无法从START_ARRAY标记中反序列化java.util.HashMap的实例 [英] Can not deserialize instance of java.util.HashMap out of START_ARRAY token

问题描述

我在使用jackson-core-2.7.3.jar
解析JSON时遇到问题你可以从这里得到它们 http://repo1.maven.org/maven2/com/fasterxml/jackson/core/

I am facing issue while parsing JSON using jackson-core-2.7.3.jar You can get them from here http://repo1.maven.org/maven2/com/fasterxml/jackson/core/

我的JSON文件是

[
    {
        "Name":  "System Idle Process",
        "CreationDate":  "20160409121836.675345+330"
    },
    {
        "Name":  "System",
        "CreationDate":  "20160409121836.675345+330"
    },
    {
        "Name":  "smss.exe",
        "CreationDate":  "20160409121836.684966+330"
    }
]

我试图解析的Java代码是

and the Java Code is by which I am trying to parse this is

byte[] mapData = Files.readAllBytes(Paths.get("process.txt"));
Map<String,String> myMap = new HashMap<String, String>();
ObjectMapper objectMapper=new ObjectMapper();
myMap = objectMapper.readValue(mapData, HashMap.class);
System.out.println("Map is: "+myMap);

但在执行时我收到错误

com.fasterxml.jackson.databind.JsonMappingException: Can not deserialize instance of java.util.HashMap out of START_ARRAY token
 at [Source: [B@34ce8af7; line: 1, column: 1]
at com.fasterxml.jackson.databind.JsonMappingException.from(JsonMappingException.java:216)
at com.fasterxml.jackson.databind.DeserializationContext.mappingException(DeserializationContext.java:873)
at com.fasterxml.jackson.databind.DeserializationContext.mappingException(DeserializationContext.java:869)
at com.fasterxml.jackson.databind.deser.std.StdDeserializer._deserializeFromEmpty(StdDeserializer.java:874)
at com.fasterxml.jackson.databind.deser.std.MapDeserializer.deserialize(MapDeserializer.java:337)
at com.fasterxml.jackson.databind.deser.std.MapDeserializer.deserialize(MapDeserializer.java:26)
at com.fasterxml.jackson.databind.ObjectMapper._readMapAndClose(ObjectMapper.java:3789)
at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:2872)

我试过在stackoverflow上搜索但是找不到这种类型的JSON的匹配解决方案。

I have tried searching over stackoverflow but couldnot find a matchable solution to this type of JSON.

任何帮助我将不胜感激。

Any help would be appreciated.

注意：这里提到的 JSON 与 JSON 没有 Key ，对于第一个元素，它直接有值，并且在该值内有键：值对。
我不知道如何访问 key：value 值在一个值内。

NOTE: This JSON mentioned here is different a JSON without Key , for the first element it has value directly and inside that value it has key:valuepair. I am not sure how do I access key:value pair which is inside a value.

推荐答案

创建一个简单的 pojo Class First

Create a simple pojo Class First

class MyClass
{
@JsonProperty
private String Name;
@JsonProperty
private String CreationDate;
}

并使用此代码......

and use this code...

byte[] mapData = Files.readAllBytes(Paths.get("process.txt"));

ObjectMapper objectMapper=new ObjectMapper();
//add this line  
objectMapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);    
List<MyClass> myObjects = mapper.readValue(mapData , new TypeReference<List<MyClass>>(){});

或

byte[] mapData = Files.readAllBytes(Paths.get("process.txt"));

ObjectMapper objectMapper=new ObjectMapper();
 //add this line  
objectMapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);    

List<MyClass> myObjects = mapper.readValue(mapData , mapper.getTypeFactory().constructCollectionType(List.class, MyClass.class));

myObjects 将包含 列表 MyClass 。现在，您可以根据自己的要求访问此列表。

myObjects will contains the List of MyClass. Now you can access this list as per your requirement.

这篇关于无法从START_ARRAY标记中反序列化java.util.HashMap的实例的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！