JPA @OneToMany 不获取 child

Question

表结构如下:

desc customer_survey
Name        Null     Type         
----------- -------- ------------ 
SURVEYID    NOT NULL VARCHAR2(10) 
CUSTNO      NOT NULL VARCHAR2(10) 
SRNO                 NUMBER(10)   
AVGRATINGS           NUMBER(5,2)  
COMMENTS             VARCHAR2(50) 
SENTON               DATE         
RESPONDEDON          DATE         

desc Survey_response
Name             Null     Type         
---------------- -------- ------------ 
SURVEYRESPONSEID NOT NULL NUMBER(10)   
RATINGS          NOT NULL NUMBER(2)    
QNO              NOT NULL VARCHAR2(10) 
SURVEYID         NOT NULL VARCHAR2(10) 

Java 类:

 public class CustomerSurvey implements Serializable {

@OneToMany(fetch=FetchType.EAGER, mappedBy="customerSurvey", 
     cascade=CascadeType.ALL)
private Set<SurveyResponse> responses;
 ......

 public class SurveyResponse {

@ManyToOne(fetch=FetchType.LAZY)
@JoinColumn(name="SURVEYID", referencedColumnName="surveyId")
private CustomerSurvey customerSurvey;

 ......

客户端代码:

 List<CustomerSurvey> surveys = workService.getSurveysByCustomer("testCNo2");
 System.out.println("surveys size = " + surveys.size());

 for(CustomerSurvey survey: surveys) {
System.out.println("getting responses from the survey object now..");
Set<SurveyResponse> responses = survey.getResponses();
System.out.println("responses size= .." + responses.size());
 }

控制台显示:

调查规模 = 1 现在从调查对象那里得到回应.. 响应大小= ..0

而数据库中有 7 个针对所选调查的回复。

Answer 1

启用日志记录并查看 SQL 是否正确。

很难从您不完整的代码中分辨出来，但通常 OneToMany 不应使用 JoinColumn，而应使用 mappedBy，而 ManyToOne 中的连接列应引用对象的 ID。

同时确保在插入对象时设置关系的两边。