Require Java 17 or newer

Jenkinsfile

@@ -14,12 +14,12 @@ properties([
 
 def axes = [
   platforms: ['linux', 'windows'],
-  jdks: [11, 17, 21],
+  jdks: [17, 21],
 ]
 
 stage('Record build') {
   retry(conditions: [kubernetesAgent(handleNonKubernetes: true), nonresumable()], count: 2) {
-    node('maven-11') {
+    node('maven-17') {
       infra.checkoutSCM()
 
       /*

core/src/main/java/jenkins/monitor/JavaVersionRecommendationAdminMonitor.java

@@ -78,15 +78,11 @@ public class JavaVersionRecommendationAdminMonitor extends AdministrativeMonitor
 
     static {
         NavigableMap<Integer, LocalDate> supportedVersions = new TreeMap<>();
-        // Adjust Java 11 end of life date for weekly and LTS
+        // Adjust Java 11 end of life date for LTS
         if (Jenkins.VERSION.split("[.]").length > 2) {
             // LTS will require Java 17 or newer beginning 30 Oct 2024
             // https://groups.google.com/g/jenkinsci-dev/c/gsXAqOQQEPc/m/VT9IBYdmAQAJ
             supportedVersions.put(11, LocalDate.of(2024, 9, 30)); // Temurin: 2024-10-31
-        } else {
-            // Weekly will require Java 17 or newer beginning 18 Jun 2024
-            // https://groups.google.com/g/jenkinsci-dev/c/gsXAqOQQEPc/m/4fn4Un1iAwAJ
-            supportedVersions.put(11, LocalDate.of(2024, 6, 18)); // Temurin: 2024-10-31
         }
         supportedVersions.put(17, LocalDate.of(2026, 3, 31)); // Temurin: 2027-10-31
         supportedVersions.put(21, LocalDate.of(2027, 9, 30)); // Temurin: 2029-09-30

pom.xml

@@ -28,7 +28,7 @@ THE SOFTWARE.
   <parent>
     <groupId>org.jenkins-ci</groupId>
     <artifactId>jenkins</artifactId>
-    <version>1.115</version>
+    <version>1.116</version>
     <relativePath />
   </parent>
 

war/pom.xml

@@ -136,6 +136,51 @@ THE SOFTWARE.
   <build>
     <finalName>jenkins</finalName>
     <plugins>
+      <!-- TODO When Java 11 usage declines to a terminal level, this can be deleted. -->
+      <plugin>
+        <groupId>org.apache.maven.plugins</groupId>
+        <artifactId>maven-enforcer-plugin</artifactId>
+        <executions>
+          <execution>
+            <id>display-info</id>
+            <configuration>
+              <rules>
+                <requireJavaVersion>
+                  <version>11</version>
+                </requireJavaVersion>
+                <enforceBytecodeVersion>
+                  <maxJdkVersion>11</maxJdkVersion>
+                  <excludes>
+                    <exclude>org.jenkins-ci:commons-jelly</exclude>
+                    <exclude>org.jenkins-ci.main:cli</exclude>
+                    <exclude>org.jenkins-ci.main:jenkins-core</exclude>
+                    <exclude>org.jenkins-ci.main:websocket-jetty10</exclude>
+                    <exclude>org.jenkins-ci.main:websocket-spi</exclude>
+                    <exclude>org.kohsuke.stapler:stapler</exclude>
+                    <exclude>org.kohsuke.stapler:stapler-groovy</exclude>
+                    <exclude>org.kohsuke.stapler:stapler-jelly</exclude>
+                  </excludes>
+                </enforceBytecodeVersion>
+              </rules>
+            </configuration>
+          </execution>
+        </executions>
+      </plugin>
+      <plugin>
+        <groupId>org.apache.maven.plugins</groupId>
+        <artifactId>maven-compiler-plugin</artifactId>
+        <configuration>
+          <release>11</release>
+          <testRelease>11</testRelease>
+        </configuration>
+      </plugin>
+      <plugin>
+        <groupId>org.apache.maven.plugins</groupId>
+        <artifactId>maven-javadoc-plugin</artifactId>
+        <configuration>
+          <release>11</release>
+        </configuration>
+      </plugin>
       <plugin>
         <artifactId>maven-war-plugin</artifactId>
         <!-- version specified in grandparent pom -->

war/src/main/java/executable/Main.java

@@ -76,7 +76,7 @@ public class Main {
      * This list must remain synchronized with the one in {@code
      * JavaVersionRecommendationAdminMonitor}.
      */
-    private static final NavigableSet<Integer> SUPPORTED_JAVA_VERSIONS = new TreeSet<>(List.of(11, 17, 21));
+    private static final NavigableSet<Integer> SUPPORTED_JAVA_VERSIONS = new TreeSet<>(List.of(17, 21));
 
     /**
      * Sets custom session cookie name.

war/src/test/java/executable/MainTest.java

@@ -11,34 +11,28 @@ class MainTest {
     void unsupported() {
         assertJavaCheckFails(8, false);
         assertJavaCheckFails(8, true);
+        assertJavaCheckFails(11, false);
+        assertJavaCheckFails(11, true);
     }
 
     @Test
     void supported() {
-        assertJavaCheckPasses(11, false);
-        assertJavaCheckPasses(11, true);
         assertJavaCheckPasses(17, false);
         assertJavaCheckPasses(17, true);
+        assertJavaCheckPasses(21, false);
+        assertJavaCheckPasses(21, true);
     }
 
     @Test
     void future() {
-        assertJavaCheckFails(12, false);
-        assertJavaCheckFails(13, false);
-        assertJavaCheckFails(14, false);
-        assertJavaCheckFails(15, false);
-        assertJavaCheckFails(16, false);
         assertJavaCheckFails(18, false);
         assertJavaCheckFails(19, false);
         assertJavaCheckFails(20, false);
-        assertJavaCheckPasses(12, true);
-        assertJavaCheckPasses(13, true);
-        assertJavaCheckPasses(14, true);
-        assertJavaCheckPasses(15, true);
-        assertJavaCheckPasses(16, true);
+        assertJavaCheckFails(22, false);
         assertJavaCheckPasses(18, true);
         assertJavaCheckPasses(19, true);
         assertJavaCheckPasses(20, true);
+        assertJavaCheckPasses(22, true);
     }
 
     private static void assertJavaCheckFails(int releaseVersion, boolean enableFutureJava) {