无法生成AVRO到CSV,无法找出错误的根源
pom.xml-
<jackson.version>2.12.4</jackson.version>
<dependency>
<groupId>com.fasterxml.jackson.datatype</groupId>
<artifactId>jackson-datatype-hppc</artifactId>
<version>${jackson.version}</version>
</dependency>
<dependency>
<groupId>com.fasterxml.jackson.datatype</groupId>
<artifactId>jackson-datatype-json-org</artifactId>
<version>${jackson.version}</version>
</dependency>
<dependency>
<groupId>com.fasterxml.jackson.datatype</groupId>
<artifactId>jackson-datatype-jsr310</artifactId>
</dependency>
<dependency>
<groupId>com.fasterxml.jackson.dataformat</groupId>
<artifactId>jackson-dataformat-csv</artifactId>
<version>${jackson.version}</version>
<type>jar</type>
</dependency>
模型-
package com.test.employee.model;
import java.time.ZonedDateTime;
import com.fasterxml.jackson.annotation.JsonIgnore;
import com.fasterxml.jackson.annotation.JsonProperty;
import com.fasterxml.jackson.annotation.JsonPropertyOrder;
@JsonPropertyOrder({"id", "name", "modifiedTimestamp", "score"})
public class EmployeeModel {
@JsonProperty("id")
private String id;
@JsonProperty("name")
private String name;
@JsonProperty("modifiedTimestamp")
private ZonedDateTime modifiedTimestamp;
@JsonProperty("score")
private String score;
@JsonIgnore
private String employeeId;
public EmployeeModel(String id, String name, ZonedDateTime modifiedTimestamp,
@JsonProperty("score"), String score) {
this.id = id;
this.name = name;
this.modifiedTimestamp = modifiedTimestamp;
this.score = score;
}
public String getId() {
return id;
}
public String getName() {
return name;
}
public ZonedDateTime getModifiedTimestamp() {
return modifiedTimestamp;
}
public String getScore() {
return score;
}
public String getEmployeeId() {
return employeeId;
}
}
public class Test {
private File avroToCsv(File avroFile, String path) {
File result = new File(path);
if (result.exists()) result.delete();
try {
GenericDatumReader<GenericData.Record> datum = new GenericDatumReader<>();
DataFileReader<GenericData.Record> reader = new DataFileReader<>(avroFile, datum);
GenericData.Record record = new GenericData.Record(reader.getSchema());
CsvMapper csvMapper = new CsvMapper();
CsvSchema schema = csvMapper.schemaFor(EmployeeModel.class).withHeader();
OutputStream outStream = new FileOutputStream(result , true);
CsvGenerator csvGenerator = csvMapper.getFactory().createGenerator(outStream);
ObjectWriter csvWriter = csvMapper.writer(schema);
while (reader.hasNext()) {
reader.next(record);
LocalDateTime dateTime = LocalDateTime.parse(modifDate);
ZonedDateTime modifiedDate = ZonedDateTime.of(dateTime, ZoneId.systemDefault());
EmployeeModel tempModel = new EmployeeModel(
record.get("id").toString(),
record.get("name").toString(),
modifiedDate,
record.get("score").toString()
);
csvWriter.writeValue(csvGenerator, tempModel);
}
}catch (Exception e) {
e.printStackTrace();
}
}
public static void main(String []args) {
avroToCsv(new File("abc.avro"), "c:/test/ModifiedUsers.csv");
}
}
模式对象包含标题如下:"id“、"name”、"modifiedTimestamp“、"score”Employee模型包含的值为:"123456“、"demoapp”、2021-04-16T19:00:54、"2.4“。
收到的例外情况: //
com.fasterxml.jackson.databind.JsonMappingException: [no message for java.lang.NullPointerException]
at com.fasterxml.jackson.databind.ser.DefaultSerializerProvider._wrapAsIOE(DefaultSerializerProvider.java:509)
at com.fasterxml.jackson.databind.ser.DefaultSerializerProvider._serialize(DefaultSerializerProvider.java:482)
at com.fasterxml.jackson.databind.ser.DefaultSerializerProvider.serializeValue(DefaultSerializerProvider.java:319)
at com.fasterxml.jackson.databind.ObjectWriter$Prefetch.serialize(ObjectWriter.java:1396)
at com.fasterxml.jackson.databind.ObjectWriter._configAndWriteValue(ObjectWriter.java:1120)
at com.fasterxml.jackson.databind.ObjectWriter.writeValue(ObjectWriter.java:933)
at com.test.employee.Test.avroToCsv(AvroToCsv.java:164)
at com.test.employee.Test.main(Test.java:41)
Caused by: java.lang.NullPointerException
at com.fasterxml.jackson.core.base.GeneratorBase.setCurrentValue(GeneratorBase.java:138)
at com.fasterxml.jackson.core.base.GeneratorBase.writeStartObject(GeneratorBase.java:290)
at com.fasterxml.jackson.databind.ser.BeanSerializer.serialize(BeanSerializer.java:151)
at com.fasterxml.jackson.databind.ser.DefaultSerializerProvider._serialize(DefaultSerializerProvider.java:480)
... 7 more
// com.fasterxml.jackson.core.JsonGenerationException:无法启动对象,期待字段名在com.fasterxml.jackson.core.JsonGenerator._reportError(JsonGenerator.java:1961),com.fasterxml.jackson.dataformat.csv.CsvGenerator._verifyValueWrite(CsvGenerator.java:957),com.fasterxml.jackson.dataformat.csv.CsvGenerator.writeStartObject(CsvGenerator.java:584),com.fasterxml.jackson.core.base.GeneratorBase.writeStartObject(GeneratorBase.java:286),com.fasterxml.jackson.databind.ser.BeanSerializer.serialize(BeanSerializer.java:151),com.fasterxml.jackson.databind.ser.DefaultSerializerProvider._serialize(DefaultSerializerProvider.java:480) at com.fasterxml.jackson.databind.ser.DefaultSerializerProvider.serializeValue(DefaultSerializerProvider.java:319) at com.fasterxml.jackson.databind.ObjectWriter$Prefetch.serialize(ObjectWriter.java:1396) at com.fasterxml.jackson.databind.ObjectWriter.writeValue(ObjectWriter.java:913)
Issue Identified with library:
https://github.com/FasterXML/jackson-dataformats-text/issues/114
发布于 2021-08-30 22:24:55
这里的问题不是模式,也不是缺乏模式(某种程度),而是您正在为每个值构建新的ObjectWriter
实例:这是行不通的。
相反,如果要单独编写行序列,则需要构造一个SequenceWriter
。类似于:
ObjectWriter ow = mapper.writerFor(schema);
SequenceWriter sw = ow.writeValues(outStream);
然后使用
sw.write(tempModel);
https://stackoverflow.com/questions/68949432
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