Java Spring MVC-在控制器中默认设置值

根据以下映射（在问题的底部），我需要知道如何在Employee类中的“department\u id”中设置特定值

Employee             
--------------------------------------------
id  | firstname  | lastname | department_id
--------------------------------------------
1   | David      | Smith    |     1 


Department              
-----------
id  | name
-----------
1   | Dep A
2   | Dep B
3   | Dep C

saveEmployee方法（EmployeeController类）：

@RequestMapping(value = "/saveEmployee", method = RequestMethod.POST)
public String saveEmployee(@ModelAttribute("employee") Employee employee){
    /*  I need to set the department "id" (foreign key) into the Employee
table directly in this method. */
    int id = 1; // 2 or 3...
    /* The "department_id" in the Employee class should 
       to receive the "id" value. */
    employee.setDepartment(id); // It does not work.
    employeeService.saveEmployee(employee);
    return "redirect:/employees";
}

@Entity
public class Employee{
    @Id
    @GeneratedValue(strategy=GenerationType.AUTO)
    private int id;
    private String firstname;
    private String lastname;

    @ManyToOne
    @JoinColumn(name = "department_id")
    private Department department;
    // Getters and Setters
}

@Entity
public class Department{
    @Id
    @GeneratedValue(strategy=GenerationType.AUTO)
    private int id;
    private String name;
    // Getters and Setters
}

员工类别：

@RequestMapping(value = "/saveEmployee", method = RequestMethod.POST)
public String saveEmployee(@ModelAttribute("employee") Employee employee){
    /*  I need to set the department "id" (foreign key) into the Employee
table directly in this method. */
    int id = 1; // 2 or 3...
    /* The "department_id" in the Employee class should 
       to receive the "id" value. */
    employee.setDepartment(id); // It does not work.
    employeeService.saveEmployee(employee);
    return "redirect:/employees";
}

@Entity
public class Employee{
    @Id
    @GeneratedValue(strategy=GenerationType.AUTO)
    private int id;
    private String firstname;
    private String lastname;

    @ManyToOne
    @JoinColumn(name = "department_id")
    private Department department;
    // Getters and Setters
}

@Entity
public class Department{
    @Id
    @GeneratedValue(strategy=GenerationType.AUTO)
    private int id;
    private String name;
    // Getters and Setters
}

系级：

@RequestMapping(value = "/saveEmployee", method = RequestMethod.POST)
public String saveEmployee(@ModelAttribute("employee") Employee employee){
    /*  I need to set the department "id" (foreign key) into the Employee
table directly in this method. */
    int id = 1; // 2 or 3...
    /* The "department_id" in the Employee class should 
       to receive the "id" value. */
    employee.setDepartment(id); // It does not work.
    employeeService.saveEmployee(employee);
    return "redirect:/employees";
}

@Entity
public class Employee{
    @Id
    @GeneratedValue(strategy=GenerationType.AUTO)
    private int id;
    private String firstname;
    private String lastname;

    @ManyToOne
    @JoinColumn(name = "department_id")
    private Department department;
    // Getters and Setters
}

@Entity
public class Department{
    @Id
    @GeneratedValue(strategy=GenerationType.AUTO)
    private int id;
    private String name;
    // Getters and Setters
}

---

实际上，您的setDepartment接收到一个Department实例。所以你必须这样做：

int id = 1; 
Department department = new Department(); //Or you can use Autowired
department.setId(id); // Set Id Department
employee.setDepartment(department); // A Department instance
employeeService.saveEmployee(employee);
return "redirect:/employees";

---

仔细查看您的

员工

班级：

@Entity
public class Employee{
    ...

    @ManyToOne
    @JoinColumn(name = "department_id")
    private Department department;
    /* THIS IS NOT AN INTEGER DATA TYPE, IT'S A DEPARTMENT DATA TYPE. 
    SO THE SETTER FOR THIS WILL LOOK SOMEWHAT LIKE THIS:*/

    //Setter
    public void setDepartment(Department department) {
        this.department = department
    }

    ...
    // Getters and Setters
}

要设置

部门

请创建您的

部门

的实例，然后通过setter发送：

@RequestMapping(value = "/saveEmployee", method = RequestMethod.POST)
public String saveEmployee(@ModelAttribute("employee") Employee employee){
    int id = 1; // 2 or 3...

