Using direct WebSphere MQ API calls

The WebSphere® MQ API is a set of program interfaces that you can use to request services from the message queue manager.

The WebSphere MQ API (also known as the MQ Interface, or MQI) accesses the message queue manager directly. Because of the complexity of the interface, the ease of making mistakes, and the lack of flexibility, use the MQI only to maintain existing code. New code should use the EGL add and get next statements to access message queue or TOPIC information.

MQ directly API not supported for Publish – subscribe.

EGL supports the following MQI functions:
To use direct WebSphere MQ API calls, you must enable an EGL Project Feature:
  1. Right-click the project name in the Project Explorer view.
  2. Select Properties.
  3. Click EGL Project Features in the left side of the Properties dialog.
  4. Check the box next to EGL with low-level MQ API support.
  5. Click OK.

IBM MQ reusable parts

EGL provides a set of reusable parts, which are parameters, records, and functions that you can use or modify to make direct calls to the WebSphere MQ API. The source files for these parts are located in the SDP70Shared\plugins\\MqReusableParts directory.

MQI parameters are either data items or records. The MQSTATE and MQATTRIBUTES sample records contain declarations for most data item parameters.

The BUFFER parameter (message buffer parameter used with MQGET, MQPUT, and MQPUT1 calls) and the CHARATTRS (character attributes buffer parameter used with MQINQ and MQSET calls) are both defined with a length of 1024 characters. Increase the length of these items if you reuse MQSTATE in a program that requires larger buffers.

Sample records are provided to define the format of record parameters and special purpose messages and message headers. Record names are the same as the COBOL structure names. The data items in the records have the same names as the corresponding fields in the COBOL structures, except that the COBOL names use a hyphen (-) as a token separator instead of an underscore.

The following table shows the names of the sample records for direct WebSphere MQ calls.

Table 1. Sample records for IBM® MQ calls
Record Description Initializer function
MQBO Begin options MQBO_INIT
MQCNO Connect options MQCNO_INIT
MQDH Distribution header MQDH_INIT
MQDLH Dead-letter header MQDLH_INIT
MQGMO Get-message options parameter MQGMO_INIT
MQINTATTRS Integer attributes parameter MQINTATTRS_INIT
MQMD Message descriptor parameter MQMD_INIT
MQMD1 Message descriptor (version 1) MQMD1_INIT
MQMDE Message descriptor extension MQMDE_INIT
MQOD Object descriptor parameter MQOD_INIT
MQOR Object record MQOR_INIT
MQPMO Put-message options structure MQPMO_INIT
MQRMH Message reference header MQRMH_INIT
MQRR Response record MQRR_INIT
MQSD Subscription descriptor record MQSD_INIT
MQSELECTORS Attribute selectors parameter MQSELECTORS_INIT
MQTM Trigger message structure MQTM_INIT
MQTMC2 Trigger message 2 (character format) MQTMC2_INIT
MQXQH Transmission queue header MQXQH_INIT

The following table shows the sample EGL functions that call WebSphere MQ API functions.

Table 2. EGL functions that call WebSphere MQ API functions
Function Description
MQCONN Connect to message queue manager
MQCONNX Extended connect
MQDISC Disconnect from message queue manager
MQOPEN Open a message queue
MQCLOSE Close a message queue
MQGET Read a message from a queue
MQPUT Write a message to a queue
MQPUT1 Write a single message to a queue including queue open and close
MQINQ Inquire about queue attributes
MQSET Set queue attributes
MQBEGIN Begin a logical unit of work
MQCMIT Commit a logical unit of work
MQBACK Back out a logical unit of work