EJB 3.0使用@Lob批注提供对Blob和Clob类型的支持.可以使用@Lob注释映射以下java类型.
java.sql.Blob
java.sql.Clob
byte []
字符串
可序列化对象
@Entity
@Table(name="books")
@EntityListeners(BookCallbackListener.class)
public class Book implements Serializable{
...
private byte[] image;
@Lob @Basic(fetch= FetchType.EAGER)
public byte[] getImage() {
return image;
}
...
}让我们创建一个测试EJB应用程序来测试EJB 3.0中的blob/clob支持.
| Step | 描述 |
|---|---|
| 1 | 在包 com.it1352.entity 下创建一个名为 EjbComponent 的项目，如下所述 EJB - 创建应用程序章节.请使用本章中 EJB - Persistence 章节中创建的项目来理解ejb概念中的clob/blob对象. |
| 2 | 在包 com下创建 Book.java . it1352.entity 的.使用 EJB - Persistence 章节作为参考.保持其余文件不变. |
| 3 | 清理并构建应用程序以确保业务逻辑按照要求运行. |
| 4 | 最后，在JBoss Application Server上以jar文件的形式部署应用程序.如果JBoss应用服务器尚未启动，它将自动启动. |
| 5 | 现在创建EJB客户端，一个基于控制台的应用程序，其方式与主题创建 EJB - 创建应用程序章节中所述的相同客户端访问EJB . |
CREATE TABLE book ( id integer PRIMARY KEY, name varchar(50) ); Alter table book add image bytea; Alter table book add xml text;
package com.it1352.entity;
import com.it1352.callback.BookCallbackListener;
import java.io.Serializable;
import javax.persistence.Basic;
import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.EntityListeners;
import javax.persistence.FetchType;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.Lob;
import javax.persistence.Table;
@Entity
@Table(name="book")
public class Book implements Serializable{
private int id;
private String name;
private byte[] image;
private String xml;
public Book() {
}
@Id
@GeneratedValue(strategy= GenerationType.IDENTITY)
@Column(name="id")
public int getId() {
return id;
}
public void setId(int id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
@Lob @Basic(fetch= FetchType.EAGER)
public byte[] getImage() {
return image;
}
public void setImage(byte[] image) {
this.image = image;
}
@Lob @Basic(fetch= FetchType.EAGER)
public String getXml() {
return xml;
}
public void setXml(String xml) {
this.xml = xml;
}
}
package com.it1352.stateless;
import com.it1352.entity.Book;
import java.util.List;
import javax.ejb.Remote;
@Remote
public interface LibraryPersistentBeanRemote {
void addBook(Book bookName);
List<Book> getBooks();
}
package com.it1352.stateless;
import com.it1352.entity.Book;
import java.util.List;
import javax.ejb.Stateless;
import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;
@Stateless
public class LibraryPersistentBean implements LibraryPersistentBeanRemote {
public LibraryPersistentBean() {
}
@PersistenceContext(unitName="EjbComponentPU")
private EntityManager entityManager;
public void addBook(Book book) {
entityManager.persist(book);
}
public List<Book> getBooks() {
return entityManager.createQuery("From Book").getResultList();
}
}一旦部署EjbComponent关于JBOSS的项目，请注意jboss日志.
JBoss已自动为会话bean创建了一个JNDI条目 - LibraryPersistentBean/remote .
我们将使用此查找字符串来获取类型的远程业务对象 - com.it1352.interceptor.LibraryPersistentBeanRemote
... 16:30:01,401 INFO [JndiSessionRegistrarBase] Binding the following Entries in Global JNDI: LibraryPersistentBean/remote - EJB3.x Default Remote Business Interface LibraryPersistentBean/remote-com.IT屋.interceptor.LibraryPersistentBeanRemote - EJB3.x Remote Business Interface 16:30:02,723 INFO [SessionSpecContainer] Starting jboss.j2ee:jar=EjbComponent.jar,name=LibraryPersistentBean,service=EJB3 16:30:02,723 INFO [EJBContainer] STARTED EJB: com.IT屋.interceptor.LibraryPersistentBeanRemote ejbName: LibraryPersistentBean 16:30:02,731 INFO [JndiSessionRegistrarBase] Binding the following Entries in Global JNDI: LibraryPersistentBean/remote - EJB3.x Default Remote Business Interface LibraryPersistentBean/remote-com.IT屋.interceptor.LibraryPersistentBeanRemote - EJB3.x Remote Business Interface ...
java.naming.factory.initial=org.jnp.interfaces.NamingContextFactory java.naming.factory.url.pkgs=org.jboss.naming:org.jnp.interfaces java.naming.provider.url=localhost
这些属性用于初始化java命名服务的InitialContext对象.
