使用Jackson将Java8 LocalDateTime序列化为UTC时间戳

Question

我刚刚根据新的（ish）Java8时间包将许多日期转换为LocalDateTime。到目前为止，我一直很喜欢这种转换，直到我开始尝试序列化和反序列化。

如何配置Jackson以支持他们？：

LocalDateTime --serialize--

这里有大量关于转换为格式化字符串的资料，但我似乎找不到utc时间戳的现成解决方案。

Answer 1

您可以利用< code>JavaTimeModule，而不是手动重写所有内容:

ObjectMapper om = new ObjectMapper();
om.registerModule(new JavaTimeModule());
om.configure(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS, true);

Answer 2

以下解决方案解决了将＜code＞LocalDateTime＜/code＞序列化/反序列化为时间戳的任务，并且至少与spring boot v1.5相关，还包括@xingbin的回答中未考虑的下一点：

• 如果需要具有与＜code＞java.util相同的行为。日期必须使用toInstant（）。toEpochMilli（）而不是toInstant（）。getEpochSecond（）
• 检查null要反序列化的值
• 可选点：为Jackson＜code＞ObjectMapper＜/code＞指定此序列化/反序列化配置

时间戳序列化程序类:

public class LocalDateTimeSerializer extends StdSerializer<LocalDateTime> {
    private static final ZoneId DEFAULT_ZONE_ID = ZoneId.of("UTC");

    public LocalDateTimeSerializer() {
        super(LocalDateTime.class);

    }

    @Override
    public void serialize(final LocalDateTime value,
                          final JsonGenerator generator,
                          final SerializerProvider provider) throws IOException {
        if (value != null) {
            final long mills = value.atZone(DEFAULT_ZONE_ID).toInstant().toEpochMilli();
            generator.writeNumber(mills);
        } else {
            generator.writeNull();
        }
    }
}

时间戳反序列化程序类：

public class LocalDateTimeDeserializer extends StdDeserializer<LocalDateTime> {
    private static final ZoneId DEFAULT_ZONE_ID = ZoneId.of("UTC");

    public LocalDateTimeDeserializer() {
        super(LocalDateTime.class);
    }

    @Override
    public LocalDateTime deserialize(final JsonParser parser,
                                     final DeserializationContext context) throws IOException {
        final long value = parser.getValueAsLong();
        return LocalDateTime.ofInstant(Instant.ofEpochMilli(value), DEFAULT_ZONE_ID);
    }
}

对象映射器配置：

@Configuration
public class ObjectMapperConfiguration {
    @Bean
    public ObjectMapper objectMapper() {
        final ObjectMapper objectMapper = new ObjectMapper();
        final SimpleModule module = new SimpleModule();
        module.addSerializer(LocalDateTime.class, new LocalDateTimeSerializer());
        module.addDeserializer(LocalDateTime.class, new LocalDateTimeDeserializer());
        objectMapper.registerModule(module);
        return objectMapper;
    }
}

Answer 3

您可以为< code>LocalDateTime自定义序列化程序和反序列化程序，例如:

CustomLocalDateTimeSerializer

import com.fasterxml.jackson.core.JsonGenerator;
import com.fasterxml.jackson.databind.SerializerProvider;
import com.fasterxml.jackson.databind.ser.std.StdSerializer;

import java.io.IOException;
import java.time.LocalDateTime;
import java.time.ZoneId;

public class CustomLocalDateTimeSerializer extends StdSerializer<LocalDateTime> {

    protected CustomLocalDateTimeSerializer(Class<LocalDateTime> t) {
        super(t);
    }

    protected CustomLocalDateTimeSerializer() {
        this(null);
    }

    @Override
    public void serialize(LocalDateTime value, JsonGenerator gen, SerializerProvider sp)
            throws IOException {
        Long epoch = value.atZone(ZoneId.systemDefault()).toInstant().getEpochSecond();
        gen.writeString(epoch.toString());
    }
}

CustomLocalDateTimeDeserializer：

import com.fasterxml.jackson.core.JsonParser;
import com.fasterxml.jackson.databind.DeserializationContext;
import com.fasterxml.jackson.databind.deser.std.StdDeserializer;

import java.io.IOException;
import java.time.Instant;
import java.time.LocalDateTime;
import java.time.ZoneId;

class CustomLocalDateTimeDesSerializer extends StdDeserializer<LocalDateTime> {

    protected CustomLocalDateTimeDesSerializer() {
        this(null);
    }

    protected CustomLocalDateTimeDesSerializer(Class<LocalDateTime> t) {
        super(t);
    }

    @Override
    public LocalDateTime deserialize(JsonParser jsonparser, DeserializationContext context)
            throws IOException {
        Long timestamp = Long.parseLong(jsonparser.getText());
        return LocalDateTime.ofInstant(Instant.ofEpochSecond(timestamp), ZoneId.systemDefault());
    }
}

并使用它们：

import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.annotation.JsonDeserialize;
import com.fasterxml.jackson.databind.annotation.JsonSerialize;
import com.fasterxml.jackson.datatype.jsr310.JavaTimeModule;

import java.time.LocalDateTime;

public class RestObject {

    private LocalDateTime timestamp = LocalDateTime.now();

    @JsonSerialize(using = CustomLocalDateTimeSerializer.class)
    @JsonDeserialize(using = CustomLocalDateTimeDesSerializer.class)
    public LocalDateTime getTimestamp() {
        return timestamp;
    }

    public static void main(String[] args) throws Exception {
        ObjectMapper objectMapper = new ObjectMapper();
        // {"timestamp":"1549026058"}
        System.out.println(objectMapper.writeValueAsString(new RestObject()));
    }
}