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。
最佳答案
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。
关于java - 如何为具有复合主键和外键的 oneToMany 关系创建 Hibernate 映射文件?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/31253040/