Ensure setters are called only once

Author: emacarron

src/main/java/org/apache/ibatis/executor/resultset/NestedResultSetHandler.java

@@ -158,13 +158,16 @@ private boolean applyNestedResultMappings(ResultSet rs, ResultMap resultMap, Met
           final boolean isAncestor = ancestorCache.containsKey(absoluteKey);
           Object rowValue = getRowValue(rs, nestedResultMap, combinedKey, absoluteKey, columnPrefix, resultColumnCache);          
           final Object collectionProperty = instantiateCollectionPropertyIfAppropriate(resultMapping, metaObject); // even if there is no data an empty collection is set
-          if (!knownValue && rowValue != null && anyNotNullColumnHasValue(resultMapping, columnPrefix, rs)) {
+          if (rowValue != null
+              && ((isAncestor && parentIsNew)
+              || (!isAncestor && !knownValue && anyNotNullColumnHasValue(resultMapping, columnPrefix, rs)))) {
             if (collectionProperty != null) {
               final MetaObject targetMetaObject = configuration.newMetaObject(collectionProperty);
               targetMetaObject.add(rowValue);
             } else {
-              if (!parentIsNew && !isAncestor) { 
-                throw new ExecutorException("Trying to set a 1 to 1 child element twice for '" + resultMapping.getProperty() + "'. Check your id properties.");
+              if (!parentIsNew) { 
+                throw new ExecutorException("Trying to orverride a previous set value for the association '" + resultMapping.getProperty() 
+                    + "'. Check your id/result elements to ensure they identify uniquely an record.");
               }
               metaObject.setValue(resultMapping.getProperty(), rowValue);
             }

src/test/java/org/apache/ibatis/submitted/parent_reference_3level/Blog.java

@@ -30,7 +30,7 @@ public int getId() {
     return id;
   }
 
-  public void setId(int id) {
+  public void setId(int id) {    
     this.id = id;
   }
 
@@ -39,6 +39,9 @@ public String getTitle() {
   }
 
   public void setTitle(String title) {
+    if (this.title != null) {
+      throw new RuntimeException("Setter called twice");
+    }
     this.title = title;
   }
 
@@ -47,6 +50,9 @@ public List<Post> getPosts() {
   }
 
   public void setPosts(List<Post> posts) {
+    if (this.posts != null) {
+      throw new RuntimeException("Setter called twice");
+    }
     this.posts = posts;
   }
 }

src/test/java/org/apache/ibatis/submitted/parent_reference_3level/Comment.java

@@ -34,6 +34,9 @@ public Post getPost() {
   }
 
   public void setPost(Post post) {
+    if (this.post != null) {
+      throw new RuntimeException("Setter called twice");
+    }
     this.post = post;
   }
 
@@ -42,6 +45,9 @@ public String getComment() {
   }
 
   public void setComment(String comment) {
+    if (this.comment != null) {
+      throw new RuntimeException("Setter called twice");
+    }    
     this.comment = comment;
   }
 }

src/test/java/org/apache/ibatis/submitted/parent_reference_3level/Post.java

@@ -37,6 +37,9 @@ public Blog getBlog() {
   }
 
   public void setBlog(Blog blog) {
+    if (this.blog != null) {
+      throw new RuntimeException("Setter called twice");
+    }    
     this.blog = blog;
   }
 
@@ -45,6 +48,9 @@ public String getBody() {
   }
 
   public void setBody(String body) {
+    if (this.body != null) {
+      throw new RuntimeException("Setter called twice");
+    }    
     this.body = body;
   }
 
@@ -53,6 +59,9 @@ public List<Comment> getComments() {
   }
 
   public void setComments(List<Comment> comments) {
+    if (this.comments != null) {
+      throw new RuntimeException("Setter called twice");
+    }    
     this.comments = comments;
   }
 }