diff --git a/src/main/java/com/example/cosmos_serversb/entities/Group.java b/src/main/java/com/example/cosmos_serversb/entities/Group.java
index 63a76cb..4c98291 100644
--- a/src/main/java/com/example/cosmos_serversb/entities/Group.java
+++ b/src/main/java/com/example/cosmos_serversb/entities/Group.java
@@ -85,7 +85,7 @@
     }
 
     public void addMember(String uId){
-        //User user = new User(uId, uId, "http:test", "sa", "hogehoge");
+        // User user = new User(uId, uId, "http:test", "hogehoge");
         User user = Users.getInstance().getUserById(uId);
         members.add(user);
 //        user.addGroups(this);
diff --git a/src/main/java/com/example/cosmos_serversb/models/Groups.java b/src/main/java/com/example/cosmos_serversb/models/Groups.java
index eb1a084..94873fc 100644
--- a/src/main/java/com/example/cosmos_serversb/models/Groups.java
+++ b/src/main/java/com/example/cosmos_serversb/models/Groups.java
@@ -51,29 +51,22 @@
         String uri = baseURI + AppName + "/groups/" + gId;
         createTestHashMap(gId, uri);
         Group testGroup = new Group(gId, uri, name, uId);
-        Session session = sessionFactory.openSession();
-        session.beginTransaction();
+        Session session = SessionManager.getInstance().getSession();
         session.save(testGroup);
-        session.getTransaction().commit();
-        session.close();
         return testGroup;
     }
 
     public static Group getGroupByGid(String gId){
         Group editGroup;
-        Session session = sessionFactory.openSession();
-        session.beginTransaction();
+        Session session = SessionManager.getInstance().getSession();
         List groupResult = session.createQuery( "from Group" ).list();
         for ( Group group : (List<Group>) groupResult ) {
             editGroup = group;
             if (editGroup.getgId().equals(gId)) {
-                session.getTransaction().commit();
-                session.close();
                 return editGroup;
             }
         }
-        session.getTransaction().commit();
-        session.close();
+
         return null;
     }
 
diff --git a/src/main/java/com/example/cosmos_serversb/resources/GroupsRest.java b/src/main/java/com/example/cosmos_serversb/resources/GroupsRest.java
index 9564c25..2714d23 100644
--- a/src/main/java/com/example/cosmos_serversb/resources/GroupsRest.java
+++ b/src/main/java/com/example/cosmos_serversb/resources/GroupsRest.java
@@ -2,6 +2,7 @@
 
 import com.fasterxml.jackson.core.JsonProcessingException;
 import com.fasterxml.jackson.databind.ObjectMapper;
+import org.hibernate.Session;
 import org.springframework.stereotype.Component;
 
 import javax.ws.rs.*;
@@ -13,95 +14,119 @@
 public class GroupsRest {
     @GET
     public String getGroupsListByUid(@QueryParam("uId") String uId, @QueryParam("token") String token) throws JsonProcessingException{
+        SessionManager.getInstance().getSession();
         ObjectMapper mapper = new ObjectMapper();
         String json = mapper.writeValueAsString(Groups.getInstance().getGroupsListByUid(uId));
+        SessionManager.getInstance().closeSession();
         return json;
     }
 
     @POST
     public String createGroup(@FormParam("name") String name, @FormParam("uId") String uId, @FormParam("token") String token) throws JsonProcessingException{
+        SessionManager.getInstance().getSession();
         ObjectMapper mapper = new ObjectMapper();
         String json = mapper.writeValueAsString(Groups.getInstance().createGroup(name, uId));
+        SessionManager.getInstance().closeSession();
         return json;
     }
 
     @Path("/{gId}")
     @GET
     public String getGroupByGid(@PathParam("gId") String gId, @QueryParam("token") String token) throws JsonProcessingException{
+        SessionManager.getInstance().getSession();
         ObjectMapper mapper = new ObjectMapper();
         String json = mapper.writeValueAsString(Groups.getInstance().getGroupByGid(gId));
+        SessionManager.getInstance().closeSession();
         return json;
     }
 
     @Path("/{gId}")
     @DELETE
     public String deleteGroup(@PathParam("gId") String gId, @FormParam("token") String token) throws JsonProcessingException{
+        SessionManager.getInstance().getSession();
         ObjectMapper mapper = new ObjectMapper();
         String json = mapper.writeValueAsString(Groups.getInstance().deleteGroup(gId));
+        SessionManager.getInstance().closeSession();
         return json;
     }
 
