Java爬虫学习:利用HttpClient和Jsoup库实现简单的Java爬虫程序

利用HttpClient和Jsoup库实现简单的Java爬虫程序

HttpClient简介

HttpClient是Apache Jakarta Common下的子项目，可以用来提供高效的、最新的、功能丰富的支持HTTP协议的客户端编程工具包，并且它支持 HTTP 协议最新的版本。它的主要功能有：

• (1) 实现了所有 HTTP 的方法（GET,POST,PUT,HEAD 等）
• (2) 支持自动转向
• (3) 支持 HTTPS 协议
• (4) 支持代理服务器等

Jsoup简介

jsoup是一款Java的HTML解析器，可直接解析某个URL地址、HTML文本内容。它提供了一套非常省力的API，可通过DOM，CSS以及类似于jQuery的操作方法来取出和操作数据。它的主要功能有：
- (1) 从一个URL，文件或字符串中解析HTML；
- (2) 使用DOM或CSS选择器来查找、取出数据；
- (3) 可操作HTML元素、属性、文本；

使用步骤

maven项目添加依赖

pom.xml文件依赖如下：

<dependency>
    <groupId>org.apache.httpcomponentsgroupId>
    <artifactId>httpclientartifactId>
    <version>4.5.2version>
dependency>

<dependency>
    <groupId>org.jsoupgroupId>
    <artifactId>jsoupartifactId>
    <version>1.8.3version>
dependency>

编写Junit测试代码

代码

import org.apache.http.HttpEntity;
import org.apache.http.client.config.RequestConfig;
import org.apache.http.client.methods.CloseableHttpResponse;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.client.protocol.HttpClientContext;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClientBuilder;
import org.apache.http.util.EntityUtils;
import org.jsoup.Jsoup;
import org.jsoup.nodes.Document;
import org.jsoup.nodes.Element;
import org.junit.Test;

import java.util.List;

/**
 * HttpClient & Jsoup libruary test class
 *
 * Created by xuyh at 2017/11/6 15:28.
 */
public class HttpClientJsoupTest {
     
    @Test
    public void test() {
            //通过httpClient获取网页响应,将返回的响应解析为纯文本
        HttpGet httpGet = new HttpGet("http://sports.sina.com.cn/");
        httpGet.setConfig(RequestConfig.custom().setSocketTimeout(30000).setConnectTimeout(30000).build());
        CloseableHttpClient httpClient = null;
        CloseableHttpResponse response = null;

        String responseStr = "";
        try {
            httpClient = HttpClientBuilder.create().build();
            HttpClientContext context = HttpClientContext.create();
            response = httpClient.execute(httpGet, context);
            int state = response.getStatusLine().getStatusCode();
            if (state != 200)
                responseStr = "";
            HttpEntity entity = response.getEntity();
            if (entity != null)
                responseStr = EntityUtils.toString(entity, "utf-8");
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            try {
                if (response != null)
                    response.close();
                if (httpClient != null)
                    httpClient.close();
            } catch (Exception ex) {
                ex.printStackTrace();
            }
        }

        if (responseStr == null)
            return;

        //将解析到的纯文本用Jsoup工具转换成Document文档并进行操作
        Document document = Jsoup.parse(responseStr);
        List elements = document.getElementsByAttributeValue("class", "phdnews_txt fr").first()
                .getElementsByAttributeValue("class", "phdnews_hdline");
        elements.forEach(element -> {
            for (Element e : element.getElementsByTag("a")) {
                System.out.println(e.attr("href"));
                System.out.println(e.text());
            }
        });
    }
}

详解

• 新建HttpGet对象，对象将从 http://sports.sina.com.cn/ 这个URL地址获取GET响应。并设置socket超时时间和连接超时时间分别为30000ms。

HttpGet httpGet = new HttpGet("http://sports.sina.com.cn/");
httpGet.setConfig(RequestConfig.custom().setSocketTimeout(30000).setConnectTimeout(30000).build());

