Java/JPA/Entity Lifecycle

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Lifecycle CallBack PreRemove

   <source lang="java">

File: Professor.java

import javax.persistence.Entity; import javax.persistence.EntityListeners; import javax.persistence.Id; import javax.persistence.PostLoad; import javax.persistence.PostPersist; import javax.persistence.PostUpdate; import javax.persistence.Transient; @Entity @EntityListeners({ProfessorDebugListener.class}) public class Professor { 

   @Id private int id;
   private String name;
   @Transient private long syncTime;
   @PostPersist 
   @PostUpdate
   @PostLoad 
   private void resetSyncTime() {
       syncTime = System.currentTimeMillis(); 
       System.out.println("Professor.resetSyncTime called on employee id: " + getId());
   }
   public long getCachedAge() {
       return System.currentTimeMillis() - syncTime; 
   }
   public int getId() {
       return id;
   }
   
   public void setId(int id) {
       this.id = id;
   }
   
   public String getName() {
       return name;
   }
   
   public void setName(String name) {
       this.name = name;
   }
   public String toString() {
       return "Professor id: " + getId() + " name: " + getName();
   }

}

File: ProfessorDebugListener.java import javax.persistence.PostLoad; import javax.persistence.PrePersist; import javax.persistence.PreRemove; import javax.persistence.PreUpdate; public class ProfessorDebugListener { 

 @PreRemove
 public void preRemove(Professor emp) {
   System.out.println("ProfessorDebugListener.Remove called on employee id: " + emp.getId());
 }

}

File: ProfessorService.java import java.util.Collection; import javax.persistence.EntityManager; import javax.persistence.Query; public class ProfessorService { 

 protected EntityManager em;
 public ProfessorService(EntityManager em) {
   this.em = em;
 }
 public Professor createProfessor(int id, String name) {
   Professor emp = new Professor();
   emp.setId(id);
   emp.setName(name);
   em.persist(emp);
   return emp;
 }
 public void removeProfessor(int id) {
   Professor emp = findProfessor(id);
   if (emp != null) {
     em.remove(emp);
   }
 }
 public Professor changeProfessorName(int id, String newName) {
   Professor emp = findProfessor(id);
   if (emp != null) {
     emp.setName(newName);
   }
   return emp;
 }
 public Professor findProfessor(int id) {
   return em.find(Professor.class, id);
 }
 public Collection<Professor> findAllProfessors() {
   Query query = em.createQuery("SELECT e FROM Professor e");
   return (Collection<Professor>) query.getResultList();
 }

}

File: JPAUtil.java import java.io.Reader; import java.sql.Connection; import java.sql.DriverManager; import java.sql.ResultSet; import java.sql.ResultSetMetaData; import java.sql.Statement; public class JPAUtil { 

 Statement st;
 
 public JPAUtil() throws Exception{
   Class.forName("org.hsqldb.jdbcDriver");
   System.out.println("Driver Loaded.");
   String url = "jdbc:hsqldb:data/tutorial";
   Connection conn = DriverManager.getConnection(url, "sa", "");
   System.out.println("Got Connection.");
   st = conn.createStatement();
 }
 public void executeSQLCommand(String sql) throws Exception {
   st.executeUpdate(sql);
 }
 public void checkData(String sql) throws Exception {
   ResultSet rs = st.executeQuery(sql);
   ResultSetMetaData metadata = rs.getMetaData();
   for (int i = 0; i < metadata.getColumnCount(); i++) {
     System.out.print("\t"+ metadata.getColumnLabel(i + 1)); 
   }
   System.out.println("\n----------------------------------");
   while (rs.next()) {
     for (int i = 0; i < metadata.getColumnCount(); i++) {
       Object value = rs.getObject(i + 1);
       if (value == null) {
         System.out.print("\t       ");
       } else {
         System.out.print("\t"+value.toString().trim());
       }
     }
     System.out.println("");
   }
 }

}

File: Main.java import javax.persistence.EntityManager; import javax.persistence.EntityManagerFactory; import javax.persistence.Persistence; public class Main { 

 public static void main(String[] a) throws Exception {
   JPAUtil util = new JPAUtil();
   EntityManagerFactory emf = Persistence.createEntityManagerFactory("ProfessorService");
   EntityManager em = emf.createEntityManager();
   ProfessorService service = new ProfessorService(em);
   em.getTransaction().begin();
   service.createProfessor(1, "name");
   for (Professor emp : service.findAllProfessors()) {
     System.out.print(emp);
   }
   service.changeProfessorName(1, "newname");
   for (Professor emp : service.findAllProfessors()) {
     System.out.print(emp);
   }
   service.removeProfessor(1);
   for (Professor emp : service.findAllProfessors()) {
     System.out.print(emp);
   }
   util.checkData("select * from Professor");
   em.getTransaction().rumit();
   em.close();
   emf.close();
 }

}


File: persistence.xml <persistence xmlns="http://java.sun.ru/xml/ns/persistence" 

            xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
            xsi:schemaLocation="http://java.sun.ru/xml/ns/persistence http://java.sun.ru/xml/ns/persistence/persistence" version="1.0">
 <persistence-unit name="JPAService" transaction-type="RESOURCE_LOCAL">
   <properties>
     <property name="hibernate.dialect" value="org.hibernate.dialect.HSQLDialect"/>
     <property name="hibernate.hbm2ddl.auto" value="update"/>
     <property name="hibernate.connection.driver_class" value="org.hsqldb.jdbcDriver"/>
     <property name="hibernate.connection.username" value="sa"/>
     <property name="hibernate.connection.password" value=""/>
     <property name="hibernate.connection.url" value="jdbc:hsqldb:data/tutorial"/>
   </properties>
 </persistence-unit>

</persistence> 


      </source>



Lifecycle CallBack PreUpdate

   <source lang="java">

File: Professor.java

import javax.persistence.Entity; import javax.persistence.EntityListeners; import javax.persistence.Id; import javax.persistence.PostLoad; import javax.persistence.PostPersist; import javax.persistence.PostUpdate; import javax.persistence.Transient; @Entity @EntityListeners({ProfessorDebugListener.class}) public class Professor { 

   @Id private int id;
   private String name;
   @Transient private long syncTime;
   @PostPersist 
   @PostUpdate
   @PostLoad 
   private void resetSyncTime() {
       syncTime = System.currentTimeMillis(); 
       System.out.println("Professor.resetSyncTime called on employee id: " + getId());
   }
   public long getCachedAge() {
       return System.currentTimeMillis() - syncTime; 
   }
   public int getId() {
       return id;
   }
   
   public void setId(int id) {
       this.id = id;
   }
   
   public String getName() {
       return name;
   }
   
   public void setName(String name) {
       this.name = name;
   }
   public String toString() {
       return "Professor id: " + getId() + " name: " + getName();
   }

}

File: ProfessorDebugListener.java import javax.persistence.PostLoad; import javax.persistence.PrePersist; import javax.persistence.PreRemove; import javax.persistence.PreUpdate; public class ProfessorDebugListener { 

 @PreUpdate
 public void preUpdate(Professor emp) {
   System.out.println("ProfessorDebugListener.Update called on employee id: " + emp.getId());
 }

}

File: ProfessorService.java import java.util.Collection; import javax.persistence.EntityManager; import javax.persistence.Query; public class ProfessorService { 

 protected EntityManager em;
 public ProfessorService(EntityManager em) {
   this.em = em;
 }
 public Professor createProfessor(int id, String name) {
   Professor emp = new Professor();
   emp.setId(id);
   emp.setName(name);
   em.persist(emp);
   return emp;
 }
 public void removeProfessor(int id) {
   Professor emp = findProfessor(id);
   if (emp != null) {
     em.remove(emp);
   }
 }
 public Professor changeProfessorName(int id, String newName) {
   Professor emp = findProfessor(id);
   if (emp != null) {
     emp.setName(newName);
   }
   return emp;
 }
 public Professor findProfessor(int id) {
   return em.find(Professor.class, id);
 }
 public Collection<Professor> findAllProfessors() {
   Query query = em.createQuery("SELECT e FROM Professor e");
   return (Collection<Professor>) query.getResultList();
 }

}

File: JPAUtil.java import java.io.Reader; import java.sql.Connection; import java.sql.DriverManager; import java.sql.ResultSet; import java.sql.ResultSetMetaData; import java.sql.Statement; public class JPAUtil { 

 Statement st;
 
 public JPAUtil() throws Exception{
   Class.forName("org.hsqldb.jdbcDriver");
   System.out.println("Driver Loaded.");
   String url = "jdbc:hsqldb:data/tutorial";
   Connection conn = DriverManager.getConnection(url, "sa", "");
   System.out.println("Got Connection.");
   st = conn.createStatement();
 }
 public void executeSQLCommand(String sql) throws Exception {
   st.executeUpdate(sql);
 }
 public void checkData(String sql) throws Exception {
   ResultSet rs = st.executeQuery(sql);
   ResultSetMetaData metadata = rs.getMetaData();
   for (int i = 0; i < metadata.getColumnCount(); i++) {
     System.out.print("\t"+ metadata.getColumnLabel(i + 1)); 
   }
   System.out.println("\n----------------------------------");
   while (rs.next()) {
     for (int i = 0; i < metadata.getColumnCount(); i++) {
       Object value = rs.getObject(i + 1);
       if (value == null) {
         System.out.print("\t       ");
       } else {
         System.out.print("\t"+value.toString().trim());
       }
     }
     System.out.println("");
   }
 }

