我如何使用杰克逊JSON映射与Java 8 LocalDateTime?
jsonmappingexception:不能实例化类型[简单类型,java.time类]的值。LocalDateTime] from JSON字符串;没有单字符串构造函数/工厂方法(通过引用链:MyDTO["field1"]->SubDTO["date"])
我如何使用杰克逊JSON映射与Java 8 LocalDateTime?
jsonmappingexception:不能实例化类型[简单类型,java.time类]的值。LocalDateTime] from JSON字符串;没有单字符串构造函数/工厂方法(通过引用链:MyDTO["field1"]->SubDTO["date"])
当前回答
更新:由于历史原因,留下这个答案,但我不建议这样做。请参阅上面接受的答案。
告诉Jackson使用自定义的[反]序列化类进行映射:
@JsonSerialize(using = LocalDateTimeSerializer.class)
@JsonDeserialize(using = LocalDateTimeDeserializer.class)
private LocalDateTime ignoreUntil;
提供自定义类:
public class LocalDateTimeSerializer extends JsonSerializer<LocalDateTime> {
@Override
public void serialize(LocalDateTime arg0, JsonGenerator arg1, SerializerProvider arg2) throws IOException {
arg1.writeString(arg0.toString());
}
}
public class LocalDateTimeDeserializer extends JsonDeserializer<LocalDateTime> {
@Override
public LocalDateTime deserialize(JsonParser arg0, DeserializationContext arg1) throws IOException {
return LocalDateTime.parse(arg0.getText());
}
}
随机事实:如果我在类上面嵌套并且不使它们静态,错误消息是奇怪的: httpmediatypenotsupportedexception:内容类型'application/json;charset=UTF-8'不支持
其他回答
对于那些正在寻找ES-8和Spring Boot:3.0版本的解决方案的人
创建一个扩展ElasticsearchConfiguration的配置文件,并覆盖clientConfiguration和elasticsearchClient的创建。
在创建elasticsearchClient期间,注入您自己的配置为使用Java 8时间模块的objectMapper,它将覆盖默认的objectMapper。
@Override
public ClientConfiguration clientConfiguration() {
return ClientConfiguration.builder()
.connectedTo(<Hostname> +":"+ <Port>)
.usingSsl()
.withBasicAuth(<Username>, <Password>)
.build();
}
@Override
public ElasticsearchClient elasticsearchClient(RestClient restClient) {
Assert.notNull(restClient, "restClient must not be null");
//Create Java8 time module
JavaTimeModule module = new JavaTimeModule();
module.addSerializer(new LocalDateTimeSerializer(DateTimeFormatter.ofPattern(DateFormat.date_time_no_millis.getPattern())));
//Register the module with objectMapper
ObjectMapper objectMapper=new ObjectMapper()
.registerModule(module);
//To convert datetime to ISO-8601
objectMapper.disable(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS);
//Creating our own jsonpMapper
JsonpMapper jsonpMapper=new JacksonJsonpMapper(objectMapper);
// Create the transport with a Jackson mapper
ElasticsearchTransport transport = new RestClientTransport(
restClient, jsonpMapper);
// And create the API client
return new ElasticsearchClient(transport);
}
Maven的依赖:
<dependency>
<groupId>com.fasterxml.jackson.datatype</groupId>
<artifactId>jackson-datatype-jsr310</artifactId>
<version>2.14.0</version>
</dependency>
您可以在应用程序中设置此参数。yml文件解析即时时间,即java8中的Date API:
spring.jackson.serialization.write-dates-as-timestamps=false
我使用这个时间格式:"{birthDate": "2018-05-24T13:56:13Z}"从json反序列化为java.time.Instant(见截图)
对于使用Spring Boot 2.x的用户
上面这些都不需要做——Java 8 LocalDateTime是开箱即用的序列化/反序列化。我必须在1年内完成以上所有工作。x,但是使用Boot 2。X,它可以无缝工作。
在Spring Boot中也可以看到JSON Java 8 LocalDateTime格式
这只是一个例子,如何使用它在一个单元测试,我黑调试这个问题。 关键成分是
mapper。registerModule(从新JavaTimeModule (); <artifactId>jack -datatyp -jsr310</artifactId>的maven dependency
代码:
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.datatype.jsr310.JavaTimeModule;
import org.testng.Assert;
import org.testng.annotations.Test;
import java.io.IOException;
import java.io.Serializable;
import java.time.Instant;
class Mumu implements Serializable {
private Instant from;
private String text;
Mumu(Instant from, String text) {
this.from = from;
this.text = text;
}
public Mumu() {
}
public Instant getFrom() {
return from;
}
public String getText() {
return text;
}
@Override
public String toString() {
return "Mumu{" +
"from=" + from +
", text='" + text + '\'' +
'}';
}
}
public class Scratch {
@Test
public void JacksonInstant() throws IOException {
ObjectMapper mapper = new ObjectMapper();
mapper.registerModule(new JavaTimeModule());
Mumu before = new Mumu(Instant.now(), "before");
String jsonInString = mapper.writeValueAsString(before);
System.out.println("-- BEFORE --");
System.out.println(before);
System.out.println(jsonInString);
Mumu after = mapper.readValue(jsonInString, Mumu.class);
System.out.println("-- AFTER --");
System.out.println(after);
Assert.assertEquals(after.toString(), before.toString());
}
}