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Oracle® HTTP Server mod_plsql User's Guide 10g Release 2 (10.2) Part Number B14337-01 |
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# 1 Understanding mod_plsql

mod_plsql provides support for building PL/SQL-based applications on the Web. PL/SQL stored procedures retrieve data from a database and generate HTTP responses containing data and code to display in a Web browser. mod_plsql also supports other Oracle products such as OracleAS Portal.

This chapter discusses the following topics:

- Processing Client Requests

- Database Access Descriptors (DADs)

- Invoking mod_plsql

- Transaction Mode

- Supported Data Types

- Parameter Passing

- File Upload and Download

- Path Aliasing (Direct Access URLs)

- Common Gateway Interface (CGI) Environment Variables

- Restrictions in mod_plsql

## 1.1 Processing Client Requests

mod_plsql is an Oracle HTTP Server plug-in that communicates with the database. It maps browser requests into database stored procedure calls over a SQL*Net connection. It is often indicated by a `/pls` virtual path.

The following scenario provides an overview of what steps occur when a server receives a client request:

Figure 1-1 Overview of the Process When a Server Receives a Client Request

Description of "Figure 1-1 Overview of the Process When a Server Receives a Client Request"

1. The Oracle HTTP Server receives a PL/SQL Server Page request from a client browser.

2. The Oracle HTTP Server routes the request to mod_plsql.

3. The request is forwarded by mod_plsql to the Oracle Database. By using the configuration information stored in your DAD, mod_plsql connects to the database.

4. mod_plsql prepares the call parameters, and invokes the PL/SQL procedure in the application.

5. The PL/SQL procedure generates an HTML page using data and the PL/SQL Web Toolkit accessed from the database.

6. The response is returned to mod_plsql.

7. The Oracle HTTP Server sends the response to the client browser.

The procedure that mod_plsql invokes returns the HTTP response to the client. To simplify this task, mod_plsql includes the PL/SQL Web Toolkit, which contains a set of packages called the owa packages. Use these packages in your stored procedure to get information about the request, construct HTML tags, and return header information to the client. Install the toolkit in a common schema so that all users can access it.

## 1.2 Database Access Descriptors (DADs)

Each mod_plsql request is associated with a Database Access Descriptor (DAD), a set of configuration values used for database access. A DAD specifies information such as:

- the database alias (Oracle Net service name).

- a connect string, if the database is remote.

- a procedure for uploading and downloading documents.

You can also specify username and password information in a DAD. If they are not specified, the user is prompted to enter a username and password when the URL is invoked.

See Also: Oracle HTTP Server Administrator's Guide for descriptions of the DAD parameters and an overview of the mod_plsql configuration files.

## 1.3 Invoking mod_plsql

To invoke mod_plsql in a Web browser, input the URL in the following format:

    protocol://hostname[:port]/DAD_location/[[!][schema.][package.]proc_name[?query_string]]

Table 1-1 Invoking mod_plsql Parameters

Parameter | Description
--- | ---
protocol | Either `http` or `https`. For SSL, use `https`.
hostname | The machine where the Web server is running.
port (optional) | The port at which the Web server is listening. If omitted, port 80 is assumed.
DAD location | A virtual path to handle PL/SQL requests that you have configured in the Web server. The DAD location can contain only ASCII characters.
! character (optional) | Indicates to use the flexible parameter passing scheme. See Section 1.6.2, "Flexible Parameter Passing" for more information.
schema (optional) | The database schema name. If omitted, name resolution for package.proc_name occurs based on the database user that the URL request is processed as.
package (optional) | The package that contains the PL/SQL stored procedure. If omitted, the procedure is standalone.
proc_name | The PL/SQL stored procedure to run. This must be a procedure and not a function. It can accept only IN arguments.
?query_string (optional) | The parameters for the stored procedure. The string follows the format of the GET method. For example: Multiple parameters are separated with the `&` character. Space characters in the values to be passed in are replaced with the `+` character. If you use HTML forms to generate the string (as opposed to generating the string yourself), the formatting is done automatically. The HTTP request may also choose the HTTP POST method to post data to mod_plsql. See "POST, GET, and HEAD Methods" for more information.

Example 1-1 Invoking A Procedure That Does Not Take Arguments

    http://www.acme.com:9000/pls/mydad/mypackage.myproc

The Web server running on `www.acme.com` and listening at port `9000` handles the request. When the Web server receives the request, it passes the request to mod_plsql. This is because the `/pls/mydad` indicates that the Web server is configured to invoke mod_plsql. It then uses the DAD associated with `/pls/mydad` and runs the `myproc` procedure stored in `mypackage`.

Example 1-2 Invoking A Procedure That Takes Arguments

    http://www.acme.com:9000/pls/mydad/mypackage.myproc?a=v&b=1

The Web server running on `www.acme.com` and listening at port `9000` handles the request. When the Web server receives the request, it uses the DAD associated with `/pls/mydad` and runs the `myproc` procedure stored in `mypackage`, and passes two arguments, `a` and `b`, with the values `v`, and `1` to the procedure.

