面试题：Java反序列化中如何确保基本数据类型的数据一致性

使用标准序列化机制：

Java提供了标准的java.io.Serializable接口和ObjectInputStream/ObjectOutputStream类来进行对象的序列化和反序列化。对于基本数据类型，遵循这些标准机制能最大程度保证一致性。例如：

import java.io.*;

class Data implements Serializable {
    int num;
    double value;

    public Data(int num, double value) {
        this.num = num;
        this.value = value;
    }
}

public class SerializeDemo {
    public static void main(String[] args) {
        Data data = new Data(10, 3.14);
        try {
            FileOutputStream fileOut = new FileOutputStream("data.ser");
            ObjectOutputStream out = new ObjectOutputStream(fileOut);
            out.writeObject(data);
            out.close();
            fileOut.close();

            FileInputStream fileIn = new FileInputStream("data.ser");
            ObjectInputStream in = new ObjectInputStream(fileIn);
            Data deserializedData = (Data) in.readObject();
            in.close();
            fileIn.close();
            System.out.println("Deserialized int: " + deserializedData.num);
            System.out.println("Deserialized double: " + deserializedData.value);
        } catch (IOException i) {
            i.printStackTrace();
        } catch (ClassNotFoundException c) {
            System.out.println("Data class not found");
            c.printStackTrace();
        }
    }
}

校验和机制：

在序列化时，计算基本数据类型的校验和。例如对于int和double，可以使用java.util.zip.CRC32类计算校验和。
序列化时：

import java.io.*;
import java.util.zip.CRC32;

class DataWithChecksum implements Serializable {
    int num;
    double value;
    long checksum;

    public DataWithChecksum(int num, double value) {
        this.num = num;
        this.value = value;
        calculateChecksum();
    }

    private void calculateChecksum() {
        CRC32 crc32 = new CRC32();
        crc32.update(new byte[]{(byte) (num >> 24), (byte) (num >> 16), (byte) (num >> 8), (byte) num});
        long doubleBits = Double.doubleToLongBits(value);
        crc32.update(new byte[]{(byte) (doubleBits >> 56), (byte) (doubleBits >> 48), (byte) (doubleBits >> 40), (byte) (doubleBits >> 32), (byte) (doubleBits >> 24), (byte) (doubleBits >> 16), (byte) (doubleBits >> 8), (byte) doubleBits});
        this.checksum = crc32.getValue();
    }
}

反序列化时，重新计算校验和并与序列化时保存的校验和对比。

import java.io.*;
import java.util.zip.CRC32;

public class DeserializeWithChecksum {
    public static void main(String[] args) {
        try {
            FileInputStream fileIn = new FileInputStream("dataWithChecksum.ser");
            ObjectInputStream in = new ObjectInputStream(fileIn);
            DataWithChecksum deserializedData = (DataWithChecksum) in.readObject();
            in.close();
            fileIn.close();

            CRC32 crc32 = new CRC32();
            crc32.update(new byte[]{(byte) (deserializedData.num >> 24), (byte) (deserializedData.num >> 16), (byte) (deserializedData.num >> 8), (byte) deserializedData.num});
            long doubleBits = Double.doubleToLongBits(deserializedData.value);
            crc32.update(new byte[]{(byte) (doubleBits >> 56), (byte) (doubleBits >> 48), (byte) (doubleBits >> 40), (byte) (doubleBits >> 32), (byte) (doubleBits >> 24), (byte) (doubleBits >> 16), (byte) (doubleBits >> 8), (byte) doubleBits});
            long calculatedChecksum = crc32.getValue();

            if (calculatedChecksum == deserializedData.checksum) {
                System.out.println("Data is consistent.");
                System.out.println("Deserialized int: " + deserializedData.num);
                System.out.println("Deserialized double: " + deserializedData.value);
            } else {
                System.out.println("Data consistency check failed.");
            }
        } catch (IOException i) {
            i.printStackTrace();
        } catch (ClassNotFoundException c) {
            System.out.println("DataWithChecksum class not found");
            c.printStackTrace();
        }
    }
}

版本控制：
- 在类中添加一个serialVersionUID字段。如果数据结构发生变化，更新这个版本号。
```
class DataWithVersion implements Serializable {
    private static final long serialVersionUID = 1L;
    int num;
    double value;

    public DataWithVersion(int num, double value) {
        this.num = num;
        this.value = value;
    }
}
```
- 反序列化时，Java会检查类的serialVersionUID与序列化数据中的版本号是否匹配。如果不匹配，会抛出InvalidClassException，防止使用不一致的数据。

数据范围检查：

在反序列化后，检查基本数据类型的值是否在合理的范围内。例如，int的范围是-2147483648到2147483647，double也有其特定的取值范围。

class DataRangeCheck {
    int num;
    double value;

    public DataRangeCheck(int num, double value) {
        this.num = num;
        this.value = value;
    }

    public boolean isDataInRange() {
        return num >= Integer.MIN_VALUE && num <= Integer.MAX_VALUE &&
               value >= Double.MIN_VALUE && value <= Double.MAX_VALUE;
    }
}

反序列化后调用isDataInRange方法进行检查。

面试题：Java反序列化中如何确保基本数据类型的数据一致性

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