package com.learning.filter;

import java.io.IOException;

import java.io.UnsupportedEncodingException;

import java.util.Enumeration;

import java.util.Map;

import javax.security.auth.message.callback.PrivateKeyCallback.Request;

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.annotation.WebFilter;

import javax.servlet.annotation.WebInitParam;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletRequestWrapper;

import javax.servlet.http.HttpServletResponse;

@WebFilter(urlPatterns = "/*")

public class EncodingFilter implements Filter {

    @Override

    public void destroy() {

    }

    @Override

    public void doFilter(ServletRequest arg0, ServletResponse arg1, FilterChain arg2)

            throws IOException, ServletException {

        // 转换对象

        HttpServletRequest httpServletRequest = (HttpServletRequest) arg0;

        HttpServletResponse httpServletResponse = (HttpServletResponse) arg1;

        httpServletResponse.setContentType("text/html;charset=UTF-8");

        // 对GET方式支持中文提交，可以应用装饰模式或适配器模式 （ 便于观看代码 此类写在本类之下 ）

        httpServletRequest = new MyWrapper(httpServletRequest);

        arg2.doFilter(httpServletRequest, httpServletResponse);

    }

    @Override

    public void init(FilterConfig filterConfig) throws ServletException {

    }

}

/*

 * 装饰模式实现： 1.实现被包装对象的接口 或者 继承被包装对象的自带装饰类 2.声明一个和被包装对象相同的对象 用于传参 3.运用构造函数

 * 4.对需要重写的方法进行重写

 */

class MyWrapper extends HttpServletRequestWrapper {

    private HttpServletRequest request;

    public MyWrapper(HttpServletRequest request) {

        super(request);

        this.request = request;

    }

    @Override

    public String[] getParameterValues(String name) {

        Map<String, String[]> map = getParameterMap();

        String[] values = map.get(name);

        return values;

    }

    @Override

    public String getParameter(String name) {

        Map<String, String[]> map = getParameterMap();

        String[] values = map.get(name);

        if (values==null) {

            return null;

        }

        return values[0];

    }

    private boolean flag = true;

    @Override

    public Map<String, String[]> getParameterMap() {

        String method = request.getMethod();

        if ("post".equalsIgnoreCase(method)) {

            try {

                request.setCharacterEncoding("UTF-8");

                return request.getParameterMap();

            } catch (UnsupportedEncodingException e) {

                e.printStackTrace();

            }

        } else if ("Get".equalsIgnoreCase(method)) {

            // get请求

            Map<String, String[]> parameterMap = request.getParameterMap();

            if (!flag) { // 确保get手动编码逻辑只运行一次

                for (String parameterName : parameterMap.keySet()) {

                    String[] values = parameterMap.get(parameterName);

                    if (values != null) {

                        for (int i = 0; i < values.length; i++) {

                            try {

                                // 处理get乱码

                                values[i] = new String(values[i]

                                        .getBytes("ISO-8859-1"), "utf-8");

                            } catch (UnsupportedEncodingException e) {

                                e.printStackTrace();

                            }

                        }

                    }

                }

                flag = true;

            }

            return parameterMap;

        }

        return super.getParameterMap();

    }

}