Java-使用jakson将json转换为复杂对象

这可能会重复这个问题，但我已经寻找了很多解决方案，但并没有运气。 我的课程如下：

public class RestartMapState {

    public RestartMapState(List<MapStepData> vMapStepData, List<AbstractMap.SimpleEntry<String,String>> vResolvedParameters, String vJobID){
        this.vJobID=vJobID;
        this.vResolvedParameters = vResolvedParameters;
        this.vMapStepData = vMapStepData;
    }

    public RestartMapState(){}

    private List<MapStepData> vMapStepData;
    public void setvMapStepData(List<MapStepData> mapStepData){ this.vMapStepData = mapStepData; }
    public List<MapStepData> getvMapStepData(){
        return this.vMapStepData;
    }

    private List<AbstractMap.SimpleEntry<String,String>> vResolvedParameters;
    public List<AbstractMap.SimpleEntry<String,String>> getvResolvedParameters(){  return this.vResolvedParameters; }
    public void setvResolvedParameters(List<AbstractMap.SimpleEntry<String,String>> resolvedParameters){ this.vResolvedParameters = resolvedParameters; }

    private String vJobID;
    public String getvJobID(){ return this.vJobID; }
    public void setvJobID(String jobID){ this.vJobID = jobID; }
}

{
  "vMapStepData" : [ {
    "dependsOn" : null,
    "orderIndex" : 0,
    "name" : "Step1",
    "mapStepId" : 167119,
    "sqlstatements" : {
      "sqlstatement" : [ {
        "value" : "-- Map Step   (Step1)\nCREATE TABLE ##!sessionid##Step1\n    AS\nSELECT currency_nbr AS currency_nbr,...",
        "orderIndex" : 1,
        "isQuery" : false,
        "flags" : [ "PartOfCore" ]
      } ]
    }
  }, {
    "dependsOn" : null,
    "orderIndex" : 1,
    "name" : "Step2",
    "mapStepId" : 237822,
    "sqlstatements" : {
      "sqlstatement" : [ {
        "value" : "\n\n-- Map Step   (Step2)\nCREATE TABLE ##!sessionid##Step2\n    AS\nSELECT country_cd AS ....",
        "orderIndex" : 1,
        "isQuery" : false,
        "flags" : [ "PartOfCore" ]
      } ]
    }
  } ],
  "vResolvedParameters" : [ {
    "key" : "##RUNDATE##",
    "value" : "2018045"
  }, {
    "key" : "##julian##",
    "value" : "2018033"
  } ],
  "vJobID" : "10012"
}

我的JSON文件如下所示：

public class RestartMapState {

    public RestartMapState(List<MapStepData> vMapStepData, List<AbstractMap.SimpleEntry<String,String>> vResolvedParameters, String vJobID){
        this.vJobID=vJobID;
        this.vResolvedParameters = vResolvedParameters;
        this.vMapStepData = vMapStepData;
    }

    public RestartMapState(){}

    private List<MapStepData> vMapStepData;
    public void setvMapStepData(List<MapStepData> mapStepData){ this.vMapStepData = mapStepData; }
    public List<MapStepData> getvMapStepData(){
        return this.vMapStepData;
    }

    private List<AbstractMap.SimpleEntry<String,String>> vResolvedParameters;
    public List<AbstractMap.SimpleEntry<String,String>> getvResolvedParameters(){  return this.vResolvedParameters; }
    public void setvResolvedParameters(List<AbstractMap.SimpleEntry<String,String>> resolvedParameters){ this.vResolvedParameters = resolvedParameters; }

    private String vJobID;
    public String getvJobID(){ return this.vJobID; }
    public void setvJobID(String jobID){ this.vJobID = jobID; }
}

{
  "vMapStepData" : [ {
    "dependsOn" : null,
    "orderIndex" : 0,
    "name" : "Step1",
    "mapStepId" : 167119,
    "sqlstatements" : {
      "sqlstatement" : [ {
        "value" : "-- Map Step   (Step1)\nCREATE TABLE ##!sessionid##Step1\n    AS\nSELECT currency_nbr AS currency_nbr,...",
        "orderIndex" : 1,
        "isQuery" : false,
        "flags" : [ "PartOfCore" ]
      } ]
    }
  }, {
    "dependsOn" : null,
    "orderIndex" : 1,
    "name" : "Step2",
    "mapStepId" : 237822,
    "sqlstatements" : {
      "sqlstatement" : [ {
        "value" : "\n\n-- Map Step   (Step2)\nCREATE TABLE ##!sessionid##Step2\n    AS\nSELECT country_cd AS ....",
        "orderIndex" : 1,
        "isQuery" : false,
        "flags" : [ "PartOfCore" ]
      } ]
    }
  } ],
  "vResolvedParameters" : [ {
    "key" : "##RUNDATE##",
    "value" : "2018045"
  }, {
    "key" : "##julian##",
    "value" : "2018033"
  } ],
  "vJobID" : "10012"
}

