[gortazar]

• upgrade: Spring Boot to 4.0.5 and Java to 21
• Actualizar maven-build.yml
• Add spring-boot-starter-json
• Fix Jackson 3.x migration: update imports and API changes in rest_ejem8, bd_ejem19, comunicacion-ws-ejem2
• Fix compilation failures after Spring Boot 4.x / Jackson 3.x upgrade
• Fix all remaining compilation failures: Jackson 3.x, Hibernate 7, Spring Security 7, Spring Session 4.x, CI workflow

[gortazar]

Upgrades every sample to Spring Boot 4.0.5 and Java 21, and fixes the ten
projects that were left broken by the first pass.

Verification

Full sweep of all 85 Maven projects on Temurin 21:

	Before	After
Compile	85	85
Start up	62	72
Fail	11	1
Skipped	12	12

"Start up" means spring-boot:run on a random port reaching Started … in Ns.
Skipped are the projects that need MySQL from docker-compose.

The one remaining failure, parte_5/ejem0-jmeter, is not a regression: it takes
its datasource URL from docker-compose, so it belongs with the skipped group.

What was fixed on top of the upgrade

Jackson 3 migration left half-done — 6 projects. Spring Boot 4 ships Jackson 3,
so com.fasterxml.jackson.databind is gone and Jackson2JsonMessageConverter
threw ClassNotFoundException on JsonMapper at startup. Spring AMQP 4 provides
JacksonJsonMessageConverter for Jackson 3. The ExampleData classes in these
same projects had already been moved to tools.jackson.databind; only the
converter bean was missed.

USER is a SQL reserved word — 3 projects. H2 rejected Hibernate's generated
DDL. MySQL accepts it, which is why these ran for years and only broke on the
H2-backed profiles. Renamed rather than quoted: a delimited identifier is
case-sensitive and must be quoted in every hand-written query, which is a trap
for students using the H2 console.

• parte_5/ejem3-cache-distribuida: User → AppUser
• parte_5/ejem4b-haproxy-ssl-passthrough: User → AppUser
• parte_2/tema_2.5_db/bd_ejer2: the clash is a column, not a table, so
  Post.user → Post.author, with templates and the form field following

In new_post.html only the form field was renamed. The {{#user}} section there
reads the model attribute the controller sets from UserSession, which is a
different thing. Visible labels are left untouched.

Spring Cloud train too old — 1 project. rest_ejem9 imported
spring-cloud-dependencies 2023.0.0, built for Boot 3.2, so OpenFeign's
autoconfiguration looked for WebMvcAutoConfiguration where Boot 4 no longer
keeps it. Moved to 2025.1.4, whose published POM declares
spring-boot.version 4.0.9. It is the only project here importing a Spring
Cloud BOM.

Known issue, not addressed here

parte_2/tema_2.5_db/bd_ejem17 declares querydsl-apt as a provided
dependency with no annotationProcessorPaths, so it relies on implicit
annotation processing. That still works on Java 21, but JDK 23 and later no
longer run processors found on the classpath, and QPost stops being generated.
It will need an explicit annotationProcessorPaths before the next JDK bump.

Supersedes codeurjc#2.

[gortazar]

Merged main and verified the samples it brought in

The branch was 6 commits behind and the PR could not merge. Resolved and re-verified.

The conflict was a rename. main had moved parte_5/ejem1-mysql to
parte_5/ejem1-jmeter/ejem-1 and reorganised the scalability examples, so the two
poms this branch had already bumped showed up as conflicts under a new path. Both
resolved to 4.0.5. ejem-2-cache-redis arrived from main still on 3.5.12 and was
bumped to match. All 86 poms are now on Spring Boot 4.0.5 and Java 21.

Two more breakages, found by running rather than compiling.
ejem1-jmeter/ejem-2-cache-redis compiled fine but did not start:

1. Boot 4 split autoconfiguration into per-area modules, so
   spring-boot-starter-data-redis alone no longer contributes the cache
   autoconfiguration and @EnableCaching found no CacheManager. Added
   spring-boot-starter-cache. This is the same restructuring that broke the
   Spring Cloud import in rest_ejem9.
2. With that fixed, the same Jackson 2 to 3 move as in the AMQP samples surfaced:
   GenericJackson2JsonRedisSerializer is gone. Spring Data Redis 4 provides
   GenericJacksonJsonRedisSerializer, which takes a
   tools.jackson.databind.ObjectMapper and has no no-arg constructor.

These three projects need MySQL, so the automated sweep skips them. They were
booted by hand against mysql:8.0 and redis:alpine containers, with the
repository's own initdb/data_load.sql loaded. All three start.

Current state

	Count
Projects	86
Compile	86
Start up	75 (72 from the sweep + these 3 by hand)
Fail	0
Skipped	11 (need MySQL from docker-compose)

parte_5/ejem0-jmeter is in the skipped group: it takes its datasource URL from
docker-compose, so it cannot start standalone. It is not a regression.

Still open, unrelated to this upgrade

parte_2/tema_2.5_db/bd_ejem17 declares querydsl-apt as provided with no
annotationProcessorPaths, relying on implicit annotation processing. That works
on Java 21 but JDK 23 and later no longer run processors found on the classpath,
so QPost silently stops being generated. Worth fixing before the next JDK bump.

[gortazar]

Smoke tests on every project, and a CI matrix that discovers them

Two commits on top of the previous report.

9724c66 — a smoke test in all 86 projects

Only one project in the branch shipped a test, so "it compiles" was the whole guarantee behind the Spring Boot 4 upgrade. Three shapes, picked per project:

• Spring Boot apps with no external service — @SpringBootTest, which fails if any bean cannot be created. That is the check that caught the Jackson 3 and autoconfiguration breakage earlier in this branch.
• Apps backed by MySQL, RabbitMQ or Redis — Testcontainers through @ServiceConnection, plus a test that opens the connection and checks it answers. 21 projects.
• parte_4/tema_4.2/ejemplo-2 — a plain command-line program with no Spring. It runs main() and asserts the arguments come out. JUnit and surefire are declared by hand there, since that pom has no Boot parent.

Three projects needed more than the test itself:

Project	Problem	Fix
parte_4/tema_4.3/ejemplo-2	Two @SpringBootConfiguration classes (WebApp plus DatabaseWaitConfigurator)	@SpringBootTest(classes = WebApp.class)
parte_4/tema_4.3/ejemplo-3	same	same
parte_2/tema_2.6_despliegue/despliegue_ejem2	The dev profile pins H2Dialect; @ServiceConnection replaces the URL and credentials but not the dialect, so Hibernate emitted sequence DDL against MySQL	The test runs under the prod profile

parte_5/ejem0-jmeter had an Ejem0EmployeeApplicationTests running contextLoads() against a database that only exists under docker-compose, so it could never pass on its own. The new SmokeTest replaces it and brings its own container.

f061417 — CI discovers the projects

The matrix was 86 paths written out by hand, and it went stale as soon as parte_5 was reorganised: run 40696456183 failed on a working directory that no longer existed, not on any code. A discover job now derives the list from git ls-files, so moving or adding a project needs no edit to the workflow. git ls-files rather than find, to keep generated poms under target/ out of the list.

Two other things were wrong in that file:

• The branch filter was '*', which does not match a branch name containing a slash. Pushes to this branch never triggered a run; what did run arrived as a pull_request event, whose filter applies to the base branch. It is '**' now.
• The build ran mvn clean package -DskipTests, so the tests above would never have run in CI. It is mvn -B -ntp clean verify.

A result job gates the matrix, so branch protection has one stable check to require instead of 86 names that change.

Local verification

mvn clean verify on all 86 projects with Temurin 21:

Projects	86
Green	86
Tests run	132
Against real containers	21

Still open, unrelated to this upgrade

parte_2/tema_2.5_db/bd_ejem17 declares querydsl-apt as provided without annotationProcessorPaths. It works on Java 21, but from JDK 23 on javac no longer runs annotation processors found on the classpath, so QPost silently stops being generated.

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