Java Web 应用开发：J2EE 和 Tomcat

蔡 剑 , Ph.D.

本讲内容 EJB 层技术 (II)

Transaction and Security Resource Connection Deployment

Web Services

Review: J2EE Framework

(X)HTMLXML

Applet

ClientApplication

JAF

JMS

JDB

C

JTA

JND

I

JSTL

Servlets JSPs

Web Container

SessionBeans

EntityBeans

EJB Container

J2EEApplicationServer

RDMS

Mail Server

JavaApplication

CORBAServer

DirectoryService

Message Queue

JDBC

JavaMail

RMI

IIOP

JNDI

JMS

HTTP

MessageBeans

Application Client Container

JAXRPC

SAAJ

JAX

RJA

CC

Mgmt

JMX

JAF

JMS

JDB

C

JTA

JND

I

JAXRPC

SAAJ

JAX

RJA

CC

Mgmt

JMX

JAXRPC

SAAJ

JAX

RJM

S

Mgmt

JMX

Web Application Architecture: MVC Model

Model• Encapsulates application state

•Responds to state queries• Exposes application functionality

•Notifies views of changes

Model• Encapsulates application state

•Responds to state queries• Exposes application functionality

•Notifies views of changes

View• Renders the models

• Request updates from models• Sends user gestures to Controller

• Allows controller to select View

View• Renders the models

• Request updates from models• Sends user gestures to Controller

• Allows controller to select View

Controller• Define application behavior

• Maps user actions to model updates• Select view for response•One for each functionality

Controller• Define application behavior

• Maps user actions to model updates• Select view for response•One for each functionality

State Query State Change

ViewSelection

User gestures

Change Notice

Transaction Conceptbegin transaction

debit checking account

credit savings account

update history log

commit transaction

CMT Transaction Managementpublic void transferToSaving(double amount) throws InsufficientBalanceException { checkingBalance -= amount; savingBalance += amount; try { updateChecking(checkingBalance); if (checkingBalance < 0.00) { context.setRollbackOnly(); throw new InsufficientBalanceException(); } updateSaving(savingBalance); } catch (SQLException ex) { throw new EJBException ("Transaction failed due to SQLException: " + ex.getMessage()); }}

BMT Transaction Management : JDBC

public void ship (String productId, String orderId, int quantity) { try { con.setAutoCommit(false); updateOrderItem(productId, orderId); updateInventory(productId, quantity); con.commit(); } catch (Exception ex) { try { con.rollback(); throw new EJBException("Transaction failed: " + ex.getMessage()); } catch (SQLException sqx) { throw new EJBException("Rollback failed: " + sqx.getMessage()); } }}

BMT Transaction Management : JTA

public void withdrawCash(double amount) {UserTransaction ut = context.getUserTransaction();try { ut.begin(); updateChecking(amount); machineBalance -= amount; insertMachine(machineBalance); ut.commit(); } catch (Exception ex) { try { ut.rollback(); } catch (SystemException syex) { throw new EJBException ("Rollback failed: " + syex.getMessage()); } throw new EJBException ("Transaction failed: " + ex.getMessage());}

Transaction Allowance

Bean Type Container-Managed

Bean-Managed

JTA

JDBC

Entity Y N N

Session Y Y Y

Message-driven

Y Y Y

Updating Multiple Databases

Resource Connections

Resource Manager Type Connection Factory Type JNDI Subcontext

JDBC javax.sql.DataSource java:comp/env/jdbc

JMS

javax.jms.TopicConnectionFactory javax.jms.QueueConnectionFactory

java:comp/env/jms

JavaMail javax.mail.Session java:comp/env/mail

URL java.net.URL java:comp/env/url

Connector javax.resource.cci.ConnectionFactory java:comp/env/eis

JAXR Resource Adapter

javax.xml.registry.ConnectionFactory

java:comp/env/eis/JAXR

Database Connection

  private String dbName    = "java:comp/env/jdbc/SavingsAccountDB";

  InitialContext ic = new InitialContext();

  DataSource ds = (DataSource) ic.lookup(dbName);

  Connection con = ds.getConnection();

EJB Deployment: Security Declare

Programmatic Security in the EJB Tier

public String getUser() { return context.getCallerPrincipal().getName(); }

boolean result = context.isCallerInRole("Customer");

Propagating Security Identity

Web Deployment: Security Declare

Packaging Modules

EJB 模块，其包含 ejb 文件及相应类 Web 模块，其包含网络层的组件及资源 应用客户模块，其包含应用客户类 资 源 适 配 器 模 块 ， 其 包 含 java 连 接 器

(connector), 资源适配器，和帮助库函数及相关资源。

Deployment Configuration Files

EJB 部署描述文件 网络层部署描述文件 web.xml 应用客户部署描述文件 资源适配器部署描述文件

EJB Deployment: Packaging

EJB and Web Services

J2EE1.4 Web Services

.Net Web Services

Perl Web Services

EJB2.1 Container

StatelessSession Bean

SOAP

SOAP

SOAP

Web Services

Web Services Support Web services are Web-based enterprise applications

that use open, Extensible Markup Language (XML)-based standards and transport protocols to exchange data with calling clients.

The J2EE platform provides the XML APIs and tools you need to quickly design, develop, test, and deploy Web services and clients that fully interoperate with other Web services and clients running on Java-based or non-Java-based platforms.

It is easy to write Web services and clients with the J2EE XML APIs. No low-level programming is needed because the XML API implementations do the work of translating the application data to and from an XML-based data stream that is sent over the standardized XML-based transport protocols.

The translation of data to a standardized XML-based data stream is what makes Web services and clients written with the J2EE XML APIs fully interoperable.

Web Services Concept

Web Services

Web Services Standards

Three Players of WS

SOAP

UDDI

WSDL

J2EE Web Services