Issue #8460 simplify DefaultSessionIdManager start (#8464)

* Issue #8460 check DefaultSessionIdManager is started

demos/demo-jetty-webapp/src/main/java/com/acme/SessionDump.java

@@ -17,6 +17,7 @@ import java.io.IOException;
 import java.io.PrintWriter;
 import java.util.Date;
 import java.util.Enumeration;
+import java.util.UUID;
 import javax.servlet.RequestDispatcher;
 import javax.servlet.ServletConfig;
 import javax.servlet.ServletException;
@@ -75,6 +76,8 @@ public class SessionDump extends HttpServlet
                 session.setAttribute("test", "value");
                 session.setAttribute("obj", new ObjectAttributeValue(System.currentTimeMillis()));
                 session.setAttribute("WEBCL", new MultiMap<>());
+                UUID uuid = UUID.randomUUID();
+                session.setAttribute("uuid", uuid);
             }
             else if (session != null)
             {

jetty-proxy/src/test/java/org/eclipse/jetty/proxy/BalancerServletTest.java

@@ -100,7 +100,6 @@ public class BalancerServletTest
         {
             DefaultSessionIdManager sessionIdManager = new DefaultSessionIdManager(server);
             sessionIdManager.setWorkerName(nodeName);
-            server.setSessionIdManager(sessionIdManager);
         }
 
         return server;

jetty-server/src/main/config/etc/sessions/id-manager.xml

@@ -5,7 +5,6 @@
   <!-- ===================================================================== -->
   <!-- Configure a SessionIdManager                                          -->
   <!-- ===================================================================== -->
-  <Set name="sessionIdManager">
     <New id="idMgr" class="org.eclipse.jetty.server.session.DefaultSessionIdManager">
       <Arg>
         <Ref refid="Server"/>
@@ -32,5 +31,4 @@
        </New>
       </Set>
    </New>
-  </Set>
 </Configure>

jetty-server/src/main/java/org/eclipse/jetty/server/session/DefaultSessionIdManager.java

@@ -15,6 +15,7 @@ package org.eclipse.jetty.server.session;
 
 import java.security.SecureRandom;
 import java.util.HashSet;
+import java.util.Objects;
 import java.util.Random;
 import java.util.Set;
 import java.util.concurrent.atomic.AtomicLong;
@@ -67,7 +68,8 @@ public class DefaultSessionIdManager extends ContainerLifeCycle implements Sessi
      */
     public DefaultSessionIdManager(Server server)
     {
-        _server = server;
+        _server = Objects.requireNonNull(server);
+        _server.setSessionIdManager(this);
     }
 
     /**
@@ -85,7 +87,8 @@ public class DefaultSessionIdManager extends ContainerLifeCycle implements Sessi
      */
     public void setServer(Server server)
     {
-        _server = server;
+        _server = Objects.requireNonNull(server);
+        _server.setSessionIdManager(this);
     }
 
     /**
@@ -270,7 +273,7 @@ public class DefaultSessionIdManager extends ContainerLifeCycle implements Sessi
         }
         return id;
     }
-
+    
     @Override
     public boolean isIdInUse(String id)
     {
@@ -308,9 +311,6 @@ public class DefaultSessionIdManager extends ContainerLifeCycle implements Sessi
     @Override
     protected void doStart() throws Exception
     {
-        if (_server == null)
-            throw new IllegalStateException("No Server for SessionIdManager");
-
         initRandom();
 
         if (_workerName == null)

jetty-server/src/main/java/org/eclipse/jetty/server/session/SessionHandler.java

@@ -426,7 +426,6 @@ public class SessionHandler extends ScopedHandler
                     {
                         Thread.currentThread().setContextClassLoader(serverLoader);
                         _sessionIdManager = new DefaultSessionIdManager(server);
-                        server.setSessionIdManager(_sessionIdManager);
                         server.manage(_sessionIdManager);
                         _sessionIdManager.start();
                     }