SpringBoot Data Jpa 級聯查詢死循環

後端 > SpringBoot > 踩坑踩坑 hibernate

Created At : 2023-04-21 17:15

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踩坑紀錄

踩坑紀錄

使用SpringBoot data JPA使用@OneToOne/@OneToMnay查詢數據時死循環，報錯內容如下：

java.lang.StackOverflowError at java.util.Date.getYear(Date.java:651) at java.sql.Timestamp.toString(Timestamp.java:279)....

解決方案：

使用debug查詢後發現是查詢時發生死循環

經過測試後，發現級聯時會在兩個地方產生死循環

1.實體類的toString()方法中包含對級聯對象的輸出，代碼中調用了實體類的toString()方法。

2.接口查詢或轉為Json返回前端時，對實體對象進行序列化。

解決實體類的toString()方法中包含對級聯對象的輸出 (查詢SQL時報錯)

方法一：在其中一個實體對象修改toString()，將級聯對象移除

@Entity
@Getter
@Setter
@Table(name = "t_company")
public class Company {
@Id
@GeneratedValue
private int companyId;
private String companyName;
private String companyTel;
private String companyAddress;
@OneToOne(mappedBy = "company")
private Good good;

@Override
public String toString() {
    return "Company{" +
            "companyId=" + companyId +
            ", companyName='" + companyName + '\'' +
            ", companyTel='" + companyTel + '\'' +
            ", companyAddress='" + companyAddress + '\'' +
            '}';
}
}

方法二：使用lombok裡面提供的注釋@ToString.Exclude
```java
@Entity
@Data
@Table(name = “t_company”)
public class Company {
@Id
@GeneratedValue
private int companyId;
private String companyName;
private String companyTel;
private String companyAddress;
@OneToOne(mappedBy = “company”)
@ToString.Exclude
private Good good;

}


* 解決轉為Json返回前端時，對實體對象進行序列化死循環問題
  * 在其中一個級聯對象中使用`@JsonIgnore`或`@JsonIgnoreProperties`
```java
@Entity
@Data
@Table(name = "t_company")
public class Company {
    @Id
    @GeneratedValue
    private int companyId;
    private String companyName;
    private String companyTel;
    private String companyAddress;
    @OneToOne(mappedBy = "company")
    @JsonIgnore
    @ToString.Exclude
    private Good good;

}

不會產生死循環的代碼如下：

@Entity
@Data
@Table(name = "t_good")
public class Good {
    @Id
    @GeneratedValue
    private int gId;
    private String lineId;
    private Date pDate;
    @OneToOne(optional = false, cascade = CascadeType.ALL)
    @JoinColumn(name = "companyId")
    //@JsonIgnoreProperties("good") 忽略company中的good屬性
    private Company company;
    private String lineName;
    private String lineType;
    private int totalCount;
    private BigDecimal unitPrice;
    private BigDecimal totalPrice;
    private BigDecimal totalProfit;
}

@Entity
@Data
@Table(name = "t_company")
public class Company {
  @Id
  @GeneratedValue
  private int companyId;
  private String companyName;
  private String companyTel;
  private String companyAddress;
  @OneToOne(mappedBy = "company")
  @JsonIgnore //忽略good實體的查詢，避免死循環
  @ToString.Exclude
  private Good good;

}

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