Tuesday, 16 October 2012

Advanced Programming Techniques in APEX

Advanced Programming Techniques

This section provides information about advanced programming techniques including working with automatic data manipulation language, establishing database links, using collections, running background SQL, utilizing Web services, and managing user preferences.
This section contains the following topics:
See Also:
"Oracle Application Express APIs" and "Deploying an Application"

About DML Lockings

When automatic data manipulation language (DML) is used in Oracle Application Express to update or delete rows of a table, a transaction is initiated to first lock the row, verify if it has changed since it was displayed on the page, and then finally issue the actual UPDATE or DELETE statement for the row.
In some environments where locking of rows is prevalent, you may wish to control the DML operation and determine if the DML operation:
  • waits indefinitely
  • fails immediately
  • waits for a specified period of time
You can set the value of an application substitution string, an application item, or a page item named APEX_DML_LOCK_WAIT_TIME to control this operation. The following values are supported:
  • If null (the default), results in the same behavior as previous versions of Oracle Application Express, that is, wait indefinitely.
  • If 0, fail immediately if the row is locked by another database session.
  • If > 0 and the row is locked, wait for the specified number of seconds.
When set in an application, the value for APEX_DML_LOCK_WAIT_TIME applies to all UPDATE and DELETE DML operations using Automatic DML in the entire application. To control a specific Automatic DML process, update the value of APEX_DML_LOCK_WAIT_TIME before the Automatic DML process and reset it after the Automatic DML process. Note that this does not affect updates and deletes using tabular forms.

Accessing Data with Database Links

Because the Workspace home page runs in an Oracle database, you have access to all distributed Oracle database capabilities. Typically, you perform distributed database operations using database links.
A database link is a schema object in one database that enables you to access objects on another database. Once you have created the database link you can access the remote objects by appending @dblink to the table or view name where dblink is the Database Link Name you specify in the Create Database Object Wizard.
Note:
By default, the CREATE DATABASE LINK system privilege is not granted to a provisioned workspace or database user. To use this feature, a DBA or administrator needs to grant this specific privilege to the database user in the user's workspace. See "Creating Database Links" in Oracle Database Administrator's Guide
To create a database link:
  1. On the Workspace home page, click SQL Workshop and then Object Browser.
    Object Browser appears.
  2. Click Create.
  3. Select Database Link and click Next.
  4. Follow the on-screen instructions.
    Note that Database Link names must conform to Oracle naming conventions and cannot contain spaces, or start with a number or underscore.
To view an existing a database link:
  1. On the Workspace home page, click SQL Workshop and then Object Browser.
    Object Browser appears.
  2. Select the object type Database Links at the top of the page.
See Also:
"Managing Database Objects with Object Browser" and "Database Links" in Oracle Database Administrator's Guide

Sending Email from an Application

This section describes how to send email from an Oracle Application Express application.
Topics in this section include:
See Also:
"Managing Mail"
Tip:
If you are running Oracle Application Express with Oracle Database 11g Release 1 (11.1), you must enable network services in order to send outbound email. See "Enabling Network Services in Oracle Database 11g"

About Configuring Oracle Application Express to Send Email

Before you can send email from an Application Builder application, you must:
  1. Log in to Oracle Application Express Administration Services and configure the email settings on the Instance Settings page. See "Configuring Email Settings".
  2. If you are running Oracle Application Express with Oracle Database 11g release 1 (11.1), you need to enable outbound mail. In Oracle Database 11g release 1 (11.1), the ability to interact with network services is disabled by default. See "Enabling Network Services in Oracle Database 11g".
Tip:
You can configure Oracle Application Express to automatically email users their login credentials when a new workspace request has been approved. To learn more, see "Specifying a Provisioning Mode".

Sending Email from an Application

You can send an email from an Application Builder application by calling the PL/SQL package APEX_MAIL. This package is built on top of the Oracle supplied UTL_SMTP package. Because of this dependence, in order to use APEX_MAIL, the UTL_SMTP package must be installed and functioning.
See Also:
Oracle Database PL/SQL Packages and Types Reference for more information about the UTL_SMTP package and "APEX_MAIL"
APEX_MAIL contains two procedures for manually sending email:
  • Use the APEX_MAIL.SEND procedure to manually send an outbound email message from your application
  • Use APEX_MAIL.PUSH_QUEUE to deliver mail messages stored in APEX_MAIL_QUEUE
Oracle Application Express stores unsent email messages in a table named APEX_MAIL_QUEUE. You can deliver mail messages stored in this queue to the specified SMTP gateway by calling the procedure APEX_MAIL.PUSH_QUEUE.
Oracle Application Express logs successfully submitted messages in the table APEX_MAIL_LOG with the timestamp reflecting your server's local time.
The following UNIX/LINUX example demonstrates the use of the APEX_MAIL.PUSH_QUEUE procedure using a shell script.
SQLPLUS / <<EOF
APEX_MAIL.PUSH_QUEUE;
DISCONNECT
EXIT
EOF
See Also:
"APEX_MAIL" for information about using the APEX_MAIL and "Managing Mail"

Using Collections

Collections enable you to temporarily capture one or more nonscalar values. You can use collections to store rows and columns currently in session state so they can be accessed, manipulated, or processed during a user's specific session. You can think of a collection as a bucket in which you temporarily store and name rows of information.
The following are examples of when you might use collections:
  • When you are creating a data-entry wizard in which multiple rows of information first need to be collected within a logical transaction. You can use collections to temporarily store the contents of the multiple rows of information, before performing the final step in the wizard when both the physical and logical transactions are completed.
  • When your application includes an update page on which a user updates multiple detail rows on one page. The user can make many updates, apply these updates to a collection and then call a final process to apply the changes to the database.
  • When you are building a wizard where you are collecting an arbitrary number of attributes. At the end of the wizard, the user then performs a task that takes the information temporarily stored in the collection and applies it to the database.
Topics in this section include:

About the APEX_COLLECTION API

Every collection contains a named list of data elements (or members) which can have up to 50 character attributes (VARCHAR2(4000)), and one large character attribute (CLOB). You insert, update, and delete collection information using the PL/SQL API APEX_COLLECTION.

