五、学习爬虫框架WebMagic（一）---入门案例

一、WebMagic简介
参见网上其他介绍。

二、添加依赖

		<!-- webmagic 核心包 -->
		<dependency>
			<groupId>us.codecraft</groupId>
			<artifactId>webmagic-core</artifactId>
			<version>0.7.3</version>
			<exclusions>
				<exclusion>
					<!-- 自带的commons-collections用不了 -->
					<groupId>commons-collections</groupId>
					<artifactId>commons-collections</artifactId>
				</exclusion>
			</exclusions>
		</dependency>
		<!-- webmagic 扩展包 -->
		<dependency>
			<groupId>us.codecraft</groupId>
			<artifactId>webmagic-extension</artifactId>
			<version>0.7.3</version>
			<exclusions>
				<exclusion>
					<!-- 默认是log4j12，若要用其他日志框架，请排除 -->
					<groupId>org.slf4j</groupId>
					<artifactId>slf4j-log4j12</artifactId>
				</exclusion>
			</exclusions>
		</dependency>
		<!-- webmagic-selenium 对selenium支持 -->
		<dependency>
			<groupId>us.codecraft</groupId>
			<artifactId>webmagic-selenium</artifactId>
			<version>0.7.3</version>
		</dependency>
		<!-- commons-collections -->
		<dependency>
			<groupId>commons-collections</groupId>
			<artifactId>commons-collections</artifactId>
			<version>3.2.1</version>
		</dependency>
	</dependencies>

注意要点1：webmagic-core 包下有 commons-collections 依赖包，但是该包在3.2.2版本有点问题，需要将其剔除出来，使用3.2.1版本的JAR包
注意要点2：webmagic-extension 默认使用的日志框架是 slf4j-log4j12，若项目中使用了其他日志框架，需要将其排除。

三、案例

package org.pc.webmagic;

import org.pc.webmagic.error.HttpClientDownloader;
import us.codecraft.webmagic.Page;
import us.codecraft.webmagic.Site;
import us.codecraft.webmagic.Spider;
import us.codecraft.webmagic.processor.PageProcessor;

/**
 * @author 咸鱼
 * @date 2018/12/28 20:08
 */
public class GithubRepoPageProcessor implements PageProcessor {

    /**
     * 部分一：抓去网站的相关配置，包括编码、抓去间隔、重试次数
     */
    private Site site = Site.me().setRetryTimes(3).setSleepTime(1000).setTimeOut(10000);

    @Override
    public void process(Page page) {
        page.addTargetRequests(page.getHtml().links().regex("(https://github\\.com/\\w+/\\w+)").all());
        page.putField("author", page.getUrl().regex("\"https://github\\.com/(\\w+)/.*\"").toString());
        page.putField("name", page.getHtml().xpath("//h1[@class='entry-title public']/strong/a/text()").toString());
        if (page.getResultItems().get("name") == null){
            page.setSkip(true);
        }
        page.putField("readme", page.getHtml().xpath("//div[@id='readme']/tidyText()"));
    }

    @Override
    public Site getSite() {
        return site;
    }
    public static void main(String[] args) {
        Spider.create(new GithubRepoPageProcessor())
                .addUrl("https://github.com/code4craft")
                //覆盖默认的实现 HttpClientDownloader，因为使用webmagic爬取 https 网站时，会
                .setDownloader(new HttpClientDownloader())
                .thread(5)
                .run();
    }
}

问题：这个案例在运行的时候会报javax.net.ssl.SSLException: Received fatal alert: protocol_versio错误？
原因：绕过ssl时，没有支持版本。

解决办法一：直接去 github clone修复后的 webmagic-core ，然后设置 commons-collections 的版本号为 3.2.1，然后重新打成Jar包（会打成webmagic-core-0.7.3.jar、webmagic-core-0.7.3-javadoc.jar、webmagic-core-0.7.3-sources.jar），然后替代本地仓库的Jar包（推荐使用！！！）。

