ICCT Wiki

User Tools

Site Tools

Trace: • lecture15 • lecture12
at-m42:lecture15

Differences

This shows you the differences between two versions of the page.

Link to this comparison view

Both sides previous revisionPrevious revision
Next revision		Previous revision
at-m42:lecture15 [2009/04/25 10:09] – eechrisat-m42:lecture15 [2011/01/14 12:45] (current) – external edit 127.0.0.1
Line 1: Line 1:
 ~~SLIDESHOW~~ ~~SLIDESHOW~~
-====== Business-tier Services ======+====== Enterprise Integration Tier Services ======
    
 In principle, the business logic of an enterprise application could be performed by //domain objects// which implement a model of the business concept as Plain-Old Java Objects (POJOs). In principle, the business logic of an enterprise application could be performed by //domain objects// which implement a model of the business concept as Plain-Old Java Objects (POJOs).
Line 15: Line 15:
   * [[#The key business tier services]]   * [[#The key business tier services]]
   * [[#The Java solution: Enterprise Java Beans]]   * [[#The Java solution: Enterprise Java Beans]]
-  * [[#Reimplementing PerfectTime as a session bean]]+  * [[#Reimplementing TimeHere as a session bean]]
   * [[#Is the Java solution a good solution?]]   * [[#Is the Java solution a good solution?]]
  
Line 107: Line 107:
   * **[[#The key business tier services]]**   * **[[#The key business tier services]]**
   * [[#The Java solution: Enterprise Java Beans]]   * [[#The Java solution: Enterprise Java Beans]]
-  * [[#Reimplementing PerfectTime as a session bean]]+  * [[#Reimplementing TimeHere as a session bean]]
   * [[#Is the Java solution a good solution?]]   * [[#Is the Java solution a good solution?]]
  
Line 136: Line 136:
     * Or simply to be stored in non-volatile memory.     * Or simply to be stored in non-volatile memory.
   * Your business objects want this to //just happen//!   * Your business objects want this to //just happen//!
-    * **Transparent persistence**, as discussed in the [[lecture14|last lecture]], is obviously important,+    * **Transparent persistence**, as discussed in the [[lecture15|last lecture]], is obviously important,
     * but persistence should also be a key part of transaction management and is a cornerstone of data integrity.     * but persistence should also be a key part of transaction management and is a cornerstone of data integrity.
  
Line 172: Line 172:
   * [[#The key business tier services]]   * [[#The key business tier services]]
   * **[[#The Java solution: Enterprise Java Beans]]**   * **[[#The Java solution: Enterprise Java Beans]]**
-  * [[#Reimplementing PerfectTime as a session bean]]+  * [[#Reimplementing TimeHere as a session bean]]
   * [[#Is the Java solution a good solution?]]   * [[#Is the Java solution a good solution?]]
  
Line 273: Line 273:
   * [[#The key business tier services]]   * [[#The key business tier services]]
   * [[#The Java solution: Enterprise Java Beans]]   * [[#The Java solution: Enterprise Java Beans]]
-  * **[[#Reimplementing PerfectTime as a session bean]]**+  * **[[#Reimplementing TimeHere as a session bean]]**
   * [[#Is the Java solution a good solution?]]   * [[#Is the Java solution a good solution?]]
  
Line 289: Line 289:
 import javax.ejb.*; import javax.ejb.*;
  
-public interface PerfectTime extends EJBObject { +package uk.ac.swan.atm42.ejb; 
-  public String getPerfectTime() throws RemoteException;+ 
 +public interface TimeHere extends EJBObject { 
 +  public String getTimeHere() throws RemoteException;
 } }
 </code> </code>
Line 298: Line 300:
 In EJB 3, the details can be left to the container: interface is a plain-old-Java interface //annotated//  with ''javax.ejb.Remote''. In EJB 3, the details can be left to the container: interface is a plain-old-Java interface //annotated//  with ''javax.ejb.Remote''.
      
-<code java 1|Example 2: Remote interface for the DateHereBean (at-m42/Examples/lecture14/TimeHere.java)> +<code java 1|Example 2: Remote interface for the DateHereBean (at-m42/Examples/lecture15/TimeHere.java)> 
-extern> http://cpjobling.org.uk/~eechris/at-m42/Examples/lecture14/TimeHere.java+extern> http://cpjobling.org.uk/~eechris/at-m42/Examples/lecture15/TimeHere.java
 </code> </code>
  
Line 320: Line 322:
  
 ===== Home interface for the TimeHere (EJB 2) ===== ===== Home interface for the TimeHere (EJB 2) =====
-<code java 1|Example 3: Remote interface for the DateHereBean (at-m42/Examples/lecture14/TimeHereHome.java)> +<code java 1|Example 3: Remote interface for the DateHereBean (at-m42/Examples/lecture15/TimeHereHome.java)> 
-extern> http://cpjobling.org.uk/~eechris/at-m42/Examples/lecture14/TimeHereHome.java+extern> http://cpjobling.org.uk/~eechris/at-m42/Examples/lecture15/TimeHereHome.java
 </code> </code>
  
Line 332: Line 334:
   - The return value and arguments of all methods must be valid RMI-IIOP data types.   - The return value and arguments of all methods must be valid RMI-IIOP data types.
  
