diff --git a/Jenkinsfile b/Jenkinsfile
index d6aca0f..5383ecd 100644
--- a/Jenkinsfile
+++ b/Jenkinsfile
@@ -8,7 +8,7 @@ pipeline {
             steps {
                 sh "./gradlew clean build"
                 junit testResults: "build/test-results/test/*.xml"
-                javadoc javadocDir: "build/docs/javadoc"
+                javadoc javadocDir: "build/docs/javadoc", keepAll: true
                 archiveArtifacts artifacts: 'build/libs/*.jar,benchmark/build/libs/*.jar',
                                  allowEmptyArchive: true,
                                  fingerprint: true,
diff --git a/build.gradle b/build.gradle
index 735aa48..f22e406 100644
--- a/build.gradle
+++ b/build.gradle
@@ -1,6 +1,6 @@
 plugins {
     id 'maven-publish'
-    id 'net.woggioni.plugins.multi-release-jar'
+    id 'net.woggioni.gradle.multi-release-jar'
     id 'net.woggioni.gradle.lombok' apply false
 }
 
@@ -27,6 +27,10 @@ allprojects {
     }
 }
 
+ext {
+    setProperty('jpms.module.name', 'net.woggioni.jwo')
+}
+
 
 configurations {
     pathClassloaderTest
diff --git a/gradle.properties b/gradle.properties
index e4d7fa3..9cab269 100644
--- a/gradle.properties
+++ b/gradle.properties
@@ -1,4 +1,4 @@
-gradle.version = 7.1.1
+gradle.version = 7.2
 jwo.version=1.0
 junitJupiter.version=5.7.0
 lombok.version=1.18.16
diff --git a/gradle/wrapper/gradle-wrapper.properties b/gradle/wrapper/gradle-wrapper.properties
index 05679dc..ffed3a2 100644
--- a/gradle/wrapper/gradle-wrapper.properties
+++ b/gradle/wrapper/gradle-wrapper.properties
@@ -1,5 +1,5 @@
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-7.1.1-bin.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-7.2-bin.zip
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists
diff --git a/settings.gradle b/settings.gradle
index 3209b19..607c2ca 100644
--- a/settings.gradle
+++ b/settings.gradle
@@ -8,7 +8,7 @@ pluginManagement {
 
     plugins {
         id "net.woggioni.gradle.lombok" version "0.1"
-        id "net.woggioni.plugins.multi-release-jar" version "0.1"
+        id "net.woggioni.gradle.multi-release-jar" version "0.1"
     }
 }
 
diff --git a/src/main/java/net/woggioni/jwo/DelegatingMap.java b/src/main/java/net/woggioni/jwo/DelegatingMap.java
new file mode 100644
index 0000000..d0203f4
--- /dev/null
+++ b/src/main/java/net/woggioni/jwo/DelegatingMap.java
@@ -0,0 +1,127 @@
+package net.woggioni.jwo;
+
+import java.util.Collection;
+import java.util.Collections;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+import java.util.function.Supplier;
+
+public class DelegatingMap<K,V> implements Map<K, V> {
+    private final Supplier<Map<K,V>> mapFactory;
+    private final List<Map<K,V>> delegates;
+    private final Map<K,V> thisMap;
+
+    public DelegatingMap(Supplier<Map<K,V>> mapFactory, List<Map<K,V>> delegates) {
+        this.mapFactory = mapFactory;
+        this.delegates = delegates;
+        thisMap = mapFactory.get();
+    }
+
+    @Override
+    public int size() {
+        throw new UnsupportedOperationException();
+    }
+
+    @Override
+    public boolean isEmpty() {
+        if(!thisMap.isEmpty()) return false;
+        for(Map<K,V> delegate : delegates) {
+            if(!delegate.isEmpty()) {
+                return false;
+            }
+        }
+        return true;
+    }
+
+    @Override
+    public boolean containsKey(Object key) {
+        if(thisMap.containsKey(key)) return true;
+        for(Map<K,V> delegate : delegates) {
+            if(!delegate.containsKey(key)) {
+                return true;
+            }
+        }
+        return false;
+    }
+
+    @Override
+    public boolean containsValue(Object value) {
+        if(thisMap.containsValue(value)) return true;
+        for(Map<K,V> delegate : delegates) {
+            if(!delegate.containsValue(value)) {
+                return true;
+            }
+        }
+        return false;
+    }
+
+    @Override
+    public V get(Object key) {
+        V result = thisMap.get(key);
+        if(result != null) return result;
+        for(Map<K,V> delegate : delegates) {
+            result = delegate.get(key);
+            if(result != null) break;
+        }
+        return result;
+    }
+
+    @Override
+    public V put(K key, V value) {
+        V result = thisMap.put(key, value);
+        if(result != null) return result;
+        for(Map<K,V> delegate : delegates) {
+            result = delegate.put(key, value);
+            if(result != null) break;
+        }
+        return result;
+    }
+
+    @Override
+    public V remove(Object key) {
+        V result = thisMap.remove(key);
+        if(result != null) return result;
+        for(Map<K,V> delegate : delegates) {
+            result = delegate.remove(key);
+            if(result != null) break;
+        }
+        return result;
+    }
+
+    @Override
+    public void putAll(Map<? extends K, ? extends V> m) {
+        this.thisMap.putAll(m);
+    }
+
+    @Override
+    public void clear() {
+        thisMap.clear();
+    }
+
+    @Override
+    public Set<K> keySet() {
+        return flatten().keySet();
+    }
+
+    private Map<K, V> flatten() {
+        Map<K, V> result = mapFactory.get();
+        int i = delegates.size();
+        while(i-->0) {
+            Map<K, V> delegate = delegates.get(i);
+            result.putAll(delegate);
+        }
+        result.putAll(thisMap);
+        return Collections.unmodifiableMap(result);
+    }
+
+    @Override
+    public Collection<V> values() {
+        return flatten().values();
+    }
+
+    @Override
+    public Set<Entry<K, V>> entrySet() {
+        return flatten().entrySet();
+    }
+}
diff --git a/src/main/java9/module-info.java b/src/main/java9/module-info.java
index fdec487..43be8b9 100644
--- a/src/main/java9/module-info.java
+++ b/src/main/java9/module-info.java
@@ -1,3 +1,4 @@
 module net.woggioni.jwo {
+    requires org.slf4j;
     exports net.woggioni.jwo;
 }
\ No newline at end of file