InitialContext对象将用于查找无状态会话bean.
package com.it1352.test;
import com.it1352.stateful.LibraryBeanRemote;
import java.io.BufferedReader;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.List;
import java.util.Properties;
import javax.naming.InitialContext;
import javax.naming.NamingException;
public class EJBTester {
BufferedReader brConsoleReader = null;
Properties props;
InitialContext ctx;
{
props = new Properties();
try {
props.load(new FileInputStream("jndi.properties"));
} catch (IOException ex) {
ex.printStackTrace();
}
try {
ctx = new InitialContext(props);
} catch (NamingException ex) {
ex.printStackTrace();
}
brConsoleReader =
new BufferedReader(new InputStreamReader(System.in));
}
public static void main(String[] args) {
EJBTester ejbTester = new EJBTester();
ejbTester.testBlobClob();
}
private void showGUI() {
System.out.println("**********************");
System.out.println("Welcome to Book Store");
System.out.println("**********************");
System.out.print("Options \n1. Add Book\n2. Exit \nEnter Choice: ");
}
private void testBlobClob() {
try {
int choice = 1;
LibraryPersistentBeanRemote libraryBean =
(LibraryPersistentBeanRemote)
ctx.lookup("LibraryPersistentBean/remote");
while (choice != 2) {
String bookName;
String publisherName;
String publisherAddress;
showGUI();
String strChoice = brConsoleReader.readLine();
choice = Integer.parseInt(strChoice);
if (choice == 1) {
System.out.print("Enter book name: ");
bookName = brConsoleReader.readLine();
String xml = "<book><name>"+bookName+"</name></book>";
Book book = new Book();
book.setName(bookName);
byte[] imageBytes = {0x32, 0x32,0x32, 0x32,0x32,
0x32,0x32, 0x32,
0x32, 0x32,0x32, 0x32,0x32, 0x32,0x32, 0x32,
0x32, 0x32,0x32, 0x32,0x32, 0x32,0x32, 0x32
};
book.setImage(imageBytes);
book.setXml(xml);
libraryBean.addBook(book);
} else if (choice == 2) {
break;
}
}
List<Book> booksList = libraryBean.getBooks();
System.out.println("Book(s) entered so far: " + booksList.size());
int i = 0;
for (Book book:booksList) {
System.out.println((i+1)+". " + book.getName());
byte[] imageByts = book.getImage();
if(imageByts != null) {
System.out.print("image bytes: [");
for(int j = 0; j < imageByts.length ; j++) {
System.out.print("0x"
+ String.format("%x", imageByts[j]) +" ");
}
System.out.println("]");
}
System.out.println(book.getXml());
i++;
}
} catch (Exception e) {
System.out.println(e.getMessage());
e.printStackTrace();
}finally {
try {
if(brConsoleReader !=null) {
brConsoleReader.close();
}
} catch (IOException ex) {
System.out.println(ex.getMessage());
}
}
}
}EJBTester执行以下任务.
从jndi.properties加载属性并初始化InitialContext对象.
在testInterceptedEjb()方法中，使用name - "LibraryPersistenceBean/remote"完成jndi查找以获取远程业务对象(无状态EJB).
然后用户显示库存储用户界面，并要求他/她输入选项.
如果用户输入1，系统将要求输入书名并保存本书使用无状态会话bean addBook()方法.会话Bean将书籍存储在数据库中.
如果用户输入2，系统将使用无状态会话bean getBooks()方法检索书籍并退出.
在项目资源管理器中找到EJBTester.java.右键单击EJBTester类并选择运行文件.
在Netbeans控制台中验证以下输出.
run: ********************** Welcome to Book Store ********************** Options 1. Add Book 2. Exit Enter Choice: 1 Enter book name: learn testing ********************** Welcome to Book Store ********************** Options 1. Add Book 2. Exit Enter Choice: 2 Book(s) entered so far: 1 1. learn testing image bytes: [ 0x32 0x32 0x32 0x32 0x32 0x32 0x32 0x32 0x32 0x32 0x32 0x32 0x32 0x32 0x32 0x32 0x32 0x32 0x32 0x32 0x32 0x32 0x32 0x32 ] <book><name>learn testing</name></book> BUILD SUCCESSFUL (total time: 20 seconds)
