java - Jackson json 映射和驼峰键名称

Question

我想通过 jackson 库将 json 转换为包含 camelCase 键的 map ...比如说...

来自

{
    "SomeKey": "SomeValue",
    "AnotherKey": "another value",
    "InnerJson" : {"TheKey" : "TheValue"}
}

为此...

{
    "someKey": "SomeValue",
    "anotherKey": "another value",
    "innerJson" : {"theKey" : "TheValue"}
}

我的代码...

public Map<String, Object> jsonToMap(String jsonString) throws IOException
{
    ObjectMapper mapper=new ObjectMapper();
    mapper.setPropertyNamingStrategy(PropertyNamingStrategy.CAMEL_CASE_TO_LOWER_CASE_WITH_UNDERSCORES);
    return mapper.readValue(jsonString,new TypeReference<Map<String, Object>>(){});
}

但是这行不通...甚至其他propertyNamingStrategy在json上也行不通...比如...

{
    "someKey": "SomeValue"
}

mapper.setPropertyNamingStrategy(new PropertyNamingStrategy.PascalCaseStrategy())

到

{
    "SomeKey": "SomeValue"
}

如何通过 jackson 获取 camelCase Map key 名称...或者我应该手动循环 map 并转换 key 还是有其他方法？？？

提前致谢...

Answer 1

当您使用 map /字典而不是将 JSON 数据绑定(bind)到 POJO(与 JSON 数据匹配的显式 Java 类)时，属性命名策略不适用:

Class PropertyNamingStrategy ... defines how names of JSON properties ("external names") are derived from names of POJO methods and fields ("internal names")

因此，您必须先使用 Jackson 解析数据，然后遍历结果并转换 key 。

像这样更改您的代码:

public Map<String, Object> jsonToMap(String jsonString) throws IOException
{
    ObjectMapper mapper=new ObjectMapper();
    mapper.setPropertyNamingStrategy(PropertyNamingStrategy.CAMEL_CASE_TO_LOWER_CASE_WITH_UNDERSCORES);
    Map<String, Object> map = mapper.readValue(jsonString,new TypeReference<Map<String, Object>>(){});
    return convertMap(map);
}

并添加这些方法:

public String mapKey(String key) {
    return Character.toLowerCase(key.charAt(0)) + key.substring(1);
}

public Map<String, Object> convertMap(Map<String, Object> map) {
    Map<String, Object> result = new HashMap<String, Object>();
    for (Map.Entry<String, Object> entry : map.entrySet()) {
        String key = entry.getKey();
        Object value = entry.getValue();
        result.put(mapKey(key), convertValue(value));
    }
    return result;
}

public convertList(Lst<Object> list) {
    List<Object> result = new ArrayList<Object>();
    for (Object obj : list) {
        result.add(convertValue(obj));
    }
    return result;
}

public Object covertValue(Object obj) {
    if (obj instanceof Map<String, Object>) {
        return convertMap((Map<String, Object>) obj);
    } else if (obj instanceof List<Object>) {
        return convertList((List<Object>) obj);
    } else {
        return obj;
    }
}