About Collection Naming

When you create a new collection, you must give it a name that cannot exceed 255 characters. Note that collection names are not case-sensitive and will be converted to uppercase.
Once the collection is named, you can access the values in the collection by running a SQL query against the view APEX_COLLECTIONS.
See Also:
"Accessing a Collection"

Creating a Collection

Every collection contains a named list of data elements (or members) which can have up to 50 character attributes (VARCHAR2(4000)), and one large character attribute (CLOB). You use the following methods to create a collection:
  • CREATE_COLLECTION
  • CREATE_OR_TRUNCATE_COLLECTION
  • CREATE_COLLECTION_FROM_QUERY
  • APEX_COLLECTION.CREATE_COLLECTION_FROM_QUERY_B
The CREATE_COLLECTION method raises an exception if the named collection already exists, for example:
APEX_COLLECTION.CREATE_COLLECTION(
    p_collection_name => collection name );
The CREATE_OR_TRUNCATE_COLLECTION method creates a new collection if the named collection does not exist. If the named collection already exists, this method truncates it. Truncating a collection empties it, but leaves it in place, for example:
APEX_COLLECTION.CREATE_OR_TRUNCATE_COLLECTION(
    p_collection_name => collection name,
    p_generate_md5    => YES or NO );
The CREATE_COLLECTION_FROM_QUERY method creates a collection and then populates it with the results of a specified query, for example:
APEX_COLLECTION.CREATE_COLLECTION_FROM_QUERY(
    p_collection_name => collection name,
    p_query           => your query );
    p_generate_md5    => YES or NO );
The CREATE_COLLECTION_FROM_QUERY_B method also creates a collection and then populates it with the results of a specified query, for example:
APEX_COLLECTION.CREATE_COLLECTION_FROM_QUERY_B(
    p_collection_name => collection name,
    p_query           => your query );
The CREATE_COLLECTION_FROM_QUERY_B method offers significantly faster performance than the CREATE_COLLECTION_FROM_QUERY method by performing bulk SQL operations, but has the following limitations:
  • No column value in the select list of the query can be more than 2,000 bytes. If a row is encountered that has a column value of more than 2,000 bytes, an error will be raised during execution.
  • The MD5 checksum will not be computed for any members in the collection.

About the Parameter p_generate_md5

Use the p_generate_md5 flag to specify if the message digest of the data of the collection member should be computed. By default, this flag is set to NO. Use this parameter to check the MD5 of the collection member (that is, compare it with another member or see if a member has changed).
See Also:
"Determining Collection Status" for information about using the GET_MEMBER_MD5 function

Truncating a Collection

If you truncate a collection, you remove all members from the specified collection, but the named collection remains in place, for example:
APEX_COLLECTION.TRUNCATE_COLLECTION(
    p_collection_name => collection name );

Accessing a Collection

You can access the members of a collection by querying the database view APEX_COLLECTIONS. The APEX_COLLECTIONS view has the following definition:
COLLECTION_NAME   NOT NULL VARCHAR2(255)
SEQ_ID            NOT NULL NUMBER 
C001                       VARCHAR2(4000)
C002                       VARCHAR2(4000)
C003                       VARCHAR2(4000)   
C004                       VARCHAR2(4000)   
C005                       VARCHAR2(4000)  
...
C050                       VARCHAR2(4000)
CLOB001                    CLOB   
MD5_ORIGINAL               VARCHAR2(4000)
Use the APEX_COLLECTIONS view in an application just as you would use any other table or view in an application, for example:
SELECT c001, c002, c003
   FROM APEX_collections
 WHERE collection_name = 'FIREARMS'

Deleting a Collection

If you delete a collection, you delete the collection and all of its members, for example:
APEX_COLLECTION.DELETE_COLLECTION (
    p_collection_name => collection name );
Be aware that if you do not delete a collection, it will eventually be deleted when the session is purged. For example:

Deleting All Collections for the Current Application

Use the DELETE_ALL_COLLECTIONS method to delete all collections defined in the current application, for example:
APEX_COLLECTION.DELETE_ALL_COLLECTIONS;

Deleting All Collections in the Current Session

Use the DELETE_ALL_COLLECTIONS_SESSION method to delete all collections defined in the current session., for example:
APEX_COLLECTION.DELETE_ALL_COLLECTIONS_SESSION;

Adding Members to a Collection

When data elements (or members) are added to a collection, they are assigned a unique sequence ID. As you add members to a collection, the sequence ID will change in increments of 1, with the newest members having the largest ID.
You add new members to a collection using the ADD_MEMBER function. Calling this function returns the sequence ID of the newly added member. The following example demonstrates how to use the ADD_MEMBER function.
APEX_COLLECTION.ADD_MEMBER(
    p_collection_name => collection name,
    p_c001          => [member attribute 1],
    p_c002          => [member attribute 2],
    p_c003          => [member attribute 3],
    p_c004          => [member attribute 4],
    p_c005          => [member attribute 5],
    p_c006          => [member attribute 6],
    p_c007          => [member attribute 7],
  ...
    p_c050          => [member attribute 50]);
    p_clob001       => [CLOB member attribute 1],
    p_generate_md5  => YES or NO);
You can also add new members (or an array of members) to a collection using the ADD_MEMBERS method, for example:
APEX_COLLECTION.ADD_MEMBERS(
    p_collection_name => collection name,
    p_c001          => member attribute array 1,
    p_c002          => member attribute array 2,
    p_c003          => member attribute array 3,
    p_c004          => member attribute array 4,
    p_c005          => member attribute array 5,
    p_c006          => member attribute array 6,
    p_c007          => member attribute array 7,
    ...
    p_c050          => member attribute array 50);
    p_generate_md5  => YES or NO);
This method raises an error if the specified collection does not exist with the specified name of the current user and in the same session. Also any attribute exceeding 4,000 characters will be truncated to 4,000 characters. The number of members added is based on the number of elements in the first array.

