File IO operations using servlets

Hi,
I want to read and process some files (on the server) and write the results using Java servlets.
Is there any tutorial/resource for the beginners for doing this. I would be grateful for any assistance.
Thanx,
-bool

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Accessing files from a servlet

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Uploading a file to server using servlet (Without using Jakarta Commons)

Hi,
I was trying to upload a file to server using servlet, but i need to do that without the help of anyother API packages like Jakarta Commons Upload. If any class for retrieval is necessary, how can i write my own code to upload from client machine?.
From
Velu

<p>Why put such a restriction on the solution? Whats wrong about using that library?
The uploading bit is easy - you put a <input type="file"> component on the form, and set it to be method="post" and enctype="multipart/form-data"
Reading the input stream at the other end - thats harder - which is why they wrote a library for it. </p>
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Hi All,
I have some RTF Files, which contains some data.
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If you only need to display it, consider your HttpServletRequest just as byte stream. :) Just read from ServletInputStream and write it back into ServletOutputStream of HttpServletResponse.
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Can't write file on server using Servlet

Dear programers,
I have written a little method that creates a simple file. This method works fine when I execute it on my PC but it doesn't work when the servlet execute it.
For example:
public void test(){
FileOutputStream fileHTML = null;
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a) You do mean Servlet not Applet don't you? Applets aren't allowed access to the file system. If it's an applet open the "java console" window on the browser. You'll probably see a security exception.
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CRUD Operations using Servlets , SessionBeans and JPA

Hi
Please tell me what will be the right approach for doing CRUD operations .
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Please tell me the right approach here :
Option 1 :
JSP --->Servlet--->SessionBean--->JPA.
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Option 2 :
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Depends on the reusabiltity of the query really. If you have a single database query that is used in multiple places, then by all means put it in a session bean. But if you only do persist/delete operations, then just use the EntityManager directly. The session bean would just be an extra layer of complexity that you don't need.

How to display XML file in browser using Servlets?

Hi My XML file is like this:
<?xml version="1.0" encoding="UTF-8"?>
<ns0:purchase_order_MT xmlns:ns0="http://filetohttp.com">
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Using servlet to generate XML file

What I want to do is simple but can't work. Hope you guys can give me a hint.
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Emp e1= new Emp(); //Emp is the root of XML
I suspect the Emp constructor can't correctly find the globalDTD in its superclass -CGDocument. Please note this only happens in servlet setting, not is command line setting. Any suggestion to get arounf this?
Another unrelated question is that when I create a XML file using the Oracle XML parser, it seems all the elements a file has to be added once, otherwise the compiler will compalain about the missing element. this will be inconvinient when I constructing a big XML file, which I 'd liek to split into small piece and add them up. Maybe there is a good way but I just don't know it.
my email: [email protected]

Hi,
I'm running into the same problem deploying the classes generated by the class generator. Code works fine from JDeveloper, but had to put my DTD in the directory where my classes are. Deploying the classes with Apache's JServ gives me a NullPointer exception on the first addNode method. I guess it can't find the DTD. I tried to put the DTD in many locations but this didn't fix the problem. Any suggestions?
Steve,
Did you fix this problem? Thanx!
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Deploying a WAR file containing .jsp and servlets (also uses JNI)

