Corporate Info | News | Solutions | Products | Partners | Services | Events | Download | How To Buy

# Using WebLogic File Services I. Introduction Overview of WebLogic File Services II. The WebLogic File API WebLogic File API reference WebLogic File objects and their classes Setting up the WebLogic Server to read and write files Manufacturing T3File-related objects T3FileSystems and T3Files The T3FileInputStream class The T3FileOutputStream class III. Implementing with WebLogic File Import packages Obtain a remote T3Services interface Create a T3FileSystem and a T3File Create and use an OutputStream object Create and use an InputStream object Full code example IV. Change history Other related documents Installing WebLogic (non-Windows) Installing WebLogic (Windows) Writing a WebLogic client application Developers Guides API Reference Manual # Overview of WebLogic File Services WebLogic File provides high-speed client-side access to native operating system files on the server. The client API extends the lowest-common-denominator capabilities of Java (java.io.InputStream and java.io.OutputStream), which allows it to be used seamlessly in existing code, with additional services that are specific to manipulating remote files. As a service, WebLogic File also has access to all of the other WebLogic facilities, like logging, instrumentation, and workspaces. All WebLogic component-based services, including File services, are integrated into the WebLogic framework and can share access and resources. Their APIs share many common aspects that make building a complex networked application easier. Your application may use a variety of these services, all of which can share access to objects and client resources. With WebLogic File, as with other WebLogic services, the client uses factory methods to generate T3FileInputStream and T3FileOutputStream objects. These classes extend the standard Java InputStream and OutputStream classes, allowing them to be plugged into existing client code. They also provide additional methods that are specific to remote file streams. WebLogic File enhances read and write performance over a network by transmitting data in buffers whose size is independent of the size of the requests, and by using readAhead and writeBehind buffering. The implementation increases the rate of data transfer in several ways. Data is transmitted in buffers whose size is independent of the size of application requests. An application can make many small requests without adversely affecting performance. The client does read ahead; that is, it automatically requests buffers ahead of the application. While an application is processing a buffer of data, the next buffer is being simultaneously retrieved. The client does write behind; that is, it allows the application to write buffers beyond what has been flushed to the disk on the server. While an application is preparing a buffer of data, the previous buffers are being simultaneously written to the disk. A flush operation blocks on the client until an acknowledgment has been received that all outstanding buffers have been flushed. An application may specify the transfer buffer size, the number of buffers of read ahead, and the number of buffers of write behind, or it may rely on default values. The default buffer size is 100K, and the default number of buffers for both read ahead and write behind is 1. The defaults set by WebLogic File are usually the best choice for maximum speed. If you decide not to use the defaults, here are some hints for choosing other values. Setting the buffer size. In general, the larger the transfer buffer size, the greater the raw speed of the transfer. The difference can be significant; using a 1K buffer might be almost an order of magnitude slower than a 100K buffer. However, larger buffers require more memory on the client side, so you need to determine the most effective settings for your configuration. Setting readAhead and writeBehind buffers. The best value for readAhead and writeBehind depends on the rate at which your application processes buffers relative to the transfer speed. With a consistently slower application, a single buffer of readAhead and writeBehind will provide the maximum benefit. A consistently faster application will not benefit at all from increasing readAhead and writeBehind. Thus, the default value of 1 works well in most cases. However, if your application varies the rate at which it processes buffers, you may want to increase readAhead and writeBehind so that the application can always work at its maximum speed. This document covers information specific to using the WebLogic File API. You should also read the Developers Guide that covers all the services and facilities within WebLogic, Writing a WebLogic client application. If this is your first experience working with InputStream and OutputStream in Java, you may also want to read the information available in the Java tutorial at Sun. # WebLogic File API reference Package weblogic.io.common
    Class java.lang.Object
       Interface weblogic.io.common.IOServicesDef
       Class java.io.InputStream
          Class weblogic.io.common.T3FileInputStream
       Class java.io.OutputStream
          Class weblogic.io.common.T3FileOutputStream
       Interface weblogic.io.common.T3File
       Interface weblogic.io.common.T3FileSystem
       Class java.lang.Throwable
         (implements java.io.Serializable)
          Class java.lang.Exception
             Class weblogic.common.T3Exception
# WebLogic File objects and their classes weblogic.io.common.T3File weblogic.io.common.T3FileSystem The interfaces T3File and T3FileSystem define T3Files and T3FileSystems. T3Files, which may represent local (usually client-side) or remote (usually server-side) files, are produced by T3FileSystems, which may also represent local or remote files. T3Files and T3FileSystems make it easy to write code that treats local and remote files uniformly. Objects from these interfaces, like all service-related objects in the WebLogic framework, are allocated by requests to an object factory. This gives the developer a fine level of control over resources. weblogic.io.common.T3FileOutputStream weblogic.io.common.T3FileInputStream Two classes from the weblogic.io.common package -- T3FileInputStream and T3FileOutputStream -- provide server-side read and write access to files. weblogic.io.common.IOServicesDef weblogic.common.T3ServicesDef With its class variable "services," a WebLogic client accesses the WebLogic Server's services through