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Java Web学习(36)：Filter学习(三)

2016-08-16 00:38 447 查看

       解决项目字符乱码

       乱码问题说明：基本上在每个Servlet中都要处理乱码问题，所以应该把这个工作放到过滤器中来完成。

       获取请求参数中的乱码问题：

       POST请求：request.setCharacterEncoding("UTF-8");

       GET请求：new String(request.getParamter("xxx").getBytes("ISO-8859-1","UTF-8");

       响应的乱码问题：

       response.setContextType("text/html;charset=UTF-8");

       代码实现：

       EncodingServlet.java

package com.servlet;

import java.io.IOException;
import java.io.PrintWriter;

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

/**
 * Servlet implementation class EncodingServlet
 */
@WebServlet(name="EncodingServlet",urlPatterns={"/EncodingServlet"})
public class EncodingServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
       
    /**
     * @see HttpServlet#HttpServlet()
     */
    public EncodingServlet() {
        super();
        // TODO Auto-generated constructor stub
    }

/**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
*/
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//响应乱码问题
response.setContentType("text/html;charset=UTF-8");

String username = request.getParameter("username");
PrintWriter out =response.getWriter();
out.println(username);
}

/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
*/
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
//响应乱码问题
response.setContentType("text/html;charset=UTF-8");

String username = request.getParameter("username");
PrintWriter out =response.getWriter();
out.println(username);
}

}


       EncoddingRequest.java

package com.filter;

import java.io.UnsupportedEncodingException;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletRequestWrapper;

/**
 * 装饰request
 * @author Administrator
 * @date 2016年8月13日
 */
public class EncodingRequest extends HttpServletRequestWrapper {
private HttpServletRequest req;

public EncodingRequest(HttpServletRequest request) {
super(request);
this.req = request;
}

public String getParameter(String name) {
String value = req.getParameter(name);

//处理编码问题
try {
value = new String(value.getBytes("ISO-8859-1"),"UTF-8");
} catch (UnsupportedEncodingException e) {
throw new RuntimeException(e);
}

return value;
}
}


       EncodingFilter.java

package com.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.annotation.WebFilter;
import javax.servlet.http.HttpServletRequest;

/**
 * Servlet Filter implementation class EncodingFilter
 */
@WebFilter(filterName="EncodingFilter",urlPatterns={"/encode.jsp"})
public class EncodingFilter implements Filter {

/**
     * Default constructor. 
     */
    public EncodingFilter() {
        // TODO Auto-generated constructor stub
    }

/**
* @see Filter#destroy()
*/
public void destroy() {
// TODO Auto-generated method stub
}

/**
* @see Filter#doFilter(ServletRequest, ServletResponse, FilterChain)
*/
public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
        //处理POST请求编码问题
request.setCharacterEncoding("UTF-8");

//处理GET请求编码问题
HttpServletRequest req = (HttpServletRequest)request;
if(req.getMethod().equals("GET")){
EncodingRequest er = new EncodingRequest(req);
chain.doFilter(er, response);
}else if(req.getMethod().equals("POST")) {
   chain.doFilter(request, response);
}

}

/**
* @see Filter#init(FilterConfig)
*/
public void init(FilterConfig fConfig) throws ServletException {
// TODO Auto-generated method stub
}

}


       encode.jsp页面：

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>字符乱码问题</title>
</head>
<body>
        <a href="EncodingServlet?username=张三">GET请求</a>
        <form action="EncodingServlet" method="post"> 
             用户名：<input type="text" name="username"  value="李四"/>
             <input type="submit" value="登录" />
        </form>
</body>
</html>


       运行结果：

       


       使用GET请求：

       


       使用POST请求：

       