Deploying a WAR file containing .jsp and servlets (also uses JNI) on Windows 2000
We had problems making it initially work on Sun ONE Web Server 6.0 Service Pack 1 because of lack of good iPlanet Web
Server documentation on deploying such files.
This is how we went about it:
1) Make one of the servlet and JSP (must call another Java Class) web application (.war) examples work with iPlanet Web
Server.
C:\iPlanet\Servers\plugins\servlets\examples\web-apps\HelloWorld\HelloWorld.war
and
C:\iPlanet\Servers\plugins\servlets\examples\web-apps\jakarta-examples\jarkarta-examples.war
a) Go to your Web Server Administration to deploy the application using GUI Web Application Deploy.
(We usually use command line, we experienced some issues with the GUI version, but maybe it is fixed in the new Web Server
service packs)
From browser, open http://yourserver:8888/
Click on Select a Server:Manage
Click on Virtual Server Class
Click on https-yourserver
Click on the Web Applications Tab
Then, click on Deploy Web Application
Enter the following -
WAR File On: Local
WAR File Path: C:\iPlanet\Servers\plugins\servlets\examples\web-apps\jakarta-examples\jarkarta-examples.war
Application URI: /jakarta
Installation Directory: c:\iPlanet\examples\jakarta-examples
By clicking on OK it deployed the application.
I can verify that it is deployed by selecting "Edit Web Applications" and I see the following entry:
Edit     /jakarta     c:/iPlanet/examples/jakarta-examples
Also, c:/iPlanet/examples/jakarta-examples should have the similar following directory structure ..
- [images]
- [jsp]
- index.html
- [servlets]
- [META-INF]
- [WEB-INF]
- [classes]
- [tlds]
- web.xml
- index.html
I restarted the server and accessed it using the following URL from my IE browser:
http://yourserver/jakarta/index.html
Then I clicked on the JSP Examples and tried some JSP examples.
b) Alternatively, you can also deploy the same example from the command-line.
Make sure C:\iPlanet\Servers\bin\https\httpadmin\bin\ is in your path
wdeploy deploy      -u /jakarta
          -i yourserver
          -v https-yourserver
          -d c:\iplanet\examples\jakarta-examples
          C:\iPlanet\Servers\plugins\servlets\examples\web-apps\jakarta-examples\jarkarta-examples.war
Restart the web server (I don't think you have to restart, but .. might as well).
2)Deploy your web-application
My Foo.war has the following structure.
You can use jar tf Foo.war to look at the file contents from command line (assuming you have JDK installed and the bin is
in your PATH)
Foo.war
- [META-INF]
- [WEB-INF]
- web.xml
- [classes]
- Bar.class
- MoServlet.class
- [lib]
- ThirdParty.jar
- [natlib]
- extlib.dll
- foo.jsp
Here is our application scenario:
foo.jsp uses a class call Bar (it is not in any package). The Bar java class uses classes from ThirdParty.jar. The
ThirdParty.jar in turn uses JNI to load library extlib.dll. foo.jsp also calls /servlet/Mo as well.
Now to deploy it, do the following:
(a) Make sure that within foo.jsp, you import the Bar class ( I don't know why you have to do it, but if you don't you get
JSP compile error).
<%@page language="java" import="Bar" contentType="text/html"%>
(b) Check web.xml (for Servlets)
Within web.xml, make sure you have the following mappings:
<servlet>
<servlet-name> MoLink </servlet-name>
<servlet-class> MoServlet </servlet-class>
</servlet>
<servlet-mapping>
<servlet-name> MoLink </servlet-name>
<url-pattern> /servlet/Mo </url-pattern>
</servlet-mapping>
(c) Deploy the application
Using command line:
wdeploy deploy      -u /foo
          -i yourserver
          -v https-yourserver
          -d c:\iplanet\examples\foo-dir
          Foo.war
(d) Change web-apps.xml file (for picking up ThirdParty.jar)
It is located in
C:\iPlanet\Servers\https-yourserver\config
You should see something similar to following after successful deployment.
<web-app uri="/foo" dir="C:\iPlanet\examples\foo-dir" enable="true"/>
Change it to look like following to pick up the ThirdParty.jar
<web-app uri="/foo" dir="C:\iPlanet\examples\foo-dir" enable="true">
<class-loader reload-interval="300"
          classpath="C:/iPlanet/examples/foo-dir/WEB-INF/lib/ThirdParty.jar"
          delegate="false"/>
</web-app>
(e) Change jvm12.conf file (for JNI)
It is located in
C:\iPlanet\Servers\https-yourserver\config
Add or uncomment the following lines:
#optional - just helps with instrumenting the jsp and servlet code
jvm.include.CLASSPATH=1
jvm.enableDebug=1
nes.jsp.enabledebug=1
jvm.trace=7
jvm.verboseMode=1
#required for JNI
java.compiler=NONE
jvm.classpath=.;C:\JDK1.3.1\lib\tools.jar;C:/iPlanet/Servers/plugins/servlets/examples/legacy/beans.10/SDKBeans10.jar;
jvm.option=-Xrs
jvm.option=-Xnoagent
# not sure if this is needed for iPlanet web server
jvm.option=-Djava.library.path=C:/iPlanet/examples/foo-dir/natlib/ -Djava.compiler=NONE
(f) Change magnus.conf file (for JNI)
We HAD to change this file in order for ThirdParty.jar file to pick up the native C++ code using JNI. Apparently, the
iPlanet Web Server doesn't pick the Environment Variable Path. Because when we had the directory containing the DLL just
in Path, it didn't work.
Change Extrapath directive:
ExtraPath C:/iPlanet/Servers/bin/https/bin;${NSES_JRE_RUNTIME_LIBPATH}
to
ExtraPath c:/iPlanet/examples/foo-dir/natlib;C:/iPlanet/Servers/bin/https/bin;${NSES_JRE_RUNTIME_LIBPATH}
(g) Apply changes from the Web Server Administration Console and Restart the web server.
You should be able to see the behaviour that you want from your application.
http://yourserver/foo/foo.jsp
Hope this was helpful!!!
Sonu

