Java序列化与Serializable（三）父类实现如果未实现序列化，子类表现

最新推荐文章于 2021-09-28 12:27:27 发布

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博客探讨了Java中父类构造函数对序列化的影响。指出子类承担责任需父类有无参构造方法，通过两种情况测试：父类无无参构造函数时，序列化成功但反序列化报错，父类属性未序列化；父类有无参构造时，虽可序列化反序列化，但父类属性未参与该过程。

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父类未实现序列化

To allow subtypes of non-serializable classes to be serialized, the
* subtype may assume responsibility for saving and restoring the
* state of the supertype's public, protected, and (if accessible)
* package fields.  The subtype may assume this responsibility only if
* the class it extends has an accessible no-arg constructor to
* initialize the class's state.  It is an error to declare a class
* Serializable if this is not the case.  The error will be detected at
* runtime. <p>

The subtype may assume this responsibility only if * the class it extends has an accessible no-arg constructor to * initialize the class's state.

也就是说需要父类要有无参的构造方法。

我们试一下如果是没有父类无参的构造函数会怎么样

因为父类如果没有写构造函数的话，默认会有一个无参的构造函数，所以我们这样写

第一种情况父类没有无参的构造函数

父类：

public class BaseBean   {
   public String property1;
   public String property2;

   public BaseBean(String id){

   }
}

子类

public class TestBean extends BaseBean  implements Serializable{
        public String desc;
    public static final int serialVersionUID = 1;
    public TestBean(String id) {
        super(id);
    }

    @Override
    public String toString() {
        return "TestBean{" +
                "desc='" + desc + '\'' +
                ", property1='" + property1 + '\'' +
                ", property2='" + property2 + '\'' +
                '}';
    }

}

这个时候序列化的过程没有出什么问题，但是反序列的时候开始报错了

//序列化之后通过给父类再加上默认构造方法，这个时候反序列化可以看到其实即便父类没有默认构造参数，序列化的过程也是

成功了的。但是1，不能反序列化，2，父类的属性没有序列化到，只序列化了子类的属性

java.io.InvalidClassException: calc.superdy.ttest.test.TestBean; no valid constructor

第二种情况父类有无参构造

通过上面的例子，可以知道，如果父类没有无参构造函数，则序列化过程不能成功

下面加下无参构造，看下情况

public class BaseBean   {
   public String property1;
   public String property2;

   public BaseBean(String id){

   }

   public BaseBean(){}

}

public class TestBean extends BaseBean  implements Serializable{
        public String desc;
    public static final int serialVersionUID = 1;
    public TestBean(String id) {
        super(id);
    }

    @Override
    public String toString() {
        return "TestBean{" +
                "desc='" + desc + '\'' +
                ", property1='" + property1 + '\'' +
                ", property2='" + property2 + '\'' +
                '}';
    }

}

   public void serialization(View view) {
        try {

            TestBean testBean = new TestBean("");
            testBean.property1 = "属性88999988";
            testBean.property2 = "属性88999988";
            testBean.desc = "我是testbean88999988";

            ObjectOutputStream objectOutputStream = new ObjectOutputStream(new FileOutputStream("/sdcard/aaatest.txt"));
            objectOutputStream.writeObject(testBean);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    public void deserialization(View view) {
        ObjectInputStream objectInputStream = null;
        try {
            objectInputStream = new ObjectInputStream(new FileInputStream("/sdcard/aaatest.txt"));
            TestBean testBean = (TestBean) objectInputStream.readObject();
            Log.i(TAG,"deserialization"+testBean.toString());
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

这个时候打印结果为：

deserializationTestBean{desc='我是testbean88999988', property1='null', property2='null'}

也就是说，虽然可以序列化反序列化成功，但是父类的属性其实并没有参与到序列化反序列化的过程中来