EJB笔记

一、EJB基础

1.概念

Enterprice JavaBean是一个用于分布式业务应用的标准服务端组件模型。采用ejb架构的应用是可伸的、事务性、多用户安全的。一般部署在jboss服务器上。

2.ejb类型

会话bean（Session Bean）：

会话bean用于实现业务逻辑，它分为有状态bean和无状态bean。会话bean可以直接访问数据库，但更多时候，它是通过实体bean实现数据库访问。

实体bean（Entity Bean）：

实体bean主要作为普通java对象使用，负责跟数据库表进行对象与关系映射。

消息驱动bean（MessageDrive Bean）：

MDB是设计用来专门处理基于消息请求的组件。它能够收发异步JMS消息，并更够与其他JEB交互。它适用于当一个业务执行的时间很长，而执行的结果无需实时向用户反馈的场景。

二、代码实现

1.服务端

• 远程无状态会话bean接口

package com.ejbtest.service.bean;import java.util.List;import javax.ejb.Remote;import javax.ejb.Stateless;import javax.ejb.TransactionManagement;import javax.ejb.TransactionManagementType;import javax.persistence.EntityManager;import javax.persistence.EntityManagerFactory;import javax.persistence.Persistence;import javax.persistence.Query;import com.ejbtest.service.vo.CtocOrder;//mappedName 是bean映射名称，客户端调用@Stateless(mappedName = "ejbTest_jndi")@Remote({ IEjbService.class })@TransactionManagement(TransactionManagementType.BEAN)public class EjbServiceBean implements IEjbService{        //注解获得实体管理对象      @javax.persistence.PersistenceUnit()private EntityManagerFactory emf;public EntityManager getEntityManager() {return emf.createEntityManager();}       //指定数据配置单元获得实体管理对象     public EntityManager getEntityManager01() {       return Persistence.createEntityManagerFactory("ejbTest-ejbPU").createEntityManager();        }@Overridepublic CtocOrder getOrderInfo(String escOrderid) {System.out.println("escOrderid="+escOrderid);EntityManager em=getEntityManager();String sql="SELECT t FROM CtocOrder t  where escOrderid=:escOrderid ";Query query=em.createQuery(sql);query.setParameter("escOrderid", escOrderid);List<CtocOrder> list=query.getResultList();if(list!=null&&list.size()>0){return list.get(0);}return null;}}

• 实体bean
  

package com.ejbtest.service.vo;import javax.persistence.Column;import javax.persistence.Entity;import javax.persistence.Table; @Entity@Table(name = "CTOC_ORDER",schema = "POSTMALL_USER")public class CtocOrder implements java.io.Serializable {private static final long serialVersionUID = 8527656418454776528L;private String escOrderid;private String buyerName;  public CtocOrder() {}@Column(name = "ESC_ORDERID", length = 20)public String getEscOrderid() {return this.escOrderid;}public void setEscOrderid(String escOrderid) {this.escOrderid = escOrderid;}@Column(name = "BUYER_NAME", length = 128)public String getBuyerName() {return this.buyerName;}public void setBuyerName(String buyerName) {this.buyerName = buyerName;}}

• 数据源配置persistence.xml

<?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="ejbTest-ejbPU" transaction-type="RESOURCE_LOCAL">    <provider>org.hibernate.ejb.HibernatePersistence</provider>    <!-- jboss 数据源配置jndi-name -->    <non-jta-data-source>java:ejbTest_db</non-jta-data-source>    <!-- 数据库映射实体bean -->    <class>com.ejbtest.service.vo.CtocOrder</class>    <exclude-unlisted-classes>false</exclude-unlisted-classes>    <properties>      <property name="hibernate.show_sql" value="false" />      <property name="min-pool-size" value="5" />      <property name="max-pool-size" value="20" />      <property name="idle-timeout-minutes" value="5" />      <property name="hibernate.connection.autocommit" value="false" />      <property name="hibernate.connection.SetBigStringTryClob" value="true"/>      <property name="hibernate.dialect" value="org.hibernate.dialect.OracleDialect" />      <property name="hibernate.jdbc.batch_size" value="3"/>       <property name="hibernate.max_fetch_depth" value="5"/>    </properties>  </persistence-unit></persistence>

