Make ResultHandler and ResultContext to generic type.

src/main/java/org/apache/ibatis/executor/result/DefaultMapResultHandler.java

@@ -26,7 +26,7 @@
 /**
  * @author Clinton Begin
  */
-public class DefaultMapResultHandler<K, V> implements ResultHandler {
+public class DefaultMapResultHandler<K, V> implements ResultHandler<V> {
 
   private final Map<K, V> mappedResults;
   private final String mapKey;
@@ -42,9 +42,8 @@ public DefaultMapResultHandler(String mapKey, ObjectFactory objectFactory, Objec
   }
 
   @Override
-  public void handleResult(ResultContext context) {
-    // TODO is that assignment always true?
-    final V value = (V) context.getResultObject();
+  public void handleResult(ResultContext<? extends V> context) {
+    final V value = context.getResultObject();
     final MetaObject mo = MetaObject.forObject(value, objectFactory, objectWrapperFactory);
     // TODO is that assignment always true?
     final K key = (K) mo.getValue(mapKey);

src/main/java/org/apache/ibatis/executor/result/DefaultResultContext.java

@@ -20,9 +20,9 @@
 /**
  * @author Clinton Begin
  */
-public class DefaultResultContext implements ResultContext {
+public class DefaultResultContext<T> implements ResultContext<T> {
 
-  private Object resultObject;
+  private T resultObject;
   private int resultCount;
   private boolean stopped;
 
@@ -33,7 +33,7 @@ public DefaultResultContext() {
   }
 
   @Override
-  public Object getResultObject() {
+  public T getResultObject() {
     return resultObject;
   }
 
@@ -47,7 +47,7 @@ public boolean isStopped() {
     return stopped;
   }
 
-  public void nextResultObject(Object resultObject) {
+  public void nextResultObject(T resultObject) {
     resultCount++;
     this.resultObject = resultObject;
   }

src/main/java/org/apache/ibatis/executor/result/DefaultResultHandler.java

@@ -25,7 +25,7 @@
 /**
  * @author Clinton Begin
  */
-public class DefaultResultHandler implements ResultHandler {
+public class DefaultResultHandler implements ResultHandler<Object> {
 
   private final List<Object> list;
 
@@ -39,7 +39,7 @@ public DefaultResultHandler(ObjectFactory objectFactory) {
   }
 
   @Override
-  public void handleResult(ResultContext context) {
+  public void handleResult(ResultContext<? extends Object> context) {
     list.add(context.getResultObject());
   }
 

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

@@ -68,7 +68,7 @@ public class DefaultResultSetHandler implements ResultSetHandler {
   private final MappedStatement mappedStatement;
   private final RowBounds rowBounds;
   private final ParameterHandler parameterHandler;
-  private final ResultHandler resultHandler;
+  private final ResultHandler<?> resultHandler;
   private final BoundSql boundSql;
   private final TypeHandlerRegistry typeHandlerRegistry;
   private final ObjectFactory objectFactory;
@@ -87,7 +87,7 @@ private static class PendingRelation {
     public ResultMapping propertyMapping;
   }
 
-  public DefaultResultSetHandler(Executor executor, MappedStatement mappedStatement, ParameterHandler parameterHandler, ResultHandler resultHandler, BoundSql boundSql,
+  public DefaultResultSetHandler(Executor executor, MappedStatement mappedStatement, ParameterHandler parameterHandler, ResultHandler<?> resultHandler, BoundSql boundSql,
       RowBounds rowBounds) {
     this.executor = executor;
     this.configuration = mappedStatement.getConfiguration();
@@ -260,7 +260,7 @@ private List<Object> collapseSingleResultList(List<Object> multipleResults) {
   // HANDLE ROWS FOR SIMPLE RESULTMAP
   //
 
-  private void handleRowValues(ResultSetWrapper rsw, ResultMap resultMap, ResultHandler resultHandler, RowBounds rowBounds, ResultMapping parentMapping) throws SQLException {
+  private void handleRowValues(ResultSetWrapper rsw, ResultMap resultMap, ResultHandler<?> resultHandler, RowBounds rowBounds, ResultMapping parentMapping) throws SQLException {
     if (resultMap.hasNestedResultMaps()) {
       ensureNoRowBounds();
       checkResultHandler();
@@ -285,9 +285,9 @@ protected void checkResultHandler() {
     }
   } 
 
