使用休眠訪問數據時java.lang.StackOverflowError

Question

我在嘗試在休眠中連接2個表時遇到錯誤。在這裏複製代碼。

/*ADDRESS table entity mapping */ 

@Entity 
@Table(name = "ADDRESS") 
public class AddressEntity { 

    @ManyToOne(fetch = FetchType.EAGER, cascade = { CascadeType.ALL }) 
    @JoinColumn(name = "user_id") 
    private UserEntity user; 

    // setters and getters and other attributes. 

} 


/* APPUSER table entity mapping */ 

@Entity 
@Table(name = "APPUSER") 
public class UserEntity { 

    @Id 
    @GeneratedValue 
    @Column(name = "USER_ID") 
    private Long userId; 

    @OneToMany(fetch = FetchType.EAGER, mappedBy = "user") 
    private Set<AddressEntity> addresses; 

    // setters and getters and other attributes. 

} 

問題在於映射地址和用戶實體。每個用戶可以有多個地址，這是要求。請幫忙。

複製表DDL語句如下。它是用戶和地址表之間的一對多關係。

SQLS表：

CREATE TABLE `appuser` (
    `user_id` int(11) NOT NULL AUTO_INCREMENT, 
    `first_name` varchar(255) NOT NULL, 
    `last_name` varchar(255) DEFAULT NULL, 
    `email_address` varchar(1024) NOT NULL, 
    `password` varchar(1024) NOT NULL, 
    `active` tinyint(1) DEFAULT '1', 
    `popularity_rating` int(11) DEFAULT NULL, 
    `join_date` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP, 
    PRIMARY KEY (`user_id`) 
) ENGINE=InnoDB AUTO_INCREMENT=7 DEFAULT CHARSET=utf8 

CREATE TABLE `address` (
    `address_id` int(11) NOT NULL AUTO_INCREMENT, 
    `address_line1` varchar(38) NOT NULL, 
    `address_line2` varchar(38) NOT NULL, 
    `city` varchar(38) NOT NULL, 
    `state` varchar(38) NOT NULL, 
    `zip` varchar(10) NOT NULL, 
    `address_type` varchar(45) NOT NULL, 
    `user_id` int(11) NOT NULL, 
    PRIMARY KEY (`address_id`), 
    KEY `fk_address_user_idx` (`user_id`), 
    CONSTRAINT `fk_address_user` FOREIGN KEY (`user_id`) REFERENCES `appuser` (`user_id`) 
) ENGINE=InnoDB AUTO_INCREMENT=9 DEFAULT CHARSET=utf8 

上面加入地址和用戶表給我的StackOverflowError。

預期的結果是：

{ 
    "userId": 1, 
    "firstName": "alb", 
    "lastName": "va", 
    "emailAddress": "alb@va.com", 
    "password": "albva", 
    "addresses": [ 
     { 
      "addressLine1": "222 plano pkwy", 
      "addressLine2": "apt 22", 
      "city": "plano", 
      "state": "tx", 
      "zip": "75034", 
      "country": null 
     }, { 
      "addressLine1": "555 plano pkwy", 
      "addressLine2": "apt 11", 
      "city": "plano", 
      "state": "tx", 
      "zip": "75024", 
      "country": null 
     } 
    ], 
    "popularityRating": 6, 
    "joinDate": 1504897922000, 
    "roles": [] 
} 

結果，而調用Web服務，我得到的是一個無限loop.Which導致堆棧溢出錯誤：

{"userId":2,"firstName":"rax","lastName":"tax","emailAddress":"rax@tax.com","password":"raxtax","addresses":[{"addressLine1":"2001 spring creek","addressLine2":"apt 724","city":"plano","state":"tx","zip":"75074","country":null,"addressType":null,"user":{"userId":2,"firstName":"rax","lastName":"tax","emailAddress":"rax@tax.com","password":"raxtax","addresses":[{"addressLine1":"2001 spring creek","addressLine2":"apt 724","city":"plano","state":"tx","zip":"75074","country":null,"addressType":null,"user":{"userId":2,"firstName":"rax","lastName":"tax","emailAddress":"rax@tax.com","password":"raxtax","addresses":[{"addressLine1":"2001 spring creek","addressLine2":"apt 724","city":"plano","state":"tx","zip":"75074","country":null,"addressType":null,"user":{"userId":2,"firstName":"rax","lastName":"tax","emailAddress":"rax@tax.com","password":"raxtax","addresses":[{"addressLine1":"2001 spring creek","addressLine2":"apt 724","city":"plano","state":"tx","zip":"75074","country":null,"addressType":null,"user":{"userId":2,"firstName":"rax","lastName":"tax","emailAddress":"rax@tax.com","password":"raxtax","addresses":[{"addressLine1":"2001 spring creek","addressLine2":"apt 724","city":"plano","state":"tx","zip":"75074","country":null,"addressType":null,"user":{"userId":2,"firstName":"rax","lastName":"tax","emailAddress":"rax@tax.com","password":"raxtax","addresses":[{"addressLine1":"2001 spring creek","addressLine2":"apt 724","city":"plano","state":"tx","zip":"75074","country":null,"addressType":null,"user":{"userId":2,"firstName":"rax","lastName":"tax","emailAddress":"rax@tax.com","password":"raxtax","addresses":[{"addressLine1":"2001 spring creek","addressLine2":"apt 724","city":"plano","state":"tx","zip":"75074","country":null,"addressType":null,"user": ... 

Answer 1

當您嘗試加入兩個表如上所述，它們之間的依賴關係必然是無限循環，因爲表A試圖從表B獲取數據。表B與表A有依賴關係，並嘗試從表A獲取數據。它運行到無限循環並繼續在此引起堆棧溢出主器件接收。 解決方法是用@JsonManagedReference和@JsonBackReference註釋你的字段。有了這個，使用@JsonManagedReference標記的類將被序列化，而使用@JsonBackReference標記的類不會。這打破了無限循環。在你的代碼中，你的實體看起來像這樣;

/*ADDRESS table entity mapping */ 

@Entity 
@Table(name = "ADDRESS") 
public class AddressEntity { 

@ManyToOne(fetch = FetchType.EAGER, cascade = { CascadeType.ALL }) 
@JoinColumn(name = "user_id") 
@JsonBackReference 
private UserEntity user; 

// setters and getters and other attributes. 

} 


/* APPUSER table entity mapping */ 

@Entity 
@Table(name = "APPUSER") 
public class UserEntity { 

@Id 
@GeneratedValue 
@Column(name = "USER_ID") 
private Long userId; 

@OneToMany(fetch = FetchType.EAGER, mappedBy = "user") 
@JsonManagedReference 
private Set<AddressEntity> addresses; 

// setters and getters and other attributes. 

}