Deploying a WAR file containing .jsp and servlets (also uses JNI) on Windows 2000
We had problems making it initially work on Sun ONE Web Server 6.0 Service Pack 1 because of lack of good iPlanet Web
Server documentation on deploying such files.
This is how we went about it:
1) Make one of the servlet and JSP (must call another Java Class) web application (.war) examples work with iPlanet Web
Server.
C:\iPlanet\Servers\plugins\servlets\examples\web-apps\HelloWorld\HelloWorld.war
and
C:\iPlanet\Servers\plugins\servlets\examples\web-apps\jakarta-examples\jarkarta-examples.war
a) Go to your Web Server Administration to deploy the application using GUI Web Application Deploy.
(We usually use command line, we experienced some issues with the GUI version, but maybe it is fixed in the new Web Server
service packs)
From browser, open http://yourserver:8888/
Click on Select a Server:Manage
Click on Virtual Server Class
Click on https-yourserver
Click on the Web Applications Tab
Then, click on Deploy Web Application
Enter the following -
WAR File On: Local
WAR File Path: C:\iPlanet\Servers\plugins\servlets\examples\web-apps\jakarta-examples\jarkarta-examples.war
Application URI: /jakarta
Installation Directory: c:\iPlanet\examples\jakarta-examples
By clicking on OK it deployed the application.
I can verify that it is deployed by selecting "Edit Web Applications" and I see the following entry:
Edit     /jakarta     c:/iPlanet/examples/jakarta-examples
Also, c:/iPlanet/examples/jakarta-examples should have the similar following directory structure ..
- [images]
- [jsp]
- index.html
- [servlets]
- [META-INF]
- [WEB-INF]
- [classes]
- [tlds]
- web.xml
- index.html
I restarted the server and accessed it using the following URL from my IE browser:
http://yourserver/jakarta/index.html
Then I clicked on the JSP Examples and tried some JSP examples.
b) Alternatively, you can also deploy the same example from the command-line.
Make sure C:\iPlanet\Servers\bin\https\httpadmin\bin\ is in your path
wdeploy deploy      -u /jakarta
          -i yourserver
          -v https-yourserver
          -d c:\iplanet\examples\jakarta-examples
          C:\iPlanet\Servers\plugins\servlets\examples\web-apps\jakarta-examples\jarkarta-examples.war
Restart the web server (I don't think you have to restart, but .. might as well).
2)Deploy your web-application
My Foo.war has the following structure.
You can use jar tf Foo.war to look at the file contents from command line (assuming you have JDK installed and the bin is
in your PATH)
Foo.war
- [META-INF]
- [WEB-INF]
- web.xml
- [classes]
- Bar.class
- MoServlet.class
- [lib]
- ThirdParty.jar
- [natlib]
- extlib.dll
- foo.jsp
Here is our application scenario:
foo.jsp uses a class call Bar (it is not in any package). The Bar java class uses classes from ThirdParty.jar. The
ThirdParty.jar in turn uses JNI to load library extlib.dll. foo.jsp also calls /servlet/Mo as well.
Now to deploy it, do the following:
(a) Make sure that within foo.jsp, you import the Bar class ( I don't know why you have to do it, but if you don't you get
JSP compile error).
<%@page language="java" import="Bar" contentType="text/html"%>
(b) Check web.xml (for Servlets)
Within web.xml, make sure you have the following mappings:
<servlet>
