java - Jackson MRBean 不工作，无法构造实例

Question

我有这个代码:

ObjectMapper objectMapper = new ObjectMapper();
objectMapper.registerModule(new JavaTimeModule());
objectMapper.registerModule(new MrBeanModule());

这个测试用例:

SearchResultContainer src = objectMapper.readValue("{}", SearchResultContainer.class);

SearchResultContainer 是一个 POJO 接口(interface)(这就是此处使用 MRBean 的全部原因)。

为什么会失败并出现以下异常？

com.fasterxml.jackson.databind.exc.InvalidDefinitionException: Cannot construct instance of `com.ctc.rets.dto.search.SearchResultContainer` (no Creators, like default construct, exist): abstract types either need to be mapped to concrete types, have custom deserializer, or contain additional type information
 at [Source: (String)"{}"; line: 1, column: 1]
    at com.fasterxml.jackson.databind.exc.InvalidDefinitionException.from(InvalidDefinitionException.java:67)
    at com.fasterxml.jackson.databind.DeserializationContext.reportBadDefinition(DeserializationContext.java:1451)
    at com.fasterxml.jackson.databind.DeserializationContext.handleMissingInstantiator(DeserializationContext.java:1027)
    at com.fasterxml.jackson.databind.deser.AbstractDeserializer.deserialize(AbstractDeserializer.java:265)
    at com.fasterxml.jackson.databind.ObjectMapper._readMapAndClose(ObjectMapper.java:4001)
    at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:2992)
    at com.ctc.web.client.CustomRestTemplateTest.test1(CustomRestTemplateTest.java:25)

Answer 1

在 pom.xml 中发现 MRBean 版本不正确。

修复:

<!-- https://mvnrepository.com/artifact/com.fasterxml.jackson.module/jackson-module-mrbean -->
<dependency>
    <groupId>com.fasterxml.jackson.module</groupId>
    <artifactId>jackson-module-mrbean</artifactId>
    <version>2.9.8</version>
</dependency>