-===== PerfectTimeBean (Session Bean) EJB 2 Version =====+===== TimeHereBean (Session Bean) EJB 2 Version =====
  
 <code java 1| Example 4: SessionBean implemented using EJB 2 conventions> <code java 1| Example 4: SessionBean implemented using EJB 2 conventions>
 // Simple Stateless Session Bean // Simple Stateless Session Bean
 // that returns current system time. // that returns current system time.
 +
 +package uk.ac.swan.atm42.ejb;
  
 import java.rmi.*; import java.rmi.*;
Line 364: Line 368:
   * EJB is now a "Plain Old Java Object" (POJO)) annotated with ''javax.ejb.Stateless''   * EJB is now a "Plain Old Java Object" (POJO)) annotated with ''javax.ejb.Stateless''
  
-===== PerfectTimeBean (Session Bean) EJB 2 Version ===== +===== TimeHereBean (Session Bean) EJB 3 Version ===== 
-<code java 1: Example 5: SessionBean implemented using EJB 3 conventions (at-m42/Examples/lecture14/TimeHereBean.java)> +<code java 1| Example 5: SessionBean implemented using EJB 3 conventions (at-m42/Examples/lecture15/TimeHereBean.java)> 
-extern> http://www.cpjobling.org.uk/~eechris/at-m42/Examples/lecture14/TimeHereBean.java+extern> http://www.cpjobling.org.uk/~eechris/at-m42/Examples/lecture15/TimeHereBean.java
 </code> </code>
  
-===== Deployment Descriptor ===== +===== Deployment Descriptor (EJB 2) =====
-An XML file that describes the EJB component. Should be stored in a file called ejb-jar.xml. <?xml version="1.0" encoding="Cp1252"?> <!DOCTYPE ejb-jar PUBLIC '-//Sun Microsystems, Inc.//DTD Enterprise JavaBeans 1.1//EN' 'http://java.sun.com/j2ee/dtds/ejb-jar_1_1.dtd'> <ejb-jar>   <description>Example for Chapter 15</description>   <display-name></display-name>   <small-icon></small-icon>   <large-icon></large-icon>   <enterprise-beans>     <session>       <ejb-name>PerfectTime</ejb-name>       <home>PerfectTimeHome</home>       <remote>PerfectTime</remote>       <ejb-class>PerfectTimeBean</ejb-class>       <session-type>Stateless</session-type>       <transaction-type>Container</transaction-type>     </session>   </enterprise-beans>   <ejb-client-jar></ejb-client-jar> </ejb-jar> +
-Deploying the EJB +
-The files must be archived inside a standard Java Archive (JAR) file. The deployment descriptors should be placed inside the /META-INF sub-directory of the Jar file. +
-Once the EJB component is defined in the deployment descriptor, the deployer should then deploy the EJB component into the EJB Container. +
-The deployment process is quite “GUI intensive” and specific to the individual EJB Container. +
-The deployment process creates some client stubs for calling the EJB component. These classes should be placed on the classpath of the client application. +
-When a client program wishes to invoke an EJB, it must look up the EJB component inside JNDI and obtain a reference to the home interface of the EJB component. The Home interface is used to create an instance of the EJB.  +
-The Client +
-Here a simple Java program but could just as easily be a servlet, a JSP or even a CORBA or RMI distributed object. // Client program for PerfectTimeBean public class PerfectTimeClient {   public static void main(String[] args) throws Exception {     // Get a JNDI context using     // the JNDI Naming service:     javax.naming.Context context = new       javax.naming.InitialContext();     // Look up the home interface in the     // JNDI Naming service:     Object ref = context.lookup("perfectTime");     // Cast the remote object to the home interface:     PerfectTimeHome home = (PerfectTimeHome)       javax.rmi.PortableRemoteObject.narrow(         ref, PerfectTimeHome.class); +
-The Client … cont +
-    // Create a remote object from the home interface:     PerfectTime pt = home.create();     // Invoke getPerfectTime()     System.out.println(       "Perfect Time EJB invoked, time is: " +         pt.getPerfectTime());   } } +
  
-=====  Lecture Content =====+An XML file that describes the EJB component. Should be stored in a file called ''ejb-jar.xml''. 
 +<code xml 1|Example 6: Deployment Descriptor for the TimeHereBean (not required in EJB 3 containers) (at-m42/Examples/lecture15/ejb-jar.xml)> 
 +extern> http://www.cpjobling.org.uk/~eechris/at-m42/Examples/lecture15/ejb-jar.xml 
 +</code> 
 +===== Deploying the EJB =====
  
