@JsonSerialize无法正常工作 [英] @JsonSerialize not working

问题描述

在Spring / Hibernate项目中，在我的实体类中我有：

In Spring/Hibernate project, in my entity class I have:

package klab.finance.main.entity;

import com.fasterxml.jackson.annotation.JsonIgnoreProperties;
import com.fasterxml.jackson.databind.annotation.JsonDeserialize;
import com.fasterxml.jackson.databind.annotation.JsonSerialize;
import klab.backend.entity.postgres.base.BaseEntity;
import klab.backend.utils.DateTimeUtils;
import klab.backend.utils.JsonDateTime;
import klab.backend.utils.json.LocalDateTimeToTimestampDeserializer;
import klab.backend.utils.json.TimestampToLocalDateTimeSerializer;
import org.hibernate.annotations.Where;
import org.joda.time.LocalDateTime;

import javax.persistence.*;
import java.util.HashSet;
import java.util.Set;

@Entity
@Table(name="transactions")
@JsonIgnoreProperties(ignoreUnknown = true)
public class Transaction extends BaseEntity {

    private Long bankTransactionDate;

    @Column(name="bank_transaction_date")
    @JsonSerialize(using = TimestampToLocalDateTimeSerializer.class)
    public Long getBankTransactionDate(){
        return bankTransactionDate;
    }

    @JsonDeserialize(using = LocalDateTimeToTimestampDeserializer.class)
    public void setBankTransactionDate(Long bankTransactionDate){
        this.bankTransactionDate=bankTransactionDate;
    }
}

我的序列化程序类：

package klab.backend.utils.json;

import com.fasterxml.jackson.core.JsonGenerator;
import com.fasterxml.jackson.databind.JsonSerializer;
import com.fasterxml.jackson.databind.SerializerProvider;
import klab.backend.entity.postgres.base.BaseEntity;
import klab.backend.utils.DateTimeUtils;
import org.joda.time.LocalDateTime;

import java.io.IOException;

public class TimestampToLocalDateTimeSerializer extends JsonSerializer<Long> {

    @Override
    public void serialize(Long value, JsonGenerator jsonGenerator, SerializerProvider serializerProvider)
            throws IOException {

        jsonGenerator.writeString("blabla");
    }
}

我希望用bank_transaction_date：blabla。

相反，我用bank_transaction_date得到它：null 。我还注意到，如果我在序列化程序中设置断点，调试器永远不会停在那里，所以可能没有使用它。

Instead, I get it with "bank_transaction_date": null. I also notice, that if I set a breakpoint in my serializer, debugger is never stopping there, so it is probably not used.

怎么了？

推荐答案

答案很简单： bankTransactionDate null ，事实证明， null 值序列化器未被调用:)

The answer was very simple: bankTransactionDate was null, and it turns out, that for null values serializer is not called :)

一旦我用数据库填充数据库，序列化器开始工作并给了我bank_transaction_date：blabla。

Once I filled database with values, serializer started to work and gave me "bank_transaction_date": "blabla".

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