Example 1-3 Invoking the Default Procedure Stored in the DAD Configuration

    http://www.acme.com:9000/pls/mydad

The Web server running on `www.acme.com` and listening at port `9000` handles the request. When the Web server receives the request, it uses the DAD associated with `/pls/mydad` and invokes the default procedure configured in the DAD. For example, if the configuration parameter `PlsqlDefaultPage` in the DAD `/pls/mydad` is set to `myschema.mypackage.myproc`, then the procedure `myschema.mypackage.myproc` is invoked for the request.

In this example, the default home page for the `mydad` DAD (as specified in the DAD Configuration) is displayed.

POST, GET, and HEAD Methods

The POST, GET, and HEAD methods in the HTTP protocol instruct browsers on how to pass parameter data (usually in the form of name-value pairs) to applications. The parameter data is generated by HTML forms.

mod_plsql applications can use any of the methods. Each method is as secure as the underlying transport protocol (HTTP or HTTPS).

- When using the POST method, parameters are passed in the request body. Generally, if you are passing large amounts of parameter data to the server, use the POST method.

- When using the GET method, parameters are passed using a query string. The limitation of this method is that the length of the value in a name-value pair cannot exceed the maximum length for the value of an environment variable, as imposed by the underlying operating system. In addition, operating systems have a limit on how many environment variables you can define.

- When using the HEAD method, it has the same functionality as the GET method. The only difference is that only the HTTP status line and the HTTP headers are passed back. No content data is streamed back to the browser. This is useful for monitoring tools in which you are only interested if the request is processed correctly.

- Mixed Mode - In mod_plsql you can pass some of the parameters in a query string and the remaining ones as POST data. For example, if you have a procedure `foo` (a varchar2, b number), and want to pass values "v" and "1" to 'a' and 'b' respectively, you could do so in three ways to create URLs:

  - All values are specified as part of the query string.

    `http://host:port/pls/DAD/foo?a=v&b=1`

  - All values are specified as part of the POST data.

    `http://host:port/pls/DAD/foo, POST data="a=v&b=1"`

  - Some of the parameters are specified in the URL and the rest in the POST data.

    `http://host:port/pls/DAD/foo?a=v, POST data="b=1"`

Note: POST data is generated as part of the input fields on a HTML form. You should not create the POST string manually in the PL/SQL procedure, or in the URL. The Submit operation of the HTML form will generate a POST request and pass the value to your procedure.

## 1.4 Transaction Mode

After processing a URL request for a procedure invocation, mod_plsql performs a rollback if there were any errors. Otherwise, it performs a commit. This mechanism does not allow a transaction to span across multiple HTTP requests. In this stateless model, applications typically maintain state using HTTP cookies or database tables.

## 1.5 Supported Data Types

Because HTTP supports character streams only, mod_plsql supports the following subset of PL/SQL data types:

- NUMBER

- VARCHAR2

- TABLE OF NUMBER

- TABLE OF VARCHAR2

Records are not supported.

## 1.6 Parameter Passing

mod_plsql supports:

- Parameter passing by name

  Each parameter in a URL that invokes procedure or functions identified by a unique name. Overloaded parameters are supported. See Section 1.6.1, "Parameter Passing by Name (Overloaded Parameters)" for more information.

- Flexible parameter passing

  Procedures are prefixed by a ! character. See Section 1.6.2, "Flexible Parameter Passing" for more information.

- Large (up to 32K) parameters passing

  See Section 1.6.3, "Large Parameter Passing" for more information.

  Note: mod_plsql handles multi-value variables by storing the values in a PL/SQL table. This enables you to be flexible about how many values the user can pick, and it makes it easy for you to process the user's selections as a unit. Each value is stored in a row in the PL/SQL table, starting at index 1. The first value (in the order that it appears in the query string) of a variable that has multiple values is placed at index 1, the second value of the same variable is placed at index 2, and so on. If the order of the values in the PL/SQL table is significant in your procedure, you need to determine the order in which the variables appear in the query string, or modify your PL/SQL application to do the ordering internally. If you do not have variables with multiple values, the order in which the variables appear does not matter, because their values are passed to the procedure's parameters by name, and not by position. The PL/SQL tables used as parameters in the mod_plsql environment must have a base type of `VARCHAR2`. Oracle can convert `VARCHAR2` to other data types such as `NUMBER`, `DATE`, or `LONG`. The maximum length of a `VARCHAR2` variable is 32K. If you cannot guarantee that at least one value will be submitted to the PL/SQL table (for example, the user can select no options), use a hidden form element to provide the first value. Not providing a value for the PL/SQL table produces an error, and you cannot provide a default value for a PL/SQL table.

