Spring Boot REST接口JSON序列化重复对象转ID问题解决

问题场景 #

我开发了一个返回List<Map<String,Object>>的Spring Boot REST接口，接口代码如下：

public List<Map<String,Object>> getAll(@Valid DataRequestDto dto)
{
    List<Map<String, Object>> data = (List<Map<String, Object>>) dataOperationMap.getAllData(dto);
    return data;
}

期望输出 #

期望所有列表项中的acckind和accbalance都显示完整对象：

{
        "id": 7581,
        "serialid": 24,
        "parentid": 7576,
        "rowno": 5,
        "code": "15005",
        "acckind": {
            "id": 10080001,
            "title": "بودجه ای",
            "systemDefine": 1,
            "typeValueId": 1,
            "isActive": true,
            "isDefault": true,
            "engTitle": ""
        },
        "accbalance": {
            "id": 10160001,
            "title": "خنثی و بدون کنترل",
            "systemDefine": 1,
            "typeValueId": 1,
            "isActive": true,
            "isDefault": true,
            "engTitle": null
        }
    },
    {
        "id": 7582,
        "serialid": 24,
        "parentid": 7576,
        "rowno": 6,
        "code": "15006",
        "acckind": {
            "id": 10080001,
            "title": "بودجه ای",
            "systemDefine": 1,
            "typeValueId": 1,
            "isActive": true,
            "isDefault": true,
            "engTitle": ""
        },
        "accbalance": {
            "id": 10160001,
            "title": "خنثی و بدون کنترل",
            "systemDefine": 1,
            "typeValueId": 1,
            "isActive": true,
            "isDefault": true,
            "engTitle": null
        }
    }

实际输出 #

实际JSON中从第二个数据开始，acckind和accbalance仅显示ID：

{
        "id": 7581,
        "serialid": 24,
        "parentid": 7576,
        "rowno": 5,
        "code": "15005",
        "acckind": {
            "id": 10080001,
            "title": "بودجه ای",
            "systemDefine": 1,
            "typeValueId": 1,
            "isActive": true,
            "isDefault": true,
            "engTitle": ""
        },
        "accbalance": {
            "id": 10160001,
            "title": "خنثی و بدون کنترل",
            "systemDefine": 1,
            "typeValueId": 1,
            "isActive": true,
            "isDefault": true,
            "engTitle": null
        }
    },
    {
        "id": 7582,
        "serialid": 24,
        "parentid": 7576,
        "rowno": 6,
        "code": "15006",
        "acckind": 10080001,
        "accbalance": 10160001
    }

排查信息 #

• 调试确认接口返回前数据是完整的，问题出在JSON转换环节
• 项目使用Spring Boot 2.3.6.RELEASE，pom.xml配置如下：

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.3.6.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.hushaerp</groupId>
    <artifactId>form-manager</artifactId>
    <version>1.0-RELEASE</version>
    <name>form-manager</name>
    <description>Demo project for Spring Boot</description>

    <properties>
        <java.version>1.8</java.version>
        <spring-cloud.version>Hoxton.SR9</spring-cloud.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-validation</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-web</artifactId>
        </dependency>
<!--        <dependency>-->
<!--            <groupId>org.springframework.cloud</groupId>-->
<!--            <artifactId>spring-cloud-starter-config</artifactId>-->
<!--        </dependency>-->
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-openfeign</artifactId>
        </dependency>
        <dependency>
            <groupId>org.modelmapper</groupId>
            <artifactId>modelmapper</artifactId>
            <version>3.1.0</version>
        </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.cloud</groupId>
            <artifactId>spring-cloud-starter-oauth2</artifactId>
        </dependency>

        <dependency>
            <groupId>io.springfox</groupId>
            <artifactId>springfox-swagger2</artifactId>
            <version>2.9.2</version>
        </dependency>