       分IP统计网站的访问次数

       网站统计每个IP地址访问本网站的次数说明：因为一个网站可能有多个页面，无论哪个页面被访问，都要统计访

问次数，所以使用过滤器最为方便。

       统计工作需要在所有资源之前都执行，那么就可以放到Filter中了。我们这个过滤器不打算做拦截操作，因为我们

只是用来做统计的。

      装载统计数据的容器：Map<String,Object>，整个网站只需要一个Map即可。

      Map需要在Filter中用来保存数据。

      Map需要在页面使用，打印Map中的数据。

      Map需要使用ServletContextListener在服务器启动时完成创建，并只保存到ServletContext中。

      代码实现：

      IPListener.java

package com.listener;

import java.util.LinkedHashMap;
import java.util.Map;

import javax.servlet.ServletContext;
import javax.servlet.ServletContextEvent;
import javax.servlet.ServletContextListener;
import javax.servlet.annotation.WebListener;

/**
 * Application Lifecycle Listener implementation class IPListener
 *
 */
@WebListener
public class IPListener implements ServletContextListener {

    /**
     * Default constructor. 
     */
    public IPListener() {
        // TODO Auto-generated constructor stub
    }

/**
     * @see ServletContextListener#contextDestroyed(ServletContextEvent)
     */
    public void contextDestroyed(ServletContextEvent arg0)  { 
         // TODO Auto-generated method stub
    }

/**
* 在服务器启动时创建Map，保存到ServletContext
     * @see ServletContextListener#contextInitialized(ServletContextEvent)
     */
    public void contextInitialized(ServletContextEvent servletContextEvent)  { 
    	 //创建Map
         Map<String, Integer> map = new LinkedHashMap<String,Integer>();
         //得到ServletContext
         ServletContext application = servletContextEvent.getServletContext();
         //把map保存到application中
         application.setAttribute("map", map);
         
    }

}


      IPFilter.java

package com.filter;

import java.io.IOException;
import java.util.Map;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.annotation.WebFilter;

/**
 * 从application中获取Map
 * 从request中得到当前客户端的IP
 * 进行统计工作，结果保存到Map中
 */
@WebFilter(filterName="IPFilter",urlPatterns={"/*"})
public class IPFilter implements Filter {

private  FilterConfig confige; 

    /**
     * Default constructor. 
     */
    public IPFilter() {
        // TODO Auto-generated constructor stub
    }

/**
* @see Filter#destroy()
*/
public void destroy() {
// TODO Auto-generated method stub
}

/**
* @see Filter#doFilter(ServletRequest, ServletResponse, FilterChain)
*/
public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
// TODO Auto-generated method stub
// place your code here
//1得到application中的map
ServletContext app = confige.getServletContext();
Map<String, Integer> map = (Map<String, Integer>)app.getAttribute("map");
//2从request中获取当前客户端的IP地址
String ip = request.getRemoteAddr();
//3查看map中的是否存在这个IP对应访问次数，如果存在，把次数+1再保存回去
//如果不存在这个IP，那么说明是第一次访问本站，设置访问次数为1
if(map.containsKey(ip)){
int cnt = map.get(ip);
map.put(ip, cnt+1);
}else {
map.put(ip, 1);
}
//4把map放回到app中
app.setAttribute("map", map);
// 放行
chain.doFilter(request, response);
}

/**
* 在服务器启动时执行此方法，而且只执行一次
* @see Filter#init(FilterConfig)
*/
public void init(FilterConfig fConfig) throws ServletException {
this.confige = fConfig;
}

}


      show.jsp页面：

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!-- 导入JSTL标签库 -->
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>结果页面</title>
</head>
<body>
     <h1 align="center">显示结果</h1>
     <table align="center" width="60%" border="1">
           <tr>
              <td>IP</td>
              <td>次数</td>
           </tr>
           <c:forEach items="${applicationScope.map}" var="entry">
           <tr>
              <td>${entry.key}</td>
              <td>${entry.value}</td>
           </tr>
           </c:forEach>
     </table>
</body>
</html>


      运行结果：

      


