Java @在实体bean中插入时不会自动设置Id
我有一个相当简单的EJB应用程序,它包括 一个实体Bean:Java @在实体bean中插入时不会自动设置Id,java,mysql,hibernate,jboss,ejb,Java,Mysql,Hibernate,Jboss,Ejb,我有一个相当简单的EJB应用程序,它包括 一个实体Bean: import java.io.Serializable; import java.util.Date; import javax.persistence.Column; import javax.persistence.Entity; import javax.persistence.GeneratedValue; import javax.persistence.GenerationType; import javax.persi
import java.io.Serializable;
import java.util.Date;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
@Entity
public class Employee implements Serializable {
private static final long serialVersionUID = -8450766960140252704L;
@Id
@GeneratedValue(strategy=GenerationType.IDENTITY)
@Column(name="employee_number", nullable=false)
private int employeeNumber;
private String firstname;
private String inital;
private String lastname;
private int age;
private Date birthday;
private String street;
@Column(name="house_number")
private String houseNumber;
private String postalcode;
private String city;
private String department;
@Column(name="sallery_group")
private String salleryGroup;
public int getEmployeeNumber() {
return employeeNumber;
}
public void setEmployeeNumber(int employeeNumber) {
this.employeeNumber = employeeNumber;
}
public String getFirstname() {
return firstname;
}
public void setFirstname(String firstname) {
this.firstname = firstname;
}
public String getInital() {
return inital;
}
public void setInital(String inital) {
this.inital = inital;
}
public String getLastname() {
return lastname;
}
public void setLastname(String lastname) {
this.lastname = lastname;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public Date getBirthday() {
return birthday;
}
public void setBirthday(Date birthday) {
this.birthday = birthday;
}
public String getStreet() {
return street;
}
public void setStreet(String street) {
this.street = street;
}
public String getHouseNumber() {
return houseNumber;
}
public void setHouseNumber(String houseNumber) {
this.houseNumber = houseNumber;
}
public String getPostalcode() {
return postalcode;
}
public void setPostalcode(String postalcode) {
this.postalcode = postalcode;
}
public String getCity() {
return city;
}
public void setCity(String city) {
this.city = city;
}
public String getDepartment() {
return department;
}
public void setDepartment(String department) {
this.department = department;
}
public String getSalleryGroup() {
return salleryGroup;
}
public void setSalleryGroup(String salleryGroup) {
this.salleryGroup = salleryGroup;
}
@Override
public String toString() {
StringBuffer sb = new StringBuffer();
sb.append("Employee Number: " + this.getEmployeeNumber() + "\n");
sb.append("Firstname: " + this.getFirstname() + "\n");
sb.append("Inital: " + this.getInital() + "\n");
sb.append("Lastname: " + this.getLastname() + "\n");
sb.append("Age: " + this.getAge() + "\n");
sb.append("Birthday: " + this.getBirthday() + "\n");
sb.append("Street: " + this.getStreet() + "\n");
sb.append("House Number: " + this.getHouseNumber() + "\n");
sb.append("Postalcode: " + this.getPostalcode() + "\n");
sb.append("City: " + this.getCity() + "\n");
sb.append("Department: " + this.getDepartment() + "\n");
sb.append("Sallery Group: " + this.getSalleryGroup() + "\n");
return sb.toString();
}
@Override
public boolean equals(Object obj) {
if(obj == null || this.getClass() != obj.getClass())
{
return false;
}
else if (obj == this)
{
return true;
}
else
{
Employee employee = (Employee)obj;
return (
((this.getFirstname() == null && employee.getFirstname() == null) || (this.getFirstname().equals(employee.getFirstname()))) &&
((this.getInital() == null && employee.getInital() == null) || (this.getInital().equals(employee.getInital()))) &&
((this.getLastname() == null && employee.getLastname() == null) || (this.getLastname().equals(employee.getLastname()))) &&
this.getAge() == employee.getAge() &&
((this.getBirthday() == null && employee.getBirthday() == null) || (this.getBirthday().equals(employee.getBirthday()))) &&
((this.getStreet() == null && employee.getStreet() == null) || (this.getStreet().equals(employee.getStreet()))) &&
