Instanceof returns false for same class 序列化后

Question

Instanceof returns false for same class after org.springframework.security.oauth2.common.util.SerializationUtils fasterxml deserialization in Spring boot application

new ObjectMapper().readValue(serialized, User.class);

Class

public class User implements Serializable {//...
}

因为新对象 getClass().getClassloader() returns 不同的 classloader，如何解决这个问题和 casting 问题？

Answer 1

在这种情况下，您应该比较 class 个名称，而不是使用 instanceof。即使 classes 由不同的 class 加载程序加载，规范名称也将相同：

public boolean haveSameCanonicalName(Object object, Class<?> clazz) {
     String actualClassName = object.getClass().getCanonicalName();
     String expectedClassName = clazz.getCanonicalName();
     return actualClassName.equals(expectedClassName);
}

然后你可以这样使用它：

if (haveSameCanonicalName(user, User.class)) {
    // Do something here
}

更新：

如果您仍然需要转换对象，有一个解决方法：

 public class CrossCastUtils {

    private final ObjectOutputStream oos;
    private final ObjectInputStream ois;

    public CrossCastUtils() throws IOException {
        final PipedOutputStream pos = new PipedOutputStream();
        final PipedInputStream pis = new PipedInputStream(pos);
        oos = new ObjectOutputStream(pos);
        ois = new ObjectInputStream(pis);
    }

    public <T> T cast(Object object) throws IOException, ClassNotFoundException {
        oos.writeObject(object);
        oos.flush();
        return (T) ois.readObject();
    }

尝试运行这个测试：

@Test
public void testCrossCast(){
    Object initial = ... // retrieve it as you did before
    User result = CrossCastUtils.cast(initial);

    assertFalse(initial instanceof User);
    assertTrue(result instanceof User);
}

Instanceof returns false for same class 序列化后

Instanceof returns false for same class after serialization

java

serialization

spring

class

classloader