通過 Java 文件使用 Avro Schema 別名

Question

我嘗試了以下 avro 架構：

{
  "type": "record",
  "name": "Tests",
  "fields": [
    {
      "name": "name",
      "alias": "first_name",
      "type": "string",
      "default": ""
    }
  ]
}

當我使用 avro 工具“編譯模式”時，我得到了相應的 java 文件。

/**
 * Autogenerated by Avro
 *
 * DO NOT EDIT DIRECTLY
 */

import org.apache.avro.generic.GenericArray;
import org.apache.avro.specific.SpecificData;
import org.apache.avro.util.Utf8;
import org.apache.avro.message.BinaryMessageEncoder;
import org.apache.avro.message.BinaryMessageDecoder;
import org.apache.avro.message.SchemaStore;

@org.apache.avro.specific.AvroGenerated
public class Tests extends org.apache.avro.specific.SpecificRecordBase implements org.apache.avro.specific.SpecificRecord {
  private static final long serialVersionUID = 8259235364501890516L;
  public static final org.apache.avro.Schema SCHEMA$ = new org.apache.avro.Schema.Parser().parse("{\"type\":\"record\",\"name\":\"Tests\",\"fields\":[{\"name\":\"name\",\"type\":\"string\",\"default\":\"\",\"alias\":\"first_name\"}]}");
  public static org.apache.avro.Schema getClassSchema() { return SCHEMA$; }

  private static SpecificData MODEL$ = new SpecificData();

  private static final BinaryMessageEncoder<Tests> ENCODER =
      new BinaryMessageEncoder<Tests>(MODEL$, SCHEMA$);

  private static final BinaryMessageDecoder<Tests> DECODER =
      new BinaryMessageDecoder<Tests>(MODEL$, SCHEMA$);

  /**
   * Return the BinaryMessageEncoder instance used by this class.
   * @return the message encoder used by this class
   */
  public static BinaryMessageEncoder<Tests> getEncoder() {
    return ENCODER;
  }

  /**
   * Return the BinaryMessageDecoder instance used by this class.
   * @return the message decoder used by this class
   */
  public static BinaryMessageDecoder<Tests> getDecoder() {
    return DECODER;
  }

  /**
   * Create a new BinaryMessageDecoder instance for this class that uses the specified {@link SchemaStore}.
   * @param resolver a {@link SchemaStore} used to find schemas by fingerprint
   * @return a BinaryMessageDecoder instance for this class backed by the given SchemaStore
   */
  public static BinaryMessageDecoder<Tests> createDecoder(SchemaStore resolver) {
    return new BinaryMessageDecoder<Tests>(MODEL$, SCHEMA$, resolver);
  }

  /**
   * Serializes this Tests to a ByteBuffer.
   * @return a buffer holding the serialized data for this instance
   * @throws java.io.IOException if this instance could not be serialized
   */
  public java.nio.ByteBuffer toByteBuffer() throws java.io.IOException {
    return ENCODER.encode(this);
  }

  /**
   * Deserializes a Tests from a ByteBuffer.
   * @param b a byte buffer holding serialized data for an instance of this class
   * @return a Tests instance decoded from the given buffer
   * @throws java.io.IOException if the given bytes could not be deserialized into an instance of this class
   */
  public static Tests fromByteBuffer(
      java.nio.ByteBuffer b) throws java.io.IOException {
    return DECODER.decode(b);
  }

   private java.lang.CharSequence name;

  /**
   * Default constructor.  Note that this does not initialize fields
   * to their default values from the schema.  If that is desired then
   * one should use <code>newBuilder()</code>.
   */
  public Tests() {}

  /**
   * All-args constructor.
   * @param name The new value for name
   */
  public Tests(java.lang.CharSequence name) {
    this.name = name;
  }

  public org.apache.avro.specific.SpecificData getSpecificData() { return MODEL$; }
  public org.apache.avro.Schema getSchema() { return SCHEMA$; }
  // Used by DatumWriter.  Applications should not call.
  public java.lang.Object get(int field$) {
    switch (field$) {
    case 0: return name;
    default: throw new IndexOutOfBoundsException("Invalid index: " + field$);
    }
  }

