Update linker plugin aot option (#1157)

* Update aotCache option and behavior when addClassDataSharingArchive=false

Author: barchetta

.gitignore

@@ -24,3 +24,4 @@ node_modules/
 node/
 *.swp
 .factorypath
+.oca/

maven-plugins/helidon-maven-plugin/README.md

@@ -139,7 +139,7 @@ This goal binds to the `package` phase by default.
 | defaultDebugOptions        | List    | []                | JVM debug options to use if the `--debug` flag is passed to the `start` script |
 | additionalModules          | Set     | []                | Add any modules that may not be found automatically                            |
 | addClassDataSharingArchive | boolean | `true`            | Add a Class Data Sharing archive to reduce startup time                        |
-| addAotCache                | boolean | `true`            | Add an Aot Cache to reduce startup/warmup time. Ignored if Java 24 or earlier  |
+| aotCache                   | String  | `true`            | Add an Aot Cache to reduce startup/warmup time. Ignored if Java 24 or earlier  |
 | testImage                  | boolean | `true`            | Start the application after the image is built                                 |
 | stripDebug                 | boolean | `false`           | Remove all debug support from the image, including within `.class` files       |
 | skipJavaImage              | boolean | `false`           | Skip this goal execution                                                       |
@@ -150,7 +150,8 @@ Notes:
 * The above parameters are mapped to user properties of the form `jlink.image.PROPERTY`, e.g.  
   `-Djlink.image.addClassDataSharingArchive=false`
 * Multiple arguments for the `jlink.image.additionalJlinkArgs` property must be comma separated.
-* If both `addClassDataSharingArchive` and `addAotCache` are true then an Aot Cache will be created if Java 25 or newer.
+* If `addClassDataSharingArchive` is `false` then `aotCache` is ignored.
+* Values for `aotCache`: `true`, `false`, `cds` (to force use of CDS archive instead of AOT Cache).
 
 ### General usage
 

maven-plugins/helidon-maven-plugin/src/main/java/io/helidon/build/maven/JLinkImageMojo.java

@@ -68,10 +68,10 @@ public class JLinkImageMojo extends AbstractMojo {
     private boolean addClassDataSharingArchive;
 
     /**
-     * Add an AOT cache to reduce startup time.
+     * Add an AOT cache to reduce startup time if Java 25 or newer: true, false, cds.
      */
-    @Parameter(defaultValue = "true", property = "jlink.image.addAotCache")
-    private boolean addAotCache;
+    @Parameter(defaultValue = "true", property = "jlink.image.aotCache")
+    private String aotCache;
 
     /**
      * Test the image after creation.
@@ -178,22 +178,28 @@ private Path mainJar(Path buildDir) throws MojoFailureException {
      *
      * @return Startup cache type to use
      */
-    private Configuration.CacheType determinCacheType() {
+    private Configuration.CacheType determinCacheType() throws MojoFailureException {
+
+        if (!addClassDataSharingArchive) {
+            // For backwards compatibility we don't generate any cache if old CDS flag is false
+            // No matter what JDK we are running on.
+            return Configuration.CacheType.NONE;
+        }
+
         if (JavaRuntime.CURRENT_JDK.version().feature() <= 24) {
-            if (addClassDataSharingArchive) {
-                return Configuration.CacheType.CDS;
-            } else {
-                return Configuration.CacheType.NONE;
-            }
+            return Configuration.CacheType.CDS;
         }
 
         // Java 25 or newer
-        if (addAotCache) {
+        if (aotCache.equalsIgnoreCase("true")) {
+            // Default case under Java 25
             return Configuration.CacheType.AOT;
-        } else if (addClassDataSharingArchive) {
+        } else if (aotCache.equalsIgnoreCase("false")) {
+            return Configuration.CacheType.NONE;
+        } else if (aotCache.equalsIgnoreCase("cds")) {
             return Configuration.CacheType.CDS;
         } else {
-            return Configuration.CacheType.NONE;
+            throw new MojoFailureException("Invalid aotCache value " + aotCache + ": must be one of: true, false, cds");
         }
     }
 }