• 通过HttpClientBuilder新建一个CloseableHttpClient对象，并执行上面的HttpGet规定的请求，将响应放在新建的HttpClientContext对象中。最后从HttpClientContext对象中获取响应的文本格式。

CloseableHttpClient httpClient = null;
CloseableHttpResponse response = null;

String responseStr = "";
try {
    httpClient = HttpClientBuilder.create().build();
    HttpClientContext context = HttpClientContext.create();

    response = httpClient.execute(httpGet, context);

    int state = response.getStatusLine().getStatusCode();
    if (state != 200)
        responseStr = "";


    HttpEntity entity = response.getEntity();
    if (entity != null)
        responseStr = EntityUtils.toString(entity, "utf-8");


} catch (Exception e) {
    e.printStackTrace();
} finally {
    try {
        if (response != null)
            response.close();
        if (httpClient != null)
            httpClient.close();
    } catch (Exception ex) {
        ex.printStackTrace();
    }
}

• 将响应的文本用Jsoup库解析，得到其中的各个元素

Document document = Jsoup.parse(responseStr);

List elements = document.getElementsByAttributeValue("class", "phdnews_txt fr").first()
        .getElementsByAttributeValue("class", "phdnews_hdline");

elements.forEach(element -> {
    for (Element e : element.getElementsByTag("a")) {
        System.out.println(e.attr("href"));
        System.out.println(e.text());
    }
});

• Jsoup的Document对象继承自org.jsoup.nodes.Element类和Element均有的部分方法：

public Element getElementById(String id);//通过id获取元素
public Elements getElementsByClass(String className);//通过className获取元素
public Elements getElementsByAttributeValue(String key, String value);//通过属性值获取元素
public Elements getElementsByTag(String tagName);//通过标签名获取元素
public String attr(String attributeKey);//获取本元素的属性值
public String text();//获取本元素的内容

• 其中HTML规定的元素格式为：

<div class="code">   
    <div>
        <br>
            这是第一个段落。    
        <br>
    div>
div>

运行结果

• 运行结果如下所示

http://sports.sina.com.cn/sportsevents/3v3/2017-11-05/doc-ifynmzrs7218551.shtml
3X3黄金联赛冠军赛山西队夺冠!独享48万
http://video.sina.com.cn/sports/k/cba/1105final3x3/
视频
http://video.sina.com.cn/p/sports/k/v/doc/2017-11-05/181467390769.html
黄金mvp集锦
http://video.sina.com.cn/p/sports/k/v/doc/2017-11-05/170167390621.html
直捣黄龙1v2
http://video.sina.com.cn/p/sports/k/v/doc/2017-11-05/183267390917.html
5佳球:库里式虚晃
http://video.sina.com.cn/p/sports/k/v/doc/2017-11-05/150067390331.html
大嫂徐冬冬亮相
http://video.sina.com.cn/p/sports/k/v/doc/2017-11-05/145367390313.html
现场众多美女云集
http://video.sina.com.cn/p/sports/c/zj/v/doc/2017-11-05/150867390337.html
啦啦队热舞表演
http://sports.sina.com.cn/nba/
哈登56分周琦暴扣火箭胜
http://sports.sina.com.cn/basketball/nba/2017-11-06/doc-ifynmzrs7300047.shtml
詹皇26分骑士负

• 爬取的网页内容区域为下图所示：

编写工具类

将HttpClient和Jsoup进行封装，形成一个工具类，内容如下：

import org.apache.http.HttpEntity;
import org.apache.http.NameValuePair;
import org.apache.http.client.CookieStore;
import org.apache.http.client.config.RequestConfig;
import org.apache.http.client.entity.UrlEncodedFormEntity;
import org.apache.http.client.methods.CloseableHttpResponse;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.client.protocol.HttpClientContext;
import org.apache.http.conn.ssl.SSLConnectionSocketFactory;
import org.apache.http.cookie.Cookie;
import org.apache.http.entity.ContentType;
import org.apache.http.entity.StringEntity;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClientBuilder;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.message.BasicNameValuePair;
import org.apache.http.ssl.SSLContextBuilder;
import org.apache.http.util.EntityUtils;
import org.jsoup.Jsoup;
import org.jsoup.nodes.Document;

import javax.net.ssl.*;
import java.io.IOException;
import java.security.GeneralSecurityException;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

