This topic describes an example of using resources in MapReduce.
Preparations
- Prepare the JAR package of the test program. In this topic, the JAR package is named mapreduce-examples.jar and stored in the local path data\resources.
- On the MaxCompute client, perform the following operations to prepare test tables
and resources:
- Create test tables.
create table mr_upload_src(key bigint, value string);
- Add test resources.
add jar data\resources\mapreduce-examples.jar -f; add file data\resources\import.txt -f;
- The import.txt file contains the following content:
1000,odps
- Create test tables.
Procedure
Run the following code on the MaxCompute client to upload the data in the test resources
to the mr_upload_src table:
jar -resources mapreduce-examples.jar,import.txt -classpath data\resources\mapreduce-examples.jar
com.aliyun.odps.mapred.open.example.Upload import.txt mr_upload_src;
Expected result
The job runs normally. The following data is returned in the mr_upload_src table:
+------------+------------+
| key | value |
+------------+------------+
| 1000 | odps |
+------------+------------+
Sample code
package com.aliyun.odps.mapred.open.example;
import java.io.BufferedInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import com.aliyun.odps.data.Record;
import com.aliyun.odps.data.TableInfo;
import com.aliyun.odps.mapred.JobClient;
import com.aliyun.odps.mapred.MapperBase;
import com.aliyun.odps.mapred.TaskContext;
import com.aliyun.odps.mapred.conf.JobConf;
import com.aliyun.odps.mapred.utils.InputUtils;
import com.aliyun.odps.mapred.utils.OutputUtils;
import com.aliyun.odps.mapred.utils.SchemaUtils;
/**
* Upload
*
* Import data from text file into table
*
**/
public class Upload {
public static class UploadMapper extends MapperBase {
@Override
public void setup(TaskContext context) throws IOException {
Record record = context.createOutputRecord();
StringBuilder importdata = new StringBuilder();
BufferedInputStream bufferedInput = null;
try {
byte[] buffer = new byte[1024];
int bytesRead = 0;
String filename = context.getJobConf().get("import.filename");
bufferedInput = context.readResourceFileAsStream(filename);
while ((bytesRead = bufferedInput.read(buffer)) != -1) {
String chunk = new String(buffer, 0, bytesRead);
importdata.append(chunk);
}
String lines[] = importdata.toString().split("\n");
for (int i = 0; i < lines.length; i++) {
String[] ss = lines[i].split(",");
record.set(0, Long.parseLong(ss[0].trim()));
record.set(1, ss[1].trim());
context.write(record);
}
} catch (FileNotFoundException ex) {
throw new IOException(ex);
} catch (IOException ex) {
throw new IOException(ex);
} finally {
}
}
@Override
public void map(long recordNum, Record record, TaskContext context)
throws IOException {
}
}
public static void main(String[] args) throws Exception {
if (args.length != 2) {
System.err.println("Usage: Upload <import_txt> <out_table>");
System.exit(2);
}
JobConf job = new JobConf();
job.setMapperClass(UploadMapper.class);
/** Specify the resource name, which can be obtained in the map stage by using the JobConf interface. */
job.set("import.filename", args[0]);
/** Explicitly set the number of reducers to 0 for map-only jobs. */
job.setNumReduceTasks(0);
job.setMapOutputKeySchema(SchemaUtils.fromString("key:bigint"));
job.setMapOutputValueSchema(SchemaUtils.fromString("value:string"));
InputUtils.addTable(TableInfo.builder().tableName("mr_empty").build(), job);
OutputUtils.addTable(TableInfo.builder().tableName(args[1]).build(), job);
JobClient.runJob(job);
}
}
You can use one of the following methods to set the JobConf configuration file:
- Use the JobConf interface in SDK. This method is used in the preceding example.
- Use the -conf parameter in a jar command to specify a new JobConf configuration file.