我试图学习使用spring框架，所以我从头开始使用了一个应用程序。目前，它应该是具有简单方法（例如创建用户，显示所有用户，按ID显示用户等）的REST API应用程序。
当我尝试删除一个组中的用户时，我的应用程序中断显示此错误：
2018-08-24 14:50:12.627 WARN 16804 --- [nio-8080-exec-2] o.h.engine.jdbc.spi.SqlExceptionHelper : SQL Error: 1064, SQLState: 42000
2018-08-24 14:50:12.627 ERROR 16804 --- [nio-8080-exec-2] o.h.engine.jdbc.spi.SqlExceptionHelper : You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'group group0_ where group0_.group_id=1' at line 1
2018-08-24 14:50:12.638 INFO 16804 --- [nio-8080-exec-2] o.h.e.internal.DefaultLoadEventListener : HHH000327: Error performing load command : org.hibernate.exception.SQLGrammarException: could not extract ResultSet
和很长的堆栈跟踪（太大，无法包含在代码示例中）
休眠执行的查询为：
Hibernate: select user0_.user_id as user_id1_4_0_, user0_.is_active as is_activ2_4_0_, user0_.confirmation_token as confirma3_4_0_, user0_.date_created as date_cre4_4_0_, user0_.email_address as email_ad5_4_0_, user0_.first_name as first_na6_4_0_, user0_.last_name as last_nam7_4_0_, user0_.notification_type as notifica8_4_0_, user0_.password as password9_4_0_, user0_.phone_number as phone_n10_4_0_, user0_.username as usernam11_4_0_ from user user0_ where user0_.user_id=?
Hibernate: select groups0_.user_id as user_id2_5_0_, groups0_.group_id as group_id1_5_0_, groups0_.group_id as group_id1_5_1_, groups0_.user_id as user_id2_5_1_, groups0_.is_blocked as is_block3_5_1_, groups0_.user_type_id as user_typ4_5_1_ from user_to_group groups0_ where groups0_.user_id=?
Hibernate: select group0_.group_id as group_id1_0_0_, group0_.created_by as created_5_0_0_, group0_.date_created as date_cre2_0_0_, group0_.is_private as is_priva3_0_0_, group0_.name as name4_0_0_ from group group0_ where group0_.group_id=?
用户实体：
@Entity
@Table(name = "user")
public class User {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
@Column(name = "user_id")
private Long id;
@Column(name = "first_name")
private String firstName;
@Column(name = "last_name")
private String lastName;
@Column(name = "username")
private String username;
@Column(name = "email_address",
unique = true)
private String emailAddress;
@Column(name = "phone_number",
unique = true)
private String phoneNumber;
@Column(name = "password")
private String password;
@Column(name = "notification_type",
insertable = false)
private String notificationType;
@Column(name = "date_created")
private Date dateCreated;
@Column(name = "confirmation_token",
unique = true)
private String confirmationToken;
@Column(name = "is_active",
insertable = false)
private Boolean active;
@OneToMany(
mappedBy = "user",
cascade = CascadeType.ALL,
orphanRemoval = true
)
private List<UserGroup> groups = new ArrayList<>();
public User(String firstName, String lastName, String username, String emailAddress, String phoneNumber, String password) {
this.firstName = firstName;
this.lastName = lastName;
this.username = username;
this.emailAddress = emailAddress;
this.phoneNumber = phoneNumber;
this.password = password;
dateCreated = new Date();
}
public User() {
}
public void addGroup(Group group) {
UserGroup userGroup = new UserGroup(this, group);
groups.add(userGroup);
group.getUsers().add(userGroup);
}
public void removeGroup(Group group) {
for (Iterator<UserGroup> iterator = groups.iterator();
iterator.hasNext(); ) {
UserGroup userGroup = iterator.next();
if (userGroup.getUser().equals(this) &&
userGroup.getGroup().equals(group)) {
iterator.remove();
userGroup.getGroup().getUsers().remove(userGroup);
userGroup.setUser(null);
userGroup.setGroup(null);
}
}
}
//Getters and setters
@Override
public boolean equals(Object o) {
if (this == o) return true;
if (o == null || getClass() != o.getClass()) return false;
User user = (User) o;
return Objects.equals(firstName, user.firstName) &&
Objects.equals(lastName, user.lastName);
}
@Override
public int hashCode() {
return Objects.hash(firstName, lastName);
}
}
组实体
@Entity
@Table(name = "group")
@NaturalIdCache
@Cache(
usage = CacheConcurrencyStrategy.READ_WRITE
)
public class Group {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
@Column(name = "group_id")
private Long id;
@NaturalId
private String name;
@Column(name = "date_created")
private Date dateCreated;
@Column(name = "is_private")
@GeneratedValue(generator = "0")
private boolean isPrivate;
@OneToOne(fetch = FetchType.LAZY,
cascade = CascadeType.ALL)
@JoinColumn(name = "created_by")
private User createdBy;
