杰克逊的JsonIgnore [英] Jackson's JsonIgnore

问题描述

JsonIgnore注释似乎对我不起作用。任何想法为什么？

JsonIgnore annotation doesn't seem to work for me. Any ideas why?

public class JsonTest implements Serializable {

    @JsonIgnore
private static JsonTest instance = null;

@JsonIgnore
private transient Set<String> set = new CopyOnWriteArraySet<String>();

private JsonTest() {}

@JsonIgnore
public static JsonTest getInstance() {
    if (instance == null)
        instance = new JsonTest();
    return instance;
}

public void setSet(Set<String> set) {
    this.set = set;
}

@JsonIgnore
public Set<String> getSet() {
    return set;
}

public String toString() {
    ObjectMapper mapper = new ObjectMapper();
    mapper.configure(SerializationConfig.Feature.FAIL_ON_EMPTY_BEANS, false);
    try {
        return mapper.writeValueAsString(this);
    } catch (Exception e) {
        e.printStackTrace();
        return null;
    }
}

public static void main(String[] args) {
    HashSet<String> set = new HashSet<String>();
    set.add("test");
    JsonTest.getInstance().setSet(set);
    System.out.println(JsonTest.getInstance().toString());
}

}

输出：{set：[test]}

Output: {"set":["test"]}

推荐答案

瞬态意味着该字段不会被序列化。你不需要在那里添加@JsonIgnore注释，因为无论如何都会排除该字段。

Transient means that that field will not be serialized. You do not need to add @JsonIgnore annotation there because of that field will be excluded anyway.

你至少可以在org.codehaus.jackson中找到@JsonIgnore注释：jackson -mapper-asl：1.9.13和com.fasterxml.jackson.core：jackson-annotations：2.4.3（这是我使用的）。 ObjectMapper在jackson-mapper-asl工件中。这里有趣的部分是，如果我使用来自jackson-annotations的@JsonIgnore（com.fasterxml.jackson.annotation.JsonIgnore） - 即使我将ObjectMapper配置为仅使用属性，它也不起作用（'set'响应） 。可能它是fastxml实现中的一个错误，但我没有找到它。

You can locate @JsonIgnore annotation at least in org.codehaus.jackson:jackson-mapper-asl:1.9.13 and com.fasterxml.jackson.core:jackson-annotations:2.4.3 (this is what I used). Where ObjectMapper is in jackson-mapper-asl artifact. The interesting part here is that if I use @JsonIgnore from jackson-annotations (com.fasterxml.jackson.annotation.JsonIgnore) -- it doesn't work ('set' is in response) even if I configure ObjectMapper to use only properties. Probably it is a bug in fasterxml implementation but I didn't find it.

所以，如果你使用codehaus而不是更快的xx（我添加配置到仅使用字段）：

So, it is working fine if you will use codehaus rather then fasterxml (I added configuration to use only fields):

import org.codehaus.jackson.annotate.JsonAutoDetect;
import org.codehaus.jackson.annotate.JsonIgnore;
import org.codehaus.jackson.map.ObjectMapper;
import org.codehaus.jackson.map.SerializationConfig;

import java.io.Serializable;
import java.util.HashSet;
import java.util.Set;
import java.util.concurrent.CopyOnWriteArraySet;

public class JsonTest implements Serializable {
    @JsonIgnore
    private static JsonTest instance = null;

    private transient Set<String> set = new CopyOnWriteArraySet<String>();

    private JsonTest() {}

    @JsonIgnore
    public static JsonTest getInstance() {
        if (instance == null)
            instance = new JsonTest();
        return instance;
    }

    public void setSet(Set<String> set) {
        this.set = set;
    }

    @JsonIgnore
    public Set<String> getSet() {
        return set;
    }

    public String toString() {
        ObjectMapper mapper = new ObjectMapper();
        mapper.configure(SerializationConfig.Feature.FAIL_ON_EMPTY_BEANS, false);
        mapper.setVisibilityChecker(mapper.getSerializationConfig().getDefaultVisibilityChecker()
                .withFieldVisibility(JsonAutoDetect.Visibility.ANY)
                .withGetterVisibility(JsonAutoDetect.Visibility.NONE)
                .withSetterVisibility(JsonAutoDetect.Visibility.NONE)
                .withCreatorVisibility(JsonAutoDetect.Visibility.NONE));
        try {
            return mapper.writeValueAsString(this);
        } catch (Exception e) {
            e.printStackTrace();
            return null;
        }
    }

    public static void main(String[] args) {
        HashSet<String> set = new HashSet<String>();
        set.add("test");
        JsonTest.getInstance().setSet(set);
        System.out.println(JsonTest.getInstance().toString());
    }
}

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