解决办法二：
核心是重写HttpClientGenerator#buildSSLConnectionSocketFactory()方法

private SSLConnectionSocketFactory buildSSLConnectionSocketFactory() {
        try {
            // 优先绕过安全证书
            return new SSLConnectionSocketFactory(createIgnoreVerifySSL(), new String[]{"SSLv3", "TLSv1", "TLSv1.1", "TLSv1.2"},
                    null,
                    new DefaultHostnameVerifier());
        } catch (KeyManagementException e) {
            logger.error("ssl connection fail", e);
        } catch (NoSuchAlgorithmException e) {
            logger.error("ssl connection fail", e);
        }
        return SSLConnectionSocketFactory.getSocketFactory();
    }

第一步：重写 HttpClientGenerator

package org.pc.webmagic.error;

import org.apache.http.HttpException;
import org.apache.http.HttpRequest;
import org.apache.http.HttpRequestInterceptor;
import org.apache.http.client.CookieStore;
import org.apache.http.config.Registry;
import org.apache.http.config.RegistryBuilder;
import org.apache.http.config.SocketConfig;
import org.apache.http.conn.socket.ConnectionSocketFactory;
import org.apache.http.conn.socket.PlainConnectionSocketFactory;
import org.apache.http.conn.ssl.DefaultHostnameVerifier;
import org.apache.http.conn.ssl.SSLConnectionSocketFactory;
import org.apache.http.impl.client.*;
import org.apache.http.impl.conn.PoolingHttpClientConnectionManager;
import org.apache.http.impl.cookie.BasicClientCookie;
import org.apache.http.protocol.HttpContext;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import us.codecraft.webmagic.Site;
import us.codecraft.webmagic.downloader.CustomRedirectStrategy;

import javax.net.ssl.SSLContext;
import javax.net.ssl.TrustManager;
import javax.net.ssl.X509TrustManager;
import java.io.IOException;
import java.security.KeyManagementException;
import java.security.NoSuchAlgorithmException;
import java.security.cert.CertificateException;
import java.security.cert.X509Certificate;
import java.util.Map;

/**
 * @author 咸鱼
 * @date 2018/12/28 21:19
 */
public class HttpClientGenerator {

    private transient Logger logger = LoggerFactory.getLogger(getClass());

    private PoolingHttpClientConnectionManager connectionManager;

    public HttpClientGenerator() {
        Registry<ConnectionSocketFactory> reg = RegistryBuilder.<ConnectionSocketFactory>create()
                .register("http", PlainConnectionSocketFactory.INSTANCE)
                .register("https", buildSSLConnectionSocketFactory())
                .build();
        connectionManager = new PoolingHttpClientConnectionManager(reg);
        connectionManager.setDefaultMaxPerRoute(100);
    }

    private SSLConnectionSocketFactory buildSSLConnectionSocketFactory() {
        try {
            // 优先绕过安全证书
            return new SSLConnectionSocketFactory(createIgnoreVerifySSL(), new String[]{"SSLv3", "TLSv1", "TLSv1.1", "TLSv1.2"},
                    null,
                    new DefaultHostnameVerifier());
        } catch (KeyManagementException e) {
            logger.error("ssl connection fail", e);
        } catch (NoSuchAlgorithmException e) {
            logger.error("ssl connection fail", e);
        }
        return SSLConnectionSocketFactory.getSocketFactory();
    }

    private SSLContext createIgnoreVerifySSL() throws NoSuchAlgorithmException, KeyManagementException {
        // 实现一个X509TrustManager接口，用于绕过验证，不用修改里面的方法
        X509TrustManager trustManager = new X509TrustManager() {

            @Override
            public void checkClientTrusted(X509Certificate[] chain, String authType) throws CertificateException {
            }

            @Override
            public void checkServerTrusted(X509Certificate[] chain, String authType) throws CertificateException {
            }

            @Override
            public X509Certificate[] getAcceptedIssuers() {
                return null;
            }

        };

        SSLContext sc = SSLContext.getInstance("SSLv3");
        sc.init(null, new TrustManager[] { trustManager }, null);
        return sc;
    }

    public HttpClientGenerator setPoolSize(int poolSize) {
        connectionManager.setMaxTotal(poolSize);
        return this;
    }

    public CloseableHttpClient getClient(Site site) {
        return generateClient(site);
    }

    private CloseableHttpClient generateClient(Site site) {
        HttpClientBuilder httpClientBuilder = HttpClients.custom();

        httpClientBuilder.setConnectionManager(connectionManager);
        if (site.getUserAgent() != null) {
            httpClientBuilder.setUserAgent(site.getUserAgent());
        } else {
            httpClientBuilder.setUserAgent("");
        }
        if (site.isUseGzip()) {
            httpClientBuilder.addInterceptorFirst(new HttpRequestInterceptor() {

                @Override
                public void process(
                        final HttpRequest request,
                        final HttpContext context) throws HttpException, IOException {
                    if (!request.containsHeader("Accept-Encoding")) {
                        request.addHeader("Accept-Encoding", "gzip");
                    }
                }
            });
        }
        //解决post/redirect/post 302跳转问题
        httpClientBuilder.setRedirectStrategy(new CustomRedirectStrategy());

        SocketConfig.Builder socketConfigBuilder = SocketConfig.custom();
        socketConfigBuilder.setSoKeepAlive(true).setTcpNoDelay(true);
        socketConfigBuilder.setSoTimeout(site.getTimeOut());
        SocketConfig socketConfig = socketConfigBuilder.build();
        httpClientBuilder.setDefaultSocketConfig(socketConfig);
        connectionManager.setDefaultSocketConfig(socketConfig);
        httpClientBuilder.setRetryHandler(new DefaultHttpRequestRetryHandler(site.getRetryTimes(), true));
        generateCookie(httpClientBuilder, site);
        return httpClientBuilder.build();
    }

    private void generateCookie(HttpClientBuilder httpClientBuilder, Site site) {
        if (site.isDisableCookieManagement()) {
            httpClientBuilder.disableCookieManagement();
            return;
        }
        CookieStore cookieStore = new BasicCookieStore();
        for (Map.Entry<String, String> cookieEntry : site.getCookies().entrySet()) {
            BasicClientCookie cookie = new BasicClientCookie(cookieEntry.getKey(), cookieEntry.getValue());
            cookie.setDomain(site.getDomain());
            cookieStore.addCookie(cookie);
        }
        for (Map.Entry<String, Map<String, String>> domainEntry : site.getAllCookies().entrySet()) {
            for (Map.Entry<String, String> cookieEntry : domainEntry.getValue().entrySet()) {
                BasicClientCookie cookie = new BasicClientCookie(cookieEntry.getKey(), cookieEntry.getValue());
                cookie.setDomain(domainEntry.getKey());
                cookieStore.addCookie(cookie);
            }
        }
        httpClientBuilder.setDefaultCookieStore(cookieStore);
    }

}

第二步：重写 HttpClientDownloader

package org.pc.webmagic.error;

import org.apache.commons.io.IOUtils;
import org.apache.http.HttpResponse;
import org.apache.http.client.methods.CloseableHttpResponse;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.util.EntityUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import us.codecraft.webmagic.Page;
import us.codecraft.webmagic.Request;
import us.codecraft.webmagic.Site;
import us.codecraft.webmagic.Task;
import us.codecraft.webmagic.downloader.AbstractDownloader;
import us.codecraft.webmagic.downloader.HttpClientRequestContext;
import us.codecraft.webmagic.downloader.HttpUriRequestConverter;
import us.codecraft.webmagic.proxy.Proxy;
import us.codecraft.webmagic.proxy.ProxyProvider;
import us.codecraft.webmagic.selector.PlainText;
import us.codecraft.webmagic.utils.CharsetUtils;
import us.codecraft.webmagic.utils.HttpClientUtils;

import java.io.IOException;
import java.nio.charset.Charset;
import java.util.HashMap;
import java.util.Map;

