标签：
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：
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：
标签：
原文地址：http://blog.csdn.net/erlian1992/article/details/52215978
