惠州分享JPA查询对象函数实例_北大青鸟IT学校

为了让大家更好地理解JPA如何查询对象函数，惠州北大青鸟老师给大家分享JPA查询对象函数的实例，希望对大家学习Java有帮助。

实例

下面的代码来自Department.java。

package cn.w3cschool.common;

import java.util.HashSet;
import java.util.Set;

import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.OneToMany;

@Entitypublic class Department {
   @Id    private int id;    private String name;
   @OneToMany(mappedBy="department")    private Set<Professor> employees = new HashSet<Professor>();    public int getId() {
       return id;
   }    
   public void setId(int deptNo) {
       this.id = deptNo;
   }    
   public String getName() {
       return name;
   }    
   public void setName(String deptName) {
       this.name = deptName;
   }    
   public Set<Professor> getProfessors() {
       return employees;
   }    public String toString() {
       return "Department no: " + getId() +
              ", name: " + getName();
   }
}

以下代码来自Project.java。

package cn.w3cschool.common;

import java.util.ArrayList;
import java.util.Collection;

import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.Inheritance;
import javax.persistence.ManyToMany;

@Entity
@Inheritancepublic class Project {
   @Id    protected int id;    protected String name;
   @ManyToMany    protected Collection<Professor> employees = new ArrayList<Professor>();    
   public int getId() {
       return id;
   }    
   public void setId(int projectNo) {
       this.id = projectNo;
   }    
   public String getName() {
       return name;
   }    
   public void setName(String projectName) {
       this.name = projectName;
   }    
   public Collection<Professor> getProfessors() {
       return employees;
   }    
   public void addProfessor(Professor employee) {        if (!getProfessors().contains(employee)) {
           getProfessors().add(employee);
       }        if (!employee.getProjects().contains(this)) {
           employee.getProjects().add(this);
       }
   }    
   public String toString() {
       return getClass().getName().substring(getClass().getName().lastIndexOf(".")+1) +
               " no: " + getId() +
               ", name: " + getName();
   }
}

以下代码来自Phone.java。

package cn.w3cschool.common;

import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.ManyToOne;

@Entitypublic class Phone {
   @Id    private long id;    private String number;    private String type;
   @ManyToOne
   Professor employee;    
   public long getId() {
       return id;
   }    
   public void setId(long id) {
       this.id = id;
   }    
   public String getNumber() {
       return number;
   }    
   public void setNumber(String phoneNo) {
       this.number = phoneNo;
   }    
   public String getType() {
       return type;
   }    
   public void setType(String phoneType) {
       this.type = phoneType;
   }    
   public Professor getProfessor() {
       return employee;
   }    public void setProfessor(Professor employee) {
       this.employee = employee;
   }    public String toString() {
       return "Phone id: " + getId() +
              ", no: " + getNumber() +               ", type: " + getType();
   }
}

以下代码来自Address.java。

package cn.w3cschool.common;

import javax.persistence.Entity;
import javax.persistence.Id;

@Entitypublic class Address {
   @Id    private int id;    private String street;    private String city;    private String state;    private String zip;    
   public int getId() {
       return id;
   }    
   public void setId(int id) {
       this.id = id;
   }    
   public String getStreet() {
       return street;
   }    
   public void setStreet(String address) {
       this.street = address;
   }    public String getCity() {
       return city;
   }    public void setCity(String city) {
       this.city = city;
   }    public String getState() {
       return state;
   }    public void setState(String state) {
       this.state = state;
   }    public String getZip() {
       return zip;
   }    public void setZip(String zip) {
       this.zip = zip;
   }    public String toString() {
       return "Address id: " + getId() +
              ", street: " + getStreet() +               ", city: " + getCity() +               ", state: " + getState() +               ", zip: " + getZip();
   }

}

下面的代码来自PersonDaoImpl.java。

package cn.w3cschool.common;

import java.util.List;

import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;

import org.springframework.transaction.annotation.Transactional;

@Transactionalpublic class PersonDaoImpl {  public void test() {
   prepareData();
   
   List l = em.createQuery(        "SELECT OBJECT(d) FROM Department d")
       .getResultList();    for (Object p : l) {
     printResult(p);
   }
 }  private void prepareData() {
   Address address = new Address();
   address.setState("BC");
   
   Professor p = new Professor();
   p.setId(0);
   p.setName("TOM");
   p.setSalary(1111L);
   p.setAddress(address);

   Department d = new Department();
   d.setId(1);
   d.setName("Design");

   p.setDepartment(d);
   d.getProfessors().add(p);

   Phone phone = new Phone();
   phone.setId(1);
   phone.setNumber("111-111-1111");
   phone.setProfessor(p);
   
   em.persist(p);
   em.persist(phone);
   em.persist(address);
   em.persist(d);
 }  private static void printResult(Object result) {    if (result == null) {
     System.out.print("NULL");
   } else if (result instanceof Object[]) {
     Object[] row = (Object[]) result;
     System.out.print("[");      for (int i = 0; i < row.length; i++) {
       printResult(row[i]);
     }
     System.out.print("]");
   } else if (result instanceof Long || result instanceof Double
       || result instanceof String) {
     System.out.print(result.getClass().getName() + ": " + result);
   } else {
     System.out.print(result);
   }
   System.out.println();
 }

