全站乱码过滤器简单实现

import javax.servlet.*;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletRequestWrapper;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.io.UnsupportedEncodingException;
import java.util.Map;
import java.util.Set;

public class EncodingFilter implements Filter {
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {

    }

    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        //将ServletRequest和ServletResponse强转成其子类
        HttpServletRequest request = (HttpServletRequest) servletRequest;
        HttpServletResponse response = (HttpServletResponse) servletResponse;
        //对request和response对象进行增强，其中，request对象我这里采用了装饰设计模式
        response.setContentType("text/html;charset=utf-8");
        MyRequest myRequest = new MyRequest(request);
        filterChain.doFilter(myRequest,response);
    }

    @Override
    public void destroy() {

    }

    private class MyRequest extends HttpServletRequestWrapper {
        HttpServletRequest request ;
        boolean flag = false;
        public MyRequest(HttpServletRequest request) {
            super(request);
            this.request = request;
        }
        public Map<String, String[]> getParameterMap(){
            //判断当前的请求是什么请求
            String method = request.getMethod();
            if ("post".equalsIgnoreCase(method)){
                //如果是post请求，直接设置
                try {
                    this.request.setCharacterEncoding("utf-8");
                    return this.request.getParameterMap();
                } catch (UnsupportedEncodingException e) {
                    e.printStackTrace();
                    return super.getParameterMap();
                }
            }else if ("get".equalsIgnoreCase(method)){
                //是get请求
                Map<String, String[]> map = this.request.getParameterMap();
                if (map == null){
                    return super.getParameterMap();
                }
                if (flag){
                    return map;
                }
                Set<String> keys = map.keySet();
                for (String key :
                        keys) {
                    String[] values = map.get(key);
                    for (String value :
                            values) {
                        try {
                            value = new String(value.getBytes("iso-8859-1"), "utf-8");
                        } catch (UnsupportedEncodingException e) {
                            e.printStackTrace();
                        }
                    }

                }
                flag = true;
                return map;
            }else{
                return super.getParameterMap();
            }
        }
        public String[] getParameterValues(String name){
            Map<String, String[]> map = this.getParameterMap();
            if(map == null){
                return super.getParameterValues(name);
            }
            String[] strings = map.get(name);
            return strings;
        }

        public String getParameter(String name){
            String[] parameterValues = this.getParameterValues(name);
            if (parameterValues == null){
                return super.getParameter(name);
            }
            return parameterValues[0];
        }

    }
}