/**
 * 
 * Http工具，包含：
 * 普通http请求工具(使用httpClient进行http,https请求的发送)
 * 
 * Created by xuyh at 2017/7/17 19:08.
 */
public class HttpUtils {
     
    /**
     * 请求超时时间,默认20000ms
     */
    private int timeout = 20000;
    /**
     * cookie表
     */
    private Map cookieMap = new HashMap<>();

    /**
     * 请求编码(处理返回结果)，默认UTF-8
     */
    private String charset = "UTF-8";

    private static HttpUtils httpUtils;

    private HttpUtils() {
    }

    /**
     * 获取实例
     *
     * @return
     */
    public static HttpUtils getInstance() {
        if (httpUtils == null)
            httpUtils = new HttpUtils();
        return httpUtils;
    }

    /**
     * 清空cookieMap
     */
    public void invalidCookieMap() {
        cookieMap.clear();
    }

    public int getTimeout() {
        return timeout;
    }

    /**
     * 设置请求超时时间
     *
     * @param timeout
     */
    public void setTimeout(int timeout) {
        this.timeout = timeout;
    }

    public String getCharset() {
        return charset;
    }

    /**
     * 设置请求字符编码集
     *
     * @param charset
     */
    public void setCharset(String charset) {
        this.charset = charset;
    }

    /**
     * 将网页返回为解析后的文档格式
     * 
     * @param html
     * @return
     * @throws Exception
     */
    public static Document parseHtmlToDoc(String html) throws Exception {
        return removeHtmlSpace(html);
    }

    private static Document removeHtmlSpace(String str) {
        Document doc = Jsoup.parse(str);
        String result = doc.html().replace(" ", "");
        return Jsoup.parse(result);
    }

    /**
     * 执行get请求,返回doc
     *
     * @param url
     * @return
     * @throws Exception
     */
    public Document executeGetAsDocument(String url) throws Exception {
        return parseHtmlToDoc(executeGet(url));
    }

    /**
     * 执行get请求
     *
     * @param url
     * @return
     * @throws Exception
     */
    public String executeGet(String url) throws Exception {
        HttpGet httpGet = new HttpGet(url);
        httpGet.setHeader("Cookie", convertCookieMapToString(cookieMap));
        httpGet.setConfig(RequestConfig.custom().setSocketTimeout(timeout).setConnectTimeout(timeout).build());
        CloseableHttpClient httpClient = null;
        String str = "";
        try {
            httpClient = HttpClientBuilder.create().build();
            HttpClientContext context = HttpClientContext.create();
            CloseableHttpResponse response = httpClient.execute(httpGet, context);
            getCookiesFromCookieStore(context.getCookieStore(), cookieMap);
            int state = response.getStatusLine().getStatusCode();
            if (state == 404) {
                str = "";
            }
            try {
                HttpEntity entity = response.getEntity();
                if (entity != null) {
                    str = EntityUtils.toString(entity, charset);
                }
            } finally {
                response.close();
            }
        } catch (IOException e) {
            throw e;
        } finally {
            try {
                if (httpClient != null)
                    httpClient.close();
            } catch (IOException e) {
                throw e;
            }
        }
        return str;
    }

    /**
     * 用https执行get请求,返回doc
     *
     * @param url
     * @return
     * @throws Exception
     */
    public Document executeGetWithSSLAsDocument(String url) throws Exception {
        return parseHtmlToDoc(executeGetWithSSL(url));
    }

