Spring Data JPA：在关联实体集合中高效筛选枚举值

import jakarta.persistence.*;
import org.hibernate.validator.constraints.Length;
import java.util.Set;

@Entity
@Table(name = "employees")
public class EmployeeEntity {
    @Id
    @Column(name = "id")
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long id;

    @Length(min = 2, max = 30)
    @Column(name = "name")
    private String name;

    @Length(min = 2, max = 30)
    @Column(name = "last_name")
    private String lastName;

    @Column(name = "email", nullable = false, unique = true)
    @Length(max = 50)
    private String email;

    @OneToMany(cascade = CascadeType.ALL, fetch = FetchType.EAGER)
    @JoinColumn(name = "employee_id")
    private Set<EmployeeRoleEntity> roles;

    // Getters and Setters
    public Long getId() { return id; }
    public void setId(Long id) { this.id = id; }
    public String getName() { return name; }
    public void setName(String name) { this.name = name; }
    public String getLastName() { return lastName; }
    public void setLastName(String lastName) { this.lastName = lastName; }
    public String getEmail() { return email; }
    public void setEmail(String email) { this.email = email; }
    public Set<EmployeeRoleEntity> getRoles() { return roles; }
    public void setRoles(Set<EmployeeRoleEntity> roles) { this.roles = roles; }
}

import jakarta.persistence.*;
import jakarta.validation.constraints.NotNull;
import lombok.EqualsAndHashCode;
import lombok.ToString;

@Entity
@Table(name = "employee_roles")
public class EmployeeRoleEntity {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "id")
    private Long id;

    @NotNull
    @Column(name = "role_name")
    @Enumerated(EnumType.STRING) // 关键：枚举以字符串形式存储
    private RoleEntityEnum role;

    @ManyToOne
    @JoinColumn(name = "employee_id")
    @ToString.Exclude
    @EqualsAndHashCode.Exclude
    private EmployeeEntity employee;

    // Getters and Setters
    public Long getId() { return id; }
    public void setId(Long id) { this.id = id; }
    public RoleEntityEnum getRole() { return role; }
    public void setRole(RoleEntityEnum role) { this.role = role; }
    public EmployeeEntity getEmployee() { return employee; }
    public void setEmployee(EmployeeEntity employee) { this.employee = employee; }
}

public enum RoleEntityEnum {
    ADMIN,
    USER,
    GUEST,
    MANAGER
}

public interface EmployeeRepository extends JpaRepository<EmployeeEntity, Long> {
    // 尝试一：这种方法无法正常工作
    List<EmployeeEntity> findByRoles_RoleContainingIgnoreCase(String role);
}

import org.springframework.data.jpa.repository.JpaRepository;
import java.util.List;

public interface EmployeeRepository extends JpaRepository<EmployeeEntity, Long> {
    /**
     * 根据关联的 EmployeeRoleEntity 集合中的 role 枚举值筛选员工。
     * Spring Data JPA 会自动处理集合遍历和枚举值的精确匹配。
     *
     * @param role 要筛选的枚举角色
     * @return 拥有指定角色的员工列表
     */
    List<EmployeeEntity> findByRoles_Role(RoleEntityEnum role);
}

import org.springframework.stereotype.Service;
import java.util.List;

@Service
public class EmployeeService {

    private final EmployeeRepository employeeRepository;

    public EmployeeService(EmployeeRepository employeeRepository) {
        this.employeeRepository = employeeRepository;
    }

    /**
     * 获取所有拥有指定角色的员工。
     *
     * @param targetRole 要查询的角色枚举
     * @return 拥有该角色的员工列表
     */
    public List<EmployeeEntity> getEmployeesByRole(RoleEntityEnum targetRole) {
        return employeeRepository.findByRoles_Role(targetRole);
    }

    // 示例：如何使用
    public void exampleUsage() {
        List<EmployeeEntity> admins = getEmployeesByRole(RoleEntityEnum.ADMIN);
        System.out.println("Admins: " + admins.size());

        List<EmployeeEntity> users = getEmployeesByRole(RoleEntityEnum.USER);
        System.out.println("Users: " + users.size());
    }
}