ESQL TUTORIAL FOR MESSAGE BROKER PDF

When you create a message flow, you include input nodes that receive the messages and, optionally, output nodes that send out new or updated messages. If required by the processing that must be performed on the message, you can include other nodes after the input node that complete the actions that your applications need. Some of the built-in nodes enable you to customize the processing that they provide. The Compute , Database , DatabaseInput , and Filter nodes require you to provide a minimum level of ESQL, and you can provide much more than the minimum to control precisely the behavior of each node. This set of topics discusses ESQL and the ways in which you can use it to customize these nodes.

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The following lists the violations that can be produced by MQ-Precise while analyzing Message Broker code. They are broken down below into the categories standards, performance, correctness and other. For a complete list of the rules please follow this link. Queue names should comply to a set length, should be in uppercase, should not contain underscores, cannot start with SYSTEM.

Enforcing a queue names adds to consistency and prevents any issues at run time with MQ names that affect functionality. If the environment is to be used, then the Variables part of the tree should be used.

Flag should be used over Environment. The lower the complexity of a routine the easier it is to test and maintain. A rule of thumb provided by PMD for java is a score of 10 by default.

Function and procedure length The longer a function or procedure is the more difficult the ESQL is to maintain. A rule of thumb provided by PMD for java is a function length of by default. The higher the cyclomatic complexity the lower this threshold should be. A large function of lines with only one path through the code is very likely to be more maintainable then a function of lines with multiple conditional statements. A corporate standard header file can be configured for all ESQL source code.

This may include author, history or licensing of the source code proprietary versus opensource. This code may be able to be removed.

Data kept in the Environment lives as long as the instance of the flow that is being processed ie the memory is only released when the flow ends. Where possible the LocalEnvironment should be used as it is cleaned up the memory is released between nodes.

An atomic block of code could has been found that could be calling another atomic block of code. If two or more broker threads are executing this code at the same time it could result in a deadlock at run-time. A column is being used as a primary key, but the column is not indexed. This could result in a performance issue for queries against larger tables at run-time. There are two or more compute nodes in a row. Filter nodes are unable to change the message tree, only the environment.

Any code that tries to change the message tree will be ignored. This code may fail at run-time. An MQ queue has been listed in the MQ setup but not used in the code. The queue may not be required or there is an issue with the code. An MQ queue has been referred in the code but not listed in the MQ setup. This could cause an issue at run-time if Message Broker attempts to read to or write to a non-existent queue.

It could also indicate that the MQ setup file is not complete. So if you are in the area please drop by and say hello. Download trial version Trial versions are available here We have trial versions of the MB-Precise plugin is available for download here 5. For a complete list of the rules please follow this link Standards Validate queue names against a naming standard Queue names should comply to a set length, should be in uppercase, should not contain underscores, cannot start with SYSTEM.

Environment tree variables If the environment is to be used, then the Variables part of the tree should be used.

Long lines can make code more difficult to read. Any line that is longer then characters will be marked as a violation. Missing file header comment A corporate standard header file can be configured for all ESQL source code. Adding a note allows for obvious documentation within flows. Use LocalEnvironment over Environment Data kept in the Environment lives as long as the instance of the flow that is being processed ie the memory is only released when the flow ends.

Having the check as a loop condition or within a loop should be avoided if possible. Atomic references atomic An atomic block of code could has been found that could be calling another atomic block of code.

Tree navigation could be a reference The message tree is being navigated more then it needs to be. A reference will improve performance as it prevents multiple parses of the data in the message. Multiple compute nodes in a row There are two or more compute nodes in a row. Check filter nodes do not affect messages Filter nodes are unable to change the message tree, only the environment. Downloads Download trial version Trial versions are available here We have trial versions of the MB-Precise plugin is available for download here 5.

This indicates that the ESQL code on a single line is very long. The message tree is being navigated more then it needs to be.

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Integration Bus/Message Broker Rules summary

Coding conventions not only help improve code readability, they also discourage the use of wasteful and error-prone programming practices. Coding guidelines can also encourage the development of secure software that has better performance. Finally, should source code need to be shipped as a product, coding conventions can help ensure a quality in presentation. Topics include file naming and organization, file layout, comments, line wrapping, alignment, white space, naming conventions, frequently used statements, and useful programming practices. In general, ESQL files longer than lines are cumbersome to deal with and should be avoided, by ensuring that a single ESQL file implements the message flows that relate to each other, and by abstracting reusable code into separate ESQL files. They also serve to create local name spaces so that procedures and functions can be reused, and yet be distinguished by the schema they are in.

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