  // Used by DatumReader.  Applications should not call.
  @SuppressWarnings(value="unchecked")
  public void put(int field$, java.lang.Object value$) {
    switch (field$) {
    case 0: name = (java.lang.CharSequence)value$; break;
    default: throw new IndexOutOfBoundsException("Invalid index: " + field$);
    }
  }

  /**
   * Gets the value of the 'name' field.
   * @return The value of the 'name' field.
   */
  public java.lang.CharSequence getName() {
    return name;
  }


  /**
   * Sets the value of the 'name' field.
   * @param value the value to set.
   */
  public void setName(java.lang.CharSequence value) {
    this.name = value;
  }

  /**
   * Creates a new Tests RecordBuilder.
   * @return A new Tests RecordBuilder
   */
  public static Tests.Builder newBuilder() {
    return new Tests.Builder();
  }

  /**
   * Creates a new Tests RecordBuilder by copying an existing Builder.
   * @param other The existing builder to copy.
   * @return A new Tests RecordBuilder
   */
  public static Tests.Builder newBuilder(Tests.Builder other) {
    if (other == null) {
      return new Tests.Builder();
    } else {
      return new Tests.Builder(other);
    }
  }

  /**
   * Creates a new Tests RecordBuilder by copying an existing Tests instance.
   * @param other The existing instance to copy.
   * @return A new Tests RecordBuilder
   */
  public static Tests.Builder newBuilder(Tests other) {
    if (other == null) {
      return new Tests.Builder();
    } else {
      return new Tests.Builder(other);
    }
  }

  /**
   * RecordBuilder for Tests instances.
   */
  @org.apache.avro.specific.AvroGenerated
  public static class Builder extends org.apache.avro.specific.SpecificRecordBuilderBase<Tests>
    implements org.apache.avro.data.RecordBuilder<Tests> {

    private java.lang.CharSequence name;

    /** Creates a new Builder */
    private Builder() {
      super(SCHEMA$);
    }

    /**
     * Creates a Builder by copying an existing Builder.
     * @param other The existing Builder to copy.
     */
    private Builder(Tests.Builder other) {
      super(other);
      if (isValidValue(fields()[0], other.name)) {
        this.name = data().deepCopy(fields()[0].schema(), other.name);
        fieldSetFlags()[0] = other.fieldSetFlags()[0];
      }
    }

    /**
     * Creates a Builder by copying an existing Tests instance
     * @param other The existing instance to copy.
     */
    private Builder(Tests other) {
      super(SCHEMA$);
      if (isValidValue(fields()[0], other.name)) {
        this.name = data().deepCopy(fields()[0].schema(), other.name);
        fieldSetFlags()[0] = true;
      }
    }

    /**
      * Gets the value of the 'name' field.
      * @return The value.
      */
    public java.lang.CharSequence getName() {
      return name;
    }


    /**
      * Sets the value of the 'name' field.
      * @param value The value of 'name'.
      * @return This builder.
      */
    public Tests.Builder setName(java.lang.CharSequence value) {
      validate(fields()[0], value);
      this.name = value;
      fieldSetFlags()[0] = true;
      return this;
    }

    /**
      * Checks whether the 'name' field has been set.
      * @return True if the 'name' field has been set, false otherwise.
      */
    public boolean hasName() {
      return fieldSetFlags()[0];
    }


    /**
      * Clears the value of the 'name' field.
      * @return This builder.
      */
    public Tests.Builder clearName() {
      name = null;
      fieldSetFlags()[0] = false;
      return this;
    }

    @Override
    @SuppressWarnings("unchecked")
    public Tests build() {
      try {
        Tests record = new Tests();
        record.name = fieldSetFlags()[0] ? this.name : (java.lang.CharSequence) defaultValue(fields()[0]);
        return record;
      } catch (org.apache.avro.AvroMissingFieldException e) {
        throw e;
      } catch (java.lang.Exception e) {
        throw new org.apache.avro.AvroRuntimeException(e);
      }
    }
  }

