问题
The tibco documentation says
The Mapper activity adds a new process variable to the process definition. This variable can be a simple datatype, a TIBCO ActiveEnterprise schema, an XML schema, or a complex structure.
so my question is tibco mapper does only this simple function.We can create process variables in process definition also(by right clicking on process definition).I looked for it in google but no body clearly explains why to use this activity and I have also tried in youtube and there also only one video and it does not explain clearly.I am looking for an example how it is used in large organizations and a real time example.Thanks in advance
回答1:
The term "process variable" is a bit overloaded I guess:
The process variables that you define in the Process properties are stateful. You can use (read) their values anywhere in the process and you can change their values during the process using the Assign task (yellow diamond with a black equals sign).
The mapper activity produces a new output variable of that task that you can only use (read) in activities that are downstream from it. You cannot change its value after the mapper activity, as for any other activity's output.
The mapper activity is mainly useful to perform complex and reusable data mappings in it rather than in the mappers of other activities. For example, you have a process that has to map its input data into a different data structure and then has to both send this via a JMS message and log it to a file. The mapper allows you to perform the mapping only once rather than doing it twice (both in the Send JMS and Write to File activity).
You'll find that in real world projects, the mapper activity is quite often used to perform data mapping independently of other activities, it just gives a nicer structure to the processes. In contrast the Process Variables defined in the Process properties together with the Assign task are used much less frequently.
Here's a very simple example, where you use the mapper activity once to set a process variable (here the filename) and then use it in two different following activities (create CSV File and Write File). Obviously, the mapper activity becomes more interesting if the mapping is not as trivial as here (though even in this simple example, you only have one place to change how the filename is generated rather than two):
Mapper Activiy
First use of the filename variable in Create File
Second use of the filename variable in Write File
回答2:
Process Variable/Assign Activity Vs Mapper Activity
The primary purpose of an assign task is to store a variable at a process level. Any variable in an assign task can be modified N times in a process. But a mapper is specifically used for introducing a new variable. We cannot change the same mapper variable multiple times in a project.
Memory is allocated to Process Variable when the process instance is created but in case of TIBCO Mapper the memory is allocated only when the mapper activity is executed in a process instance.
Process Variable is allocated a single slot of memory which is used to update/modify the schema thought the process instance execution i.e. N number of assign activity will access same memory allocated to the variable. Whereas using N mapper for a same schema will create N amount of memory.
Assign Activity can be is used to accumulate the output of a tibco activity inside a group.
来源：https://stackoverflow.com/questions/24925787/why-do-we-use-tibco-mapper-activity