Java 解析的 JSON 数组 (GSON) 返回零或 null答案

【问题标题】：Java parsed JSON array (GSON) gives back zero or nullJava 解析的 JSON 数组 (GSON) 返回零或 null
【发布时间】：2020-10-13 11:06:34
【问题描述】：

我有一个如下所示的 JSON 数组：

[
  {
    "ScanDateTime": "2020-10-11T00:04:05",
    "RecipeName": "_BLANK_16",
    "Slot": 13,
    "DefectTotal": 0,
    "AreaCount": 3,
    "Part1": 0,
    "Part2": 0,
    "Part3": 0,
    "Part4": 0,
    "Part5": 0,
    "Part6": 0,
    "Part7": 0,
    "Part8": 0,
    "HazeRegion": 0,
    "HazeAverage": 0,
    "HazePeak": 0,
    "TotalScratch": 0
  },
  {
    "ScanDateTime": "2020-10-11T00:34:36",
    "RecipeName": "_BLANK_16",
    "Slot": 24,
    "DefectTotal": 50,
    "AreaCount": 5,
    "Part1": 21,
    "Part2": 25,
    "Part3": 0,
    "Part4": 1,
    "Part5": 1,
    "Part6": 2,
    "Part7": 0,
    "Part8": 0,
    "HazeRegion": 0,
    "HazeAverage": 0,
    "HazePeak": 0,
    "TotalScratch": 0
  },
  {
    "ScanDateTime": "2020-10-11T00:35:26",
    "RecipeName": "_BLANK_16",
    "Slot": 23,
    "DefectTotal": 192,
    "AreaCount": 2401,
    "Part1": 34,
    "Part2": 63,
    "Part3": 30,
    "Part4": 16,
    "Part5": 9,
    "Part6": 40,
    "Part7": 0,
    "Part8": 0,
    "HazeRegion": 0,
    "HazeAverage": 0,
    "HazePeak": 0,
    "TotalScratch": 39.205788
  },
  {
    "ScanDateTime": "2020-10-11T03:05:29",
    "RecipeName": "_BLANK_16",
    "Slot": 0,
    "DefectTotal": 945,
    "AreaCount": 57,
    "Part1": 273,
    "Part2": 479,
    "Part3": 93,
    "Part4": 33,
    "Part5": 35,
    "Part6": 32,
    "Part7": 0,
    "Part8": 0,
    "HazeRegion": 0,
    "HazeAverage": 0,
    "HazePeak": 0,
    "TotalScratch": 0
  },
  {
    "ScanDateTime": "2020-10-11T03:06:55",
    "RecipeName": "_BLANK_16",
    "Slot": 4,
    "DefectTotal": 842,
    "AreaCount": 78,
    "Part1": 203,
    "Part2": 469,
    "Part3": 95,
    "Part4": 33,
    "Part5": 13,
    "Part6": 29,
    "Part7": 0,
    "Part8": 0,
    "HazeRegion": 0,
    "HazeAverage": 0,
    "HazePeak": 0,
    "TotalScratch": 0
  },
  {
    "ScanDateTime": "2020-10-11T03:07:44",
    "RecipeName": "_BLANK_16",
    "Slot": 9,
    "DefectTotal": 391,
    "AreaCount": 56,
    "Part1": 125,
    "Part2": 214,
    "Part3": 25,
    "Part4": 6,
    "Part5": 11,
    "Part6": 10,
    "Part7": 0,
    "Part8": 0,
    "HazeRegion": 0,
    "HazeAverage": 0,
    "HazePeak": 0,
    "TotalScratch": 0
  }
]

我使用 GSON 对其进行解析，并有一个类 Messung，如下所示：

public class Messung {
private String scanDateTime;
private String recipeName;
private int slot;
private int defectTotal;
private int areaCount;
private int part1;
private int part2;
private int part3;
private int part4;
private int part5;
private int part6;
private int part7;
private int part8;
private double hazeRegion;
private double hazePeak;
private double totalScratch;

public Messung(String scanDateTime, String recipeName, int slot, int defectTotal1, int areaCount1, int part1, int part2, int part3, int part4, int part5, int part6, int part7, int part8, double hazeRegion, double hazePeak, double totalScratch){
    this.scanDateTime = scanDateTime;
    this.recipeName = recipeName;
    this.slot = slot;
    this.defectTotal = defectTotal1;

    this.areaCount = areaCount1;
    this.part1 = part1;
    this.part2 = part2;
    this.part3 = part3;
    this.part4 = part4;
    this.part5 = part5;
    this.part6 = part6;
    this.part7 = part7;
    this.part8 = part8;
    this.hazeRegion = hazeRegion;
    this.hazePeak = hazePeak;
    this.totalScratch = totalScratch;
}

