public void init(CliShell shell, CliEnvironment env, Terminal terminal, ExecutionContext exeContext) {
    this.env = env;
    executor = env.getExecutor();
    this.terminal = terminal;
    this.writer = terminal.writer();
    this.exeContext = exeContext;
    this.shell = shell;
  }
sets up the member variables
@param shell the {@link CliShell} which uses this CommandHandler
@param env the Shell's {@link CliEnvironment}
@param terminal the {@link Terminal} to print output and messages
@param exeContext the {@link ExecutionContext}
samza-sql-shell/src/main/java/org/apache/samza/sql/client/impl/CliCommandHandler.java