无法从 InputStream 中读取多个可外部化对象 [重复]

Question

我在从 InputStream（即从文件）读取多个对象时遇到问题。我收到异常：

java.io.StreamCorruptedException: invalid type code: AC
    at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1379)
    at java.io.ObjectInputStream.readObject(ObjectInputStream.java:371)
    at com.socket.Client.readFromFile(Client.java:63)
    at com.socket.Client.main(Client.java:44)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:483)
    at com.intellij.rt.execution.application.AppMain.main(AppMain.java:120)

我只成功地读/写了一个对象，没关系。我可以写很多对象，也可以。但我不能从文件中读取多个对象。为什么会这样？

编辑：

注意！看来我遇到了在 Externalazible 类中实现 List 的问题。如何正确实现？

我的“主要”代码：

public class Client {


public static void main(String[] args) {

    if (args[0] == null || args[1] == null) {
        System.out.println("No arguments entered!");
        System.exit(0);
    }

    try (Socket clientSocket = new Socket("localhost", 3000);
         OutputStream outbound = clientSocket.getOutputStream();
         BufferedReader inbound = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));) {

        outbound.write((args[0] + "\n").getBytes());
        outbound.write("End\n".getBytes());

        List<StockQuote> stockQuotes = new ArrayList<>();
        String quote;
        while (true) {
            quote = inbound.readLine();

            if (quote != null && quote.equals("End"))
                break;

            stockQuotes.add(new StockQuote(args[0], new Double(quote)));
        }

        writeInFile(args[1], stockQuotes);
        stockQuotes.clear();

        stockQuotes = readFromFile(args[1]);
        if (stockQuotes != null)
            for (StockQuote stockQuote : stockQuotes)
                System.out.println("The " + stockQuote.getSymbol() + " price is " + stockQuote.getPrice());

    } catch (UnknownHostException e) {
        System.out.println("No such host available!");
    } catch (IOException e) {
        System.out.println("Server not reachable or down!!");
    }
}

private static List<StockQuote> readFromFile(String filename) {

    File file = new File(filename);

    try (ObjectInputStream readFromFile = new ObjectInputStream(new BufferedInputStream(new FileInputStream(file)));) {
        return (List<StockQuote>) readFromFile.readObject();
    } catch (FileNotFoundException e) {
        System.out.println("'" + filename + "' is not found in " + file.getPath());
    } catch (IOException e) {
        e.printStackTrace();
        System.out.println("Something gone wrong in the process of reading from '" + file + "'");
    } catch (ClassNotFoundException e) {
        System.out.println("Cast to class is wrong!");
    }

    return null;
}

private static void writeInFile(String filename, List<StockQuote> stockQuotes) {

    File file = new File(filename);

    try (ObjectOutputStream writeInFile = new ObjectOutputStream(new BufferedOutputStream(new FileOutputStream(file, true)));) {
            writeInFile.writeObject(stockQuotes);
    } catch (FileNotFoundException e) {
        System.out.println("'" + filename + "' is not found in " + file.getPath());
    } catch (IOException e) {
        System.out.println("Something gone wrong in the process of writing to '" + file + "'");
    }
}

}

可外部化的“StockQuote”类：

public class StockQuote implements Externalizable {

private String symbol;
private double price;
private List<StockQuote> stockQuoteList;

public StockQuote() {
}

public StockQuote(String symbol, double price) {
    this.symbol = symbol;
    this.price = price;
}

public String getSymbol() {
    return symbol;
}

public void setSymbol(String symbol) {
    this.symbol = symbol;
}

public double getPrice() {
    return price;
}

public void setPrice(double price) {
    this.price = price;
}

@Override
public void writeExternal(ObjectOutput out) throws IOException {
    out.writeObject(stockQuoteList);
}

@Override
public void readExternal(ObjectInput in) throws IOException, ClassNotFoundException {
    stockQuoteList = (List<StockQuote>) in.readObject();
}

}

结果：

结果，我收到类似“空价格为 0.0”的信息。它说我序列化了我的列表，但里面的对象没有序列化，为什么？

注意！

您能否再给我一个提示，如何在 Externalizable 类中将字符串、列表等写成 out.writeObject 或有更好的方法？

Answer 1

您的读取和写入不是对称的。

要写两个股票报价，你

• 打开一个新的 ObjectOutputStream
• 写股票报价
• 关闭 ObjectOutputStream
• 打开一个新的 ObjectOutputStream
• 写股票报价
• 关闭 ObjectOutputStream

要阅读这两个股票行情，您

• 打开一个 ObjectInputStream
• 阅读股票报价
• 阅读股票报价
• 关闭 ObjectInputStream

每次打开新的 ObjectOutputStream 时，都会将序列化标头写入底层流。

我的建议：将所有 StockQuotes 存储到一个列表中，并在完成后将此列表写入 ObjectOutputStream。在接收端，读取列表。