java - 如何修复流关闭异常

Question

我正在开发一个可以将列表写入 json 文件的小程序，因此我创建了两个 Dealer 类实例，然后将其添加到“dealerList”。

我尝试写入名为“Dealer.json”的 json 文件，因此我从名为“dealerList”的列表中读取对象，然后将其写入 json 文件。

public class Main {
    private static List<Dealer> dealerList = new ArrayList<>();

    public static void main(String[] args) {
            Dealer dearler = new Dealer("Chevrolet");
            dearler.addCartoDealer(new Cars("Camaro","Steve",11000));
            dearler.addCartoDealer(new Cars("Coverette","Jhon",22000));
            Dealer dearler1 = new Dealer("Ford");
            dearler1.addCartoDealer(new Cars("Ford1","Jessie",11000));
            dearler1.addCartoDealer(new Cars("Ford2","Smith",22000));
            dealerList.add(dearler);
            dealerList.add(dearler1);
            ObjectMapper mapper = new ObjectMapper();

            try(FileOutputStream newFile = new FileOutputStream("Dealer.json")){
               for(Dealer dealer:dealerList){
                  mapper.writeValue(newFile,dealer);
               }
            } catch (IOException e){
              e.printStackTrace();
            }
    }

我得到的堆栈:

java.io.IOException: Stream Closed
    at java.io.FileOutputStream.writeBytes(Native Method)
    at java.io.FileOutputStream.write(FileOutputStream.java:326)
    at com.fasterxml.jackson.core.json.UTF8JsonGenerator._flushBuffer(UTF8JsonGenerator.java:2093)
    at com.fasterxml.jackson.core.json.UTF8JsonGenerator.close(UTF8JsonGenerator.java:1137)
    at com.fasterxml.jackson.databind.ObjectMapper._configAndWriteValue(ObjectMapper.java:3983)
    at com.fasterxml.jackson.databind.ObjectMapper.writeValue(ObjectMapper.java:3245)
    at com.Ayoub.Main.main(Main.java:26)

我得到了 Stream 关​​闭异常

Answer 1

我认为 Jackson 会在调用 writeValue 后自动关闭您的流。您可以通过以下方式关闭此功能:

MessagePackFactory messagePackFactory = new MessagePackFactory();
messagePackFactory.disable(JsonGenerator.Feature.AUTO_CLOSE_TARGET);
ObjectMapper objectMapper = new ObjectMapper(messagePackFactory);

不要忘记在某个时间点自己关闭流 ;-)