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java - Java中的反序列化在多种方法中无法一致地工作

问题描述

deletebook()在该方法中创建 FileInputStream 时出现错误 。但是相同的对象创建在该 searchBook()方法中起作用。当唯一不同的是传递给方法的参数时，有谁知道为什么代码会产生不同的结果？

import java.io.EOFException;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.io.ObjectOutputStream;
import java.time.LocalDate;
import java.time.format.DateTimeFormatter;
import java.util.ArrayList;
import java.util.List;
import java.util.Scanner;

public class TestMain {
    public static final String FILENAME = "cool_file.txt";
    public static void main(String[] args) throws IOException, ClassNotFoundException {
        // TODO Auto-generated method stub
        FileOutputStream fos = null;
        fos = new FileOutputStream(FILENAME);
        System.out.println("Welcome to the Application");
        ObjectOutputStream oos1;
        int sel = 0;
        TestMain t = new TestMain();
        do {
            System.out.println("1) addSubject");
            System.out.println("2) addBook");
            System.out.println("3) deleteSubject");
            System.out.println("4) deleteBook");
            System.out.println("5) searchBook");
            System.out.println("6) searchSubject");
            System.out.println("7) Exit");
            System.out.println("#############");
            System.out.println("Insert a selection");
            Scanner s = new Scanner(System.in);
            sel = s.nextInt();

            switch (sel) {
            case 1:
                t.addSubject();
                break;
            case 2:
                t.addBook(fos);
                break;
            case 3:
                t.deleteSubject();
                break;
            case 4:
                t.deleteBook(fos);
                break;
            case 5:
                t.searchBook();
                break;
            case 6:
                t.searchSubject();
                break;
            case 7:
                t.exitService();
                break;
            default:
                System.out.println("Invalid Selection");
            }

        } while (sel != 7);

    }

    public void addSubject() {
        System.out.println("In addSubject"+"\n");
        }

    public void addBook(FileOutputStream fos) throws IOException {
        System.out.println("In addBook"+"\n");
        long bookId;
        String title;
        double price;
        Integer volume;
        LocalDate publishDate;
        ObjectOutputStream oos = new ObjectOutputStream(fos);
        System.out.println("Enter Book ID");
        Book b=new Book();
        Scanner s=new Scanner(System.in);
        bookId=s.nextLong();
        System.out.println("Enter the Title of the Book");
        title=s.next();
        System.out.println("Enter the price of the Book");
        price=s.nextDouble();
        System.out.println("Enter the Volume of the Book");
        volume=s.nextInt();
        System.out.println("Enter the publishDate of the Book");
        String dateStr_1=s.next();
           DateTimeFormatter formatter_1=DateTimeFormatter.ofPattern("dd-MM-yyyy");
            publishDate= LocalDate.parse(dateStr_1,formatter_1);
            b.setBookId(bookId);
            b.setTitle(title);
            b.setPrice(price);
            b.setVolume(volume);
            b.setPublishDate(publishDate);

            oos.writeObject(b);
            //fos.close();
            //oos.close();

    }


    public void deleteSubject() {
        System.out.println("In deleteSubject"+"\n");
    }

    public void deleteBook(FileOutputStream fos) throws IOException, ClassNotFoundException {
        System.out.println("In deleteBook"+"\n");
        System.out.println("Enter the Book Id to be deleted");
        Scanner s=new Scanner(System.in);
        int bookId=s.nextInt();
        ArrayList<Book> results = new ArrayList<Book>();

        FileInputStream fis = null;
        System.out.println(fis);
        try {
            fis = new FileInputStream(FILENAME);
            System.out.println(fis);
            while (true) {
                ObjectInputStream ois = new ObjectInputStream(fis);
                results.add((Book) ois.readObject());
            }
        } catch (EOFException ignored) {
            ignored.printStackTrace();
            // as expected
        } finally {
            if (fis != null)
                fis.close();
            System.out.println("Finally");
        }
        System.out.println("results = " + results);
        for(Book b:results)
        {
        if(b.getBookId()==bookId)   
        {
            results.remove(b);
        }
        }

        File file = new File(FILENAME);

        if(file.exists())
        {
            file.delete();
            System.out.println("File Exists");
            if(file.exists())
                {
                System.out.println("File Exists after deletion");
            }
        }
            if(file.delete())
        {
            System.out.println("File deleted successfully");
        }
        else
        {
            System.out.println("Failed to delete the file");
        }

        /*ObjectOutputStream oos = new ObjectOutputStream(fos);
        for(Book newb:results)
        oos.writeObject(newb);*/


    }
    public void searchBook() throws ClassNotFoundException, IOException {
        System.out.println("In searchBook"+"\n");
         ArrayList<Book> results = new ArrayList<Book>();

            FileInputStream fis = null;
            try {
                fis = new FileInputStream(FILENAME);
                while (true) {
                    ObjectInputStream ois = new ObjectInputStream(fis);
                    results.add((Book) ois.readObject());
                }
            } catch (EOFException ignored) {
                // as expected
            } finally {
                if (fis != null)
                    fis.close();
            }
            System.out.println("results = " + results);

    }
    public void searchSubject() {
        System.out.println("In searchSubject"+"\n");

    }
    public void exitService() {
        System.out.println("Thank You for using the service..You rare now Exitinng the service");

    }
}

这是控制台：

欢迎使用应用程序 1) addSubject 2) addBook 3) deleteSubject 4) deleteBook 5) searchBook 6) searchSubject 7) 退出

####### 插入选择 2 在 addBook

输入图书 ID 1 输入图书标题 ufihv 输入图书价格 1 输入图书数量 1 输入图书发布日期 01-01-2001 1) addSubject 2) addBook 3) deleteSubject 4) deleteBook 5) searchBook 6) searchSubject 7) 退出

####### 插入选择 2 在 addBook

输入图书 ID 2 输入图书名称 2 输入图书价格 2 输入图书数量 2 输入图书发布日期 02-02-2002 1) addSubject 2) addBook 3) deleteSubject 4) deleteBook 5) searchBook 6) searchSubject 7) 退出

####### 插入选择 4 在 deleteBook

输入要删除的Book Id 1 null java.io.FileInputStream@7106e68e java.io.EOFException finally results = [Book@1a6c5a9e, Book@37bba400] File Exists File Exists after delete 删除文件失败 1) addSubject 2) addBook 3) deleteSubject 4) deleteBook 5) searchBook 6) searchSubject 7) 退出

####### 在 java.io.ObjectInputStream$PeekInputStream.readFully(Unknown Source) 处插入选择

在 java.io.ObjectInputStream$BlockDataInputStream.readShort(Unknown Source) 在 java.io.ObjectInputStream.readStreamHeader(Unknown Source) 在 java.io.ObjectInputStream.(Unknown Source) 在 TestMain.deleteBook(TestMain.java:124) 在 TestMain .main(TestMain.java:49)

标签： javafile

解决方案

我不太确定，为什么要删除具有对象可序列化状态的文件。因此，当您删除具有对象可序列化状态的文件时。即使文件不存在，您也会失去一切。而且，如果您尝试以其他方法访问相同的文件，您将得到异常。

此外，当您删除特定对象时，您不会将对象的最新更新状态保存到文件（您没有序列化对象的最新状态），而是直接删除了文件。那么，从反序列化对象中删除对象有什么意义呢？

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