java - 如何为具有复合主键和外键的 oneToMany 关系创建 Hibernate 映射文件？

Question

数据库表是:

Create table CatalogRequirements (
    semester varchar(20) NOT NULL,
    year int NOT NULL,
    program varchar(20) not null,
    GPA decimal(5 , 2 ) NOT NULL,
    ILETS decimal(5 , 2 ),
    TOFEL int,
    Backlogs int,
    Pre_requisite1 varchar(20),
    Pre_requisite2 varchar(20),
    compsmingpa decimal(5,2) not null,
    compsminHours int not null,
    Primary key (semester , year,program)
);
    Create table Catalog_Course (
    courseNum int NOT NULL,
    semester varchar(20) not null,
    year int not  null,
    program varchar(20) not null,
    Hours int NOT NULL,
    MIN_GPA decimal(3 , 2 ) NOT NULL,primary key(coursenum,semester,year,program),
    FOREIGN KEY (coursenum)
        references nwcourse (coursenum),
    FOREIGN KEY (semester,year,program)
        references CatalogRequirements (semester,year,program)
);

managedbean 文件是

/* This is CatalogRequirement Class */

 @ManagedBean
 @SessionScoped
 @Entity
 @IdClass(CatalogRequirementsId.class)
 public class CatalogRequirements implements Serializable{


   @Id
   private String semester;
   @Id
   private int year;
   @Id
   private String program;
   @Id
   CatalogRequirementsId crPK = new CatalogRequirementsId();
   private double GRE;
private double IELTS;
private int TOEFL;
private int Backlogs;
private String PreRequisites1;
private String PreRequisites2;
private double compsMinGpa;
private int CompsMinHours;
private CatalogCourse cc;


@OneToMany(mappedBy = "catalogrequirements")
private Set<CatalogCourse> catalogCourses;

public CatalogRequirements() {
}

public CatalogRequirements(double GRE,double IELTS, int TOEFL, int Backlogs, String PreRequisites1, String PreRequisites2, double compsMinGpa, int CompsMinHours) {
    this.GRE = GRE;
    this.IELTS = IELTS;
    this.TOEFL = TOEFL;
    this.Backlogs = Backlogs;
    this.PreRequisites1 = PreRequisites1;
    this.PreRequisites2 = PreRequisites2;
    this.compsMinGpa = compsMinGpa;
    this.CompsMinHours = CompsMinHours;
}

public CatalogRequirementsId getCrPK() {
    return crPK;
}

public void setCrPK(CatalogRequirementsId crPK) {
    this.crPK = crPK;
}

public Set<CatalogCourse> getCatalogCourses() {
    return catalogCourses;
}

public void setCatalogCourses(Set<CatalogCourse> catalogCourses) {
    this.catalogCourses = catalogCourses;
}

public double getGRE() {
    return GRE;
}

public void setGRE(double GRE) {
    this.GRE = GRE;
}

public double getIELTS() {
    return IELTS;
}

public void setIELTS(double IELTS) {
    this.IELTS = IELTS;
}

public int getTOEFL() {
    return TOEFL;
}

public void setTOEFL(int TOEFL) {
    this.TOEFL = TOEFL;
}

public int getBacklogs() {
    return Backlogs;
}

public void setBacklogs(int Backlogs) {
    this.Backlogs = Backlogs;
}

public String getPreRequisites1() {
    return PreRequisites1;
}

public void setPreRequisites1(String PreRequisites1) {
    this.PreRequisites1 = PreRequisites1;
}

public String getPreRequisites2() {
    return PreRequisites2;
}

public void setPreRequisites2(String PreRequisites2) {
    this.PreRequisites2 = PreRequisites2;
}

public double getCompsMinGpa() {
    return compsMinGpa;
}

public void setCompsMinGpa(double compsMinGpa) {
    this.compsMinGpa = compsMinGpa;
}

public int getCompsMinHours() {
    return CompsMinHours;
}

public void setCompsMinHours(int CompsMinHours) {
    this.CompsMinHours = CompsMinHours;
}

public String getSemester() {
    return semester;
}

public void setSemester(String semester) {
    this.semester = semester;
}

public int getYear() {
    return year;
}

public void setYear(int year) {
    this.year = year;
}

public String getProgram() {
    return program;
}

public void setProgram(String program) {
    this.program = program;
}

public void saveCatalog() {
    CreateCatalogDao dao = new CreateCatalogDao();
    dao.createCatalog(this);