  @SuppressWarnings("unchecked")
  private static final org.apache.avro.io.DatumWriter<Tests>
    WRITER$ = (org.apache.avro.io.DatumWriter<Tests>)MODEL$.createDatumWriter(SCHEMA$);

  @Override public void writeExternal(java.io.ObjectOutput out)
    throws java.io.IOException {
    WRITER$.write(this, SpecificData.getEncoder(out));
  }

  @SuppressWarnings("unchecked")
  private static final org.apache.avro.io.DatumReader<Tests>
    READER$ = (org.apache.avro.io.DatumReader<Tests>)MODEL$.createDatumReader(SCHEMA$);

  @Override public void readExternal(java.io.ObjectInput in)
    throws java.io.IOException {
    READER$.read(this, SpecificData.getDecoder(in));
  }

  @Override protected boolean hasCustomCoders() { return true; }

  @Override public void customEncode(org.apache.avro.io.Encoder out)
    throws java.io.IOException
  {
    out.writeString(this.name);

  }

  @Override public void customDecode(org.apache.avro.io.ResolvingDecoder in)
    throws java.io.IOException
  {
    org.apache.avro.Schema.Field[] fieldOrder = in.readFieldOrderIfDiff();
    if (fieldOrder == null) {
      this.name = in.readString(this.name instanceof Utf8 ? (Utf8)this.name : null);

    } else {
      for (int i = 0; i < 1; i++) {
        switch (fieldOrder[i].pos()) {
        case 0:
          this.name = in.readString(this.name instanceof Utf8 ? (Utf8)this.name : null);
          break;

        default:
          throw new java.io.IOException("Corrupt ResolvingDecoder.");
        }
      }
    }
  }
}

我想知道別名的 getter/setter 在哪里？ 我怎樣才能使用它？ 我知道如果我有 avro 記錄，那么我可以使用別名，但是如何使用該別名使用 Java 文件生成 Avro 記錄？

Answer 1

aliases負責為字段提供備用名稱。 來自 Apache Avro 的 文檔。

如果您將alias更新為aliases ，這將起作用：

{
  "type": "record",
  "name": "Tests",
  "fields": [
    {
      "name": "first_name",
      "aliases": ["former_name_of_field"],
      "type": "string",
      "default": ""
    }
  ]
}

這是支持模式演化的可選字段。

/**
 * Autogenerated by Avro
 *
 * DO NOT EDIT DIRECTLY
 */

import org.apache.avro.generic.GenericArray;
import org.apache.avro.specific.SpecificData;
import org.apache.avro.util.Utf8;
import org.apache.avro.message.BinaryMessageEncoder;
import org.apache.avro.message.BinaryMessageDecoder;
import org.apache.avro.message.SchemaStore;

@org.apache.avro.specific.AvroGenerated
public class Tests extends org.apache.avro.specific.SpecificRecordBase implements org.apache.avro.specific.SpecificRecord {
  private static final long serialVersionUID = -2440753220882419647L;
  public static final org.apache.avro.Schema SCHEMA$ = new org.apache.avro.Schema.Parser().parse("{\"type\":\"record\",\"name\":\"Tests\",\"fields\":[{\"name\":\"first_name\",\"type\":{\"type\":\"string\",\"avro.java.string\":\"String\"},\"default\":\"\",\"aliases\":[\"former_name_of_field\"]}]}");
  public static org.apache.avro.Schema getClassSchema() { return SCHEMA$; }

  private static SpecificData MODEL$ = new SpecificData();

  private static final BinaryMessageEncoder<Tests> ENCODER =
      new BinaryMessageEncoder<Tests>(MODEL$, SCHEMA$);

  private static final BinaryMessageDecoder<Tests> DECODER =
      new BinaryMessageDecoder<Tests>(MODEL$, SCHEMA$);

  /**
   * Return the BinaryMessageEncoder instance used by this class.
   * @return the message encoder used by this class
   */
  public static BinaryMessageEncoder<Tests> getEncoder() {
    return ENCODER;
  }