 @PersistenceContext  private EntityManager em;
}

以下代码来自Professor.java。

package cn.w3cschool.common;

import java.util.ArrayList;
import java.util.Collection;
import java.util.Date;

import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.ManyToMany;
import javax.persistence.ManyToOne;
import javax.persistence.OneToMany;
import javax.persistence.OneToOne;
import javax.persistence.Temporal;
import javax.persistence.TemporalType;

@Entitypublic class Professor {
   @Id    private int id;    private String name;    private long salary;
   @Temporal(TemporalType.DATE)    private Date startDate;
   
   @OneToOne    private Address address;
   
   @OneToMany(mappedBy="employee")    private Collection<Phone> phones = new ArrayList<Phone>();
   
   @ManyToOne    private Department department;
   
   @ManyToOne    private Professor manager;
   
   @OneToMany(mappedBy="manager")    private Collection<Professor> directs = new ArrayList<Professor>();
   
   @ManyToMany(mappedBy="employees")    private Collection<Project> projects = new ArrayList<Project>();    public int getId() {
       return id;
   }    
   public void setId(int empNo) {
       this.id = empNo;
   }    
   public String getName() {
       return name;
   }    
   public void setName(String name) {
       this.name = name;
   }    public long getSalary() {
       return salary;
   }    public void setSalary(long salary) {
       this.salary = salary;
   }    public Date getStartDate() {
       return startDate;
   }    public void setStartDate(Date startDate) {
       this.startDate = startDate;
   }    
   public Collection<Phone> getPhones() {
       return phones;
   }    
   public void addPhone(Phone phone) {        if (!getPhones().contains(phone)) {
           getPhones().add(phone);            if (phone.getProfessor() != null) {
               phone.getProfessor().getPhones().remove(phone);
           }
           phone.setProfessor(this);
       }
   }    
   public Department getDepartment() {
       return department;
   }    
   public void setDepartment(Department department) {        if (this.department != null) {
           this.department.getProfessors().remove(this);
       }
       this.department = department;
       this.department.getProfessors().add(this);
   }    
   public Collection<Professor> getDirects() {
       return directs;
   }    
   public void addDirect(Professor employee) {        if (!getDirects().contains(employee)) {
           getDirects().add(employee);            if (employee.getManager() != null) {
               employee.getManager().getDirects().remove(employee);
           }
           employee.setManager(this);
       }
   }    
   public Professor getManager() {
       return manager;
   }    
   public void setManager(Professor manager) {
       this.manager = manager;
   }    public Collection<Project> getProjects() {
       return projects;
   }    
   public void addProject(Project project) {        if (!getProjects().contains(project)) {
           getProjects().add(project);
       }        if (!project.getProfessors().contains(this)) {
           project.getProfessors().add(this);
       }
   }    
   public Address getAddress() {
       return address;
   }    
   public void setAddress(Address address) {
       this.address = address;
   }    
   public String toString() {
       return "Professor " + getId() +
              ": name: " + getName() +               ", salary: " + getSalary() +               ", phones: " + getPhones() +               ", managerNo: " + ((getManager() == null) ? null : getManager().getId()) +               ", deptNo: " + ((getDepartment() == null) ? null : getDepartment().getId());
   }

}

上面的代码生成以下结果。

以下是数据库转储。

Table Name: ADDRESS
Row:
   Column Name: ID,
   Column Type: INTEGER:
   Column Value: 0

   Column Name: CITY,
   Column Type: VARCHAR:
   Column Value: null

   Column Name: STATE,
   Column Type: VARCHAR:
   Column Value: BC

   Column Name: STREET,
   Column Type: VARCHAR:
   Column Value: null

   Column Name: ZIP,
   Column Type: VARCHAR:
   Column Value: null





Table Name: DEPARTMENT
Row:
   Column Name: ID,
   Column Type: INTEGER:
   Column Value: 1

   Column Name: NAME,
   Column Type: VARCHAR:
   Column Value: Design





Table Name: PHONE
Row:
   Column Name: ID,
   Column Type: BIGINT:
   Column Value: 1

   Column Name: NUMBER,
   Column Type: VARCHAR:
   Column Value: 111-111-1111

   Column Name: TYPE,
   Column Type: VARCHAR:
   Column Value: null

   Column Name: EMPLOYEE_ID,
   Column Type: INTEGER:
   Column Value: 0





Table Name: PROFESSOR
Row:
   Column Name: ID,
   Column Type: INTEGER:
   Column Value: 0

   Column Name: NAME,
   Column Type: VARCHAR:
   Column Value: TOM

   Column Name: SALARY,
   Column Type: BIGINT:
   Column Value: 1111

   Column Name: STARTDATE,
   Column Type: DATE:
   Column Value: null

   Column Name: ADDRESS_ID,
   Column Type: INTEGER:
   Column Value: 0

   Column Name: DEPARTMENT_ID,
   Column Type: INTEGER:
   Column Value: 1

   Column Name: MANAGER_ID,
   Column Type: INTEGER:
   Column Value: null





Table Name: PROJECT




Table Name: PROJECT_PROFESSOR

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