Avro 简明教程

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="   http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">

   <modelVersion>4.0.0</modelVersion>
   <groupId>Test</groupId>
   <artifactId>Test</artifactId>
   <version>0.0.1-SNAPSHOT</version>

   <build>
      <sourceDirectory>src</sourceDirectory>
      <plugins>
         <plugin>
            <artifactId>maven-compiler-plugin</artifactId>
            <version>3.1</version>

            <configuration>
               <source>1.7</source>
               <target>1.7</target>
            </configuration>

         </plugin>
      </plugins>
   </build>

   <dependencies>
      <dependency>
         <groupId>org.apache.avro</groupId>
         <artifactId>avro</artifactId>
         <version>1.7.7</version>
      </dependency>

      <dependency>
         <groupId>org.apache.avro</groupId>
         <artifactId>avro-tools</artifactId>
         <version>1.7.7</version>
      </dependency>

      <dependency>
         <groupId>org.apache.logging.log4j</groupId>
         <artifactId>log4j-api</artifactId>
         <version>2.0-beta9</version>
      </dependency>

      <dependency>
         <groupId>org.apache.logging.log4j</groupId>
         <artifactId>log4j-core</artifactId>
         <version>2.0-beta9</version>
      </dependency>

   </dependencies>

</project>

#class path for Avro
export CLASSPATH=$CLASSPATH://home/Hadoop/Avro_Work/jars/*

{
   "type" : "record",
   "namespace" : "Tutorialspoint",
   "name" : "Employee",
   "fields" : [
      { "name" : "Name" , "type" : "string" },
      { "name" : "Age" , "type" : "int" }
   ]
}

{
   "namespace": "tutorialspoint.com",
   "type": "record",
   "name": "emp",
   "fields": [
      {"name": "name", "type": "string"},
      {"name": "id", "type": "int"},
      {"name": "salary", "type": "int"},
      {"name": "age", "type": "int"},
      {"name": "address", "type": "string"}
   ]
}

import java.io.File;
import java.io.IOException;

import org.apache.avro.file.DataFileWriter;
import org.apache.avro.io.DatumWriter;
import org.apache.avro.specific.SpecificDatumWriter;

public class Serialize {
   public static void main(String args[]) throws IOException{

      //Instantiating generated emp class
      emp e1=new emp();

      //Creating values according the schema
      e1.setName("omar");
      e1.setAge(21);
      e1.setSalary(30000);
      e1.setAddress("Hyderabad");
      e1.setId(001);

      emp e2=new emp();

      e2.setName("ram");
      e2.setAge(30);
      e2.setSalary(40000);
      e2.setAddress("Hyderabad");
      e2.setId(002);

      emp e3=new emp();

      e3.setName("robbin");
      e3.setAge(25);
      e3.setSalary(35000);
      e3.setAddress("Hyderabad");
      e3.setId(003);

      //Instantiate DatumWriter class
      DatumWriter<emp> empDatumWriter = new SpecificDatumWriter<emp>(emp.class);
      DataFileWriter<emp> empFileWriter = new DataFileWriter<emp>(empDatumWriter);

      empFileWriter.create(e1.getSchema(), new File("/home/Hadoop/Avro_Work/with_code_gen/emp.avro"));

      empFileWriter.append(e1);
      empFileWriter.append(e2);
      empFileWriter.append(e3);

      empFileWriter.close();

      System.out.println("data successfully serialized");
   }
}

$ cd home/Hadoop/Avro_work/with_code_gen/

$ javac Serialize.java
$ java Serialize

import java.io.File;
import java.io.IOException;

import org.apache.avro.file.DataFileReader;
import org.apache.avro.io.DatumReader;
import org.apache.avro.specific.SpecificDatumReader;

public class Deserialize {
   public static void main(String args[]) throws IOException{

      //DeSerializing the objects
      DatumReader<emp> empDatumReader = new SpecificDatumReader<emp>(emp.class);

      //Instantiating DataFileReader
      DataFileReader<emp> dataFileReader = new DataFileReader<emp>(new
         File("/home/Hadoop/Avro_Work/with_code_genfile/emp.avro"), empDatumReader);
      emp em=null;

      while(dataFileReader.hasNext()){

         em=dataFileReader.next(em);
         System.out.println(em);
      }
   }
}

$ cd home/Hadoop/Avro_work/with_code_gen/

$ javac Deserialize.java
$ java Deserialize

import java.io.File;
import java.io.IOException;

import org.apache.avro.Schema;
import org.apache.avro.file.DataFileWriter;

import org.apache.avro.generic.GenericData;
import org.apache.avro.generic.GenericDatumWriter;
import org.apache.avro.generic.GenericRecord;

import org.apache.avro.io.DatumWriter;

public class Seriali {
   public static void main(String args[]) throws IOException{

      //Instantiating the Schema.Parser class.
      Schema schema = new Schema.Parser().parse(new File("/home/Hadoop/Avro/schema/emp.avsc"));

      //Instantiating the GenericRecord class.
      GenericRecord e1 = new GenericData.Record(schema);

      //Insert data according to schema
      e1.put("name", "ramu");
      e1.put("id", 001);
      e1.put("salary",30000);
      e1.put("age", 25);
      e1.put("address", "chenni");

      GenericRecord e2 = new GenericData.Record(schema);

      e2.put("name", "rahman");
      e2.put("id", 002);
      e2.put("salary", 35000);
      e2.put("age", 30);
      e2.put("address", "Delhi");

      DatumWriter<GenericRecord> datumWriter = new GenericDatumWriter<GenericRecord>(schema);

      DataFileWriter<GenericRecord> dataFileWriter = new DataFileWriter<GenericRecord>(datumWriter);
      dataFileWriter.create(schema, new File("/home/Hadoop/Avro_work/without_code_gen/mydata.txt"));

      dataFileWriter.append(e1);
      dataFileWriter.append(e2);
      dataFileWriter.close();

      System.out.println(“data successfully serialized”);
   }
}

$ cd home/Hadoop/Avro_work/without_code_gen/

$ javac Serialize.java
$ java Serialize

public class Deserialize {
   public static void main(String args[]) throws Exception{

      //Instantiating the Schema.Parser class.
      Schema schema = new Schema.Parser().parse(new File("/home/Hadoop/Avro/schema/emp.avsc"));
      DatumReader<GenericRecord> datumReader = new GenericDatumReader<GenericRecord>(schema);
      DataFileReader<GenericRecord> dataFileReader = new DataFileReader<GenericRecord>(new File("/home/Hadoop/Avro_Work/without_code_gen/mydata.txt"), datumReader);
      GenericRecord emp = null;

      while (dataFileReader.hasNext()) {
         emp = dataFileReader.next(emp);
         System.out.println(emp);
      }
      System.out.println("hello");
   }
}

$ cd home/Hadoop/Avro_work/without_code_gen/

$ javac Deserialize.java
$ java Deserialize