Add some sanity checks when creating sort comparators (#1538)

src/main/java/io/ebeaninternal/server/deploy/BeanDescriptor.java

@@ -61,6 +61,7 @@ import io.ebeaninternal.server.deploy.meta.DeployBeanDescriptor;
 import io.ebeaninternal.server.deploy.meta.DeployBeanPropertyLists;
 import io.ebeaninternal.server.el.ElComparator;
 import io.ebeaninternal.server.el.ElComparatorCompound;
+import io.ebeaninternal.server.el.ElComparatorNoop;
 import io.ebeaninternal.server.el.ElComparatorProperty;
 import io.ebeaninternal.server.el.ElPropertyChainBuilder;
 import io.ebeaninternal.server.el.ElPropertyDeploy;
@@ -2443,7 +2444,15 @@ public class BeanDescriptor<T> implements BeanType<T>, STreeType {
   private ElComparator<T> createPropertyComparator(SortByClause.Property sortProp) {
 
     ElPropertyValue elGetValue = getElGetValue(sortProp.getName());
+    if (elGetValue == null) {
+      logger.error("Sort property [" + sortProp + "] not found in " + beanType + ". Cannot sort.");
+      return new ElComparatorNoop<>();
+    }
 
+    if (elGetValue.isAssocMany()) {
+      logger.error("Sort property [" + sortProp + "] in " + beanType + " is a many-property. Cannot sort.");
+      return new ElComparatorNoop<>();
+    }
     Boolean nullsHigh = sortProp.getNullsHigh();
     if (nullsHigh == null) {
       nullsHigh = Boolean.TRUE;

src/main/java/io/ebeaninternal/server/el/ElComparatorNoop.java

@@ -0,0 +1,23 @@
+package io.ebeaninternal.server.el;
+
+/**
+ * Comparator with no operation for unsortable properties.
+ *
+ * @author Roland Praml, FOCONIS AG
+ *
+ */
+public class ElComparatorNoop<T> implements ElComparator<T> {
+
+  private static final long serialVersionUID = -9060871822183687180L;
+
+  @Override
+  public int compare(T o1, T o2) {
+    return 0;
+  }
+
+  @Override
+  public int compareValue(Object value, T o2) {
+    return 0;
+  }
+
+}

src/main/java/io/ebeaninternal/server/el/ElComparatorProperty.java

@@ -2,6 +2,8 @@ package io.ebeaninternal.server.el;
 
 import java.util.Comparator;
 
+import io.ebean.bean.EntityBean;
+
 /**
  * Comparator based on a ElGetValue.
  */
@@ -42,9 +44,15 @@ public final class ElComparatorProperty<T> implements Comparator<T>, ElComparato
     if (val1 == null) {
       return val2 == null ? 0 : nullOrder;
     }
+    if (elGetValue.isAssocId()) {
+      val1 = elGetValue.getAssocIdValues((EntityBean) val1)[0]; // TODO: compound key not yet supported
+    }
     if (val2 == null) {
       return -1 * nullOrder;
     }
+    if (elGetValue.isAssocId()) {
+      val2 = elGetValue.getAssocIdValues((EntityBean) val2)[0];
+    }
     Comparable c = (Comparable) val1;
     return asc * c.compareTo(val2);
   }

src/main/java/io/ebeaninternal/server/el/ElPropertyChain.java

@@ -266,6 +266,9 @@ public class ElPropertyChain implements ElPropertyValue {
   @Override
   public Object pathGet(Object bean) {
     for (ElPropertyValue aChain : chain) {
+      if (aChain.isAssocMany()) {
+        throw new UnsupportedOperationException("pathGet not supported on [" + expression + "], because " + aChain + " is an assocMany property");
+      }
       bean = aChain.pathGet(bean);
       if (bean == null) {
         return null;