### 1.6.1 Parameter Passing by Name (Overloaded Parameters)

Overloading allows multiple subprograms (procedures or functions) to have the same name, but differ in the number, order, or the datatype family of the parameters. When you call an overloaded subprogram, the PL/SQL compiler determines which subprogram to call based on the data types passed.

PL/SQL enables you to overload local or packaged subprograms. Standalone subprograms cannot be overloaded.

You must give parameters different names for overloaded subprograms that have the same number of parameters. Because HTML data is not associated with datatypes, mod_plsql does not know which version of the subprogram to call.

For example, although PL/SQL enables you to define two procedures using the same parameter names for the procedures, an error occurs if you use this with mod_plsql.

    -- legal PL/SQL, but not for mod_plsql
    CREATE PACKAGE my_pkg AS
      PROCEDURE my_proc (val IN VARCHAR2);
      PROCEDURE my_proc (val IN NUMBER);
    END my_pkg;

To avoid the error, name the parameters differently. For example:

    -- legal PL/SQL and also works for mod_plsql
    CREATE PACKAGE my_pkg AS
      PROCEDURE my_proc (valvc2 IN VARCHAR2);
      PROCEDURE my_proc (valnum IN NUMBER);
    END my_pkg;

The URL to invoke the first version of the procedure looks similar to:

    http://www.acme.com/pls/mydad/my_pkg.my_proc?valvc2=input

The URL to invoke the second version of the procedure looks similar to:

    http://www.acme.com/pls/mydad/my_pkg.my_proc?valnum=34

Overloading and PL/SQL Arrays

If you have overloaded PL/SQL procedures where the parameter names are identical, but the data type is owa_util.ident_arr (a table of varchar2) for one procedure and a scalar type for another procedure, mod_plsql can still distinguish between the two procedures. For example, if you have the following procedures:

    CREATE PACKAGE my_pkg AS
      PROCEDURE my_proc (val IN VARCHAR2); -- scalar data type
      PROCEDURE my_proc (val IN owa_util.ident_arr); -- array data type
    END my_pkg;

Each of these procedures has a single parameter of the same name, `val`.

When mod_plsql gets a request that has only one value for the `val` parameter, it invokes the procedure with the scalar data type.

Example 1-4 Sending a URL to Execute the Scalar Version of a Procedure

Send the following URL to execute the scalar version of the procedure:

    http://www.acme.com/pls/mydad/my_proc?val=john

When mod_plsql gets a request with more than one value for the `val` parameter, it then invokes the procedure with the array data type.

Example 1-5 Sending a URL to Execute the Array Version of a Procedure

Send the following URL to execute the array version of the procedure:

    http://www.acme.com/pls/mydad/my_proc?val=john&val=sally

To ensure that the array version executes, use hidden form elements on your HTML page to send dummy values that are checked and discarded in your procedure.

### 1.6.2 Flexible Parameter Passing

You can have HTML forms from which users can select any number of elements. If these elements have different names, you would have to create overloaded procedures to handle each possible combination. Alternatively, you could insert hidden form elements to ensure that the names in the query string are consistent each time, regardless of what elements the user chooses. mod_plsql makes this operation easier by supporting flexible parameter passing to handle HTML forms where users can select any number of elements.

To use flexible parameter passing for a URL-based procedure invocation, prefix the procedure with an exclamation mark (!) in the URL. You can use two or four parameters. The two parameter interface provides improved performance with mod_plsql. The four parameter interface is supported for compatibility.

#### 1.6.2.1 Two Parameter Interface

    procedure [proc_name]
         (name_array IN [array_type],
         value_array IN  [array_type]);

Table 1-2 Two Parameter Interface Parameters

Parameter | Description
--- | ---
proc_name (required) | The name of the PL/SQL procedure that you are invoking.
name_array | The names from the query string (indexed from 1) in the order submitted.
value_array | The values from the query string (indexed from 1) in the order submitted.
array_type (required) | Any PL/SQL index-by table of varchar2 type (Example, owa.vc_arr).

Example 1-6 Two Parameter Interface

If you send the following URL:

    http://www.acme.com/pls/mydad/!scott.my_proc?x=john&y=10&z=doe

The exclamation mark prefix (!) instructs mod_plsql to use flexible parameter passing. It invokes procedure scott.myproc and passes it the following two arguments:

    name_array ==> ('x', 'y', 'z')
    value_array ==> ('john', '10', 'doe')

Note: When using this style of Flexible Parameter Passing, the procedure must be defined with the parameters name_array and value_array. The datatypes of these arguments should match the datatypes shown in the example.

