Email 198 performance in image html email

[seanfabs]

There are several fixes and improvements to the regex's here:

1. The regex could run with exponential time in the \\s*[^>]*?\\s+ part, this is because the \s, [^>], and \\s+ parts can all match whitespace and so when excessive whitespace is encountered it will attempt all combinations to find a match. This is a fairly well documented phenomenon https://blog.codinghorror.com/regex-performance/
2. The <script> tag matching did not match multiple scripts.
3. Fix the edge case where tags could match which started with img or script e.g. <imgx ...>
4. Use a greedy matcher for the src url [^\"']+ which gives a slight performance boost - we will always want to grab the whole url.

One question is should I also update the similar class in the javax package?

Benchmark results

VM version: JDK 17.0.10, OpenJDK 64-Bit Server VM, 17.0.10+8-b1207.12

Result for old regex (<[Ii][Mm][Gg]\s*[^>]*?\s+[Ss][Rr][Cc]\s*=\s*["'])([^"']+?)(["'])

32.339 ±(99.9%) 4.394 ops/s [Average]
(min, avg, max) = (20.590, 32.339, 40.601), stdev = 5.866
CI (99.9%): [27.945, 36.733] (assumes normal distribution)

Result for new regex - candidate non greedy url (<[Ii][Mm][Gg](?=\s)[^>]*?\s[Ss][Rr][Cc]\s*=\s*["'])([^"']+?)(["'])

1244.602 ±(99.9%) 225.819 ops/s [Average]
(min, avg, max) = (518.410, 1244.602, 1512.089), stdev = 301.462
CI (99.9%): [1018.783, 1470.420] (assumes normal distribution)

Result for new regex (<[Ii][Mm][Gg](?=\s)[^>]*?\s[Ss][Rr][Cc]\s*=\s*["'])([^"']+)(["'])

1480.002 ±(99.9%) 160.408 ops/s [Average]
(min, avg, max) = (986.366, 1480.002, 1651.095), stdev = 214.140
CI (99.9%): [1319.594, 1640.409] (assumes normal distribution)

[garydgregory]

Hello @seanfabs
Thank you for your PR. Please see my comments.

[garydgregory]

Hello @seanfabs
I can't reproduce these results unless a benchmark run executes tests with old and new code. You can usually do this by copying old code into a benchmark test method so that you have two methods: One tests the new patched main code and the old runs the old code now living in the benchmark; in this case, it's not much code since these are REs. Please rebase on git master to pick up the new Maven I added to facilitate running benchmarks from the command line like mvn -P benchmark -Dbenchmark=ImageHtmlEmailBenchmark -pl commons-email2-jakarta.
TY!

[garydgregory]

@seanfabs
Please see my comment.

[seanfabs]

Thanks for the suggestion, changes made

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 76.71%. Comparing base (0bd7e34) to head (59a9c16).
Report is 140 commits behind head on master.

Additional details and impacted files

@@             Coverage Diff              @@
##             master     #239      +/-   ##
============================================
+ Coverage     74.34%   76.71%   +2.36%     
- Complexity      353      635     +282     
============================================
  Files            22       39      +17     
  Lines          1072     1915     +843     
  Branches        126      233     +107     
============================================
+ Hits            797     1469     +672     
- Misses          216      345     +129     
- Partials         59      101      +42     

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