methods in the weblogic.common.T3ServicesDef. WebLogic Files and WebLogic File Systems are accessed through the method, T3ServicesDef.io(), which returns a weblogic.io.common.IOServicesDef object. The IOServicesDef interface has methods for requesting a T3FileSystem from the IOServices object factory. From a client, you supply the name of the fileSystem as an argument to IOServicesDef.getFileSystem() and are returned a T3FileSystem object. From a server-side object, call IOServicesDef.getFileSystem() with an empty string or null. This will return a pointer to the file system relative to the working directory of the server. The T3FileSystem interface has methods for requesting a T3File from the IOServicesDef object factory, and the T3File interface has methods for requesting a T3FileInput/OutputStream for reading or writing to the file. The following code shows how a client obtains a T3FileSystem remote interface, a T3File, and an OutputStream for writing to the file:
      T3ServicesDef t3services;
      Hashtable env = new Hashtable();
      env.put(Context.PROVIDER_URL, "t3://localhost:7001");
      env.put(Context.INITIAL_CONTEXT_FACTORY,
              weblogic.jndi.WLInitialContextFactory.class.getName());
      Context ctx = new InitialContext(env);
      t3services = (T3ServicesDef) ctx.lookup("weblogic.common.T3Services");
      ctx.close();
      T3FileSystem myFS = t3services.io().getFileSystem("usr");
      T3File myFile = myFS.getFile("myDirectory/myFilename");
      T3FileOutputStream t3os = myFile.getFileOutputStream();
      t3os.write(b);
You will need to wrap the code in a try / catch block to handle possible exceptions. This is not shown here for simplicity. The recommended method of getting a T3FileInputStream or T3FileOutputStream for a T3File is to invoke T3File.getFileInputStream() or T3File.getFileOutputStream() directly on a T3File object. T3FileInputStream and T3FileOutputStream objects both extend standard java.io.* classes. ### Setting up the WebLogic Server to read and write files Before you can use WebLogic File services, you must first establish one or more path prefixes -- a fileSystem -- for use by clients by setting a property in the weblogic.properties file. For example, to map the file system name "users" to the path on the server host "/usr/local/tmp" add the following line to your weblogic.properties file:
      weblogic.io.fileSystem.users=/usr/local/tmp
When you request a T3FileSystem from the IOServicesDef factory -- eventually to be used to creating a T3File and reading/writing to it with an input or output stream -- you use the registered fileSystem name as an argument for the getFileSystem() method. The T3FileSystem object that is returned is mapped to the fileSystem registered in the properties file. For security reasons, a WebLogic client cannot access files higher in the directory than the lowest directory registered as part of a file system name. Filenames cannot contain ".." or an Exception will be thrown. For example, an attempt to read or write "/users/../filename" will throw an Exception. Note: When you are setting properties in the properties file on a Windows NT system, you cannot use single backslashes (\) because they will be interpreted as escape characters. Using single backslashes when setting a property result in an error message similar to this:
      java.io.FileNotFoundException: Remote file name <filename> malformed
You can either use double backslashes, as in this example:
      weblogic.io.volume.vol=c:\\remote\\temp
or use forward slashes instead, which will be properly mapped to a Window-style syntax by the parser:
      weblogic.io.volume.vol=c:/remote/temp
### Manufacturing T3File-related objects In these examples, we show how to obtain request the input and output streams necessary to read and write to a remote T3File. We obtain the remote T3File object from a T3FileSystem interface. Here, "users" is the name of a fileSystem that is registered in the weblogic.properties file. It maps to the absolute path /usr/local/users on the WebLogic Server host.
      T3ServicesDef t3services = getT3Services("t3://localhost:7001");
      // Get a T3FileSystem object from the IOServicesDef factory
      // Give a registered fileSystem as an arg
      T3FileSystem myFS = t3services.io().getFileSystem("users");
      // Get a T3File from the T3FileSystem
      T3File myFile = myFS.getFile("ben/notes");
      // Get an OutputStream to write to the file
      T3FileOutputStream t3os = myFile.getFileOutputStream();
      // Write a byte "b" to the OutputStream
      t3os.write(b);
This code creates and writes a byte to a file that maps to the Server host path "/usr/local/users/ben/notes". The method getT3Services() is listed under the section Accessing WebLogic services via JNDI in the Developers Guide, "Writing a WebLogic client application". You can add this method to your client. This brief example illustrates the most common usage. There are other way to request particular T3File-related objects from the IOServicesDef factory, through a set of "convenience" methods that allow you to directly request a T3FileInputStream or T3FileOutputStream without first creating a T3FileSystem or T3File object. Here are examples of using the "convenience" methods provided by the IOServicesDef factory. You can request a T3FileInputStream or T3FileOutputStream object directly from the IOServicesDef factory by calling the getFileInput/OutputStream() method, with a pathname argument that follows this pattern:
    "/registeredFileSystem/fileName"
where the registeredFileSystem is a mount-point registered in the weblogic.properties file as the property "weblogic.io.filesystem.registeredFileSystem=actualPath; and the fileName is the name of the destination file. When you request a T3FileInputStream or T3FileOutputStream object directly, without getting one from methods called on a T3FileSystem, you must include the leading slash in the fileSystem name or the server will generate this type of error:
      java.io.FileNotFoundException: Remote file name <filename> is relative
Here is an example. This T3FileInputStream object uses the defaults for buffer size and readAhead. If you choose not to use the default settings for buffer size and readAhead/writeBehind, you can set these values by using different factory methods that allow you to specify these values. In this example, an InputStream object is created with a buffer size of 1024 bytes and 3 readAhead buffers:
      int bufferSize = 1024;
      int readAhead = 3;

