#2157 - ManyToMany mapping to itself results in broken generated SQL DDL when not defining @JoinTable.

ebean-core/src/main/java/io/ebeaninternal/server/deploy/parse/AnnotationAssocManys.java

@@ -5,7 +5,6 @@ import io.ebean.annotation.FetchPreference;
 import io.ebean.annotation.HistoryExclude;
 import io.ebean.annotation.Where;
 import io.ebean.bean.BeanCollection.ModifyListenMode;
-import io.ebean.config.BeanNotRegisteredException;
 import io.ebean.config.NamingConvention;
 import io.ebean.config.TableName;
 import io.ebean.core.type.ScalarType;
@@ -140,15 +139,15 @@ class AnnotationAssocManys extends AnnotationAssoc {
     JoinTable joinTable = get(prop, JoinTable.class);
     if (joinTable != null) {
       if (prop.isManyToMany()) {
-        // expected this
         readJoinTable(joinTable, prop);
-
       } else {
         // OneToMany with @JoinTable
         prop.setO2mJoinTable();
         readJoinTable(joinTable, prop);
         manyToManyDefaultJoins(prop);
       }
+    } else if (prop.isManyToMany()) {
+      checkSelfManyToMany(prop);
     }
 
     if (prop.getMappedBy() != null) {
@@ -181,6 +180,12 @@ class AnnotationAssocManys extends AnnotationAssoc {
     }
   }
 
+  private void checkSelfManyToMany(DeployBeanPropertyAssocMany<?> prop) {
+    if (prop.getTargetType().equals(descriptor.getBeanType())) {
+      throw new IllegalStateException("@ManyToMany mapping for " + prop.getFullBeanName() + " requires explicit @JoinTable with joinColumns & inverseJoinColumns. Refer issue #2157");
+    }
+  }
+
   @SuppressWarnings("unchecked")
   private void readElementCollection(DeployBeanPropertyAssocMany<?> prop, ElementCollection elementCollection) {
 
@@ -430,7 +435,6 @@ class AnnotationAssocManys extends AnnotationAssoc {
   }
 
   private void readToMany(ManyToMany propAnn, DeployBeanPropertyAssocMany<?> manyProp) {
-
     manyProp.setMappedBy(propAnn.mappedBy());
     manyProp.setFetchType(propAnn.fetch());
     setCascadeTypes(propAnn.cascade(), manyProp.getCascadeInfo());
@@ -442,7 +446,6 @@ class AnnotationAssocManys extends AnnotationAssoc {
   }
 
   private void readToOne(OneToMany propAnn, DeployBeanPropertyAssocMany<?> manyProp) {
-
     manyProp.setMappedBy(propAnn.mappedBy());
     manyProp.setFetchType(propAnn.fetch());
     setCascadeTypes(propAnn.cascade(), manyProp.getCascadeInfo());

ebean-core/src/test/java/org/tests/model/interfaces/SelfManyMany.java

@@ -0,0 +1,40 @@
+package org.tests.model.interfaces;
+
+import javax.persistence.Entity;
+import javax.persistence.Id;
+import javax.persistence.JoinColumn;
+import javax.persistence.JoinTable;
+import javax.persistence.ManyToMany;
+import java.util.List;
+
+@Entity
+public class SelfManyMany {
+
+  @Id
+  private long id;
+
+  private final String name;
+
+  @ManyToMany
+  // requires explicit @JoinTable
+  @JoinTable(name = "self_many_bridge",
+    joinColumns = @JoinColumn(name = "self_1_id"),
+    inverseJoinColumns = @JoinColumn(name = "self_2_id"))
+  private List<SelfManyMany> related;
+
+  public SelfManyMany(String name) {
+    this.name = name;
+  }
+
+  public long getId() {
+    return id;
+  }
+
+  public String getName() {
+    return name;
+  }
+
+  public List<SelfManyMany> getRelated() {
+    return related;
+  }
+}

ebean-core/src/test/java/org/tests/model/interfaces/TestSelfMany.java

@@ -0,0 +1,15 @@
+package org.tests.model.interfaces;
+
+import io.ebean.BaseTestCase;
+import io.ebean.DB;
+import org.junit.Test;
+
+public class TestSelfMany extends BaseTestCase {
+
+  @Test
+  public void self_manyToMany() {
+
+    SelfManyMany m = new SelfManyMany("1");
+    DB.save(m);
+  }
+}