Terry.Li-彬

來自：http://www.javaeye.com/news/3370-ejb-3-0-and-spring-2-5-the-use-of-spring-in-ejb-3-0
Meera Subbarao說道：EJB和Spring社區的開發者為什么總是貶低對方呢？我同時使用EJB和Spring，就像所有的開發者一樣，我對于兩者需要大量的XML設置非常頭疼，但是從Java 5發布以來，XML配置已經用annotation來替代了。但是在使用了最新的Spring 2.5和EJB 3.0,我覺得它們是互相補充的關系，而非相互競爭關系。

許多開發者理解，Spring是由Spring Source創建的最常用的非標準框架，而EJB 3.0是一個由主要的JEE廠商創建的規格。我以前曾一起工作的同事更愿意使用標準規格，選擇EJB 2.X現在遷移到EJB 3.0。也有開發者愿意使用Spring而拒絕EJB。但是沒有任何東西阻止開發者同時使用Spring和EJB，對不對？在Spring的配置文件增加幾行就能夠在Spring中無縫使用EJB 3.0組件。

下面我將展示這個過程是多么簡單，我們可以通過Spring的強大的依賴注入機制來注入Customer session bean。這個Customer session bean可以使用Entity Manager來進行創建/讀寫/刪除操作。

1。創建一個簡單的JPA Entity：

package com.ejb.domain;
import java.io.Serializable;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.Table;
/**
*
* @author meerasubbarao
*/
@Entity
@Table(name = "CUSTOMER", catalog = "", schema = "ADMIN")
public class Customer implements Serializable {
private static final long serialVersionUID = 1L;
@Id
@Column(name = "CUSTOMER_ID")
private Long customerId;
@Column(name = "FIRST_NAME")
private String firstName;
@Column(name = "LAST_NAME")
private String lastName;
@Column(name = "MIDDLE_NAME")
private String middleName;
@Column(name = "EMAIL_ID")
private String emailId;
public Customer() {
}
public Customer(Long customerId) {
this.customerId = customerId;
}
public Long getCustomerId() {
return customerId;
}
public void setCustomerId(Long customerId) {
this.customerId = customerId;
}
public String getFirstName() {
return firstName;
}
public void setFirstName(String firstName) {
this.firstName = firstName;
}
public String getLastName() {
return lastName;
}
public void setLastName(String lastName) {
this.lastName = lastName;
}
public String getMiddleName() {
return middleName;
}
public void setMiddleName(String middleName) {
this.middleName = middleName;
}
public String getEmailId() {
return emailId;
}
public void setEmailId(String emailId) {
this.emailId = emailId;
}
}

2.創建一個EJB 3.0 Session bean.

The Interface:

package com.ejb.service;
import com.ejb.domain.Customer;
import java.util.Collection;
import javax.ejb.Remote;
/**
*
* @author meerasubbarao
*/
@Remote
public interface CustomerService {
Customer create(Customer info);
Customer update(Customer info);
void remove(Long customerId);
Collection<Customer> findAll();
Customer[] findAllAsArray();
Customer findByPrimaryKey(Long customerId);
}

The Implementation Class:

package com.ejb.service;
import com.ejb.domain.Customer;
import java.util.Collection;
import javax.ejb.Stateless;
import javax.jws.WebService;
import javax.jws.soap.SOAPBinding;
import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;
import javax.persistence.Query;
import javax.jws.WebMethod;
/**
*
* @author meerasubbarao
*/
@WebService(name = "CustomerService", serviceName = "CustomerService", targetNamespace = "urn:CustomerService")
@SOAPBinding(style = SOAPBinding.Style.RPC)
@Stateless(name = "CustomerService")
public class CustomerServiceImpl implements CustomerService {
@PersistenceContext
private EntityManager manager;
@WebMethod
public Customer create(Customer info) {
this.manager.persist(info);
return info;
}
@WebMethod
public Customer update(Customer info) {
return this.manager.merge(info);
}
@WebMethod
public void remove(Long customerId) {
this.manager.remove(this.manager.getReference(Customer.class, customerId));
}
public Collection<Customer> findAll() {
Query query = this.manager.createQuery("SELECT c FROM Customer c");
return query.getResultList();
}
@WebMethod
public Customer[] findAllAsArray() {
Collection<Customer> collection = findAll();
return (Customer[]) collection.toArray(new Customer[collection.size()]);
}
@WebMethod
public Customer findByPrimaryKey(Long customerId) {
return (Customer) this.manager.find(Customer.class, customerId);
}
}

