java web过滤器案列

package com.itheima.filter; import java.io.IOException; import java.util.Map; 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.HttpServletRequestWrapper; public class EncodingFilter implements Filter { private FilterConfig config = null; private String encode = null; public void destroy() { } public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException { response.setContentType("text/html;charset="+encode); //--解决响应乱码 chain.doFilter(new MyHttpServletRequest((HttpServletRequest) request), response);//--包装改造request中和获取请求参数相关的方法解决请求参数乱码 } public void init(FilterConfig filterConfig) throws ServletException { this.config = filterConfig; encode = config.getInitParameter("encode") == null ?"utf-8" :config.getInitParameter("encode"); } class MyHttpServletRequest extends HttpServletRequestWrapper{ private HttpServletRequest request = null; private boolean isNotEncode = true; public MyHttpServletRequest(HttpServletRequest request) { super(request); this.request = request; } @Override public Map getParameterMap() { try{ if(request.getMethod().equalsIgnoreCase("POST")){//--如果是post提交,一行代码解决post提交请求参数乱码 request.setCharacterEncoding(encode); return request.getParameterMap(); }else if(request.getMethod().equalsIgnoreCase("GET")){//--如果是get提交,则应该手动编解码解决乱码 Map<String,String[]> map = request.getParameterMap();//获取有乱码的map if(isNotEncode){//只能在第一次解决乱码 for(Map.Entry<String, String[]> entry : map.entrySet()){//遍历map,解决所有值的乱码 String [] vs = entry.getValue(); for(int i=0;i<vs.length;i++){ vs[i] = new String(vs[i].getBytes("iso8859-1"),encode); } } isNotEncode = false;//设置为false,第二次就不会再进这个代码块了 } return map; }else{ return request.getParameterMap(); } }catch (Exception e) { e.printStackTrace(); throw new RuntimeException(e); } } @Override public String[] getParameterValues(String name) { return (String[]) getParameterMap().get(name); } @Override public String getParameter(String name) { return getParameterValues(name) == null ? null : getParameterValues(name)[0]; } } }