java - 为什么 Spring boot "failed to lazily initialize a collection of role"使用 Eager fetch 类型得到解决？

Question

我正在编写一个简单的 Spring 启动应用程序。

对于身份验证部分，我正在实现自定义 UserDetails。当我向登录端点发出请求时，出现此异常:

身份验证失败:无法延迟初始化角色集合:com.boot.cut_costs.config.security.CustomUserDetails.roles，无法初始化代理 - 无 session

CustomUserDetails.java

@Entity
@Table(name="ACCOUNT_USER")
public class CustomUserDetails implements UserDetails {

    private static final long serialVersionUID = 1L;

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name = "USER_ID")
    private long id;

    @NotBlank
    @Column(name = "USERNAME")
    private String username;

    @NotBlank
    @Column(name = "PASSWORD")
    private String password;

    @Column(name = "LOCKED")
    private boolean locked;

    @ManyToMany(cascade=CascadeType.ALL)
    @JoinTable(name = "USER_ROLE", 
                joinColumns = @JoinColumn(name = "USER_ID"), 
                inverseJoinColumns = @JoinColumn(name = "ROLE_ID"))
    private Set<CustomRole> roles;

    public CustomUserDetails(String username, String password, boolean enabled, boolean accountNonExpired, boolean credentialsNonExpired, boolean accountNonLocked, Collection<GrantedAuthority> authorities) { // jpa only
        this.setUsername(username);
        this.setPassword(password);
        this.roles = new HashSet<CustomRole>();
        for (GrantedAuthority authority: authorities) {
            roles.add(new CustomRole(authority.getAuthority()));
        }
    }

    public CustomUserDetails() { // jpa only
    }

    @Override
    public String getPassword() {
        return password;
    }

    public void setPassword(String password) {
        this.password = password;
    }

    @Override
    public String getUsername() {
        return username;
    }

    public void setUsername(String username) {
        this.username = username;
    }

    public Set<CustomRole> getRoles() {
        return roles;
    }

    public void setRoles(Set<CustomRole> roles) {
        this.roles = roles;
    }

    @Override
    public Collection<GrantedAuthority> getAuthorities() {
        ArrayList<String> authoritiesList = new ArrayList<String>();
        for (CustomRole role: roles) {
            authoritiesList.add(role.getRole());
        }
        return AuthorityUtils.commaSeparatedStringToAuthorityList(String.join(",", authoritiesList));
    }
    //Some more getters and setters ...

}

CustomRole.java

@Entity
@Table(name="ACCOUNT_ROLE")
public class CustomRole {

    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    @Column(name="ROLE_ID")
    private long id;

    @Column(name="ROLE")
    private String role;

    public long getId() {
        return id;
    }

    //delete if not necessary
    public void setId(long id) {
        this.id = id;
    }

    public String getRole() {
        return role;
    }

    public void setRole(String role) {
        this.role = role;
    }

    public CustomRole() {} //for jpa

    public CustomRole(String role) {
        this.role = role;
    }
}

当我在 ManyToMany 注释中设置获取类型 Eager 时，它起作用了。

我在 SO 中读到这不是一个好的做法。首先，我想知道为什么？其次，我想知道什么是好的做法？我在这里混合服务层和 DAO 吗？

Answer 1

当你使用 Lazy 时，你会加载没有角色的用户，角色只会在你使用它们时收费

这里你使用了spring security，当你调用CustomUserDetails时，你应该把Eager加载所有角色，在一般情况下使用 Eager 不是一个好的做法，因为您加载了许多不需要的细节