Spring Data Rest API使用UUID报错，求兼容解决方案

配置了如下实体类：

@Entity
@RestResource
public class Employee  {
    @Id
    @GeneratedValue
    @Type(type = "pg-uuid")
    private UUID id;

    @OneToMany(mappedBy = "employee")
    @RestResource(path = "projects", rel = "projects")
    private List<EmployeeToProject> projects;
}

@Entity
@RestResource
public class Project {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    @OneToMany(mappedBy = "project", cascade = CascadeType.ALL, orphanRemoval = true)
    @RestResource(path = "employees", rel = "employees")
    private List<EmployeeToProject> employees;
}

@Entity
@RestResource
public class EmployeeToProject {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    @ManyToOne
    @RestResource(path = "employee", rel = "employee")
    private Employee employee;

    @ManyToOne
    @RestResource(path = "project", rel = "project")
    private Project project;
}

并为EmployeeToProject配置了仓库：

@RepositoryRestResource
@CrossOrigin("*")
public interface EmployeeToProjectRepository extends PagingAndSortingRepository<EmployeeToProjectRepository, Long> {
    
}

注：仓库代码存在笔误，应将泛型参数改为EmployeeToProject而非EmployeeToProjectRepository，正确写法为：

@RepositoryRestResource
@CrossOrigin("*")
public interface EmployeeToProjectRepository extends PagingAndSortingRepository<EmployeeToProject, Long> {
    
}

调用Spring Data Rest的API创建employee_to_project记录时，抛出NumberFormatException，错误信息如下：

"message": "JSON parse error: Failed to convert from type [java.lang.String] to type [java.lang.Long] for value 'e21d6b85-371f-485d-ba5b-b807e2c79093'; nested exception is java.lang.NumberFormatException: For input string: \"e21d6b85-371f-485d-ba5b-b807e2c79093\"; nested exception is com.fasterxml.jackson.databind.JsonMappingException: Failed to convert from type [java.lang.String] to type [java.lang.Long] for value 'e21d6b85-371f-485d-ba5b-b807e2c79093'; nested exception is java.lang.NumberFormatException: For input string: \"e21d6b85-371f-485d-ba5b-b807e2c79093\"

将Employee的ID改为Long类型后API可正常工作，现需在保留UUID作为Employee ID的前提下，让API正常运行。

1. 修复仓库泛型笔误 #

先修正EmployeeToProjectRepository的泛型参数，确保第一个参数为EmployeeToProject，否则仓库无法正确关联实体类。

2. 配置Jackson支持UUID类型转换 #

Spring Data Rest依赖Jackson处理JSON序列化/反序列化，需确保Jackson能正确识别UUID类型：

方式一：添加依赖 #

如果使用Maven，在pom.xml中添加：

<dependency>
    <groupId>com.fasterxml.jackson.datatype</groupId>
    <artifactId>jackson-datatype-jdk8</artifactId>
</dependency>
<dependency>
    <groupId>com.fasterxml.jackson.datatype</groupId>
    <artifactId>jackson-datatype-uuid</artifactId>
</dependency>

如果使用Gradle，在build.gradle中添加：

implementation 'com.fasterxml.jackson.datatype:jackson-datatype-jdk8'
implementation 'com.fasterxml.jackson.datatype:jackson-datatype-uuid'

方式二：自定义配置类 #

创建配置类手动注册UUID模块：

import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.datatype.uuid.UUIDModule;
import org.springframework.context.annotation.Configuration;
import org.springframework.data.rest.webmvc.config.RepositoryRestConfigurer;

@Configuration
public class RestConfig implements RepositoryRestConfigurer {

    @Override
    public void configureJacksonObjectMapper(ObjectMapper objectMapper) {
        objectMapper.registerModule(new UUIDModule());
    }
}

3. 优化Employee实体ID注解 #

在Employee的ID字段上补充@JsonFormat注解，明确UUID的格式：

import com.fasterxml.jackson.annotation.JsonFormat;

// ...其他注解
@Id
@GeneratedValue
@Type(type = "pg-uuid")
@JsonFormat(shape = JsonFormat.Shape.STRING)
private UUID id;

4. 使用HAL规范的关联链接（推荐） #

Spring Data Rest遵循HAL规范，创建关联记录时，推荐传入实体的API链接而非直接传ID值，例如创建EmployeeToProject的请求体：

{
  "employee": "http://localhost:8080/employees/e21d6b85-371f-485d-ba5b-b807e2c79093",
  "project": "http://localhost:8080/projects/1"
}

这种方式能彻底避免ID类型转换问题，同时符合RESTful设计规范。

内容的提问来源于stack exchange，提问作者user09