    /**
     * 用https执行get请求
     *
     * @param url
     * @return
     * @throws Exception
     */
    public String executeGetWithSSL(String url) throws Exception {
        HttpGet httpGet = new HttpGet(url);
        httpGet.setHeader("Cookie", convertCookieMapToString(cookieMap));
        httpGet.setConfig(RequestConfig.custom().setSocketTimeout(timeout).setConnectTimeout(timeout).build());
        CloseableHttpClient httpClient = null;
        String str = "";
        try {
            httpClient = createSSLInsecureClient();
            HttpClientContext context = HttpClientContext.create();
            CloseableHttpResponse response = httpClient.execute(httpGet, context);
            getCookiesFromCookieStore(context.getCookieStore(), cookieMap);
            int state = response.getStatusLine().getStatusCode();
            if (state == 404) {
                str = "";
            }
            try {
                HttpEntity entity = response.getEntity();
                if (entity != null) {
                    str = EntityUtils.toString(entity, charset);
                }
            } finally {
                response.close();
            }
        } catch (IOException e) {
            throw e;
        } catch (GeneralSecurityException ex) {
            throw ex;
        } finally {
            try {
                if (httpClient != null)
                    httpClient.close();
            } catch (IOException e) {
                throw e;
            }
        }
        return str;
    }

    /**
     * 执行post请求,返回doc
     *
     * @param url
     * @param params
     * @return
     * @throws Exception
     */
    public Document executePostAsDocument(String url, Map params) throws Exception {
        return parseHtmlToDoc(executePost(url, params));
    }

    /**
     * 执行post请求
     *
     * @param url
     * @param params
     * @return
     * @throws Exception
     */
    public String executePost(String url, Map params) throws Exception {
        String reStr = "";
        HttpPost httpPost = new HttpPost(url);
        httpPost.setConfig(RequestConfig.custom().setSocketTimeout(timeout).setConnectTimeout(timeout).build());
        httpPost.setHeader("Cookie", convertCookieMapToString(cookieMap));
        List paramsRe = new ArrayList<>();
        for (String key : params.keySet()) {
            paramsRe.add(new BasicNameValuePair(key, params.get(key)));
        }
        CloseableHttpClient httpclient = HttpClientBuilder.create().build();
        CloseableHttpResponse response;
        try {
            httpPost.setEntity(new UrlEncodedFormEntity(paramsRe));
            HttpClientContext context = HttpClientContext.create();
            response = httpclient.execute(httpPost, context);
            getCookiesFromCookieStore(context.getCookieStore(), cookieMap);
            HttpEntity entity = response.getEntity();
            reStr = EntityUtils.toString(entity, charset);
        } catch (IOException e) {
            throw e;
        } finally {
            httpPost.releaseConnection();
        }
        return reStr;
    }

    /**
     * 用https执行post请求,返回doc
     *
     * @param url
     * @param params
     * @return
     * @throws Exception
     */
    public Document executePostWithSSLAsDocument(String url, Map params) throws Exception {
        return parseHtmlToDoc(executePostWithSSL(url, params));
    }

    /**
     * 用https执行post请求
     *
     * @param url
     * @param params
     * @return
     * @throws Exception
     */
    public String executePostWithSSL(String url, Map params) throws Exception {
        String re = "";
        HttpPost post = new HttpPost(url);
        List paramsRe = new ArrayList<>();
        for (String key : params.keySet()) {
            paramsRe.add(new BasicNameValuePair(key, params.get(key)));
        }
        post.setHeader("Cookie", convertCookieMapToString(cookieMap));
        post.setConfig(RequestConfig.custom().setSocketTimeout(timeout).setConnectTimeout(timeout).build());
        CloseableHttpResponse response;
        try {
            CloseableHttpClient httpClientRe = createSSLInsecureClient();
            HttpClientContext contextRe = HttpClientContext.create();
            post.setEntity(new UrlEncodedFormEntity(paramsRe));
            response = httpClientRe.execute(post, contextRe);
            HttpEntity entity = response.getEntity();
            if (entity != null) {
                re = EntityUtils.toString(entity, charset);
            }
            getCookiesFromCookieStore(contextRe.getCookieStore(), cookieMap);
        } catch (Exception e) {
            throw e;
        }
        return re;
    }

