问题陈述:
因此,要求编写一种通用映射表,该映射表可以获取任何Avro数据,但以Avro格式生成输出,并具有与传入相同的模式。
代码(经过多次尝试,这是我到达的距离)
驱动程序
public class AvroDriver extends Configured implements Tool {
public int run(String[] args) throws Exception {
Job job = new Job(getConf());
job.setJarByClass(AvroMapper.class);
job.setJobName("Avro With Xml Mapper");
job.getConfiguration().setBoolean("mapreduce.input.fileinputformat.input.dir.recursive", true);
//This is required to use avro-1.7.6 and above
job.getConfiguration().set("mapreduce.job.user.classpath.first", "true");
FileInputFormat.addInputPath(job, new Path(args[0]));
FileOutputFormat.setOutputPath(job, new Path(args[1]));
job.setInputFormatClass(AvroKeyInputFormat.class);
job.setMapperClass(AvroMapper.class);
Schema schema = new Schema.Parser().parse(new File(args[2]));
AvroJob.setInputKeySchema(job, schema);
job.setOutputFormatClass(AvroKeyOutputFormat.class);
job.setMapOutputKeyClass(AvroKey.class);
AvroJob.setOutputKeySchema(job, schema);
job.setNumReduceTasks(0);
return (job.waitForCompletion(true) ? 0 : 1);
}
public static void main(String[] args) throws Exception {
int res = ToolRunner.run(new AvroDriver(), args);
System.exit(res);
}
}
映射器
public static class AvroMapper extends Mapper<AvroKey<GenericData.Record>, NullWritable, AvroKey<GenericData>, NullWritable> {
@Override
public void map(AvroKey<GenericData.Record> key, NullWritable value, Context context) throws IOException, InterruptedException {
try {
System.out.println("Specific Record - " + key);
System.out.println("Datum :: " + key.datum());
System.out.println("Schema :: " + key.datum().getSchema());
List<Field> fields = key.datum().getSchema().getFields();
GenericRecord record = new GenericData.Record(key.datum().getSchema());
for(Field f : fields) {
System.out.println("Field Name - " + f.name());
record.put(f.name(), key.datum().get(f.name()));
}
System.out.println("Record - " + record);
GenericData d = new GenericData();
d.newRecord(record, key.datum().getSchema());
AvroKey<GenericData> outkey = new AvroKey<GenericData>(d);
System.out.println("Generic Record (Avro Key) - " + outkey);
context.write(outkey, NullWritable.get());
} catch (Exception e) {
e.printStackTrace();
throw new IOException(e.getMessage());
}
}
}
命令
Avro模式样本
{ "type" : "record", "name" : "Entity", "namespace" : "com.sample.avro", "fields".......
我在运行 map 时遇到的问题减少了
环境
HDP 2.3沙箱
有什么想法吗?
更新了
我尝试了以下但相同的结果
public static class AvroMapper extends Mapper<AvroKey<GenericData.Record>, NullWritable, AvroKey<GenericData>, NullWritable> {
@Override
public void map(AvroKey<GenericData.Record> key, NullWritable value, Context context) throws IOException, InterruptedException {
try {
System.out.println("Specific Record - " + key);
System.out.println("Datum :: " + key.datum());
System.out.println("Schema :: " + key.datum().getSchema());
List<Field> fields = key.datum().getSchema().getFields();
Schema s = Schema.createRecord(key.datum().getSchema().getName(), null, key.datum().getSchema().getNamespace(), false);
List<Field> outFields = new ArrayList<Field>();
for(Field f : fields) {
System.out.println("Field Name - " + f.name());
Schema.Field f1 = new Schema.Field(f.name(),Schema.create(Schema.Type.STRING), null,null);
outFields.add(f1);
}
s.setFields(outFields);
System.out.println("Out Schema - " + s);
GenericRecord record = new GenericData.Record(s);
for(Field f : fields) {
record.put(f.name(), key.datum().get(f.name()));
}
System.out.println("Record - " + record);
GenericData d = new GenericData();
d.newRecord(record, s);
AvroKey<GenericData> outkey = new AvroKey<GenericData>(d);
System.out.println("Generic Record (Avro Key) - " + outkey.datum());
context.write(outkey, NullWritable.get());
} catch (Exception e) {
e.printStackTrace();
}
}
}
请注意,将 map 输入的Avro效果很好,但是此处出现的是Avro格式的输出。
最佳答案
最后,我找到了答案和映射器代码,如下所示。
我没有使用GenericData发出AvroKey,而是更改为发出GenericData.Record。
public static class AvroMapper extends Mapper<AvroKey<GenericData.Record>, NullWritable, AvroKey<GenericData.Record>, NullWritable> {
@Override
public void map(AvroKey<GenericData.Record> key, NullWritable value, Context context) throws IOException, InterruptedException {
try {
System.out.println("Specific Record - " + key);
System.out.println("Datum :: " + key.datum());
System.out.println("Schema :: " + key.datum().getSchema());
List<Field> fields = key.datum().getSchema().getFields();
Schema s = Schema.createRecord(key.datum().getSchema().getName(), null, key.datum().getSchema().getNamespace(), false);
List<Field> outFields = new ArrayList<Field>();
for(Field f : fields) {
System.out.println("Field Name - " + f.name());
Schema.Field f1 = new Schema.Field(f.name(),Schema.create(Schema.Type.STRING), null,null);
outFields.add(f1);
}
s.setFields(outFields);
System.out.println("Out Schema - " + s);
GenericData.Record record = new GenericData.Record(s);
for(Field f : fields) {
record.put(f.name(), key.datum().get(f.name()));
}
System.out.println("Record - " + record);
AvroKey<GenericData.Record> outkey = new AvroKey<GenericData.Record>(record);
System.out.println("Generic Record (Avro Key) - " + outkey.datum());
context.write(outkey, NullWritable.get());
} catch (Exception e) {
e.printStackTrace();
System.out.println(e);
System.out.println(e.getMessage());
throw new IOException(e.getMessage());
}
}
}