Spring Boot内存Map实现CRUD接口返回200但无数据求助

Spring Boot应用能正常启动，也能保存记录，但通过REST Controller执行CRUD操作时，从内存Map获取记录会返回200 OK响应却无数据内容，不过/hello接口可正常返回"Hello World"。确认Controller类的对象注入无问题，恳请提供排查思路，相关代码如下：

主应用类 #

@ComponentScan("com.someone.organization")
@SpringBootApplication
public class WorkingOrganizationApplication {

    public static void main(String[] args) {
        SpringApplication.run(WorkingOrganizationApplication.class, args);

        @SuppressWarnings("resource")
        AnnotationConfigApplicationContext context = new AnnotationConfigApplicationContext();
        context.scan("com.someone.organization");
        context.refresh();

        
        EmployeeRepository empRepository = context.getBean(EmployeeRepository.class);
         //testing the store method
        empRepository.save(new Employee(1L, "XYZ","PQR"));
        empRepository.save(new Employee(2L, "ABC","PQR"));
        empRepository.save(new Employee(3L, "MNC","PQR"));


        Employee employee = empRepository.findById(1L);
        System.out.println(employee.toString());
  

        Employee employee2 = empRepository.findById(2L);
        System.out.println(employee2.toString());
        // close the spring context
        context.close();
    
    }

}

Entity类 #

public class Employee {

    private Long Employee_Id;

    @Override
    public String toString() {
        return "Employee{" +
                "Employee_Id=" + Employee_Id +
                ", Employee_first_name='" + Employee_first_name + '\'' +
                ", Employee_last_name='" + Employee_last_name + '\'' +
                '}';
    }

    private String Employee_first_name;

    private String Employee_last_name;


    public Long getEmployeeId() {
        return Employee_Id;
    }

    public void setEmployee_Id(Long employee_Id) {
        Employee_Id = employee_Id;
    }

    public String getEmployee_first_name() {
        return Employee_first_name;
    }

    public void setEmployee_first_name(String employee_first_name) {
        Employee_first_name = employee_first_name;
    }

    public String getEmployee_last_name() {
        return Employee_last_name;
    }

    public void setEmployee_last_name(String employee_last_name) {
        Employee_last_name = employee_last_name;
    }

    public Employee(Long employee_Id, String employee_first_name, String employee_last_name) {

        this.Employee_Id = employee_Id;

        this.Employee_first_name = employee_first_name;
        this.Employee_last_name = employee_last_name;
    }


}

数据仓库接口 #

public interface OrganizationRepository<T> {

      // Save method
      void save(T entity);

      // Find a employee by its id
      Employee findById(Long id);


      //public List<Employee> findAllEmployees();

}

仓库实现类 #

@Repository
public class EmployeeRepository implements OrganizationRepository<Employee> {

    private final Map<Long, Employee> repository;

    public EmployeeRepository() {
        this.repository = new HashMap<>();
    }

    @Override
    public void save(Employee employee) {

        // repository.put(id, employee);
        repository.put(employee.getEmployeeId(), employee);

    }

    @Override
    public Employee findById(Long id) {

        Employee employeeOutput = null;
        if (repository.containsKey(id)) {
            employeeOutput = repository.get(id);
        }

        return employeeOutput;
    }

    
}

Controller类 #

@RestController
public class EmployeeController {

    @Autowired
    private EmployeeRepository  employeeRepository;

    @PostMapping("/employees")
    public Employee createEmployee(@RequestBody Employee employee) {
         employeeRepository.save(employee);
         return  employee;
    }

    @GetMapping("/employees/findbyid/{id}")
    public Employee getEmployee(@PathVariable Long id) {

      
      return employeeRepository.findById(id);
        
    }

    @GetMapping("/hello")
    public String hello() {
        return "Hello, World!";
    }
}

排查建议 #

• 仓库实例不共享：主应用类中手动创建的AnnotationConfigApplicationContext和Spring Boot启动的主上下文完全独立，你手动初始化的数据存储在这个独立上下文的仓库实例中，而Controller注入的是主上下文的仓库实例，两者无关联。删除手动创建上下文的代码，改用CommandLineRunner在主上下文初始化数据：

  @SpringBootApplication
  @ComponentScan("com.someone.organization")
  public class WorkingOrganizationApplication implements CommandLineRunner {
  
      @Autowired
      private EmployeeRepository empRepository;
  
      public static void main(String[] args) {
          SpringApplication.run(WorkingOrganizationApplication.class, args);
      }
  
      @Override
      public void run(String... args) throws Exception {
          empRepository.save(new Employee(1L, "XYZ","PQR"));
          empRepository.save(new Employee(2L, "ABC","PQR"));
          empRepository.save(new Employee(3L, "MNC","PQR"));
  
          System.out.println(empRepository.findById(1L));
          System.out.println(empRepository.findById(2L));
      }
  }
  

• 实体类序列化异常：Employee类的属性名与getter/setter命名不符合JavaBean规范（比如属性Employee_Id对应gettergetEmployeeId()，缺少下划线），导致JSON序列化工具无法正确识别字段，返回空对象。解决方式二选一：
  1. 将属性名改为小驼峰格式（employeeId、employeeFirstName、employeeLastName），同步修改对应的getter/setter使其符合规范；
  2. 保留原属性名，添加@JsonProperty注解指定序列化字段名：

     @JsonProperty("Employee_Id")
     private Long Employee_Id;
     
     @JsonProperty("Employee_Id")
     public Long getEmployeeId() {
         return Employee_Id;
     }
     
     @JsonProperty("Employee_Id")
     public void setEmployee_Id(Long employee_Id) {
         Employee_Id = employee_Id;
     }
     

• 空值响应处理：findById方法找不到数据时返回null，Controller直接返回null会导致响应体为空，建议改用ResponseEntity返回明确状态：

  @GetMapping("/employees/findbyid/{id}")
  public ResponseEntity<Employee> getEmployee(@PathVariable Long id) {
      Employee employee = employeeRepository.findById(id);
      return employee != null ? ResponseEntity.ok(employee) : ResponseEntity.notFound().build();
  }
  

• 实例一致性验证：在Controller和初始化代码中打印仓库实例的哈希值，确认是否为同一个对象：

  // Controller中
  System.out.println("Controller仓库实例哈希：" + employeeRepository.hashCode());
  
  // 初始化代码中
  System.out.println("初始化仓库实例哈希：" + empRepository.hashCode());
  

内容的提问来源于stack exchange，提问作者crcr