从头学习爬虫（二十三）重构篇----WebMagic框架分析之pipeline

这系列文章主要分析分析webmagic框架，没有实战内容，如有实战问题可以讨论，也可以提供技术支持。

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Pipeline

我们先来看看接口，就一个process 方法

package us.codecraft.webmagic.pipeline;

import us.codecraft.webmagic.ResultItems;
import us.codecraft.webmagic.Task;

/**
 * Pipeline is the persistent and offline process part of crawler.<br>
 * The interface Pipeline can be implemented to customize ways of persistent.
 *
 * @author [email protected] <br>
 * @since 0.1.0
 * @see ConsolePipeline
 * @see FilePipeline
 */
public interface Pipeline {

    /**
     * Process extracted results.
     *
     * @param resultItems resultItems
     * @param task task
     */
    public void process(ResultItems resultItems, Task task);
}

我们再来看看默认调用实现pipeline的那个类ConsolePipeline

很简单把存储在resultItem 的结果打印出来

package us.codecraft.webmagic.pipeline;

import us.codecraft.webmagic.ResultItems;
import us.codecraft.webmagic.Task;

import java.util.Map;

/**
 * Write results in console.<br>
 * Usually used in test.
 *
 * @author [email protected] <br>
 * @since 0.1.0
 */
public class ConsolePipeline implements Pipeline {

    @Override
    public void process(ResultItems resultItems, Task task) {
        System.out.println("get page: " + resultItems.getRequest().getUrl());
        for (Map.Entry<String, Object> entry : resultItems.getAll().entrySet()) {
            System.out.println(entry.getKey() + ":\t" + entry.getValue());
        }
    }
}

其他的

FilePipeline 以文件形式保存

package us.codecraft.webmagic.pipeline;

import org.apache.commons.codec.digest.DigestUtils;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import us.codecraft.webmagic.ResultItems;
import us.codecraft.webmagic.Task;
import us.codecraft.webmagic.utils.FilePersistentBase;

import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStreamWriter;
import java.io.PrintWriter;
import java.util.Map;

/**
 * Store results in files.<br>
 *
 * @author [email protected] <br>
 * @since 0.1.0
 */
public class FilePipeline extends FilePersistentBase implements Pipeline {

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

    /**
     * create a FilePipeline with default path"/data/webmagic/"
     */
    public FilePipeline() {
        setPath("/data/webmagic/");
    }

    public FilePipeline(String path) {
        setPath(path);
    }

    @Override
    public void process(ResultItems resultItems, Task task) {
        String path = this.path + PATH_SEPERATOR + task.getUUID() + PATH_SEPERATOR;
        try {
            PrintWriter printWriter = new PrintWriter(new OutputStreamWriter(new FileOutputStream(getFile(path + DigestUtils.md5Hex(resultItems.getRequest().getUrl()) + ".html")),"UTF-8"));
            printWriter.println("url:\t" + resultItems.getRequest().getUrl());
            for (Map.Entry<String, Object> entry : resultItems.getAll().entrySet()) {
                if (entry.getValue() instanceof Iterable) {
                    Iterable value = (Iterable) entry.getValue();
                    printWriter.println(entry.getKey() + ":");
                    for (Object o : value) {
                        printWriter.println(o);
                    }
                } else {
                    printWriter.println(entry.getKey() + ":\t" + entry.getValue());
                }
            }
            printWriter.close();
        } catch (IOException e) {
            logger.warn("write file error", e);
        }
    }
}

结果集

ResultItemsCollectorPipeline 我猜主要是为了批量处理这样效率高

package us.codecraft.webmagic.pipeline;

import us.codecraft.webmagic.ResultItems;
import us.codecraft.webmagic.Task;

import java.util.ArrayList;
import java.util.List;

/**
 * @author [email protected]
 * @since 0.4.0
 */
public class ResultItemsCollectorPipeline implements CollectorPipeline<ResultItems> {

    private List<ResultItems> collector = new ArrayList<ResultItems>();

    @Override
    public synchronized void process(ResultItems resultItems, Task task) {
        collector.add(resultItems);
    }

    @Override
    public List<ResultItems> getCollected() {
        return collector;
    }
}

扩展

代码就不贴了

大概介绍下

FilePageModelPipeline 保存成.html

JsonFilePageModelPipeline 保存成.json

JsonFilePipeline 将内容转换成json再保存成.json

MultiPagePipeline 用于需要拼接的地方

官网还有个集成mysql 点击打开链接

总结

上面介绍了很多保存方式，个人习惯于在process就进行数据持久化，不知道有什么不同，欢迎探讨。