#### 1.6.2.2 Four Parameter Interface

The four parameter interface is supported for compatibility.

    procedure [proc_name]
         (num_entires IN NUMBER,
         name_array  IN  [array_type],
         value_array IN  [array_type],
         reserved in [array_type]);

Table 1-3 Four Parameter Interface Parameters

Parameter | Description
--- | ---
proc_name (required) | The name of the PL/SQL procedure that you are invoking.
num_entries | The number of name_value pairs in the query string
name_array | The names from the query string (indexed from 1) in the order submitted.
value_array | The values from the query string (indexed from 1) in the order submitted.
reserved | Not used. It is reserved for future use.
array_type (required) | Any PL/SQL index-by table of varchar2 type (Example, owa.vc_arr).

Example 1-7 Four Parameter Interface

If you send the following URL, where the query_string has duplicate occurrences of the name "x":

    http://www.acme.com/pls/mydad/!scott.my_pkg.my_proc?x=a&y=b&x=c

The exclamation mark prefix (!) instructs mod_plsql to use flexible parameter passing. It invokes procedure `scott.my_pkg.myproc` and passes it the following arguments:

    num_entries ==> 3
    name_array ==> ('x', 'y', 'x');
    value_array ==> ('a', 'b', 'c')
    reserved ==> ()

Note: When using this style of Flexible Parameter Passing, the procedure must be defined with the parameters num_entries, name_array, value_array, and reserved. The datatypes of these arguments should match the datatypes shown in the example.

### 1.6.3 Large Parameter Passing

The values passed as scalar arguments and the values passed as elements to the index-by table of varchar2 arguments can be up to 32K in size.

For example, when using flexible parameter passing (described in Section 1.6.2, "Flexible Parameter Passing"), each name or value in the query_string portion of the URL gets passed as an element of the `name_array` or `value_array` argument to the procedure being invoked. These names or values can be up to 32KB in size.

## 1.7 File Upload and Download

mod_plsql enables you to:

- Upload and download files as raw byte streams without any character set conversions. The files are uploaded into the document table. A primary key is passed to the PL/SQL upload handler routine so that it can retrieve the appropriate table row.

- Specify one or more tables for each application, for uploaded files so that files from different applications are not mixed together.

- Provide access to files in these tables through a URL format that doesn't use query strings, for example:

      http://www.acme.com:9000/pls/mydad/docs/cs250/lecture1.htm

  This is required to support uploading a set of files that have relative URL references to each other.

- Upload multiple files for each form submission.

- Upload files into LONG RAW and BLOB (Binary Large Object) types of columns in the document table.

This section discusses the following:

- Document Table Definition

- Old Style Document Table Definition

- Configuration Parameters for Document Upload/Downloading

- File Upload

- Specifying Attributes (Mime Types) of Uploaded Files

- Uploading Multiple Files

- File Download

- Direct BLOB Download

### 1.7.1 Document Table Definition

You can specify the document storage table for each DAD. The document storage table must have the following definition:

    CREATE TABLE [table_name] (
         NAME           VARCHAR2(256) UNIQUE NOT NULL,
         MIME_TYPE      VARCHAR2(128),
         DOC_SIZE       NUMBER,
         DAD_CHARSET    VARCHAR2(128),
         LAST_UPDATED   DATE,
         CONTENT_TYPE   VARCHAR2(128),
         [content_column_name] [content_column_type]
         [ , [content_column_name] [content_column_type]]
    );

Users can choose the `table_name.` The `content_column_type` type must be either LONG RAW or BLOB.

The `content_column_name` depends on the corresponding `content_column_type`:

- If the content_column_type is LONG RAW, the `content_column_name` must be CONTENT.

- If the content_column_type is BLOB, the `content_column_name` must be BLOB_CONTENT.

An example of legal document table definition is:

    CREATE TABLE MYDOCTABLE (
      NAME               VARCHAR(128)   UNIQUE NOT NULL,
      MIME_TYPE          VARCHAR(128),
      DOC_SIZE           NUMBER,
      DAD_CHARSET        VARCHAR(128),
      LAST_UPDATED       DATE,
      CONTENT_TYPE       VARCHAR(128),
      CONTENT            LONG RAW,
      BLOB_CONTENT       BLOB ;
    );

#### 1.7.1.1 Semantics of the CONTENT Column

The contents of the table are stored in a content column. There can be more than one content column in a document table. However, for each row in the document table, only one of the content columns is used. The other content columns are set to NULL.

#### 1.7.1.2 Semantics of the CONTENT_TYPE Column

The `content_type` column tracks in which content column the document is stored. When a document is uploaded, mod_plsql sets the value of this column to the type name.

For example, if a document was uploaded into the BLOB_CONTENT column, then the `CONTENT_TYPE` column for the document is set to the string 'BLOB'.

#### 1.7.1.3 Semantics of the LAST_UPDATED Column

The `LAST_UPDATED` column reflects a document's creation or last modified time. When a document is uploaded, mod_plsql sets the `LAST_UPDATED` column for the document to the database server time.

