Struts Boot Hello

The smallest Struts Boot application: one action, one FreeMarker template, no web.xml, no struts.xml.

Struts Boot is experimental: its API and defaults may change between minor releases.

Three steps

1. Depend on org.apache.struts:struts2-boot-starter, at the same version as the rest of Struts. Importing org.apache.struts:struts2-bom in <dependencyManagement> keeps the versions aligned so the starter needs no <version> of its own.

2. Implement StrutsBootApplication and register actions:

   public class HelloApp implements StrutsBootApplication {
   
       public static void main(String[] args) {
           StrutsBoot.run(HelloApp.class, args);
       }
   
       @Override
       public void actions(ActionRegistry actions) {
           actions.action("hello", HelloAction.class).success("hello.ftl");
       }
   }
   

3. Put the view in src/main/resources/templates/hello.ftl and run main().

Then open http://localhost:8080/hello.action.

Running the jar

mvn package -pl apps/boot-hello -am -DskipAssembly -DskipTests
java -jar apps/boot-hello/target/struts2-boot-hello-<version>.jar --struts.boot.port=9090

<version> is the Struts version being built, for example struts2-boot-hello-7.5.0-SNAPSHOT.jar. The example is not deployed to Maven repositories; build it from source.

Settings

Settings are read from struts.properties on the classpath. A --key=value argument overrides the file.

Key	Default	Meaning
struts.boot.port	8080	HTTP port; 0 picks a free port
struts.boot.context-path	""	Context path the application is served at
struts.boot.address	all	Interface to listen on, e.g. 127.0.0.1

Defaults worth knowing

• Tomcat listens on all interfaces, not only on localhost; set struts.boot.address to restrict it.
• Error pages show the status only, without stack traces or the Tomcat version.
• struts.devMode stays off.
• Each start uses a fresh temporary base directory (struts-boot-<uuid>) that is deleted on shutdown.
• Views are FreeMarker only; a result path such as hello.ftl resolves to /templates/hello.ftl on the classpath.

Shading and plugins

The jar is built with maven-shade-plugin. Every Struts plugin ships its own META-INF/struts-plugin.xml, and shading keeps only one file with that name, so with two or more plugins on the classpath all but one would be silently lost. This example uses no plugins. If your application needs them, package it differently instead of shading: a thin jar with its dependencies in a lib/ directory (maven-dependency-plugin copies them, maven-jar-plugin writes the Class-Path manifest entry), or a distribution built with maven-assembly-plugin.

Logging

Struts logs through the Log4j 2 API, and the starter ships no logging backend, so warnings and errors from Struts are not printed. Add one to your application, for example (version managed by org.apache.logging.log4j:log4j-bom):

<dependency>
    <groupId>org.apache.logging.log4j</groupId>
    <artifactId>log4j-core</artifactId>
    <scope>runtime</scope>
</dependency>

with a log4j2.xml on the classpath, or log4j-slf4j2-impl to route to an SLF4J backend.