About the Parameters p_generate_md5 and p_clob001

Use the p_generate_md5 flag to specify if the message digest of the data of the collection member should be computed. By default, this flag is set to NO. Use this parameter to check the MD5 of the collection member (that is, compare it with another member or see if a member has changed).
Use p_clob001 for collection member attributes which exceed 4,000 characters.
See Also:
"Determining Collection Status" for information about using the function GET_MEMBER_MD5

Updating Collection Members

You can update collection members by calling the UPDATE_MEMBER procedure and referencing the desired collection member by its sequence ID, for example:
APEX_COLLECTION.UPDATE_MEMBER (
    p_collection_name => collection name,
    p_seq             => member sequence number,
    p_c001            => member attribute 1,
    p_c002            => member attribute 2,
    p_c003            => member attribute 3,
    p_c004            => member attribute 4,
    p_c005            => member attribute 5,
    p_c006            => member attribute 6,
    p_c007            => member attribute 7,
    ...
    p_c050            => member attribute 50);
    p_clob001         => [CLOB member attribute 1],
The UPDATE_MEMBER procedure replaces an entire collection member, not individual member attributes. This procedure causes an error if the named collection does not exist. For example:
Use the p_clob001 parameter for collection member attributes which exceed 4,000 characters.
If you want to update a single attribute of a collection member, use the UPDATE_MEMBER_ATTRIBUTE procedure, for example:
APEX_COLLECTION.UPDATE_MEMBER_ATTRIBUTE(
    p_collection_name       => collection_name,
    p_seq                   => member sequence number,
    p_attr_number           => member attribute number,
    p_attr_value            => member attribute value )


APEX_COLLECTION.UPDATE_MEMBER_ATTRIBUTE(
    p_collection_name        => collection_name,
    p_seq                    => member sequence number,
    p_clob_number            => CLOB member attribute number,
    p_clob_value             => CLOB member attribute value );
Calling the UPDATE_MEMBER_ATTRIBUTE procedure causes an error if the named collection does not exist.
Note that the only valid value for the p_clob_number parameter is 1.

Deleting Collection Members

You can delete a collection member by calling the DELETE_MEMBER procedure and referencing the desired collection member by its sequence ID, for example:
APEX_COLLECTION.DELETE_MEMBER(
    p_collection_name => collection name,
    p_seq             => member sequence number);
Note that this procedure leaves a gap in the sequence IDs in the specified collection. In addition, calling this procedure causes an error if the named collection does not exist.
You can also delete all members from a collection by when an attribute matches a specific value, for example:
APEX_COLLECTION.DELETE_MEMBERS(
    p_collection_name => collection name,
    p_attr_number     => number of attribute used to match for the specified
                         attribute value for deletion, 
    p_attr_value      => attribute value of the member attribute used to 
                         match for deletion);
Note that the DELETE_MEMBER procedure also leaves a gap in the sequence IDs in the specified collection. This procedure causes an error if:
  • The named collection does not exist.
  • The specified attribute number is outside the range of 1 to 50, or not valid.
If the supplied attribute value is null, then all members of the named collection will deleted.

Determining Collection Status

The p_generate_md5 parameter determines if the MD5 message digests are computed for each member of a collection. The collection status flag is set to FALSE immediately after you create a collection. If any operations are performed on the collection (such as add, update, truncate, and so on), this flag is set to TRUE.
You can reset this flag manually by calling RESET_COLLECTION_CHANGED, for example:
APEX_COLLECTION.RESET_COLLECTION_CHANGED (
    p_collection_name => collection name)
Once this flag has been reset, you can determine if a collection has changed by calling COLLECTION_HAS_CHANGED, for example:
l_changed := APEX_COLLECTION.COLLECTION_HAS_CHANGED(
  p_collection_name => collection_name);
When you add a new member to a collection, an MD5 message digest is computed against all 50 attributes and the CLOB attribute if the p_generated_md5 parameter is set to YES. You can access this value from the MD5_ORIGINAL column of the view APEX_COLLECTION. You can access the MD5 message digest for the current value of a specified collection member by using the function GET_MEMBER_MD5. For example:
APEX_COLLECTION.GET_MEMBER_MD5 (
    p_collection_name => collection name,
    p_seq             => member sequence number );
    RETURN VARCHAR2;

Merging Collections

You can merge members of a collection with values passed in a set of arrays. By using the p_init_query argument, you can create a collection from the supplied query, for example:
APEX_COLLECTION.MERGE_MEMBERS
p_collection_name => collection_name
Note that if the collection exists, the following occurs:
  • Rows in the collection not in the arrays will be deleted.
  • Rows in the collection and in the arrays will be updated.
  • Rows in the array and not in the collection will be inserted.
Any attribute value exceeding 4,000 characters will be truncated to 4,000 characters. Table 13-1 describes the available arguments you can use when merging collections.
Table 13-1 Available Arguments for Merging Collections
Argument Description
p_c001
 Array of first attribute values to be merged. Maximum length is 4,000 characters. If the maximum length is greater, it will be truncated to 4,000 characters.
The count of elements in the P_C001 PL/SQL table is used as the total number of items across all PL/SQL tables. For example, if P_C001.count = 2 and P_C002.count = 10, only 2 members will be merged. Note that if P_C001 is null, an application error will be raised.
p_c0xx
 Attribute of XX attributes values to be merged. Maximum length is 4,000 characters. If the maximum length is greater, it will be truncated to 4,000 characters.
p_collection_name
 Name of the collection.
See Also: "About Collection Naming"
p_null_index
 Use this argument to identify rows the merge function should ignore. This argument identifies an row as null. Null rows are automatically removed from the collection.
p_null_value
 Use this argument in conjunction with the p_null_index. Identifies the null value. If used this value cannot be null. A typical value for this argument is 0.
p_init_query
 Use the query defined by this argument to create a collection if the collection does not exist.

