SwanBear: Generic CRUD DAO

Thursday, August 31, 2006

Generic CRUD DAO

這是參考Don't repeat the DAO!這篇文章前面一部分的note
單純運用Java 5.0 Generic、Spring、Hibernate
後面還有加入AOP的部份比較複雜
改天我再另外整理

這篇文章的程式碼
為Eclipse Project，需要的library都放好在裡面了，測試請以Unit Test執行PersonDaoTest.java

Generic CRUD DAO

Generic CRUD DAO只需要

GenericDao interface
GenericDaoHibernateImpl class

GenericDao.java

package genericdao;

import java.io.Serializable;

public interface GenericDao<T, PK extends Serializable> {
   PK create(T newInstance);
   T read(PK id);
   void update(T transientObject);
   void delete(T persistentObject);
}

GenericDaoHibernateImpl.java

package genericdao.impl;

import genericdao.GenericDao;
import java.io.Serializable;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.springframework.orm.hibernate3.SessionFactoryUtils;

public class GenericDaoHibernateImpl<T, PK extends Serializable> implements GenericDao<T, PK> {
   private SessionFactory sessionFactory;

   private Class<T> type;

   public GenericDaoHibernateImpl(Class<T> type) {
      this.type = type;
   }

   public PK create(T o) {
      return (PK) getSession().save(o);
   }

   public T read(PK id) {
      return (T) getSession().get(type, id);
   }

   public void update(T o) {
      getSession().update(o);
   }

   public void delete(T o) {
      getSession().delete(o);
   }

   public Session getSession() {
      boolean allowCreate = true;
      return SessionFactoryUtils.getSession(sessionFactory, allowCreate);
   }

   public void setSessionFactory(SessionFactory sessionFactory) {
      this.sessionFactory = sessionFactory;
   }
}

Your DAO

使用Generic CRUD DAO來寫你自己的CRUD DAO你需要

Your Domain Object
Your Domain Object's Hibernate Mapping

Person.java (Your Domain Object)

package genericdaotest.domain;

import java.io.Serializable;

public class Person implements Serializable {
   private Long id;

   private String name;

   private Integer weight;

   public Person(String name, Integer weight) {
      this.name = name;
      this.weight = weight;
   }

   // Default constructor needed by Hibernate
   protected Person() {
   }

   public Long getId() {
      return id;
   }

   private void setId(Long id) {
      this.id = id;
   }

   public String getName() {
      return name;
   }

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

   public Integer getWeight() {
      return weight;
   }

   public void setWeight(Integer weight) {
      this.weight = weight;
   }
}

Person.hbm.xml (Your Domain Object's Hibernate Mapping)

<?xml version="1.0"?>
<!DOCTYPE hibernate-mapping PUBLIC
        "-//Hibernate/Hibernate Mapping DTD 3.0//EN"
        "http://hibernate.sourceforge.net/hibernate-mapping-3.0.dtd">

<hibernate-mapping package="genericdaotest.domain">
   <class name="Person">
      <id name="id">
         <generator class="native"></generator>
      </id>
      <property name="name" update="false" />
      <property name="weight" />
   </class>
</hibernate-mapping>

Use Your DAO

使用你的DAO需要

Spring Configuration File
Codes That Use Your DAO

my-test.xml (Spring Configration File)

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE beans PUBLIC "-//SPRING//DTD BEAN//EN" "http://www.springframework.org/dtd/spring-beans.dtd" >
<beans>
   <bean id="dataSource"
      class="org.springframework.jdbc.datasource.DriverManagerDataSource">
      <property name="driverClassName">
         <value>org.hsqldb.jdbcDriver</value>
      </property>
      <property name="url">
         <value>jdbc:hsqldb:file:db/data</value>
      </property>
      <property name="username">
         <value>sa</value>
      </property>
      <property name="password">
         <value></value>
      </property>
   </bean>

   <bean id="sessionFactory"
      class="org.springframework.orm.hibernate3.LocalSessionFactoryBean">
      
      <property name="mappingResources">
         <list>
            <value>genericdaotest/domain/Person.hbm.xml</value>
         </list>
      </property>
      <property name="hibernateProperties">
         <props>
            <prop key="hibernate.dialect">
               org.hibernate.dialect.HSQLDialect
            </prop>
            <prop key="hibernate.show_sql">true</prop>
            <prop key="hibernate.hbm2ddl.auto">create</prop>
         </props>
      </property>
      <property name="dataSource">
         <ref bean="dataSource" />
      </property>
   </bean>

   <bean id="personDao"
      class="genericdao.impl.GenericDaoHibernateImpl">
      <constructor-arg>
         <value>genericdaotest.domain.Person</value>
      </constructor-arg>
      <property name="sessionFactory">
         <ref bean="sessionFactory" />
      </property>
   </bean>
</beans>

PersonDaoTest.java (Codes That Use Your DAO)

package genericdaotest;

import genericdao.GenericDao;
import genericdaotest.domain.Person;
import junit.framework.TestCase;

import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
import org.springframework.orm.hibernate3.SessionFactoryUtils;
import org.springframework.orm.hibernate3.SessionHolder;
import org.springframework.transaction.support.TransactionSynchronizationManager;

public class PersonDaoTest extends TestCase {
   private ApplicationContext factory;

   public PersonDaoTest(String s) {
      super(s);
      factory = new ClassPathXmlApplicationContext("my-test.xml");
   }

   public void testCrud() throws Exception {
      // Create
      GenericDao personDao = (GenericDao) factory.getBean("personDao");
      Person createPerson = new Person("Mellqvist", 88);
      personDao.create(createPerson);
      assertNotNull(createPerson.getId());
      Long id = createPerson.getId();

      restartSession();

      // Read
      Person foundPerson = (Person) personDao.read(id);
      assertEquals(createPerson.getWeight(), foundPerson.getWeight());

      restartSession();

      // Update
      Integer updateWeight = 90;
      foundPerson.setWeight(updateWeight);
      personDao.update(foundPerson);
      Person updatedPerson = (Person) personDao.read(id);
      assertEquals(updateWeight, updatedPerson.getWeight());

      restartSession();

      // Delete
      personDao.delete(updatedPerson);
      restartSession();
      assertNull(personDao.read(id));
   }

   protected void setUp() throws Exception {
      openSession();
   }

   protected void tearDown() throws Exception {
      closeSession();
   }

   private void openSession() {
      SessionFactory sessionFactory = getSessionFactory();
      Session session = SessionFactoryUtils.getSession(sessionFactory, true);
      TransactionSynchronizationManager.bindResource(sessionFactory,
            new SessionHolder(session));
   }

   private void closeSession() {
      SessionFactory sessionFactory = getSessionFactory();
      SessionHolder sessionHolder = (SessionHolder) TransactionSynchronizationManager
            .unbindResource(sessionFactory);
      sessionHolder.getSession().flush();
      sessionHolder.getSession().close();
      SessionFactoryUtils.releaseSession(sessionHolder.getSession(),
            sessionFactory);
   }

   private void restartSession() {
      closeSession();
      openSession();
   }

   private SessionFactory getSessionFactory() {
      return (SessionFactory) factory.getBean("sessionFactory");
   }
}