DefaultCursor could invoke method of a closed ResultSet on DB2.

Should fix mybatis#1345 .

src/main/java/org/apache/ibatis/cursor/defaults/DefaultCursor.java

@@ -139,9 +139,12 @@ protected T fetchNextObjectFromDatabase() {
       return null;
     }
 
+    final boolean resultSetClosed;
     try {
       status = CursorStatus.OPEN;
       resultSetHandler.handleRowValues(rsw, resultMap, objectWrapperResultHandler, RowBounds.DEFAULT, null);
+      // ResultSet might have been closed by the driver (e.g. DB2).
+      resultSetClosed = rsw.getResultSet().isClosed();
     } catch (SQLException e) {
       throw new RuntimeException(e);
     }
@@ -151,7 +154,7 @@ protected T fetchNextObjectFromDatabase() {
       indexWithRowBound++;
     }
     // No more object or limit reached
-    if (next == null || getReadItemsCount() == rowBounds.getOffset() + rowBounds.getLimit()) {
+    if (resultSetClosed || next == null || getReadItemsCount() == rowBounds.getOffset() + rowBounds.getLimit()) {
       close();
       status = CursorStatus.CONSUMED;
     }

src/test/java/org/apache/ibatis/cursor/defaults/DefaultCursorTest.java

@@ -0,0 +1,200 @@
+/**
+ *    Copyright 2009-2018 the original author or authors.
+ *
+ *    Licensed under the Apache License, Version 2.0 (the "License");
+ *    you may not use this file except in compliance with the License.
+ *    You may obtain a copy of the License at
+ *
+ *       http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *    Unless required by applicable law or agreed to in writing, software
+ *    distributed under the License is distributed on an "AS IS" BASIS,
+ *    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *    See the License for the specific language governing permissions and
+ *    limitations under the License.
+ */
+
+package org.apache.ibatis.cursor.defaults;
+
+import static org.junit.Assert.*;
+import static org.mockito.Mockito.*;
+
+import java.sql.Connection;
+import java.sql.DatabaseMetaData;
+import java.sql.ResultSet;
+import java.sql.ResultSetMetaData;
+import java.sql.SQLException;
+import java.sql.Statement;
+import java.sql.Types;
+import java.util.ArrayList;
+import java.util.HashMap;
+import java.util.Iterator;
+import java.util.List;
+import java.util.Map;
+
+import org.apache.ibatis.builder.StaticSqlSource;
+import org.apache.ibatis.executor.Executor;
+import org.apache.ibatis.executor.parameter.ParameterHandler;
+import org.apache.ibatis.executor.resultset.DefaultResultSetHandler;
+import org.apache.ibatis.executor.resultset.ResultSetWrapper;
+import org.apache.ibatis.mapping.BoundSql;
+import org.apache.ibatis.mapping.MappedStatement;
+import org.apache.ibatis.mapping.ResultMap;
+import org.apache.ibatis.mapping.ResultMapping;
+import org.apache.ibatis.mapping.SqlCommandType;
+import org.apache.ibatis.session.Configuration;
+import org.apache.ibatis.session.ResultHandler;
+import org.apache.ibatis.session.RowBounds;
+import org.apache.ibatis.type.TypeHandlerRegistry;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.mockito.Mock;
+import org.mockito.Spy;
+import org.mockito.junit.MockitoJUnitRunner;
+
+@RunWith(MockitoJUnitRunner.class)
+public class DefaultCursorTest {
+  @Spy
+  private ImpatientResultSet rs;
+  @Mock
+  protected ResultSetMetaData rsmd;
+  @Mock
+  private Connection conn;
+  @Mock
+  private DatabaseMetaData dbmd;
+  @Mock
+  private Statement stmt;
+
+  @SuppressWarnings("unchecked")
+  @Test
+  public void shouldCloseImmediatelyIfResultSetIsClosed() throws Exception {
+    final MappedStatement ms = getNestedAndOrderedMappedStatement();
+    final ResultMap rm = ms.getResultMaps().get(0);
+
+    final Executor executor = null;
+    final ParameterHandler parameterHandler = null;
+    final ResultHandler<?> resultHandler = null;
+    final BoundSql boundSql = null;
+    final RowBounds rowBounds = RowBounds.DEFAULT;
+
+    final DefaultResultSetHandler resultSetHandler = new DefaultResultSetHandler(executor, ms, parameterHandler,
+      resultHandler, boundSql, rowBounds);
+
+    when(stmt.getResultSet()).thenReturn(rs);