      页面静态化

      页面静态化说明：首次访问去数据库获取数据，然后把数据保存到一个HTML页面中。第二次访问以及以后的访

问，就不再去访问数据库了，而是直接显示HTML。

       项目所用数据库：

create database imooc charset utf8;

create table imooc_book(
    bid char(32) primary key,
    bname varchar(100),
    price numeric(10,2),
    category int
)charset utf8;

insert into imooc_book values('b1','JavaSE_1',10,1);
insert into imooc_book values('b2','JavaSE_2',15,1);
insert into imooc_book values('b3','JavaSE_3',20,1);
insert into imooc_book values('b4','JavaSE_4',25,1);

insert into imooc_book values('b5','JavaEE_1',30,2);
insert into imooc_book values('b6','JavaEE_1',35,2);
insert into imooc_book values('b7','JavaEE_1',40,2);

insert into imooc_book values('b8','Java_framework_1',45,3);
insert into imooc_book values('b9','Java_framework_2',50,3);


       整个项目的概述：

       JSP：link.jsp页面：链接页面，四个超链接：1)查看所有、2)查看SE分类、3)查看EE分类、4)查看框架分类

                show.jsp页面：显示查询结果

       servlet：BookServlet的findAll()方法：查看所有图书

                      BookServlet的findByCategory()方法：按分类进行查询

       service：BookService略

       dao：BookDao的List<Book> findAll()方法：从数据查询出所有图书

                 BookDao的List<Book> findByCategory(int category)方法：从数据库分类进行查询

       domain：Book实体类：与数据库相对应

       filter：StaticFilter.java用于判断请求是否为首次请求并作出响应的处理

                   StaticResponse.java生成静态HTML文件

       相关jar包导入：

       


       代码实现：

       Book.java

package com.domain;

/**
 * Book实体类
 * @author Administrator
 * @date 2016年8月16日
 */
public class Book {
private String bid;
private String bname;
private double price;
private int category;

public String getBid() {
return bid;
}

public void setBid(String bid) {
this.bid = bid;
}

public String getBname() {
return bname;
}

public void setBname(String bname) {
this.bname = bname;
}

public double getPrice() {
return price;
}

public void setPrice(double price) {
this.price = price;
}

public int getCategory() {
return category;
}

public void setCategory(int category) {
this.category = category;
}

@Override
public String toString() {
return "Book [bid=" + bid + ", bname=" + bname + ", price=" + price + ", category=" + category + "]";
}

}


       BookDao.java

package com.dao;

import java.sql.SQLException;
import java.util.List;

import org.apache.commons.dbutils.QueryRunner;
import org.apache.commons.dbutils.handlers.BeanListHandler;

import com.domain.Book;

import cn.itcast.jdbc.TxQueryRunner;

public class BookDao {
private QueryRunner qr = new TxQueryRunner();

public List<Book> findAll(){
try {
String sql = "select * from imooc_book";
return qr.query(sql, new BeanListHandler<Book>(Book.class));
} catch (SQLException e) {
throw new RuntimeException();
}
}

public List<Book> findByCategory(int category){
try {
String sql = "select * from imooc_book where category=?";
return qr.query(sql, new BeanListHandler<Book>(Book.class),category);
} catch (SQLException e) {
throw new RuntimeException();
}

}
}


       BookServlet.java

package com.servlet;

import java.io.IOException;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.dao.BookDao;

import cn.itcast.servlet.BaseServlet;

/**
 * Servlet implementation class BookServlet
 */
@WebServlet("/BookServlet")
public class BookServlet extends BaseServlet {

private BookDao bookDao = new BookDao();

public String findAll(HttpServletRequest request,HttpServletResponse response) throws ServletException,IOException{
request.setAttribute("bookList", bookDao.findAll());
return "/show.jsp";//转发
}

public String findByCategory(HttpServletRequest request,HttpServletResponse response) throws ServletException,IOException{
String value = request.getParameter("category");
int category = Integer.parseInt(value);
request.setAttribute("bookList", bookDao.findByCategory(category));
return "/show.jsp";//转发
}
}


       StaticFilter.java

package com.filter;

import java.io.File;
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.annotation.WebFilter;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * Servlet Filter implementation class StaticFilter
 */
@WebFilter(filterName="StaticFilter",urlPatterns = { "/BookServlet" })
public class StaticFilter implements Filter {

private FilterConfig config;

