java - 附加到 ObjectOuputStream

Question

这个问题已经有答案了:

FileOutputStream opens a new file and deletes the contents whenever it is created (2 个回答)

已关闭 5 年前。

我有一个名为“admin_product.bin”的文件。我想将对象附加到文件中。搜索后发现一个类如下:

public class AppendingObjectOutputStream extends ObjectOutputStream {

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

  @Override
  protected void writeStreamHeader() throws IOException {
    // do not write a header, but reset:
    // this line added after another question
    // showed a problem with the original
    reset();
  }

}

上面的代码帮助我们将数据附加到我的文件中。但是，当我尝试使用 ObjectInputStream 读取文件时，它会抛出如下错误:

java.io.StreamCorruptedException: invalid stream header: 79737200

我的代码示例是:

public static void write_into_file() throws IOException {
        File file = null;
        file = new File("admin_product.bin");

        if(!file.exists()) {
            ObjectOutputStream os = null;
            try {
                os = new ObjectOutputStream(new FileOutputStream(file));
                os.writeObject(prd);
                System.out.println("Done!");
            } catch(Exception e) {
                System.out.println("Exception = " + e);
            } finally {
                if(os != null) {
                    os.close();
                }
            }

        }

        else {
            AppendingObjectOutputStream as = null;
            try {
                as = new AppendingObjectOutputStream(new FileOutputStream(file));
                as.writeObject(prd);
                System.out.println("Done!");
            } catch(Exception e) {
                System.out.println("Exception = " + e);
            } finally {
                if(as != null) {
                    as.close();
                }
            }
        }
    }

谁能告诉我哪里出错了？

我有以下问题的答案(但无法找出问题所在)-

1) Appending to a file

2) Appending class error

Answer 1

您没有附加到文件。如果要附加到对象流，则还必须附加到文件，并且不能覆盖已有的内容。

这将覆盖现有文件内容:

new FileOutputStream(file)

附加使用

new FileOutputStream(file, true)

整行是:

as = new AppendingObjectOutputStream(new FileOutputStream(file, true));