Upgrade explicit Java versions in pom.xml files that have no Maven model

src/main/java/org/openrewrite/java/migrate/UpgradeJavaVersion.java

@@ -52,6 +52,7 @@ public List<Recipe> getRecipeList() {
         return Arrays.asList(
                 new UseMavenCompilerPluginReleaseConfiguration(version),
                 new UpdateMavenProjectPropertyJavaVersion(version),
+                new UpgradeUnmodeledMavenJavaVersion(version),
                 new org.openrewrite.jenkins.UpgradeJavaVersion(version, null),
                 new UpdateJavaCompatibility(version, null, null, false, null),
                 new UpdateSdkMan(String.valueOf(version), null),

src/main/java/org/openrewrite/java/migrate/UpgradeUnmodeledMavenJavaVersion.java

@@ -0,0 +1,79 @@
+/*
+ * Copyright 2026 the original author or authors.
+ * <p>
+ * Licensed under the Moderne Source Available License (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ * <p>
+ * https://docs.moderne.io/licensing/moderne-source-available-license
+ * <p>
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.openrewrite.java.migrate;
+
+import lombok.EqualsAndHashCode;
+import lombok.Value;
+import org.openrewrite.ExecutionContext;
+import org.openrewrite.Option;
+import org.openrewrite.Recipe;
+import org.openrewrite.TreeVisitor;
+import org.openrewrite.maven.tree.MavenResolutionResult;
+import org.openrewrite.xml.XPathMatcher;
+import org.openrewrite.xml.XmlIsoVisitor;
+import org.openrewrite.xml.tree.Xml;
+
+@Value
+@EqualsAndHashCode(callSuper = false)
+public class UpgradeUnmodeledMavenJavaVersion extends Recipe {
+    @Option(displayName = "Java version", description = "The minimum Java version.", example = "25")
+    Integer version;
+
+    String displayName = "Upgrade Java version in alternate Maven builds";
+    String description = "Update explicit Java version properties and compiler settings in pom.xml files parsed as XML " +
+            "without a Maven model, for example in a repository built with Gradle. Property references are left intact.";
+
+    @Override
+    public TreeVisitor<?, ExecutionContext> getVisitor() {
+        return new XmlIsoVisitor<ExecutionContext>() {
+            private final XPathMatcher properties = new XPathMatcher("/project/properties/*");
+            private final XPathMatcher compiler = new XPathMatcher("//plugin[artifactId='maven-compiler-plugin']/configuration/*");
+
+            @Override
+            public Xml.Document visitDocument(Xml.Document document, ExecutionContext ctx) {
+                if (!"pom.xml".equals(document.getSourcePath().getFileName().toString()) ||
+                        document.getMarkers().findFirst(MavenResolutionResult.class).isPresent()) {
+                    return document;
+                }
+                return super.visitDocument(document, ctx);
+            }
+
+            @Override
+            public Xml.Tag visitTag(Xml.Tag tag, ExecutionContext ctx) {
+                Xml.Tag t = super.visitTag(tag, ctx);
+                String name = t.getName();
+                boolean javaProperty = properties.matches(getCursor()) &&
+                        ("java.version".equals(name) || "maven.compiler.release".equals(name) ||
+                         "maven.compiler.source".equals(name) || "maven.compiler.target".equals(name));
+                boolean compilerSetting = compiler.matches(getCursor()) &&
+                        ("release".equals(name) || "source".equals(name) || "target".equals(name));
+                if (compilerSetting) {
+                    Xml.Tag plugin = getCursor().getParentOrThrow().getParentOrThrow().getValue();
+                    compilerSetting = "org.apache.maven.plugins".equals(
+                            plugin.getChildValue("groupId").orElse("org.apache.maven.plugins"));
+                }
+                if (javaProperty || compilerSetting) {
+                    String value = t.getValue().orElse("");
+                    String major = value.startsWith("1.") ? value.substring(2) : value;
+                    if (major.matches("[0-9]{1,3}") && Integer.parseInt(major) < version) {
+                        return t.withValue(version.toString());
+                    }
+                }
+                return t;
+            }
+        };
+    }
+}