  /**
   * Return the BinaryMessageDecoder instance used by this class.
   * @return the message decoder used by this class
   */
  public static BinaryMessageDecoder<Tests> getDecoder() {
    return DECODER;
  }

  /**
   * Create a new BinaryMessageDecoder instance for this class that uses the specified {@link SchemaStore}.
   * @param resolver a {@link SchemaStore} used to find schemas by fingerprint
   * @return a BinaryMessageDecoder instance for this class backed by the given SchemaStore
   */
  public static BinaryMessageDecoder<Tests> createDecoder(SchemaStore resolver) {
    return new BinaryMessageDecoder<Tests>(MODEL$, SCHEMA$, resolver);
  }

  /**
   * Serializes this Tests to a ByteBuffer.
   * @return a buffer holding the serialized data for this instance
   * @throws java.io.IOException if this instance could not be serialized
   */
  public java.nio.ByteBuffer toByteBuffer() throws java.io.IOException {
    return ENCODER.encode(this);
  }

  /**
   * Deserializes a Tests from a ByteBuffer.
   * @param b a byte buffer holding serialized data for an instance of this class
   * @return a Tests instance decoded from the given buffer
   * @throws java.io.IOException if the given bytes could not be deserialized into an instance of this class
   */
  public static Tests fromByteBuffer(
      java.nio.ByteBuffer b) throws java.io.IOException {
    return DECODER.decode(b);
  }

  @Deprecated public java.lang.String first_name;

  /**
   * Default constructor.  Note that this does not initialize fields
   * to their default values from the schema.  If that is desired then
   * one should use <code>newBuilder()</code>.
   */
  public Tests() {}

  /**
   * All-args constructor.
   * @param first_name The new value for first_name
   */
  public Tests(java.lang.String first_name) {
    this.first_name = first_name;
  }

  public org.apache.avro.specific.SpecificData getSpecificData() { return MODEL$; }
  public org.apache.avro.Schema getSchema() { return SCHEMA$; }
  // Used by DatumWriter.  Applications should not call.
  public java.lang.Object get(int field$) {
    switch (field$) {
    case 0: return first_name;
    default: throw new IndexOutOfBoundsException("Invalid index: " + field$);
    }
  }

  // Used by DatumReader.  Applications should not call.
  @SuppressWarnings(value="unchecked")
  public void put(int field$, java.lang.Object value$) {
    switch (field$) {
    case 0: first_name = value$ != null ? value$.toString() : null; break;
    default: throw new IndexOutOfBoundsException("Invalid index: " + field$);
    }
  }

  /**
   * Gets the value of the 'first_name' field.
   * @return The value of the 'first_name' field.
   */
  public java.lang.String getFirstName() {
    return first_name;
  }


  /**
   * Sets the value of the 'first_name' field.
   * @param value the value to set.
   */
  public void setFirstName(java.lang.String value) {
    this.first_name = value;
  }

  /**
   * Creates a new Tests RecordBuilder.
   * @return A new Tests RecordBuilder
   */
  public static Tests.Builder newBuilder() {
    return new Tests.Builder();
  }

  /**
   * Creates a new Tests RecordBuilder by copying an existing Builder.
   * @param other The existing builder to copy.
   * @return A new Tests RecordBuilder
   */
  public static Tests.Builder newBuilder(Tests.Builder other) {
    if (other == null) {
      return new Tests.Builder();
    } else {
      return new Tests.Builder(other);
    }
  }

  /**
   * Creates a new Tests RecordBuilder by copying an existing Tests instance.
   * @param other The existing instance to copy.
   * @return A new Tests RecordBuilder
   */
  public static Tests.Builder newBuilder(Tests other) {
    if (other == null) {
      return new Tests.Builder();
    } else {
      return new Tests.Builder(other);
    }
  }

