做一個解決全站的字元編碼過濾器，過濾器類和配置如下：

過濾器類：

package com.charles.web.filter;

import java.io.IOException;
import java.lang.reflect.Proxy;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
 
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class CharacterEncodingFilter implements Filter {

    public void destroy() {
    }

    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
            
 
throws IOException, ServletException {
        final HttpServletRequest req = (HttpServletRequest) request;
        HttpServletResponse resp = (HttpServletResponse) response;

        HttpServletRequest newRequest = (HttpServletRequest) Proxy.newProxyInstance(req.getClass().getClassLoader(),
                req.getClass().getInterfaces(), (proxy, method, args) 
 
-> {
                    if ("getParameter".equals(method.getName())) {
                        String str = (String) method.invoke(req, args);
                        return new String(str.getBytes("iso8859-1"), "utf-8");
                    }
                    return method.invoke(req, args);
                });

        resp.setContentType("text/html;charset=utf-8");

        chain.doFilter(newRequest, resp);

    }

    public void init(FilterConfig fConfig) throws ServletException {
    }

}

過濾器配置：

<!-- 解決全站亂碼的filter -->
    <filter>
        <display-name>CharacterEncodingFilter</display-name>
        <filter-name>CharacterEncodingFilter</filter-name>
        <filter-class>com.charles.web.filter.CharacterEncodingFilter</filter-class>
    </filter>
    <filter-mapping>
        <filter-name>CharacterEncodingFilter</filter-name>
        <url-pattern>/*</url-pattern>
    </filter-mapping>

但是在前端form的提交方式是get的情況下，得到的仍然是亂碼。

              剛開始一直糾結於過濾器是不是寫錯了，編碼集是不是寫錯了，但是經過測試，並沒有錯，過濾器正常執行，

       最後把new String(str.getBytes("iso8859-1"), "utf-8")改為new String(str.getBytes("utf-8"), "utf-8")後臺就能得到值，不再是亂碼了。最後百度了下，

      說tomcat8預設的編碼集是utf-8，tomcat8之前預設的編碼集是iso-8859-1,恍然大悟......

總結：tomcat7及其版本之前預設的編碼集是iso-8859-1，tomcat8預設的字符集已經是UTF-8，所以不再需要為request.getParameter()的結果進行轉碼，不需要編碼編碼過濾器類了