Spring Boot没有使用Jackson Kotlin插件

Posted 2021-04-20

我不能强迫Spring为Jackson使用Kotlin模块。问题是Jackson无法将JSON解析为数据类。

//Exception
2018-02-23 13:29:09.046 ERROR 24730 --- [nio-9300-exec-1] o.a.c.c.C.[.[.[.[dispatcherServlet]      : Servlet.service() for servlet [dispatcherServlet] in context with path [/services] threw exception [Request processing failed; nested exception is org.springframework.beans.BeanInstantiationException: Failed to instantiate [*.model.User]: Constructor threw exception; nested exception is java.lang.IllegalArgumentException: Parameter specified as non-null is null: method *.model.User.<init>, parameter name] with root cause
java.lang.IllegalArgumentException: Parameter specified as non-null is null: method *.User.<init>, parameter name

//JSON
{
    "name": "name",
    "surname": "surname",
    "email": "email",
    "password": "pswd"
}

//Model
@Entity
@Table
data class User(
        @Id
        @GeneratedValue(strategy = GenerationType.AUTO)
        var userId: Long?,
        var name: String,
        var surname: String,
        var email: String,
        var password: String,
        (...)
        ): Resource() {
        (...)
}

我试图配置杰克逊，但它没有多大帮助。有什么奇怪的，在我配置ObjectMapper的@Bean方法中，一切正常。此外，当我为非可空字段添加默认值时，它们不会被覆盖。

@Configuration
class JacksonConfig {
    @Bean
    fun mappingJackson2HttpMessageConverter(): MappingJackson2HttpMessageConverter {
        val mapper = ObjectMapper().registerKotlinModule()
        mapper.configure(SerializationFeature.FAIL_ON_EMPTY_BEANS, false)
        var user = mapper.readValue<User>("{
" +
                "	"name": "name",
" +
                "	"surname": "surname",
" +
                "	"email": "email",
" +
                "	"password": "pswd"
" +
                "}")
        return MappingJackson2HttpMessageConverter(mapper)
    }
}

可能重要的是模型与应用程序本身在不同的项目中。

Kotlin版本是1.20杰克逊依赖：

    <dependency>
        <groupId>com.fasterxml.jackson.core</groupId>
        <artifactId>jackson-core</artifactId>
        <version>${jackson.version}</version> <!--2.9.4-->
    </dependency>
    <dependency>
        <groupId>com.fasterxml.jackson.core</groupId>
        <artifactId>jackson-annotations</artifactId>
        <version>${jackson.version}</version>
    </dependency>
    <dependency>
        <groupId>com.fasterxml.jackson.core</groupId>
        <artifactId>jackson-databind</artifactId>
        <version>${jackson.version}</version>
    </dependency>
    <dependency>
        <groupId>com.fasterxml.jackson.module</groupId>
        <artifactId>jackson-module-kotlin</artifactId>
        <version>${jackson.version}</version>
    </dependency>

我现在尝试的是：

All of these answers

Similiar problem but probably different case anyway

还有一些其他的，不值得注意的。

答案

我是愚蠢的，认真的。

我的结构如下：

abstract class AbstractController (...) {
    fun save(@RequestMapping entity: T) {
    (...)
}

并启用它我用过

class DeriveredController (...) {
    @PostMapping
    override fun save(entity: Derivered) {
    (...)
    }
}

问题在于派生函数中缺少@RequestMapping。