Java学习路线-49：Servlet过滤器Filter(3)

package util;
import com.mchange.v2.c3p0.ComboPooledDataSource;
import javax.sql.DataSource;
import java.sql.Connection;
import java.sql.SQLException;
public class JdbcUtil {
    // 需要配置c3p0-config.xml
    private static ComboPooledDataSource dataSource = new ComboPooledDataSource();
    // 返回连接对象
    public static Connection getConnection() {
        try {
            return dataSource.getConnection();
        } catch (SQLException e) {
            throw new RuntimeException(e);
        }
    }
    // 返回连接池对象
    public static DataSource getDataSource() {
        return dataSource;
    }
    // 释放连接
    public static void releaseConnection(Connection connection) {
        try {
            connection.close();
        } catch (SQLException e) {
            throw new RuntimeException(e);
        }
    }
}

<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%>
<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c"%>
<h2>图书列表</h2>
分类：
<a href="book?method=findAll">全部</a>
<a href="book?method=findByCategory&category=1">第一类</a>
<a href="book?method=findByCategory&category=2">第二类</a>
<table border="1">
    <tr>
        <th>ID</th>
        <th>书名</th>
        <th>价格</th>
        <th>分类</th>
    </tr>
    <c:forEach items="${bookList}" var="book">
        <tr>
            <td>${book.bid}</td>
            <td>${book.bname}</td>
            <td>${book.price}</td>
            <td>${book.category}</td>
        </tr>
    </c:forEach>
</table>

<dependency>
    <groupId>jstl</groupId>
    <artifactId>jstl</artifactId>
    <version>1.2</version>
</dependency>
<dependency>
    <groupId>taglibs</groupId>
    <artifactId>standard</artifactId>
    <version>1.1.2</version>
</dependency>

<servlet-mapping>
    <servlet-name>BookServlet</servlet-name>
    <url-pattern>/book</url-pattern>
</servlet-mapping>
<servlet>
    <servlet-name>BookServlet</servlet-name>
    <servlet-class>com.pengshiyu.servlet.BookServlet</servlet-class>
</servlet>

<?xml version="1.0" encoding="utf-8"?>
<c3p0-config>
    <!-- 这是默认配置信息 -->
    <default-config>
        <!-- 连接四大参数配置 -->
        <property name="driverClass">com.mysql.cj.jdbc.Driver</property>
        <property name="jdbcUrl">jdbc:mysql://localhost:3306/data</property>
        <property name="user">root</property>
        <property name="password">123456</property>
        <!-- 池参数配置 -->
        <property name="acquireIncrement">2</property>
        <property name="initialPoolSize">2</property>
        <property name="minPoolSize">2</property>
        <property name="maxPoolSize">10</property>
    </default-config>
</c3p0-config>

package com.pengshiyu.filter;
import com.pengshiyu.response.StaticResponse;
import javax.servlet.*;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.File;
import java.io.IOException;
public class CacheFilter implements Filter {
    private FilterConfig config;
    private final String cacheFileName = "cache";
    private String cacheFilePath = null;
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        this.config = filterConfig;
        this.cacheFilePath = this.config.getServletContext().getRealPath(this.cacheFileName);
        File file = new File(this.cacheFilePath);
        if(file.exists()){
            file.mkdir();
        }
    }
    /**
     * 访问路径
     * http://localhost:8080/demo/book?method=findByCategory&category=4
     */
    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse,
                         FilterChain filterChain) throws IOException, ServletException {
        HttpServletRequest request = (HttpServletRequest)servletRequest;
        HttpServletResponse response = (HttpServletResponse)servletResponse;
        String category = request.getParameter("category");
        String filepath = this.cacheFilePath + "/" + category + ".html";
        File file = new File(filepath);
        // 如果页面不存在就缓存页面
        if(!file.exists()){
            StaticResponse staticResponse = new StaticResponse(response, filepath);
            filterChain.doFilter(request, staticResponse);
        }
        System.out.println("文件存在了");
        request.getRequestDispatcher(this.cacheFileName + "/" + category + ".html").forward(request, response);
    }
    @Override
    public void destroy() {
    }
}

package com.pengshiyu.response;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpServletResponseWrapper;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.PrintWriter;
public class StaticResponse extends HttpServletResponseWrapper {
    private PrintWriter pw;
    public StaticResponse(HttpServletResponse response, String filename) throws FileNotFoundException {
        super(response);
        this.pw = new PrintWriter(filename);
    }
    @Override
    public PrintWriter getWriter() throws IOException {
        // 掉包输出流
        return this.pw;
    }
}