        <dependency>
            <groupId>io.springfox</groupId>
            <artifactId>springfox-swagger-ui</artifactId>
            <version>2.9.2</version>
        </dependency>

    </dependencies>

    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-dependencies</artifactId>
                <version>${spring-cloud.version}</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

</project>

原因分析 #

这个问题由Jackson的对象引用检测机制导致：当同一个对象被多次引用时，Jackson默认会在第一次序列化时输出完整对象，后续引用仅输出对象标识（ID），以此优化序列化性能。同时，使用Map<String, Object>作为返回类型会丢失类型信息，Jackson无法明确重复对象的序列化规则，进一步触发该问题。

解决方案 #

方法1：禁用Jackson对象引用检测 #

通过配置关闭Jackson的引用检测逻辑，强制序列化所有重复对象：

代码配置方式

import com.fasterxml.jackson.databind.ObjectMapper;
import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;

@Configuration
public class JacksonConfig {
    @Bean
    public ObjectMapper objectMapper() {
        ObjectMapper mapper = new ObjectMapper();
        // 关闭引用检测，强制序列化所有重复对象
        mapper.disable(com.fasterxml.jackson.databind.SerializationFeature.USE_ID_FOR_REFERENCE);
        mapper.disable(com.fasterxml.jackson.databind.MapperFeature.USE_ANNOTATIONS);
        return mapper;
    }
}

配置文件方式

在application.properties中添加：

spring.jackson.serialization.use-id-for-reference=never
spring.jackson.mapper.use-annotations=false

方法2：使用具体DTO类替代Map #

创建明确的DTO类，避免Map的类型模糊问题，这也是最规范的长期解决方案：

import lombok.Data;
import java.util.List;
import java.util.stream.Collectors;
import org.modelmapper.ModelMapper;

@Data
public class DataItemDto {
    private Long id;
    private Integer serialid;
    private Long parentid;
    private Integer rowno;
    private String code;
    private AccKindDto acckind;
    private AccBalanceDto accbalance;

    @Data
    public static class AccKindDto {
        private Long id;
        private String title;
        private Integer systemDefine;
        private Integer typeValueId;
        private Boolean isActive;
        private Boolean isDefault;
        private String engTitle;
    }

    @Data
    public static class AccBalanceDto {
        private Long id;
        private String title;
        private Integer systemDefine;
        private Integer typeValueId;
        private Boolean isActive;
        private Boolean isDefault;
        private String engTitle;
    }
}

修改接口返回类型：

public List<DataItemDto> getAll(@Valid DataRequestDto dto) {
    List<Map<String, Object>> dataMap = (List<Map<String, Object>>) dataOperationMap.getAllData(dto);
    ModelMapper modelMapper = new ModelMapper();
    return dataMap.stream()
            .map(map -> modelMapper.map(map, DataItemDto.class))
            .collect(Collectors.toList());
}

方法3：序列化前深拷贝重复对象 #

如果无法修改返回类型，可在返回前对重复的关联对象进行深拷贝，确保每个Map中的对象都是独立实例：

import org.springframework.beans.BeanUtils;

public List<Map<String,Object>> getAll(@Valid DataRequestDto dto) {
    List<Map<String, Object>> data = (List<Map<String, Object>>) dataOperationMap.getAllData(dto);
    for (Map<String, Object> item : data) {
        // 深拷贝acckind对象
        Object accKind = item.get("acckind");
        if (accKind != null) {
            AccKind newAccKind = new AccKind();
            BeanUtils.copyProperties(accKind, newAccKind);
            item.put("acckind", newAccKind);
        }
        // 深拷贝accbalance对象
        Object accBalance = item.get("accbalance");
        if (accBalance != null) {
            AccBalance newAccBalance = new AccBalance();
            BeanUtils.copyProperties(accBalance, newAccBalance);
            item.put("accbalance", newAccBalance);
        }
    }
    return data;
}

内容的提问来源于stack exchange，提问作者F Goli