Servlet Filter 示例

1. CityQuery.java

package com.xxx.servlet;

import com.google.common.collect.Lists;
import com.xxx.data.HotelInfo;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.util.List;

/**
 * Created with IntelliJ IDEA.
 * User: zhenwei.liu
 * Date: 13-7-15
 * Time: 下午7:39
 * To change this template use File | Settings | File Templates.
 */
public class CityQuery extends HttpServlet {
    private static String PAGE_NO = "pageNo";
    private static String PAGE_SIZE = "pageSize";
    private static String CITY = "city";

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        String city = req.getParameter(CITY);
        String pageNo = req.getParameter(PAGE_NO);
        String pageSize = req.getParameter(PAGE_SIZE);

        if (city == null || city.equals("")
                || pageNo == null || pageNo.equals("")
                || pageSize == null || pageSize.equals(""))
            resp.getWriter().println("参数缺失");

        // 筛选城市
        List<String> hotelList = Lists.newArrayList();
        HotelInfo hotelInfo = HotelInfo.getInstance();
        for (String hotelCode : hotelInfo.getHotelInfo().keySet()) {
            if (hotelCode.contains(city))
                hotelList.add(hotelInfo.getHotelInfo().get(hotelCode));
        }

        // 分页
        int pageSizeInt = Integer.valueOf(pageSize);
        int pageNoInt = Integer.valueOf(pageNo);
        int startIndex = pageSizeInt * (pageNoInt - 1);
        int endIndex = startIndex + pageSizeInt;
        if (startIndex < 0)
            startIndex = 0;
        if (startIndex > hotelList.size() - 1)
            startIndex = hotelList.size() - 1;
        if (endIndex > hotelList.size() - 1)
            endIndex = hotelList.size() - 1;

        hotelList = hotelList.subList(startIndex, endIndex + 1);
        resp.getWriter().println("City: " + city);
        resp.getWriter().println("Page: " + pageNo);
        resp.getWriter().println("PageSize: " + pageSize);
        for (String hotel : hotelList)
            resp.getWriter().println(hotel);
    }
}

2.HotelQuery.java

package com.xxx.servlet;

import com.google.common.base.Charsets;
import com.google.common.base.Splitter;
import com.google.common.collect.Lists;
import com.google.common.collect.Maps;
import com.google.common.io.Files;
import com.google.common.io.LineProcessor;
import com.xxx.data.HotelInfo;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.File;
import java.io.IOException;
import java.util.List;
import java.util.Map;

/**
 * Created with IntelliJ IDEA.
 * User: zhenwei.liu
 * Date: 13-7-15
 * Time: 下午5:27
 * To change this template use File | Settings | File Templates.
 */
public class HotelQuery extends HttpServlet {
    private static String SEQ = "seq";

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        String hotelCode = req.getParameter(SEQ);
        HotelInfo hotelInfo = HotelInfo.getInstance();
        if (hotelCode == null || hotelCode.equals(""))
            resp.getWriter().println("参数缺失");
        else
            resp.getWriter().println(hotelCode + " " + hotelInfo.getHotelInfo().get(hotelCode));
    }
}

3.WhiteListFilter

package com.xxx.filter;

import com.google.common.io.Files;
import com.xxx.data.WhiteList;
import com.xxx.util.HttpTools;

import javax.servlet.*;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import java.io.IOException;
import java.util.List;

/**
 * Created with IntelliJ IDEA.
 * User: zhenwei.liu
 * Date: 13-7-15
 * Time: 下午11:19
 * To change this template use File | Settings | File Templates.
 */
public class WhiteListFilter implements Filter {
    private static String IP = "ip";

    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
    }

    /**
     * 过滤白名单
     *
     * @param servletRequest
     * @param servletResponse
     * @param filterChain
     * @throws IOException
     * @throws ServletException
     */
    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        HttpServletRequest req = (HttpServletRequest) servletRequest;
        HttpServletResponse resp = (HttpServletResponse) servletResponse;
        String ip = HttpTools.getRemoteAddress(req);
        WhiteList whiteList = WhiteList.getInstance();
        if (!whiteList.getWhiteList().contains(ip)) {
            resp.setCharacterEncoding("UTF-8");
            resp.getWriter().println("您的IP受限");
        } else {
            resp.setCharacterEncoding("UTF-8");
            filterChain.doFilter(req, resp);
        }
    }

    @Override
    public void destroy() {
    }

}

4.HotelInfo.java

package com.xxx.data;

import com.google.common.base.Charsets;
import com.google.common.base.Splitter;
import com.google.common.collect.Lists;
import com.google.common.collect.Maps;
import com.google.common.io.Files;
import com.google.common.io.LineProcessor;