    /**
     * Default constructor. 
     */
    public StaticFilter() {
        // TODO Auto-generated constructor stub
    }

/**
* @see Filter#destroy()
*/
public void destroy() {
// TODO Auto-generated method stub
}

/**
* @see Filter#doFilter(ServletRequest, ServletResponse, FilterChain)
*/
public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
HttpServletRequest req = (HttpServletRequest) request;
HttpServletResponse res = (HttpServletResponse) response;
/*
* 第一次访问时，查找请求对应的HTML页面是否存在，如果存在，重定向到HTML页面
* 如果不存在，放行，把Servlet访问数据库后，输出给客户端的数据保存到一个HTML文件中
* 然后再重定向到HTML页面
*/
        //获取category参数，category有四种可能
   String category = request.getParameter("category");
   String htmlPage = category + ".html";
   String htmlPath = config.getServletContext().getRealPath("/htmls");
   File destFile = new File(htmlPath,htmlPage);
   
   //如果文件存在
   if(destFile.exists()){
   	res.sendRedirect(req.getContextPath() + "/htmls/" + htmlPage);
   	return ;
   }
   
   //如果不存在
   StaticResponse sr = new StaticResponse(res, destFile.getAbsolutePath());
chain.doFilter(request, sr);//放行，即生成HTML文件
//重定向到HTML文件
res.sendRedirect(req.getContextPath() + "/htmls/" + htmlPage);
}

/**
* @see Filter#init(FilterConfig)
*/
public void init(FilterConfig fConfig) throws ServletException {
this.config = fConfig;
}

}


       StaticResponse.jav

package com.filter;

import java.io.FileNotFoundException;
import java.io.PrintWriter;
import java.io.UnsupportedEncodingException;

import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpServletResponseWrapper;

public class StaticResponse extends HttpServletResponseWrapper {
private PrintWriter pw;

/**
* String path：HTML文件路径
* @param response
* @param path
* @throws FileNotFoundException
* @throws UnsupportedEncodingException
*/
public StaticResponse(HttpServletResponse response,String path) throws FileNotFoundException, UnsupportedEncodingException {
super(response);
//创建一个与HTML文件路径绑定在一起的流对象
pw = new PrintWriter(path,"UTF-8");
}

public PrintWriter getWriter(){
//返回一个与HTML绑定在一起的PrintWriter对象
return pw;
}

}


       link.jsp页面：

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>超链接页面</title>
</head>
<body>
     <h1>超链接页面</h1>
     <a href="BookServlet?method=findAll" >查看所有</a><br/>
     <a href="BookServlet?method=findByCategory&category=1" >查看JavaSE</a><br/>
     <a href="BookServlet?method=findByCategory&category=2" >查看JavaEE</a><br/>
     <a href="BookServlet?method=findByCategory&category=3" >查看Java_framework</a><br/>
</body>
</html>


       show.jsp页面：

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<!-- 导入JSTL标签库 -->
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>显示页面</title>
</head>
<body>
     <h1 align="center">图书列表</h1>
     <table border="1" align="center" width="50%">
          <tr>
              <th>图书名称</th>
              <th>图书单价</th>
              <th>图书分类</th>
          </tr>
          <c:forEach items="${bookList}" var="book">
          <tr>
              <td>${book.bname}</td>
              <td>${book.price}</td>
              <c:choose>
                   <c:when test="${book.category eq 1 }">
                         <td style="color:red">JavaSE</td>
                   </c:when>
                   <c:when test="${book.category eq 2 }">
                         <td style="color:blue">JavaEE</td>
                   </c:when>
                   <c:when test="${book.category eq 3 }">
                         <td style="color:green">JavaFramework</td>
                   </c:when>
              </c:choose>
          </tr>
          </c:forEach>
     </table>
</body>
</html>


       运行结果：

       链接页面：

       


       查看所有：

       


       查看JavaSE分类：

       


       查看JavaEE分类：

       


       查看JavaFramework分类：

       


       那么在Tomcat服务器下的webapps中的Book项目中会有静态页面生成：

       


       

      
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