During command execution a lot of exceptions may be thrown. Some of them represent error situations which can be handled specifically by the caller of the command. But a lot of exceptions are so low-level that is is unlikely that the caller of the command can handle them effectively. The huge number of these low-level exceptions which are thrown by the commands lead to a complicated and wide interface of the commands. Callers of the API have to deal with a lot of exceptions they don't understand.
To overcome this situation this class was introduced. Commands will wrap all exceptions they declare as low-level in their context into an instance of this class. Callers of the commands have to deal with one type of low-level exceptions. Callers will always get access to the original exception (if available) by calling {@code #getCause()}.
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