JPA 1.0中是否有任何JPA流利的API/Critera API？我正在使用OpenJPA

Question

是否有任何jpa 1.0流利的api /接口用于查询构建？我使用的是openjpa 1.x，所以我被JPA1困住了。

我发现QueryByProxy，但其maven回购工作不正常。

Answer 1

如果您遇到JPA 1.0，请考虑使用Querydsl，它在JPA之上提供流畅的类型安全API。您必须使用1.6.0之前的版本，即1.5.4（他们在1.6.0中转换为JPA 2.0）。这是IMO最好的选择。

Answer 2

简短的回答是没有。但是，这取决于您使用的提供商。例如，如果您使用的是Hibernate，那么您总是可以从休眠状态获取Criteria API。但是在JPA 1.0中不支持。但是在JPA 2.0中。

Answer 3

您可以在JPA和Hibernate中使用Fluent接口模式。我写了an article which explains this topic in great detail。

要总结一下，如果你正在使用Hibernate，你可以修改制定者返回实体：

@Entity(name = "Post") 
@Table(name = "post") 
public class Post { 

    @Id 
    private Long id; 

    private String title; 

    public Post() {} 

    public Post(String title) { 
     this.title = title; 
    } 

    @OneToMany(
     cascade = CascadeType.ALL, 
     orphanRemoval = true, 
     mappedBy = "post" 
    ) 
    private List<PostComment> comments = new ArrayList<>(); 

    public Long getId() { 
     return id; 
    } 

    public Post setId(Long id) { 
     this.id = id; 
     return this; 
    } 

    public String getTitle() { 
     return title; 
    } 

    public Post setTitle(String title) { 
     this.title = title; 
     return this; 
    } 

    public List<PostComment> getComments() { 
     return comments; 
    } 

    public Post addComment(PostComment comment) { 
     comment.setPost(this); 
     comments.add(comment); 
     return this; 
    } 
} 

@Entity(name = "PostComment") 
@Table(name = "post_comment") 
public class PostComment { 

    @Id 
    @GeneratedValue 
    private Long id; 

    private String review; 

    private Date createdOn; 

    @ManyToOne 
    private Post post; 

    public Long getId() { 
     return id; 
    } 

    public PostComment setId(Long id) { 
     this.id = id; 
     return this; 
    } 

    public String getReview() { 
     return review; 
    } 

    public PostComment setReview(String review) { 
     this.review = review; 
     return this; 
    } 

    public Date getCreatedOn() { 
     return createdOn; 
    } 

    public PostComment setCreatedOn(Date createdOn) { 
     this.createdOn = createdOn; 
     return this; 
    } 

    public Post getPost() { 
     return post; 
    } 

    public PostComment setPost(Post post) { 
     this.post = post; 
     return this; 
    } 
} 

这种方式，你可以建立家长和孩子的实体是这样的：

doInJPA(entityManager -> { 
    Post post = new Post() 
    .setId(1L) 
    .setTitle("High-Performance Java Persistence") 
    .addComment(
     new PostComment() 
     .setReview("Awesome book") 
     .setCreatedOn(Timestamp.from(
      LocalDateTime.now().minusDays(1).toInstant(ZoneOffset.UTC)) 
     ) 
    ) 
    .addComment(
     new PostComment() 
     .setReview("High-Performance Rocks!") 
     .setCreatedOn(Timestamp.from(
      LocalDateTime.now().minusDays(2).toInstant(ZoneOffset.UTC)) 
     ) 
    ) 
    .addComment(
     new PostComment() 
     .setReview("Database essentials to the rescue!") 
     .setCreatedOn(Timestamp.from(
      LocalDateTime.now().minusDays(3).toInstant(ZoneOffset.UTC)) 
     ) 
    ); 
    entityManager.persist(post); 
}); 

如果你关心JPA的便携性，那么你可能不想违反Java Bean的规范，在这种情况下，你需要添加流利的接口方法一起定期制定者：

@Entity(name = "Post") 
@Table(name = "post") 
public class Post { 

    @Id 
    private Long id; 

    private String title; 

    public Post() {} 

    public Post(String title) { 
     this.title = title; 
    } 

    @OneToMany(
     cascade = CascadeType.ALL, 
     orphanRemoval = true, 
     mappedBy = "post" 
    ) 
    private List<PostComment> comments = new ArrayList<>(); 

    public Long getId() { 
     return id; 
    } 

    public void setId(Long id) { 
     this.id = id; 
    } 

    public Post id(Long id) { 
     this.id = id; 
     return this; 
    } 

    public String getTitle() { 
     return title; 
    } 

    public void setTitle(String title) { 
     this.title = title; 
    } 

    public Post title(String title) { 
     this.title = title; 
     return this; 
    } 

    public List<PostComment> getComments() { 
     return comments; 
    } 

    public Post addComment(PostComment comment) { 
     comments.add(comment.post(this)); 
     return this; 
    } 
} 

@Entity(name = "PostComment") 
@Table(name = "post_comment") 
public class PostComment { 

    @Id 
    @GeneratedValue 
    private Long id; 

    private String review; 

    private Date createdOn; 

    @ManyToOne 
    private Post post; 

    public Long getId() { 
     return id; 
    } 

    public PostComment setId(Long id) { 
     this.id = id; 
     return this; 
    } 

    public String getReview() { 
     return review; 
    } 

    public void setReview(String review) { 
     this.review = review; 
    } 

    public PostComment review(String review) { 
     this.review = review; 
     return this; 
    } 

    public Date getCreatedOn() { 
     return createdOn; 
    } 

    public void setCreatedOn(Date createdOn) { 
     this.createdOn = createdOn; 
    } 

    public PostComment createdOn(Date createdOn) { 
     this.createdOn = createdOn; 
     return this; 
    } 

    public Post getPost() { 
     return post; 
    } 

    public void setPost(Post post) { 
     this.post = post; 
    } 

    public PostComment post(Post post) { 
     this.post = post; 
     return this; 
    } 
} 

实体建筑几乎等同于前一个：

doInJPA(entityManager -> { 
    Post post = new Post() 
    .id(1L) 
    .title("High-Performance Java Persistence") 
    .addComment(new PostComment() 
     .review("Awesome book") 
     .createdOn(Timestamp.from(
      LocalDateTime.now().minusDays(1).toInstant(ZoneOffset.UTC)) 
     ) 
    ) 
    .addComment(new PostComment() 
     .review("High-Performance Rocks!") 
     .createdOn(Timestamp.from(
      LocalDateTime.now().minusDays(2).toInstant(ZoneOffset.UTC)) 
     ) 
    ) 
    .addComment(new PostComment() 
     .review("Database essentials to the rescue!") 
     .createdOn(Timestamp.from(
      LocalDateTime.now().minusDays(3).toInstant(ZoneOffset.UTC)) 
     ) 
    ); 
    entityManager.persist(post); 
});