使用 Jackson 在 Java 中 @JsonView 註解的重要性?


JsonView 註解 可在序列化和反序列化過程中動態包含/排除屬性。我們需要配置一個 ObjectMapper 類來包含用於透過 writerWithView() 方法從 Java 物件編寫 JSON 的檢視型別。

語法

@Target(value={ANNOTATION_TYPE,METHOD,FIELD})
@Retention(value=RUNTIME)
public @interface JsonView

示例

import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.annotation.JsonProperty;
import com.fasterxml.jackson.annotation.JsonView;
import com.fasterxml.jackson.core.JsonProcessingException;
public class JsonViewAnnotationTest {
   public static void main(String args[]) throws JsonProcessingException {
      ObjectMapper objectMapper = new ObjectMapper();
      String jsonString = objectMapper.writerWithView(Views.Public.class).writeValueAsString(new Person());
      String jsonStringInternal = objectMapper.writerWithView(Views.Internal.class).writeValueAsString(new Person());
      System.out.println(jsonString);
      System.out.println(jsonStringInternal);
   }
}
// Person class
class Person {
   @JsonView(Views.Public.class)
   public long personId = 115;
   @JsonView(Views.Public.class)
   public String personName = "Raja Ramesh";
   @JsonView(Views.Internal.class)
   public String gender = "male";
   @Override
   public String toString() {
      return "Person{" +
             "personId=" + personId +
             ", personName='" + personName + '\'' +
             ", gender='" + gender + '\'' +
       '}';
   }
}
class Views {
   static class Public {}
   static class Internal extends Public {}
}

輸出

{"personId":115,"personName":"Raja Ramesh"}
{"personId":115,"personName":"Raja Ramesh","gender":"male"}

更新於:2020-07-08

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