java - 使用 Jackson "Unexpected token (START_OBJECT), expected VALUE_STRING: Expected array or string."使用 LocalDateTime 将 JSON 解析为 POJO

Question

我在这里阅读了很多关于将 JSON 解析为 Java 对象的帖子，在我引入 LocalDateTime 之前，我的解析工作正常。我曾尝试使用 Java 8 解析器、JSR310 模块并构建自定义 - 下面描述了每个方面的障碍。任何帮助将不胜感激!

这是我的 JSON 字符串，由 Jackson 从另一个 POJO 创建:

{"validEscortsWTheirSpecReqs":"MAYBE",
 "modifiedDateTimeNeedToBeThere":     
    {"dayOfMonth":6,"dayOfWeek":"MONDAY","month":"FEBRUARY","year":2017,
     "hour":10,"minute":1,"second":24,"nano":0,"dayOfYear":37,"monthValue":2,
     "chronology":{"id":"ISO","calendarType":"iso8601"}
    }
}

产生

com.fasterxml.jackson.databind.JsonMappingException: Unexpected token (START_OBJECT), expected VALUE_STRING: Expected array or string. at 
...
    at com.fasterxml.jackson.databind.JsonMappingException.from(JsonMappingException.java:270)
    at com.fasterxml.jackson.databind.DeserializationContext.wrongTokenException(DeserializationContext.java:1376)
    at com.fasterxml.jackson.datatype.jsr310.deser.LocalDateTimeDeserializer.deserialize(LocalDateTimeDeserializer.java:118)
    at com.fasterxml.jackson.datatype.jsr310.deser.LocalDateTimeDeserializer.deserialize(LocalDateTimeDeserializer.java:39)
...

调用自:

ComputeArrive response = mapper.readValue(responseString, ComputeArrive.class);

响应有以下字段:

Logger 记录器//不应该被 JSON 映射，没有 getters/settersstatic final long serialVersionUID = 1L;//"String validEscortsWTheirSpecReqs = "YES"//想要映射LocalDateTime modifiedDateTimeNeedToBeThere//想要映射

我现在可能已经注册了太多模块，添加它们以尝试让它解析:

    mapper.findAndRegisterModules();
    //mapper           .registerModule(new ParameterNamesModule());
    mapper.registerModule(new Jdk8Module());
    mapper.registerModule(new JavaTimeModule());
    mapper.registerModule(new JSR310Module());

所以我尝试将 Spring Boot 依赖项添加到我的项目中并为 JSR310 编写定制程序(考虑到上述模块，这似乎是不必要的):

@Configuration
public class JacksonConfig {

    @Bean
    @Primary
    public ObjectMapper objectMapper(Jackson2ObjectMapperBuilder builder) {
        ObjectMapper objectMapper = builder.createXmlMapper(false).build();
        objectMapper.configure(SerializationFeature.WRITE_DATES_AS_TIMESTAMPS, false);
        objectMapper.configure(SerializationFeature.WRITE_DATE_TIMESTAMPS_AS_NANOSECONDS, false);
        return objectMapper;
    }
}

我的应用程序有很多依赖项，所以我不想让任何东西成为它的“父”，并添加了以下依赖项。但是，未找到“Jackson2ObjectMapperBuilder”类，因此上述内容无法使用这些依赖项进行编译:

<dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-core</artifactId>
    <version>4.3.5.RELEASE</version>
</dependency>
<dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-web</artifactId>
    <version>4.3.5.RELEASE</version>
</dependency>
<dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-beans</artifactId>
    <version>4.3.5.RELEASE</version>
</dependency>
<dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-context</artifactId>
    <version>4.3.5.RELEASE</version>
</dependency>
<dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-expression</artifactId>
    <version>4.3.5.RELEASE</version>
</dependency>
<dependency>
    <groupId>org.springframework</groupId>
    <artifactId>spring-aop</artifactId>
    <version>4.3.5.RELEASE</version>
</dependency>
<dependency>
    <groupId>aopalliance</groupId>
    <artifactId>aopalliance</artifactId>
    <version>1.0</version>
</dependency>   

我没有找到很多关于“Jackson2ObjectMapperBuilderCustomizer”的文档，它可能是“Jackson2ObjectMapperBuilder”的替代品——这可能是问题所在。请注意，上面的类不是我实例化的，因为我假设 Spring 实例化了它。

如有任何关于如何解析我的回复的想法，我们将不胜感激!

Answer 1

对我来说，这个问题是通过将 JavaTimeModule 添加到 Jackson2ObjectMapperBuilder 中解决的，如下所示:

@Configuration
public class MyConfiguration {

    @Bean
    @Primary
    public Jackson2ObjectMapperBuilder objectMapperBuilder() {
        Jackson2ObjectMapperBuilder builder = new Jackson2ObjectMapperBuilder();
        return builder.modulesToInstall(new JavaTimeModule());
    }

}

然后 Spring 将此映射器与已注册的模块一起使用。