我正在构建一个MapR-ES Java生产者,该生产者通过JDBC连接到Oracle,并获取结果集以发布到流中。
我想将填充的类对象序列化为Avro字符串,作为发布者的消息。
我已经使用Maven Apache Avro插件为我的类对象生成了一个Avro字符串
Schema schema = ReflectionData.get().getSchema(MyClass.class);
但是,如果我有一个完全填充的MyClass对象,如何用架构和填充的数据生成Avro字符串?
我还没有找到任何好的例子。任何帮助表示赞赏。
答案 0 :(得分:0)
假设我在Java中有ReflectedCustomer类。
import org.apache.avro.reflect.Nullable;
public class ReflectedCustomer {
private String firstName;
private String lastName;
@Nullable private String nickName;
// needed by the reflection
public ReflectedCustomer(){}
public ReflectedCustomer(String firstName, String lastName, String nickName) {
this.firstName = firstName;
this.lastName = lastName;
this.nickName = nickName;
}
public String getFirstName() {
return firstName;
}
public void setFirstName(String firstName) {
this.firstName = firstName;
}
public String fullName(){
return this.firstName + " " + this.lastName + " " + this.nickName;
}
public String getNickName() {
return nickName;
}
public void setNickName(String nickName) {
this.nickName = nickName;
}
}
下面的代码将使用上面的ReflectedCustomer并生成Avro字符串,并将其读回。
import org.apache.avro.Schema;
import org.apache.avro.file.CodecFactory;
import org.apache.avro.file.DataFileReader;
import org.apache.avro.file.DataFileWriter;
import org.apache.avro.io.DatumReader;
import org.apache.avro.io.DatumWriter;
import org.apache.avro.reflect.ReflectData;
import org.apache.avro.reflect.ReflectDatumReader;
import org.apache.avro.reflect.ReflectDatumWriter;
import java.io.File;
import java.io.IOException;
public class ReflectionExamples {
public static void main(String[] args) {
// here we use reflection to determine the schema
Schema schema = ReflectData.get().getSchema(ReflectedCustomer.class);
System.out.println("schema = " + schema.toString(true));
// create a file of ReflectedCustomers
try {
System.out.println("Writing customer-reflected.avro");
File file = new File("customer-reflected.avro");
DatumWriter<ReflectedCustomer> writer = new ReflectDatumWriter<>(ReflectedCustomer.class);
DataFileWriter<ReflectedCustomer> out = new DataFileWriter<>(writer)
.setCodec(CodecFactory.deflateCodec(9))
.create(schema, file);
out.append(new ReflectedCustomer("Bill", "Clark", "The Rocket"));
out.close();
} catch (IOException e) {
e.printStackTrace();
}
// read from an avro into our Reflected class
// open a file of ReflectedCustomers
try {
System.out.println("Reading customer-reflected.avro");
File file = new File("customer-reflected.avro");
DatumReader<ReflectedCustomer> reader = new ReflectDatumReader<>(ReflectedCustomer.class);
DataFileReader<ReflectedCustomer> in = new DataFileReader<>(file, reader);
// read ReflectedCustomers from the file & print them as JSON
for (ReflectedCustomer reflectedCustomer : in) {
System.out.println(reflectedCustomer.fullName());
}
// close the input file
in.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}