Feign使用JPA分页类Page和Pageable抛出序列化异常

╰+攻爆jí腚メ 2022-11-17 14:50 375阅读 0赞

##### 一、异常如下 #####

feign.AsyncResponseHandler.decode(AsyncResponseHandler.java:119) 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: (ByteArrayInputStream); line: 1, column: 40] (through reference chain: com.emily.framework.common.base.BaseResponse["data"])

解决这个异常很简单，只需配置如下配置就可以解决：

# feign相关配置
    feign:
      # Feign org.springframework.data.domain.Page编码和解码
      # Feign org.springframework.data.domain.Sort编码解码
      autoconfiguration:
        jackson:
          # 如果为true，则将提供PageJacksonModule、SortJacksonModule用jackson对Page进行编码和解码操作，默认：false
          enabled: true

##### 二、org.springframework.cloud.openfeign.FeignAutoConfiguration.FeignJacksonConfiguration自动化配置类 #####

@Configuration(proxyBeanMethods = false)
    	@ConditionalOnClass({  Module.class, Page.class, Sort.class })
    	@ConditionalOnProperty(value = "feign.autoconfiguration.jackson.enabled", havingValue = "true")
    	protected static class FeignJacksonConfiguration { 
    
    		@Bean
    		@ConditionalOnMissingBean(PageJacksonModule.class)
    		public PageJacksonModule pageJacksonModule() { 
    			return new PageJacksonModule();
    		}
    
    		@Bean
    		@ConditionalOnMissingBean(SortJacksonModule.class)
    		public SortJacksonModule sortModule() { 
    			return new SortJacksonModule();
    		}
    
    	}

开启feign.autoconfiguration.jackson.enabled配置就可以向容器中注入PageJacksonModule、SortJacksonModule两个对JPA分页类的序列化和反序列化操作能力；

##### 三、org.springframework.data.domain.Pageable、org.springframework.data.domain.Page两个分页实现类是在JPA相关实现的pom包中，具体是在如下包： #####

<dependency>
                <groupId>org.springframework.data</groupId>
                <artifactId>spring-data-commons</artifactId>
                <version>2.4.6</version>
            </dependency>

Page类的序列化结果是这样的：

"content": [
                { 
                    "name": "emily",
                    "weight": "10"
                }
            ],
            "number": 1,
            "size": 3,
            "totalElements": 10,
            "numberOfElements": 10,
            "first": false,
            "last": false,
            "totalPages": 4,
            "hasContent": true,
            "pageable": { 
                "sort": [],
                "offset": 3,
                "pageNumber": 1,
                "pageSize": 3,
                "paged": true,
                "unpaged": false
            },
            "empty": false
        }

> 这样的返回结果对于底层库来说是很有帮助的，但是在实际的开发过程中感觉用处不大，无用的字段太多了；

GitHub地址：[https://github.com/mingyang66/spring-parent][https_github.com_mingyang66_spring-parent]

[https_github.com_mingyang66_spring-parent]: https://github.com/mingyang66/spring-parent