Question on java

I have a Java program ( not mine) with import statements like the following:
import com.brainysoftware.tassie.ejb.Search;
import com.brainysoftware.tassie.ejb.SearchHome;
I want to know if Search here corresponds to "Search.class" and SearchHome corresponds to SearchHome.class" respectively. I was confused and for example, thought that Search and SearchHome were directories in the package tree.
Actually I also two other Java files ( actually EJBs) called SearchHome.java and Search.java and their corresponding class files in com.brainysoftware.tassie.ejb
So my question is: is Search in the import statement to be interpreted as Search.class..
I know my question is downright simple and silly. All help is appreciated
thanks in advance

actually, this would recursively import any
subpackages (or rather their classes), so
technically, you can (at least syntactically) import
a package this way!Uhm ... no, it wouldn't ... there is no such thing as a sub-package.
xxx.yyy and xxx.yyy.zzz have no special relationship whatsoever in Java. They are as related as xxx.yyy and xxx.zzz are ... the similarity in naming has no meaning in Java, it's there only to logically group APIs which belong together but you can't automatically import classes from all "sub-packages".
Ever tried to write "import java.*"? It doesn't do anything usefull.

Similar Messages

Question about Java's HttpServer: Threading? Backlog?

Hello,
I have two questions about Java's HttpServer (com.sun.net.httpserver). From the JavaDoc:
>
Management of threads can be done external to this object by providing a Executor object. If none is provided a default implementation is used.
>
How can I get information about the default implementation in 1.6.0_13? Do you know the behavior? From my observations, the default implementation uses no Threads, meaning every request is handled in the same Thread, this results in handling the requests to the HttpServer one after another.
Is this right?
The second question is about this, also from the JavaDoc:
>
When binding to an address and port number, the application can also specify an integer backlog parameter. This represents the maximum number of incoming TCP connections which the system will queue internally. [...]
>
When setting the backlog to -1, it uses the systems default backlog. How can I determine the systems default backlog? Can some lines of Java code reveal it (there is no getBeacklog() method)? Or is it up to the Operating System (we use Redhat Linux)?
Thanks a lot for your help!
Regards,
Timo

How can I determine the systems default backlog?You can't. There is no API for that even at the C level.
Can some lines of Java code reveal itNo.
Or is it up to the Operating System (we use Redhat Linux)?Yes. Linux provides a large default. It seems to be at least 50 on most platforms. This is not something you should be worrying about.

Three questions about Java and Ftp

Hello, i've the following questions about Java and Ftp:
1- .netrc file is in $HOME directory but i can't access to this directory from java code. The following line producesan Exception (directory doesn't exists)
FileWriter file = new FileWriter ("$HOME/.netrc");
2- .netrc file must have the following permissions: -rw- --- --- but when i create the .netrc file the following permissions are on default: -rw- r-- r--, how can i change this permissions? (In java code, i can't use chmod.....)
3- Are there any way to pass parameters to a .netrc file? If i get to do this i needn't change the permissions because i can't modify or create/destroy this file.
Thanks in advanced!!!
Kike

1- .netrc file is in $HOME directory but i can't
access to this directory from java code. The
following line producesan Exception (directory
doesn't exists)
FileWriter file = new FileWriter ("$HOME/.netrc");$HOME would have to be replaced by a shell, I don't
think you can use it as part of a legal path.
Instead, use System.getProperty("user.home");
Ok, thanks
2- .netrc file must have the followingpermissions:
-rw- --- --- but when i create the .netrc file the
following permissions are on default: -rw- r--r--,
how can i change this permissions? (In java code,i
can't use chmod.....)Yes, you can: Runtime.exec("chmod ...");
I need to use estrictly the .netrc with -rw- --- --- permissions
Yes, i can use Runtime.exec ("chmod ..."); but i don't like very much this solution because is a slow solution, am i right?
3- Are there any way to pass parameters to a.netrc
file? If i get to do this i needn't change the
permissions because i can't modify orcreate/destroy
this file.I don't think so. Why do you need the .netrc file in
Java at all? Writing a GUI frontend?I want to use automatic ftp in a java program and FTP server, the files and path are not always the same, so i can:
- modify .netrc (for me is the complex option)
- destroy and create a new .netrc (is easier but i have permissions problem)
- use .netrc with parameters but i haven't found any help about it
Thanks for your prompt reply!!!!
Kike

