Spring Data JPA 基本篇 @ MISTECH 技術手抄本

本文的示例代碼基於 Hibernate EntityManager 開發，程式碼中使用到的都是 JPA 規範提供的Interface / Class，以便瞭解 JPA 基本的概念。整個系統架構如下

jpa-mis

Step 01 : create mysql table: person

CREATE TABLE `person` (
`id` int(10) unsigned NOT NULL AUTO_INCREMENT,
`firstName` varchar(45) NOT NULL,
`lastName` varchar(45) NOT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB AUTO_INCREMENT=3 DEFAULT CHARSET=utf8;

Step 02: 利用 Hibernate Tool 自動建立 Entity model :Person.java

package com.mis.demos.model;
// Generated Jan 20, 2016 10:35:00 AM by Hibernate Tools 4.3.1

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import static javax.persistence.GenerationType.IDENTITY;
import javax.persistence.Id;
import javax.persistence.Table;

/**
* Person generated by hbm2java
*/
@Entity
@Table(name = "person", catalog = "spring")
public class Person implements java.io.Serializable {

   private Integer id;
   private String firstName;
   private String lastName;

   public Person() {
   }

   public Person(String firstName, String lastName) {
       this.firstName = firstName;
       this.lastName = lastName;
   }

   @Id
   @GeneratedValue(strategy = IDENTITY)

   @Column(name = "id", unique = true, nullable = false)
   public Integer getId() {
       return this.id;
   }

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

   @Column(name = "firstName", nullable = false, length = 45)
   public String getFirstName() {
       return this.firstName;
   }

   public void setFirstName(String firstName) {
       this.firstName = firstName;
   }

   @Column(name = "lastName", nullable = false, length = 45)
   public String getLastName() {
       return this.lastName;
   }

   public void setLastName(String lastName) {
       this.lastName = lastName;
   }

}

Step 03: 直接用 Service 去存取 table ，不建立 DAO (Data Access Object)，正常來說，是應該要先建立 DAO 的，我有點偷懶...:

package com.mis.demos.services;

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

import com.mis.demos.model.Person;
/**
* 沒有透過 DAO 操作 CRUD
* @author polin.wei
*
*/
public class PersonPU {

   private EntityManager em;
   private EntityManagerFactory emf;


   public void clientSave(Person person){
       emf = Persistence.createEntityManagerFactory("mysqlLocalPU");
       em = emf.createEntityManager();
       if (person.getId()==null){
           // new
           em.getTransaction().begin();
           em.persist(person);
           em.getTransaction().commit();
       } else {
           // update
           em.getTransaction().begin();
           em.merge(person);
           em.getTransaction().commit();
       }
       em.close();
       emf.close();
   }
}

Step 04: 建立 src\main\resources\META-INF\persistence.xml

<?xml version="1.0" encoding="UTF-8"?>
<persistence xmlns="http://java.sun.com/xml/ns/persistence"
   version="2.0">
   <persistence-unit name="mysqlLocalPU"
       transaction-type="RESOURCE_LOCAL">
       <provider>org.hibernate.jpa.HibernatePersistenceProvider</provider>
       <properties>
           <property name="hibernate.connection.driver_class" value="org.gjt.mm.mysql.Driver" />
           <property name="hibernate.connection.url" value="jdbc:mysql://localhost:3306/spring" />
           <property name="hibernate.connection.username" value="root" />
           <property name="hibernate.connection.password" value="root" />
           <property name="hibernate.dialect" value="org.hibernate.dialect.MySQLInnoDBDialect" />
           <property name="hibernate.show_sql" value="true" />
           <property name="hibernate.format_sql" value="true" />
           <property name="hibernate.use_sql_comments" value="false" />
           <property name="hibernate.hbm2ddl.auto" value="update" />
       </properties>
   </persistence-unit>

</persistence>

Step 05: 測試

package com.mis.demos;

import javax.annotation.Resource;

import org.springframework.context.support.ClassPathXmlApplicationContext;

import com.mis.demos.dao.PersonDao;
import com.mis.demos.dao.PersonSpringDataDao;
import com.mis.demos.model.Person;
import com.mis.demos.services.PersonPU;
import com.mis.demos.services.PersonService;
import com.mis.demos.services.PersonSpringDataService;
import com.mis.demos.services.PersonSpringDataServiceImpl;
public class SimpleSpringJpaDemo {

   public static void main(String[] args) {

        doPersistenceSave();

   }

   public static void doPersistenceSave(){
       Person person = new Person();
       // 利用 ID 是否有給值來作 save & update 的判斷
       person.setId(2);
       person.setFirstName("polin-2-6");
       person.setLastName("wei-2-6");

       new PersonPU().clientSave(person);
   }

}

從 Spring + Hibernate 到 Spring Data JPA

http://cw1057.blogspot.tw/2013/12/more-in-spring-data-jpa-150-m1.html

https://struts.apache.org/docs/struts-2-spring-2-jpa-ajax.html#Struts2+Spring2+JPA+AJAX-Themavenway

https://www.ibm.com/developerworks/cn/opensource/os-cn-spring-jpa/

http://www.mastertheboss.com/jboss-frameworks/hibernate-jpa/jpa-configuration/how-to-use-multiple-database-in-persistencexml