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

/**
 * Created with IntelliJ IDEA.
 * User: zhenwei.liu
 * Date: 13-7-15
 * Time: 下午7:40
 * To change this template use File | Settings | File Templates.
 */
public class HotelInfo {
    private static String INFO_FILENAME = HotelInfo.class.getClassLoader().getResource("hotelinfo.txt").getPath();
    private Map<String, String> hotelInfo;    // 酒店列表静态数据
    private static HotelInfo instance;
    private static Object lock = new Object();  // 锁对象

    public Map<String, String> getHotelInfo() {
        return hotelInfo;
    }

    public static HotelInfo getInstance() {
        if (instance == null) {
            synchronized (lock) {
                if (instance == null) {
                    instance = new HotelInfo();
                    instance.hotelInfo = Maps.newHashMap();
                    // 初始化酒店信息,读入Map中
                    File file = new File(INFO_FILENAME);
                    try {
                        // 读取文件同时处理每行数据
                        Files.readLines(file, Charsets.UTF_8, new LineProcessor<List<String>>() {
                            @Override
                            public boolean processLine(String s) throws IOException {
                                // 使用正则切分空字符
                                List<String> data = Lists.newArrayList(
                                        Splitter.onPattern("\\s").trimResults().omitEmptyStrings().split(s));
                                instance.hotelInfo.put(data.get(0), data.get(1));
                                return true;
                            }

                            @Override
                            public List<String> getResult() {
                                return null;
                            }
                        });
                    } catch (IOException ex) {
                        ex.printStackTrace();
                    }
                }
            }
        }
        return instance;
    }
}

5.WhiteList.java

package com.xxx.data;

import com.google.common.base.Charsets;
import com.google.common.io.Files;

import java.io.File;
import java.io.IOException;
import java.util.List;

/**
 * Created with IntelliJ IDEA.
 * User: zhenwei.liu
 * Date: 13-7-15
 * Time: 下午11:39
 * To change this template use File | Settings | File Templates.
 */
public class WhiteList {
    private static String WHITE_LIST_FILENAME = WhiteList.class.getClassLoader().getResource("whitelist.txt").getPath();
    ;
    private List<String> whiteList;   // 白名单静态数据
    private static WhiteList instance;
    private static Object lock = new Object();

    public static WhiteList getInstance() {
        if (instance == null) {
            synchronized (lock) {
                if (instance == null) {
                    instance = new WhiteList();
                    File file = new File(WHITE_LIST_FILENAME);
                    try {
                        instance.whiteList = Files.readLines(file, Charsets.UTF_8);
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                }
            }
        }
        return instance;
    }

    public List<String> getWhiteList() {
        return whiteList;
    }
}

7.web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns="http://java.sun.com/xml/ns/j2ee"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd"
         version="2.4">
    <display-name>Servlet Test</display-name>
    <description>
        Servlet Test
    </description>
    <servlet>
        <servlet-name>hotelQuery</servlet-name>
        <servlet-class>com.xxx.servlet.HotelQuery</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>hotelQuery</servlet-name>
        <url-pattern>/hotelQuery</url-pattern>
    </servlet-mapping>
    <servlet>
        <servlet-name>cityQuery</servlet-name>
        <servlet-class>com.xxx.servlet.CityQuery</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>cityQuery</servlet-name>
        <url-pattern>/cityQuery</url-pattern>
    </servlet-mapping>

    <!-- 白名单filter配置 -->
    <filter>
        <filter-name>WhiteListFilter</filter-name>
        <filter-class>com.xxx.filter.WhiteListFilter</filter-class>
    </filter>
    <filter-mapping>
        <filter-name>WhiteListFilter</filter-name>
        <url-pattern>/*</url-pattern>
    </filter-mapping>
</web-app>

8.pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>ServletTest</groupId>
    <artifactId>ServletTest</artifactId>
    <version>1.0-SNAPSHOT</version>

    <parent>
        <groupId>xxx.common</groupId>
        <artifactId>xxx-supom-generic</artifactId>
        <version>1.2.32</version>
    </parent>

    <dependencies>
        <!-- servlet -->
        <dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>servlet-api</artifactId>
        </dependency>

        <dependency>
            <groupId>javax.servlet</groupId>
            <artifactId>jstl</artifactId>
        </dependency>

        <dependency>
            <groupId>com.google.guava</groupId>
            <artifactId>guava</artifactId>
        </dependency>

    </dependencies>

</project>