}

File: Main.java import javax.persistence.EntityManager; import javax.persistence.EntityManagerFactory; import javax.persistence.Persistence; public class Main { 

 public static void main(String[] a) throws Exception {
   JPAUtil util = new JPAUtil();
   EntityManagerFactory emf = Persistence.createEntityManagerFactory("ProfessorService");
   EntityManager em = emf.createEntityManager();
   ProfessorService service = new ProfessorService(em);
   em.getTransaction().begin();
   service.createProfessor(1, "name");
   for (Professor emp : service.findAllProfessors()) {
     System.out.print(emp);
   }
   service.changeProfessorName(1, "newname");
   for (Professor emp : service.findAllProfessors()) {
     System.out.print(emp);
   }
   service.removeProfessor(1);
   for (Professor emp : service.findAllProfessors()) {
     System.out.print(emp);
   }
   util.checkData("select * from Professor");
   em.getTransaction().rumit();
   em.close();
   emf.close();
 }

}


File: persistence.xml <persistence xmlns="http://java.sun.ru/xml/ns/persistence" 

            xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
            xsi:schemaLocation="http://java.sun.ru/xml/ns/persistence http://java.sun.ru/xml/ns/persistence/persistence" version="1.0">
 <persistence-unit name="JPAService" transaction-type="RESOURCE_LOCAL">
   <properties>
     <property name="hibernate.dialect" value="org.hibernate.dialect.HSQLDialect"/>
     <property name="hibernate.hbm2ddl.auto" value="update"/>
     <property name="hibernate.connection.driver_class" value="org.hsqldb.jdbcDriver"/>
     <property name="hibernate.connection.username" value="sa"/>
     <property name="hibernate.connection.password" value=""/>
     <property name="hibernate.connection.url" value="jdbc:hsqldb:data/tutorial"/>
   </properties>
 </persistence-unit>

</persistence> 


      </source>



Lifecycle PostConstruct

   <source lang="java">

File: Department.java

import java.util.ArrayList; import java.util.Collection; import javax.persistence.Entity; import javax.persistence.Id; import javax.persistence.OneToMany; @Entity public class Department { 

   @Id
   private int id;
   private String name;
   @OneToMany(mappedBy="department")
   private Collection<Professor> employees;
   public Department() {
       employees = new ArrayList<Professor>();
   }
   
   public int getId() {
       return id;
   }
   
   public String getName() {
       return name;
   }
   
   public Collection<Professor> getProfessors() {
       return employees;
   }
   public String toString() {
       return "Department no: " + getId() + 
              ", name: " + getName();
   }

}

File: Professor.java

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.NamedQueries; import javax.persistence.NamedQuery; import javax.persistence.OneToMany; import javax.persistence.Temporal; import javax.persistence.TemporalType; @Entity @NamedQuery(name="findHighestPaidByDepartment", 

   query="SELECT e " +
         "FROM Professor e " +
         "WHERE e.department = :dept AND " +
         "      e.salary = (SELECT MAX(e2.salary) " +
         "                  FROM Professor e2 " +
         "                  WHERE e2.department = :dept)")

public class Professor { 

   @Id
   private int id;
   private String name;
   private long salary;
   @Temporal(TemporalType.DATE)
   private Date startDate;
   
   @ManyToOne
   private Professor manager;
   
   @OneToMany(mappedBy="manager")
   private Collection<Professor> directs;
   @ManyToOne
   private Department department;
   
   @ManyToMany 
   private Collection<Project> projects;
   public Professor() {
       projects = new ArrayList<Project>();
       directs = new ArrayList<Professor>();
   }
   public int getId() {
       return id;
   }
   
   public String getName() {
       return name;
   }
   public long getSalary() {
       return salary;
   }
   public Date getStartDate() {
       return startDate;
   }
   
   public Department getDepartment() {
       return department;
   }
   
   public Collection<Professor> getDirects() {
       return directs;
   }
   
   public Professor getManager() {
       return manager;
   }
   public Collection<Project> getProjects() {
       return projects;
   }
   
   public String toString() {
       return "Professor " + getId() + 
              ": name: " + getName() +
              ", salary: " + getSalary() +
              ", dept: " + ((getDepartment() == null) ? null : getDepartment().getName());
   }

