mapreduce导出MSSQL的数据到HDFS

　　今天想通过一些数据，来测试一下我的《基于信息熵的无字典分词算法》这篇文章的正确性。就写了一下MapReduce程序从MSSQL SERVER2008数据库里取数据分析。程序发布到hadoop机器上运行报SQLEXCEPTION错误

 

　　奇怪了，我的SQL语句中没有LIMIT，这LIMIT哪来的。我翻看了DBInputFormat类的源码，

 1 protected RecordReader<LongWritable, T> createDBRecordReader(DBInputSplit split,
 2 
 3       Configuration conf) throws IOException {
 4 
 5  
 6 
 7     @SuppressWarnings("unchecked")
 8 
 9     Class<T> inputClass = (Class<T>) (dbConf.getInputClass());
10 
11     try {
12 
13       // use database product name to determine appropriate record reader.
14 
15       if (dbProductName.startsWith("ORACLE")) {
16 
17         // use Oracle-specific db reader.
18 
19         return new OracleDBRecordReader<T>(split, inputClass,
20 
21             conf, createConnection(), getDBConf(), conditions, fieldNames,
22 
23             tableName);
24 
25       } else if (dbProductName.startsWith("MYSQL")) {
26 
27         // use MySQL-specific db reader.
28 
29         return new MySQLDBRecordReader<T>(split, inputClass,
30 
31             conf, createConnection(), getDBConf(), conditions, fieldNames,
32 
33             tableName);
34 
35       } else {
36 
37         // Generic reader.
38 
39         return new DBRecordReader<T>(split, inputClass,
40 
41             conf, createConnection(), getDBConf(), conditions, fieldNames,
42 
43             tableName);
44 
45       }
46 
47     } catch (SQLException ex) {
48 
49       throw new IOException(ex.getMessage());
50 
51     }
52 
53   }
View Code

DBRecordReader的源码

 1 protected String getSelectQuery() {
 2 
 3     StringBuilder query = new StringBuilder();
 4 
 5  
 6 
 7     // Default codepath for MySQL, HSQLDB, etc. Relies on LIMIT/OFFSET for splits.
 8 
 9     if(dbConf.getInputQuery() == null) {
10 
11       query.append("SELECT ");
12 
13   
14 
15       for (int i = 0; i < fieldNames.length; i++) {
16 
17         query.append(fieldNames[i]);
18 
19         if (i != fieldNames.length -1) {
20 
21           query.append(", ");
22 
23         }
24 
25       }
26 
27  
28 
29       query.append(" FROM ").append(tableName);
30 
31       query.append(" AS ").append(tableName); //in hsqldb this is necessary
32 
33       if (conditions != null && conditions.length() > 0) {
34 
35         query.append(" WHERE (").append(conditions).append(")");
36 
37       }
38 
39  
40 
41       String orderBy = dbConf.getInputOrderBy();
42 
43       if (orderBy != null && orderBy.length() > 0) {
44 
45         query.append(" ORDER BY ").append(orderBy);
46 
47       }
48 
49     } else {
50 
51       //PREBUILT QUERY
52 
53       query.append(dbConf.getInputQuery());
54 
55     }
56 
57         
58 
59     try {
60 
61       query.append(" LIMIT ").append(split.getLength()); //问题所在
62 
63       query.append(" OFFSET ").append(split.getStart());
64 
65     } catch (IOException ex) {
66 
67       // Ignore, will not throw.
68 
69     }
70 
71  
72 
73     return query.toString();
74 
75   }
View Code

终于找到原因了。

　　原来，hadoop只实现了Mysql的DBRecordReader（MySQLDBRecordReader）和ORACLE的DBRecordReader（OracleDBRecordReader）。