      T3ServicesDef t3services = getT3Services("t3://localhost:7001");
      InputStream is =
        t3services.io().getFileInputStream("/users/myfile",
                                           bufferSize,
                                           readAhead);
In this example, the OutputStream object is created with a buffer of 1024 bytes and 2 writeBehind buffers. The method getT3Services() is listed under the section Accessing WebLogic services via JNDI in the Developers Guide, "Writing a WebLogic client application".
      int bufferSize = 1024;
      int writeBehind = 2;

      T3ServicesDef t3services = getT3Services("t3://localhost:7001");
      Outputstream os =
        t3services.io().getFileOutputStream("/users/myfile",
                                            bufferSize,
                                            writeBehind);
Error handling. When an error occurs, the factory methods throw the exception weblogic.common.T3Exception, which contains the cause of the problem as a nested exception. ### T3FileSystems and T3Files weblogic.io.common.T3FileSystem A T3FileSystem is made up of T3Files. You create and manage a T3File by manufacturing a T3FileInput/OutputStream that is used to read and write the file. A T3FileSystem may represent the local file system on a client, or a remote file system on a WebLogic Server. This makes it easy to write code that treats both local and remote file systems uniformly. You request a T3FileSystem from the IOServicesDef factory with the getFileSystem() method. From a client, you supply the name of the fileSystem as an argument to IOServicesDef.getFileSystem() and are returned a T3FileSystem object. From a server-side object, call IOServicesDef.getFileSystem() with an empty string or null. This will return a pointer to the file system relative to the working directory of the server. The T3FileSystem interface also has other methods that return the file-system-dependent file separator string, and the file-system-dependent path separator string. This interface also contains more "convenience" methods that allow direct access to file Input/OutputStreams without creating an intermediary T3File object. weblogic.io.common.T3File You request a T3File by calling one of the T3FileSystem.getFile() methods. Like a T3FileSystem, a T3File can represent either local or remote files. In addition to methods for getting Input/OutputStreams to read and write to the file, this interface also has accessory methods to get the file name and path associated with the T3File object, to get its parent directory, to check if the file exists and is a "normal" T3file, to test if you can read and write to the file, to get its length and last modified date, to rename it, to make a directory, and other file-related tasks. ### The T3FileInputStream class weblogic.io.common.T3FileInputStream You customarily create a T3FileInputStream by calling the T3File.getFileInputStream() method, which returns an object of the class T3FileInputStream. This class extends the standard java.io.InputStream class and provides two additional methods:
       public int bufferSize();
which returns the current buffer size and
       public int readAhead();
which returns the current number of buffers of read ahead. The implementation of two other methods in T3FileInputStream that override methods in java.io.InputStream are of interest: The method available() returns the number of bytes of unread data that have been buffered on the client. It is never greater than the buffer size times one plus the number of buffers of read ahead. The method skip() starts out by discarding data that has been requested through read ahead and eventually issues a request to the server to skip any remaining data. Currently, T3FileInputStream does not support the methods java.io.InputStream.mark() and java.io.InputStream.reset(). ### The T3FileOutputStream class weblogic.io.common.T3FileOutputStream You customarily create a T3FileOutputStream by calling the T3File.getFileOutputStream() method, which returns an object of class T3FileOutputStream. This class extends the standard java.io.OutputStream class and provides two additional methods:
       public int bufferSize();
which returns the current buffer size and
       public int writeBehind();