}
}

这是 CatalogRequirementsId 类

 public class CatalogRequirementsId implements Serializable{

private String semester;
private int year;
private String program;

public CatalogRequirementsId() {
}

public CatalogRequirementsId(String semester, int year, String program) {
    this.semester = semester;
    this.year = year;
    this.program = program;
}

public String getSemester() {
    return semester;
}

public void setSemester(String semester) {
    this.semester = semester;
}

public int getYear() {
    return year;
}

public void setYear(int year) {
    this.year = year;
}

public String getProgram() {
    return program;
}

public void setProgram(String program) {
    this.program = program;
}

@Override
public int hashCode() {
    int hash = 7;
    hash = 17 * hash + Objects.hashCode(this.semester);
    hash = 17 * hash + Objects.hashCode(this.year);
    hash = 17 * hash + Objects.hashCode(this.program);
    return hash;
}

@Override
public boolean equals(Object obj) {
    if (obj == null) {
        return false;
    }
    if (getClass() != obj.getClass()) {
        return false;
    }
    final CatalogRequirementsId other = (CatalogRequirementsId) obj;
    if (!Objects.equals(this.semester, other.semester)) {
        return false;
    }
    if (!Objects.equals(this.year, other.year)) {
        return false;
    }
    if (!Objects.equals(this.program, other.program)) {
        return false;
    }
    return true;
}
}

这是 CatalogCourse 类

@ManagedBean
@SessionScoped
@Entity
@IdClass(CatalogCourseId.class)
public class CatalogCourse implements Serializable{

@Id
CatalogCourseId ccid = new CatalogCourseId();
@Id
private String CourseNo;
private int CreditHours;
private double MinGrade;

@ManyToOne
private CatalogRequirements catalogrequirements;
//private CatalogCourse cc;

public CatalogCourse() {
}

public CatalogCourse(String CourseNo, int CreditHours, double MinGrade, CatalogRequirements catalogrequirements) {
    this.CourseNo = CourseNo;
    this.CreditHours = CreditHours;
    this.MinGrade = MinGrade;
    this.catalogrequirements = catalogrequirements;
}

public CatalogRequirements getCatalogrequirements() {
    return catalogrequirements;
}

public void setCatalogrequirements(CatalogRequirements catalogrequirements) {
    this.catalogrequirements = catalogrequirements;
}

public CatalogCourseId getCcid() {
    return ccid;
}

public void setCcid(CatalogCourseId ccid) {
    this.ccid = ccid;
}

public int getCreditHours() {
    return CreditHours;
}

public void setCreditHours(int CreditHours) {
    this.CreditHours = CreditHours;
}

public double getMinGrade() {
    return MinGrade;
}

public void setMinGrade(double MinGrade) {
    this.MinGrade = MinGrade;
}

public String getCourseNo(){
    return getCcid().getCourseNo();
}

public void setCourseNo(String CourseNo){
    getCcid().setCourseNo(CourseNo);
}

public CatalogRequirements getCrFK(){
    return getCcid().getCrFK();
}

public void setCrFK(CatalogRequirements fk){
    getCcid().setCrFK(fk);
}
}

这是 CatalogCourseId 类

public class CatalogCourseId implements Serializable {

private String CourseNo;

@ManyToOne
CatalogRequirements crFK;

public String getCourseNo() {
    return CourseNo;
}

public void setCourseNo(String CourseNo) {
    this.CourseNo = CourseNo;
}

public CatalogRequirements getCrFK() {
    return crFK;
}

public void setCrFK(CatalogRequirements crFK) {
    this.crFK = crFK;
}

@Override
public int hashCode() {
    int hash = 7;
    hash = 37 * hash + Objects.hashCode(this.CourseNo);
    hash = 37 * hash + Objects.hashCode(this.crFK);
    return hash;
}

@Override
public boolean equals(Object obj) {
    if (obj == null) {
        return false;
    }
    if (getClass() != obj.getClass()) {
        return false;
    }
    final CatalogCourseId other = (CatalogCourseId) obj;
    if (!Objects.equals(this.CourseNo, other.CourseNo)) {
        return false;
    }
    if (!Objects.equals(this.crFK, other.crFK)) {
        return false;
    }
    return true;
}
}

