如何使用 Flux 将 Json Pojo 写入 CSV

Question

以下函数将检索字符串列表。在合并过程中，而不是打印输出，我想将输出写入 CSV 文件。

List<Mono<Device>> list1 = page.get().map(device -> webClient.post()
                .uri(uri)
                .header(HttpHeaders.CONTENT_TYPE, MediaType.APPLICATION_JSON_VALUE)
                .header(HttpHeaders.ACCEPT, MediaType.APPLICATION_JSON_VALUE)
                .body(Mono.just("{ \"mac\": \"" + device.getData()  ), String.class)
                .attributes(ServerOAuth2AuthorizedClientExchangeFilterFunction.clientRegistrationId("xxxx"))
                .retrieve()
                .bodyToMono(Device.class)).collect(Collectors.toList());

        Flux<Device> mergedMonos = Flux.fromIterable(list1).flatMapSequential(Function.identity());
        mergedMonos.doOnNext(System.out::println)
                .subscribe();


public class Device {
 @JsonProperty("ip")
 private String ip;
 @JsonProperty("macAddress")
 private String macAddress;
 @JsonProperty("vendor")
 private String vendor;

如何将设备 (Json) 数据写入 CSV 文件？

谢谢

Answer 1

结帐Converting JSON to CSV in Java

您可以利用 jackson 库将 java 对象转换为 csv。在依赖项中添加：

<dependency>
    <groupId>com.fasterxml.jackson.dataformat</groupId>
    <artifactId>jackson-dataformat-csv</artifactId>
    <version>2.11.1</version>
</dependency>
<dependency>
    <groupId>com.fasterxml.jackson.core</groupId>
    <artifactId>jackson-databind</artifactId>
    <version>2.11.1</version>
</dependency>

然后在代码中：

ObjectMapper mapper = new ObjectMapper();
Flux<Device> mergedMonos = 
Flux.fromIterable(list1).flatMapSequential(Function.identity());
List<JsonNode> nodes = mergedMonos
    .collectList()
    .map(mapper::valueToTree)
    .subscribe(list -> {
        Builder csvSchemaBuilder = CsvSchema.builder();
        JsonNode firstObject = list.elements().next();
        firstObject.fieldNames().forEachRemaining(fieldName -> {csvSchemaBuilder.addColumn(fieldName);} );
        CsvSchema csvSchema = csvSchemaBuilder.build().withHeader();
        CsvMapper csvMapper = new CsvMapper();
        csvMapper.writerFor(JsonNode.class)
          .with(csvSchema)
          .writeValue(new File("output.csv"), list);
    });