编写一个过滤器MyFilter实现以下功能： 1）按照utf-8字符集处理请求和响应中字符； 2）实现跨域访问

编写一个名为MyFilter的过滤器，用于处理UTF-8字符并支持跨域访问，可以基于Spring MVC框架来做，因为Spring MVC的Filter机制允许自定义请求处理流程。以下是一个简单的例子，假设你已经在项目中配置了Spring WebMVC和Spring Security:

import javax.servlet.*;
import javax.servlet.http.HttpServletRequest;
import java.io.IOException;

public class MyFilter implements Filter {

    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
        // 设置UTF-8字符编码
        HttpServletRequest httpRequest = (HttpServletRequest) request;
        httpRequest.setCharacterEncoding("UTF-8");
        httpResponse.setContentType("application/json; charset=UTF-8");

        // 跨域访问设置
        HttpServletResponse httpResponse = (HttpServletResponse) response;
        httpResponse.setHeader("Access-Control-Allow-Origin", "*"); // 允许所有来源
        httpResponse.setHeader("Access-Control-Allow-Methods", "GET, POST, OPTIONS");
        httpResponse.setHeader("Access-Control-Max-Age", "3600");
        httpResponse.setHeader("Access-Control-Allow-Headers", "Content-Type, Authorization");

        // 如果请求是OPTIONS预检请求，则直接返回
        if ("OPTIONS".equals(request.getMethod())) {
            httpResponse.setStatus(HttpServletResponse.SC_OK);
            return;
        }

        chain.doFilter(request, response);
    }

    @Override
    public void init(FilterConfig filterConfig) {}

    @Override
    public void destroy() {}
}

在这个例子中，`doFilter`方法首先设置了请求和响应的UTF-8字符编码，然后添加了必要的HTTP头信息来允许跨域访问。当接收到OPTIONS请求时，这是浏览器在实际发送请求前发出的检查请求，我们简单地返回状态码200以确认支持。