Lazily initialize SecureRandom in MimeTypeUtils [SPR-16974]

[spring-projects-issues]

Andy Wilkinson opened SPR-16974 and commented

Creating a new instance of SecureRandom can have a large cost in terms of elapsed time. On Linux, the JVM uses /dev/random by default which will block until there is sufficient entropy available to produce a random value. As things stand, whenever MimeTypeUtils is loaded, this cost will be incurred, irrespective of whether or not generateMultipartBoundary() is ever called. I think it would be better if the SecureRandom instance was initialized lazily so that the cost is only incurred when the instance is needed.

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Affects: 5.0.7

Reference URL: spring-projects/spring-boot#6174

Issue Links:

• Generate multipart boundary using SecureRandom [SPR-16635] #21176 Generate multipart boundary using SecureRandom

Referenced from: commits 847202c, 4402336