code: @Test public void getSessionInvalidCharacters(){
    HttpServerExchange exchange=new HttpServerExchange(null);
    SessionConfig config=mock(SessionConfig.class);
    String sessionId="session+";
    when(config.findSessionId(exchange)).thenReturn(sessionId);
    io.undertow.server.session.Session sessionAdapter=this.adapter.getSession(exchange,config);
    assertNull(sessionAdapter);
    sessionAdapter=this.adapter.getSession(sessionId);
    assertNull(sessionAdapter);
    verify(this.manager,never()).findSession(sessionId);
  }
  