[MNG-7263] use constants instead of copy/paste
diff --git a/maven-core/src/main/java/org/apache/maven/lifecycle/providers/AbstractLifecycleProvider.java b/maven-core/src/main/java/org/apache/maven/lifecycle/providers/AbstractLifecycleProvider.java
index b69f5aa..e167cac 100644
--- a/maven-core/src/main/java/org/apache/maven/lifecycle/providers/AbstractLifecycleProvider.java
+++ b/maven-core/src/main/java/org/apache/maven/lifecycle/providers/AbstractLifecycleProvider.java
@@ -43,7 +43,7 @@
         {
             final int len = pluginBindings.length;
 
-            if ( len < 1 || len % 2 != 0 )
+            if ( len < 2 || len % 2 != 0 )
             {
                 throw new IllegalArgumentException( "Plugin bindings must have more than 0, even count of elements" );
             }
diff --git a/maven-core/src/main/java/org/apache/maven/lifecycle/providers/CleanLifecycleProvider.java b/maven-core/src/main/java/org/apache/maven/lifecycle/providers/CleanLifecycleProvider.java
index 62924cd..93adf1d 100644
--- a/maven-core/src/main/java/org/apache/maven/lifecycle/providers/CleanLifecycleProvider.java
+++ b/maven-core/src/main/java/org/apache/maven/lifecycle/providers/CleanLifecycleProvider.java
@@ -26,12 +26,12 @@
 /**
  * {@code clean} lifecycle provider.
  */
-@Named( "clean" )
+@Named( CleanLifecycleProvider.LIFECYCLE_ID )
 @Singleton
 public final class CleanLifecycleProvider
     extends AbstractLifecycleProvider
 {
-    private static final String LIFECYCLE_ID = "clean";
+    protected static final String LIFECYCLE_ID = "clean";
 
     private static final String[] PHASES = {
         "pre-clean",
diff --git a/maven-core/src/main/java/org/apache/maven/lifecycle/providers/DefaultLifecycleProvider.java b/maven-core/src/main/java/org/apache/maven/lifecycle/providers/DefaultLifecycleProvider.java
index aa6f75c..4e55766 100644
--- a/maven-core/src/main/java/org/apache/maven/lifecycle/providers/DefaultLifecycleProvider.java
+++ b/maven-core/src/main/java/org/apache/maven/lifecycle/providers/DefaultLifecycleProvider.java
@@ -26,12 +26,12 @@
 /**
  * {@code default} lifecycle provider.
  */
-@Named( "default" )
+@Named( DefaultLifecycleProvider.LIFECYCLE_ID )
 @Singleton
 public final class DefaultLifecycleProvider
     extends AbstractLifecycleProvider
 {
-    private static final String LIFECYCLE_ID = "default";
+    protected static final String LIFECYCLE_ID = "default";
 
     private static final String[] PHASES = {
         "validate",
diff --git a/maven-core/src/main/java/org/apache/maven/lifecycle/providers/SiteLifecycleProvider.java b/maven-core/src/main/java/org/apache/maven/lifecycle/providers/SiteLifecycleProvider.java
index 142ac1c..ca21fbf 100644
--- a/maven-core/src/main/java/org/apache/maven/lifecycle/providers/SiteLifecycleProvider.java
+++ b/maven-core/src/main/java/org/apache/maven/lifecycle/providers/SiteLifecycleProvider.java
@@ -26,12 +26,12 @@
 /**
  * {@code site} lifecycle provider.
  */
-@Named( "site" )
+@Named( SiteLifecycleProvider.LIFECYCLE_ID )
 @Singleton
 public final class SiteLifecycleProvider
     extends AbstractLifecycleProvider
 {
-    private static final String LIFECYCLE_ID = "site";
+    protected static final String LIFECYCLE_ID = "site";
 
     private static final String[] PHASES = {
         "pre-site",
diff --git a/maven-core/src/main/java/org/apache/maven/lifecycle/providers/WrapperLifecycleProvider.java b/maven-core/src/main/java/org/apache/maven/lifecycle/providers/WrapperLifecycleProvider.java
index aa383ab..3eac8d1 100644
--- a/maven-core/src/main/java/org/apache/maven/lifecycle/providers/WrapperLifecycleProvider.java
+++ b/maven-core/src/main/java/org/apache/maven/lifecycle/providers/WrapperLifecycleProvider.java
@@ -26,12 +26,12 @@
 /**
  * {@code wrapper} lifecycle provider.
  */
-@Named( "wrapper" )
+@Named( WrapperLifecycleProvider.LIFECYCLE_ID )
 @Singleton
 public final class WrapperLifecycleProvider
     extends AbstractLifecycleProvider
 {
-    private static final String LIFECYCLE_ID = "wrapper";
+    protected static final String LIFECYCLE_ID = "wrapper";
 
     private static final String[] PHASES =
     {