  /**
   * RecordBuilder for Tests instances.
   */
  @org.apache.avro.specific.AvroGenerated
  public static class Builder extends org.apache.avro.specific.SpecificRecordBuilderBase<Tests>
    implements org.apache.avro.data.RecordBuilder<Tests> {

    private java.lang.String first_name;

    /** Creates a new Builder */
    private Builder() {
      super(SCHEMA$);
    }

    /**
     * Creates a Builder by copying an existing Builder.
     * @param other The existing Builder to copy.
     */
    private Builder(Tests.Builder other) {
      super(other);
      if (isValidValue(fields()[0], other.first_name)) {
        this.first_name = data().deepCopy(fields()[0].schema(), other.first_name);
        fieldSetFlags()[0] = other.fieldSetFlags()[0];
      }
    }

    /**
     * Creates a Builder by copying an existing Tests instance
     * @param other The existing instance to copy.
     */
    private Builder(Tests other) {
      super(SCHEMA$);
      if (isValidValue(fields()[0], other.first_name)) {
        this.first_name = data().deepCopy(fields()[0].schema(), other.first_name);
        fieldSetFlags()[0] = true;
      }
    }

    /**
      * Gets the value of the 'first_name' field.
      * @return The value.
      */
    public java.lang.String getFirstName() {
      return first_name;
    }


    /**
      * Sets the value of the 'first_name' field.
      * @param value The value of 'first_name'.
      * @return This builder.
      */
    public Tests.Builder setFirstName(java.lang.String value) {
      validate(fields()[0], value);
      this.first_name = value;
      fieldSetFlags()[0] = true;
      return this;
    }

    /**
      * Checks whether the 'first_name' field has been set.
      * @return True if the 'first_name' field has been set, false otherwise.
      */
    public boolean hasFirstName() {
      return fieldSetFlags()[0];
    }


    /**
      * Clears the value of the 'first_name' field.
      * @return This builder.
      */
    public Tests.Builder clearFirstName() {
      first_name = null;
      fieldSetFlags()[0] = false;
      return this;
    }

    @Override
    @SuppressWarnings("unchecked")
    public Tests build() {
      try {
        Tests record = new Tests();
        record.first_name = fieldSetFlags()[0] ? this.first_name : (java.lang.String) defaultValue(fields()[0]);
        return record;
      } catch (org.apache.avro.AvroMissingFieldException e) {
        throw e;
      } catch (java.lang.Exception e) {
        throw new org.apache.avro.AvroRuntimeException(e);
      }
    }
  }

  @SuppressWarnings("unchecked")
  private static final org.apache.avro.io.DatumWriter<Tests>
    WRITER$ = (org.apache.avro.io.DatumWriter<Tests>)MODEL$.createDatumWriter(SCHEMA$);

  @Override public void writeExternal(java.io.ObjectOutput out)
    throws java.io.IOException {
    WRITER$.write(this, SpecificData.getEncoder(out));
  }

  @SuppressWarnings("unchecked")
  private static final org.apache.avro.io.DatumReader<Tests>
    READER$ = (org.apache.avro.io.DatumReader<Tests>)MODEL$.createDatumReader(SCHEMA$);

  @Override public void readExternal(java.io.ObjectInput in)
    throws java.io.IOException {
    READER$.read(this, SpecificData.getDecoder(in));
  }

  @Override protected boolean hasCustomCoders() { return true; }

  @Override public void customEncode(org.apache.avro.io.Encoder out)
    throws java.io.IOException
  {
    out.writeString(this.first_name);

  }

  @Override public void customDecode(org.apache.avro.io.ResolvingDecoder in)
    throws java.io.IOException
  {
    org.apache.avro.Schema.Field[] fieldOrder = in.readFieldOrderIfDiff();
    if (fieldOrder == null) {
      this.first_name = in.readString();

    } else {
      for (int i = 0; i < 1; i++) {
        switch (fieldOrder[i].pos()) {
        case 0:
          this.first_name = in.readString();
          break;

        default:
          throw new java.io.IOException("Corrupt ResolvingDecoder.");
        }
      }
    }
  }
}

我不相信可以通過 Java 代碼設置別名。