-  * [[#An example]] +  * The files must be archived inside a standard Java Archive (JAR) file. The deployment descriptors (if used) should be placed inside the ''/META-INF'' sub-directory of the Jar file. 
-  * [[#The key business tier services]] +  * Once the EJB component is defined in the deployment descriptor, the deployer should then deploy the EJB component into the EJB Container. 
-  * [[#The Java solution: Enterprise Java Beans]] +  * The deployment process is quite "GUI intensive2 and specific to the individual EJB Container. 
-  * [[#Reimplementing PerfectTime as a session bean]] +  * The deployment process creates some client stubs for calling the EJB component. These classes should be placed on the CLASSPATH of the client application. 
-  * **[[#Is the Java solution a good solution?]]**+  * When a client program wishes to invoke an EJB it must look up the EJB component inside JNDI and obtain a reference to the home interface of the EJB component. The Home interface is used to create an instance of the EJB. 
  
 +===== The Client =====
  
 +  * Here a simple Java program but could just as easily be a servlet, a JSP or even a CORBA or RMI distributed object.
  
-===== Is the Java Solution a Good Solution? ===== +<code java 1|Example 7: Client program for TimeHereBean (at-m42/Examples/lecture15/TimeHereClient.java)> 
-During 2004, the developer community decided that the answer is probably no. +extern> http://www.cpjobling.org.uk/~eechris/at-m42/Examples/lecture15/TimeHereClient.java 
-We will discuss this issue, and some of the alternatives in the final lecture. +</code> 
-Eckel’s PerfectTime session EJB example gives a flavour of the complexity! To run the example, you’ll need an implementation of a J2EE container to which you can deploy the bean. +<code java 1| Example 7: Client program for TimeHereBean (at-m42/Examples/lecture15/TimeHereClient.java)>  
-It’s a good example of a bad design if nothing else!+extern> http://www.cpjobling.org.uk/~eechris/at-m42/Examples/lecture15/TimeHereClient.java 
 +</code>
  
 =====  Lecture Content ===== =====  Lecture Content =====
Line 403: Line 403:
   * [[#The key business tier services]]   * [[#The key business tier services]]
   * [[#The Java solution: Enterprise Java Beans]]   * [[#The Java solution: Enterprise Java Beans]]
-  * [[#Reimplementing PerfectTime as a session bean]] +  * [[#Reimplementing TimeHere as a session bean]]
-  * [[#Is the Java solution a good solution?]] +
- +
- +
- +
----- +
- +
-[[Home]] | [[lecture14|Previous Lecture]] | [[Lectures]] | [[lecture16|Next Lecture]]  +
- +
-=====  Lecture Content ===== +
- +
-  * [[#An example]] +
-  * [[#The key business tier services]] +
-  * [[#The Java solution: Enterprise Java Beans]] +
-  * [[#Reimplementing PerfectTime as a session bean]]+
   * **[[#Is the Java solution a good solution?]]**   * **[[#Is the Java solution a good solution?]]**
  
 +===== Is the Java Solution a Good Solution? =====
  
 +  * During 2004, the developer community decided that the answer is probably no.
 +  * EJB 3 was a response to this, and uses annotations to simplify it.
 +  * We will discuss this issue, and some of the alternatives in the final lecture.
 +  * The TimeHere session EJB example gives a flavour of the complexity! To run the example, you’ll need an implementation of a Java EE container (e.g. Glassfish) to which you can deploy the bean.
  
-===== Is the Java Solution a Good Solution? ===== +=====  Lecture Summary =====
-During 2004, the developer community decided that the answer is probably no. +
-We will discuss this issue, and some of the alternatives in the final lecture. +
-Eckel’s PerfectTime session EJB example gives a flavour of the complexity! To run the example, you’ll need an implementation of a J2EE container to which you can deploy the bean. +
-It’s a good example of a bad design if nothing else! +
- +
-=====  Lecture Content =====+
  
   * [[#An example]]   * [[#An example]]
   * [[#The key business tier services]]   * [[#The key business tier services]]
   * [[#The Java solution: Enterprise Java Beans]]   * [[#The Java solution: Enterprise Java Beans]]
-  * [[#Reimplementing PerfectTime as a session bean]]+  * [[#Reimplementing TimeHere as a session bean]]
   * [[#Is the Java solution a good solution?]]   * [[#Is the Java solution a good solution?]]
  
Line 440: Line 425:
 ---- ----
  
-[[Home]] | [[lecture14|Previous Lecture]] | [[Lectures]] | [[lecture16|Next Lecture]] +[[Home]] | [[lecture15|Previous Lecture]] | [[Lectures]] | [[lecture16|Next Lecture]]  
 + 
at-m42/lecture15.1240654179.txt.gz · Last modified: 2011/01/14 12:24 (external edit)