3.編譯，打包，部署到一個應用服務器上。

我使用GlassFish，用缺省的持久化提供工具TopLink，persistence.xml文件配置如下：

<?xml version="1.0" encoding="UTF-8"?>
<persistence version="1.0" xmlns="http://java.sun.com/xml/ns/persistence" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/persistence http://java.sun.com/xml/ns/persistence/persistence_1_0.xsd">
<persistence-unit name="SpringAndEJBPU" transaction-type="JTA">
<provider>oracle.toplink.essentials.PersistenceProvider</provider>
<jta-data-source>spring-ejb</jta-data-source>
<properties>
<property name="toplink.ddl-generation" value="drop-and-create-tables"/>
</properties>
</persistence-unit>
</persistence>

當你的應用部署以后，確認session bean JNDI名稱，在 GlassFish 中，點擊JNDI瀏覽工具按鈕查看：



4: 測試無狀態 Session beans.



5: 創建一個 Spring Bean.

創建一個CustomerManager 接口：

package com.spring.service;
import com.ejb.domain.Customer;
/**
*
* @author meerasubbarao
*/
public interface CustomerManager {
public void addCustomer(Customer customer);
public void removeCustomer(Long customerId);
public Customer[] listCustomers();
}

package com.spring.service;
import com.ejb.domain.Customer;
import com.ejb.service.CustomerService;
/**
*
* @author meerasubbarao
*/
public class CustomerManagerImpl implements CustomerManager {
CustomerService customerService;
public void setCustomerService(CustomerService customerService) {
this.customerService = customerService;
}
public void removeCustomer(Long customerId) {
customerService.remove(customerId);
}
public Customer[] listCustomers() {
return customerService.findAllAsArray();
}
public void addCustomer(Customer customer) {
customerService.create(customer);
}
}

6: 注入 EJB 3.0 Session bean 進入我們的 Spring Beans.

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xmlns:context="http://www.springframework.org/schema/context"
xmlns:jee="http://www.springframework.org/schema/jee"
xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-2.5.xsd
http://www.springframework.org/schema/context http://www.springframework.org/schema/context/spring-context-2.5.xsd
http://www.springframework.org/schema/jee http://www.springframework.org/schema/jee/spring-jee-2.5.xsd">
<jee:jndi-lookup id="customerService" <b>jndi-name="com.ejb.service.CustomerService"</b>>
</jee:jndi-lookup>
<bean id="manageCustomer"
class="com.spring.service.CustomerManagerImpl">
<property name="customerService" ref="customerService" />
</bean>
</beans>

<jee:jndi-lookup id="customerService" jndi-name="com.ejb.service.CustomerService">
</jee:jndi-lookup>

    <bean id="manageCustomer"
class="com.spring.service.CustomerManagerImpl">
<property name="customerService" ref="customerService" />
</bean>

7: 測試

package com.spring.client;
import com.ejb.domain.Customer;
import com.spring.service.CustomerManager;
import org.springframework.context.ApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;
public class SpringAndEJBMain {
public static void main(String[] args) {
ApplicationContext context =
new ClassPathXmlApplicationContext("SpringXMLConfig.xml");
CustomerManager service = (CustomerManager) context.getBean("manageCustomer");
Customer customer = new Customer();
customer.setFirstName("Meera");
customer.setLastName("Subbarao");
customer.setMiddleName("B");
customer.setEmailId("meera@springandejb.com");
customer.setCustomerId(new Long(1));
service.addCustomer(customer);
for (Customer cust : service.listCustomers()) {
System.out.println(cust.getFirstName());
System.out.println(cust.getLastName());
System.out.println(cust.getMiddleName());
System.out.println(cust.getEmailId());
}
service.removeCustomer(new Long(1));
}
}

整個過程結束，使用Spring和EJB 3.0能夠同時或者兩者的好處。