com.fasterxml.jackson.databind.exc.InvalidDefinitionException: Cannot construct instance of `org.springframework.data.domain.Page`

问题描述

关键的信息就是抛出了一个异常InvalidDefinitionException，不能构建springdata的一个Page对象，没有默认构造器。

3:49:21.788 [http-nio-8083-exec-7] ERROR org.apache.catalina.core.ContainerBase.[Tomcat].[localhost].[/].[dispatcherServlet] - Servlet.service() for servlet [dispatcherServlet] in context with path [] threw exception [Request processing failed; nested exception is org.springframework.http.converter.HttpMessageConversionException: Type definition error: [simple type, class org.springframework.data.domain.Page]; nested exception is com.fasterxml.jackson.databind.exc.InvalidDefinitionException: Cannot construct instance of `org.springframework.data.domain.Page` (no Creators, like default constructor, exist): abstract types either need to be mapped to concrete types, have custom deserializer, or contain additional type information
at [Source: (PushbackInputStream); line: 1, column: 1]] with root cause
com.fasterxml.jackson.databind.exc.InvalidDefinitionException: Cannot construct instance of `org.springframework.data.domain.Page` (no Creators, like default constructor, exist): abstract types either need to be mapped to concrete types, have custom deserializer, or contain additional type information
at [Source: (PushbackInputStream); line: 1, column: 1]
at com.fasterxml.jackson.databind.exc.InvalidDefinitionException.from(InvalidDefinitionException.java:67) ~[jackson-databind-2.12.5.jar:2.12.5]
at com.fasterxml.jackson.databind.DeserializationContext.reportBadDefinition(DeserializationContext.java:1764) ~[jackson-databind-2.12.5.jar:2.12.5]
at com.fasterxml.jackson.databind.DatabindContext.reportBadDefinition(DatabindContext.java:400) ~[jackson-databind-2.12.5.jar:2.12.5]
at com.fasterxml.jackson.databind.DeserializationContext.handleMissingInstantiator(DeserializationContext.java:1209) ~[jackson-databind-2.12.5.jar:2.12.5]
at com.fasterxml.jackson.databind.deser.AbstractDeserializer.deserialize(AbstractDeserializer.java:274) ~[jackson-databind-2.12.5.jar:2.12.5]
at com.fasterxml.jackson.databind.deser.DefaultDeserializationContext.readRootValue(DefaultDeserializationContext.java:322) ~[jackson-databind-2.12.5.jar:2.12.5]
at com.fasterxml.jackson.databind.ObjectMapper._readMapAndClose(ObjectMapper.java:4593) ~[jackson-databind-2.12.5.jar:2.12.5]
at com.fasterxml.jackson.databind.ObjectMapper.readValue(ObjectMapper.java:3601) ~[jackson-databind-2.12.5.jar:2.12.5]
at org.springframework.http.converter.json.AbstractJackson2HttpMessageConverter.readJavaType(AbstractJackson2HttpMessageConverter.java:378) ~[spring-web-5.3.10.jar:5.3.10]
at org.springframework.http.converter.json.AbstractJackson2HttpMessageConverter.read(AbstractJackson2HttpMessageConverter.java:342) ~[spring-web-5.3.10.jar:5.3.10]
at org.springframework.web.client.HttpMessageConverterExtractor.extractData(HttpMessageConverterExtractor.java:105) ~[spring-web-5.3.10.jar:5.3.10]
at org.springframework.web.client.RestTemplate.doExecute(RestTemplate.java:778) ~[spring-web-5.3.10.jar:5.3.10]
at org.springframework.web.client.RestTemplate.execute(RestTemplate.java:711) ~[spring-web-5.3.10.jar:5.3.10]
at org.springframework.web.client.RestTemplate.getForObject(RestTemplate.java:334) ~[spring-web-5.3.10.jar:5.3.10]
at io.majing.admin.web.NotebookContentRest.getAllLoginContent(NotebookContentRest.java:38) ~[classes/:?]
at jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[?:?]
at jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[?:?]

异常信息如上所示：

问题分析

jackson这个库在序列化和反序列化的时候需要无参构造器，而spring中Page接口的实现类PageImpl没有无参构造器，所以报错。

RestTemplate在调用的时候，返回的是分页数据是不能够被序列化的，因此报出了这个异常。

知道了问题的原因，那么解决方案自然就有了。

解决方案

处理这个问题的一个思路是自己实现一个Page的接口，具体的代码如下

public class PageImpl<T> extends org.springframework.data.domain.PageImpl<T> {

    @JsonCreator(mode = JsonCreator.Mode.PROPERTIES)
    public PageImpl(@JsonProperty("content") List<T> content,
                    @JsonProperty("number") int number,
                    @JsonProperty("size") int size,
                    @JsonProperty("totalElements") Long totalElements,
                    @JsonProperty("pageable") JsonNode pageable,
                    @JsonProperty("last") boolean last,
                    @JsonProperty("totalPages") int totalPages,
                    @JsonProperty("sort") JsonNode sort,
                    @JsonProperty("first") boolean first,
                    @JsonProperty("numberOfElements") int numberOfElements) {

        super(content, PageRequest.of(number, size), totalElements);
    }

    public PageImpl(List<T> content, Pageable pageable, long total) {
        super(content, pageable, total);
    }

    public PageImpl(List<T> content) {
        super(content);
    }

    public PageImpl() {
        super(new ArrayList<>());
    }
}

注意，这个实现类在被调用方和调用方都要实现，因此，如果遇到此类问题，可以考虑将这个类抽象到一个公共的模块去。