原因找到了，我参考着OracleDBRecordReader实现了MSSQL SERVER的DBRecordReader代码如下：

　　MSSQLDBInputFormat的代码：

 1 /**
 2  * 
 3  */
 4 package org.apache.hadoop.mapreduce.lib.db;
 5 
 6 import java.io.IOException;
 7 import java.sql.SQLException;
 8 
 9 import org.apache.hadoop.conf.Configuration;
10 import org.apache.hadoop.io.LongWritable;
11 import org.apache.hadoop.mapreduce.Job;
12 import org.apache.hadoop.mapreduce.RecordReader;
13 
14 /**
15  * @author summer
16  *  MICROSOFT SQL SERVER
17  */
18 public class MSSQLDBInputFormat<T extends DBWritable> extends DBInputFormat<T> {
19 
20     public static void setInput(Job job,
21               Class<? extends DBWritable> inputClass,
22               String inputQuery, String inputCountQuery,String rowId) {
23             job.setInputFormatClass(MSSQLDBInputFormat.class);
24             DBConfiguration dbConf = new DBConfiguration(job.getConfiguration());
25             dbConf.setInputClass(inputClass);
26             dbConf.setInputQuery(inputQuery);
27             dbConf.setInputCountQuery(inputCountQuery);
28             dbConf.setInputFieldNames(new String[]{rowId});
29           }
30     
31     @Override
32     protected RecordReader<LongWritable, T> createDBRecordReader(
33             org.apache.hadoop.mapreduce.lib.db.DBInputFormat.DBInputSplit split,
34             Configuration conf) throws IOException {
35         
36          @SuppressWarnings("unchecked")
37             Class<T> inputClass = (Class<T>) (dbConf.getInputClass());
38             try {
39              
40                 return new MSSQLDBRecordReader<T>(split, inputClass,
41                     conf, createConnection(), getDBConf(), conditions, fieldNames,
42                     tableName);
43             
44             } catch (SQLException ex) {
45               throw new IOException(ex.getMessage());
46             }
47         
48         
49     }
50 
51     
52 }
View Code

　　MSSQLDBRecordReader的代码：

 1 /**
 2  * 
 3  */
 4 package org.apache.hadoop.mapreduce.lib.db;
 5 
 6 import java.io.IOException;
 7 import java.sql.Connection;
 8 import java.sql.SQLException;
 9 
10 import org.apache.hadoop.conf.Configuration;
11 
12 
13 /**
14  * @author summer
15  *
16  */
17 public class MSSQLDBRecordReader <T extends DBWritable> extends DBRecordReader<T>{
18 
19     public MSSQLDBRecordReader(DBInputFormat.DBInputSplit split, 
20               Class<T> inputClass, Configuration conf, Connection conn, DBConfiguration dbConfig,
21               String cond, String [] fields, String table) throws SQLException {
22         super(split, inputClass, conf, conn, dbConfig, cond, fields, table);
23         
24     }
25 
26     @Override
27     protected String getSelectQuery() {
28          StringBuilder query = new StringBuilder();
29             DBConfiguration dbConf = getDBConf();
30             String conditions = getConditions();
31             String tableName = getTableName();
32             String [] fieldNames = getFieldNames();
33 
34             // Oracle-specific codepath to use rownum instead of LIMIT/OFFSET.
35             if(dbConf.getInputQuery() == null) {
36               query.append("SELECT ");
37           
38               for (int i = 0; i < fieldNames.length; i++) {
39                 query.append(fieldNames[i]);
40                 if (i != fieldNames.length -1) {
41                   query.append(", ");
42                 }
43               }
44           
45               query.append(" FROM ").append(tableName);
46               if (conditions != null && conditions.length() > 0)
47                 query.append(" WHERE ").append(conditions);
48               String orderBy = dbConf.getInputOrderBy();
49               if (orderBy != null && orderBy.length() > 0) {
50                 query.append(" ORDER BY ").append(orderBy);
51               }
52             } else {
53               //PREBUILT QUERY
54               query.append(dbConf.getInputQuery());
55             }
56                 
57             try {
58               DBInputFormat.DBInputSplit split = getSplit();
59               if (split.getLength() > 0){
60                 String querystring = query.toString();
61                 String id = fieldNames[0];
62                 query = new StringBuilder();
63                 query.append("SELECT TOP "+split.getLength()+"* FROM ( ");
64                 query.append(querystring);
65                 query.append(" ) a WHERE " + id +" NOT IN (SELECT TOP ").append(split.getEnd());
66                 query.append(" "+id +" FROM (");
67                 query.append(querystring);
68                 query.append(" ) b");
69                 query.append(" )");
70                 System.out.println("----------------------MICROSOFT SQL SERVER QUERY STRING---------------------------");
71                 System.out.println(query.toString());
72                 System.out.println("----------------------MICROSOFT SQL SERVER QUERY STRING---------------------------");
73               }
74             } catch (IOException ex) {
75               // ignore, will not throw.
76             }              
77 
78             return query.toString();
79     }
80     
81     
82 
83 }
View Code

mapreduce的代码

  1 /**
  2  * 
  3  */
  4 package com.nltk.sns.mapreduce;
  5 
  6 import java.io.IOException;
  7 import java.util.List;
  8 
  9 import org.apache.hadoop.conf.Configuration;
 10 import org.apache.hadoop.fs.FileSystem;
 11 import org.apache.hadoop.fs.Path;
 12 import org.apache.hadoop.io.LongWritable;
 13 import org.apache.hadoop.io.Text;
 14 import org.apache.hadoop.mapreduce.Job;
 15 import org.apache.hadoop.mapreduce.MRJobConfig;
 16 import org.apache.hadoop.mapreduce.Mapper;
 17 import org.apache.hadoop.mapreduce.lib.db.DBConfiguration;
 18 import org.apache.hadoop.mapreduce.lib.db.MSSQLDBInputFormat;
 19 import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;
 20 
 21 
 22 
 23 
 24 
 25 
 26 
 27 import com.nltk.utils.ETLUtils;
 28 
 29 /**
 30  * @author summer
 31  *
 32  */
 33 public class LawDataEtl {
 34 
 35     public static class CaseETLMapper extends 
 36         Mapper<LongWritable, LawCaseRecord, LongWritable, Text>{
 37 
 38         static final int step = 6;
 39         
 40         LongWritable key = new LongWritable(1);
 41         Text value = new Text();
 42         
 43         @Override
 44         protected void map(
 45                 LongWritable key,
 46                 LawCaseRecord lawCaseRecord,
 47                 Mapper<LongWritable, LawCaseRecord, LongWritable, Text>.Context context)
 48                 throws IOException, InterruptedException {
 49             
 50             System.out.println("-----------------------------"+lawCaseRecord+"------------------------------");
 51             
 52             key.set(lawCaseRecord.id);
 53             String source = ETLUtils.format(lawCaseRecord.source);
 54             List<LawCaseWord> words = ETLUtils.split(lawCaseRecord.id,source, step);
 55             for(LawCaseWord w:words){
 56                 value.set(w.toString());
 57                 context.write(key, value);
 58             }
 59         }
 60     }
 61     
 62                 
 63     static final String driverClass = "com.microsoft.sqlserver.jdbc.SQLServerDriver";
 64     static final String dbUrl = "jdbc:sqlserver://192.168.0.1:1433;DatabaseName=XXX";
 65     static final String uid = "XXX";
 66     static final String pwd = "XXX";
 67     static final String inputQuery = "select id,source from tablename where id<1000";
 68     static final String inputCountQuery = "select count(1) from LawDB.dbo.case_source where id<1000";
 69     static final String jarClassPath = "/user/lib/sqljdbc4.jar";
 70     static final String outputPath = "hdfs://ubuntu:9000/user/test";
 71     static final String rowId = "id";
 72     
 73     public static Job configureJob(Configuration conf) throws Exception{
 74         
 75         String jobName = "etlcase";
 76         Job job =  Job.getInstance(conf, jobName);
 77 
 78         job.addFileToClassPath(new Path(jarClassPath));
 79         MSSQLDBInputFormat.setInput(job, LawCaseRecord.class, inputQuery, inputCountQuery,rowId);
 80         job.setJarByClass(LawDataEtl.class);
 81         
 82         FileOutputFormat.setOutputPath(job, new Path(outputPath));
 83         
 84         job.setMapOutputKeyClass(LongWritable.class);
 85         job.setMapOutputValueClass(Text.class);
 86         job.setOutputKeyClass(LongWritable.class);
 87         job.setOutputValueClass(Text.class);
 88         job.setMapperClass(CaseETLMapper.class);
 89         
 90         return job;
 91     }
 92     
 93     public static void main(String[] args) throws Exception{
 94         
 95         Configuration conf = new Configuration();
 96         FileSystem fs = FileSystem.get(conf);
 97         fs.delete(new Path(outputPath), true);
 98         
 99         DBConfiguration.configureDB(conf, driverClass, dbUrl, uid, pwd);
100         conf.set(MRJobConfig.NUM_MAPS, String.valueOf(10));
101         Job job = configureJob(conf);
102         System.out.println("------------------------------------------------");
103         System.out.println(conf.get(DBConfiguration.DRIVER_CLASS_PROPERTY));
104         System.out.println(conf.get(DBConfiguration.URL_PROPERTY));
105         System.out.println(conf.get(DBConfiguration.USERNAME_PROPERTY));
106         System.out.println(conf.get(DBConfiguration.PASSWORD_PROPERTY));
107         System.out.println("------------------------------------------------");
108         System.exit(job.waitForCompletion(true) ? 0 : 1);  
109         
110     }
111 }
View Code

辅助类的代码：

 1 /**
 2  * 
 3  */
 4 package com.nltk.sns;
 5 
 6 import java.util.ArrayList;
 7 import java.util.List;
 8 
 9 import org.apache.commons.lang.StringUtils;
10 
11 
12 
13 
14 
15 /**
16  * @author summer
17  *
18  */
19 public class ETLUtils {
20 
21     public final static String NULL_CHAR = "";
22     public final static String PUNCTUATION_REGEX = "[(\pP)&&[^\|\｛\｝\＃]]+";
23     public final static String WHITESPACE_REGEX = "[\p{Space}]+";
24     
25     public static String format(String s){
26         
27         return s.replaceAll(PUNCTUATION_REGEX, NULL_CHAR).replaceAll(WHITESPACE_REGEX, NULL_CHAR); 
28     }
29     
30     public static List<String> split(String s,int stepN){
31         
32         List<String> splits = new ArrayList<String>();
33         if(StringUtils.isEmpty(s) || stepN<1)
34             return splits;
35         int len = s.length();
36         if(len<=stepN)
37             splits.add(s);
38         else{
39             for(int j=1;j<=stepN;j++)
40                 for(int i=0;i<=len-j;i++){
41                     String key = StringUtils.mid(s, i,j);
42                     if(StringUtils.isEmpty(key))
43                         continue;
44                     splits.add(key);
45                 }
46         }
47         return splits;
48         
49     }
50     
51     public static void main(String[] args){
52         
53         String s="谢婷婷等与姜波等";
54         int stepN = 2;
55         List<String> splits = split(s,stepN);
56         System.out.println(splits);
57     }
58 }
View Code

运行成功了

 

代码初略的实现，主要是为了满足我的需求，大家可以根据自己的需要进行修改。

　　实际上DBRecordReader作者实现的并不好，我们来看DBRecordReader、MySQLDBRecordReader和OracleDBRecordReader源码，DBRecordReader和MySQLDBRecordReader耦合度太高。一般而言，就是对于没有具体实现的数据库DBRecordReader也应该做到运行不报异常，无非就是采用单一的SPLIT和单一的MAP。

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原文地址：https://www.cnblogs.com/bigdatafly/p/5018076.html