save a gif (or jpeg or png) image into
    an application file?
    
    Thanks in advance.
    
    Young-Jin
- 2
  - CeWolf and JSPHi, I'm Claudio, I'm a student and I want to use ceWolf for my graphs
    in JSP pages. I visited the web site http://cewolf.sourceforge.net/
    and i followed each pass of the tutorial but I don't visualize the
    chart, there is an exeption: NullPointerException in cewolf_jsp.java
    row 202:
    int _jspx_eval_cewolf_img_0 = _jspx_th_cewolf_img_0.doStartTag();
    
    In the JSP, if I delete this row:
    <cewolf:img chartid="line" renderer="cewolf" width="400"
    height="300"/>
    all go ok, but obviously there isn't the chart.
    
    Could you help me, please!
    Thanks, Claudio
- 3
  - Snake Sex 1827email***@***.com wrote:
    > I like to masterbate with my pet python, i hope you enjoy the pics i posted here of me having a wonerfull snakey time !
    >
    > http://superbabes.sexpartnerbd.com
    > cvgixlemtdskrblgjgfeitxfscjzhrcppyxghjowcxfo
    >
    
    leave it out! this is a java programming news group!
    
    try comp.lang.python
    
    W'ell just hang here having a wonderful erm.... "Classy" time! [groan]
- 4
  - Eclipse vs NetBeans vs Jbuilder under LinuxHello everyone,
    I've tried the above 3 IDEs in the last year and thought I might make some
    comments and ask for your thoughts. Just for interest sake and please don't
    start a Holy War ;-)
    
    I originally used netBeans for development, but switched over to Jbuilder
    because we where doing tomcat/struts development and my boss said it had
    better support. I didn't really get to use netBeans struts stuff but it did
    seem a bit weak in comparision.
    
    I would have thought Borland would have a great editor, but I find it very
    buggy in comparison to netBeans. Some of the things I have had problems
    with include the cursor not being moved when you click in the text area
    (this tends to screw up click and drag rearrangement of text or do it when
    you don't mean too), auto-formatting of code rearranging it until it won't
    compile, method parameter popups not always accessable, method parameter
    popups not able to show the names of parameters - only the type, and some
    others I can't remember right now.
    
    However, the struts support in JBuilder does seem to be better than netBeans
    and runs quite well. Over all the IDE also seems a little quicker and I
    quite like the way that you can have multiple projects open and flip
    between then with ease. netBeans doesn't seem to handle multiple projects
    as smoothly as JBuilder.
    
    I also tried Eclipse at home a couple of time in the last 6 months and at
    the moment I can't see why many people are using it. On both occasions I
    found also sorts of nasty bugs which tended to simple drive me nuts. The
    last time time I used it for example, I found that it would not run the
    code I had just edited. I.e. if I could load a project, made some changes
    and hit the run button, it would run the code without the changes included.
    In order to get the changes it, I had to explicitly do a save before each
    run. This sounds trivial but can get very annoying, both netBeans and
    JBuilder run the code you are editing, not the last saved code.
    
    Eclipse also seemed to have a strange concept of projects. It looked rather
    good with being able to see multiple project trees at the same time until
    it came to running them. Then it appeared to separate the concept of
    running a projects from the projects themselves and I had to effectively
    re-setup again. I also found that if I had en error in one project, it
    would fail the compile even if I was in another project. So whilst I could
    have multiple projects open at a single time, it seemed to have trouble
    understanding which projects I was in and what it was to compile. This
    resulted in me having to unload/reload projects on a regular basis. I also
    remember not being that happy with it's editor either, I can't remember
    exactly why right now.
    
    So, I would have to say that at the moment, I would tend to use netBeans for
    general development, JBuilder for struts and Eclipse not at all.
    
    --
    cio
    Derek
- 5
  - 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
- 6
  - 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 ?
- 7
  - 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
- 8
  - popupmenu for a cell in a JTableHello
    
    I want to have a popupmenu when I right click on a selected cell in a JTable
    (using with a AbtractTableModel). What are steps I should do, please help.
    
