10. ProtoStuff不支持BigDecimal序列化/反序列化记录

平时使用ProtoStuff作为序列化工具，对于一些POJO对象序列化，但是在实际使用中，发现针对BigDecimal对象进行序列化时却出现了问题

• 不管什么数，生成的byte数组都一样
• 无法正确反序列化

下面记录一下这个问题

1. 场景复现

我们使用的protostuff依赖如下

 <dependency>
    <groupId>com.dyuproject.protostuff</groupId>
    <artifactId>protostuff-core</artifactId>
    <version>1.1.3</version>
</dependency>
<dependency>
    <groupId>com.dyuproject.protostuff</groupId>
    <artifactId>protostuff-runtime</artifactId>
    <version>1.1.3</version>
</dependency>

写一个简单测试demo，如下

public static byte[] serialize(Object obj) {
    Schema schema = RuntimeSchema.getSchema(obj.getClass());
    LinkedBuffer buffer = LinkedBuffer.allocate(1048576);

    byte[] protoStuff;
    try {
        protoStuff = ProtostuffIOUtil.toByteArray(obj, schema, buffer);
    } catch (Exception var8) {
        throw new RuntimeException("Failed to serializer");
    } finally {
        buffer.clear();
    }

    return protoStuff;
}

public static <T> T deserialize(byte[] paramArrayOfByte, Class<T> targetClass) {
    if (paramArrayOfByte != null && paramArrayOfByte.length != 0) {
        Schema<T> schema = RuntimeSchema.getSchema(targetClass);
        T instance = schema.newMessage();
        ProtostuffIOUtil.mergeFrom(paramArrayOfByte, instance, schema);
        return instance;
    } else {
        throw new RuntimeException("Failed to deserialize");
    }
}


@Test
public void testSer() {
    byte[] ans = serialize(new BigDecimal(20));
    byte[] ans2 = serialize(new BigDecimal(120));

    System.out.println(new String(ans));
    System.out.println(new String(ans2));

    BigDecimal res = deserialize(ans, BigDecimal.class);
    System.out.println(res);
}

执行如下

2. 疑似原因与兼容方法

并没有找到具体的原因，在github上有一个issure: https://github.com/protostuff/protostuff/issues/245，其中回复为

Protostuff works on user-defined types (pojos), not on built-in jdk types.

上面的说法是ProtoStuff更多的是用于简单对象的序列化，而不是基础的jdk类型，因此推荐的是序列一个成员变量为BigDecimal的对象

接下来我们试一下，定义一个简单的对象，成员为BigDecimal的场景

@Data
public static class InnerDecimal {
    private BigDecimal decimal;

    public InnerDecimal() {
    }

    public InnerDecimal(BigDecimal decimal) {
        this.decimal = decimal;
    }
}

@Test
public void testSer() {
    byte[] ans = serialize(new InnerDecimal(new BigDecimal(20.123)));
    byte[] ans2 = serialize(new InnerDecimal(new BigDecimal(120.1970824)));

    System.out.println(new String(ans));
    System.out.println(new String(ans2));

    InnerDecimal res = deserialize(ans, InnerDecimal.class);
    System.out.println(res);
}

测试输出如下

上面虽然可以正常工作，但与我们希望的差别有点大，序列化一个BigDecimal，还需要定义一个POJO包装他，有点麻烦；于是一个猥琐的方法就是在序列化和反序列化的时候，针对BigDeimal进行特殊处理

public static byte[] serialize(Object obj) {
    if (obj instanceof BigDecimal) {
        obj = ((BigDecimal) obj).toPlainString();
    }

    Schema schema = RuntimeSchema.getSchema(obj.getClass());
    LinkedBuffer buffer = LinkedBuffer.allocate(1048576);

    byte[] protoStuff;
    try {
        protoStuff = ProtostuffIOUtil.toByteArray(obj, schema, buffer);
    } catch (Exception var8) {
        throw new RuntimeException("Failed to serializer");
    } finally {
        buffer.clear();
    }

    return protoStuff;
}

public static <T> T deserialize(byte[] paramArrayOfByte, Class<T> targetClass) {
    if (paramArrayOfByte != null && paramArrayOfByte.length != 0) {
        Schema schema;
        if (targetClass.isAssignableFrom(BigDecimal.class)) {
            schema = RuntimeSchema.getSchema(String.class);
            Object instance = schema.newMessage();
            ProtostuffIOUtil.mergeFrom(paramArrayOfByte, instance, schema);
            return (T) new BigDecimal((String) instance);
        } else {
            schema = RuntimeSchema.getSchema(targetClass);
            Object instance = schema.newMessage();
            ProtostuffIOUtil.mergeFrom(paramArrayOfByte, instance, schema);
            return (T) instance;
        }
    } else {
        throw new RuntimeException("Failed to deserialize");
    }
}

再次测试，正常执行