如何用Jackson實現動態部分JSON序列化？

Question

我有一個POJO，其中包含用於跟蹤屬性是否已顯式設置的所有屬性的自定義setter方法。 setter存儲到fieldNameSet布爾字段，並為這些標志公開isFieldNameSet getter。 我希望Jackson只使用isFieldNameSet為true字段動態地序列化類。

背景：

我開始編寫一個自定義的JsonFilter實現，但它沒有給出當前正在序列化的對象實例的任何上下文，所以顯然我無法讀取isFieldNameSet屬性的當前值。

Answer 1

從傑克遜的例子中快速入侵

import org.codehaus.jackson.JsonGenerationException;
import org.codehaus.jackson.map.JsonMappingException;
import org.codehaus.jackson.map.ObjectMapper;
import org.codehaus.jackson.map.ser.FilterProvider;
import org.codehaus.jackson.map.ser.impl.SimpleBeanPropertyFilter;
import org.codehaus.jackson.map.ser.impl.SimpleFilterProvider;

public class JacksonExample {
    public static void main(String[] args) {

        ObjectMapper mapper = new ObjectMapper();

        User user = createDummyUser();

        try {

            //Its age here , this is conditional based on your fieldset
            SimpleBeanPropertyFilter theFilter = SimpleBeanPropertyFilter.serializeAllExcept("age");
            FilterProvider filters = new SimpleFilterProvider().addFilter("myFilter", theFilter);

            // Convert object to JSON string
            String jsonInString = jsonInString = mapper.writer(filters).writeValueAsString(user);
            System.out.println(jsonInString);

            // Convert object to JSON string and pretty print

            //System.out.println(jsonInString);

        } catch (JsonGenerationException e) {
            e.printStackTrace();
        } catch (JsonMappingException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }

    }

    private static User createDummyUser() {

        User user = new User();

        user.setName("mkyong");
        user.setAge(33);

        List<String> msg = new ArrayList<>();
        msg.add("hello jackson 1");
        msg.add("hello jackson 2");
        msg.add("hello jackson 3");

        user.setMessages(msg);

        return user;

    }
}


package org.soproject;

import java.util.List;

import org.codehaus.jackson.map.annotate.JsonFilter;

@JsonFilter("myFilter")
public class User {

    private String name;
    private int age;
    private List<String> messages;

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }

    public int getAge() {
        return age;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public List<String> getMessages() {
        return messages;
    }

    public void setMessages(List<String> messages) {
        this.messages = messages;
    }

    // getters and setters

}

如您所見，忽略年齡：

{“name”：“mkyong”，“messages”：[“hello jackson 1”，“hello jackson 2”，“hello jackson 3”]}

注意傑克遜源來自： https ： //www.mkyong.com/java/how-to-convert-java-object-to-from-json-jackson/