    Thank you
    S.Hoa
- 9
  - extract numbers from picture?is this called pattern matching or AI in java? how can you extract a number
    that is on a jpeg or bmp/gif/tiff ? is there any java package doing this?
    
    thanks
- 10
  - Java GSM encoding from micHi
    
    I'm trying to encode a microphone stream into GSM using
    org.tritonus.lowlevel.gsm.Encoder but I am receiving just static noise -
    I've checked the raw PCM output and it's fine. Is there anything obvious
    that's missing here?
    Thanks
    
    __________________________
    The mic is opened as:
    
    AudioInputStream ais=null;
    
    DataLine.Info info_mic = new DataLine.Info(TargetDataLine.class,
    new AudioFormat(AudioFormat.Encoding.PCM_SIGNED, 8000.0f, 16, 1, 2,
    8000.0f, false)
    );
    
    TargetDataLine mic = (TargetDataLine) AudioSystem.getLine(info_mic);
    mic.open();
    mic.start();
    
    ais = new AudioInputStream(mic);
    
    _____________________
    
    And the GSM frame encoder is:
    
    /*------*/
    byte [] gsmframe(AudioInputStream ais){
    
    byte [] encd = new byte[33];
    
    try{
    
    byte [] b = new byte[320];
    
    ais.read(b,0,b.length);
    
    DataInputStream di = new DataInputStream(new ByteArrayInputStream(b));
    
    short [] buf = new short[160];
    
    short j=0;
    
    for(int k=0; k<buf.length; k++){
    j=di.readShort();
    buf[k]=j;
    }
    
    org.tritonus.lowlevel.gsm.Encoder enc = new
    org.tritonus.lowlevel.gsm.Encoder();
    enc.encode(buf, encd);
    
    }catch(Exception e){
    System.out.println("error with microphone reading "+e);
    return null;
    }
    
    return encd;
    
    }
    /*-------*/
- 11
  - Communicating with a servlet using NIO?Is it possible for a client applet to communicate with a servlet using NIO?
    I know it's possible using standard IO but I would like to implement a
    servlet that accepts NIO connections from clients and interacts with them.
    Is this possible? I don't want to use a special port because of firewall
    considerations.
    
    --
    And loving it,
    
    -Q
    _________________________________________________
    email***@***.com
    (Replace the "SixFour" with numbers to email me)
- 12
  - Struts and AA based on a database
    Hello:)
    
    I have a question concerning authentification/authorization and
    elements visibility on a Web page in Struts. How to manage the
    visibility of control elements in a Struts-based application? The
    information about users should be stored in a database and not in XML
    configuration files. How to use role based or/and function based
    authorization system and how to retrieve the rights from a database and
    store them in the Principal object? The application is mantained within
    Tomcat application server. So, how to do this? Or, being more precise,
    is there any open-source library which provides such a functionality or
    should I develop everything from scratch? Do you have some examples for
    such stuff?
    
    best regards,
    Ania
- 13
  - Mp3 converter to WavHi,
    
    I just need to convert a mp3 file to the Wav format.
    Is there any free package existing, or do i have to write my own program ?
    In that case, do you know any link that could help me to understand how to
    do this ?
    
    Thanks !
- 14
  - 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());
    }
    }
- 15
  - Jars built with JDK 1.3 and JDK 1.4 interoperatingThe Runtime Environment is JRE 1.4. The latest code I have written has
    been compiled with JDK 1.4. However it depends on some packages written
    and compiled with JDK 1.3. Is there anything to look out for in this
    kind of setup or should I have to recompile the older code with 1.4? I
    have tested the whole thing and it works, but I wanted some more
    information. It is a swing code and I need the JProgressBar's
    indeterminate state which is available only in JDK 1.4.
    
    Any update is welcome. If there is any document explaining the above,
    that would be perfect. I searched but I was not able to find any
    reference.
    
    Thanks
    JS