我是JAVA和JPA的新手,我搜索了解决方案但无济于事。我发现了很多例子,但他们没有在我的方案中工作。 我想下面给出这两个表映射:双向多对一映射
书架表
CREATE TABLE "SOA2"."BOOKSHELF" (
"BOOKSHELF_ID" NUMBER(19,0) NOT NULL ENABLE,
"NAME_TXT" VARCHAR2(255 CHAR),
PRIMARY KEY ("BOOKSHELF_ID") USING INDEX PCTFREE 10 INITRANS 2
MAXTRANS 255 NOCOMPRESS LOGGING
TABLESPACE "SOA2" ENABLE
) SEGMENT CREATION DEFERRED PCTFREE 10 PCTUSED 40 INITRANS 1
MAXTRANS 255 NOCOMPRESS LOGGING TABLESPACE "SOA2" ;
和
书表
CREATE TABLE "SOA2"."BOOK" (
"BOOK_IX" NUMBER(19,0) NOT NULL ENABLE,
"BOOKSHELF_ID" NUMBER(19,0) NOT NULL ENABLE,
"NAME_TXT" VARCHAR2(255 CHAR),
PRIMARY KEY ("BOOK_IX", "BOOKSHELF_ID") USING INDEX PCTFREE 10 INITRANS 2
MAXTRANS 255 NOCOMPRESS LOGGING TABLESPACE "SOA2" ENABLE, CONSTRAINT "FK_RJWHY4FC"
FOREIGN KEY ("BOOKSHELF_ID")
REFERENCES "SOA2"."BOOKSHELF" ("BOOKSHELF_ID") ENABLE)
SEGMENT CREATION DEFERRED PCTFREE 10 PCTUSED 40 INITRANS 1
MAXTRANS 255 NOCOMPRESS LOGGING TABLESPACE "SOA2" ;
为了便于理解,下面的结构如下所示
Bookshelf Table and Book Table 经过所有搜索后,我使用Eclipse“JPA Entities from Tables”工具。 它产生以下的课给我:
Bookshelf.java
@Entity
@Table(name="BOOKSHELF")
public class Bookshelf implements Serializable {
@Id
@Column(name="BOOKSHELF_ID", unique=true)
private long bookshelfId;
@Column(name="NAME_TXT")
private String nameTxt;
//bi-directional many-to-one association to Book
@OneToMany(mappedBy="bookshelf", cascade={CascadeType.ALL})
private List<Book> books;
public List<Book> getBooks() {
return this.books;
}
public void setBooks(List<Book> books) {
this.books = books;
}
//Code removed for the sake of brevity
}
Book.java
@Entity
@Table(name="BOOK")
public class Book implements Serializable {
@EmbeddedId
private BookPK id;
@Column(name="NAME_TXT", length=255)
private String nameTxt;
//bi-directional many-to-one association to Bookshelf
@ManyToOne(cascade={CascadeType.ALL})
@JoinColumn(name="BOOKSHELF_ID", nullable=false, insertable=false, updatable=false)
private Bookshelf bookshelf;
//Code removed for the sake of brevity
}
BookPK.java
@Embeddable
public class BookPK implements Serializable {
@Column(name="BOOK_IX")
private long bookIx;
@Column(name="BOOKSHELF_ID", insertable=false, updatable=false, unique=true, nullable=false)
private long bookshelfId;
public BookPK(long bkShlfId, long bkId) {
this.bookshelfId = bkShlfId;
this.bookIx = bkId;
}
//Code removed for the sake of brevity
只有一本书成功
Test.java
//Physics Bookshelf
Bookshelf physicsShelf = new Bookshelf();
physicsShelf.setNameTxt("Physics");
physicsShelf.setBookshelfId(500);
//Add Books
Book book1 = new Book();
book1.setNameTxt("God and the Physics");
book1.setId(new BookPK(500, 600));
Book book2 = new Book();
book2.setNameTxt("Hyperspace");
//if I pass 500 as first param in below constructor
//Changing 500 to 501 solves the issue
book2.setId(new BookPK(500, 600)); //javax.persistence.EntityExistsException: A different object with the same identifier value was already associated with the session : [books.Book#[email protected]]
//Add Books into list
List<Book> bookList = new ArrayList<Book>();
bookList.add(book1);
//Error: Following error appears if I uncomment the following line
bookList.add(book2); //Caused by: java.sql.SQLIntegrityConstraintViolationException: ORA-02291: integrity constraint (SOA2.FK_RJ) violated - parent key not found
//Set Books
physicsShelf.setBooks(bookList);
EntityTransaction transaction = entitymanager.getTransaction();
transaction.begin();
entitymanager.persist(physicsShelf);
transaction.commit();
physicsShelf插入,如果我在插入第二本书的书目它给了我在错误描述:0
}
我测试这是Test.java评论。
请指引我
什么,我做错了,如何纠正它。我很困难。
有什么办法通过注释其他两个类来摆脱BookPK.java类。
我不能更改数据库 我使用Oracle 11g与JPA 2。1
任何帮助将高度赞赏
问候
更换
如若BOOKID的第二册比BOOKID是不同的BOOK1?在上面的代码中,两者似乎都与600相同? – 2014-12-03 06:10:57
感谢您的回答。 – 2014-12-03 07:00:27