FIX: When saving multiple m2m beans, only last m2m wins (Regression due #1630) (#1638)

* provide test case, that shows problem on multiple-m2m

* FIX: When saving multiple m2m beans, only last m2m wins (Regression due #1630)

src/main/java/io/ebeaninternal/server/core/PersistRequestBean.java

@@ -187,7 +187,7 @@ public final class PersistRequestBean<T> extends PersistRequest implements BeanP
   /**
    * Many to many intersection table changes that are held for later batch processing.
    */
-  private SaveManyBeans saveManyIntersection;
+  private List<SaveManyBeans> saveManyIntersections;
 
   public PersistRequestBean(SpiEbeanServer server, T bean, Object parentBean, BeanManager<T> mgr, SpiTransaction t,
                             PersistExecute persistExecute, PersistRequest.Type type, int flags) {
@@ -965,8 +965,8 @@ public final class PersistRequestBean<T> extends PersistRequest implements BeanP
   }
 
   private void saveQueuedManyIntersection() {
-    if (saveManyIntersection != null) {
-      saveManyIntersection.saveIntersectionBatch();
+    if (saveManyIntersections != null) {
+      saveManyIntersections.forEach(SaveManyBeans::saveIntersectionBatch);
     }
   }
 
@@ -1479,7 +1479,10 @@ public final class PersistRequestBean<T> extends PersistRequest implements BeanP
   /**
    * The intersection table updates to the batch executed later on postExecute.
    */
-  public void setManyIntersection(SaveManyBeans saveManyIntersection) {
-    this.saveManyIntersection = saveManyIntersection;
+  public void addManyIntersection(SaveManyBeans saveManyIntersection) {
+    if (this.saveManyIntersections == null) {
+      this.saveManyIntersections = new ArrayList<>();
+    }
+    this.saveManyIntersections.add(saveManyIntersection);
   }
 }

src/main/java/io/ebeaninternal/server/persist/SaveManyBeans.java

@@ -247,7 +247,7 @@ public class SaveManyBeans extends SaveManyBase {
     if (request.isQueueManyIntersection()) {
       // queue/delay until bean persist request is flushed
       this.deleteMissing = deleteMissingChildren;
-      request.setManyIntersection(this);
+      request.addManyIntersection(this);
     } else {
       saveAssocManyIntersection(deleteMissingChildren, false);
     }

src/test/java/org/tests/sp/TestManyToManySaveTwice.java

@@ -6,11 +6,13 @@ import io.ebean.Ebean;
 import io.ebean.Transaction;
 import org.junit.Test;
 import org.tests.sp.model.car.Car;
+import org.tests.sp.model.car.Door;
 import org.tests.sp.model.car.Wheel;
 
 import java.util.LinkedList;
 import java.util.List;
 
+import static org.assertj.core.api.Assertions.assertThat;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertNotNull;
 
@@ -24,15 +26,24 @@ public class TestManyToManySaveTwice extends BaseTestCase {
     Wheel w0 = new Wheel("wx0");
     Wheel w1 = new Wheel("wx1");
 
+    Door d0 = new Door("dx0");
+    Door d1 = new Door("dx1");
+
     List<Wheel> wheels = new LinkedList<>();
     wheels.add(w0);
     wheels.add(w1);
 
+    List<Door> doors = new LinkedList<>();
+    doors.add(d0);
+    doors.add(d1);
+
     DB.saveAll(wheels);
+    DB.saveAll(doors);
 
     Car c0 = new Car("cx0");
     c0.getWheels().add(w0);
     c0.getWheels().add(w1);
+    c0.getDoors().add(d0);
 
     Car c1 = new Car("cx1");
     c1.getWheels().add(w1);
@@ -45,6 +56,16 @@ public class TestManyToManySaveTwice extends BaseTestCase {
 
       transaction.commit();
     }
+
+    c0 = Ebean.find(Car.class, c0.getId());
+    c1 = Ebean.find(Car.class, c1.getId());
+
+    assertThat(c0.getWheels()).hasSize(2);
+    assertThat(c0.getDoors()).hasSize(1);
+
+    assertThat(c1.getWheels()).hasSize(1);
+    assertThat(c1.getDoors()).hasSize(0);
+
   }
 
 
@@ -101,7 +122,9 @@ public class TestManyToManySaveTwice extends BaseTestCase {
 
   private void delete() {
     DB.sqlUpdate("delete from sp_car_car_wheels").execute();
+    DB.sqlUpdate("delete from sp_car_car_doors").execute();
     DB.sqlUpdate("delete from sp_car_wheel").execute();
+    DB.sqlUpdate("delete from sp_car_door").execute();
     DB.sqlUpdate("delete from sp_car_car").execute();
   }
 }

src/test/java/org/tests/sp/model/car/Car.java

@@ -22,6 +22,10 @@ public class Car extends IdEntity {
   @JoinTable(name = "sp_car_car_wheels", joinColumns = {@JoinColumn(name = "car")}, inverseJoinColumns = {@JoinColumn(name = "wheel")})
   private List<Wheel> wheels;
 
+  @ManyToMany(cascade = CascadeType.ALL)
+  @JoinTable(name = "sp_car_car_doors", joinColumns = {@JoinColumn(name = "car")}, inverseJoinColumns = {@JoinColumn(name = "door")})
+  private List<Door> doors;
+
   public Car(String name) {
     this.name = name;
   }
@@ -37,4 +41,12 @@ public class Car extends IdEntity {
   public void setWheels(List<Wheel> wheels) {
     this.wheels = wheels;
   }
+
+  public List<Door> getDoors() {
+    return doors;
+  }
+
+  public void setDoors(List<Door> doors) {
+    this.doors = doors;
+  }
 }

src/test/java/org/tests/sp/model/car/Door.java

@@ -0,0 +1,23 @@
+package org.tests.sp.model.car;
+
+import org.tests.sp.model.IdEntity;
+
+import javax.persistence.Entity;
+import javax.persistence.Table;
+
+@Entity
+@Table(name = "sp_car_door")
+public class Door extends IdEntity {
+
+  private static final long serialVersionUID = 2399600193947163469L;
+
+  private String name;
+
+  public Door(String name) {
+    this.name = name;
+  }
+
+  public String getName() {
+    return name;
+  }
+}