网上图书商城项目学习笔记-037工具类之BaseServlet及统一中文编码

1.统一中文编码分析

tomcat默认esetISO-8859-1编码，在servlet中，可能通过request的setCharacterEncoding(charset)和response.setContentType("text/html;charset=UTF-8");处理post请求编码,但get请求的编码控制不了，所以，如果请求类型是get，则用装饰者模式把request整个调包

2.EncodingFilter.java

package cn.itcast.filter;

import java.io.IOException;

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;


public class EncodingFilter implements Filter {
    private String charset = "UTF-8";
    @Override
    public void destroy() {}

    @Override
    public void doFilter(ServletRequest request, ServletResponse response,
            FilterChain chain) throws IOException, ServletException {
        HttpServletRequest req = (HttpServletRequest) request;
        if(req.getMethod().equalsIgnoreCase("GET")) {
            if(!(req instanceof GetRequest)) {
                req = new GetRequest(req, charset);//处理get请求编码
            }
        } else {
            req.setCharacterEncoding(charset);//处理post请求编码
        }
        chain.doFilter(req, response);
    }

    @Override
    public void init(FilterConfig fConfig) throws ServletException {
        String charset = fConfig.getInitParameter("charset");
        if(charset != null && !charset.isEmpty()) {
            this.charset = charset;
        }
    }
}

3.GetRequest.java  装饰者模式

package cn.itcast.filter;

import java.io.UnsupportedEncodingException;
import java.util.Enumeration;
import java.util.Map;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletRequestWrapper;

/**
 * 对GET请求参数加以处理！
 * @author qdmmy6
 *
 */
public class GetRequest extends HttpServletRequestWrapper {
    private HttpServletRequest request;
    private String charset;
    
    public GetRequest(HttpServletRequest request, String charset) {
        super(request);
        this.request = request;
        this.charset = charset;
    }

    @Override
    public String getParameter(String name) {
        // 获取参数
        String value = request.getParameter(name);
        if(value == null) return null;//如果为null，直接返回null
        try {
            // 对参数进行编码处理后返回
            return new String(value.getBytes("ISO-8859-1"), charset);
        } catch (UnsupportedEncodingException e) {
            throw new RuntimeException(e);
        }
    }
    
    @SuppressWarnings({ "unchecked", "rawtypes" })
    @Override
    public Map getParameterMap() {
        Map<String,String[]> map = request.getParameterMap();
        if(map == null) return map;
        // 遍历map，对每个值进行编码处理
        for(String key : map.keySet()) {
            String[] values = map.get(key);
            for(int i = 0; i < values.length; i++) {
                try {
                    values[i] = new String(values[i].getBytes("ISO-8859-1"), charset);
                } catch (UnsupportedEncodingException e) {
                    throw new RuntimeException(e);
                }
            }
        }
        // 处理后返回
        return map;
    }
    
    @Override
    public String[] getParameterValues(String name) {
        String[] values = super.getParameterValues(name);
        for(int i = 0; i < values.length; i++) {
            try {
                values[i] = new String(values[i].getBytes("ISO-8859-1"), charset);
            } catch (UnsupportedEncodingException e) {
                throw new RuntimeException(e);
            }
        }
        return values;
    }
}

3.BaseServlet.java

package cn.itcast.servlet;

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

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

/**
 * BaseServlet用来作为其它Servlet的父类
 * 
 * @author qdmmy6
 * 
 *         一个类多个请求处理方法，每个请求处理方法的原型与service相同！ 原型 = 返回值类型 + 方法名称 + 参数列表
 */
@SuppressWarnings("serial")
public class BaseServlet extends HttpServlet {
    @Override
    public void service(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        response.setContentType("text/html;charset=UTF-8");//处理响应编码
        
        /**
         * 1. 获取method参数，它是用户想调用的方法 2. 把方法名称变成Method类的实例对象 3. 通过invoke()来调用这个方法
         */
        String methodName = request.getParameter("method");
        Method method = null;
        /**
         * 2. 通过方法名称获取Method对象
         */
        try {
            method = this.getClass().getMethod(methodName,
                    HttpServletRequest.class, HttpServletResponse.class);
        } catch (Exception e) {
            throw new RuntimeException("您要调用的方法：" + methodName + "它不存在！", e);
        }
        
        /**
         * 3. 通过method对象来调用它
         */
        try {
            String result = (String)method.invoke(this, request, response);
            if(result != null && !result.trim().isEmpty()) {//如果请求处理方法返回不为空
                int index = result.indexOf(":");//获取第一个冒号的位置
                if(index == -1) {//如果没有冒号，使用转发
                    request.getRequestDispatcher(result).forward(request, response);
                } else {//如果存在冒号
                    String start = result.substring(0, index);//分割出前缀
                    String path = result.substring(index + 1);//分割出路径
                    if(start.equals("f")) {//前缀为f表示转发
                        request.getRequestDispatcher(path).forward(request, response);
                    } else if(start.equals("r")) {//前缀为r表示重定向
                        response.sendRedirect(request.getContextPath() + path);
                    }
                }
            }
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
    }
}