     @Path("/{gId}/members")
     @GET
     public String getGroupMembersListByGid(@PathParam("gId") String gId, @QueryParam("token") String token) throws JsonProcessingException{
+        SessionManager.getInstance().getSession();
         ObjectMapper mapper = new ObjectMapper();
         String json = mapper.writeValueAsString(Groups.getInstance().getMembersListByGid(gId));
+        SessionManager.getInstance().closeSession();
         return json;
     }
 
     @Path("/{gId}/members")
     @POST
     public String addMember(@PathParam("gId") String gId, @FormParam("uId") String uId, @FormParam("token") String token) throws JsonProcessingException{
+        SessionManager.getInstance().getSession();
         ObjectMapper mapper = new ObjectMapper();
         String json = mapper.writeValueAsString(Groups.getInstance().addMember(gId, uId));
+        SessionManager.getInstance().closeSession();
         return json;
     }
 
     @Path("/{gId}/members")
     @DELETE
     public String deleteMember(@PathParam("gId") String gId, @FormParam("uId") String uId, @FormParam("token") String token) throws JsonProcessingException{
+        SessionManager.getInstance().getSession();
         ObjectMapper mapper = new ObjectMapper();
         String json = mapper.writeValueAsString(Groups.getInstance().deleteMember(gId, uId));
+        SessionManager.getInstance().closeSession();
         return json;
     }
 
     @Path("/{gId}/requests")
     @GET
     public String getRequestsListByGid(@PathParam("gId") String gId, @QueryParam("token") String token) throws JsonProcessingException{
+        SessionManager.getInstance().getSession();
         ObjectMapper mapper = new ObjectMapper();
         String json = mapper.writeValueAsString(Groups.getInstance().getRequestsListByGid(gId));
+        SessionManager.getInstance().closeSession();
         return json;
     }
 
     @Path("/{gId}/requests")
     @POST
     public String addRequests(@PathParam("gId") String gId, @FormParam("uId") String uId, @FormParam("product") String product, @FormParam("deadline") String deadline, @FormParam("location") int location, @FormParam("token") String token) throws JsonProcessingException{
+        SessionManager.getInstance().getSession();
         ObjectMapper mapper = new ObjectMapper();
         String json = mapper.writeValueAsString(Groups.getInstance().addRequests(gId, uId, product, deadline, location));
+        SessionManager.getInstance().closeSession();
         return json;
     }
 
     @Path("{gId}/requests/{rId}")
     @GET
     public String getRequestsDetailByGidAndRid(@PathParam("gId") String gId, @PathParam("rId") String rId, @QueryParam("token") String token) throws JsonProcessingException{
+        SessionManager.getInstance().getSession();
         ObjectMapper mapper = new ObjectMapper();
         String json = mapper.writeValueAsString(Groups.getInstance().getRequestDetailByGidAndRid(gId, rId));
+        SessionManager.getInstance().closeSession();
         return json;
     }
 
     @Path("{gId}/requests/{rId}")
     @PUT
     public String updateRequest(@PathParam("gId") String gId, @PathParam("rId") String rId, @FormParam("uId") String uId, @FormParam("product") String product, @FormParam("deadline") String deadline, @FormParam("location") int location, @FormParam("done") boolean done, @FormParam("token") String token) throws JsonProcessingException{
+        SessionManager.getInstance().getSession();
         ObjectMapper mapper = new ObjectMapper();
         String json = mapper.writeValueAsString(Groups.getInstance().updateRequest(gId, rId, uId, product, deadline, location, done));
+        SessionManager.getInstance().closeSession();
         return json;
     }
 
     @Path("{gId}/requests/{rId}")
     @DELETE
     public String deleteRequest(@PathParam("gId") String gId, @PathParam("rId") String rId, @FormParam("token") String token) throws JsonProcessingException{
+        SessionManager.getInstance().getSession();
         ObjectMapper mapper = new ObjectMapper();
         String json = mapper.writeValueAsString(Groups.getInstance().deleteRequest(gId, rId));
+        SessionManager.getInstance().closeSession();
         return json;
     }
 }