avro 架构 LocalDate 映射

Question

如何将 avro 架构映射到 LocalDate / LocaldateTime？ 规范说我们可以使用logicalType。但不关心显示它如何映射到 Java 中的 LocalDate 的示例。为什么一个很好的例子不是规范的一部分？那是给规范编写者的。 安耶 例如

    {"namespace": "example.avro",
     "type": "record",
     "name": "User",
     "fields": [
    {"name": "date", "type": "int", "logicalType": "date"}
    ]
    }

这映射到 int 而不是 LocalDate 例如，

如何在 avro 模式中映射 LocalDate？

    @org.apache.avro.specific.AvroGenerated   
    public class User extends org.apache.avro.specific.SpecificRecordBase implements      
org.apache.avro.specific.SpecificRecord {
    private int date;// This should be LocalDate
    }

Answer 1

{
  "namespace": "example.avro",
  "type": "record",
  "name": "User",
  "fields": [
    {
      "name": "date",
      "type": {
        "type": "int",
        "logicalType": "date"
      }
    }
  ]
}

//这将生成以下到私有 java.time.LocalDate 日期的映射；如下所示，使用 maven-avro-plugin。

/** * 由 Avro 自动生成 * * 不要直接编辑 */ 包example.avro;

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 User extends org.apache.avro.specific.SpecificRecordBase implements org.apache.avro.specific.SpecificRecord {
  private static final long serialVersionUID = -2875816324033601436L;
  public static final org.apache.avro.Schema SCHEMA$ = new org.apache.avro.Schema.Parser().parse("{\"type\":\"record\",\"name\":\"User\",\"namespace\":\"example.avro\",\"fields\":[{\"name\":\"date\",\"type\":{\"type\":\"int\",\"logicalType\":\"date\"}}]}");
  public static org.apache.avro.Schema getClassSchema() { return SCHEMA$; }

  private static SpecificData MODEL$ = new SpecificData();
static {
    MODEL$.addLogicalTypeConversion(new org.apache.avro.data.TimeConversions.DateConversion());
  }

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

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

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

  /**
   * Return the BinaryMessageDecoder instance used by this class.
   * @return the message decoder used by this class
   */
  public static BinaryMessageDecoder<User> 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<User> createDecoder(SchemaStore resolver) {
    return new BinaryMessageDecoder<User>(MODEL$, SCHEMA$, resolver);
  }

  /**
   * Serializes this User 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 User from a ByteBuffer.
   * @param b a byte buffer holding serialized data for an instance of this class
   * @return a User 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 User fromByteBuffer(
      java.nio.ByteBuffer b) throws java.io.IOException {
    return DECODER.decode(b);
  }

   private java.time.LocalDate date;

  /**
   * 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 User() {}

  /**
   * All-args constructor.
   * @param date The new value for date
   */
  public User(java.time.LocalDate date) {
    this.date = date;
  }

  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 date;
    default: throw new IndexOutOfBoundsException("Invalid index: " + field$);
    }
  }

  private static final org.apache.avro.Conversion<?>[] conversions =
      new org.apache.avro.Conversion<?>[] {
      new org.apache.avro.data.TimeConversions.DateConversion(),
      null
  };

  @Override
  public org.apache.avro.Conversion<?> getConversion(int field) {
    return conversions[field];
  }

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

  /**
   * Gets the value of the 'date' field.
   * @return The value of the 'date' field.
   */
  public java.time.LocalDate getDate() {
    return date;
  }


  /**
   * Sets the value of the 'date' field.
   * @param value the value to set.
   */
  public void setDate(java.time.LocalDate value) {
    this.date = value;
  }

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

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

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

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

    private java.time.LocalDate date;

    /** 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(example.avro.User.Builder other) {
      super(other);
      if (isValidValue(fields()[0], other.date)) {
        this.date = data().deepCopy(fields()[0].schema(), other.date);
        fieldSetFlags()[0] = other.fieldSetFlags()[0];
      }
    }

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

    /**
      * Gets the value of the 'date' field.
      * @return The value.
      */
    public java.time.LocalDate getDate() {
      return date;
    }


    /**
      * Sets the value of the 'date' field.
      * @param value The value of 'date'.
      * @return This builder.
      */
    public example.avro.User.Builder setDate(java.time.LocalDate value) {
      validate(fields()[0], value);
      this.date = value;
      fieldSetFlags()[0] = true;
      return this;
    }

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


    /**
      * Clears the value of the 'date' field.
      * @return This builder.
      */
    public example.avro.User.Builder clearDate() {
      fieldSetFlags()[0] = false;
      return this;
    }

    @Override
    @SuppressWarnings("unchecked")
    public User build() {
      try {
        User record = new User();
        record.date = fieldSetFlags()[0] ? this.date : (java.time.LocalDate) 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<User>
    WRITER$ = (org.apache.avro.io.DatumWriter<User>)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<User>
    READER$ = (org.apache.avro.io.DatumReader<User>)MODEL$.createDatumReader(SCHEMA$);

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

}