Managing Collections

You can use the following utilities to manage collections.
Topics in this section include:

Obtaining a Member Count

Use COLLECTION_MEMBER_COUNT to return the total count of all members in a collection. Note that this count does not indicate the highest sequence in the collection, for example:
l_count := APEX_COLLECTION.COLLECTION_MEMBER_COUNT (
  p_collection_name => collection name );

Resequencing a Collection

Use RESEQUENCE_COLLECTION to resequence a collection to remove any gaps in sequence IDs while maintaining the same element order, for example:
APEX_COLLECTION.RESEQUENCE_COLLECTION (
   p_collection_name => collection name )

Verifying Whether a Collection Exists

Use COLLECTION_EXISTS to determine if a collection exists, for example:
l_exists := APEX_COLLECTION.COLLECTION_EXISTS  (
  p_collection_name => collection name );

Adjusting a Member Sequence ID

You can adjust the sequence ID of a specific member within a collection by moving the ID up or down. When you adjust a sequence ID, the specified ID is exchanged with another ID. For example, if you were to move the ID 2 up, 2 becomes 3, and 3 would become 2.
Use MOVE_MEMBER_UP to adjust a member sequence ID up by one. Alternately, use MOVE_MEMBER_DOWN to adjust a member sequence ID down by one, for example:
APEX_COLLECTION.MOVE_MEMBER_DOWN(
    p_collection_name => collection name,
    p_seq             => member sequence number);
Note that while using either of these methods an application error displays:
  • If the named collection does not exist for the current user in the current session
  • If the member specified by the p_seq sequence ID does not exist
However, an application error will not be returned if the specified member already has the highest or lowest sequence ID in the collection (depending on if you are calling MOVE_MEMBER_UP or MOVE_MEMBER_DOWN).

Sorting Collection Members

Use the SORT_MEMBERS method to reorder members of a collection by the column number. This method sorts the collection by a particular column number and also reassigns the sequence IDs for each member to remove gaps, for example:
APEX_COLLECTION.SORT_MEMBERS(
    p_collection_name       => collection name,
    p_sort_on_column_number => column number to sort by);

Clearing Collection Session State

Clearing the session state of a collection removes the collection members. A shopping cart is a good example of when you might need to clear collection session state. When a user requests to empty the shopping cart and start again, you need to clear the session state for a collection. You can remove session state of a collection by calling the CREATE_OR_TRUNCATE_COLLECTION method or by using f?p syntax.
Calling the CREATE_OR_TRUNCATE_COLLECTION method deletes the existing collection and then recreates it, for example:
APEX_COLLECTION.CREATE_OR_TRUNCATE_COLLECTION(
    p_collection_name       => collection name,
You can also use the sixth f?p syntax argument to clear session state, for example:
f?p=App:Page:Session::NO:1,2,3,collection name
See Also:
"Understanding URL Syntax"

Creating Custom Activity Reports Using APEX_ACTIVITY_LOG

The APEX_ACTIVITY_LOG view records all activity in a workspace, including developer activity and application run-time activity. You can use APEX_ACTIVITY_LOG to view to query all activity for the current workspace. For example, you can use this view to develop monitoring reports within a specific application to provide real-time performance statistics.
Table 13-2 describes the columns in the APEX_ACTIVITY_LOG view.
Table 13-2 Columns in APEX_ACTIVITY_LOG
Column Type Description
time_stamp
 DATE
 Date and time that activity was logged at the end of the page view.
component_type
 VARCHAR2(255)
 Reserved for future use.
component_name
 VARCHAR2(255)
 Reserved for future use.
component_attribute
 VARCHAR2(4000)
 Title of page.
information
 VARCHAR2(4000)
 Reserved for future use.
elap
 NUMBER
 Elapsed time of page view in seconds.
num_rows
 NUMBER
 Number of rows processed on page.
userid
 VARCHAR2(255)
 User ID performing page view.
ip_address
 VARCHAR2(4000)
 IP address of client.
user_agent
 VARCHAR2(4000)
 Web browser user agent of client.
flow_id
 NUMBER
 Application ID.
step_id
 NUMBER
 Page number.
session_id
 NUMBER
 Oracle Application Express session identifier.
sqlerrm
 VARCHAR2(4000)
 SQL Error message.
sqlerrm_component_type
 VARCHAR2(255)
 Reserved for future use.
sqlerrm_component_name
 VARCHAR2(255)
 Reserved for future use.

To conserve space in the activity log, only the first log entry of each unique session will contain the IP address and Web browser user agent.
The following example demonstrates how to create a report that displays the total number of page views and the average page view time in the past 24 hours for application 9529, and grouped by userid:
SELECT COUNT(*), AVG(elap), userid
    FROM APEX_ACTIVITY_LOG
 WHERE time_stamp > (SYSDATE-1)
   AND flow_id = 9529
GROUP BY userid
Keep in mind that logging of activity in an Application Express instance is rotated between two different log tables. Because of this, logging information is only as current as the oldest available entry in the logs. If you wish to persist your application specific log information for all time, you need to either copy the log information into your own application table or implement logging directly in your application.
See Also:
"Name" for information on enabling logging on the Edit Definition page

Running Background PL/SQL

You can use the APEX_PLSQL_JOB package to run PL/SQL code in the background of your application. This is an effective approach for managing long running operations that do not need to complete for a user to continue working with your application.
Topics in this section include:

Understanding the APEX_PLSQL_JOB Package

APEX_PLSQL_JOB is a wrapper package around DBMS_JOB functionality offered in the Oracle database. Note that the APEX_PLSQL_JOB package only exposes that functionality which is necessary to run PL/SQL in the background. The following is a description of the APEX_PLSQL_JOB package:
SQL> DESC APEX_PLSQL_JOB
FUNCTION JOBS_ARE_ENABLED RETURNS BOOLEAN
PROCEDURE PURGE_PROCESS
 Argument Name                  Type                    In/Out Default?
 ------------------------------ ----------------------- ------ --------
 P_JOB                          NUMBER                  IN
FUNCTION SUBMIT_PROCESS RETURNS NUMBER
 Argument Name                  Type                    In/Out Default?
 ------------------------------ ----------------------- ------ --------
 P_SQL                          VARCHAR2                IN
 P_WHEN                         VARCHAR2                IN     DEFAULT
 P_STATUS                       VARCHAR2                IN     DEFAULT
FUNCTION TIME_ELAPSED RETURNS NUMBER
 Argument Name                  Type                    In/Out Default?
 ------------------------------ ----------------------- ------ --------
 P_JOB                          NUMBER                  IN
PROCEDURE UPDATE_JOB_STATUS
 Argument Name                  Type                    In/Out Default?
 ------------------------------ ----------------------- ------ --------
 P_JOB                          NUMBER                  IN
 P_STATUS                       VARCHAR2                IN
 P_DESC
Table 13-1 describes the functions available in the APEX_PLSQL_JOB package.
Table 13-3 APEX_PLSQL_JOB Package: Available Functions
Function or Procedure Description
SUBMIT_PROCESS
 Use this procedure to submit background PL/SQL. This procedure returns a unique job number. Because you can use this job number as a reference point for other procedures and functions in this package, it may be useful to store it in your own schema.
UPDATE_JOB_STATUS
 Call this procedure to update the status of the currently running job. This procedure is most effective when called from the submitted PL/SQL.
TIME_ELAPSED
 Use this function to determine how much time has elapsed since the job was submitted.
JOBS_ARE_ENABLED
 Call this function to determine whether or not the database is currently in a mode that supports submitting jobs to the APEX_PLSQL_JOB package.
PURGE_PROCESS
 Call this procedure to clean up submitted jobs. Submitted jobs stay in the APEX_PLSQL_JOBS view until either Oracle Application Express cleans out those records, or you call PURGE_PROCESS to manually remove them.

You can view all jobs submitted to the APEX_PLSQL_JOB package using the APEX_PLSQL_JOBS view. The following is the description of APEX_PLSQL_JOBS view:
SQL> DESCRIBE APEX_PLSQL_JOBS
 Name                              Null?    Type
 --------------------------------- -------- ----------------------------
 ID                                         NUMBER
 JOB                                        NUMBER
 FLOW_ID                                    NUMBER
 OWNER                                      VARCHAR2(30)
 ENDUSER                                    VARCHAR2(30)
 CREATED                                    DATE
 MODIFIED                                   DATE
 STATUS                                     VARCHAR2(100)
 SYSTEM_STATUS                              VARCHAR2(4000)
 SYSTEM_MODIFIED                            DATE
 SECURITY_GROUP_ID                          NUMBER
Table 13-4 describes the columns available in APEX_PLSQL_JOBS view.
Table 13-4 APEX_PLSQL_JOBS View Columns
Name Description
ID
 A unique identifier for each row.
JOB
 The job number assigned to each submitted PL/SQL job. The APEX_PLSQL_JOB.SUBMIT_PROCESS function returns this value. This is also the value you pass into other procedures and functions in the APEX_PLSQL_JOB package.
FLOW_ID
 The application from which this job was submitted.
OWNER
 The database schema that owns the application. This identifies what schema will parse this code when DBMS_JOB runs it.
ENDUSER
 The end user (that is, who logged into the application) that caused this process to be submitted.
CREATED
 The date when the job was submitted.
MODIFIED
 The date when the status was modified.
STATUS
 The user-defined status for this job. Calling APEX_PLSQL_JOB.UPDATE_JOB_STATUS updates this column.
SYSTEM_STATUS
 The system defined status for this job.
SYSTEM_MODIFIED
 The date when the system status was modified.
SECURITY_GROUP_ID
 The unique ID assigned to your workspace. Developers can only see jobs submitted from their own workspace.

About System Status Updates

Submitted jobs can contain any of the following system status settings:
  • SUBMITTED indicates the job has been submitted, but has not yet started. The DBMS_JOB does not guarantee immediate starting of jobs.
  • IN PROGRESS indicates that the DBMS_JOB has started the process.
  • COMPLETED indicates the job has finished.
  • BROKEN (sqlcode) sqlerrm indicates there was a problem in your job that resulted in an error. The SQL code and SQL error message for the error should be included in the system status. Review this information to determine what went wrong.

Using a Process to Implement Background PL/SQL

The following example runs a PL/SQL job in the background for testing and explanation:
001  BEGIN
002    FOR i IN 1 .. 100 LOOP
003      INSERT INTO emp(a,b) VALUES (:APP_JOB,i);
004      IF MOD(i,10) = 0 THEN
005        APEX_PLSQL_JOB.UPDATE_JOB_STATUS(
006          P_JOB     => :APP_JOB,
007          P_STATUS  => i || 'rows inserted');
008      END IF;
009      APEX_UTIL.PAUSE(2);
010    END LOOP;
011  END;
In this example, note that:
  • Lines 002 to 010 run a loop that inserts 100 records into the emp table.
  • APP_JOB is referenced as a bind variable inside the VALUES clause of the INSERT, and specified as the P_JOB parameter value in the call to UPDATE_JOB_STATUS.
  • APP_JOB represents the job number which will be assigned to this process as it is submitted to APEX_PLSQL_JOB. By specifying this reserved item inside your process code, it will be replaced for you at execution time with the actual job number.
  • Note that this example calls to UPDATE_JOB_STATUS every ten records, INSIDE the block of code. Normally, Oracle transaction rules dictate updates made inside code blocks will not be seen until the entire transaction is committed. The APEX_PLSQL_JOB.UPDATE_JOB_STATUS procedure, however, has been implemented in such a way that the update will happen regardless of whether or not the job succeeds or fails. This last point is important for two reasons:
    1. Even if your status shows "100 rows inserted," it does not mean the entire operation was successful. If an error occurred at the time the block of code tried to commit, the user_status column of APEX_PLSQL_JOBS would not be affected because status updates are committed separately.
    2. Updates are performed autonomously. You can view the job status before the job has completed. This gives you the ability to display status text about ongoing operations in the background as they are happening.

