refactor release for ShardingConnection

sharding-jdbc-core/src/main/java/com/dangdang/ddframe/rdb/sharding/jdbc/ShardingConnection.java

@@ -93,17 +93,10 @@ public final class ShardingConnection extends AbstractConnectionAdapter {
      * @param connection 待释放的数据库连接
      */
     public void release(final Connection connection) {
-        Preconditions.checkNotNull(connection);
-        closeConnection(connection);
         connectionMap.values().remove(connection);
-    }
-    
-    private void closeConnection(final Connection connection) {
-        if (null != connection) {
-            try {
-                connection.close();
-            } catch (final SQLException ignored) {
-            }
+        try {
+            connection.close();
+        } catch (final SQLException ignored) {
         }
     }
     

sharding-jdbc-core/src/test/java/com/dangdang/ddframe/rdb/sharding/jdbc/ShardingConnectionTest.java

@@ -36,7 +36,6 @@ import java.util.Map;
 
 import static org.junit.Assert.assertNotSame;
 import static org.junit.Assert.assertSame;
-import static org.junit.Assert.fail;
 
 public final class ShardingConnectionTest {
     
@@ -111,12 +110,4 @@ public final class ShardingConnectionTest {
         connection.release(conn);
         assertNotSame(conn, connection.getConnection(DS_NAME, SQLType.UPDATE));
     }
-    
-    @Test(expected = SQLException.class)
-    public void assertCloseExceptionConnection() throws SQLException {
-        connection.getConnection(DS_NAME, SQLType.SELECT);
-        connection.getConnection(DS_NAME, SQLType.UPDATE);
-        connection.close();
-        fail();
-    }
 }