Simple question about JAVA path

Hi. I have a simple question , but I spent several hours trying to find an answer.
How do I know the location of the java executable which is used by Concurrent Manager.
I already know that running which java under application user will not give me the correct answer

Maybe you can try like this:
     public String getPath(){
          Class cls=getClass();
          String className=cls.getName();
          String packageName=cls.getPackage().getName();
          System.out.println(className);
          System.out.println(packageName);
          String newClassName=className.replaceAll("\\.", "/");
          String resouceName=newClassName+".class";
          System.out.println(resouceName);
          URL url;
          url=cls.getClassLoader().getResource(resouceName);
          String path="";
          path=url.getFile();
          return path;
     }

Efficiency Question: Simple Java DC vs Used WD Component

Hello guys,
The scenario is - I want to call a function that returns a FileInputStream object so I can process it on my WD view. I can think of two approaches - one is to simply write a simple Java DC that does so and just use it as a used DC so I can call the functionality from there. Or create another WD DC that exposes the value (as binary) via component interface.
I'm leaning on the simple Java DC approach - its easier to create. But I'm just curious on what would be the Pro-side (if there's any) if I use the WD Component interface approach? Is there a plus for the efficiency? (Though I doubt) Or is it just a 'best/recommended practice' approach?
Thanks!
Regards,
Jan

Hi Jan
>one is to simply write a simple Java DC that does so and just use it as a used DC so I can call the functionality from there
Implemented Java API for the purpose mentioned in your question is the right way, I think. The Java API can be even located in the same WebDynpro DC as your WebDynpro components. There is not strongly necessity to put it into separate Java DC.
>Or create another WD DC that exposes the value (as binary) via component interface
You should not do this because in general WD components' purpose is UI, not API. Implementing WD component without any UI, but with some component interface has very-very restricted use cases. Such WD component shall only be a choice in the cases when the API is WebDynpro based and if you have to strongly use WebDynpro Runtime API in order to implement your own API.
If your API does not require WebDynpro Runtime API invocations or anything else related to WebDynpro then your choice is simple Java API.
>But I'm just curious on what would be the Pro-side (if there's any) if I use the WD Component interface approach? Is there a plus for the efficiency?
No. Performance will be better in simple Java API then in WebDynpro component interface. The reason is the API will not pass thought heavy WebDynpro engine.
BR, Siarhei

Question About Java Threads and Blocking

I'm helping someone rehost a tool from the PC to the Sun. We're using the Netbeans IDE and the Java programming language. I took a Java course several years ago, but need some help with something now. We're developing a front-end GUI using Swing to allow users to select different options to perform their tasks. I have a general question that will apply to all cases where we run an external process from the GUI. We have a "CommandProcessor" class that will call an external process using the "ProcessBuilder" class. I'm including the snippet of code below where this happens. We pass in a string which is the command we want to run. We also instantiate a class called "StreamGobbler" my coworker got off the Internet for redirecting I/O to a message window. I'm also including the "StreamGobbler" class below for reference. Here's the "CommandProcessor" class:
// Test ProcessBuilder
public class CommandProcessor {
public static void Run(String[] cmd) throws Exception {
System.out.println("inside CommandProcessor.Run function...");
Process p = new ProcessBuilder(cmd).start();
StreamGobbler s1 = new StreamGobbler("stdin", p.getInputStream());
StreamGobbler s2 = new StreamGobbler("stderr", p.getErrorStream());
s1.start();
s2.start();
//p.waitFor();
System.out.println("Process Returned");
Here's the "StreamGobbler" class:
import java.lang.*;
import java.io.*;
// Attempt to make the output of the process go to the message window
// as it is produced rather that waiting for the process to finish
public class StreamGobbler implements Runnable {
String name;
InputStream is;
Thread thread;
public StreamGobbler (String name, InputStream is){
this.name = name;
this.is = is;
public void start(){
thread = new Thread (this);
thread.start();
public void run(){
try{
InputStreamReader isr = new InputStreamReader(is);
BufferedReader br = new BufferedReader(isr);
while (true){
String s = br.readLine();
if (s == null) break;
System.out.println(s);
//messageWindow.writeToMessageArea("[" + name + "]" + s);
is.close();
catch(Exception ex){
System.out.println("Problem reading stream" + name + "...:" + ex);
ex.printStackTrace();
The "CommandProcessor" class calls two (2) instances of the "StreamGobbler" class, one for "stdin" and one for "stderr". My coworker discovered these are the 2 I/O descriptors that are needed for the external command we're running in this case. We're actually called the Concurrent Versions System (cvs) command from the GUI. Here's what we need it to do:
We want to display the output real-time as the external process is executing, but we want to block any actions being performed on the GUI itself until the process finishes. In other words, we want to show the user any generated output from the process, but don't want to alllow them to perform any other actions on the GUI until this process has finished. If we use the "waitFor()" function associated with a process, it blocks all external process output until the process has completed and then spews all the output to the screen all at once. That's NOT what we want. Also, if we don't use the "waitFor()" function, the code just continues on as it should, but we don't know how to block any actions on the GUI until this process has finished. My coworker tried the following code, but it also blocked any output until the process had finished:
while (s1.thread.isAlive() || s2.thread.isAlive())
// We really don't do anything here
I'm pretty sure we have to use threads for the output, but how do we instantly show all output and block any GUI actions?
Thank you in advance for your help!