If an application then modifies the contents or attributes of the document, it must also update the `LAST_UPDATED` time.

mod_plsql uses the `LAST_UPDATED` column to check and indicate to the HTTP client (browser) if the browser can use a previously cached version of the document. This reduces network traffic and improves server performance.

#### 1.7.1.4 Semantics of the DAD_CHARSET Column

The `DAD_CHARSET` column keeps track of the character set setting at the time of the file upload. This column is reserved for future use.

### 1.7.2 Old Style Document Table Definition

For backward capability with the document model used by older releases of WebDB 2.x, mod_plsql also supports the following old definition of the document storage table where the CONTENT_TYPE, DAD_CHARSET and LAST_UPDATED columns are not present.

    /* older style document table definition (DEPRECATED) */
    CREATE TABLE [table_name]
    (
        NAME         VARCHAR2(128),
        MIME_TYPE    VARCHAR2(128),
        DOC_SIZE     NUMBER,
        CONTENT      LONG RAW

    );

### 1.7.3 Configuration Parameters for Document Upload/Downloading

The following configuration parameters in the DAD affect a document upload/download operation:

- "PlsqlDocumentTablename"

- "PlsqlDocumentPath (Document Access Path)"

- "PlsqlDocumentProcedure (Document Access Procedure)"

- "PlsqlUploadAsLongRaw"

Example 1-8 Parameters for Document Upload/Download

If the configuration for these parameters in a DAD is as follows:

    PlsqlDocumentTablename   scott.my_document_table
    PlsqlUploadAsLongRaw   html
    PlsqlDocumentPath   docs
    PlsqlDocumentProcedure   scott.my_doc_download_procedure

then:

- mod_plsql will retrieve data from, or store to a database table called my_document_table in the scott schema.

- All file extensions except `.html` will be uploaded to the document table as BLOBs. All files with `.html` extension will be uploaded as Long Raw.

- All URLs which have the keyword docs immediately following the DAD location will result in invocation of the procedure scott.my_doc_download_procedure.

  Typically, this procedure will call wpg_docload.download_file to initiate a file download for a file whose name is based on the URL specification.

A simple example with the preceding configuration is:

    http://www.acme.com/pls/dad/docs/index.html

This results in downloading of the file `index.html` from the Long Raw column of the database table scott.my_document_table. Note that the application procedure has full control on the file download to initiate, and has the flexibility to define a more complex `PlsqlDocumentProcedure` that implements file-level access controls and versioning.

Note: The application defined procedure scott.my_doc_download_procedure has to be defined without arguments, and should rely on the CGI environment variables to process the request.

#### 1.7.3.1 PlsqlDocumentTablename

The `PlsqlDocumentTablename` parameter specifies the table for storing documents when file uploads are performed through this DAD.

Syntax:

    PlsqlDocumentTablename  [document_table_name]

    PlsqlDocumentTablename  my_documents

or,

    PlsqlDocumentTablename  scott.my_document_table

#### 1.7.3.2 PlsqlDocumentPath (Document Access Path)

The `PlsqlDocumentPath` parameter specifies the path element to access a document. The `PlsqlDocumentPath` parameter follows the DAD name in the URL. For example, if the document access path is `docs`, then the URL would look similar to:

    http://www.acme.com/pls/mydad/docs/myfile.htm

The `mydad` is the DAD name and `myfile.htm` is the file name.

Syntax:

    PlsqlDocumentPath  [document_access_path_name]

#### 1.7.3.3 PlsqlDocumentProcedure (Document Access Procedure)

The `PlsqlDocumentProcedure` procedure is an application-specified procedure. It has no parameters and processes a URL request with the document access path. The document access procedure calls `wpg_docload.download_file(filename)` to download a file. It knows the filename based on the URL specification. For example, an application can use this to implement file-level access controls and versioning. An example of this is in Section 1.7.7, "File Download".

Syntax:

    PlsqlDocumentProcedure  [document_access_procedure_name]

Example 1-9 PlsqlDocumentProcedure

    PlsqlDocumentProcedure  my_access_procedure

or,

    PlsqlDocumentProcedure  scott.my_pkg.my_access_procedure

#### 1.7.3.4 PlsqlUploadAsLongRaw

The DAD parameter, `PlsqlUploadAsLongRaw`, configures file uploads based on their file extensions. The value of a `PlsqlUploadAsLongRaw` DAD parameter is a one-entry-for-each-line list of file extensions. Files with these extensions are uploaded by mod_plsql into the content column of `LONG RAW` type in the document table. Files with other extensions are uploaded into the BLOB content column.

The file extensions can be text literals (jpeg, gif, and so on) or an asterisk (*) matches any file whose extension has not been listed in the `PlsqlUploadAsLongRaw` setting.

Syntax:

    PlsqlUploadAsLongRaw  [file_extension]
    PlsqlUploadAsLongRaw *

`[file_extension]` is an extension for a file (with or without the '.' character, for example, 'txt' or '.txt') or the wildcard character *.