/**
 * @author 咸鱼
 * @date 2018/12/28 21:22
 */
public class HttpClientDownloader extends AbstractDownloader {
    private Logger logger = LoggerFactory.getLogger(getClass());

    private final Map<String, CloseableHttpClient> httpClients = new HashMap<String, CloseableHttpClient>();

    private HttpClientGenerator httpClientGenerator = new HttpClientGenerator();

    private HttpUriRequestConverter httpUriRequestConverter = new HttpUriRequestConverter();

    private ProxyProvider proxyProvider;

    private boolean responseHeader = true;

    public void setHttpUriRequestConverter(HttpUriRequestConverter httpUriRequestConverter) {
        this.httpUriRequestConverter = httpUriRequestConverter;
    }

    public void setProxyProvider(ProxyProvider proxyProvider) {
        this.proxyProvider = proxyProvider;
    }

    private CloseableHttpClient getHttpClient(Site site) {
        if (site == null) {
            return httpClientGenerator.getClient(null);
        }
        String domain = site.getDomain();
        CloseableHttpClient httpClient = httpClients.get(domain);
        if (httpClient == null) {
            synchronized (this) {
                httpClient = httpClients.get(domain);
                if (httpClient == null) {
                    httpClient = httpClientGenerator.getClient(site);
                    httpClients.put(domain, httpClient);
                }
            }
        }
        return httpClient;
    }

    @Override
    public Page download(Request request, Task task) {
        if (task == null || task.getSite() == null) {
            throw new NullPointerException("task or site can not be null");
        }
        CloseableHttpResponse httpResponse = null;
        CloseableHttpClient httpClient = getHttpClient(task.getSite());
        Proxy proxy = proxyProvider != null ? proxyProvider.getProxy(task) : null;
        HttpClientRequestContext requestContext = httpUriRequestConverter.convert(request, task.getSite(), proxy);
        Page page = Page.fail();
        try {
            httpResponse = httpClient.execute(requestContext.getHttpUriRequest(), requestContext.getHttpClientContext());
            page = handleResponse(request, request.getCharset() != null ? request.getCharset() : task.getSite().getCharset(), httpResponse, task);
            onSuccess(request);
            logger.info("downloading page success {}", request.getUrl());
            return page;
        } catch (IOException e) {
            logger.warn("download page {} error", request.getUrl(), e);
            onError(request);
            return page;
        } finally {
            if (httpResponse != null) {
                //ensure the connection is released back to pool
                EntityUtils.consumeQuietly(httpResponse.getEntity());
            }
            if (proxyProvider != null && proxy != null) {
                proxyProvider.returnProxy(proxy, page, task);
            }
        }
    }

    @Override
    public void setThread(int thread) {
        httpClientGenerator.setPoolSize(thread);
    }

    protected Page handleResponse(Request request, String charset, HttpResponse httpResponse, Task task) throws IOException {
        byte[] bytes = IOUtils.toByteArray(httpResponse.getEntity().getContent());
        String contentType = httpResponse.getEntity().getContentType() == null ? "" : httpResponse.getEntity().getContentType().getValue();
        Page page = new Page();
        page.setBytes(bytes);
        if (!request.isBinaryContent()){
            if (charset == null) {
                charset = getHtmlCharset(contentType, bytes);
            }
            page.setCharset(charset);
            page.setRawText(new String(bytes, charset));
        }
        page.setUrl(new PlainText(request.getUrl()));
        page.setRequest(request);
        page.setStatusCode(httpResponse.getStatusLine().getStatusCode());
        page.setDownloadSuccess(true);
        if (responseHeader) {
            page.setHeaders(HttpClientUtils.convertHeaders(httpResponse.getAllHeaders()));
        }
        return page;
    }

    private String getHtmlCharset(String contentType, byte[] contentBytes) throws IOException {
        String charset = CharsetUtils.detectCharset(contentType, contentBytes);
        if (charset == null) {
            charset = Charset.defaultCharset().name();
            logger.warn("Charset autodetect failed, use {} as charset. Please specify charset in Site.setCharset()", Charset.defaultCharset());
        }
        return charset;
    }
}

第三步：在Spider中设置重写后的HttpClientDownloader

@Override
    public Site getSite() {
        return site;
    }
    public static void main(String[] args) {
        Spider.create(new GithubRepoPageProcessor())
                .addUrl("https://github.com/code4craft")
                //覆盖默认的实现 HttpClientDownloader，因为使用webmagic爬取 https 网站时，会报错
                .setDownloader(new HttpClientDownloader())
                .thread(5)
                .run();
    }

五、学习爬虫框架WebMagic（一）---入门案例

猜你喜欢