Implementing Web Services

Web services enable applications to interact with one another over the Web in a platform-neutral, language independent environment. In a typical Web services scenario, a business application sends a request to a service at a given URL by using the protocol over HTTP. The service receives the request, processes it, and returns a response. You can incorporate calls with external Web services in applications developed in Application Builder.
Web services are based on Simple Object Access Protocol (SOAP). SOAP is a World Wide Web Consortium (W3C) standard protocol for sending and receiving requests and responses across the Internet. SOAP messages can be sent back and forth between a service provider and a service user in SOAP envelopes.
SOAP offers two primary advantages:
  • SOAP is based on XML, and therefore easy to use.
  • SOAP messages are not blocked by firewalls because this protocol uses simple transport protocols, such as HTTP.
Tip:
If you are running Oracle Application Express with Oracle Database 11g Release 1 (11.1), you must enable network services in order to use Web services. See "Enabling Network Services in Oracle Database 11g"
Topics in this section include:
Note:
The SOAP 1.1 specification is a W3C note. (The W3C XML Protocol Working Group has been formed to create a standard that will supersede SOAP.) For information about Simple Object Access Protocol (SOAP) 1.1 see:
http://www.w3.org/TR/SOAP/

Understanding Web Service References

To utilize Web services in Oracle Application Express, you create a Web service reference using a wizard. Web service references can be based either on a Web Services Description Language (WSDL) document or created manually by supplying information about the service.
When you create a Web service reference based on a WSDL, the wizard analyzes the WSDL and collects all the necessary information to create a valid SOAP message, including:
  • The URL used to post the SOAP request over HTTP(S)
  • A Universal Resource Identifier (URI) identifying the SOAP HTTP request
  • Operations of the Web Service
  • Input parameters for each operation
  • Output parameters for each operation
When you create a Web service reference manually, you supply the necessary information to create a valid SOAP request, including:
  • The URL used to post the SOAP request over HTTP(S)
  • A Universal Resource Identifier (URI) identifying the SOAP HTTP request
  • The SOAP envelope for the request, including any item substitutions
  • Optionally the name of a collection to store the response from the Web service

Accessing the Web Service References Page

You manage Web service references on the Web Service References page.
To access the Web Service References page:
  1. On the Workspace home page, click the Application Builder icon.
  2. Select an application.
    Application Builder appears.
  3. Click Shared Components.
    The Shared Components page appears.
  4. Under Logic, click Web Service References.
    The Web Service References page appears.

Specifying an Application Proxy Server Address

If your environment requires a proxy server to access the Internet, you must specify a proxy server address on the Application Attributes page before you can create a Web service reference.
To specify a proxy address for an application:
  1. On the Workspace home page, click the Application Builder icon.
  2. Select an application.
    Application home page appears.
  3. Click Shared Components.
  4. Under Application, click Definition.
  5. Under Name, enter the proxy server in the Proxy Server field.
  6. Click Apply Changes.

Working with SSL Enabled Web Services

Secure Sockets Layer (SSL) is an industry standard protocol that uses RSA public key cryptography in conjunction with symmetric key cryptography to provide authentication, encryption, and data integrity.
If the Web service that you need to interact with is SSL-enabled (that is, https displays in the URL to the Web service), you must create a wallet. A wallet is a password-protected container that stores authentication and signing credentials (including private keys, certificates, and trusted certificates) needed by SSL.
See Also:
"Configuring Wallet Information"

Creating a Web Service Reference Based on a WSDL

When you create a Web service reference based on a WSDL, you need to decide how to locate the WSDL. You can locate a WSDL in two ways:
  • By searching a Universal Description, Discovery and Integration (UDDI) registry
  • by entering the URL to the WSDL document
A UDDI registry is a directory where businesses register their Web services.
Topics in this section include:

Creating a Web Service Reference by Searching a UDDI Registry

To create a new Web service by searching a UDDI registry:
  1. Navigate to the Web Service References page. See "Accessing the Web Service References Page".
  2. Click Create.
  3. When prompted to search a UDDI registry to find a WSDL, click Yes.
  4. For UDDI Location you can either:
    • Enter a URL endpoint to a UDDI registry.
    • Click the List icon and select a UDDI registry.
  5. For Search, specify the following:
    1. Search Type - Specify whether to search for a business name or a service name. You cannot search for both.
    2. Name - Enter the business name or service name to search for. Use the percent (%) symbol as a wildcard character.
    3. Optionally indicate if the search should be case-sensitive or an exact match.
    4. Click Search.
    5. When the search results appear, make a selection and click Next.
    A summary page appears describing the selected Web service.
  6. Review your selection and click Next to continue.
    The URL to the WSDL document displays in the WSDL Location field.
  7. Click Finish.
The Web service reference is added to the Web Service References Repository.

Creating a Web Service Reference by Specifying a WSDL Document

To create a new Web service by specifying a URL to a specific WSDL document:
  1. Navigate to the Web Service References page. See "Accessing the Web Service References Page".
  2. Click Create.
  3. When prompted to search a UDDI registry to find a WSDL, click No.
  4. In WSDL Location, enter the URL to the WSDL document.
  5. Click Finish.
The Web service reference is added to the Web Service References Repository.