hibernate 映射文件是

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD     3.0//EN" "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping package="com.javaknowledge.entity">
<class name="com.javaknowledge.entity.CatalogRequirements"       table="CatalogRequirements">
    <composite-id class="com.javaknowledge.entity.CatalogRequirementsId" mapped="true">
        <key-property name="semester" column="semester" ></key-property>
        <key-property name="year" column="year" ></key-property>
        <key-property name="program" column="program" ></key-property>
    </composite-id>
    <property name="GRE" column="GPA" />
    <property name="IELTS" column="ILETS" />
    <property name="TOEFL" column="TOFEL" />
    <property name="Backlogs" column="Backlogs" />
    <property name="PreRequisites1" column="Pre_requisite1" />
    <property name="PreRequisites2" column="Pre_requisite2" />
    <property name="compsMinGpa" column="compsmingpa" />
    <property name="compsMinHours" column="compsminHours" />
    <set name="catalogCourses" inverse="true" cascade="all">
        <key not-null="true">
            <column name="semester" ></column>
            <column name="year" ></column>
            <column name="program" ></column>
        </key>
        <one-to-many class="com.javaknowledge.entity.CatalogCourse"></one-to-many>
    </set>

</class>
</hibernate-mapping>

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE hibernate-mapping PUBLIC "-//Hibernate/Hibernate Mapping DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
 <class name="com.javaknowledge.entity.CatalogCourse" table="Catalog_Course">
     <id name="CourseNo" column="courseNum" type="string" ></id>
    <property name="CreditHours" column="Hours" />
    <property name="MinGrade" column="MIN_GPA" />
    <many-to-one name="catalogrequirements" class="com.javaknowledge.entity.CatalogRequirements" not-null="true">
            <column name="semester" />
            <column name="year" />
            <column name="program" />
    </many-to-one>
</class>
</hibernate-mapping>

hibernate 配置文件

<?xml version="1.0" encoding="UTF-8"?>
 <!DOCTYPE hibernate-configuration PUBLIC "-//Hibernate/Hibernate   Configuration DTD 3.0//EN" "http://hibernate.sourceforge.net/hibernate-  configuration-3.0.dtd">
<hibernate-configuration>
 <session-factory>
   <property name="hibernate.dialect">org.hibernate.dialect.MySQLDialect</property>
<property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property>
<property name="hibernate.connection.url">jdbc:mysql://localhost:3306/gdp</property>
<property name="hibernate.connection.username">root</property>
<property name="hbm2ddl.auto">update</property>
<property name="show_sql">true</property>
<mapping resource="com/javaknowledge/entity/CatalogRequirements.hbm.xml" />
<mapping resource="com/javaknowledge/entity/CatalogCourse.hbm.xml"/>
 </session-factory>
 </hibernate-configuration>

最后将记录保存到数据库的dao文件

public class CreateCatalogDao {

private CatalogCourse cc;
public void createCatalog(CatalogRequirements cust) {
    Transaction trns = null;
    Session session = HibernateUtil.createSessionFactory().openSession();
    try {
        trns = session.beginTransaction();
        session.save(cust);            
        trns.commit();

    } catch (RuntimeException e) {
        if (trns != null) {
            trns.rollback();
        }
    } finally {
        session.flush();
        session.close();
    }
}
}

记录正确存储在 CatalogRequirements 表中，但未存储在 Catalog_Course 中。我想问题出在 hbm 文件上。您还可以解释一下如何从 catalog_Course 表中检索值。

Answer 1

开始:您的 Entity 类都不应包含对其对应的 Id 类的引用(即 CatalogRequirements 不应引用 CatalogRequirementsId 和 CatalogCourse 不应引用 CatalogCourseId)。不要介意这些引用不应被注释为 @Id。 :-)

然后您需要使用派生身份。 CatalogCourse 类应该如下所示:

public class CatalogCourseId implements Serializable {
    private CatalogRequirementsId catalogRequirements;
    private String CourseNo;
    ...
}

@Entity
@IdClass(CatalogCourseId.class)
@Table(name="Catalog_Course")
public class CatalogCourse {
    @Id
    @ManyToOne
    @JoinColumns({
        @JoinColumn(name="semester", referencedColumnName="semester"),
        @JoinColumn(name="year", referencedColumnName="year"),
        @JoinColumn(name="program", referencedColumnName="program")
    })
    private CatalogRequirements catalogRequirements;

    @Id
    @Column(name="courseNum")
    private String courseNo;

    ...
}

请注意 IdClass 中的属性名称与 Entity 中的属性名称匹配(即 catalogRequirements)，但属性的类型不同.在 IdClass 中，属性类型必须匹配引用的 Entity 的 IdClass(即 CatalogRequirementsId)。

派生身份在 JPA 2.1 规范的第 2.4.1 节中进行了讨论。