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WebLogic Tuxedo Connector Programmer's Guide

# WebLogic Tuxedo Connector JATMI VIEWs

The following sections provide information about how to use WebLogic Tuxedo Connector VIEW buffers:

- Overview of WebLogic Tuxedo Connector VIEW Buffers
- How to Create a VIEW Description File
- How to Use the viewj Compiler
- How to Pass Information to and from a VIEW Buffer
- How to Use VIEW Buffers in JATMI Applications

# Overview of WebLogic Tuxedo Connector VIEW Buffers

Note: For more information on Tuxedo VIEW buffers, see Using a VIEW Typed Buffer.

WebLogic Tuxedo Connector allows you to create a Java VIEW buffer type analogous to a Tuxedo VIEW buffer type derived from an independent C structure. This allows WebLogic Server applications and Tuxedo applications to pass information using a common structure. WebLogic Tuxedo Connector VIEW buffers do not support FML VIEWs or FML VIEWs/Java conversions.

# How to Create a VIEW Description File

Note: `fbname` and `null` fields are not relevant for independent Java and C structures and are ignored by the Java and C VIEW compiler. You must include a value (for example, a dash) as a placeholder in these fields.

Your WebLogic Server application and your Tuxedo application must share the same information structure as defined by the VIEW description. The following format is used for each structure in the VIEW description file:

>     $ /* VIEW structure */
>     VIEW viewname
>     type cname fbname count flag size null

where

- The file name is the same as the VIEW name.
- You can have only one VIEW description per file.
- The VIEW description file is the same file used for both the WebLogic Tuxedo Connector `viewj` compiler and the Tuxedo `viewc` compiler.
- viewname is the name of the information structure.
- You can include a comment line by prefixing it with the # or $ character.
- The following table describes the fields that must be specified in the VIEW description file for each structure.

Table 8-1 VIEW Description File Fields

Field | Description
--- | ---
type | Data type of the field. Can be set to short, long, float, double, char, string, carray, or dec_t (packed decimal).
cname | Name of the field as it appears in the information structure.
fbname | Ignored.
count | Number of times field occurs.
flag | Specifies any of the following optional flag settings: N—zero-way mapping C—generate additional field for associated count member (ACM) L—hold number of bytes transferred for STRING and CARRAY
size | For STRING and CARRAY buffer types, specifies the maximum length of the value. This field is ignored for all other buffer types.
null | User-specified NULL value, or minus sign (-) to indicate the default value for a field. NULL values are used in VIEW typed buffers to indicate empty C structure members. The default NULL value for all numeric types is 0 (0.0 for dec_t). For character types, the default NULL value is \Q\0'. For STRING and CARRAY types, the default NULL value is " ". Constants used, by convention, as escape characters can also be used to specify a NULL value. The VIEW compiler recognizes the following escape constants: \ddd (where d is an octal digit), \0, \n, \t, \v, \r, \f, \\, \', and \". You may enclose STRING, CARRAY, and char NULL values in double or single quotes. The VIEW compiler does not accept unescaped quotes within a user-specified NULL value. You can also specify the keyword NONE in the NULL field of a VIEW member description, which means that there is no NULL value for the member. The maximum size of default values for string and character array members is 2660 characters.

## Example VIEW Description File

The following provides an example VIEW description which uses VIEW buffers to send information to and receive information from a Tuxedo application. The file name for this VIEW is `infoenc`.

Listing 8-1 Example VIEW Description

>     VIEW infoenc
>     #type    cname    fbname  count flag size null
>     float    amount   AMOUNT  2     -    -    0.0
>     short    status   STATUS  2     -    -    0
>     init     term     TERM    2     -    -    0
>     char     mychar   MYCHAR  2     -    -    -
>     string   name     NAME    1     -    16   -
>     carray   carray1  CARRAY1 	1     -    10   -
>     dec_t    decimal  DECIMAL 	1     -    9    - #size ignored by viewj/viewj32
>     END

# How to Use the viewj Compiler

To compile a VIEW typed buffer, run the `viewj` command, specifying the package name and the name of the VIEW description file as arguments. The output file is written to the current directory.

