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前进：从EJB 2.1到EJB 3.0 |
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时间: 2006-06-22 来自：天极开发 |
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迁移EJB会话bean客户端
一个EJB 2.1会话bean的客户端通过使用JNDI名可取得一个会话bean对象，如下所示的客户端使用了BookCatalogLocalHome的JNDI名取得一个本地主对象，接着调用了create()方法，随后，客户端用getEdition(String)业务方法输出特定标题的版本值。
import javax.naming.InitialContext;
public class BookCatalogClient
{
public static void main(String[] argv)
{
try{
InitialContext ctx=new InitialContext();
Object objref=ctx.lookup("BookCatalogLocalHome");
BookCatalogLocalHome catalogLocalHome = (BookCatalogLocalHome)objref;
BookCatalogLocal catalogLocal = (BookCatalogLocal) catalogLocalHome.
create();
String title="Java and XML";
String edition = catalogLocal.getEdition(title);
System.out.println("标题的版本：" + title + " " + edition);
}
catch(Exception e){}
}
} |
在EJB 3.0中，可通过依赖性注入，来获取一个对会话bean对象的引用，这通常由@Inject、@Resource、@EJB注释来实现。如下所示的EJB 3.0会话bean客户端使用了@Inject注释注入到BookCatalogBean类中，仍可由getEdition(String)业务方法来获取标题的版本值。
public class BookCatalogClient
{
@Inject BookCatalogBean;
BookCatalogBean catalogBean;
String title="Java and XML";
String edition=catalogBean.getEdition(edition);
System.out.println("标题版本：" + title + " " + edition);
} |
迁移实体bean
本节讲述如何迁移EJB 2.1的实体bean到EJB 3.0。一个EJB 2.1实体bean实现了EntityBean接口，其由getter和setter CMP字段方法、getter和setter CMR字段方法、回调方法及ejbCreate/ejbPostCreate方法组成。示例实体bean（见例1）--BookCatalogBean.java，由CMP字段标题、作者、发行者和CMR字段版本组成。
例1：BookCatalogBean.java
import javax.ejb.EntityBean;
import javax.ejb.EntityContext;
public class BookCatalogBean implements EntityBean
{
private EntityContext ctx;
public abstract void setTitle();
public abstract String getTitle();
public abstract void setAuthor();
public abstract String getAuthor();
public abstract void setPublisher();
public abstract String getPublisher();
public abstract void setEditions(java.util.Collection editions);
public abstract java.util.Collection getEditions();
public String ejbCreate(String title)
{
setTitle(title);
return null;
}
public void ejbRemove() {}
public void ejbActivate() {}
public void ejbPassivate() {}
public void ejbLoad() {}
public void ejbStore() {}
public void setEntityContext(EntityContext ctx)
{
this.ctx=ctx;
}
public void unsetEntityContext()
{
ctx = null;
}
} |
而这个EJB 2.1实体bean的ejb-jar.xml部署描述符（见例2）文件，指定了EJB类、接口、CMP字段、EJB QL查询和CMR关系。BookCatalogBean实体Bean定义了一个查找方法findByTitle()、一个CMR字段及版本。
例2：ejb-jar.xml部署描述符
＜?xml version="1.0"?＞
＜!DOCTYPE ejb-jar PUBLIC
"-//Sun Microsystems, Inc.//DTD Enterprise JavaBeans 2.0//EN"
"http://java.sun.com/dtd/ejb-jar_2_0.dtd"＞
＜ejb-jar＞
＜enterprise-beans＞
＜entity＞
＜ejb-name＞BookCatalog＜/ejb-name＞
＜local-home＞BookCatalogLocalHome＜/local-home＞
＜local＞BookCatalogLocal＜/local＞
＜ejb-class＞BookCatalogBean＜/ejb-class＞
＜persistence-type＞Container＜/persistence-type＞
＜prim-key-class＞String＜/prim-key-class＞
＜reentrant＞False＜/reentrant＞
＜cmp-version＞2.x＜/cmp-version＞
＜abstract-schema-name＞BookCatalog＜/abstract-schema-name＞
＜cmp-field＞
＜field-name＞title＜/field-name＞
＜/cmp-field＞
＜cmp-field＞
＜field-name＞author＜/field-name＞
＜/cmp-field＞
＜cmp-field＞
＜field-name＞publisher＜/field-name＞
＜/cmp-field＞
＜query＞
＜query-method＞
＜method-name＞findByTitle＜/method-name＞
＜method-params＞
＜method-param＞java.lang.String＜/method-param＞
＜/method-params＞
＜/query-method＞
＜ejb-ql＞
＜![CDATA[SELECT DISTINCT OBJECT(obj) FROM BookCatalog obj WHERE obj.title = ?1 ]]＞
＜/ejb-ql＞
＜/query＞
＜/entity＞
＜/enterprise-beans＞
＜relationships＞
＜ejb-relation＞
＜ejb-relation-name＞BookCatalog-Editions＜/ejb-relation-name＞
＜ejb-relationship-role＞
＜ejb-relationship-role-name＞
BookCatalog-Has-Editions
＜/ejb-relationship-role-name＞
＜multiplicity＞One＜/multiplicity＞
＜relationship-role-source＞
＜ejb-name＞BookCatalog＜/ejb-name＞
＜/relationship-role-source＞
＜cmr-field＞
＜cmr-field-name＞editions＜/cmr-field-name＞
＜cmr-field-type＞java.util.Collection＜/cmr-field-type＞
＜/cmr-field＞
＜/ejb-relationship-role＞
＜ejb-relationship-role＞
＜ejb-relationship-role-name＞
Editions-Belong-To-BookCatalog
＜/ejb-relationship-role-name＞
＜multiplicity＞One＜/multiplicity＞
＜cascade-delete /＞
＜relationship-role-source＞
＜ejb-name＞Edition＜/ejb-name＞
＜/relationship-role-source＞
＜/ejb-relationship-role＞
＜/ejb-relation＞
＜/relationships＞
＜/ejb-jar＞ |
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