which returns the current number of buffers of write behind. The implementation of two other methods in T3FileOutputStream that override methods in java.io.OutputStream are of interest: The method flush() blocks on the client until an acknowledgment has been received that all outstanding buffers have been flushed to the server. The method close() method does an automatic flush(). If an error occurs on the server while a file is being written, the client is asynchronously notified and all subsequent operations -- write(), flush(), or close() -- will generate a java.io.IOException. # Implementing with WebLogic File Services Here are step-by-step instructions on how to request and use T3File-related objects in your application. Step 1. Import packages Step 2. Obtain a remote T3Services Step 3. Create a T3FileSystem and a T3File Step 4. Create and use an OutputStream object Step 5. Create and use an InputStream object Full code example ### Step 1. Import packages In addition to other packages you import for your program, WebLogic File applications import the following:
    import java.io.*;
    import weblogic.common.*;
    import weblogic.io.common.*;
### Step 2. Obtain a remote T3Services interface From a WebLogic client application, you access the T3File services via the T3ServicesDef remote factory interface that lives on the WebLogic Server. Your client obtains a remote stub to the T3Services object via a JNDI look-up. We define and list a method called getT3Services() that you can add to you client to access the T3Services stub. It is listed under the section Accessing WebLogic services via JNDI in the Developers Guide, "Writing a WebLogic client application". You can simply call the method giving the URL of the WebLogic Server as an argument like so:
     T3ServicesDef t3services = getT3Services("t3://weblogicurl:7001")
### Step 3. Create a T3FileSystem and a T3File In general, the way to begin working with reading and writing files is to get a T3FileSystem object, and from it to request a T3File from or to which you will read or write. Use the T3ServicesDef remote interface to access the IOServices factory. Call the IOServices factory method getFileSystem() to get a T3FileSystem object. Supply the name of a file system that is registered on the WebLogic Server as an argument. You register a file system in the weblogic.properties file with the property:
      weblogic.io.fileSystem.name=path
For this example, we assume the following file system property is set up:
      weblogic.io.fileSystem.myFS=/usr/local
T3Files created in the T3FileSystem mapped to "myFS" will be physically located in the directory "/usr/local" on the WebLogic Server's host. Here is the code to get the T3FileSystem and a T3File named "test":
      T3FileSystem t3fs =
        t3services.io().getFileSystem("myFS");
        T3File myFile = t3fs.getFile("test");
We can also check to see if the file exists before we read from or write to it, as shown here:
      if (myFile.exists()) {
        System.out.println("The file already exists");
      }
      else {
        // Create a file with an array of bytes. We'll write it
        // to an output stream in the next step
        byte b[] = new byte[11];
        b[0]='H'; b[1]='e'; b[2]='l'; b[3]='l'; b[4]='o'; b[5]=' ';
        b[6]='W'; b[7]='o'; b[8]='r'; b[9]='l'; b[10]='d';
      }
### Step 4. Create and use an OutputStream object We have assembled an array of bytes that we'd like to write to a T3File on the WebLogic Server. You customarily create a T3File, and then request an OutputStream to write to it, using the T3File.getOutputStream() method. Using the T3File "myFile" that we created in the previous step, this example illustrates this process:
      Outputstream os =
         myFile.getFileOutputStream();
         os.write(b);
         os.close();
Always close the OutputStream object when work with it is completed. ### Step 5. Create and use an InputStream object Now we have got a T3File that we'd like to read from and confirm its contents. You request and use an InputStream object with the same patterns you use for an OutputStream object. Here we request an InputStream object with which we can read from the T3File "myFile." This opens an InputStream to the T3File. In this example, we're reading bytes; first, we allocate an array of bytes to read into (from which we will later create a String that we can display); then we use the standard methods of the java.io.InputStream class to read from the T3File, as shown here:
      byte b[] = new byte[11];
      InputStream is = myFile.getFileInputStream();
      is.read(b);
      is.close();
Now let's create a String for display to confirm the results:
      String result = new String(b);
      System.out.println("Read from file " + T3File.getName()
                         " on the WebLogic Server:");
      System.out.println(result);
      is.close();
Always close the InputStream object when work with it is completed. ### Full code example The full code example is a runnable example that we ship in the examples/io directory in the distribution. You can compile and run the example using the instructions located in the same directory. The example uses a main() method so that you can run the example from the command line.
    public class HelloWorld {

