我正在使用 Java 中的 Hibernate、Spring 和 GWT 开发应用程序。我在 Hibernate（使用 JBoss Developer Studio）下使用逆向工程从现有的 MySQL 数据库中获取 POJO 和配置文件。这是一个非常简单的数据库，只有两个实体：Country 和 Citizen。它们之间有 OneToMany 关系。
这是代码：
应用入口点：
...
Country country = new Country();
country.setName("NameOfCountry"+i);
country.setPopulation(10000);
Citizen ctz = new Citizen();
ctz.setName("John");
ctz.setSurname("Smith");
ctz.setCountry(country);
country.getCitizens().add(ctz);
service.saveCitizen(ctz, new AsyncCallback<Boolean>(){
@Override
public void onFailure(Throwable caught) {
System.out.println("Problem saving citizen");
}
@Override
public void onSuccess(Boolean result) {
System.out.println("Citizen successfully saved");
}
});
service.saveCountry(country, new AsyncCallback<Boolean>(){
@Override
public void onFailure(Throwable caught) {
System.out.println("Problem saving country");
}
@Override
public void onSuccess(Boolean result) {
System.out.println("Country successfully saved");
}
});
...
-- 服务提供对服务器的简单 GWT-RPC 调用
服务器上的服务：
@Service("componentService")
public class ComponentServiceImpl implements ComponentService{
@Autowired
private CountryDAO daoCnt;
@Autowired
private CitizenDAO daoCtz;
@Transactional(readOnly=false)
@Override
public boolean saveCitizen(Citizen citizen) {
daoCtz.saveOrUpdate(citizen);
return true;
}
@Transactional(readOnly=false)
@Override
public boolean saveCountry(Country country) {
daoCnt.saveOrUpdate(country);
return true;
}
}
现在 SpringDAO：
公民道：
@Repository
public class CitizenDAO {
...
public void saveOrUpdate(Citizen citizen){
sessionFactory.getCurrentSession().saveOrUpdate(citizen);
}
...
国家DAO：
@Repository
public class CountryDAO {
...
public void saveOrUpdate(Country country){
sessionFactory.getCurrentSession().saveOrUpdate(country);
}
...
最后
公民.hbm.xml：
<hibernate-mapping>
<class name="sk.jakub.mod.shared.model.Citizen" table="citizen" catalog="modeldb">
<id name="id" type="java.lang.Integer">
<column name="id" />
<generator class="identity" />
</id>
<many-to-one name="country" class="sk.jakub.mod.shared.model.Country" fetch="select">
<column name="Country_id" not-null="true" />
</many-to-one>
<property name="name" type="string">
<column name="name" length="45" not-null="true" />
</property>
<property name="surname" type="string">
<column name="surname" length="45" not-null="true" />
</property>
</class>
</hibernate-mapping>
国家.hbm.xml：
<hibernate-mapping>
<class name="sk.jakub.mod.shared.model.Country" table="country" catalog="modeldb">
<id name="id" type="java.lang.Integer">
<column name="id" />
<generator class="identity" />
</id>
<property name="name" type="string">
<column name="name" length="45" not-null="true" />
</property>
<property name="population" type="int">
<column name="population" not-null="true" />
</property>
<set name="citizens" table="citizen" inverse="true" lazy="true" fetch="select">
<key>
<column name="Country_id" not-null="true" />
</key>
<one-to-many class="sk.jakub.mod.shared.model.Citizen" />
</set>
</class>
</hibernate-mapping>
我没有列出 Citizen.java 和 Country.java 因为它们只是基本的 POJO（如果有必要我会提供它们）。
当我启动我的应用程序并且我想将我的数据保存到数据库中时，我收到以下错误：
org.hibernate.PropertyValueException: not-null property references a null or transient value: sk.jakub.mod.shared.model.Citizen.country
我无法弄清楚问题出在哪里。我也在尝试而不是 saveOrUpdate 方法，persist 方法。或者也改变保存到数据库的顺序。似乎没有任何效果。
非常感谢您的帮助 :) 如果需要，我可以从我的应用程序中发布更多代码。
编辑：Citizen.java 的代码：
public class Citizen implements java.io.Serializable {
private static final long serialVersionUID = -3102863479088406293L;
private Integer id;
private Country country;
private String name;
private String surname;
public Citizen() {
}
public Citizen(Country country, String name, String surname) {
this.country = country;
this.name = name;
this.surname = surname;
}
public Integer getId() {
return this.id;
}
public void setId(Integer id) {
this.id = id;
}
public Stat getCountry() {
return this.country;
}
public void setCountry(Country country) {
this.country = country;
}
public String getName() {
return this.name;
}
public void setName(String name) {
this.name = name;
}
public String getSurname() {
return this.surname;
}
public void setSurname(String surname) {
this.surname = surname;
}
}
国家.java：
public class Country implements java.io.Serializable {
private static final long serialVersionUID = -4085805854508658303L;
private Integer id;
private String name;
private int population;
private Set<Citizen> citizens = new HashSet<Citizen>();
public Country() {
}
public Country(String name, int population) {
this.name = name;
this.population = population;
}
public Country(String name, int population, Set<Citizen> citizens) {
this.name = name;
this.population = population;
this.citizens = citizens;
}
public Integer getId() {
return this.id;
}
public void setId(Integer id) {
this.id = id;
}
public String getName() {
return this.name;
}
public void setName(String name) {
this.name = name;
}
public int getPopulation() {
return this.population;
}
public void setPopulation(int population) {
this.population = population;
}
public Set<Citizen> getCitizens() {
return this.citizens;
}
public void setCitizens(Set<Citizen> citizens) {
this.citizens = citizens;
}
}
此外，我手动检查了数据库并保存了国家，但没有保存公民。