[TOC] # 需求 现有一些原始日志需要做增强解析处理，流程： 1. 从原始日志文件中读取数据 2. 根据日志中的一个URL字段到外部知识库中获取信息增强到原始日志 3. 如果成功增强，则输出到增强结果目录；如果增强失败，则抽取原始数据中URL字段输出到待爬清单目录 # 分析 程序的关键点是要在一个mapreduce程序中根据数据的不同输出两类结果到不同目录，这类灵活的输出需求可以通过自定义outputformat来实现 # 实现 实现要点： 1. **在mapreduce中访问外部资源** 2. **自定义outputformat，改写其中的recordwriter，改写具体输出数据的方法write()** # 代码实现 **数据库获取数据的工具** 给数据打上标签 ~~~ public class DBLoader { public static void dbLoader(HashMap<String, String> ruleMap) { Connection conn = null; Statement st = null; ResultSet res = null; try { Class.forName("com.mysql.jdbc.Driver"); conn = DriverManager.getConnection("jdbc:mysql://hdp-node01:3306/urlknowledge", "root", "root"); st = conn.createStatement(); res = st.executeQuery("select url,content from urlcontent"); while (res.next()) { ruleMap.put(res.getString(1), res.getString(2)); } } catch (Exception e) { e.printStackTrace(); } finally { try{ if(res!=null){ res.close(); } if(st!=null){ st.close(); } if(conn!=null){ conn.close(); } }catch(Exception e){ e.printStackTrace(); } } } public static void main(String[] args) { DBLoader db = new DBLoader(); HashMap<String, String> map = new HashMap<String,String>(); db.dbLoader(map); System.out.println(map.size()); } } ~~~ **自定义一个outputformat** 根据不同的放到不同的文件中 ~~~ public class LogEnhancerOutputFormat extends FileOutputFormat<Text, NullWritable>{ @Override public RecordWriter<Text, NullWritable> getRecordWriter(TaskAttemptContext context) throws IOException, InterruptedException { //参数context代表上下文 //获取配置信息 FileSystem fs = FileSystem.get(context.getConfiguration()); Path enhancePath = new Path("hdfs://hdp-node01:9000/flow/enhancelog/enhanced.log"); Path toCrawlPath = new Path("hdfs://hdp-node01:9000/flow/tocrawl/tocrawl.log"); FSDataOutputStream enhanceOut = fs.create(enhancePath); FSDataOutputStream toCrawlOut = fs.create(toCrawlPath); //返回的类和下面定义的内部类对应起来 return new MyRecordWriter(enhanceOut,toCrawlOut); } public static class MyRecordWriter extends RecordWriter<Text, NullWritable>{ FSDataOutputStream enhanceOut = null; FSDataOutputStream toCrawlOut = null; public MyRecordWriter(FSDataOutputStream enhanceOut, FSDataOutputStream toCrawlOut) { this.enhanceOut = enhanceOut; this.toCrawlOut = toCrawlOut; } @Override public void write(Text key, NullWritable value) throws IOException, InterruptedException { //有了数据，你来负责写到目的地 —— hdfs //判断，进来内容如果是带tocrawl的，就往待爬清单输出流中写 toCrawlOut //然后就造成了写到不同文件的情况 if(key.toString().contains("tocrawl")){ toCrawlOut.write(key.toString().getBytes()); }else{ enhanceOut.write(key.toString().getBytes()); } } @Override public void close(TaskAttemptContext context) throws IOException, InterruptedException { if(toCrawlOut!=null){ toCrawlOut.close(); } if(enhanceOut!=null){ enhanceOut.close(); } } } } ~~~ **开发mapreduce处理流程** ~~~ /** * 这个程序是对每个小时不断产生的用户上网记录日志进行增强(将日志中的url所指向的网页内容分析结果信息追加到每一行原始日志后面) */ public class LogEnhancer { static class LogEnhancerMapper extends Mapper<LongWritable, Text, Text, NullWritable> { HashMap<String, String> knowledgeMap = new HashMap<String, String>(); /** * maptask在初始化时会先调用setup方法一次 利用这个机制，将外部的知识库加载到maptask执行的机器内存中 */ @Override protected void setup(org.apache.hadoop.mapreduce.Mapper.Context context) throws IOException, InterruptedException { DBLoader.dbLoader(knowledgeMap); } @Override protected void map(LongWritable key, Text value, Context context) throws IOException, InterruptedException { String line = value.toString(); String[] fields = StringUtils.split(line, "\t"); try { String url = fields[26]; // 对这一行日志中的url去知识库中查找内容分析信息 String content = knowledgeMap.get(url); // 根据内容信息匹配的结果，来构造两种输出结果 String result = ""; if (null == content) { // 输往待爬清单的内容 result = url + "\t" + "tocrawl\n"; } else { // 输往增强日志的内容 result = line + "\t" + content + "\n"; } context.write(new Text(result), NullWritable.get()); } catch (Exception e) { } } } public static void main(String[] args) throws Exception { Configuration conf = new Configuration(); Job job = Job.getInstance(conf); job.setJarByClass(LogEnhancer.class); job.setMapperClass(LogEnhancerMapper.class); job.setOutputKeyClass(Text.class); job.setOutputValueClass(NullWritable.class); // 要将自定义的输出格式组件设置到job中 job.setOutputFormatClass(LogEnhancerOutputFormat.class); FileInputFormat.setInputPaths(job, new Path(args[0])); // 虽然我们自定义了outputformat，但是因为我们的outputformat继承自fileoutputformat // 而fileoutputformat要输出一个_SUCCESS文件，所以，在这还得指定一个输出目录 FileOutputFormat.setOutputPath(job, new Path(args[1])); job.waitForCompletion(true); System.exit(0); } } ~~~