@SuppressWarnings("serial")
@Entity
@Table(name = "BOOK")
@Cache(usage = CacheConcurrencyStrategy.READ_WRITE)
public class Book implements Serializable{

?private static final long serialVersionUID = -2700610405985954588L;
?
?private int oid;
?
?private String name;
?
?private String description;
?
?private Date publish;
?
?private Collection<Author> authors;

?@Id
?@GeneratedValue(strategy=GenerationType.SEQUENCE)
?public int getOid() {
??return oid;
?}

?public void setOid(int oid) {
??this.oid = oid;
?}

?public String getName() {
??return name;
?}

?public void setName(String name) {
??this.name = name;
?}

?public String getDescription() {
??return description;
?}

?public void setDescription(String description) {
??this.description = description;
?}

?@Temporal(value=TemporalType.TIMESTAMP)
?public Date getPublish() {
??return publish;
?}

?public void setPublish(Date publish) {
??this.publish = publish;
?}

?@ManyToMany(
???targetEntity=com.e104cn.pda.data.anno.Author.class,
???cascade ={CascadeType.PERSIST,CascadeType.MERGE},
??????????? fetch=FetchType.LAZY
?)
?@JoinTable(
???????? name = "book_author",
???????? joinColumns ={@JoinColumn(name="book_id")},
???????? inverseJoinColumns ={@JoinColumn(name= "author_id")}
?? )
?public Collection<Author> getAuthors() {
??return authors;
?}
?
?public void addAuthor(Author author){
??if(author == null){
???authors = new ArrayList<Author>();
??}
??if(!authors.contains(author)){
???authors.add(author);
??}
?}

?public void setAuthors(Collection<Author> authors) {
??this.authors = authors;
?}
?
}

/**@SuppressWarnings("serial")
@Entity
@Table(name = "AUTHOR")
@Cache(usage = CacheConcurrencyStrategy.READ_WRITE)*/
public class Author implements Serializable{

?private static final long serialVersionUID = 7131973910486229579L;
?
?private int id;
?
?private String firstName;
?
?private String lastName;
?
?private boolean male;
?
?private Date birthday;
?
?@Transient
?private Collection<Book> books ;

?@Id
?@GeneratedValue(strategy=GenerationType.SEQUENCE)
?public int getId() {
??return id;
?}

?public void setId(int oid) {
??this.id = oid;
?}

?public String getFirstName() {
??return firstName;
?}

?public void setFirstName(String firstName) {
??this.firstName = firstName;
?}

?public String getLastName() {
??return lastName;
?}

?public void setLastName(String lastName) {
??this.lastName = lastName;
?}

?public boolean isMale() {
??return male;
?}

?public void setMale(boolean male) {
??this.male = male;
?}

?@Temporal(value=TemporalType.TIMESTAMP)
?public Date getBirthday() {
??return birthday;
?}

?public void setBirthday(Date birthday) {
??this.birthday = birthday;
?}

?@ManyToMany(mappedBy="authors",
??cascade={CascadeType.PERSIST,CascadeType.ALL}
?)
?public Collection<Book> getBooks() {
??return books;
?}

?public void addBook(Book book){
??if(books == null){
???books = new ArrayList<Book>();
??}
??if(!books.contains(book)){
???books.add(book);
??}
?}
?
?public void setBooks(Collection<Book> books) {
??this.books = books;
?}
?
}
1、去掉藍色注釋的部分即可解決錯誤.
2、?注：@ManyToMany(mappedBy="authors",屬性一定要和book中的authors一致。