Spring 映射需要引导域 class table
Spring boot domain class required for mapping table
我是 Spring Boot 的新手。我有一个 table(团队),它有资源,我存储在一个单独的 table(资源)中,并且有 team_resource 映射 table(带有字段 teamid、resourceid)。我的问题是我也应该为 mapping_table 设置一个域 class 吗?
当我插入具有资源的新团队 (POST) 时,我在所有 3 个 table 中创建条目。我正在使用 facade/dao 模式写入/读取数据库。当团队被修改/删除时,我必须处理。 mapping_table 我应该有一个域 class 吗?
有多种方法可以处理它
方法一
像这样在您的团队和资源实体之间定义@ManyToMany
:
在团队实体中
@ManyToMany(fetch = FetchType.LAZY,
cascade = {
CascadeType.PERSIST,
CascadeType.MERGE
})
@JoinTable(name = "resources",
joinColumns = { @JoinColumn(name = "id") },
inverseJoinColumns = { @JoinColumn(name = "id") })
private Set<Resources> resources= new HashSet<>();
在您的资源实体中:
@ManyToMany(fetch = FetchType.LAZY,
cascade = {
CascadeType.PERSIST,
CascadeType.MERGE
},
mappedBy = "resources")
private Set<Team> teams= new HashSet<>();
方法二
@Entity
@Table(name = "team_resources")
public class TeamResources implements Serializable {
@EmbeddedId
private TeamResourcesId id;
@ManyToOne
@JoinColumn(name = "team_id", referencedColumnName = "id", insertable = false, updatable = false)
private Team team;
@ManyToOne
@JoinColumn(name = "resources_id", referencedColumnName = "id", insertable = false, updatable = false)
private Resources resources;
public TeamResources (Team u, Resources r) {
// create primary key
this.id = new TeamResourcesId (u.getUserId(), q.getQuestionId());
// initialize attributes
this.user = u;
this.question = q;
}
@Embeddable
public static class TeamResourcesId implements Serializable {
@Column(name = "team_id")
protected Long teamId;
@Column(name = "resources_id")
protected Long resourcesId;
public TeamResourcesId () {
}
public TeamResourcesId (Long teamId, Long resourcesId) {
this.teamId= teamId;
this.resourcesId= resourcesId;
}
//Getter , setter. equal and hash
}
所以要回答你的问题,请遵循第二种方法,最好不要定义双向方法,因为如果处理不当,它可能会导致一些 运行 时间问题。
我是 Spring Boot 的新手。我有一个 table(团队),它有资源,我存储在一个单独的 table(资源)中,并且有 team_resource 映射 table(带有字段 teamid、resourceid)。我的问题是我也应该为 mapping_table 设置一个域 class 吗?
当我插入具有资源的新团队 (POST) 时,我在所有 3 个 table 中创建条目。我正在使用 facade/dao 模式写入/读取数据库。当团队被修改/删除时,我必须处理。 mapping_table 我应该有一个域 class 吗?
有多种方法可以处理它
方法一
像这样在您的团队和资源实体之间定义@ManyToMany
:
在团队实体中
@ManyToMany(fetch = FetchType.LAZY, cascade = { CascadeType.PERSIST, CascadeType.MERGE }) @JoinTable(name = "resources", joinColumns = { @JoinColumn(name = "id") }, inverseJoinColumns = { @JoinColumn(name = "id") }) private Set<Resources> resources= new HashSet<>();
在您的资源实体中:
@ManyToMany(fetch = FetchType.LAZY, cascade = { CascadeType.PERSIST, CascadeType.MERGE }, mappedBy = "resources") private Set<Team> teams= new HashSet<>();
方法二
@Entity
@Table(name = "team_resources")
public class TeamResources implements Serializable {
@EmbeddedId
private TeamResourcesId id;
@ManyToOne
@JoinColumn(name = "team_id", referencedColumnName = "id", insertable = false, updatable = false)
private Team team;
@ManyToOne
@JoinColumn(name = "resources_id", referencedColumnName = "id", insertable = false, updatable = false)
private Resources resources;
public TeamResources (Team u, Resources r) {
// create primary key
this.id = new TeamResourcesId (u.getUserId(), q.getQuestionId());
// initialize attributes
this.user = u;
this.question = q;
}
@Embeddable
public static class TeamResourcesId implements Serializable {
@Column(name = "team_id")
protected Long teamId;
@Column(name = "resources_id")
protected Long resourcesId;
public TeamResourcesId () {
}
public TeamResourcesId (Long teamId, Long resourcesId) {
this.teamId= teamId;
this.resourcesId= resourcesId;
}
//Getter , setter. equal and hash
}
所以要回答你的问题,请遵循第二种方法,最好不要定义双向方法,因为如果处理不当,它可能会导致一些 运行 时间问题。