Flink如何使用-FasterXML/jackson数据格式文本-将CSV转换为POJO

Question

我在课堂上收到了一个CSV，我需要获取用于装箱POJO的值。我不必在目录中打开“file.csv”，由Flink将逗号分隔的元素传递给EventDeserializationSchema，这个元素用于“Event Class”来处理每个事件。

以下是一个示例：

在：“‘亚当’、‘史密斯’，66，….‘12:01:00.000’”-

为此，我正在使用：https://github.com/FasterXML/jackson-dataformats-text/tree/master/csv

这是我的事件类，应该做到这一点，实际上目前什么都没有做。

import java.io.Serializable;
import org.apache.flink.shaded.jackson2.com.fasterxml.jackson.databind.ObjectMapper;
import org.apache.flink.shaded.jackson2.com.fasterxml.jackson.databind.ObjectReader;
import org.apache.flink.shaded.jackson2.com.fasterxml.jackson.dataformat.csv.CsvMapper;
import org.apache.flink.shaded.jackson2.com.fasterxml.jackson.dataformat.csv.CsvSchema;

public class Event implements Serializable {

    CsvSchema schema = CsvSchema.builder()
            .addColumn("firstName")
            .addColumn("lastName")
            .addColumn("age", CsvSchema.ColumnType.NUMBER)
            .addColumn("time")
            .build();
    
    CsvSchema schema = CsvSchema.emptySchema().withHeader();

    CsvSchema bootstrapSchema = CsvSchema.emptySchema().withHeader();
    ObjectMapper mapper = new CsvMapper();
    mapper.readerFor(Pojo.class).with(bootstrapSchema).readValue(??);
    
    return Pojo
}

这是我的Pojo课程：

public class Pojo {
    
        public String firstName;
        public String lastName;
        private int age;
        public String time;

        public Pojo(String firstName, String lastName, int age, String time) {
            this.firstName = firstName;
            this.lastName = lastName;
            this.age = age;
            this.time =time;
            
        }

}

如果能帮助全班同学归还Pojo，我们将不胜感激。

这是JSON：https://github.com/apache/flink-playgrounds/blob/master/docker/ops-playground-image/java/flink-playground-clickcountjob/src/main/java/org/apache/flink/playgrounds/ops/clickcount/records/ClickEventDeserializationSchema.java的一个例子

单击evenclasshttps://html" target="_blank">github.com/apache/flink/blob/9dd04a25bd300a725486ff08560920f548f3b1d9/flink-end-to-end-tests/flink-streaming-kafka-test-base/src/main/java/org/apache/flink/streaming/kafka/test/base/KafkaEvent.java#L27

Answer 1

要使其工作，您需要为字段设置默认构造函数和getter/setters。我不明白您将在Event中做什么，以及为什么还有Pojo，但假设您想将传入的字符串反序列化为Event，这样的东西应该可以工作：

1. 事件Pojo类：

public class Event implements Serializable {
    public String firstName;
    public String lastName;
    private int age;
    public String time;

    public Event() {
    }

    public String getFirstName() {
        return firstName;
    }

    public void setFirstName(String firstName) {
        this.firstName = firstName;
    }

    public String getLastName() {
        return lastName;
    }

    public void setLastName(String lastName) {
        this.lastName = lastName;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public String getTime() {
        return time;
    }

    public void setTime(String time) {
        this.time = time;
    }
}

public class EventDeserializationSchema implements DeserializationSchema<Event> {

    private static final long serialVersionUID = 1L;

    private static final CsvSchema schema = CsvSchema.builder()
            .addColumn("firstName")
            .addColumn("lastName")
            .addColumn("age", CsvSchema.ColumnType.NUMBER)
            .addColumn("time")
            .build();

    private static final ObjectMapper mapper = new CsvMapper();

    @Override
    public Event deserialize(byte[] message) throws IOException {
        return mapper.readerFor(Event.class).with(schema).readValue(message);
    }

    @Override
    public boolean isEndOfStream(Event nextElement) {
        return false;
    }

    @Override
    public TypeInformation<Event> getProducedType() {
        return TypeInformation.of(Event.class);
    }
}