Question

我刚刚按照新的（ish）Java 8时间包将许多日期转换为LocalDateTime。到目前为止，在开始尝试序列化和反序列化之前，我一直喜欢这种切换。

我如何配置Jackson以支持它们？：

LocalDateTime --serialize-> UTC时间戳--deserialize-> LocalDateTime？

这里有很多有关转换为格式化字符串的资料，但是我似乎找不到通用的utc时间戳解决方案。

Answer 1

您可以为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());
    }
}

CustomLocalDateTimeDesSerializer：

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()));
    }
}

Answer 2

以下解决方案解决了将LocalDateTime序列化/反序列化到时间戳的任务，并且至少与spring-boot v1.5有关，并且还包括了@xingbin的{{ 3}}：

如果有必要与java.util.Date具有相同的行为，则必须使用toInstant().toEpochMilli()代替toInstant().getEpochSecond()
检查null的值以反序列化
以及可选点：为Jackson ObjectMapper

时间戳序列化器类：

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();
        }
    }
}

时间戳解串器类：

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

您可以利用the JavaTimeModule来代替手动重写所有内容：

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

Answer 4

这里是简单有效的方法：

@JsonFormat(shape= JsonFormat.Shape.STRING, pattern="EEE MMM dd HH:mm:ss Z yyyy")
@JsonProperty("created_at") 
ZonedDateTime created_at;

这是一个问题的引号：Jackson deserialize date from Twitter to `ZonedDateTime`，因此这可能是重复的问题

Answer 5

添加 jackson-modules-java-8 依赖项：

<dependency>
   <groupId>com.fasterxml.jackson.datatype</groupId>
   <artifactId>jackson-datatype-jsr310</artifactId>
</dependency>

到您的项目，并将以下模块注册到ObjectMapper： JavaTimeModule

请参见description of JavaTimeModule以及相应的GitHub存储库jackson-modules-java-8

使用Jackson将Java8 LocalDateTime序列化为UTC时间戳

5 个答案: