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JIRA: https://jira.spring.io/browse/INT-4144 Fixes GH-1936 (https://github.com/spring-projects/spring-integration/issues/1936) Previously `LoggingHandler` could be used as a standalone object, without any Spring Container initialization. Even if that doesn't sound reasonable, we should reinstate the logic to avoid breaking changes * Initialize `expression` and `evaluationContext` during object `<init>` phase * Some code reformatting to avoid duplicate blocks and cyclomatic complexity * Simple code formatting * Additional JavaDocs for `LoggingHandler` **Cherry-pick to 4.3.x**