抽象類和Spring問題

Question

我正在開發基於Spring框架的簡單Web應用程序。我有這兩個文件，這是映射數據庫表的迴應：

import javax.persistence.*; 
import java.util.Date; 

/** 
* Abstract class for all publications of BIS 
* @author Tomek Zaremba 
*/ 

public abstract class GenericPost { 

@Temporal(TemporalType.DATE) 
@Column(name = "date_added") 
private Date dateAdded; 

@Column(name = "title") 
private String title; 

@Column(name = "description") 
private String description; 

/** 
* 
* @return title of publication 
*/ 
public String getTitle() { 
    return title; 
} 

/** 
* 
* @param title to be set for publication 
*/ 
public void setTitle(String title) { 
    this.title = title; 
} 

/** 
* 
* @return description of publication 
*/ 
public String getDescription() { 
    return description; 
} 

/** 
* 
* @param description of publication 
*/ 
public void setDescription(String description) { 
    this.description = description; 
} 

/** 
* 
* @return date when publication was added 
*/ 
public Date getDateAdded() { 
    return dateAdded; 
} 

/** 
* 
* @param dateAdded set the date of adding for publication 
*/ 
public void setDateAdded(Date dateAdded) { 
    this.dateAdded = dateAdded; 
} 
} 

和另：

import javax.persistence.*; 
import java.io.Serializable; 

/** 
* Instances of Link represents and collects data about single link stored in BIS database 
* @author Tomek Zaremba 
*/ 
@Entity 
@Table(name="Link", schema="public") 
public class Link extends GenericPost implements Serializable{ 

@Id 
@Column(name="id", unique=true) 
@GeneratedValue(strategy= GenerationType.SEQUENCE, generator="link_id_seq") 
@SequenceGenerator(sequenceName="link_id_seq", name="link_id_seq") 
private Integer id; 

@Column(name="link") 
private String link; 

@ManyToOne(fetch = FetchType.LAZY) 
@JoinColumn(name = "author_user_id") 
private User user; 

/** 
* 
* @return id of link 
*/ 
public Integer getId() { 
    return id; 
} 

/** 
* 
* @param id to be set to link 
*/ 
public void setId(Integer id) { 
    this.id = id; 
} 

/** 
* 
* @return link which is connected with Link instance 
*/ 
public String getLink() { 
    return link; 
} 

/** 
* 
* @param link to be set fo Link instance 
*/ 
public void setLink(String link) { 
    this.link = link; 
} 

/** 
* 
* @return User instance connected with Link instance 
*/ 
public User getUser() { 
    return user; 
} 

/** 
* 
* @param user to be set for Link instance 
*/ 
public void setUser(User user) { 
    this.user = user; 
} 
} 

的問題是：當我使用從通用類（吸氣）方法，爲什麼我總是得到null，當我使用來自Link類的getters時，我得到正確的數據？數據庫訪問沒問題，junit測試傳遞沒有錯誤。感謝幫助。

Answer 1

GenericPost類應註明@MappedSuperclass。否則，映射不考慮其持久性註釋。

注意：您的單元測試可能應該更新，以檢查超類字段的映射是否按預期工作。

Answer 2

我不認爲這是春天的錯。你需要註釋你的父類@MappedSuperclass