      public static void main(String[] argv) {

        // Strings for the WebLogic Server URL, the T3FileSystem
        // name, and the T3File name
        String url;
        String fileSystemName;
        String fileName;

        // Check the user's input, and then use it if correct
        if (argv.length == 2) {
          url = argv[0];
          // Use the local file system on the client
          fileSystemName = "";
          fileName = argv[1];
        }
        else if (argv.length == 3) {
          url = argv[0];
          fileSystemName = argv[1];
          fileName = argv[2];
        }
        else {
          System.out.println("Usage:   java example.io.HelloWorld " +
                             "WebLogicURL fileSystemName fileName");
          System.out.println("Example: java example.io.HelloWorld " +
                             "t3://localhost:7001 users test");
          return;
        }

        // Obtain remote T3Services factory from WebLogic Server
        try {
          T3Services t3services = getT3Services(url);

          // Get the file system and the file
          System.out.println("Getting the file system " + fileSystemName);
          T3FileSystem fileSystem =
            t3services.io().getFileSystem(fileSystemName);
          System.out.println("Getting the file " + fileName);
          T3File file = fileSystem.getFile(fileName);

          if (file.exists()) {
    	// The file exists. Don't do anything
    	System.out.println("The file already exists");
          }
          else {
    	// The file does not exist. Create it.
    	byte b[] = new byte[11];
    	b[0]='H'; b[1]='e'; b[2]='l'; b[3]='l'; b[4]='o'; b[5]=' ';
    	b[6]='W'; b[7]='o'; b[8]='r'; b[9]='l'; b[10]='d';

    	// Get an OutputStream and write to the file
    	System.out.println("Writing to the file");
    	OutputStream os = file.getFileOutputStream();
    	os.write(b);
    	os.close();
          }

          // Get an InputStream and read from the file
          byte b[] = new byte[11];
          System.out.println("Reading from the file");
          InputStream is = file.getFileInputStream();
          is.read(b);
          is.close();

          // Report the result
          String result = new String(b);
          System.out.println("File contents is: " + result);
        }
        catch (Exception e) {
          System.out.println("The following exception occurred " +
                             "while running the HelloWorld example.");
          e.printStackTrace();
          if (!fileSystemName.equals("")) {
    	System.out.println("Make sure the WebLogic server at " +
    	                   url + " was started with " +
    	                   "the property weblogic.io.fileSystem." +
    	                   fileSystemName + " set.");
          }
        }
      }

      private static T3ServicesDef getT3Services(String wlUrl)
           throws javax.naming.NamingException
      {
        T3ServicesDef t3s;
        Hashtable env = new Hashtable();
        env.put(Context.PROVIDER_URL, wlUrl);
        env.put(Context.INITIAL_CONTEXT_FACTORY,
                weblogic.jndi.WLInitialContextFactory.class.getName());
        Context ctx = new InitialContext(env);
        t3s = (T3ServicesDef) ctx.lookup("weblogic.common.T3Services");
        ctx.close();
        return(t3s);
      }
    }
# Change history Release 3.0 Added support for T3FileSystem and T3File, with methods for creating and managing files uniformly, whether located on the client or a remote VM. Release 2.5 -- (8/23/97) First release; included support for T3FileInputStream and T3FileOutputStream.

Copyright © 2000 BEA Systems, Inc. All rights reserved. Required browser: Netscape 4.0 or higher, or Microsoft Internet Explorer 4.0 or higher. Last updated 01/13/1999