解決全站亂碼的過濾器實現-包裝類設計模式的應用

package myself.study.filter;

import java.io.IOException;
import java.util.Map;
import java.util.Set;

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 {

 public void init(FilterConfig filterConfig) throws ServletException {
 }

 public void doFilter(ServletRequest request, ServletResponse response,
   FilterChain chain) throws IOException, ServletException {
  //全站亂碼解決過濾器
  //>響應正文亂碼
  response.setContentType("text/html;charset=utf-8");
  
  //>請求參數亂碼(使用裝飾設計模式對request對象中的獲取參數的方法進行改造)
  HttpServletRequest res = (HttpServletRequest) request;
  MyHttpServletRequest myRes = new MyHttpServletRequest(res);
  
  //放行過濾器
  chain.doFilter(myRes, response);
 }

 public void destroy() {
 }
}

//使用裝飾設計模式對request對象中的獲取參數的方法進行改造
class MyHttpServletRequest extends HttpServletRequestWrapper{
 private HttpServletRequest request = null;
 private boolean isEncode = true;
 public MyHttpServletRequest(HttpServletRequest request) {
  super(request);
  this.request = request;
 }
 
 public String getParameter(String name) {
  return getParameterValues(name) == null? null : getParameterValues(name)[0];
 }
 
 public String[] getParameterValues(String name) {
  return getParameterMap().get(name);
  
 }
 
 public Map<String, String[]> getParameterMap() {
  try {
   //把map中的所有參數值取出來手動編解碼, 再存回map
   String method = request.getMethod();
   if("POST".equals(method)){    //對post請求 的處理
    request.setCharacterEncoding("utf-8");
    return request.getParameterMap();
   }else if("GET".equals(method)){     //對get請求的處理
    //把map中的所有參數值取出來手動編解碼, 再存回map
    Map map = request.getParameterMap();
    if(isEncode){
     Set<Map.Entry<String, String[]>> set = map.entrySet();
     for (Map.Entry<String, String[]> entry : set) {
      String[] vs = entry.getValue();
      for (int i = 0; i < vs.length; i++) {
       vs[i] = new String(vs[i].getBytes("iso8859-1"), "utf-8");
      }
     }
     isEncode = false;
    }
    return map;
   }else{ //其他5種方式, 不處理原樣返回
    return request.getParameterMap();
   }
   
   //return map(沒有亂碼數據的map)
  } catch (Exception e) {
   e.printStackTrace();
   throw new RuntimeException(e);
  }
 }
}

web.xml中的配置

<filter>
  <description>全站亂碼解決過濾器</description>
  <filter-name>EncodingFilter</filter-name>
  <filter-class>myself.study.filter.EncodingFilter</filter-class>
 </filter>
 <filter-mapping>
  <filter-name>EncodingFilter</filter-name> 
  <url-pattern>/*</url-pattern>
 </filter-mapping>