ColumnReader NullPointerException when finding a setSomething() method that is not a property mutator

server/src/main/java/io/spine/server/entity/storage/ColumnReader.java

@@ -20,14 +20,18 @@
 
 package io.spine.server.entity.storage;
 
+import com.google.common.collect.ImmutableSet;
 import io.spine.server.entity.Entity;
 
 import java.beans.BeanInfo;
 import java.beans.IntrospectionException;
 import java.beans.Introspector;
 import java.beans.PropertyDescriptor;
+import java.lang.reflect.Method;
 import java.util.Arrays;
 import java.util.Collection;
+import java.util.Set;
+import java.util.stream.Collectors;
 
 import static com.google.common.base.Preconditions.checkNotNull;
 import static com.google.common.collect.Lists.newLinkedList;
@@ -84,6 +88,7 @@ static ColumnReader forClass(Class<? extends Entity> entityClass) {
      * @throws IllegalStateException
      *         if entity column definitions are incorrect
      */
+    @SuppressWarnings("ConstantConditions")
     Collection<EntityColumn> readColumns() {
         BeanInfo entityDescriptor;
         try {
@@ -92,24 +97,26 @@ Collection<EntityColumn> readColumns() {
             throw new IllegalStateException(e);
         }
 
-        Collection<EntityColumn> entityColumns = newLinkedList();
         PropertyDescriptor[] propertyDescriptors = entityDescriptor.getPropertyDescriptors();
-        Arrays.stream(propertyDescriptors)
-              .filter(ColumnReader::hasAccessor)
-              .filter(ColumnReader::accessorIsAnnotated)
-              .map(PropertyDescriptor::getReadMethod)
-              .forEach(readMethod -> entityColumns.add(EntityColumn.from(readMethod)));
-
-        checkRepeatedColumnNames(entityColumns);
-        return entityColumns;
+
+        Set<EntityColumn> annotatedColumns = Arrays.stream(propertyDescriptors)
+                                               .map(PropertyDescriptor::getReadMethod)
+                                               .filter(ColumnReader::hasAccessor)
+                                               .filter(ColumnReader::accessorIsAnnotated)
+                                               .map(EntityColumn::from)
+                                               .collect(Collectors.toSet());
+
+        checkRepeatedColumnNames(annotatedColumns);
+        return ImmutableSet.copyOf(annotatedColumns);
     }
 
-    private static boolean accessorIsAnnotated(PropertyDescriptor descriptor) {
-        return getAnnotatedVersion(descriptor.getReadMethod()).isPresent();
+    private static boolean accessorIsAnnotated(Method method) {
+        return getAnnotatedVersion(method).isPresent();
     }
 
-    private static boolean hasAccessor(PropertyDescriptor descriptor) {
-        return descriptor.getReadMethod() != null;
+    @SuppressWarnings("ConstantConditions")
+    private static boolean hasAccessor(Method method) {
+        return method != null;
     }
 
     /**
@@ -123,6 +130,7 @@ private static boolean hasAccessor(PropertyDescriptor descriptor) {
      *         if columns contain repeated names
      */
     private void checkRepeatedColumnNames(Iterable<EntityColumn> columns) {
+
         Collection<String> checkedNames = newLinkedList();
         for (EntityColumn column : columns) {
             String columnName = column.getStoredName();

server/src/test/java/io/spine/server/entity/storage/ColumnReaderTest.java

@@ -116,11 +116,11 @@ void fromImplementedInterface() {
     }
 
     @Test
-    @DisplayName("not confuse a `setSomething()` method with a property mutator")
+    @DisplayName("not confuse a setter method with a property mutator")
     void testSetterDeclaringEntity(){
         ColumnReader columnReader = forClass(EntityWithASetterButNoGetter.class);
         Collection<EntityColumn> entityColumns = columnReader.readColumns();
-        assertThat(entityColumns).hasSize(1);
+        assertThat(entityColumns).isEmpty();
     }
 
     @Nested

server/src/test/java/io/spine/server/entity/storage/given/ColumnsTestEnv.java

@@ -69,11 +69,6 @@ protected EntityWithASetterButNoGetter(String id) {
             super(id);
         }
 
-        @Column
-        public Integer getFortyThree(){
-            return 43;
-        }
-
         @SuppressWarnings("WeakerAccess") // Required for a test
         public void setSecretNumber(Integer secretNumber) {
             this.secretNumber = secretNumber;