Java 使用“反序列化JSON映射”；“关键”&&引用；“价值”；属性不适用于Jackson

问题

@JsonIgnoreProperties(ignoreUnknown = true)  
public class Attributes {

    public Attributes() {}

    private ArrayList<Entry> entry;  

    public ArrayList<Entry> getEntry() {
        return entry;
    }    
}

首先，下面的序列化JSON序列化有意义吗

如果是这样的话，我为什么不拿回地图

在反序列化方面我能做些什么

映射属性的JSON序列化（节选）：

{
  "attributes": {
    "entry": [
      {
        "key": "operating system",
        "value": "GNU/Linux"
      },
      {
        "key": "allergies",
        "value": "weed"
      }
    ]
  }
}

class Contact implements Comparable<Contact>, Serializable {
    @JsonProperty("attributes")
    private Map<String, String> attributes;
    ...
}

@JsonProperty("attributes")
private Map<String, List<Map<String, String>>> attributes;

POJO用于反序列化：

{
  "attributes": {
    "entry": [
      {
        "key": "operating system",
        "value": "GNU/Linux"
      },
      {
        "key": "allergies",
        "value": "weed"
      }
    ]
  }
}

class Contact implements Comparable<Contact>, Serializable {
    @JsonProperty("attributes")
    private Map<String, String> attributes;
    ...
}

@JsonProperty("attributes")
private Map<String, List<Map<String, String>>> attributes;

反序列化后在调试器中检查属性对象：

{
  "attributes": {
    "entry": [
      {
        "key": "operating system",
        "value": "GNU/Linux"
      },
      {
        "key": "allergies",
        "value": "weed"
      }
    ]
  }
}

class Contact implements Comparable<Contact>, Serializable {
    @JsonProperty("attributes")
    private Map<String, String> attributes;
    ...
}

@JsonProperty("attributes")
private Map<String, List<Map<String, String>>> attributes;

更改为后的进一步检查：

{
  "attributes": {
    "entry": [
      {
        "key": "operating system",
        "value": "GNU/Linux"
      },
      {
        "key": "allergies",
        "value": "weed"
      }
    ]
  }
}

class Contact implements Comparable<Contact>, Serializable {
    @JsonProperty("attributes")
    private Map<String, String> attributes;
    ...
}

@JsonProperty("attributes")
private Map<String, List<Map<String, String>>> attributes;

@JsonProperty（“属性”）
私有地图属性；

依赖关系：

{
  "attributes": {
    "entry": [
      {
        "key": "operating system",
        "value": "GNU/Linux"
      },
      {
        "key": "allergies",
        "value": "weed"
      }
    ]
  }
}

class Contact implements Comparable<Contact>, Serializable {
    @JsonProperty("attributes")
    private Map<String, String> attributes;
    ...
}

@JsonProperty("attributes")
private Map<String, List<Map<String, String>>> attributes;

• com.fasterxml.jackson.core:jackson-core:2.3.0
• core:jackson-databind:2.3.0
• core:jackson注释：2.3.0

---

如果我们将

Map

转换为json：

    Map<String, String> map = new HashMap<String, String>();
    map.put("operating system", "GNU/Linux");
    map.put("allergies", "weed");

正如我们所看到的，没有

键/值

解决方案 WrapperObject

@JsonIgnoreProperties(ignoreUnknown = true)
public class WrapperObject { // we can give any name to class, its only external {}    

    private Attributes attributes;

    public WrapperObject() {}

    public Attributes getAttributes() {
        return attributes;
    }    
}

属性

@JsonIgnoreProperties(ignoreUnknown = true)  
public class Attributes {

    public Attributes() {}

    private ArrayList<Entry> entry;  

    public ArrayList<Entry> getEntry() {
        return entry;
    }    
}

启动器

public static void main(String[] args) throws JsonParseException, JsonMappingException,     IOException {
    String str = "{" + 
            "  \"attributes\": {" + 
            "    \"entry\": [" + 
            "      {" + 
            "        \"key\": \"operating system\"," + 
            "        \"value\": \"GNU/Linux\"" + 
            "      }," + 
            "      {" + 
            "        \"key\": \"allergies\"," + 
            "        \"value\": \"weed\"" + 
            "      }" + 
            "    ]" + 
            "  }" + 
            "}";

    
    
    ObjectMapper mapper = new ObjectMapper();
    WrapperObject mj = mapper.readValue(str, WrapperObject.class);

    if(mj == null){
        System.err.println("null");
    }
    // dummy check
    System.out.println(mj.getAttributes().getEntry().get(0).getKey());
}

输出：

operating system