To use the `viewj` compiler, enter the following command:

>     java weblogic.wtc.jatmi.viewj [options] [package] viewfile

To use the `viewj32` compiler, enter the following command:

>     java weblogic.wtc.jatmi.viewj32 [options] [package] viewfile

The arguments for this command are defined as follows:

``

Argument | Description
--- | ---
options | `-associated_fields`: Use to set `AssociatedFieldHandling` to true. This allows `set` and `get` accessor methods to use the values of the associated length and count fields if they are specified in the VIEW description file. If not specified, the default value for `AssociatedFieldHandling` is false. `-bean_names`: Use to create `set` and `get` accessor names that follow JavaBeans naming conventions. The first character of the field name is changed to upper case before the `set` or `get` prefix is added. The signature of indexed `set` accessors for array fields changes from the default signature of `void setAfield(T value, int index)` to `void setAfield(int index, T value).` `-compat_names`: Use to create `set` and `get` accessor names that are formed by taking the field name from the VIEW description file and adding a set or get prefix. Provides compatibility with releases prior to WebLogic Server 8.1 SP2. Default value is `-compat_names` if `-bean_names or -compat_names is not` specified. `-modify_strings`: Use to generate different Java code for encoding strings sent to Tuxedo and decoding strings received from Tuxedo. Encoding code adds a null character to the end of each string. Decoding code truncates each string at the first null character recieved. `-xcommon`: Use to generate output class as extending TypedXCommon instead of TypedView. `-xtype`: Use to generate output class as extending TypedXCType instead of TypedView. Note: `-compat_names` and `-bean_names` are mutually exclusive options.
`package` | The package name to be included in the `.java` source file. Example: examples.wtc.atmi.simpview
`viewfile` | Name of the VIEW description file. Example: `Infoenc`

For example:

- A VIEW buffer is compiled as follows:

>     java weblogic.wtc.jatmi.viewj -compat_names examples.wtc.atmi.simpview infoenc

- A VIEW32 buffer is compiled as follows:

>     java weblogic.wtc.jatmi.viewj32 -compat_names -modify_strings examples.wtc.atmi.simpview infoenc

# How to Pass Information to and from a VIEW Buffer

The output of the `viewj` and `view` `j32` command is a `.java` source file that contains `set` and `get` accessor methods for each field in the VIEW description file. Use these `set` and `get` accessor methods in your Java applications to pass information to and from a VIEW buffer.

The `AssociatedFieldHandling` flag is used to specify if the `set` and `get` methods use the values of the associated length and count fields if they are specified in the VIEW description file.

- `set` methods set the count for an array field and set the length for a string or carray field.
- Array `get` methods return an array that is at most the size of the associated count field.
- String and carray `get` methods return data that is at most the length of the associated length field.

Use one of the following to set or get the state of the `AssociatedFieldHandling` flag:

- Use the -`associated_fields` option for the `viewj` and `viewj32` compiler to set the `AssociatedFieldHandling` flag to true..
- Invoke the `void setAssociatedFieldHandling(boolean state)` method in your Java application to set the state of the `AssociatedFieldHandling` flag.

- If false, the `set` and `get` methods ignore the length and count fields.
- If true, the `set` and `get` methods use the values of the associated length and count fields if they are specified in the VIEW description file.
- The default state is false.

- Invoke the `boolean getAssociatedFieldHandling()` method in your Java application to return the current state of `AssociatedFieldHandling`.

# How to Use VIEW Buffers in JATMI Applications

Use the following steps when incorporating VIEW buffers in your JATMI applications:

1. Create a VIEW description file for your application as described in How to Create a VIEW Description File.
2. Compile the VIEW description file as described in How to Use the viewj Compiler.
3. Use the set and get accessor methods to pass information to and recieve information from a VIEW buffer as described in How to Pass Information to and from a VIEW Buffer.

See the `examples/wtc/atmi/simpview/ViewClient.java` file in your WebLogic Server distribution for an example of how a client uses accessors to pass information to and from a VIEW buffer.

4. Import the output of the VIEW compiler into your source code.
5. If necessary, compile the VIEW description file for your Tuxedo application and include the output in your C source file as described in Using a VIEW Typed Buffer.
6. Configure a WTCServer MBean with a Resources Mbean that specifies the VIEW buffer type (VIEW or VIEW32) and the fully qualified class name of the compiled Java VIEW description file.
7. Build and launch your Tuxedo application.
8. Build and launch your WebLogic Server Application.