@OneToMany(
mappedBy = "group",
cascade = CascadeType.ALL,
orphanRemoval = true
)
private List<UserGroup> users = new ArrayList<>();
public Group(String name) {
this.name = name;
this.dateCreated = new Date();
}
public Group() {
}
//Getters and setters
@Override
public boolean equals(Object o) {
if (this == o) return true;
if (o == null || getClass() != o.getClass()) return false;
Group group = (Group) o;
return Objects.equals(name, group.name);
}
@Override
public int hashCode() {
return Objects.hash(name);
}
}
用户组实体（联接表）为
@Entity
@Table(name = "user_to_group")
public class UserGroup {
@EmbeddedId
private UserGroupId id;
@ManyToOne(fetch = FetchType.LAZY,
cascade = CascadeType.ALL)
@JoinColumn(name = "user_id", insertable = false, updatable = false)
private User user;
@ManyToOne(fetch = FetchType.LAZY,
cascade = CascadeType.ALL)
@JoinColumn(name = "group_id", insertable = false, updatable = false)
private Group group;
@ManyToOne(fetch = FetchType.LAZY,
cascade = CascadeType.ALL)
@JoinColumn(name = "user_type_id")
private UserType userType;
@Column(name = "is_blocked")
@GeneratedValue(generator = "0")
private boolean isBlocked;
public UserGroup() {
}
public UserGroup(User user, Group group) {
this.user = user;
this.group = group;
this.id = new UserGroupId(user.getId(), group.getId());
}
//Getters and setters
@Override
public boolean equals(Object o) {
if (this == o) return true;
if (o == null || getClass() != o.getClass()) return false;
UserGroup userGroup = (UserGroup) o;
return Objects.equals(user, userGroup.user) &&
Objects.equals(group, userGroup.group);
}
@Override
public int hashCode() {
return Objects.hash(user, group);
}
}
UserGroupId（复合主键）是
@Embeddable
public class UserGroupId implements Serializable {
@Column(name = "user_id")
private Long userId;
@Column(name = "group_id")
private Long groupId;
public UserGroupId() {
}
public UserGroupId(Long userId, Long groupId) {
this.userId = userId;
this.groupId = groupId;
}
//Getters and setters
@Override
public boolean equals(Object o) {
if (this == o) return true;
if (o == null || getClass() != o.getClass())
return false;
UserGroupId that = (UserGroupId) o;
return Objects.equals(userId, that.userId) &&
Objects.equals(groupId, that.userId);
}
@Override
public int hashCode() {
return Objects.hash(userId, groupId);
}
}
数据库的DDL为：
USE chatapp;
CREATE TABLE user (
user_id int NOT NULL AUTO_INCREMENT,
confirmation_token varchar(255),
first_name varchar(100) NOT NULL,
last_name varchar(100) NOT NULL,
username varchar(100) NOT NULL,
email_address varchar(100) UNIQUE NOT NULL,
phone_number varchar(100) NOT NULL,
password varchar(255) NOT NULL,
notification_type varchar(30) NOT NULL DEFAULT "email",
date_created datetime NOT NULL,
is_active bool NOT NULL DEFAULT false,
CONSTRAINT user_pk PRIMARY KEY (user_id)
);
CREATE TABLE `group` (
group_id int NOT NULL AUTO_INCREMENT,
name varchar(100) NULL,
date_created datetime NOT NULL,
is_private bool NOT NULL DEFAULT false,
created_by int NULL,
CONSTRAINT group_pk PRIMARY KEY (group_id),
CONSTRAINT group_user_fk FOREIGN KEY(created_by)
REFERENCES user (user_id) ON DELETE SET NULL
);
CREATE TABLE privilege (
id int NOT NULL,
name varchar(50) NOT NULL,
CONSTRAINT privilege_pk PRIMARY KEY (id)
);
CREATE TABLE user_type (
id int NOT NULL AUTO_INCREMENT,
type_name varchar(50) NOT NULL,
CONSTRAINT user_type_pk PRIMARY KEY (id)
);
CREATE TABLE user_to_group (
user_id int NOT NULL,
group_id int NOT NULL,
user_type_id int NOT NULL,
is_blocked bool NOT NULL DEFAULT false,
CONSTRAINT user_to_group_pk PRIMARY KEY (user_id,group_id),
CONSTRAINT user_to_group_group_fk FOREIGN KEY(group_id)
REFERENCES `group` (group_id),
CONSTRAINT user_to_group_user_type_fk FOREIGN KEY(user_type_id)
REFERENCES user_type (id),
CONSTRAINT user_to_group_user_fk FOREIGN KEY(user_id)
REFERENCES user (user_id)
);
CREATE TABLE user_type_to_privilege (
user_type_id int NOT NULL,
privilege_id int NOT NULL,
CONSTRAINT user_type_to_privilege_pk PRIMARY KEY (user_type_id,privilege_id),
CONSTRAINT user_type_to_privilege_privilege_fk FOREIGN KEY(privilege_id)
REFERENCES privilege (id),
CONSTRAINT user_type_to_privilege_user_type_fk FOREIGN KEY(user_type_id)
REFERENCES user_type (id)
);
对于CRUD操作，我使用spring数据，我有一个存储库和一个用户服务，并且使用默认的deleteById方法。
任何帮助都将不胜感激！抱歉，很长的帖子，但我试图向您显示我认为您需要的所有信息。如果您还需要其他东西，请告诉我。
答案 0 :(得分：2)
很遗憾，group是保留的SQL关键字（例如group by）。
请考虑为您的group表命名。