EJB 3.0和Spring 2.5 ：在Spring中使用EJB 3.0

Meera Subbarao说道：EJB和Spring社区的开发者为什么总是贬低对方呢？我同时使用EJB和Spring，就像所有的开发者一样，我对于两者需要大量的XML设置非常头疼，但是从Java 5发布以来，XML配置已经用annotation来替代了。但是在使用了最新的Spring 2.5和EJB 3.0,我觉得它们是互相补充的关系，而非相互竞争关系。

许多开发者理解，Spring是由Spring Source创建的最常用的非标准框架，而EJB 3.0是一个由主要的JEE厂商创建的规格。我以前曾一起工作的同事更愿意使用标准规格，选择EJB 2.X现在迁移到EJB 3.0。也有开发者愿意使用Spring而拒绝EJB。但是没有任何东西阻止开发者同时使用Spring和EJB，对不对？在Spring的配置文件增加几行就能够在Spring中无缝使用EJB 3.0组件。

下面我将展示这个过程是多么简单，我们可以通过Spring的强大的依赖注入机制来注入Customer session bean。这个Customer session bean可以使用Entity Manager来进行创建/读写/删除操作。

1。创建一个简单的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.创建一个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.编译，打包，部署到一个应用服务器上。

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>

当你的应用部署以后，确认session bean JNDI名称，在 GlassFish 中，点击JNDI浏览工具按钮查看：



4: 测试无状态 Session beans.



5: 创建一个 Spring Bean.

创建一个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 进入我们的 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: 测试

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("[e-mail]");
        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));

    }
}

整个过程结束，使用Spring和EJB 3.0能够同时或者两者的好处。