修复 Jackson 无法构造 Java.time.LocalDate 的实例

Question

我正在尝试使用 Jackson csv Mapper 读取 csv 文件并将条目映射到具有 LocalDate 字段的 Pojo。尝试解析文件时出现以下错误

无法构造java.time.LocalDate 的实例（没有创作者，比如 默认构造，存在）：无字符串参数构造函数/工厂 从字符串值反序列化的方法（'2019-12-01'）\n [来源： (com.fasterxml.jackson.dataformat.csv.impl.UTF8Reader)

我已经尝试了其他答案中给出的方法，但仍然得到相同的结果，只有有效的注释是

@JsonDeserialize(使用 = LocalDateDeserializer.class)

我试图创建一个 Object Mapper 的 bean 并在我创建的应用程序配置文件中注册它的模块，但仍然没有效果。请有人帮助我

波乔

@Data
class TestImport{

@JsonProperty("start_date")
LocalDate startDate;
}

对象映射器配置：

 @Bean
    @Primary
    public ObjectMapper objectMapper(){
        ObjectMapper objectMapper=new ObjectMapper();
        objectMapper.registerModule(new JavaTimeModule());
        return objectMapper;
    }

文件读取代码：

public  <T> List<T> read(Class<T> Entity, MultipartFile file) throws Exception{
            InputStream inputStream = new BufferedInputStream(file.getInputStream());
            CsvSchema schema = csvMapper.schemaFor(Entity).withHeader().withColumnReordering(true);
            ObjectReader reader = csvMapper.readerFor(Entity).with(schema);
            List<T> result= reader.<T>readValues(inputStream).readAll();
            inputStream.close();
            return result;
    }

Pom.xml

 <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.2.2.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <dependencies>
        <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>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-actuator</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-jpa</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-redis</artifactId>
        </dependency>

        <dependency>
            <groupId>org.postgresql</groupId>
            <artifactId>postgresql</artifactId>
            <scope>runtime</scope>
        </dependency>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <optional>true</optional>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
            <exclusions>
                <exclusion>
                    <groupId>org.junit.vintage</groupId>
                    <artifactId>junit-vintage-engine</artifactId>
                </exclusion>
            </exclusions>
        </dependency>
        <dependency>
            <groupId>com.fasterxml.jackson.dataformat</groupId>
            <artifactId>jackson-dataformat-csv</artifactId>
            <version>2.10.1</version>
        </dependency>

        <!-- https://mvnrepository.com/artifact/io.github.millij/poi-object-mapper -->
        <dependency>
            <groupId>io.github.millij</groupId>
            <artifactId>poi-object-mapper</artifactId>
            <version>1.0.0</version>
        </dependency>
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>spring-web</artifactId>

        </dependency>
        <dependency>
            <groupId>redis.clients</groupId>
            <artifactId>jedis</artifactId>
            <version>2.8.1</version>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-redis</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <dependency>
            <groupId>org.apache.httpcomponents</groupId>
            <artifactId>httpclient</artifactId>
            <version>4.5.2</version>
        </dependency>
    </dependencies>

Answer 1

jackson-datatype-jsr310 在 Springs 自己的博客 Jackson-Modules Spring Blog 中所述的类路径上默认注册，因此根本无需在新的 ObjectMapper 中手动注册。

Answer 2

在你的 pojo 中你需要设置注解
@JsonFormat(shape = JsonFormat.Shape.STRING, pattern = "yyyy-MM-dd") 有关更多详细信息，请查看问题Spring Data JPA - ZonedDateTime format for json serialization 的答案