You're talking about a GUI, but there's nothing in that code which is putting events into the GUI update thread. You also say that nothing happens to the GUI until the CommandProcessor.Run() method returns if you wait for the process.
This implies that you're calling CommandProcessor.Run() in an ActionListener. This will block the GUI thread until it completes.
I was going to explain what to do, but a quick Google informed me that there's a new class which is designed to help in these situations SwingWorker (or as a [separate library|https://swingworker.dev.java.net/] if you're not up-to-date yet).

Questions about Java Servlets and JSP

Hi,
I'm a confident Java Programmer (and really enjoy using this language) but am very new to Java servlets and Java Server Pages.
I have previously worked with Perl on my web projects (simple 'league' style voting pages). I read in my 'Core Java' book that I should no longer use perl or even cgi.
I need to know more about Java servlets and Java Server Pages so I can make the switch to a 'real' programming language.
I have a few questions:
How should I start to learn JS and JSP?
How applicable will the java knowlegdge I have already be?
Are JSP common on the world wide web?
What tools do I need to start? (I currently develop in JBuilder and have Java 1.4.1 Standard Edition)
Is it likey my web host (and others) will support JSP?
Thank-you very much for helping a novice get started,
Regards,
Paul

Hi, Steve ...has to be frustrating! But do not despair.
Let's suppose the servlet it's named MyServlet on package org.servlets
WEB-INF should look:
WEB-INF
classes
org
servlets
MyServlet.class
web.xml
web.xml file should have this two declarations:
<web-app>
<servlet>
    <servlet-name>MyServlet</servlet-name>
    <servlet-class>org.servlets.MyServlet</servlet-class>
</servlet>

<servlet-mapping>
    <servlet-name>MyServlet</servlet-name>
    <url-pattern>/MyServlet</url-pattern>
</servlet-mapping>

</web-app>Now, once the container starts (Tomcat?), you should be able to see that servlet in:
http://localhost:8080/[my-context/]MyServletAnd what my-context is? The web application context. This string should be empty if your're deploying to the root context, otherwise should the context name. In Tomcat, deploying to root context defaults to using webapps/ROOT.
Sorry for my English, but I felt the need to answer your request. I hope it helps despite my writing.

Newbie question to java web services....

hi,
I used to be a .net programmer for a few years, and am have done web services in .net.... (using IIS, of course)
And i moved onto Java side recently - and am pretty new to tomcat / axis..etc..
I looked at the netbeans ide tutorial, and it covered on how to create a web services and a client using the IDE - with that is with the sun app server. Since I want to stick with Tomcat (which is a servlet container, i believe), the compilation complained that the HelloWSImpl.java is not a servlet, and will not let me run the web app. I have tried the WSDP 2.0 tutorial as well, but I first got the FastSetsource.jar not found? Then I got some other classes not found..etc... so, until now - i still am not able to create a web service, and a cliet to talk back and forth.
I have the following questions..
1. I am confused that how come tomcat itself is already a webserver, why would people use it on top of apache http server, which is another web server?
2. To create a web services, (I am thinking of the .net web services that i have done - that once you deploy it with IIS, and you browse to that service, if the function takes 2 parameter, there will be 2 textboxes waiting for you to put data to, then once you post - the xml response will come back...), does java allow front end interface automatically like that in .net? Or you have to code the JSP pages to include those textboxes yourself, and do a manual post to the web services address?
3. Are there any book out there, explains how to use tomcat for webservices? I have looked thru some of the java books that talks about web services, they mainly explain what webservices are, what is xml..etc... and of course, they did talk about the differenct type of messaging format available. (JAX-RPC..etc..)
4. In the java world - how do you use webservices? Is it the same way that i am familiar with? Like, that we have a front end gui, that it will call the web services, pass it a few param, and get the xml result back, and parse it and display / store.. it? Or that is not the correct way to consume the web services in java world?
5. In .net - as long as i have the .net framework sdk, and a IIS - i am good to go. In java - what do i need in order to deploy a web services?? I already have tomcat / jdk / wsdp / IDE - do i have enough to create a simple ws? if so, can you show me a basic tutorial??
based on some reading, i understand that the ws on the service side, needs an SEI implementing java.rmi.remote, and we need another class implementing this SEI. But I would really want to see more example, or downloads, where i can just download / view the whole thing all at once... I googled "java web service", "jax-rpc example"..etc.. most of the return links are from either java.sun.com, or ibm, or some other vendor's web site, explaining the architecture... I really want to look at the code, to get a better understand, what is the relationship between each of these softwares (tomcat, apache http server, axis...)
Any suggestions??
Thanks,
T

I think I can answer your Q1
Apache is very good at serving simple HTML pages
Tomcat is capable of serving active content
So the two complement each other
Or that's how I understand it.
Steaker

Newbie question on Java Persistence API - Entity Beans

Hi All,
I am basically new to Entities and the Java Persistence API. My question is, when using a container managed EntityManager, do I have to manually tidy-up any resources? Say for example, do I have to explicitly close the database connection (if ever I have that ability)? Invoke close() on EntityManager?
- Pat

You don't have to. That's what they mean by container managed. The container does it for you.
In fact you will get an IllegalStateException if you call close on a container-managed EntityManager.

Some questions about Java servlets

I am having some problems with my Java servlets. Here they are below.
#1 I have a login jsp page. When user logs in, the MySQL database is queried. If a match, redirect to appropriate page. The problem is I can't seem to remain in the login page if there is no match, I get a blank screen. If there is no match, how can I redirect it back to the login screen? For example, my login screen is login.jsp. Here is my code below.
while(rs.next())
if(rs != null)
String name = rs.getString("USERNAME");
Cookie getUser = new Cookie("User", name);
response.addCookie(getUser);
String sql2 = "INSERT INTO answers (USERNAME) VALUES( '" + name +"')";
ResultSet rs2 = stmt.executeQuery(sql2);
response.sendRedirect("profile410.jsp");
out.println("<p>inside if structure");
#2 After I go to the first screen after login, I am filling out a questionaire, and everytime I click on a submit button a different servlet comes into play, called InsertRecords.java. Everytime I go from one jsp to another, information gets stored into a database, InsertRecords.java is controlling this. I use the below code.
String delete = request.getParameter("delete");
String question = request.getParameter("question");
String value = request.getParameter("R");
if (delete.equals("no") && !value.equals(""))
String sql = "INSERT INTO answers (" + question + ") VALUES (" + value + ")";
int numRows = stmt.executeUpdate(sql);
out.println("Record has been inserted");
String nextPage = request.getParameter("nextPage");
Cookie[] cookies = request.getCookies();
if (cookies != null)
for (int i = 0; i < cookies.length; i++)
String name = cookies.getName();
String valuecook = cookies.getValue();
Cookie getUser = new Cookie(name, valuecook);
response.addCookie(getUser);
response.sendRedirect(nextPage);
the table is answer and the fields are ID, username, and q1, q2 q3, up to q11. the idea is upon login, the username gets stored into the answer table, the field username. I want the values stored in the same row everytime user jumps from one page to another based on his username. Goes to first jsp, q1 gets inserted, next jsp, q2 gets inserted, etc. But they all get inserted diagonally on different rows, not the same one, that is the problem. How can I fix this?
#2 Based on the above code, say there is 11 jsp pages, remember, this is an online questionaire. When user logs in, he starts at the first jsp page, or question. When for example when the browser gets cut off at question6, when he logs back in, I want him to start at question4, if cut of at question 11, start again upon login at question 8. The reason, so he won't have to start from the beginning. Each question is on seperate jsp's. The way I see this happening is creating a session upon login and keeping that session. And grab 4th question when he logs back in, but I am not sure about how to go about it.
Can someone help me please?