    Department temporaryDepartment = new Department();
    temporaryDepartment.setId(id);

    employee.setDepartment(temporaryDepartment); 
    employeeService.saveEmployee(employee);
    return "redirect:/employees";
}

---

实际上，您已经设置了如下所示的生成策略

@Id
    @GeneratedValue(strategy=GenerationType.AUTO) 

在

Department

类上，这意味着您希望hibernate为您生成id，这样您就不必担心设置部门id。您只需要设置部门名称

下面是工作代码，

JPAEmployeeTest.java

：

package com.chatar.hibernate.receipes.example;

import javax.persistence.EntityManager;
import javax.persistence.EntityManagerFactory;
import javax.persistence.Persistence;

import com.chatar.hibernate.receipes.example.domain.annotations.Department;
import com.chatar.hibernate.receipes.example.domain.annotations.Employee;

public class JPAEmployeeTest {

    public static void main(String[] args) {
        EntityManagerFactory entityManagerFactory = Persistence.createEntityManagerFactory( "employee" );

        EntityManager entityManager = entityManagerFactory.createEntityManager();
        entityManager.getTransaction().begin();

        Employee employee = new Employee();
        Department department = new Department();
        department.setName("Engineering");

        employee.setFirstName("Johny");
        employee.setLastName("Walker");
        employee.setDepartment(department);

        entityManager.persist(employee);

        entityManager.getTransaction().commit();

        entityManager.close();

    }
}

和我的域对象，

Employee.java

package com.chatar.hibernate.receipes.example.domain.annotations;

import java.io.Serializable;

import javax.persistence.CascadeType;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.ManyToOne;

@Entity
public class Employee implements Serializable {

    private static final long serialVersionUID = -5641563180459243167L;

    @Id
    @GeneratedValue(strategy = GenerationType.TABLE)
    private long id;

    @Column(name = "first_name")
    private String firstName;

    @Column(name = "last_name")
    private String lastName;

    @ManyToOne(cascade=CascadeType.ALL)
    @JoinColumn(name = "department_id" )
    private Department department;

    public long getId() {
        return id;
    }

    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 Department getDepartment() {
        return department;
    }

    public void setDepartment(Department department) {
        this.department = department;
    }
}

package com.chatar.hibernate.receipes.example.domain.annotations;

import java.io.Serializable;

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;

@Entity
public class Department implements Serializable {

    private static final long serialVersionUID = -598469568850009702L;
    @Id
    @GeneratedValue(strategy = GenerationType.TABLE)
    private long id;
    private String name;

    public long getId() {
        return id;
    }

    public void setId(long id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

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

和

Department.java

package com.chatar.hibernate.receipes.example.domain.annotations;

import java.io.Serializable;

import javax.persistence.CascadeType;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.JoinColumn;
import javax.persistence.ManyToOne;

@Entity
public class Employee implements Serializable {

    private static final long serialVersionUID = -5641563180459243167L;

    @Id
    @GeneratedValue(strategy = GenerationType.TABLE)
    private long id;

    @Column(name = "first_name")
    private String firstName;

    @Column(name = "last_name")
    private String lastName;

    @ManyToOne(cascade=CascadeType.ALL)
    @JoinColumn(name = "department_id" )
    private Department department;

    public long getId() {
        return id;
    }

    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 Department getDepartment() {
        return department;
    }

    public void setDepartment(Department department) {
        this.department = department;
    }
}

package com.chatar.hibernate.receipes.example.domain.annotations;

import java.io.Serializable;

import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;

@Entity
public class Department implements Serializable {

    private static final long serialVersionUID = -598469568850009702L;
    @Id
    @GeneratedValue(strategy = GenerationType.TABLE)
    private long id;
    private String name;

    public long getId() {
        return id;
    }

    public void setId(long id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

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

My

persistence.xml

<?xml version="1.0" encoding="UTF-8"?>
<persistence 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_1_0.xsd"
   version="1.0">

   <persistence-unit name="employee" transaction-type="RESOURCE_LOCAL">
                             <provider>org.hibernate.ejb.HibernatePersistence</provider>
      <class>com.chatar.hibernate.receipes.example.domain.annotations.Employee</class>
      <class>com.chatar.hibernate.receipes.example.domain.annotations.Department</class>

      <properties>
       <property name="javax.persistence.jdbc.driver"
            value = "org.apache.derby.jdbc.EmbeddedDriver"/>
        <property name="javax.persistence.jdbc.url" value = "jdbc:derby://localhost:1527/BookShopDB" />
        <property name="javax.persistence.jdbc.user" value="book" />
        <property name="javax.persistence.jdbc.password" value = "book" />
        <property name="hibernate.dialect" value = "org.hibernate.dialect.DerbyDialect" />
     </properties>

   </persistence-unit>
</persistence>

注意-我使用的是

GenerationType.TABLE

，因为

AUTO

不适用于我的数据库，即

Debry

。此外，我还设置了

CascadeType.ALL

，这样当我保存

Employee

实体时，Hibernate会保存所有引用实体，例如我的案例中的

Department