fastjson字节数组序列化与反序列化注意事项base64

墨蓝 2022-11-13 15:24 223阅读 0赞

## 场景 ##

在某通讯场景中发送和接收的消息都是JSON字符串格式（这里不讨论那种格式对于通信更高效）。 其中payload是\[\]byte格式，在发送时将数据部分进行打包放入map，然后JSON.toJSONString(map);后发送， 收到数据后进行  
(Map) JSON.parseObject(json); 此时里面的payload都是字符串，需要主动**base64.decode**再转换为byte，

## 代码 ##

public class JsonDemo { 
        private static final String PAYLOAD_KEY = "payload";
        private static final String SEQ_ID_KEY = "seqId";
    
        public static void main(String[] args) throws Exception { 
            Map<String, Object> map = new HashMap<>(16);
            byte[] originalByte =  new byte[]{ 1, 127, -5};
            map.put(PAYLOAD_KEY, originalByte);
            map.put(SEQ_ID_KEY, 123);
            System.out.println("originalPayLoadByte:" + Arrays.toString(originalByte));
            String jsonStr = JSON.toJSONString(map);
            System.out.println("jsonStr:" + jsonStr);
            //这里这直接进行转换没有类型check
            Map<String, Object> receivedMap =  (Map) JSON.parseObject(jsonStr);
            System.out.println("receivedMap:" + receivedMap);
            String payloadStr = (String)receivedMap.get(PAYLOAD_KEY);
            byte[] payloadByte = payloadStr.getBytes();
            System.out.println("receivedPayLoadStr:" + payloadStr);
    
            byte[] payloadDecodeByte = Base64.decode(payloadStr);
    
            if (originalByte.length !=  payloadByte.length) { 
                System.out.println("payloadByte != originalByte. the getBytes() can't be used.");
            }
    
            if (originalByte.length ==  payloadDecodeByte.length) { 
                for (int i=0; i < originalByte.length; i++ ) { 
                    if (originalByte[i] != payloadDecodeByte[i] ) { 
                        System.out.println("payloadDecodeByte != originalByte");
                        break;
                    }
                }
            } else { 
                System.out.println("payloadDecodeByte != originalByte");
                return;
            }
    
            System.out.println("payloadDecodeByte == originalByte");
        }
    }

## 运行截图 ##

![在这里插入图片描述][watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3J1c3NsZQ_size_16_color_FFFFFF_t_70_pic_center]

## 进一步 ##

那如不是字节数组，而是string数据组，会出现什么情况了？

扩展原有代码,（代码比较凌乱和啰嗦，主要是为了展示日常编程是可能进行类型判断， 实际开发时如果通过debug一次就知道具体的类型，不会在代码中这样处理） 。  
注意这里的展示代码只是判断了类型，并没有进一步处理，读者可根据自己实际业务进行后续处理。

package com.citic.plat.demo;
    
    import com.alibaba.fastjson.JSON;
    import com.alibaba.fastjson.JSONArray;
    import com.sun.org.apache.xerces.internal.impl.dv.util.Base64;
    import org.yaml.snakeyaml.util.ArrayUtils;
    
    import java.util.Arrays;
    import java.util.HashMap;
    import java.util.Map;
    
    /** * Created by EricYang on 2021/3/27. */
    
    public class JsonDemo { 
        private static final String PAYLOAD_KEY = "payload";
        private static final String SEQ_ID_KEY = "seqId";
        private static final String PAYLOAD2_KEY = "payload2";
    
        public static void main(String[] args) throws Exception { 
            Map<String, Object> map = new HashMap<>(16);
            byte[] originalByte =  new byte[]{ 1, 127, -5};
            String[] originalString =  new String[]{ "01str", "03str", "03str"};
            map.put(PAYLOAD_KEY, originalByte);
            map.put(SEQ_ID_KEY, 123);
            map.put(PAYLOAD2_KEY, originalString);
            System.out.println("originalPayLoadByte:" + Arrays.toString(originalByte));
            String jsonStr = JSON.toJSONString(map);
            System.out.println("jsonStr:" + jsonStr);
            //这里这直接进行转换没有类型check
            Map<String, Object> receivedMap =  (Map) JSON.parseObject(jsonStr);
            System.out.println("receivedMap:" + receivedMap);
            String payloadStr = (String)receivedMap.get(PAYLOAD_KEY);
            byte[] payloadByte = payloadStr.getBytes();
            System.out.println("receivedPayLoadStr:" + payloadStr);
    
            Object payload2Obj = receivedMap.get(PAYLOAD2_KEY);
            if (payload2Obj instanceof  String) { 
                String payload2Str = (String) payload2Obj;
                System.out.println("payload2 is str:" + payload2Str);
            } else if (payload2Obj instanceof String[]) { 
                String[] payload2StrArray = (String[]) payload2Obj;
                System.out.println("payload2 is strArray:" +  Arrays.toString(payload2StrArray));
            } else if (payload2Obj instanceof Object[]) { 
                Object[] payload2ObjrArray = (Object[]) payload2Obj;
                System.out.println("payload2 is ObjArray:" +  Arrays.toString(payload2ObjrArray));
            } else if (payload2Obj instanceof JSONArray) { 
                JSONArray payload2JsonArray = (JSONArray)payload2Obj;
                System.out.println("payload2 is payload2JsonArray:" );
            } else { 
                System.out.println("payload2 is not str, either strArray:" + payload2Obj );
            }
    
            byte[] payloadDecodeByte = Base64.decode(payloadStr);
    
            if (originalByte.length !=  payloadByte.length) { 
                System.out.println("payloadByte != originalByte. the getBytes() can't be used.");
            }
    
            if (originalByte.length ==  payloadDecodeByte.length) { 
                for (int i=0; i < originalByte.length; i++ ) { 
                    if (originalByte[i] != payloadDecodeByte[i] ) { 
                        System.out.println("payloadDecodeByte != originalByte");
                        break;
                    }
                }
            } else { 
                System.out.println("payloadDecodeByte != originalByte");
                return;
            }
    
            System.out.println("payloadDecodeByte == originalByte");
        }
    }

结果

originalPayLoadByte:[1, 127, -5]
    jsonStr:{ "payload2":["01str","03str","03str"],"payload":"AX/7","seqId":123}
    receivedMap:{ "payload2":["01str","03str","03str"],"payload":"AX/7","seqId":123}
    receivedPayLoadStr:AX/7
    payload2 is payload2JsonArray:
    payloadByte != originalByte. the getBytes() can't be used.
    payloadDecodeByte == originalByte

可以看到，新的类型是JSONArray

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3J1c3NsZQ_size_16_color_FFFFFF_t_70_pic_center]: /images/20221022/531cec9a62ce4e8b8e2f84a6474c94b8.png