Q1:
Use the update command and not insert.
Q2:
Won't work. The user may log back in after the session has expired or from a different location. On log in look for a record for that user and what questions have been answered so far.

Question about Java Applet Jar file signing.

These questions pertain to Java 6 Standard Edition 1.6.0_22-b04 and later.
I have gone through the Oracle Java Tutorial for generate public and private key information
to sign a jar file, and how to sign the jar itself, all at
[http://java.sun.com/developer/onlineTraining/Programming/JDCBook/signed.html|http://java.sun.com/developer/onlineTraining/Programming/JDCBook/signed.html]
, and seek some clarification on the following related questions:
-In order to "escape" the java applet sandbox that exists around the client's
copy of the applet running in their web browser, ie.
(something forbidden by default), is verification of the signed applet enough, or is a policy file required
to stipulate these details?
-using the policytool policy file generator, what do I need to add under "Principals"
(if anything) when dealing with a Java applet? Are Codebase and SignedBy simply author information?
-If I choose to use a java.security.Permission subclass object set up in equivalent fashion within the Applet,
which class within the Applet jar do I instantiate that object in? Does it need to be mentioned
in the applet's jar Manifest.MF file?
-Is the "keystore database" a java language service/process which runs in
the Server's memory and is simply accessed and started by default
by the client verifier program (appletview/web browser)?
-The public key certificate file (*.cer) is put in the webserver directory holding
the Applet jar file (ie. Apache Tomcat, for example).
-Presumably, the web browser detects the signed jar
and certificate file, and provides the browser pop up menu asking the user
about a new, non recognised certificate (initially).
Is this so?
-With this being the case, can the applet now escape
the sandbox, be it with or without the stipulated
policy permissions?

848439 wrote:
-In order to "escape" the java applet sandbox that exists around the client's
copy of the applet running in their web browser, ie.
(something forbidden by default), is verification of the signed applet enough, or is a policy file required
to stipulate these details?Just sign the applet, the policy file is not necessary.
-Is the "keystore database" a java language service/process which runs in
the Server's memory and is simply accessed and started by default
by the client verifier program (appletview/web browser)?No.
-The public key certificate file (*.cer) is put in the webserver directory holding
the Applet jar file (ie. Apache Tomcat, for example).No. For a signed Jar, all the information is contained inside the Jar.
-Presumably, the web browser detects the signed jar
and certificate file, and provides the browser pop up menu asking the user
about a new, non recognised certificate (initially).
Is this so?No. It is the JVM that determines when to pop the confirmation dialog.
-With this being the case, can the applet now escape
the sandbox, ..Assuming the end-user OK's the trust prompt, yes.
..be it with or without the stipulated
policy permissions?Huh?

Question re: Java System vs. ABAP + Java System

Hello everyone,
I posted this message in the EP Implementation forum without realizing there is a dedicated WAS General forum; I apologize to those of you who might have read this already.
My question is;
Under what scenario would I want to install my Web Application Server as an ABAP + Java system?
We have been working with our development Portal server for a few months now with a high degree of success and the WAS Server it sits on is setup as a Java System only.
I understand that for Portals and using business packages in portal I only need Java WAS.
I guess I am only left with the question, when or why would I want to install the ABAP engine?
Would you use that for a different application that sits on WAS other than Portals?
Are there benefits in installing the ABAP engine that you do not have with a Java only system?
Thanks in advance for your help,
~Henry

Hi Henry,
Your ABAP stack in WAS server in nothing but your SAP R/3 System. In earlier versions only ABAP stack was available. But now SAP has combined both JAVA and ABAP stack into one. So, if anyone wants to work on both the things then they can you one single server only. No need to have different servers for that.
If your purpose solves with the only JAVA stack then you can continue with that. But, if you are going to install new server and you want to work on both ABAP as well as JAVA then better to install WAS 6.40 with ABAP+JAVA stack. So, single server will setisfy your whole requirement.
I hope you satistied with this answer.
Regards,
Bhavik

