Previously, working with a JarFile created a large amount of garbage
that was allocated on the thread local allocation buffer (TLAB).
The TLAB allocations made a significant contribution to GC pressure
and slowed down startup. This commit reduces the amount of garbage
by making a number of changes.
Reading from a RandomAccessDataFile has been reworked to avoid
creating new RandomAccessFile instances. A single RandomAccessFile
is now created for an entire jar file and it is used to read data from
anywhere in that jar file, including entries in nested jar files. To
ensure that reads remain thread-safe, a lock is taken on the
RandomAccessFile that is shared by all RandomAccessDataFile instances
that are provided access to (portions of) the same jar file.
Reading all of the bytes from a RandomAccessData has been reworked to
avoid the use of an InputStream that was created, used to read the
data, and then thrown away. In place of the InputStream-based
mechanism a method has been introduced that returns all of the
RandomAccessData as a byte[]. Building on this change, a method has
also been introduced to read a portion of a RandomAccessData as a
byte[]. This avoids the need to create a new RandomAccessData
subsection where the subsection was only used to read its entire
contents and then thrown away.
Decoding of an MS-DOS datetime has been reworked to use LocalDataTime
rather than GregorianCalendar. The former produces less garbage than
the latter.
Closes gh-12226
Refactor fat jar loader classes so that less `char[]` instances are
created. This is primarily achieved by adding a new `StringSequence`
class that can chop up Strings without needing to copy the underlying
array. Since Java 8, calls to `String.subString(...)` always copy the
underlying char array. For many of the operations that we need, this
is unnecessary.
Fixes gh-11405
Move projects to better reflect the way that Spring Boot is released.
The following projects are under `spring-boot-project`:
- `spring-boot`
- `spring-boot-autoconfigure`
- `spring-boot-tools`
- `spring-boot-starters`
- `spring-boot-actuator`
- `spring-boot-actuator-autoconfigure`
- `spring-boot-test`
- `spring-boot-test-autoconfigure`
- `spring-boot-devtools`
- `spring-boot-cli`
- `spring-boot-docs`
See gh-9316
