如何使用jackson在java中解包和序列化java映射？

How to unwrap and serialize java map in java using Hymanson?

提问by Suren Raju

I have a bean like this

我有一颗这样的豆子

class Foo {
    private Map<String, Data> dataMap;
    private String fooFieldOne;
    private String fooFieldTwo;
}

class Data {
    private fieldOne;
    private fieldTwo;
}

I want to serialize as Json as like this

我想像这样序列化为 Json

{
    "key1": {
        "fieldOne": "some value",
        "fieldTwo": "some value"
    },
    "key2": {
        "fieldOne": "some other value",
        "fieldTwo": "some other value"
    },
    "fooFieldOne":"valueone", 
    "fooFieldTwo":"valuetwo" 
}

But i am getting result like

但我得到的结果是

{
    "dataMap": {
        "key1": {
            "fieldOne": "some value",
            "fieldTwo": "some value"
        },
        "key2": {
            "fieldOne": "some other value",
            "fieldTwo": "some other value"
        }
    },
    "fooFieldOne":"valueone", 
    "fooFieldTwo":"valuetwo" 
}

How to ignore dataMap layer in the above json? I'm using java Hymanson library for this.

如何忽略上面json中的dataMap层？我为此使用了 java Hymanson 库。

Code i tried is

我试过的代码是

ObjectMapper mapper = new ObjectMapper();
mapper.writeValueAsString(myFOOObject)

采纳答案by Bart

You could create a getter for dataMapand serialize the dataMapinstead of the entire Fooinstance.

您可以为dataMap创建一个 getter并序列化dataMap而不是整个Foo实例。

mapper.writeValueAsString(myFOOObject.getDataMap());

Another method is using the @JsonUnwrappedannotation. This annotation is available in Hymanson 1.9+.

另一种方法是使用@JsonUnwrapped注释。此注释在 Hymanson 1.9+ 中可用。

http://Hymanson.codehaus.org/1.9.9/javadoc/org/codehaus/Hymanson/annotate/JsonUnwrapped.html

http://Hymanson.codehaus.org/1.9.9/javadoc/org/codehaus/Hymanson/annotate/JsonUnwrapped.html

The downside of using this annotation is the inability to use maps as stated in the answer to your other question

使用此注释的缺点是无法使用其他问题的答案中所述的地图

回答by sanbhat

You are getting

你得到

{ "dataMap": ... } 

because Foohas a fieldcalled dataMapwithin it. Here the name of the field cannot be ignoredbecause it will create conflictsif Foohad multiple maps, something like

因为Foo在其中调用了一个字段dataMap。这里字段的名称不能被忽略，因为如果有多个地图，它会产生冲突Foo，比如

class Foo {
private Map<String, Data> dataMap1;
private Map<String, Data> dataMap2;
}

now without having the fieldName : in JSON, the JSON doesn't know how to deserialize when it gets some JSON like

现在没有 fieldName ：在 JSON 中，当它获得一些 JSON 时，JSON 不知道如何反序列化

{
    //belongs to dataMap1
    "key1": {
        "fieldOne": "some value",
        "fieldTwo": "some value"
    },
    "key2": {
        "fieldOne": "some value",
        "fieldTwo": "some value"
    },
    //belongs to dataMap2
    "key3": {
        "fieldOne": "some value",
        "fieldTwo": "some value"
    },
    "key4": {
        "fieldOne": "some other value",
        "fieldTwo": "some other value"
    }
}

Now having the fieldName makes it very clearwhile deserializing

现在有了 fieldName在反序列化时变得非常清楚

{
    "dataMap1" : {
    "key1": {
        "fieldOne": "some value",
        "fieldTwo": "some value"
    },
    "key2": {
        "fieldOne": "some value",
        "fieldTwo": "some value"
    }
    },
    "dataMap2" : {
    "key3": {
        "fieldOne": "some value",
        "fieldTwo": "some value"
    },
    "key4": {
        "fieldOne": "some other value",
        "fieldTwo": "some other value"
    }
  }
}

Having said that

话说回来

How to ignore dataMap layer in the json?

如何忽略json中的dataMap层？

You can just serialize the map

你可以序列化地图

ObjectMapper mapper = new ObjectMapper();
mapper.writeValueAsString(myFOOObject.getDataMap());

回答by Harmeet Singh Taara

In map there is two Objects Stringand Data. JSON convert the java objects into JSON key value pair , but if you already have a Map that contain key value pair, and convert that map into JSON document , then map key is also convert into JSON key value pair and Map value also have a object that convert into key value pair.

在地图中有两个对象String和Data。JSON 将 java 对象转换为 JSON 键值对，但是如果您已经有一个包含键值对的 Map，并将该映射转换为 JSON 文档，那么映射键也转换为 JSON 键值对并且 Map 值也有一个对象转换成键值对。

回答by T.Loner

I found answer - using @JsonAnyGetter annotation with getter for map. To avoid conflicts during deserialization should be used @JsonAnySetter annotation with setter for this map.

我找到了答案 - 使用 @JsonAnyGetter 注释和 getter 来获取地图。为避免在反序列化期间发生冲突，应为此映射使用带有 setter 的 @JsonAnySetter 注释。