package com.loaderman.demo.b_filter_data;

import java.io.IOException;
import java.lang.reflect.InvocationHandler;
import java.lang.reflect.Method;
import java.lang.reflect.Proxy;
import java.util.ArrayList;
import java.util.List;

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;

/**
 * 無效數據過濾
 *
 */
public class DateFilter implements
 
 Filter {

    // 初始化無效數據
    private List<String> dirtyData;
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        // 模擬幾個數據
        dirtyData = new ArrayList<String>();
        dirtyData.add("NND");
        dirtyData.add("炸使館");
    }

    @Override
    
 
public void doFilter(ServletRequest req, ServletResponse res,
                         FilterChain chain) throws IOException, ServletException {

        // 轉型
        final HttpServletRequest request = (HttpServletRequest) req;
        HttpServletResponse response = (HttpServletResponse) res;

        // 一、處理公用業務
        request.setCharacterEncoding("UTF-8");                    // POST提交有效
        response.setContentType("text/html;charset=UTF-8");

        HttpServletRequest proxy =  (HttpServletRequest) Proxy.newProxyInstance(
                request.getClass().getClassLoader(),         // 指定當前使用的累加載器
                new Class[]{HttpServletRequest.class},         // 對目標對象實現的接口類型
                new InvocationHandler() {                    // 事件處理器
                    @Override
                    public Object invoke(Object proxy, Method method, Object[] args)
                            throws Throwable {
                        // 定義方法返回值
                        Object returnValue = null;
                        // 獲取方法名
                        String methodName = method.getName();
                        // 判斷：對getParameter方法進行GET提交中文處理
                        if ("getParameter".equals(methodName)) {

                            // 獲取請求數據值【 <input type="text" name="userName">】
                            String value = request.getParameter(args[0].toString());    // 調用目標對象的方法

                            // 獲取提交方式
                            String methodSubmit = request.getMethod(); // 直接調用目標對象的方法

                            // 判斷如果是GET提交，需要對數據進行處理  (POST提交已經處理過了)
                            if ("GET".equals(methodSubmit)) {
                                if (value != null && !"".equals(value.trim())){
                                    // 處理GET中文
                                    value = new String(value.getBytes("ISO8859-1"),"UTF-8");
                                }
                            }

                            // 中文數據已經處理完： 下面進行無效數據過濾
                            //【如何value中出現dirtyData中數據，用****替換】
                            for (String data : dirtyData) {
                                // 判斷當前輸入數據(value), 是否包含無效數據
                                if (value.contains(data)){
                                    value = value.replace(data, "*****");
                                }
                            }
                            // 處理完編碼、無效數據後的正確數據
                            return value;
                        }
                        else {
                            // 執行request對象的其他方法
                            returnValue = method.invoke(request, args);
                        }

                        return returnValue;
                    }
                });

        // 二、放行 (執行下一個過濾器或者servlet)
        chain.doFilter(proxy, response);        // 傳入代理對象
    }



    @Override
    public void destroy() {

    }
}

package com.loaderman.demo.b_filter_data;

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class DisServlet extends HttpServlet {

    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {

        // 獲取請求數據
        String content = request.getParameter("content");
        // 保存到request
        request.setAttribute("content", "Content：" + content);
        // 轉發
        request.getRequestDispatcher("/dis.jsp").forward(request, response);

    }

    public void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        this.doGet(request, response);
    }

}

 <!-- 2. 無效數據過濾器配置 -->
    <filter>
        <filter-name>dataFilter</filter-name>
        <filter-class>com.loaderman.demo.b_filter_data.DateFilter</filter-class>
    </filter>
    <filter-mapping>
        <filter-name>dataFilter</filter-name>
        <url-pattern>/*</url-pattern>
    </filter-mapping>

過濾器-無效數據過濾