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);
}
}
}