反序列化序列化对象时出现 ClassNotFound 异常

Question

我正在尝试序列化和反序列化一个对象。此对象可以包含对其他对象以及 ArrayList 和 HashMap 的引用。

当我尝试执行我的代码时，序列化工作正常，但反序列化没有。它会导致以下异常：

Exception in thread "main" java.lang.ClassNotFoundException: experiment.Experiment
    at java.net.URLClassLoader.findClass(URLClassLoader.java:381)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:331)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
    at java.lang.Class.forName0(Native Method)
    at java.lang.Class.forName(Class.java:348)
    at javax.crypto.extObjectInputStream.resolveClass(SealedObject.java:490)
    at java.io.ObjectInputStream.readNonProxyDesc(ObjectInputStream.java:1613)
    at java.io.ObjectInputStream.readClassDesc(ObjectInputStream.java:1518)
    at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1774)
    at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1351)
    at java.io.ObjectInputStream.defaultReadFields(ObjectInputStream.java:2000)
    at java.io.ObjectInputStream.readSerialData(ObjectInputStream.java:1924)
    at java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:1801)
    at java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1351)
    at java.io.ObjectInputStream.readObject(ObjectInputStream.java:371)
    at javax.crypto.SealedObject.getObject(SealedObject.java:302)
    at experiment.Experiment.main(Experiment.java:52)
Java Result: 1

我有主要的class，实验，如下：

public class Experiment {  
    public static void main(String[] args) throws Exception {
        File data = new File("C:\Users\Furze\Desktop\experiment.dat");   
        // I only execute the following to encrypt the file, which works fine:
        Test test = new Test(new VariableMap<String, String>() {{
            put("Name", "Furze");
        }});   
        Cipher cipher = Cipher.getInstance("Blowfish");
        cipher.init(Cipher.ENCRYPT_MODE, new SecretKeySpec(new byte[] {0x00,0x01,0x02,0x03,0x04,0x05,0x06,0x07}, "Blowfish"));
        SealedObject sealedObject = new SealedObject(test, cipher);
        CipherOutputStream outputStream = new CipherOutputStream(new BufferedOutputStream(new FileOutputStream(data.getPath())), cipher);
        ObjectOutputStream objectOutput = new ObjectOutputStream(outputStream);
        objectOutput.writeObject(sealedObject);     
        objectOutput.close();
        // I then comment out the above code to test the file, which fails.
        Cipher cipher = Cipher.getInstance("Blowfish");
        cipher.init(Cipher.DECRYPT_MODE, new SecretKeySpec(new byte[] {0x00,0x01,0x02,0x03,0x04,0x05,0x06,0x07}, "Blowfish"));
        CipherInputStream inputStream = new CipherInputStream(new BufferedInputStream(new FileInputStream(data.getPath())), cipher);
        ObjectInputStream objectInput = new ObjectInputStream(inputStream);
        SealedObject sealedObject = (SealedObject) objectInput.readObject();
        Test test = (Test) sealedObject.getObject(cipher);
        System.out.println(test.variables.get("Name"));
    }
}

奇怪的是，如果我在回读时完整地保留 Test test = new Test(...); 部分，但将名称更改为 test_old 之类的名称，它似乎可以正常工作。

对象class如下：

// The VariableMap class is something I added during debugging to test if HashMap simply isn't serializable. It didn't help. It does have to stay a HashMap (or VariableMap!) however, for my code to operate correctly.
class VariableMap<Name, Value> extends HashMap<String, String> implements java.io.Serializable {
    public VariableMap() {
        super();
    }
}

public class Test implements java.io.Serializable {
    VariableMap<String, String> variables = new VariableMap<>();
    public Test() {}
    public Test(VariableMap<String, String> variables) {
        this.variables = variables;
    }
}

谁能解释一下我的代码可能出了什么问题？我读过有关更改 CLASSPATH 的内容，但是当我尝试这样做时，它没有任何区别。

Answer 1

您缺少 class 顶部的包裹声明，它应该是：

package experiment;

public class Experiment implements Serializable {
    public static void main(String[] args) throws Exception {
        File data = new File("C:\Users\Furze\Desktop\experiment.dat");   
        // I only execute the following to encrypt the file, which works fine:
        Test test = new Test(new VariableMap<String, String>() {{
            put("Name", "Furze");
        }});   
        Cipher cipher = Cipher.getInstance("Blowfish");
        cipher.init(Cipher.ENCRYPT_MODE, new SecretKeySpec(new byte[] {0x00,0x01,0x02,0x03,0x04,0x05,0x06,0x07}, "Blowfish"));
        SealedObject sealedObject = new SealedObject(test, cipher);
        CipherOutputStream outputStream = new CipherOutputStream(new BufferedOutputStream(new FileOutputStream(data.getPath())), cipher);
        ObjectOutputStream objectOutput = new ObjectOutputStream(outputStream);
        objectOutput.writeObject(sealedObject);     
        objectOutput.close();
        // I then comment out the above code to test the file, which fails.
        Cipher cipher = Cipher.getInstance("Blowfish");
        cipher.init(Cipher.DECRYPT_MODE, new SecretKeySpec(new byte[] {0x00,0x01,0x02,0x03,0x04,0x05,0x06,0x07}, "Blowfish"));
        CipherInputStream inputStream = new CipherInputStream(new BufferedInputStream(new FileInputStream(data.getPath())), cipher);
        ObjectInputStream objectInput = new ObjectInputStream(inputStream);
        SealedObject sealedObject = (SealedObject) objectInput.readObject();
        Test test = (Test) sealedObject.getObject(cipher);
        System.out.println(test.variables.get("Name"));
    }
}

Answer 2

情况

What is Double Brace initialization in Java?

new VariableMap<String, String>() {{
    put("Name", "Furze");
}}

创建一个匿名内部 class（class VariableMap 的子class）并创建它的对象。

class和对象都是在同一个地方创建的。

自 all subtypes of a serializable class are themselves serializable 以来仍然是 Serializable。

问题

当你评论它时，class定义本身消失 .

这导致上述 ClassNotFoundException。

解决方案

如果可以，尽量避免Serialization。实现自己的数据存储机制。
如果必须使用 Serialization，请避免双括号初始化。
保持声明而不使用它（test_old 方式）。然而，这是一个临时解决方案和不好的做法。这是令人困惑且无法记住的。也是未来错误的可能原因。

反序列化序列化对象时出现 ClassNotFound 异常

ClassNotFound Exception when deserializing serialized object

java

serialization

exception

object

classnotfoundexception

情况

问题

解决方案