-  private void handleRowValuesForSimpleResultMap(ResultSetWrapper rsw, ResultMap resultMap, ResultHandler resultHandler, RowBounds rowBounds, ResultMapping parentMapping)
+  private void handleRowValuesForSimpleResultMap(ResultSetWrapper rsw, ResultMap resultMap, ResultHandler<?> resultHandler, RowBounds rowBounds, ResultMapping parentMapping)
       throws SQLException {
-    DefaultResultContext resultContext = new DefaultResultContext();
+    DefaultResultContext<Object> resultContext = new DefaultResultContext<Object>();
     skipRows(rsw.getResultSet(), rowBounds);
     while (shouldProcessMoreRows(resultContext, rowBounds) && rsw.getResultSet().next()) {
       ResultMap discriminatedResultMap = resolveDiscriminatedResultMap(rsw.getResultSet(), resultMap, null);
@@ -296,20 +296,21 @@ private void handleRowValuesForSimpleResultMap(ResultSetWrapper rsw, ResultMap r
     }
   }
 
-  private void storeObject(ResultHandler resultHandler, DefaultResultContext resultContext, Object rowValue, ResultMapping parentMapping, ResultSet rs) throws SQLException {
+  private void storeObject(ResultHandler<?> resultHandler, DefaultResultContext<Object> resultContext, Object rowValue, ResultMapping parentMapping, ResultSet rs) throws SQLException {
     if (parentMapping != null) {
       linkToParents(rs, parentMapping, rowValue);
     } else {
       callResultHandler(resultHandler, resultContext, rowValue);
     }
   }
 
-  private void callResultHandler(ResultHandler resultHandler, DefaultResultContext resultContext, Object rowValue) {
+  @SuppressWarnings("unchecked" /* because ResultHandler<?> is always ResultHandler<Object>*/)
+  private void callResultHandler(ResultHandler<?> resultHandler, DefaultResultContext<Object> resultContext, Object rowValue) {
     resultContext.nextResultObject(rowValue);
-    resultHandler.handleResult(resultContext);
+    ((ResultHandler<Object>)resultHandler).handleResult(resultContext);
   }
 
-  private boolean shouldProcessMoreRows(ResultContext context, RowBounds rowBounds) throws SQLException {
+  private boolean shouldProcessMoreRows(ResultContext<?> context, RowBounds rowBounds) throws SQLException {
     return !context.isStopped() && context.getResultCount() < rowBounds.getLimit();
   }
 
@@ -758,8 +759,8 @@ private String prependPrefix(String columnName, String prefix) {
   // HANDLE NESTED RESULT MAPS
   //
 
-  private void handleRowValuesForNestedResultMap(ResultSetWrapper rsw, ResultMap resultMap, ResultHandler resultHandler, RowBounds rowBounds, ResultMapping parentMapping) throws SQLException {
-    final DefaultResultContext resultContext = new DefaultResultContext();
+  private void handleRowValuesForNestedResultMap(ResultSetWrapper rsw, ResultMap resultMap, ResultHandler<?> resultHandler, RowBounds rowBounds, ResultMapping parentMapping) throws SQLException {
+    final DefaultResultContext<Object> resultContext = new DefaultResultContext<Object>();
     skipRows(rsw.getResultSet(), rowBounds);
     Object rowValue = null;
     while (shouldProcessMoreRows(resultContext, rowBounds) && rsw.getResultSet().next()) {

src/main/java/org/apache/ibatis/session/ResultContext.java

@@ -18,9 +18,9 @@
 /**
  * @author Clinton Begin
  */
-public interface ResultContext {
+public interface ResultContext<T> {
 
-  Object getResultObject();
+  T getResultObject();
 
   int getResultCount();
 

src/main/java/org/apache/ibatis/session/ResultHandler.java

@@ -18,8 +18,8 @@
 /**
  * @author Clinton Begin
  */
-public interface ResultHandler {
+public interface ResultHandler<T> {
 
-  void handleResult(ResultContext context);
+  void handleResult(ResultContext<? extends T> resultContext);
 
 }

src/main/java/org/apache/ibatis/session/defaults/DefaultSqlSession.java

@@ -92,11 +92,11 @@ public <K, V> Map<K, V> selectMap(String statement, Object parameter, String map
 
   @Override
   public <K, V> Map<K, V> selectMap(String statement, Object parameter, String mapKey, RowBounds rowBounds) {
-    final List<?> list = selectList(statement, parameter, rowBounds);
+    final List<? extends V> list = selectList(statement, parameter, rowBounds);
     final DefaultMapResultHandler<K, V> mapResultHandler = new DefaultMapResultHandler<K, V>(mapKey,
         configuration.getObjectFactory(), configuration.getObjectWrapperFactory());
-    final DefaultResultContext context = new DefaultResultContext();
-    for (Object o : list) {
+    final DefaultResultContext<V> context = new DefaultResultContext<V>();
+    for (V o : list) {
       context.nextResultObject(o);
       mapResultHandler.handleResult(context);
     }