代碼倉庫地址+文檔:https://gitee.com/DerekAndroid/FilterServlet.git
保存用戶登錄信息效果:
自動登錄’複選框,實現下次進入在一定cookie時間內自動登錄到主頁
案例一:完成自動登錄
需求:當用戶第一次登錄該網站的時候,如果勾選了‘自動登錄’複選框,'保存用戶登錄信息'
那麼關閉瀏覽器後,下次在訪問該網站任何資源的時候,都會顯示用戶在線
技術分析:
session(保證用戶在線)
cookie(保存第一訪問網站的狀態)
filter(到達目標資源之前,完成登錄操作)
案例二:全局統一編碼
需求:在向服務器發送請求的時候,使用filter過濾亂碼問題
技術分析:
filter
對方法增強:
繼承
動態代理
裝飾者模式(靜態代理)
如何使用裝飾者模式:
裝飾者和被裝飾者繼承同一個類或者實現同一個接口
裝飾者中需要有被裝飾者的引用
對需要增強的方法進行增強
對不需要增強的方法,直接使用父類的方法
filter處理編碼亂碼問題
方案1:getParameter
package com.itheima.servlet;
import java.io.IOException;
import java.io.UnsupportedEncodingException;
import java.sql.SQLException;
import java.util.Map;
import java.util.Set;
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.Cookie;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletRequestWrapper;
import javax.servlet.http.HttpServletResponse;
import com.itheima.bean.User;
import com.itheima.service.LoginService;
public class LoginFilter implements Filter {
@Override
public void init(FilterConfig filterConfig) throws ServletException {
// TODO Auto-generated method stub
}
@Override
public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain)
throws IOException, ServletException {
// HttpServletRequest request = (HttpServletRequest)req;
// chain.doFilter(new myCode(request), res);
//把servletReuqest強轉爲HttpServletRequest
HttpServletRequest request = (HttpServletRequest)req;
HttpServletResponse response = (HttpServletResponse)res;
//判斷session中是否有用戶存在
String username1=(String)request.getSession().getAttribute("username");
if(username1!=null){
//放行
// chain.doFilter(request, response);
chain.doFilter(new myCodeParameter(request), res);
return;
}
//獲取所有的cookie
Cookie[] cookies = request.getCookies();
Cookie co = null;
//判斷cookies是否爲null
if(cookies!=null){
//從cookies中查找與usernameAndPwd相匹配的cookie
for(Cookie cookie:cookies){
if("usernameAndPwd".equals(cookie.getName())){
co=cookie;
}
}
}
//判斷是否是第一次登錄
if(co!=null){
//獲取cookie中的用戶名和密碼
String up = co.getValue();
System.out.println(co.getValue());
String[] sp = up.split("-");
String username = sp[0];
String password = sp[1];
//完成自動登錄,調用LoginService
LoginService ls = new LoginService();
try {
User user = ls.getUserByUsernameAndPwd(username, password);
System.out.println("查詢一次數據庫");
if(user!=null){
//保證用戶在線
request.getSession().setAttribute("username", user.getUsername());
}
//放行
// chain.doFilter(request, response);
chain.doFilter(new myCodeParameter(request), res);
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}else{
// chain.doFilter(request, response);
chain.doFilter(new myCodeParameter(request), res);
}
}
@Override
public void destroy() {
// TODO Auto-generated method stub
}
}
class myCodeParameter extends HttpServletRequestWrapper {
public myCodeParameter(HttpServletRequest request) {
super(request);
// TODO Auto-generated constructor stub
}
@Override
public String getParameter(String name) {
String method = super.getMethod();
if("get".equalsIgnoreCase(method)){
// String value = super.getParameter("username");
// try {
// value = new String(value.getBytes("iso-8859-1"),"utf-8");
// } catch (UnsupportedEncodingException e) {
// // TODO Auto-generated catch block
// e.printStackTrace();
// }
// return value;
//返回值有問題,全部攔截了
// username=阿根
// password=阿根
// yzm=阿根
// yzm=阿根
//編碼轉換
String value=super.getParameter(name);
System.out.println("value="+value);
//判斷是參數提交才轉換編碼
if (null!=value) {
try {
value = new String(value.getBytes("iso-8859-1"),"utf-8");
} catch (UnsupportedEncodingException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
return value;
}else if("post".equalsIgnoreCase(method)){
try {
super.setCharacterEncoding("utf-8");
} catch (UnsupportedEncodingException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return super.getParameter(name);
}
return super.getParameter(name);
}
}
方案2:重寫getParameterValues
package com.itheima.servlet;
import java.io.IOException;
import java.io.UnsupportedEncodingException;
import java.util.Map;
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.HttpServletRequestWrapper;
import javax.servlet.http.HttpServletResponse;
/**
* 統一編碼
* @author Administrator
*
*/
public class EncodingFilter implements Filter {
@Override
public void init(FilterConfig filterConfig) throws ServletException {
// TODO Auto-generated method stub
}
@Override
public void doFilter(ServletRequest req, ServletResponse resp, FilterChain chain) throws IOException, ServletException {
//1.強轉
HttpServletRequest request=(HttpServletRequest) req;
HttpServletResponse response=(HttpServletResponse) resp;
//2.放行
chain.doFilter(new MyRequest(request), response);
}
@Override
public void destroy() {
// TODO Auto-generated method stub
}
}
class MyRequest extends HttpServletRequestWrapper{
private HttpServletRequest request;
private boolean flag=true;
public MyRequest(HttpServletRequest request) {
super(request);
this.request=request;
}
@Override
public String getParameter(String name) {
if(name==null || name.trim().length()==0){
return null;
}
String[] values = getParameterValues(name);
if(values==null || values.length==0){
return null;
}
return values[0];
}
@Override
/**
* hobby=[eat,drink]
*/
public String[] getParameterValues(String name) {
if(name==null || name.trim().length()==0){
return null;
}
Map<String, String[]> map = getParameterMap();
if(map==null || map.size()==0){
return null;
}
return map.get(name);
}
@Override
/**
* map{ username=[tom],password=[123],hobby=[eat,drink]}
*/
public Map<String,String[]> getParameterMap() {
/**
* 首先判斷請求方式
* 若爲post request.setchar...(utf-8)
* 若爲get 將map中的值遍歷編碼就可以了
*/
String method = request.getMethod();
if("post".equalsIgnoreCase(method)){
try {
request.setCharacterEncoding("utf-8");
return request.getParameterMap();
} catch (UnsupportedEncodingException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}else if("get".equalsIgnoreCase(method)){
Map<String,String[]> map = request.getParameterMap();
if(flag){
for (String key:map.keySet()) {
String[] arr = map.get(key);
//繼續遍歷數組
for(int i=0;i<arr.length;i++){
//編碼
try {
arr[i]=new String(arr[i].getBytes("iso8859-1"),"utf-8");
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
}
}
}
flag=false;
}
//需要遍歷map 修改value的每一個數據的編碼
return map;
}
return super.getParameterMap();
}
}