}

File: ProfessorService.java import javax.annotation.PostConstruct; import javax.persistence.EntityManager; import javax.persistence.Query; public class ProfessorService { 

 protected EntityManager em;
 public ProfessorService(EntityManager em) {
   this.em = em;
 }
 Query unassignedQuery;
 
 @PostConstruct
 public void init() {
     System.out.println("post constructed\n\n\n\n\n\n\n\n");
     unassignedQuery = 
         em.createQuery("SELECT e " +
                        "FROM Professor e " +
                        "WHERE e.projects IS EMPTY");
 }

}

File: Project.java

import java.util.ArrayList; import java.util.Collection; import javax.persistence.Entity; import javax.persistence.Id; import javax.persistence.ManyToMany; @Entity public class Project { 

   @Id
   protected int id;
   protected String name;
   @ManyToMany(mappedBy="projects")
   private Collection<Professor> employees;
   public Project() {
       employees = new ArrayList<Professor>();
   }
   public int getId() {
       return id;
   }
   
   public String getName() {
       return name;
   }
   
   public Collection<Professor> getProfessors() {
       return employees;
   }
   
   public String toString() {
       return "Project id: " + getId() + ", name: " + getName();
   }

}

File: JPAUtil.java import java.io.Reader; import java.sql.Connection; import java.sql.DriverManager; import java.sql.ResultSet; import java.sql.ResultSetMetaData; import java.sql.Statement; public class JPAUtil { 

 Statement st;
 
 public JPAUtil() throws Exception{
   Class.forName("org.hsqldb.jdbcDriver");
   System.out.println("Driver Loaded.");
   String url = "jdbc:hsqldb:data/tutorial";
   Connection conn = DriverManager.getConnection(url, "sa", "");
   System.out.println("Got Connection.");
   st = conn.createStatement();
 }
 public void executeSQLCommand(String sql) throws Exception {
   st.executeUpdate(sql);
 }
 public void checkData(String sql) throws Exception {
   ResultSet rs = st.executeQuery(sql);
   ResultSetMetaData metadata = rs.getMetaData();
   for (int i = 0; i < metadata.getColumnCount(); i++) {
     System.out.print("\t"+ metadata.getColumnLabel(i + 1)); 
   }
   System.out.println("\n----------------------------------");
   while (rs.next()) {
     for (int i = 0; i < metadata.getColumnCount(); i++) {
       Object value = rs.getObject(i + 1);
       if (value == null) {
         System.out.print("\t       ");
       } else {
         System.out.print("\t"+value.toString().trim());
       }
     }
     System.out.println("");
   }
 }

}

File: Main.java import java.util.Collection; import java.util.Date; import javax.persistence.EntityManager; import javax.persistence.EntityManagerFactory; import javax.persistence.Persistence; public class Main { 

 public static void main(String[] a) throws Exception {
   JPAUtil util = new JPAUtil();
   EntityManagerFactory emf = Persistence.createEntityManagerFactory("ProfessorService");
   EntityManager em = emf.createEntityManager();
   ProfessorService service = new ProfessorService(em);
   em.getTransaction().begin();
  
   util.checkData("select * from Professor");
   util.checkData("select * from Department");
   
   em.getTransaction().rumit();
   em.close();
   emf.close();
 }

}


File: persistence.xml <persistence xmlns="http://java.sun.ru/xml/ns/persistence" 

            xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
            xsi:schemaLocation="http://java.sun.ru/xml/ns/persistence http://java.sun.ru/xml/ns/persistence/persistence" version="1.0">
 <persistence-unit name="JPAService" transaction-type="RESOURCE_LOCAL">
   <properties>
     <property name="hibernate.dialect" value="org.hibernate.dialect.HSQLDialect"/>
     <property name="hibernate.hbm2ddl.auto" value="update"/>
     <property name="hibernate.connection.driver_class" value="org.hsqldb.jdbcDriver"/>
     <property name="hibernate.connection.username" value="sa"/>
     <property name="hibernate.connection.password" value=""/>
     <property name="hibernate.connection.url" value="jdbc:hsqldb:data/tutorial"/>
   </properties>
 </persistence-unit>

</persistence> 

      </source>
Источник — «http://www.jexp.ru/index.php?title=Java/JPA/Entity_Lifecycle&oldid=8967»