Creating a Web Service Manually

To create a new Web service reference manually:
  1. Navigate to the Web Service References page. See "Accessing the Web Service References Page".
  2. Click Create.
  3. When prompted to search a UDDI registry to find a WSDL, click No.
  4. From the Tasks list, click Create Web Service Reference Manually.
    The Create/Edit Web Service page appears.
  5. In Name, enter a name to identify the reference.
  6. Under Service Description:
    1. URL - Enter the URL endpoint of the Web service.
    2. Action - Enter the action of the Web service (optional).
    3. Proxy - Enter a proxy if you wish to override the application proxy for this service.
    4. Basic Authentication - Choose whether the Web service requires authentication. Select Yes or No.
  7. For SOAP Envelop, enter the SOAP envelope for this request.
  8. For Store Response in Collection, enter the name of a collection to store the response (optional).
  9. Click Create.
The Web service reference is added to the Web Service References Repository.

Using the Web Service Reference Repository

Web service references are stored in the Web Service Reference Repository.
To access the Web Service References Repository:
  1. On the Workspace home page, click the Application Builder icon.
  2. Select an application.
    Application Builder appears.
  3. Click Shared Components.
    The Shared Components page appears.
  4. Under Logic, click Web Service References.
    The Web Service Reference page appears.
    Use the Navigation bar at the top of the page to search for Web service references or change the page display. Available options include:
    • Web Service Reference - Enter a case insensitive query for the reference name and click Go. To view all Web service references, leave the field blank and click Go.
    • View - Select a display mode and click Go. Available options include:
      • Icons (the default) displays each Web service reference as a large icon. To edit a Web service reference, click the appropriate icon.
      • Details displays each Web service reference as a line in a report.
  5. Select Details from the View list and click Go.
  6. In Details view you can:
    • Edit a reference by clicking the reference name.
    • Test a reference by clicking the Run icon.
    • View details about a reference by clicking the View icon. Note that this option is not available for manually created Web service references.

Testing a Web Service Reference Created from a WSDL

After you have created a Web service reference, you can test it on the Test Web Service Reference page.
To test a Web service reference:
  1. Navigate to the Web Service References page. See "Accessing the Web Service References Page".
  2. From View, select Details.
  3. Click the Run icon adjacent to the Web Service reference name.
    The Test Web Service Reference page appears. The Web service name and URL endpoint display at the top of the page.
  4. From Operation, select an operation (that is, the method to be executed).
  5. Under Input Parameters, enter the appropriate value.
  6. Click Test.
    The message request and response appear at the bottom of the page.

Testing a Web Service Reference Created Manually

After you have created a Web service reference, you can test it on the Test Web Service Reference page.
To test a Web service reference:
  1. Navigate to the Web Service References page. See "Accessing the Web Service References Page".
  2. From View, select Details.
  3. Click the Run icon adjacent to the Web Service reference name.
    The Test Web Service Reference page appears. The Web service name and URL endpoint display at the top of the page.
  4. If required, enter the username and password under Basic Authentication.
  5. In SOAP Envelope text area, optionally edit the SOAP request envelope.
  6. Click Test.
    The message request and response appear at the bottom of the page.

Creating an Input Form and Report on a Web Service

The Create Form and Report on Web Service Wizard creates an input form, a submit button, and a report for displaying results. You can execute this wizard directly after creating the Web service reference from a WSDL, or by adding a new page.
Use this wizard when you expect a nonscalar result from the Web service. The Amazon Web service is a good example. This Web service returns many results based on the search criteria entered in an input form.

Creating a Form and Report After Creating a Reference

To create a form and report after creating a Web Service Reference:
  1. Create the Web service reference. See "Creating a Web Service Reference Based on a WSDL".
  2. After the Web service reference has been added, select Create Form and Report on Web Service.
  3. For Choose Service and Operation:
    1. Web Service Reference - Select the Web service reference.
    2. Operation - Select the method to be executed.
  4. For Page and Region Attributes, review the displayed attributes. If the page you specify does not exist, the wizard creates the page for you.
  5. For Input Items:
    1. Identify which items to add to the form. To include an item, select Yes in the Create column. Otherwise, select No.
    2. If necessary, edit the item label.
  6. If applicable, specify the Item Names and Item Labels for basic authentication. Note that this step only appears if basic authentication was specified for this Web service reference when it was created.
  7. For Window Service Results:
    1. Temporary Result Set Name - Enter a name for the collection that stores the Web service result.
    2. Result Tree to Report On - Select the portion of the resulting XML document that contains the information you want to include in the report.
  8. For Result Parameters to Display, select the parameters to be included in the report.
  9. Click Finish.

Creating a Form and Report by Adding a New Page

If you have an existing Web service reference, you can create an input form and report by adding a new page.
To create a form and report by adding a new page:
  1. Create the Web service reference. See "Creating a Web Service Reference Based on a WSDL".
  2. Create a new page. See "Managing Pages in an Application".
    In the Create Page Wizard:
    1. Select Form.
    2. Select Form and Report on Web Service.
  3. For Choose Service and Operation:
    1. Web Service Reference - Select the Web service reference.
    2. Operation - Select the method to be executed.
  4. For Page and Region Attributes, review the page and region attributes. If the page you specify does not exist, the wizard creates the page for you.
  5. For Input Items:
    1. Identify which items to add to the form. To include an item, select Yes in the Create column. Otherwise, select No.
    2. If necessary, edit the item label.
  6. If applicable, specify the Item Names and Item Labels for basic authentication. Note that this step only appears if basic authentication was specified for this Web service reference when it was created.
  7. Follow the on-screen instructions.
  8. Click Finish.

