关于java中常见数据格式的问题

╰+哭是因爲堅強的太久メ 2021-12-18 14:19 248阅读 0赞

## 关于java中常见数据格式的问题（底层的数据结构方面的知识先不研究了…,这里只是记录下偶然发现的问题） ##

#### 一、定义 ####

数据格式：是描述数据保存在文件或记录中的规则。可以是字符形式的文本格式，或二进制数据形式的压缩格式。字符形式的文本格式占用的存贮空间多但透明度高，二进制数形式的压缩格式占用的存贮空间少但缺少透明度。

#### 二、问题引出 ####

今天想处理excel数据，用Java封装的Jar包去解析，入库时，发现引用的工具对Excel读取时，返回的是 List，并不能真正返回我希望的List,

[
     [1, 阿拉巴马州, Alabama, AL, 蒙哥马利, Montgomery, null],
     [2, 阿拉斯加州, Alaska, AK, 朱诺, Juneau, null],
     [3, 阿利桑那州, Arizona, AZ, 菲尼克斯, Phoenix, null],
     [4, 阿肯色州, Arkansas, AR, 小石城, Little rock, null],
     [5, 加利福尼亚州, California, CA, 萨克拉门托, Sacramento, null], 
     [6, 科罗拉多州, Colorado, CO, 丹佛, Denver, null], 
     [7, 康涅狄格州, Connecticut, CT, 哈特福德, Hartford, null],
     [8, 特拉华州, Delaware, DE, 多佛, Dover, null], 
     [9, 佛罗里达州, Florida, FL, 塔拉哈西, Tallahassee, null]
      ]

这个数据其实是List的，在处理的时候，先遍历第一层，在把第二层Object强转成List，然后对对象进行Set赋值操作，即可完成解析，返回所希望返回的List。

处理后返回的数据格式为以下：

[
    State(id=1, chName=阿拉巴马州, enName=Alabama, code=AL, captial=蒙哥马利, capitalen=Montgomery, remark=null), 
    State(id=2, chName=阿拉斯加州, enName=Alaska, code=AK, captial=朱诺, capitalen=Juneau, remark=null), 
    State(id=3, chName=阿利桑那州, enName=Arizona, code=AZ, captial=菲尼克斯, capitalen=Phoenix, remark=null), 
    State(id=4, chName=阿肯色州, enName=Arkansas, code=AR, captial=小石城, capitalen=Little rock, remark=null), 
    State(id=5, chName=加利福尼亚州, enName=California, code=CA, captial=萨克拉门托, capitalen=Sacramento, remark=null), 
    State(id=6, chName=科罗拉多州, enName=Colorado, code=CO, captial=丹佛, capitalen=Denver, remark=null), 
    State(id=7, chName=康涅狄格州, enName=Connecticut, code=CT, captial=哈特福德, capitalen=Hartford, remark=null), 
    State(id=8, chName=特拉华州, enName=Delaware, code=DE, captial=多佛, capitalen=Dover, remark=null), 
    State(id=9, chName=佛罗里达州, enName=Florida, code=FL, captial=塔拉哈西, capitalen=Tallahassee, remark=null)
    ]

#### 三、Java中数据传输几种格式 ####

##### 3.1 JSON #####

基本格式

{ 
    "BigIntSupported": 995815895020119788889,
    "date": "20180322",
    "message": "Success !",
    "status": 200,
    "city": "北京",
    "count": 632,
    "data": { 
    "shidu": "34%",
    "pm25": 73,
    "pm10": 91,
    "quality": "良",
    "wendu": "5",
    "ganmao": "极少数敏感人群应减少户外活动",
    "yesterday": { 
    "date": "21日星期三",
    "sunrise": "06:19",
    "high": "高温 11.0℃",
    "low": "低温 1.0℃",
    "sunset": "18:26",
    "aqi": 85,
    "fx": "南风",
    "fl": "<3级",
    "type": "多云",
    "notice": "阴晴之间，谨防紫外线侵扰"
    },
    "forecast": [
    { 
    "date": "22日星期四",
    "sunrise": "06:17",
    "high": "高温 17.0℃",
    "low": "低温 1.0℃",
    "sunset": "18:27",
    "aqi": 98,
    "fx": "西南风",
    "fl": "<3级",
    "type": "晴",
    "notice": "愿你拥有比阳光明媚的心情"
    },
    { 
    "date": "23日星期五",
    "sunrise": "06:16",
    "high": "高温 18.0℃",
    "low": "低温 5.0℃",
    "sunset": "18:28",
    "aqi": 118,
    "fx": "无持续风向",
    "fl": "<3级",
    "type": "多云",
    "notice": "阴晴之间，谨防紫外线侵扰"
    },
    { 
    "date": "24日星期六",
    "sunrise": "06:14",
    "high": "高温 21.0℃",
    "low": "低温 7.0℃",
    "sunset": "18:29",
    "aqi": 52,
    "fx": "西南风",
    "fl": "<3级",
    "type": "晴",
    "notice": "愿你拥有比阳光明媚的心情"
    },
    { 
    "date": "25日星期日",
    "sunrise": "06:13",
    "high": "高温 22.0℃",
    "low": "低温 7.0℃",
    "sunset": "18:30",
    "aqi": 71,
    "fx": "西南风",
    "fl": "<3级",
    "type": "晴",
    "notice": "愿你拥有比阳光明媚的心情"
    },
    { 
    "date": "26日星期一",
    "sunrise": "06:11",
    "high": "高温 21.0℃",
    "low": "低温 8.0℃",
    "sunset": "18:31",
    "aqi": 97,
    "fx": "西南风",
    "fl": "<3级",
    "type": "多云",
    "notice": "阴晴之间，谨防紫外线侵扰"
    }
    ]
    }
    }

