具有另一个对象列表的对象的 DynamoDB Mapper 注释

Question

我正在尝试为以下情况创建一个 dynamoDBMapper 注释。

我有 EmployeeLevelTrail，它是一个员工级别记录的类

@DynamoDBTable(tableName = TABLE_NAME)
public class EmployeeData {
    public final static String TABLE_NAME = “EmployeeDataRecord”;

    @DynamoDBAttribute(attributeName = “employeeID”)
    public String EmployeeID;

    @DynamoDBAttribute(attributeName = “EmployeeLevelDataRecords”)
    @DynamoDBTyped(DynamoDBMapperFieldModel.DynamoDBAttributeType.M)
    public EmployeeLevelTrail employeeLevelTrail

}


public class EmployeeLevelTrail {

    public final static String DDB_ATTR_EMPLOYEE_LEVEL_TRAIL = “employeeLevelTrail”;

    @DynamoDBAttribute(attributeName = DDB_ATTR_EMPLOYEE_LEVEL_TRAIL)
    private List<EmployeeLevelRecord> thisEmployeeLevelRecords;

    public void appendEmployeeLevelRecord(@NonNull EmployeeLevelRecord employeeLevelRecord) {

        thisEmployeeLevelRecords.add(employeeLevelRecord);

    }
}


public class EmployeeLevelRecord {

    private String Level;

    private String Manager;

    private Instant timeOfEvent;

}

这是我的注释，但它不正确，因为我无法保存我的 DynamoDB 数据

Answer 1

要将另一个类标记为 DynamoDBMapper 的数据模型的一部分，您可以使用 注释它@DynamoDBDocument，它告诉 DynamoDBMapper 一个类可以序列化为 DynamoDB 文档。

对于类，你是不是写（即从Java库或外部库）或者如果你需要更多的控制权如何序列化自己的类之一，就可以使用@DynamoDBTypeConverted，它允许你映射任意数据提供您的自己的DynamoDBTypeConverter实现来从任何 Java 对象转换为任何受支持的 DynamoDB 类型。

使用您的示例代码，我添加了适当的@DynamoDBDocumentand@DynamoDBTypeConverted注释，以及DynamoDBTypeConverter将 an 转换Instant为 ISO-8601 的a 示例实现String。如果employeeId是表的哈希键，请确保还将@DynamoDBHashKey注释添加到employeeId.

@DynamoDBTable(tableName = TABLE_NAME)
public class EmployeeData {
    public final static String TABLE_NAME = “EmployeeDataRecord”;

    @DynamoDBAttribute(attributeName = “employeeID”)
    public String EmployeeID;

    @DynamoDBAttribute(attributeName = “EmployeeLevelDataRecords”)
    public EmployeeLevelTrail employeeLevelTrail

}

@DynamoDBDocument
public class EmployeeLevelTrail {

    public final static String DDB_ATTR_EMPLOYEE_LEVEL_TRAIL = “employeeLevelTrail”;

    @DynamoDBAttribute(attributeName = DDB_ATTR_EMPLOYEE_LEVEL_TRAIL)
    private List<EmployeeLevelRecord> thisEmployeeLevelRecords;

    public void appendEmployeeLevelRecord(@NonNull EmployeeLevelRecord employeeLevelRecord) {

        thisEmployeeLevelRecords.add(employeeLevelRecord);

    }
}

@DynamoDBDocument
public class EmployeeLevelRecord {

    private String Level;

    private String Manager;

    @DynamoDBTypeConverted(converter = InstantToStringTypeConverter.class)
    private Instant timeOfEvent;

}

public class InstantToStringTypeConverter implements DynamoDBTypeConverter<String, Instant> {

    @Override
    public String convert(final Instant instant) {
        return instant.toString();
    }

    @Override
    public Instant unconvert(final String string) {
        return Instant.parse(string);
    }
}

Answer 2

我使用下面的代码找到了解决方案。仅使用 @DynamoDBTypeConvertedJSON，我能够在表中创建一个条目，但无法更新它，因为我遇到了映射 Dynamo DB 映射异常。

@Data
@Builder
@AllArgsConstructor
@NoArgsConstructor
@DynamoDBTable(tableName = TABLE_NAME)
public class EmployeeData {

    public final static String TABLE_NAME = "EmployeeData";

    public final static String DDB_ATTR_ID = "Id";

    public final static String DDB_ATTR_EMPLOYEE_LEVEL_RECORD_TRAIL = "EmployeeLevelRecordTrail";

    @DynamoDBHashKey(attributeName = DDB_ATTR_ID)
    @DynamoDBAttribute(attributeName = DDB_ATTR_ID)
    private String id;

    @DynamoDBAttribute(attributeName = DDB_ATTR_EMPLOYEE_LEVEL_RECORD_TRAIL)
    @DynamoDBTypeConverted(converter = EmployeeLevelRecordTrailConverter.class)
    private  EmployeeLevelRecordTrail  employeeLevelRecordTrail;

    @DynamoDBAttribute(attributeName = DDB_ATTR_CREATED_TIME)
    @DynamoDBTypeConverted(converter = InstantConverter.class)
    private Instant joiningTime;
}



@Data
@Builder
@AllArgsConstructor
@NoArgsConstructor
public class EmployeeLevelRecordTrail {

    private List<EmployeeLevelRecord> thisEmployeeLevelRecords;

    public void appendEmployeeLevelRecord(@NonNull EmployeeLevelRecord employeeLevelRecord) {

        thisEmployeeLevelRecords.add(employeeLevelRecord);

    }
}


@Data
@Builder
@AllArgsConstructor
@NoArgsConstructor
@DynamoDBDocument
public class EmployeeLevelRecord {

    private String Level;

    private String Manager;

    @DynamoDBTypeConverted(converter = InstantConverter.class)
    private Instant timeOfEvent;

}

public class EmployeeLevelRecordTrailConverter implements
        DynamoDBTypeConverter<List<EmployeeLevelRecord>, EmployeeLevelRecordTrail> {

    @Override
    public List<EmployeeLevelRecord> convert(EmployeeLevelRecordTrail employeeLevelRecordTrail) {
        return employeeLevelRecordTrail.getEmployeeLevelRecord();
    }

    @Override
    public EmployeeLevelRecordTrail unconvert(List<EmployeeLevelRecord> thisEmployeeLevelRecords) {
        return new EmployeeLevelRecordTrail(thisEmployeeLevelRecords);
    }
}

public class InstantConverter implements DynamoDBTypeConverter<String, Instant> {

    private static final DateTimeFormatter DATE_TIME_FORMATTER = DateTimeFormatter.ISO_INSTANT;

    @Override
    public String convert(Instant instant) {
        return instant == null ? null : DATE_TIME_FORMATTER.format(instant);
    }

    @Override
    public Instant unconvert(String str) {
        return str == null ? null : Instant.from(DATE_TIME_FORMATTER.parse(str));
    }
}

阅读有关如何进行映射的文档会有所帮助。