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
如果有人在使用SpringBoot时遇到问题,这里是我在不添加新的依赖项的情况下修复问题的方法。
在Spring 2.1.3中,Jackson期望在此yyyy-MM-dd HH:mm:ss中出现日期字符串2019-05-21T07:37:11.000。在LocalDateTime中反序列化SSS格式。确保日期字符串用T分隔日期和时间,而不是用空格。秒(ss)和毫秒(SSS)可以省略。
@JsonProperty("last_charge_date")
public LocalDateTime lastChargeDate;
其他回答
<dependency>
<groupId>com.fasterxml.jackson.module</groupId>
<artifactId>jackson-module-parameter-names</artifactId>
</dependency>
<dependency>
<groupId>com.fasterxml.jackson.datatype</groupId>
<artifactId>jackson-datatype-jdk8</artifactId>
</dependency>
<dependency>
<groupId>com.fasterxml.jackson.datatype</groupId>
<artifactId>jackson-datatype-jsr310</artifactId>
</dependency>
添加这些依赖项并启用这些模块。这应该会有帮助
private static final ObjectMapper mapper = new ObjectMapper().findAndRegisterModules();
如果你因为任何原因不能使用jackson-modules-java8,你可以(反)序列化即时字段,只要使用@JsonIgnore和@JsonGetter和@JsonSetter:
public class MyBean {
private Instant time = Instant.now();
@JsonIgnore
public Instant getTime() {
return this.time;
}
public void setTime(Instant time) {
this.time = time;
}
@JsonGetter
private long getEpochTime() {
return this.time.toEpochMilli();
}
@JsonSetter
private void setEpochTime(long time) {
this.time = Instant.ofEpochMilli(time);
}
}
例子:
@Test
public void testJsonTime() throws Exception {
String json = new ObjectMapper().writeValueAsString(new MyBean());
System.out.println(json);
MyBean myBean = new ObjectMapper().readValue(json, MyBean.class);
System.out.println(myBean.getTime());
}
收益率
{"epochTime":1506432517242}
2017-09-26T13:28:37.242Z
@JsonDeserialize(using = LocalDateTimeDeserializer.class)
@JsonSerialize(using = LocalDateTimeSerializer.class)
private LocalDateTime createTime;
这对我来说很有效。
对于spring引导api:
@Configuration
public class JsonConfig {
@Bean
public MappingJackson2HttpMessageConverter mappingJackson2HttpMessageConverter() {
MappingJackson2HttpMessageConverter jsonConverter = new MappingJackson2HttpMessageConverter();
ObjectMapper mapper = new ObjectMapper();
mapper.registerModule(new ParameterNamesModule())
.registerModule(new Jdk8Module())
.registerModule(new JavaTimeModule());
mapper.setSerializationInclusion(JsonInclude.Include.NON_NULL);// will remove value properties
mapper.configure(DeserializationFeature.FAIL_ON_UNKNOWN_PROPERTIES, false);
jsonConverter.setObjectMapper(mapper);
return jsonConverter;
}
}
导入以下依赖项:
implementation 'com.fasterxml.jackson.core:jackson-core:2.13.0'
implementation 'com.fasterxml.jackson.core:jackson-databind:2.13.0'
implementation 'com.fasterxml.jackson.datatype:jackson-datatype-jsr310:2.13.0'
如果你正在使用Jersey,那么你需要像其他人建议的那样添加Maven依赖项(jackson- dattype -jsr310),并像这样注册你的对象映射器实例:
@Provider
public class JacksonObjectMapper implements ContextResolver<ObjectMapper> {
final ObjectMapper defaultObjectMapper;
public JacksonObjectMapper() {
defaultObjectMapper = createDefaultMapper();
}
@Override
public ObjectMapper getContext(Class<?> type) {
return defaultObjectMapper;
}
private static ObjectMapper createDefaultMapper() {
final ObjectMapper mapper = new ObjectMapper();
mapper.registerModule(new JavaTimeModule());
return mapper;
}
}
当在你的资源中注册Jackson时,你需要像这样添加这个映射器:
final ResourceConfig rc = new ResourceConfig().packages("<your package>");
rc
.register(JacksonObjectMapper.class)
.register(JacksonJaxbJsonProvider.class);