Java by API/javax.persistence/QueryHint

QueryHint.name()

   <source lang="java">
 

File: Professor.java

import javax.persistence.Entity; import javax.persistence.Id; import javax.persistence.NamedQuery; import javax.persistence.QueryHint; @Entity @NamedQuery(name="findProfessorNoCache",

           query="SELECT e FROM Professor e WHERE e.id = ?1",
           hints={@QueryHint(name="toplink.cache-usage", value="DoNotCheckCache")})

public class Professor {

   @Id
   private int id;
   private String name;
   private long salary;
   public int getId() {
       return id;
   }
   
   public String getName() {
       return name;
   }
   public long getSalary() {
       return salary;
   }
   
   public String toString() {
       return "Professor " + getId() + 
              ": name: " + getName() +
              ", salary: " + getSalary();
   }

}

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

 protected EntityManager em;
 public ProfessorService(EntityManager em) {
   this.em = em;
 }
 public Professor findProfessor(int empId) {
   Query q = em.createQuery("SELECT e FROM Professor e WHERE e.id =  ?1");
   q.setParameter(1, empId);
   try {
     return (Professor) q.getSingleResult();
   } catch (NoResultException e) {
     return null;
   }
 }
 public Professor findProfessorNoCache(int empId) {
   Query q = em.createQuery("SELECT e FROM Professor e WHERE e.id = ?1");
   // force read from database
   q.setHint("cacheUsage", oracle.toplink.essentials.queryframework.ObjectLevelReadQuery.DoNotCheckCache);
   q.setParameter(1, empId);
   try {
     return (Professor) q.getSingleResult();
   } catch (NoResultException e) {
     return null;
   }
 }
 public Professor findProfessorNoCacheNamed(int empId) {
   Query q = em.createNamedQuery("findProfessorNoCache");
   q.setParameter(1, empId);
   try {
     return (Professor) q.getSingleResult();
   } catch (NoResultException e) {
     return null;
   }
 }
 public Collection<Professor> findAllProfessors() {
   return (Collection<Professor>) em.createQuery("SELECT e FROM Professor e").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.removeDepartment2();
   
   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>
   
  
 
  

QueryHint.value()

   <source lang="java">
 

File: Professor.java

import javax.persistence.Entity; import javax.persistence.Id; import javax.persistence.NamedQuery; import javax.persistence.QueryHint; @Entity @NamedQuery(name="findProfessorNoCache",

           query="SELECT e FROM Professor e WHERE e.id = ?1",
           hints={@QueryHint(name="toplink.cache-usage", value="DoNotCheckCache")})

public class Professor {

   @Id
   private int id;
   private String name;
   private long salary;
   public int getId() {
       return id;
   }
   
   public String getName() {
       return name;
   }
   public long getSalary() {
       return salary;
   }
   
   public String toString() {
       return "Professor " + getId() + 
              ": name: " + getName() +
              ", salary: " + getSalary();
   }

}

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

 protected EntityManager em;
 public ProfessorService(EntityManager em) {
   this.em = em;
 }
 public Professor findProfessor(int empId) {
   Query q = em.createQuery("SELECT e FROM Professor e WHERE e.id =  ?1");
   q.setParameter(1, empId);
   try {
     return (Professor) q.getSingleResult();
   } catch (NoResultException e) {
     return null;
   }
 }
 public Professor findProfessorNoCache(int empId) {
   Query q = em.createQuery("SELECT e FROM Professor e WHERE e.id = ?1");
   // force read from database
   q.setHint("cacheUsage", oracle.toplink.essentials.queryframework.ObjectLevelReadQuery.DoNotCheckCache);
   q.setParameter(1, empId);
   try {
     return (Professor) q.getSingleResult();
   } catch (NoResultException e) {
     return null;
   }
 }
 public Professor findProfessorNoCacheNamed(int empId) {
   Query q = em.createNamedQuery("findProfessorNoCache");
   q.setParameter(1, empId);
   try {
     return (Professor) q.getSingleResult();
   } catch (NoResultException e) {
     return null;
   }
 }
 public Collection<Professor> findAllProfessors() {
   return (Collection<Professor>) em.createQuery("SELECT e FROM Professor e").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.removeDepartment2();
   
   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>