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);
         }
     }
 }