    /**
     * 发送JSON格式body的POST请求
     *
     * @param url 地址
     * @param jsonBody json body
     * @return
     * @throws Exception
     */
    public String executePostWithJson(String url, String jsonBody) throws Exception {
        String reStr = "";
        HttpPost httpPost = new HttpPost(url);
        httpPost.setConfig(RequestConfig.custom().setSocketTimeout(timeout).setConnectTimeout(timeout).build());
        httpPost.setHeader("Cookie", convertCookieMapToString(cookieMap));
        CloseableHttpClient httpclient = HttpClientBuilder.create().build();
        CloseableHttpResponse response;
        try {
            httpPost.setEntity(new StringEntity(jsonBody, ContentType.APPLICATION_JSON));
            HttpClientContext context = HttpClientContext.create();
            response = httpclient.execute(httpPost, context);
            getCookiesFromCookieStore(context.getCookieStore(), cookieMap);
            HttpEntity entity = response.getEntity();
            reStr = EntityUtils.toString(entity, charset);
        } catch (IOException e) {
            throw e;
        } finally {
            httpPost.releaseConnection();
        }
        return reStr;
    }

    /**
     * 发送JSON格式body的SSL POST请求
     *
     * @param url 地址
     * @param jsonBody json body
     * @return
     * @throws Exception
     */
    public String executePostWithJsonAndSSL(String url, String jsonBody) throws Exception {
        String re = "";
        HttpPost post = new HttpPost(url);
        post.setHeader("Cookie", convertCookieMapToString(cookieMap));
        post.setConfig(RequestConfig.custom().setSocketTimeout(timeout).setConnectTimeout(timeout).build());
        CloseableHttpResponse response;
        try {
            CloseableHttpClient httpClientRe = createSSLInsecureClient();
            HttpClientContext contextRe = HttpClientContext.create();
            post.setEntity(new StringEntity(jsonBody, ContentType.APPLICATION_JSON));
            response = httpClientRe.execute(post, contextRe);
            HttpEntity entity = response.getEntity();
            if (entity != null) {
                re = EntityUtils.toString(entity, charset);
            }
            getCookiesFromCookieStore(contextRe.getCookieStore(), cookieMap);
        } catch (Exception e) {
            throw e;
        }
        return re;
    }

    private void getCookiesFromCookieStore(CookieStore cookieStore, Map cookieMap) {
        List cookies = cookieStore.getCookies();
        for (Cookie cookie : cookies) {
            cookieMap.put(cookie.getName(), cookie.getValue());
        }
    }

    private String convertCookieMapToString(Map map) {
        String cookie = "";
        for (String key : map.keySet()) {
            cookie += (key + "=" + map.get(key) + "; ");
        }
        if (map.size() > 0) {
            cookie = cookie.substring(0, cookie.length() - 2);
        }
        return cookie;
    }

    /**
     * 创建 SSL连接
     *
     * @return
     * @throws GeneralSecurityException
     */
    private static CloseableHttpClient createSSLInsecureClient() throws GeneralSecurityException {
        try {
            SSLContext sslContext = new SSLContextBuilder().loadTrustMaterial(null, (chain, authType) -> true).build();
            SSLConnectionSocketFactory sslConnectionSocketFactory = new SSLConnectionSocketFactory(sslContext,
                    (s, sslContextL) -> true);
            return HttpClients.custom().setSSLSocketFactory(sslConnectionSocketFactory).build();
        } catch (GeneralSecurityException e) {
            throw e;
        }
    }
}

上面的工具类不仅可以进行网页内容的获取，还能够进行http请求的发送。

源码地址

https://github.com/johnsonmoon/HttpUtils.git