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Caleb Myers
Caleb Myers

WebUtil Configuration and Jacob DLL Deployment for Oracle Forms



How to Solve the Problem of Unable to Write to Local File Jacob.dll




Jacob.dll is a Java library that allows Java applications to interact with COM objects, such as Microsoft Word or Excel. It is often used by Oracle Forms applications that use WebUtil to access client-side resources. However, sometimes users may encounter an error message like this:




unable to write to local file jacob.dll


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WUC-19: Unable to write to local file C:\Program Files (x86)\Java\jre6\bin\jacob.dll


This error means that the Java applet cannot download and write the jacob.dll file to the local file system. This can cause the applet to fail or behave unexpectedly. In this article, we will explain why this problem occurs and how to fix it.


Why Does This Problem Occur?




The problem of unable to write to local file jacob.dll can occur due to various reasons, such as:


  • The user does not have sufficient permissions to write to the default directory where jacob.dll is supposed to be stored (usually C:\Windows\System32 or C:\Program Files (x86)\Java\jre6\bin).



  • The jacob.dll file is already in use by another process and cannot be overwritten.



  • The jacob.dll file is corrupted or missing from the server where the applet is hosted.



  • The applet is not configured properly to download and load the jacob.dll file.



How to Fix It?




There are several possible solutions for this problem, depending on the root cause. Here are some common ones:


  • Create a dedicated directory where users have full permissions to write and read files, such as C:\WebUtil. Then, modify the webutil.cfg file on the server to point to this directory as the base directory for WebUtil files. For example:



webutil.archive=frmwebutil.jar,jacob.jar


webutil.base=C:/WebUtil


  • Make sure that the jacob.dll file is available on the server where the applet is hosted, and that it matches the version of the jacob.jar file that is used by the applet. You can download the latest version of Jacob from here.



  • Use Java Web Start (JWS) to deploy your applet instead of using a browser plug-in. JWS allows you to specify native libraries as part of your applet's resources, and automatically downloads and installs them on the client's machine. You can find more information on how to use JWS with Oracle Forms here.



By following these steps, you should be able to solve the problem of unable to write to local file jacob.dll and run your applet smoothly.


What Are the Benefits of Using Jacob.dll?




Jacob.dll is a useful tool for Java developers who want to leverage the power of COM objects in their applications. By using Jacob.dll, you can:


  • Access and manipulate any COM object that supports automation, such as Microsoft Office applications, Internet Explorer, Windows Media Player, etc.



  • Create and register your own COM objects in Java and expose them to other applications.



  • Use events and callbacks to communicate between Java and COM objects.



  • Support both 32-bit and 64-bit platforms with minimal changes.



Jacob.dll is also free and open source, so you can modify it to suit your needs or contribute to its development.


How to Troubleshoot Common Issues with Jacob.dll?




While Jacob.dll is a powerful and versatile library, it may also encounter some issues that can affect your applet's performance or functionality. Here are some common issues and how to troubleshoot them:


  • If you get an error message like "java.lang.UnsatisfiedLinkError: no jacob in java.library.path", it means that the Java Virtual Machine (JVM) cannot find the jacob.dll file in its library path. To fix this, you need to add the directory where jacob.dll is located to the java.library.path system property. For example, if jacob.dll is in C:\WebUtil, you can add this option to your applet's launch command: -Djava.library.path=C:\WebUtil



  • If you get an error message like "java.lang.NoClassDefFoundError: com/jacob/com/ComFailException", it means that the JVM cannot find the jacob.jar file in its classpath. To fix this, you need to add the jacob.jar file to your applet's classpath. For example, if jacob.jar is in C:\WebUtil, you can add this option to your applet's launch command: -cp C:\WebUtil\jacob.jar



  • If you get an error message like "com.jacob.com.ComFailException: Can't co-create object", it means that the JVM cannot create an instance of the COM object that you are trying to access. This can be caused by several reasons, such as:




  • The COM object is not registered on the client's machine. To fix this, you need to install or register the COM object on the client's machine.



  • The COM object is not compatible with the JVM's architecture. For example, if you are using a 64-bit JVM, you cannot access a 32-bit COM object. To fix this, you need to use a compatible JVM or COM object.



  • The COM object requires some initialization or configuration before it can be used. To fix this, you need to check the documentation of the COM object and perform any necessary steps before creating an instance of it.




By following these troubleshooting tips, you should be able to resolve most of the common issues with Jacob.dll and enjoy its benefits in your applet.


How to Use Jacob.dll in Your Java Applet?




Now that you know how to solve the problem of unable to write to local file jacob.dll, you may wonder how to use Jacob.dll in your Java applet. Here are some basic steps to follow:


  • Download the Jacob source code from here and extract it to a folder of your choice.



  • Compile the Jacob source code using a C++ compiler, such as Visual Studio or MinGW. You will get two files: jacob.dll and jacob.jar.



  • Copy the jacob.dll file to the directory where you want to store your WebUtil files, such as C:\WebUtil.



  • Copy the jacob.jar file to the directory where you store your applet's jar files, such as C:\Applet.



  • Edit the webutil.cfg file on the server to specify the webutil.base and webutil.archive parameters, as explained in the previous section.



  • Edit the formsweb.cfg file on the server to specify the archive and archive_jini parameters for your applet, as explained here.



  • Write your Java code to access and manipulate COM objects using Jacob. You can find some examples and documentation here.



  • Compile and deploy your applet using your preferred method, such as JWS or browser plug-in.



By following these steps, you should be able to use Jacob.dll in your Java applet and enjoy its features.


Conclusion




In this article, we have learned what is Jacob.dll, why it is used by Oracle Forms applications with WebUtil, how to solve the problem of unable to write to local file jacob.dll, how to troubleshoot common issues with Jacob.dll, and how to use Jacob.dll in your Java applet. We hope that this article has been helpful and informative for you. If you have any questions or feedback, please feel free to leave a comment below. 4e3182286b


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