Creating a Form on a Web Service

The Create Form on Web Service Wizard creates a form and a submit button. You can execute this wizard after creating the Web service reference from a WSDL, or from the Page Definition.
Use this wizard when you expect a scalar result from the Web service. A Web service that looks up a stock price is a good example because the input is a stock symbol and the output is the scalar value price.

Creating a Form After Creating a Reference

To create a form after creating a Web Service Reference:
  1. Create the Web service reference. See "Creating a Web Service Reference Based on a WSDL".
  2. After the Web service references has been added, select Create Form on Web Service.
  3. For Choose Service and Operation:
    1. Web Service Reference - Select the Web service reference.
    2. Operation - Select the method to be executed.
  4. For Identify Page and Region Attributes, review the page and region attributes. If the page you specify does not exist, the wizard creates the page for you.
  5. For Items for Input Parameters:
    1. Identify which items to add. To include an item, select Yes in the Create column. Otherwise, select No.
    2. If necessary, edit the item label.
  6. For Items for Output Parameters:
    1. Identify which items need to be added. To include an item, select Yes in the Create column. Otherwise, select No.
    2. If necessary, edit the item label.
  7. If applicable, specify the Item Names and Item Labels for basic authentication.
    Note that this step only appears if basic authentication was specified for this Web service reference when it was created.
  8. Click Finish.

Creating a Form by Adding a New Page

If you have an existing Web service reference created from a WSDL, you can create form by adding a new page.
To create a form by adding a new page:
  1. Create the Web service reference. See "Creating a Web Service Reference Based on a WSDL".
  2. Create a new page. See "Managing Pages in an Application".
    In the Create Page Wizard:
    1. Select Form.
    2. Select Form on Web Service.
  3. For Web Service Reference and Operation, select the Web service reference and operation (that is, the method to be executed).
  4. For Identify Page and Region Attributes, review the page and region attributes. If the page you specify does not exist, the wizard creates the page for you.
  5. For Items for Input Parameters:
    1. Identify which items need to be added. To include an item, select Yes in the Create column. Otherwise, select No.
    2. If applicable, specify the Item Names and Item Labels for basic authentication.
      Note that this step only appears if basic authentication was specified for this Web service reference when it was created.
  6. For Items for Output Parameters:
    1. Identify which items need to be added. To include an item, select Yes in the Create column. Otherwise, select No.
    2. If necessary, edit the item label.
  7. Click Finish.

Invoking a Web Service as a Process

You can also implement a Web service as a process on the page. Running the process submits the request to the service provider. You can then display the request results in report.
To invoke a Web service as a process:
  1. Create a new page. See "Managing Pages in an Application".
    In the Create Page Wizard:
    1. Select Blank Page.
    2. When prompted to use tabs, select No.
  2. Navigate to the Page Definition. See "Accessing a Page Definition".
  3. Under Page Rendering, Processes, click the Create icon.
    The Create Page Processes Wizard appears.
  4. From the process category, select Web Services.
  5. Specify a process name, sequence, and processing point.
  6. Select the Web service reference.
    If the Web reference was created from a WSDL, perform the following additional steps.
  7. Select the Web service reference and operation (that is, the method to be executed).
  8. Define the process. You can store the results in a collection or in items on the page by selecting options under Web Service Output Parameters.
    1. To store the results in a collection:
      • For Store Result in, select Collection.
      • Enter a name for the collection in the value field.
    2. To store the results in items on the page:
      • For Store Result in, select Items.
      • Enter the appropriate items value in the fields provided.
  9. Click Create Process.

Displaying Web Service Results in a Report

To create a report in which to display Web Service request results:
  1. Navigate to the Page Definition. See "Accessing a Page Definition".
  2. Under Regions, click the Create icon.
    The Create Region Wizard appears.
  3. For the region type, select Report.
  4. For the report implementation, select Report on collection containing Web service result.On Identify Region Attributes, enter a region title and optionally edit the region attributes.
  5. Choose whether the Web reference was created manually or from a WSDL.
  6. If the Web service reference was created from a WSDL:
    1. For Web Service Reference and Operation, select a Web service reference and an operation (that is, the method to be executed).
    2. For Result Tree to Report On, select the portion of the resulting XML document that contains the information you want to include in the report.
    3. For Result Parameters:
      • In Temporary Result Set Name, enter a name for the collection that stores the Web service result.
      • Select and deselect the appropriate parameters.
  7. If the Web service reference was created manually:
    1. Select the Web service reference.
    2. Choose the SOAP style.
    3. Choose the message format.
    4. Enter the XPath expression to the node to report on.
    5. Enter the namespace for the SOAP response envelope and click Next.
    6. Enter the name of the collection where the response message is stored.
    7. Enter the names of the parameters that you wish to be included in the report.
  8. Click Create SQL Report.

Editing a Web Service Process

After you create a process of type Web service on a Web service reference created from a WSDL, you can map input parameters to a static value (for example to pass a key) by editing the Web service process.
To edit a Web service process:
  1. Create a Web service process. See "Invoking a Web Service as a Process".
  2. Navigate to the Page Definition containing the Web service process.
  3. Select the process name.
    The Edit Page Process page appears.
  4. To map an input parameter to a static value:
    1. Scroll down to Web Service Input Parameters.
    2. Enter a value in the Value field, adjacent to the appropriate parameter name.
  5. Click Apply Changes.

Viewing a Web Service Reference History

The Web Services History displays changes to Web service references for the current application by application ID, Web service references name, developer, and date.
To view a history of Web service reference changes:
  1. On the Workspace home page, click the Application Builder icon.
  2. Select an application.
    Application Builder appears.
  3. Click Shared Components.
    The Shared Components page appears.
  4. Under Logic, click Web Service References.
  5. Click History.
Note:
The History button only appears on the Web Service Reference page after you have created a Web service reference.
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