使用EOFException阅读objectInputStream

Question

我想要写对象文件并读取它们，但是我得到了错误。Main.java中的第51行是while循环，它应该显示对象。

Exception in thread "main" java.io.EOFException
    at java.io.ObjectInputStream$BlockDataInputStream.peekByte(ObjectInputStream.java:2626)
    at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1321)
    at java.io.ObjectInputStream.readObject(ObjectInputStream.java:373)
    at com.sdajava.rwobj.Main.main(Main.java:51)
    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:498)
    at com.intellij.rt.execution.application.AppMain.main(AppMain.java:147)

我的代码:首先编写对象并读取它们。数据被写入文件。

String fileName = "c://Users//lukas//obj.txt";
Person p1 = new Person("Jan", "Kowalski", 21);
Person p2 = new Person("Jan", "Kowalski", 21);

OutputStream  fileOutputStream = null;
ObjectOutput objectOutputStream = null;
OutputStream bufferOut  = null;
try {

    fileOutputStream = new FileOutputStream(fileName);
    bufferOut = new BufferedOutputStream(fileOutputStream);
    objectOutputStream = new ObjectOutputStream(bufferOut);

    objectOutputStream.writeObject(p1);
    objectOutputStream.writeObject(p2);
    objectOutputStream.close();
} finally {
    if (objectOutputStream != null) {
        objectOutputStream.close();
    }
    fileOutputStream.close();
    bufferOut.close();
    objectOutputStream.close();
}

try {

    FileInputStream fileInputStream = new FileInputStream(fileName);
    InputStream bufferIn = new BufferedInputStream(fileInputStream);
    ObjectInputStream objectInputStream
            = new ObjectInputStream(bufferIn);

    Person readCase = null;
    List<Person> recordList = new ArrayList<>();
    do {
        readCase = (Person) objectInputStream.readObject();
        if (readCase != null) {
            recordList.add(readCase);
        }
    } while (readCase != null);

    fileOutputStream.close();
    objectOutputStream.close();

} catch (FileNotFoundException err){
    err.printStackTrace();
}

怎么啦？

Answer 1

do {
        readCase = (Person) objectInputStream.readObject();
        if (readCase != null) {
            recordList.add(readCase);
        }
} while (readCase != null);

这个循环是不正确的。readObject()在流结束时不返回null。它可以在你写空的时候做到这一点。在流的末尾，它抛出EOFException。所以：

for (;;) {
    try {
        readCase = (Person) objectInputStream.readObject();
        recordList.add(readCase);
    }
    catch (EOFException exc) {
        break;
    }
}

Answer 2

正如注释中所指出的，您正在尝试读取更多的对象然后存储，如果您还不知道存储的对象的数量，可以这样做：

try{
  while(true)
    recordList.add((Person) objectInputStream.readObject());
}
catch(EOFException ex){
  //All objects are read when control is here
}