Example 1-10 PlsqlUploadAsLongRaw

    PlsqlUploadAsLongRaw  html
    PlsqlUploadAsLongRaw  txt
    PlsqlUploadAsLongRaw  *

### 1.7.4 File Upload

To send files from a client machine to a database, create an HTML page that contains:

- A FORM tag whose enctype attribute is set to `multipart/form-data` and whose action attribute is associated with a mod_plsql procedure call, referred to as the "action procedure."

- An INPUT element whose type and name attributes are set to file. The `INPUT type="file"` element enables a user to browse and select files from the file system.

When a user clicks Submit, the following events occur:

1. The browser uploads the file specified by the user as well as other form data to the server.

2. mod_plsql stores the file contents in the database in the document storage table. The table name is derived from the `PlsqlDocumentTablename` DAD setting.

3. The action procedure specified in the action attribute of the FORM is run (similar to invoking a mod_plsql procedure without file upload).

   Note: The parsing of HTML documents is deprecated in mod_plsql. mod_plsql used to parse the content of an HTML file when it was uploaded, and identified other files that the HTML document was referring to. This information was then stored into a table. The table name was constructed by appending the name of the document table with "part". This functionality was found to be not of use to customers and has been deprecated, starting in version 9.0.4 of mod_plsql.

The following example shows an HTML form that lets a user select a file from the file system to upload. The form contains other fields to provide information about the file.

    <html>
       <head>
          <title>test upload</title>
       </head>
       <body>
       <FORM     enctype="multipart/form-data"
          action="pls/mydad/write_info"
          method="POST">
          <p>Author's Name:<INPUT type="text" name="who">
          <p>Description:<INPUT type="text" name="description"><br>
          <p>File to upload:<INPUT type="file" name="file"><br>
          <p><INPUT type="submit">
       </FORM>
       </body>
    </html>

When a user clicks Submit on the form:

1. The browser uploads the file listed in the `INPUT type="file"` element.

2. The `write_info` procedure then runs.

3. The procedure writes information from the form fields to a table in the database and returns a page to the user.

   Note: The action procedure does not have to return anything to the user, but it is a good idea to let the user know whether the Submit succeeded or failed, as shown subsequently.

       procedure write_info (
            who         in varchar2,
            description in varchar2,
            file        in varchar2) as
       begin
            insert into myTable values (who, description, file);
            htp.htmlopen;
            htp.headopen;
            htp.title('File Uploaded');
            htp.headclose;
            htp.bodyopen;
            htp.header(1, 'Upload Status');
            htp.print('Uploaded ' || file || ' successfully');
            htp.bodyclose;
            htp.htmlclose;
       end;

The filename obtained from the browser is prefixed with a generated directory name to reduce the possibility of name conflicts. The "action procedure" specified in the form renames this name. So, for example, when `/private/minutes.txt` is uploaded, the name stored in the table by the mod_plsql is `F9080/private/minutes.txt.` The application can rename this in the called stored procedure. For example, the application can rename it to `scott/minutes.txt`.

### 1.7.5 Specifying Attributes (Mime Types) of Uploaded Files

In addition to renaming the uploaded file, the stored procedure can alter other file attributes. For example, the form in the example from Section 1.7.4, "File Upload" could display a field for allowing the user to input the uploaded document's Multipurpose Internet Mail Extension (MIME) type.

The MIME type can be received as a parameter in `write_info`. The document table would then store the mime type for the document instead of the default mime type that is parsed from the multipart form by mod_plsql when uploading the file.

### 1.7.6 Uploading Multiple Files

To send multiple files in a single submit, the upload form must include multiple <INPUT type="file" name="file"> elements. If more than one file INPUT element defines `name` to be of the same name, then the action procedure must declare that parameter name to be of type owa.vc_arr. The names defined in the file INPUT elements could also be unique, in which case, the action procedure must declare each of them to be of varchar2. For example, if a form contained the following elements:

    <INPUT type="file" name="textfiles">
    <INPUT type="file" name="textfiles">
    <INPUT type="file" name="binaryfile">

As a result, the action procedure must contain the following parameters:

    procedure handle_text_and_binary_files(textfiles IN owa.vc_arr, binaryfile IN varchar2).

### 1.7.7 File Download

After you have sent files to the database, you can download them, delete them from the database, and read and write their attributes.

To download a file, create a stored procedure without parameters that calls `wpg_docload.download_file` (file_name) to initiate the download.

The HTML page presented to the user simply has a link to a URL, which includes the Document Access Path and specifies the file to be downloaded.

For example, if the DAD specifies that the Document Access Path is `docs` and the Document Access Procedure is `mydad.process_download`, then the `mydad.process_download` procedure is called when the user clicks on the URL:

    http://www.acme.com:9000/pls/mydad/docs/myfile.htm

An example implementation of process_download is:

    procedure process_download is
            v_filename varchar2(255);
    begin
      -- getfilepath() uses the SCRIPT_NAME and PATH_INFO cgi
      -- environment variables to construct the full path name of
      -- the file URL, and then returns the part of the path name
      -- following '/docs/'
      v_filename := getfilepath;
      select name into v_filename from plsql_gateway_doc
      where UPPER(name) = UPPER(v_filename);
      -- now we call docload.download_file to initiate
      -- the download.
      wpg_docload.download_file(v_filename);
    exception
      when others then
            v_filename := null;
    end process_download;

Any time you call `wpg_docload.download_file(filename)` from a procedure running in mod_plsql, a download of the file `filename` is initiated. However, when a file download begins, no other HTML (produced through HTP interfaces) generated by the procedure, is passed back to the browser.

mod_plsql looks for the filename in the document table. There must be a unique row in the document table whose NAME column matches the filename. mod_plsql generates the HTTP response headers based on the information in the MIME_TYPE column of the document table. The `content_type` column's value determines which content columns the document's content comes from. The contents of the document are sent as the body of the HTTP response.

### 1.7.8 Direct BLOB Download

You can also download contents stored as Binary Large Object (BLOB) data type.

1. Create a stored procedure that calls wpg_docload.download_file(blob) where blob is of data type BLOB. Since mod_plsql has no information about the contents in the BLOB, you must supply them.

2. Setup the Content-Type and other headers.

   Example: The following procedure uses the name from the argument to select a BLOB from a table and initiates the Direct BLOB download:

       create or replace procedure download_blob(varchar2 name) is
       myblob blob;
       begin

   1. Select the BLOB out of mytable using the name argument

          select blob_data into myblob from mytable where blob_name = name;

   2. Setup headers which describes the content

          owa_util.mime_header('text/html', FALSE);
          htp.p('Content-Length: ' || dbms_lob.getlength(myblob));
          owa_util.http_header_close;

   3. Initiate Direct BLOB download

          wpg_docload.download_file(myblob);
          end;

      The structure of the `mytable` table:

          create table mytable
          (
          blob_name varchar2(128),
          blob_data blob
          );

3. The HTML page presented to the user has a link to a URL that calls this stored procedure with the correct argument(s).

4. When a Direct BLOB download is initiated, no other HTML (produced through the HTP interface) generated by the procedure is passed back to the browser.

## 1.8 Path Aliasing (Direct Access URLs)

Path Aliasing enables applications using mod_plsql to provide direct reference to its objects using simple URLs. The Path Aliasing functionality is a generalization of how the document download functionality is provided. The following configuration parameters in the DAD are used for Path Aliasing:

- PlsqlPathAlias

- PlsqlPathAliasProcedure

For Example, if the configuration for these parameters in a DAD is as follows:

    PlsqlPathAlias   myalias
    PlsqlPathAliasProcedure   scott.my_path_alias_procedure

then, all URLs that have the keyword myalias immediately following the DAD location will invoke the procedure scott.my_path_alias_procedure. Based on the URL specification, this procedure can initiate an appropriate response.

Note: The application defined procedure scott.my_path_alias_procedure has to be defined to take one argument of type varchar2 called p_path. This argument will receive everything following the keyword used in PlsqlPathAlias. For example, in the preceding configuration, the URL: `http://www.acme.com/pls/dad/myalias/MyFolder/MyItem` will result in the procedure scott.my_path_alias_procedure receiving the argument MyFolder/MyItem.

## 1.9 Common Gateway Interface (CGI) Environment Variables

The OWA_UTIL package provides an API to get the values of CGI environment variables. The variables provide context to the procedure being executed through mod_plsql. Although mod_plsql is not operated through CGI, the PL/SQL application invoked from mod_plsql can access these CGI environment variables.

The list of CGI environment variables is as follows:

- HTTP_AUTHORIZATION

- DAD_NAME

- DOC_ACCESS_PATH

- HTTP_ACCEPT

- HTTP_ACCEPT_CHARSET

- HTTP_ACCEPT_LANGUAGE

- HTTP_COOKIE

- HTTP_HOST

- HTTP_PRAGMA

- HTTP_REFERER

- HTTP_USER_AGENT

- PATH_ALIAS

- PATH_INFO

- HTTP_ORACLE_ECID

- DOCUMENT_TABLE

- REMOTE_ADDR

- REMOTE_HOST

- REMOTE_USER

- REQUEST_CHARSET (refer to Section 1.9.2.1, "REQUEST_CHARSET CGI Environment Variable")

- REQUEST_IANA_CHARSET (refer to Section 1.9.2.2, "REQUEST_IANA_CHARSET CGI Environment Variable")

- REQUEST_METHOD

- REQUEST_PROTOCOL

- SCRIPT_NAME

- SCRIPT_PREFIX

- SERVER_NAME

- SERVER_PORT

- SERVER_PROTOCOL

A PL/SQL application can get the value of a CGI environment variable using the owa_util.get_cgi_env interface.

