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
<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();
其他回答
所有你需要知道的都在杰克逊文档里 https://www.baeldung.com/jackson-serialize-dates
9号广告很快为我解决了这个问题。
ObjectMapper mapper = new ObjectMapper();
mapper.registerModule(new JavaTimeModule());
mapper.disable(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS);
我在使用Spring boot时遇到了类似的问题。 使用Spring启动1.5.1。我所要做的就是添加依赖项:
<dependency>
<groupId>com.fasterxml.jackson.datatype</groupId>
<artifactId>jackson-datatype-jsr310</artifactId>
</dependency>
如果你正在使用Jackson Serializer,下面是一种使用date模块的方法:
import com.fasterxml.jackson.core.JsonProcessingException;
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.datatype.jdk8.Jdk8Module;
import com.fasterxml.jackson.datatype.jsr310.JavaTimeModule;
import com.fasterxml.jackson.module.paramnames.ParameterNamesModule;
import org.apache.kafka.common.serialization.Serializer;
public class JacksonSerializer<T> implements Serializer<T> {
private final ObjectMapper mapper = new ObjectMapper()
.registerModule(new ParameterNamesModule())
.registerModule(new Jdk8Module())
.registerModule(new JavaTimeModule());
@Override
public byte[] serialize(String s, T object) {
try {
return mapper.writeValueAsBytes(object);
} catch (JsonProcessingException e) {
e.printStackTrace();
}
return null;
}
}
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
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'