Lukasz Lenart created WW-5689:
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Summary: Lean core: extract FreeMarker, tag library and JSP
support into dedicated plugins
Key: WW-5689
URL: https://issues.apache.org/jira/browse/WW-5689
Project: Struts 2
Issue Type: Task
Components: Core
Reporter: Lukasz Lenart
Fix For: 8.0.0
h2. Goal
Reduce {{struts2-core}} to routing, dispatch, the OGNL value stack and the
interceptor/result machinery. View technologies become opt-in plugins, so a
REST/JSON-only application carries no JSP, no tag library and no FreeMarker.
The default assembly still bundles all three, so the out-of-the-box
distribution is unchanged for existing users — this is Ted Husted's "omnibus
jar" answer from the original 2007 dev@ thread.
Supersedes WW-2278 (closed Won't Fix — "move the tags into a plugin" is not the
change anyone would make today; see the triage comment there for the evidence).
Blocked by WW-4759. Its governing constraint applies here unchanged: OSGi
{{Export-Package}} and the JPMS direction forbid split packages, so every
module cut must be whole-package with FQCNs preserved, and the
API/implementation de-mixing has to land first.
h2. Proposed modules
* {{struts2-freemarker-plugin}} — {{org.apache.struts2.views.freemarker}}
(FreemarkerManager, FreemarkerResult, FreemarkerThemeTemplateLoader),
{{components.template.FreemarkerTemplateEngine}}, and the FTL theme templates
* {{struts2-tags-plugin}} — {{org.apache.struts2.components}},
{{org.apache.struts2.views.jsp}} plus the generated
{{META-INF/struts-tags.tld}}, {{org.apache.struts2.views.annotations}}
* {{struts2-jsp-plugin}} — {{components.template.JspTemplateEngine}},
{{JspSupportServlet}}, JSP-side template support
The tags/JSP boundary is genuinely fuzzy and needs a design decision rather
than an assumption: the tag components are useless without some template engine
behind them.
h2. Core decoupling that must happen first
Each of these is independently reviewable and can land in 7.x ahead of the
module split. Together they are what actually makes FreeMarker optional —
core's own dependency on it is three convenience pages.
h1. {{DefaultDispatcherErrorHandler}} renders the dev-mode error page through
FreemarkerManager. It needs a template-free default.
h1. {{ExecuteAndWaitInterceptor}} defaults to FreemarkerResult for the wait
page. The default must not hard-reference a view technology.
h1. {{DebuggingInterceptor}} imports FreemarkerResult and FreemarkerManager.
Same treatment.
h1. Core extension points currently living in view packages must move to
core-owned packages (WW-4759 step (i)): {{components.UrlRenderer}},
{{views.util.UrlHelper}}, {{components.date.DateFormatter}},
{{components.template.TemplateEngine}} and {{TemplateEngineManager}},
{{components.Component}}.
h1. {{StrutsBeanSelectionProvider}} and {{struts-beans.xml}} hard-register nine
view beans. Those registrations move into each plugin's {{struts-plugin.xml}}.
h2. Compatibility
FQCNs preserved throughout; {{struts2-core}} must never depend on a plugin.
Seven existing plugins import these packages and will need dependency updates:
javatemplates, velocity, jasperreports7, jasperreports, tiles, convention,
config-browser.
h2. Scope note
Major structural change, targeted for Struts 8.0.0, sequenced after WW-4759.
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