((this.getHouseNumber() == null && employee.getHouseNumber() == null) || (this.getHouseNumber().equals(employee.getHouseNumber()))) &&
((this.getPostalcode() == null && employee.getPostalcode() == null) || (this.getPostalcode().equals(employee.getPostalcode()))) &&
((this.getCity() == null && employee.getCity() == null) || (this.getCity().equals(employee.getCity()))) &&
((this.getDepartment() == null && employee.getDepartment() == null) || (this.getDepartment().equals(employee.getDepartment()))) &&
((this.getSalleryGroup() == null && employee.getSalleryGroup() == null) || (this.getSalleryGroup().equals(employee.getSalleryGroup()))));
}
}
}
一个会话Bean
import javax.ejb.Stateless;
import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;
@Stateless
public class EmployeeManagementBean implements EmployeeManagement {
@PersistenceContext(unitName="EmployeePersistenceUnit")
private EntityManager entityManager;
@Override
public Employee create() {
return new Employee();
}
@Override
public void store(Employee employee) {
entityManager.persist(employee);
}
@Override
public Employee findEmployeeWithNumber(int employeeNumber) {
return entityManager.find(Employee.class, employeeNumber);
}
}
在我的客户机中,我只需在会话bean上调用create(),设置所有属性,除了在我的例子中是employeeNumber的id字段。然后调用store()并将对象传递给会话bean。然后,对象被适当地存储在数据库中,主键由mysql数据库自动生成
问题
我的问题是,生成的id没有传递回对象。因此,在调用store()和entityManager.persist()之后,对getEmployeeNumber()的调用始终返回0。根据我在网上读到的很多东西,@Id字段应该由数据库生成的Id自动填充。希望有人能帮我。entityManager.flush()无法解决此问题
更多详细信息
我正在使用JBoss7.1.0和MySQL 5.6。MySQL JDBC驱动程序放在部署文件夹中
persistence.xml
<?xml version="1.0" encoding="UTF-8"?>
<persistence version="2.0" xmlns="http://java.sun.com/xml/ns/persistence"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/persistence
http://java.sun.com/xml/ns/persistence/persistence_2_0.xsd">
<persistence-unit name="EmployeePersistenceUnit" transaction-type="JTA">
<provider>org.hibernate.ejb.HibernatePersistence</provider>
<jta-data-source>java:jboss/datasources/MySQLEmployeeManagementDS</jta-data-source>
</persistence-unit>
<datasource jndi-name="java:jboss/datasources/MySQLEmployeeManagementDS" pool-name="MySQLEmployeeManagementDS" enabled="true" jta="true" use-java-context="true" use-ccm="true">
<connection-url>
jdbc:mysql://localhost:3306/employee_management
</connection-url>
<driver>
mysql-connector-java-5.1.25.jar
</driver>
<pool>
<min-pool-size>
10
</min-pool-size>
<max-pool-size>
100
</max-pool-size>
<prefill>
true
</prefill>
<use-strict-min>
false
</use-strict-min>
<flush-strategy>
FailingConnectionOnly
</flush-strategy>
</pool>
<security>
<user-name>
root
</user-name>
<password>
test
</password>
</security>
</datasource>
<drivers>
<driver name="mysql-connector-java-5.1.25.jar" module="com.mysql">
<xa-datasource-class>
com.mysql.jdbc.jdbc2.optional.MysqlXADataSource
</xa-datasource-class>
</driver>
</drivers>
我相信你观察到的行为是正确的。使用GenerationType.IDENTITY或GenerationType.SEQUENCE策略时,在插入行之前,id值是未知的 如果在持久化实体后立即需要该值,则必须调用EntityManager.flush()以强制与数据库同步,然后检索对象-此时它将设置id 您也可以尝试使用HQL查询,而不是查找方法
Query q = em.createQuery("select e from Employee where e.id = :id");
q.setId(employeeNumber);
return q.getSingleResult()
如果将EJB与远程接口一起使用,则可能会出现另一个问题。假设以下流程
public Employee store(Employee employee) {
entityManager.persist(employee);
entityManager.flush();
return employee; //employee should have id set to the DB value
}
你以前的雇员号码是多少?0还是空?employeeNumber是否设置为PK???由于实体bean中的employeeNumber的类型为int,因此它从一开始就是0,并且从不更改。据我所知,int不可能为Null,是的,employe_number是数据库中的列,它被设置为PKYou是正确的,我通常使用Long表示id,使用Long代替int表示id是一种很好的做法。。。我的第三个问题呢?您是否将employeeNumber设置为PK?是的,请参见上面的附加列表:)您让hibernate和mysql为记录生成主键。我不知道这是否是问题所在,但您可以检查它(例如,通过从创建表脚本中删除自动增量)。正如我所提到的,我已准备好尝试调用flush,因为我在其他几个关于同一问题的主题中发现了这一点。遗憾的是,它不起作用。还有其他提示吗?您是否尝试使用HQL查询代替find(),请参阅更新的答案您的查询不需要我知道id吗?这正是我的问题,我无法访问新插入对象的id:(非常好的解释。非常感谢。它通过返回对象解决了我的问题:-)它甚至在没有刷新的情况下工作。有什么更好的方法?我想用flush来确保上下文和数据库同步?
public Employee store(Employee employee) {
entityManager.persist(employee);
entityManager.flush();
return employee; //employee should have id set to the DB value
}