Syntax:

    owa_util.get_cgi_env(param_name in varchar2) return varchar2;

param_name is the name of the CGI environment variable. param_name is case-insensitive.

### 1.9.1 Adding and Overriding CGI Environment Variables

The `PlsqlCGIEnvironmentList` DAD parameter is a one-entry-for-each-line list of name and value pairs that can override any environment variables or add new ones. If the name is one of the original environment variables (as listed in Section 1.9, "Common Gateway Interface (CGI) Environment Variables"), that environment variable is overridden with the given value. If the name is not in the original list, a new environment variable is added into the list with that same name and value given in the parameter.

Note: Refer to the Oracle HTTP Server Administrator's Guide for information about the mod_plsql Configuration Files.

If no value is specified for the parameter, then the value is obtained from the Oracle HTTP Server. With Oracle HTTP Server, you can pass the DOCUMENT_ROOT CGI Environment variable by specifying:

    PlsqlCGIEnvironmentList DOCUMENT_ROOT

New environment variables passed in through this configuration parameter are available to the PL/SQL application through the owa_util.get_cgi_env interface.

Example 1-11 PlsqlCGIEnvironmentList with Environment Variable Overrides

    PlsqlCGIEnvironmentList SERVER_NAME=myhost.mycompany.com
    PlsqlCGIEnvironmentListREMOTE_USER=testuser

This example overrides the SERVER_NAME and the REMOTE_USER CGI environment variables with the given values since they are part of the original list.

Example 1-12 PlsqlCGIEnvironmentList with New Environment Variable

    PlsqlCGIEnvironmentList MYENV_VAR=testing
    PlsqlCGIEnvironmentList SERVER_NAME=
    PlsqlCGIEnvironmentListREMOTE_USER=user2

This example overrides the SERVER_NAME and the REMOTE_USER variables. The SERVER_NAME variable is deleted since there is no value given to it. A new environment variable called MYENV_VAR is added since it is not part of the original list. It is assigned the value of "testing".

### 1.9.2 PlsqlNLSLanguage

For mod_plsql, the Globalization Support variable (`PlsqlNLSLanguage`) can be set either as an environment variable or at the DAD level, the `PlsqlNLSLanguage` parameter of the database must match that of the Oracle HTTP Server, or the `PlsqlNLSLanguage` parameter of the database and Oracle HTTP Server, must be of fixed character width and both must be the same size.

If `PlsqlNLSLanguage` is not configured at the DAD level, the Globalization Support setting is picked up from the environment. If it does not exist, the default rules apply for NLS_LANG settings for Oracle.

#### 1.9.2.1 REQUEST_CHARSET CGI Environment Variable

Every request to mod_plsql is associated with a DAD. The CGI environment variable REQUEST_CHARSET is set as follows:

- The REQUEST_CHARSET is set to the default character set in use, derived from the `PlsqlNLSLanguage` environment variable. However, if the DAD level `PlsqlNLSLanguage` parameter is set, that derives the character set information instead.

The PL/SQL application can access this information by a function call of the form:

    owa_util.get_cgi_env('REQUEST_CHARSET');

#### 1.9.2.2 REQUEST_IANA_CHARSET CGI Environment Variable

This is the IANA (Internet Assigned Number Authority) equivalent of the REQUEST_CHARSET CGI environment variable. IANA is an authority that globally coordinates the standards for charsets on the Internet.

## 1.10 Restrictions in mod_plsql

The following restrictio ns exist in mod_plsql:

- The maximum length of the HTTP cookie header is 32000 bytes. Values higher than this generate an error. This limit is due to the PL/SQL varchar2 limit.

- The maximum length of any single cookie within the HTTP cookie is 3990. Values higher than this generate an error. This limit is due to the OCI array bind limit of strings in arrays.

- There is a hard maximum cookie limit in mod_plsql that limits the number of cookies being set at any given time. That limit is set to 20. Anything over 20 will be dropped.

- The PL/SQL Gateway does not support calling procedures with OUT parameters to be called from a Web interface. Doing this may result in ORA-6502 errors. The recommended approach is not to call any procedure that has OUT variables in it. However, the current architecture will let you modify a value as long as the modified value does not exceed the length that was passed in. Existing applications that encounter this problem need to be modified in one of the following ways:

  - Implement wrappers for procedures with OUT parameters so that such procedures are not invoked directly through a browser URL.

  - Create a local variable that gets assigned the value of the parameter being passed in, and is then used for all internal changes.

- The total number of name value pairs that can be passed to a PL/SQL procedure is 2000.

- mod_plsql limits the total number of parameters that can be passed to a single procedure to 2000.

- mod_plsql limits the size of a single parameter that can be passed to a procedure to 32000 bytes.

- It is not possible to use identical DAD locations in different virtual hosts.