Question

import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.io.OutputStream;

public class Main
{
    static ObjectOutputStream outputStream;
    static ObjectInputStream inputStream;

    public static void main(String[] args) throws Exception
    {
        File file = new File("Test.ser");
        outputStream = openWriteFile(file);
        write(new Integer(5));
        write(new Integer(3));
        write(new Integer(1));

        FileInputStream fileInputStream = new FileInputStream(file);
        inputStream = openReadFile(fileInputStream);
        readFile();
    }

    public static ObjectOutputStream openWriteFile(File file)
    {
        try
        {
            if (file.exists())
                return new AppendableObjectOutputStream(new FileOutputStream(file, true));

            return new ObjectOutputStream(new FileOutputStream(file));
        }

        catch (IOException e)
        {
            return null;
        }
    }

    public static void write(Integer i)
    {
        try
        {
            outputStream.write(i); 
        }

        catch (IOException ioException)
        {
            System.err.println("error");
        }
    }

    public static ObjectInputStream openReadFile(FileInputStream fileInputStream)
    {
        try
        {
            if(fileInputStream.getChannel().position() != 0)
                return new ObjectInputStream(fileInputStream);
            return new AppendableObjectInputStream(fileInputStream);
        }

        catch (IOException ioException)
        {
            return null;
        }
    }

    public static void readFile()
    {
        try
        {
            while (true)
            {
                System.out.println("here");
                Integer integer = (Integer) inputStream.readObject();
                System.out.println("after");
                System.out.println(integer);
            }
        }

        catch (ClassNotFoundException classNotFoundException)
        {
            classNotFoundException.printStackTrace();
        }

        catch (IOException e) 
        {
            System.err.println("ioexecption");
            e.printStackTrace();
        }
    }


    private static class AppendableObjectOutputStream extends ObjectOutputStream
    {

        public AppendableObjectOutputStream(OutputStream out) throws IOException
        {
            super(out);
        }

        @Override
        protected void writeStreamHeader() throws IOException
        {
            // do not write a header
        }
    }

    private static class AppendableObjectInputStream extends ObjectInputStream
    {

        public AppendableObjectInputStream(InputStream in) throws IOException
        {
            super(in);
        }

        @Override
        protected void readStreamHeader() throws IOException
        {
            // do not read a header
        }
    }
}

输出：

here
ioexecption
java.io.StreamCorruptedException: invalid type code: AC
    at java.io.ObjectInputStream.readObject0(Unknown Source)
    at java.io.ObjectInputStream.readObject(Unknown Source)
    at Main.readFile(Main.java:79)
    at Main.main(Main.java:25)

从我写的.ser文件中读回来时遇到了一些麻烦。我已经运行了几次程序并使用了getClass()，发现两个流都是流的Appendable版本。消息“here”打印到控制台但不打印在“之后”。 “Test.ser”出现在与classpath相同的目录中，并包含内容“¬í”。

Answer 1

在处理输入和输出时，您应该寻找对称性：如果您在一侧写入一个字节，则在另一侧读取一个字节。如果你在一边写一个对象，你可以在另一边读一个对象。

您的代码写入3个字节，并尝试读取对象。那不行。

我也不明白你想要用你的可追溯流来实现什么。

读取和附加到ObjectInputStream / ObjectOutputStream时遇到问题

1 个答案: