Java Jackson映射器未映射所有字段

我使用jackson将我的POJO数组转换为json，但它没有在输出中提供一个特定字段，其中as gson.toJson提供输出。有人能帮忙吗

public class TestCenter implements Comparable<TestCenter>{


    private Integer no_of_accessible_tests=0;
    private Integer tagId;
    private String tag;
    private Integer number_of_tests=0;

    private List<Test> tests= new ArrayList<>();

    public Integer getTagId() {
        return tagId;
    }
    public void setTagId(Integer tagId) {
        this.tagId = tagId;
    }
    public String getTag() {
        return tag;
    }
    public void setTag(String tag) {
        this.tag = tag;
    }
    public Integer getNumber_of_tests() {
        return number_of_tests;
    }
    public void setNumber_of_tests(Integer number_of_tests) {
        this.number_of_tests = number_of_tests;
    }
    public List<Test> getTests() {
        return tests;
    }
    public void setTests(List<Test> tests) {
        this.tests = tests;
    }

    public void addTest(Test t)
    {

        this.tests.add(t);
        this.number_of_tests++;
        if("Yes".equals(t.getAccess()))
            this.no_of_accessible_tests++;
    }
    @Override
    public int compareTo(TestCenter o) {

        if(this.no_of_accessible_tests.equals(o.no_of_accessible_tests))
        {
            return number_of_tests.compareTo(o.number_of_tests);
        }
        else
        {
            return o.no_of_accessible_tests.compareTo(this.no_of_accessible_tests);
        }
    }


}

System.out.println(gson.toJson(tests));
          System.out.println(mapper.writeValueAsString(tests));
          return mapper.writeValueAsString(tests);
output for both:
[{"no_of_accessible_tests":0,"tagId":196,"tag":"IBPS Clerical Prelims","number_of_tests":1,"tests":[{"activatedDate":null,"activatedTime":null,"ScheduleDate":null,"ScheduleTime":null,"endDate":null,"endTime":null,"testId":2193,"testCode":"P15 CP FLT 61","testName":"Amazon -4","testType":"flt","testPattern":"ibps","testDurationInMinutes":120,"numberOfQuestions":104,"access":"No","status":"start","testResult":null,"tags":["2017","IBPS Clerical Prelims"]}]},{"no_of_accessible_tests":0,"tagId":0,"tag":"Others","number_of_tests":6,"tests":[{"activatedDate":null,"activatedTime":null,"ScheduleDate":null,"ScheduleTime":null,"endDate":null,"endTime":null,"testId":2525,"testCode":"CP 16 FLT 04","testName":"Tech Mahindra -4","testType":"flt","testPattern":"ibps","testDurationInMinutes":65,"numberOfQuestions":76,"access":"No","status":"start","testResult":null,"tags":null},{"activatedDate":"2015-12-17","activatedTime":"09:00:00","ScheduleDate":"2015-12-17","ScheduleTime":"09:00:00","endDate":"license end date","endTime":"license end time","testId":2188,"testCode":"P15 CP FLT 58","testName":"Amazon -1","testType":"flt","testPattern":"ibps","testDurationInMinutes":120,"numberOfQuestions":104,"access":"No","status":"Resume","testResult":null,"tags":null},{"activatedDate":"2015-12-17","activatedTime":"09:00:00","ScheduleDate":"2015-12-17","ScheduleTime":"09:00:00","endDate":"license end date","endTime":"license end time","testId":2190,"testCode":"P15 CP FLT 59","testName":"Amazon -2","testType":"flt","testPattern":"ibps","testDurationInMinutes":120,"numberOfQuestions":104,"access":"No","status":"start","testResult":null,"tags":null},{"activatedDate":null,"activatedTime":null,"ScheduleDate":null,"ScheduleTime":null,"endDate":null,"endTime":null,"testId":2192,"testCode":"P15 CP FLT 60","testName":"Amazon -3","testType":"flt","testPattern":"ibps","testDurationInMinutes":120,"numberOfQuestions":104,"access":"No","status":"start","testResult":null,"tags":null},{"activatedDate":null,"activatedTime":null,"ScheduleDate":null,"ScheduleTime":null,"endDate":null,"endTime":null,"testId":1929,"testCode":"P15 CP FLT 09","testName":"CapGemini -1","testType":"flt","testPattern":"ibps","testDurationInMinutes":60,"numberOfQuestions":75,"access":"No","status":"start","testResult":null,"tags":null},{"test_ready":"no","reason_student_side":"This test would be available on 22-Dec-16.","reason_admin_side":".","testId":2633,"testCode":"BP FLT 87","testName":"SBI Specialist Officer Test -5","testType":"flt","testPattern":"ibps","testDurationInMinutes":90,"numberOfQuestions":120,"access":"No","status":"start","testResult":null,"tags":null}]}]
[{"tagId":196,"tag":"IBPS Clerical Prelims","number_of_tests":1,"tests":[{"testId":2193,"testCode":"P15 CP FLT 61","testName":"Amazon -4","testType":"flt","testPattern":"ibps","testDurationInMinutes":120,"numberOfQuestions":104,"access":"No","status":"start","testResult":null,"tags":["2017","IBPS Clerical Prelims"],"activatedDate":null,"activatedTime":null,"endDate":null,"endTime":null,"scheduleDate":null,"scheduleTime":null}]},{"tagId":0,"tag":"Others","number_of_tests":6,"tests":[{"testId":2525,"testCode":"CP 16 FLT 04","testName":"Tech Mahindra -4","testType":"flt","testPattern":"ibps","testDurationInMinutes":65,"numberOfQuestions":76,"access":"No","status":"start","testResult":null,"tags":null,"activatedDate":null,"activatedTime":null,"endDate":null,"endTime":null,"scheduleDate":null,"scheduleTime":null},{"testId":2188,"testCode":"P15 CP FLT 58","testName":"Amazon -1","testType":"flt","testPattern":"ibps","testDurationInMinutes":120,"numberOfQuestions":104,"access":"No","status":"Resume","testResult":null,"tags":null,"activatedDate":"2015-12-17","activatedTime":"09:00:00","endDate":"license end date","endTime":"license end time","scheduleDate":"2015-12-17","scheduleTime":"09:00:00"},{"testId":2190,"testCode":"P15 CP FLT 59","testName":"Amazon -2","testType":"flt","testPattern":"ibps","testDurationInMinutes":120,"numberOfQuestions":104,"access":"No","status":"start","testResult":null,"tags":null,"activatedDate":"2015-12-17","activatedTime":"09:00:00","endDate":"license end date","endTime":"license end time","scheduleDate":"2015-12-17","scheduleTime":"09:00:00"},{"testId":2192,"testCode":"P15 CP FLT 60","testName":"Amazon -3","testType":"flt","testPattern":"ibps","testDurationInMinutes":120,"numberOfQuestions":104,"access":"No","status":"start","testResult":null,"tags":null,"activatedDate":null,"activatedTime":null,"endDate":null,"endTime":null,"scheduleDate":null,"scheduleTime":null},{"testId":1929,"testCode":"P15 CP FLT 09","testName":"CapGemini -1","testType":"flt","testPattern":"ibps","testDurationInMinutes":60,"numberOfQuestions":75,"access":"No","status":"start","testResult":null,"tags":null,"activatedDate":null,"activatedTime":null,"endDate":null,"endTime":null,"scheduleDate":null,"scheduleTime":null},{"testId":2633,"testCode":"BP FLT 87","testName":"SBI Specialist Officer Test -5","testType":"flt","testPattern":"ibps","testDurationInMinutes":90,"numberOfQuestions":120,"access":"No","status":"start","testResult":null,"tags":null,"test_ready":"no","reason_student_side":"This test would be available on 22-Dec-16.","reason_admin_side":"."}]}]

公共类TestCenter实现了可比较的{
可访问测试的私有整数编号=0；
私有整数tagId；
私有字符串标签；
_测试的私有整数_=0；
私有列表测试=新建ArrayList（）；
公共整数getTagId（）{
返回标记ID；
}
public void setTagId（整型tagId）{
this.tagId=tagId；
}
公共字符串getTag（）{
返回标签；
}
公共void setTag（字符串标记）{
this.tag=tag；
}
公共整数getNumber of_tests（）{
返回测试的次数；
}
公共无效集合测试的数量（测试的整数）{
这是。测试次数=测试次数；
}
公共列表getTests（）{
回归测试；
}
公共无效设置测试（列表测试）{
这个。测试=测试；
}
公共测试（测试t）
{
本.试验.添加（t）；
这个。测试的数量++；
如果（“是”。等于（t.getAccess（））
这个。没有可访问的测试++；
}
@凌驾
公共int比较（测试中心o）{
if（这是可访问测试的数量等于（可访问测试的数量））
{
返回测试的数量。比较（o.测试的数量）；
}
其他的
{
返回o.no\u of_accessible\u tests.compareTo（此为.no\u of_accessible\u tests）；
}
}
}
System.out.println（gson.toJson（tests））；
System.out.println（mapper.writeValueAsString（tests））；
返回mapper.writeValueAsString（测试）；
两者的输出：
[{“no_of_accessible_tests”：0，“tagId”：196，“tag”：“IBPS文书预备”、“数量_tests”：1，“tests”：[{“activatedate”：null，“activatedTime”：null，“ScheduleDate”：null，“scheduledtime”：null，“endDate”：null，“endTime”：null，“testId”：2193，“testCode”：“P15 CP FLT 61”，“testName”：“Amazon-4”，“testType”：“FLT”，“testPattern”：“IBPS”，“testDurationInMinutes”：120，“numberOfQuestions”：104，“access:“No”，“status:“start”，“testResult:”null，“tags:”[“2017”，“IBPS文书预备课”]}]，{“No_of_accessible__tests:”0，“tagId:”0，“tag:”Others”，“number of_tests:”6，“tests:”[{“activatedDate:”null，“activatedTime:”null，“ScheduleDate:”null，“ScheduleTime:”null，“endDate:”null，“endTime:”null，“testId:”2525，“testCode:”CP 16 FLT 04“，”testName“：”Tech Mahindra-4“，”testType“：”flt“，”testPattern“：”ibps“，”testDurationInMinutes“：”65，“numberOfQuestions“，”access“，”否“，”状态“，”开始“，”testResult“，”空“，”标签“：”空“，”激活日期“：”09:00:00“，”时间表日期“：”2015-12-17“，”时间表时间“：”09:00:00:00“，”结束日期“，”结束日期“，”结束时间“，”，“testId”：2188，“testCode”：“P15 CP FLT 58”，“testName”：“Amazon-1”，“testType”：“FLT”，“testPattern”：“ibps”，“testDurationInMinutes”：120，“numberOfQuestions”：104，“access”：“No”，“status”：“Resume”，“testResult”：null，“tags”：null}，{“activatedDate”：“2015-12-17”，“activatedTime”：“09:00:00”，“ScheduleDate”：“2015-12-17”，“ScheduleTime”：“09:00:00”，“endDate”：“许可证结束日期”，“结束时间”：“许可证结束时间”，“测试ID”：2190，“测试代码”：“P15 CP FLT 59”，“测试名称”：“Amazon-2”，“测试类型”：“FLT”，“测试模式”：“ibps”，“testDurationInMinutes”：120，“numberOfQuestions”：104，“访问”：“否”，“状态”：“开始”，“测试结果”：null，“标记”：null}，{“activatedDate”：null，“activatedTime”：null，“ScheduleDate”：null，“ScheduleTime”：null，”endDate:null，“endTime:null”，testId:2192，“testCode”：“P15 CP FLT 60”，“testName”：“Amazon-3”，“testType”：“FLT”，“testPattern”：“ibps”，“testDurationInMinutes”：120，“numberOfQuestions”：104，“access”：“No”，“status”：“start”，“testResult”：null，“tags”：null}，{“activatedDate”：null，“activatedTime”：null，“ScheduleDate”：null，“ScheduleTime”：null，“endDate”：null，”endTime:null，“testId”：1929，“testCode”：“P15 CP FLT 09”，“testName”：“CapGemini-1”，“testType”：“FLT”，“testPattern”：“ibps”，“testDurationInMinutes”：60，“numberOfQuestions”：75，“access”：“No”，“status”：“start”，“testResult”：null，“tags”：null}，{“test ready”：“No”，“reason\u student\u side”：“此测试将于2016年12月22日提供”，“reason\u admin\u side”：“testId”“：2633，“测试代码”：“BP FLT 87”，“测试名称”：“SBI专家官员测试-5”，“测试类型”：“FLT”，“测试模式”：“ibps”，“测试持续时间分钟”：90，“numberOfQuestions”：120，“访问”：“否”，“状态”：“开始”，“测试结果”：null，“标记”：null}]]
[{“tagId”：196，“tag”：“IBPS文书预备课”，“测试次数”：1，“测试”：[{“testId”：2193，“testCode”：“P15 CP FLT 61”，“testName”：“Amazon-4”，“testType”：“FLT”，“testPattern”：“IBPS”，“testDurationInMinutes”：120，“numberOfQuestions”：104，“access”：“No”，“status”：“start”，“testResult”：null，“tags”：[“2017”，“IBPS文书预备课”]，“activatedDate”：null，“activatedTime”：null，“endDate”：null，“endTime”：null，“scheduleDate”：null，“scheduleTime”：null}}，{“tagId”：0，“tag”：“其他”，“测试次数”：6，“测试”：[{“testId”：2525，“testCode”：“CP 16 FLT 04”，“testName”：“Tech Mahindra-4”，“testType”：“FLT”，“testPattern”：“ibps”，“testDurationInMinutes”：65，“numberOfQuestions”：76，“access”：“No”，“status”：“start”testResult:null，“tags:null，”activatedDate:null，“activatedTime:null，”endDate:null，“scheduleDate:null”，scheduleDate:null}，{“testId”：2188，“testCode”：“P15 CP FLT 58”，“testName”：“Amazon-1”，“testType”：“FLT”，“testPattern”：“ibps”，“testdurationofminutes”：120，“numberquestions”：104，“access”：“No”，“status”：“Resume”，“testResult”：null，”标签：null，“activatedDate”：“2015-12-17”，“activatedTime”：“09:00:00”，“endDate”：“许可证结束日期”，“endTime”：“许可证结束时间”，“scheduleDate”：“2015-12-17”，“scheduleTime”：“09:00:00”}，{“testId”：2190，“testCode”：“P15 CP FLT 59”，“testName”：“Amazon-2”，“testType”：“FLT”，“testPattern”：“ibps”，“TestDurationnMinutes”：120，“numberOfQuestions”：104，“access”：“No”状态：“开始”，“测试结果”：null，“标记”：null，“激活日期”：“2015-12-17”，“激活日期”：“09:00:00”，“结束日期”：“许可证结束日期”，“结束时间”：“许可证结束时间”，“日程日期”：“2015-12-17”，“日程时间”：“09:00:00”}，{“testId”：2192，“测试代码”：“P15 CP FLT”