优点  
a.数据格式比较简洁，也便于阅读和解析，  
b.具有自我描述性，易于阅读编写，也易于机器解析与生成  
c.使用 Javascript语法来描述数据对象，但是 JSON 仍然独立于语言和平台。JSON 解析器和 JSON 库支持许多不同的编程语言。 目前非常多的动态（PHP，JSP，.NET）编程语言都支持JSON  
d.非常适用于服务器与JavaScript交互

##### 3.2 XML(eXtensible Markup Language) #####

基本格式：

<note>
    	<to>George</to>
    	<from>John</from>
    	<heading>Reminder</heading>
    	<body>Don't forget the meeting!</body>
    </note>

是基于标签库的数据,优点:  
a.读取XML文档  
b.使用XML DOM循环遍历文档  
c.读取值并存储与变量

##### 3.3 YAML(Yet Another Markup Language) #####

基本格式

#YAML格式
    environments:
        dev:
            url: http://dev.bar.com
            name: Developer Setup
        prod:
            url: http://foo.bar.com
            name: My Cool App
    my:
        servers:
            - dev.bar.com
            - foo.bar.com

springtoot架构中常见的  
优点：  
a.由于实现简单，解析成本低，特别适合在脚本语言中使用  
b.YAML比较适合做序列化。因为它是宿主语言数据类型直转的。  
c.YAML做配置文件也不错。比如Ruby on Rails的配置就选用的YAML。

#### 四、java 中常见的数据格式问题 ####

##### 4.1 List #####

[
    State(id=1, chName=E, enName=D, code=C, captial=B, capitalen=A, remark=F), 
    State(id=1, chName=E, enName=D, code=C, captial=B, capitalen=A, remark=F), 
    State(id=1, chName=E, enName=D, code=C, captial=B, capitalen=A, remark=F), 
    State(id=1, chName=E, enName=D, code=C, captial=B, capitalen=A, remark=F),
    State(id=1, chName=E, enName=D, code=C, captial=B, capitalen=A, remark=F)
    ]

转成Json后

[
    {"capitalen":"A","code":"C","enName":"D","remark":"F","id":1,"captial":"B","chName":"E"},
    {"capitalen":"A","code":"C","enName":"D","remark":"F","id":1,"captial":"B","chName":"E"},
    {"capitalen":"A","code":"C","enName":"D","remark":"F","id":1,"captial":"B","chName":"E"},
    {"capitalen":"A","code":"C","enName":"D","remark":"F","id":1,"captial":"B","chName":"E"},
    {"capitalen":"A","code":"C","enName":"D","remark":"F","id":1,"captial":"B","chName":"E"}
    ]

##### 4.2 Map #####

{a=State(id=1, chName=E, enName=D, code=C, captial=B, capitalen=A, remark=F), 
    b=State(id=1, chName=E, enName=D, code=C, captial=B, capitalen=A, remark=F), 
    c=State(id=1, chName=E, enName=D, code=C, captial=B, capitalen=A, remark=F)}

转成Json后

{
    "a": {
    "capitalen": "A",
    "code": "C",
    "enName": "D",
    "remark": "F",
    "id": 1,
    "captial": "B",
    "chName": "E"
    },
    "b": {
    "capitalen": "A",
    "code": "C",
    "enName": "D",
    "remark": "F",
    "id": 1,
    "captial": "B",
    "chName": "E"
    },
    "c": {
    "capitalen": "A",
    "code": "C",
    "enName": "D",
    "remark": "F",
    "id": 1,
    "captial": "B",
    "chName": "E"
    }
    }

##### 4.3 Pojo #####

State(id=1, chName=E, enName=D, code=C, captial=B, capitalen=A, remark=F)

对应的Json

{
    "capitalen": "A",
    "code": "C",
    "enName": "D",
    "remark": "F",
    "id": 1,
    "captial": "B",
    "chName": "E"
    }

##### 4.4 Array #####

这里其实是数组的底层的是引用数据类型，toString方法只是显示其在内存中的位置

转成Json后

["s","a","f","g","h"]

备注，这里的Pojo转String，默认是其toString方法

public String toString() {
            return "McnRecordVo(" +
                    "programId=" + programId +
                    ", contentId=" + contentId +
                    ')';
        }

是可以重写其ToString方法，这样的返回就可以和Map格式一模一样了

@Override
        public String toString() {
            return "McnRecordVo{" +
                    "programId=" + programId +
                    ", contentId=" + contentId +
                    '}';
        }