拦截器如下：

public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception {
    PrintWriter writer=response.getWriter();
    response.setContentType("application/json;charset=UTF-8");
    response.setCharacterEncoding("UTF-8");
    writer.println("{\"language\":\"简体中文\"}");
    writer.flush();
    writer.close();
    return false;
}

上面返回时，中文只显示几个问号。Controller里返回的中文是不会乱码的。什么回事呢？