 注：persistence.xml位于src/META-INF下

• pom配置
  

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0                      http://maven.apache.org/xsd/maven-4.0.0.xsd">    <modelVersion>4.0.0</modelVersion>    <!-- The Basics -->    <groupId>com.ejbtest</groupId>    <artifactId>ejbTestServcie</artifactId>    <version>1.0</version>    <packaging>ejb</packaging>    <dependencies>       <dependency><groupId>javax.ejb</groupId><artifactId>ejb-api</artifactId><version>3.0</version></dependency><dependency><groupId>javax.persistence</groupId><artifactId>persistence-api</artifactId><version>1.0</version></dependency>             </dependencies>        <build>        <resources>            <resource>                <directory>src/main/resources</directory>                <includes>                    <include>**/*.*</include>                </includes>            </resource>        </resources>        <plugins>            <plugin>                <groupId>org.apache.maven.plugins</groupId>                <artifactId>maven-compiler-plugin</artifactId>                <version>3.1</version>                <configuration>                    <source>1.6</source>                    <target>1.6</target>                    <encoding>UTF-8</encoding>                    <debug>true</debug>                    <fork>true</fork>                </configuration>            </plugin>            <plugin>                <groupId>org.apache.maven.plugins</groupId>                <artifactId>maven-eclipse-plugin</artifactId>                <version>2.8</version>                <configuration>                    <wtpversion>2.0</wtpversion>                    <wtpContextName>/</wtpContextName>                </configuration>            </plugin>            <plugin>                <groupId>org.apache.maven.plugins</groupId>                <artifactId>maven-ejb-plugin</artifactId>                <configuration>                    <ejbVersion>3.0</ejbVersion>                    <generateClient>true</generateClient>                    <jarName>ejbtest-1.0</jarName>                </configuration>            </plugin>            <plugin>                <groupId>org.apache.maven.plugins</groupId>                <artifactId>maven-jar-plugin</artifactId>                <version>2.3</version>                <executions>                    <execution>                        <id>ejbtest-util</id>                        <phase>package</phase>                        <goals>                            <goal>jar</goal>                        </goals>                        <configuration>                            <classifier>util</classifier>                            <jarName>ejbtest-1.0</jarName>                        </configuration>                    </execution>                </executions>            </plugin>                   </plugins>    </build>    <distributionManagement>        <repository>            <id>tom-maven-repository</id>            <name>Tom Maven Repository</name>            <url>xxxx</url>        </repository>    </distributionManagement>    <repositories>        <repository>            <releases>                <enabled>true</enabled>                <updatePolicy>always</updatePolicy>                <checksumPolicy>fail</checksumPolicy>            </releases>            <id>internal</id>            <name>Tom Central Maven Repository</name>            <layout>default</layout>            <url>xxx</url>            <snapshots>                <updatePolicy>always</updatePolicy>                <checksumPolicy>warn</checksumPolicy>            </snapshots>        </repository>    </repositories></project>

2.客户端

package com.ejbtest.client;import java.util.Properties;import javax.naming.Context;import javax.naming.InitialContext;import javax.naming.NamingException;import com.ejbtest.service.bean.IEjbService;import com.ejbtest.service.vo.CtocOrder;public class Test {    public static void main(String[] args) throws NamingException {        Properties props = new Properties();        props.put("java.naming.factory.initial","org.jnp.interfaces.NamingContextFactory");        props.put("java.naming.provider.url", "127.0.0.1:1004");//ejb服务地址        props.put("java.naming.factory.url.pkgs", "org.jboss.naming");        Context ctx = new InitialContext(props);        IEjbService service = (IEjbService) ctx.lookup("ejbTest_jndi");//ejb bean接口名称        CtocOrder order=service.getOrderInfo("2017052400494689");        System.out.println(order.getEscOrderid()+">>>>"+order.getBuyerName());    }     }

注：客户端要引用jboss client jar