但是，当我尝试将同一个json文件反序列化为RestartMapState类型的对象时，我得到了以下错误

org.codehaus.jackson.map.JsonMappingException: No suitable constructor found for type [simple type, class java.util.AbstractMap$SimpleEntry<java.lang.String,java.lang.String>]: can not instantiate from JSON object (need to add/enable type information?)
 at [Source: C:\Users\vkukk1\.MAP_STATE_System_Test_Group_Vasu_Test_2_10012.json; line: 30, column: 5] (through reference chain: com.aexp.idn.magellan.RestartMapState["vResolvedParameters"]) RestartMapState vRestartMapState = null;

org.codehaus.jackson.map.JsonMappingException:找不到适合类型[simple type，class java.util.AbstractMap$SimpleEntry]的构造函数：无法从JSON对象实例化（需要添加/启用类型信息？）
在[Source:C:\Users\vkukkk1\.MAP\u STATE\u System\u Test\u Group\u Vasu\u Test\u 2\u 10012.json；第30行，第5列]（通过引用链：com.aexp.idn.magelan.RestartMapState[“vResolvedParameters”]）RestartMapState vRestartMapState=null；

---

有人能帮我解决这个问题吗？我做错了什么？

类

抽象映射。SimpleEntry

没有默认构造函数（没有参数），无法反序列化。
您应该将

vResolvedParameters

的泛型类型从

AbstractMap.SimpleEntry

更改为其他类型：

private List<Pair<String, String>> vResolvedParameters;
public List<Pair<String, String>> getvResolvedParameters() {
    return this.vResolvedParameters;
}
public void setvResolvedParameters(List<Pair<String, String>> resolvedParameters) {
    this.vResolvedParameters = resolvedParameters;
}

您可以使用许多其他库中的

对

实现

或者，如果

“key”

的值是唯一的，您可以将

vResolvedParameters

类型更改为

Map

。但您的JSON格式将从：

...
"vResolvedParameters" : [ {
  "key" : "##RUNDATE##",
  "value" : "2018045"
}, {
  "key" : "##julian##",
  "value" : "2018033"
} ],
...

致：

---

我终于解决了这个问题。问题是关于vResolvedParameter的getter方法。我将getter方法更改如下：

private List<MapStepData> vMapStepData;
public void setvMapStepData(List<MapStepData> mapStepData){ this.vMapStepData = mapStepData; }
public List<MapStepData> getvMapStepData(){ return this.vMapStepData; }

private Map<String,String> vResolvedParameters;
public Map<String,String> getvResolvedParameters() { return this.vResolvedParameters; }

私有列表vMapStepData；
public void setvMapStepData（List mapStepData）{this.vMapStepData=mapStepData；}
public List getvMapStepData（）{返回this.vMapStepData；}
私有地图vResolvedParameters；
公共映射getvResolvedParameters（）{返回this.vResolvedParameters；}

---

谢谢@Nokolay.

即使我改为Map，我也会遇到以下异常：-org.codehaus.jackson.Map.JsonMappingException:无法在[Source:C:\Test_2_10012.json；line:28，column:6]（通过引用链：com.aexp.idn.magellan.RestartMapState）反序列化java.util.LinkedHashMap的实例[“vResolvedParameters”]）顺便说一句，我没有在任何地方使用LinkedHashMap，我不知道为什么我会得到

MapStepData

类的这个例外添加代码

private List<MapStepData> vMapStepData;
public void setvMapStepData(List<MapStepData> mapStepData){ this.vMapStepData = mapStepData; }
public List<MapStepData> getvMapStepData(){ return this.vMapStepData; }

private Map<String,String> vResolvedParameters;
public Map<String,String> getvResolvedParameters() { return this.vResolvedParameters; }