+    when(rsmd.getColumnCount()).thenReturn(2);
+    when(rsmd.getColumnLabel(1)).thenReturn("id");
+    when(rsmd.getColumnType(1)).thenReturn(Types.INTEGER);
+    when(rsmd.getColumnClassName(1)).thenReturn(Integer.class.getCanonicalName());
+    when(rsmd.getColumnLabel(2)).thenReturn("role");
+    when(rsmd.getColumnType(2)).thenReturn(Types.VARCHAR);
+    when(rsmd.getColumnClassName(2)).thenReturn(String.class.getCanonicalName());
+    when(stmt.getConnection()).thenReturn(conn);
+    when(conn.getMetaData()).thenReturn(dbmd);
+    when(dbmd.supportsMultipleResultSets()).thenReturn(false);
+
+    final ResultSetWrapper rsw = new ResultSetWrapper(rs, ms.getConfiguration());
+
+    try (DefaultCursor<?> cursor = new DefaultCursor<>(resultSetHandler, rm, rsw, RowBounds.DEFAULT)) {
+      Iterator<?> iter = cursor.iterator();
+      assertTrue(iter.hasNext());
+      Map<String, Object> map = (Map<String, Object>) iter.next();
+      assertEquals(Integer.valueOf(1), map.get("id"));
+      assertEquals("CEO", ((Map<String, Object>) map.get("roles")).get("role"));
+      assertTrue(cursor.isConsumed());
+      assertFalse(cursor.isOpen());
+      assertFalse(iter.hasNext());
+    }
+  }
+
+  @SuppressWarnings("serial")
+  private MappedStatement getNestedAndOrderedMappedStatement() {
+    final Configuration config = new Configuration();
+    final TypeHandlerRegistry registry = config.getTypeHandlerRegistry();
+
+    ResultMap nestedResultMap = new ResultMap.Builder(config, "roleMap", HashMap.class,
+      new ArrayList<ResultMapping>() {
+        {
+          add(new ResultMapping.Builder(config, "role", "role", registry.getTypeHandler(String.class))
+            .build());
+        }
+      }).build();
+    config.addResultMap(nestedResultMap);
+
+    return new MappedStatement.Builder(config, "selectPerson", new StaticSqlSource(config, "select person..."),
+      SqlCommandType.SELECT).resultMaps(
+        new ArrayList<ResultMap>() {
+          {
+            add(new ResultMap.Builder(config, "personMap", HashMap.class, new ArrayList<ResultMapping>() {
+              {
+                add(new ResultMapping.Builder(config, "id", "id", registry.getTypeHandler(Integer.class))
+                  .build());
+                add(new ResultMapping.Builder(config, "roles").nestedResultMapId("roleMap").build());
+              }
+            }).build());
+          }
+        })
+        .resultOrdered(true)
+        .build();
+  }
+
+  /*
+   * Simulate a driver that closes ResultSet automatically when next() returns false (e.g. DB2).
+   */
+  protected abstract class ImpatientResultSet implements ResultSet {
+    private int rowIndex = -1;
+    private List<Map<String, Object>> rows = new ArrayList<>();
+
+    protected ImpatientResultSet() {
+      Map<String, Object> row = new HashMap<>();
+      row.put("id", Integer.valueOf(1));
+      row.put("role", "CEO");
+      rows.add(row);
+    }
+
+    @Override
+    public boolean next() throws SQLException {
+      throwIfClosed();
+      return ++rowIndex < rows.size();
+    }
+
+    @Override
+    public boolean isClosed() throws SQLException {
+      return rowIndex >= rows.size();
+    }
+
+    @Override
+    public String getString(String columnLabel) throws SQLException {
+      throwIfClosed();
+      return (String) rows.get(rowIndex).get(columnLabel);
+    }
+
+    @Override
+    public int getInt(String columnLabel) throws SQLException {
+      throwIfClosed();
+      return (Integer) rows.get(rowIndex).get(columnLabel);
+    }
+
+    @Override
+    public boolean wasNull() throws SQLException {
+      throwIfClosed();
+      return false;
+    }
+
+    @Override
+    public ResultSetMetaData getMetaData() throws SQLException {
+      return rsmd;
+    }
+
+    @Override
+    public int getType() throws SQLException {
+      throwIfClosed();
+      return ResultSet.TYPE_FORWARD_ONLY;
+    }
+
+    private void throwIfClosed() throws SQLException {
+      if (rowIndex >= rows.size()) {
+        throw new SQLException("Invalid operation: result set is closed.");
+      }
+    }
+  }
+}