<servlet-name> MoLink </servlet-name>
<servlet-class> MoServlet </servlet-class>
</servlet>
<servlet-mapping>
<servlet-name> MoLink </servlet-name>
<url-pattern> /servlet/Mo </url-pattern>
</servlet-mapping>
(c) Deploy the application
Using command line:
wdeploy deploy      -u /foo
          -i yourserver
          -v https-yourserver
          -d c:\iplanet\examples\foo-dir
          Foo.war
(d) Change web-apps.xml file (for picking up ThirdParty.jar)
It is located in
C:\iPlanet\Servers\https-yourserver\config
You should see something similar to following after successful deployment.
<web-app uri="/foo" dir="C:\iPlanet\examples\foo-dir" enable="true"/>
Change it to look like following to pick up the ThirdParty.jar
<web-app uri="/foo" dir="C:\iPlanet\examples\foo-dir" enable="true">
<class-loader reload-interval="300"
          classpath="C:/iPlanet/examples/foo-dir/WEB-INF/lib/ThirdParty.jar"
          delegate="false"/>
</web-app>
(e) Change jvm12.conf file (for JNI)
It is located in
C:\iPlanet\Servers\https-yourserver\config
Add or uncomment the following lines:
#optional - just helps with instrumenting the jsp and servlet code
jvm.include.CLASSPATH=1
jvm.enableDebug=1
nes.jsp.enabledebug=1
jvm.trace=7
jvm.verboseMode=1
#required for JNI
java.compiler=NONE
jvm.classpath=.;C:\JDK1.3.1\lib\tools.jar;C:/iPlanet/Servers/plugins/servlets/examples/legacy/beans.10/SDKBeans10.jar;
jvm.option=-Xrs
jvm.option=-Xnoagent
# not sure if this is needed for iPlanet web server
jvm.option=-Djava.library.path=C:/iPlanet/examples/foo-dir/natlib/ -Djava.compiler=NONE
(f) Change magnus.conf file (for JNI)
We HAD to change this file in order for ThirdParty.jar file to pick up the native C++ code using JNI. Apparently, the
iPlanet Web Server doesn't pick the Environment Variable Path. Because when we had the directory containing the DLL just
in Path, it didn't work.
Change Extrapath directive:
ExtraPath C:/iPlanet/Servers/bin/https/bin;${NSES_JRE_RUNTIME_LIBPATH}
to
ExtraPath c:/iPlanet/examples/foo-dir/natlib;C:/iPlanet/Servers/bin/https/bin;${NSES_JRE_RUNTIME_LIBPATH}
(g) Apply changes from the Web Server Administration Console and Restart the web server.
You should be able to see the behaviour that you want from your application.
http://yourserver/foo/foo.jsp
Hope this was helpful!!!
Sonu

Cache file(pdf) in user's browser using Servlet -Cookie, or Session

How can I save a file (pdf) in the cache of a browser (IE 6) in a user's computer? I am using Servlet and Tomcat 4.1.24. PDF file is sitting in server (remote computer) under a URL space.
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Thanks,
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[email protected]

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Also, how would I create a file, given a URL to that file.
URL fileInServer = new URL("http://www.myDomain.com/myWebApp/PDF/my.pdf");
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u don't need j2ee and struts to do file uploading. An example is as such
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class FileUploadObj {
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Hi all,
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please suggest me a way.
thanks in advance.
ram.

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