Question about Java MySQL connection

Hi guys, greetings to y'all, me name is Ryan, I'm new 'round here.
I have some questions, I have some application that I build with Java and using MSSQL Server 2000 as it's database, and now I want to try to use MySQL as it's database. I use MySQL server 5.0 and Navicat 8 for MySQL for the gateway and Win XP SP2 as my OS, what I want to know is, can you guys give me some connection string example for MySQL, for Java that is, I'm still learning in Java so sorry if I have some mistaken languages or code related words. Thanks a lot guys.
Best Regards.

Hi zahid, thanks for the reply, so if I have this code, like this one
try
                              Class.forName("sun.jdbc.odbc.JdbcOdbcDriver");
                              Connection con;
                              con=DriverManager.getConnection("jdbc:odbc:FlightSource","","");
                              stat2=con.prepareStatement("insert into Passenger_Table(vPassenger_Name,vPassenger_gender,iPassenger_Age,vPassenger_Destination,vPass_FlightClass,vPass_FlightType,vDate_of_Issue,vDate_of_Departure,vDate_Expire,vForm_Payment,Card_No,vTotal_Price)values(?,?,?,?,?,?,?,?,?,?,?,?)");
                              stat2.setString(1,textNama.getText());
                              stat2.setString(2,(String.valueOf(entry2)));
                              stat2.setString(3,textUmur.getText());
                              stat2.setString(4,textTujuan.getText());
                              stat2.setString(5,(String)comboKelas.getSelectedItem());
                              stat2.setString(6,(String)comboJenisKeberangkatan.getSelectedItem());
                              stat2.setString(7,(String)comboTglTiket.getSelectedItem()+"/"+texttgltiket1.getText()+"/"+texttgltiket2.getText());
                              stat2.setString(8,(String)comboTglBerangkat.getSelectedItem()+"/"+texttglberangkat1.getText()+"/"+texttglberangkat2.getText());
                              stat2.setString(9,(String)comboTglKadaluwarsa.getSelectedItem()+"/"+texttglkadaluwarsa1.getText()+"/"+texttglkadaluwarsa2.getText());
                              stat2.setString(10,(String)comboPayType.getSelectedItem());
                              stat2.setString(11,textCardNo.getText());
                              //stat2.setFloat(12,Float.parseFloat(textHarga.getText()));
                              stat2.setString(12,textHarga.getText());
                              stat2.executeUpdate();
                              JOptionPane.showMessageDialog(null, "The Data has successfully Booked " );
                         catch(Exception exception)
                              JOptionPane.showMessageDialog(null,"Error encountered while entering data in the database: "+exception);
                         }I just simply change the Class.forName{} line right ?
What About the database name, considering in the code above I used ODBC (the ODBC name is FlightSource), so the database was configured when I create the ODBC, then how about MySQL, should I create ODBC too to configured the database that I wanna use ?

Question about Java Makefile

Hello,
I was wondering how to write a Makefile that can create scripts (in bash) to launch programs? E.g. I have client.java and server.java, I know how to write a Makefile to compile them, but how can I use the Makefile to create a script to run them? Many thanks for any help.
Arjin

Hi,
It doesn't sound like you are asking a Java question even if you are using / having java classes. You probably get better and faster replies if you ask that in a mailing list or a forum that is related to make files.
Kaj
Ps. Most Java applications are built using Ant or Maven.

Question about java virtual machine

Hi,
Recently I met a strange conflict. I used Netbean to build a project and execute this project very well. However, when I opened a command window promt and tried to use the default command 'java' to execute my main class, the virtual machine reported a list of classload exceptions.
My question is : how could we execute a project built by a IDE such as Netbean using the default command 'java', or if we could use the default java compiler javac to build a project?
Thank you very much!
Best Regards,
Song

You should learn to use the javac/java command line tools. You're getting those errors because your classpath is wrong. The IDE might have additional library classes it uses and you need to explicitly include those when you compile and run your project outside the IDE.
So you would need to do for example:
java -cp .;lib/somelib.jar;lib/otherlib.jar com.mycompany.MyMainClass
Read up on classpath, if you ever want to become a serious programmer, you'll need to know what it does.

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