Jackson CSV映射器不适用于自定义架构 [英] Jackson CSV mapper doesn't work for custom schema

问题描述

我有此代码:

CsvSchema sema = CsvSchema.builder()
    .addColumn("name")
    .addColumn("year", CsvSchema.ColumnType.NUMBER)
    .build().withHeader();

ObjectReader reader = new CsvMapper().readerFor(JsonNode.class).with(sema);

JsonNode o = reader.readValue(new FileInputStream(new File("/path/to/test.csv")));
System.out.println(o);

和test.csv是:

test, year
1,    1

该代码应以以下格式将CSV解析为JSON:

That code should parse CSV to JSON in next format:

{"name":"1","year":1}

但是我的输出是:

{"name":"1","year":"1"}

问题是:Jackson将年份解析为String，但是我在CSV Schema中配置的年份是Number.有人知道这是什么问题吗?

Problem is: Jackson parses year as String, but I configured in CSV Schema that year is Number. Does someone know what is the problem?

Jackson版本是2.9.8，我也在2.7.1

Jackson version is 2.9.8, I tried it also on 2.7.1

推荐答案

下班后，我为您找到了解决方案.

After hours of work I found a solution for you.

我使用FlexJson来配置json的序列化.

I used FlexJson to configure the serialization of your json.

    <!-- https://mvnrepository.com/artifact/net.sf.flexjson/flexjson -->
<dependency>
    <groupId>net.sf.flexjson</groupId>
    <artifactId>flexjson</artifactId>
    <version>2.0</version>
</dependency>

它不是很漂亮，但是可以.

It is not very pretty but it works.

希望这对您有所帮助，并且我相信您可以改进此代码

I hope this helps you and I am sure you can improve this code

public String generateJsonFromCSV(File csvFile, File schemaJson) throws IOException, ClassNotFoundException, NoSuchMethodException, IllegalAccessException, InvocationTargetException, InstantiationException {

    //Get CsvSchema as Map
    Map<String, CsvSchema.ColumnType> map = getSchemaMapFromJson(schemaJson);
    //Create CsvSchema from CsvSchemaMap
    CsvSchema.Builder schemaBuilder = new CsvSchema.Builder();
    map.forEach(schemaBuilder::addColumn);
    CsvSchema schema = schemaBuilder.build();
    //read CSV
    CsvMapper csvMapper = new CsvMapper();
    MappingIterator<Map<?, ?>> mappingIterator = csvMapper.readerFor(Map.class).with(schema).readValues(csvFile);
    //Get configured JsonSerializer from CsvSchemaMap
    JSONSerializer jsonSerializer = getJsonSerializer(map);
    List<Map<?, ?>> lines = mappingIterator.readAll();
    //remove first line
    lines.remove(0);
    //serialize
    return jsonSerializer.deepSerialize(lines);
}

/**
 *
 * @param schemaMap mapping field to ColumnType
 * @return a configured JSONSerializer
 */
private JSONSerializer getJsonSerializer(Map<String, CsvSchema.ColumnType> schemaMap){
    Map<CsvSchema.ColumnType, Transformer> transformerMap = new EnumMap<>(CsvSchema.ColumnType.class);
    transformerMap.put(CsvSchema.ColumnType.STRING, new StringTransformer());
    transformerMap.put(CsvSchema.ColumnType.NUMBER, new NumberTransformer());
    JSONSerializer jsonSerializer = new JSONSerializer();
    for (Map.Entry<String, CsvSchema.ColumnType> columnTypeEntry : schemaMap.entrySet()) {
        jsonSerializer.transform(transformerMap.get(columnTypeEntry.getValue()),columnTypeEntry.getKey());
    }
    return jsonSerializer;
}

/**
 /**
 *
 * @param file JSON CsvSchema
 * @return fieldname ColumnType mapping
 * @throws ClassNotFoundException
 */
private Map<String, CsvSchema.ColumnType> getSchemaMapFromJson(File file) throws ClassNotFoundException {
    Map<String, String> schema = new JSONDeserializer<Map<String,String>>().deserialize(getResourceFileAsString(file.getName()));
    Map<String, CsvSchema.ColumnType> result = new HashMap<>(schema.size());
    for (Map.Entry<String, String> columnSchema : schema.entrySet()) {
        result.put(columnSchema.getKey(), CsvSchema.ColumnType.valueOf(columnSchema.getValue().toUpperCase()));
    }
    return result;
}

输出将是

[{"name":"foobar","year":1986},{"name":"testtest","year":777}]

这篇关于Jackson CSV映射器不适用于自定义架构的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！