我有一个像这样的Java类,想要使用Jackson转换为JSON。谢谢你的帮助。
public class myClass {
String Id;
Map<String, Object> optionalData = new LinkedHashMap<String, Object>();
}
例如,假设optionalData
是一个地图,可以保存两个条目<"type", "book">
和<"year", "2014">
我希望输出如下。请注意,optionalData的键/值可以随时更改(因此,我无法使用Map创建&#34;静态&#34; Java对象)
[
{
id: "book-id1",
type: "book",
year: "2014"
},
{
id: "book-id2",
type: "book",
year: "2013"
}
]
答案 0 :(得分:2)
您可以在getter方法上使用@JsonAnyGetter
注释,该方法返回可选值的映射。请参阅详细解释的this blog plost。
以下是一个例子:
public class JacksonAnyGetter {
public static class myClass {
final String Id;
private final Map<String, Object> optionalData = new LinkedHashMap<>();
public myClass(String id, String key1, Object value1, String key2, Object value2) {
Id = id;
optionalData.put(key1, value1);
optionalData.put(key2, value2);
}
public String getid() {
return Id;
}
@JsonAnyGetter
public Map<String, Object> getOptionalData() {
return optionalData;
}
}
public static void main(String[] args) throws JsonProcessingException {
ObjectMapper mapper = new ObjectMapper();
List<myClass> objects = Arrays.asList(
new myClass("book-id1", "type", "book", "year", 2013),
new myClass("book-id2", "type", "book", "year", 2014)
);
System.out.println(mapper.writerWithDefaultPrettyPrinter().writeValueAsString(objects));
}
}
输出:
[ {
"id" : "book-id1",
"type" : "book",
"year" : 2013
}, {
"id" : "book-id2",
"type" : "book",
"year" : 2014
} ]
答案 1 :(得分:1)
您需要编写自己的Jackson JsonSerializer
以根据需要从Java对象创建自定义JSON字符串。
以下是不错的帖子以及示例
以下是一些例子
以下是使用GSON Serialiser
List<MyClass> list = new ArrayList<MyClass>();
MyClass myClass1 = new MyClass();
myClass1.setId("book-id1");
myClass1.getOptionalData().put("type", "book");
myClass1.getOptionalData().put("year", "2014");
list.add(myClass1);
MyClass myClass2 = new MyClass();
myClass2.setId("book-id2");
myClass2.getOptionalData().put("type", "book");
myClass2.getOptionalData().put("year", "2013");
list.add(myClass2);
class MyClassSerialiser implements JsonSerializer<MyClass> {
@Override
public JsonElement serialize(final MyClass obj, final Type typeOfSrc,
final JsonSerializationContext context) {
final JsonObject jsonObject = new JsonObject();
jsonObject.addProperty("id", obj.getId());
Map<String, String> optioanlData = obj.getOptionalData();
if (optioanlData.size() > 0) {
for (Map.Entry<String, String> entry : optioanlData.entrySet()) {
jsonObject.addProperty(entry.getKey(), entry.getValue());
}
}
return jsonObject;
}
}
String jsonString = new GsonBuilder().setPrettyPrinting().
.registerTypeAdapter(MyClass.class, new MyClassSerialiser()).create()
.toJson(list);
System.out.println(jsonString);
输出:
[
{
"id": "book-id1",
"type": "book",
"year": "2014"
},
{
"id": "book-id2",
"type": "book",
"year": "2013"
}
]