public String getScanDateTime() {
    return scanDateTime;
}

public String getRecipeName() {
    return recipeName;
}

public int getSlot() {
    return slot;
}

public int getDefectTotal() {
    return defectTotal;
}

public int getAreaCount() {
    return areaCount;
}

public int getPart1() {
    return part1;
}

public int getPart2() {
    return part2;
}

public int getPart3() {
    return part3;
}

public int getPart4() {
    return part4;
}

public int getPart5() {
    return part5;
}

public int getPart6() {
    return part6;
}

public int getPart7() {
    return part7;
}

public int getPart8() {
    return part8;
}

public double getHazeRegion() {
    return hazeRegion;
}

public double getHazePeak() {
    return hazePeak;
}

public double getTotalScratch() {
    return totalScratch;
}

@Override
public String toString() {
    return "Messung [ScanDateTime=" + scanDateTime + ", RecipeName=" + recipeName + ", Slot=" + slot + ", DefectTotal=" + defectTotal + ", AreaCount=" + areaCount + ", Part1=" + part1 + ", Part2=" + part2 + ", Part3=" + part3 + ", Part4=" + part4 + ", Part5=" + part5 + ", Part6=" + part6 + ", Part7=" + part7 + ", Part8=" + part8 + ", HazeRegion=" + hazeRegion + ", HazePeak=" + hazePeak + ", TotalScratch=" + getTotalScratch() + "]";
}

}

这是我尝试解析的脚本部分：

while(!isExisting){
        try {
            File myObj = new File("C:\\workspace\\AccessDBReader-6420-II\\AccessDBReader-6420-II\\bin\\Release\\Publish\\Messung-6420-II.txt");
            Scanner myReader = new Scanner(myObj);
            while (myReader.hasNextLine()) {
                data = myReader.nextLine();
            }
            System.out.println(data);
            myReader.close();
            Gson gson = new Gson();
            Messung[] messungen = gson.fromJson(data, Messung[].class);

            for(Messung messung : messungen) {
                System.out.println(messung);
            }

            isExisting = true;
        } catch (FileNotFoundException e) {
            Thread.sleep(10000);
            //e.printStackTrace();
        }

但是当我尝试打印 Messung-objects 时，我得到 null 的字符串和 0 的 int 和 double：

Messung [ScanDateTime=null, RecipeName=null, Slot=0, DefectTotal=0, AreaCount=0, Part1=0, Part2=0, Part3=0, Part4=0, Part5=0, Part6=0, Part7=0, Part8=0, HazeRegion=0.0, HazePeak=0.0, TotalScratch=0.0]
Messung [ScanDateTime=null, RecipeName=null, Slot=0, DefectTotal=0, AreaCount=0, Part1=0, Part2=0, Part3=0, Part4=0, Part5=0, Part6=0, Part7=0, Part8=0, HazeRegion=0.0, HazePeak=0.0, TotalScratch=0.0]
Messung [ScanDateTime=null, RecipeName=null, Slot=0, DefectTotal=0, AreaCount=0, Part1=0, Part2=0, Part3=0, Part4=0, Part5=0, Part6=0, Part7=0, Part8=0, HazeRegion=0.0, HazePeak=0.0, TotalScratch=0.0]
Messung [ScanDateTime=null, RecipeName=null, Slot=0, DefectTotal=0, AreaCount=0, Part1=0, Part2=0, Part3=0, Part4=0, Part5=0, Part6=0, Part7=0, Part8=0, HazeRegion=0.0, HazePeak=0.0, TotalScratch=0.0]
Messung [ScanDateTime=null, RecipeName=null, Slot=0, DefectTotal=0, AreaCount=0, Part1=0, Part2=0, Part3=0, Part4=0, Part5=0, Part6=0, Part7=0, Part8=0, HazeRegion=0.0, HazePeak=0.0, TotalScratch=0.0]
Messung [ScanDateTime=null, RecipeName=null, Slot=0, DefectTotal=0, AreaCount=0, Part1=0, Part2=0, Part3=0, Part4=0, Part5=0, Part6=0, Part7=0, Part8=0, HazeRegion=0.0, HazePeak=0.0, TotalScratch=0.0]
Messung [ScanDateTime=null, RecipeName=null, Slot=0, DefectTotal=0, AreaCount=0, Part1=0, Part2=0, Part3=0, Part4=0, Part5=0, Part6=0, Part7=0, Part8=0, HazeRegion=0.0, HazePeak=0.0, TotalScratch=0.0]
Messung [ScanDateTime=null, RecipeName=null, Slot=0, DefectTotal=0, AreaCount=0, Part1=0, Part2=0, Part3=0, Part4=0, Part5=0, Part6=0, Part7=0, Part8=0, HazeRegion=0.0, HazePeak=0.0, TotalScratch=0.0]

我做错了什么？

【问题讨论】：

您的字段采用大写格式。在您的 gson 课程中更正它们

标签： java json parsing gson

【解决方案1】：

字符大小写不匹配。在您使用的 java 类中：

scanDateTime

当您的 json 文件使用时：

ScanDateTime

我会尝试在您的 java 类或 json 文件中更新案例。

【讨论】：