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Sun Java System Application Server Platform Edition 8.1 2005Q2 Update 2 Upgrade and Migration Guide

Chapter 6 Migrating from Application Server 6.x/7.x to Application Server 8.1

This chapter describes the considerations and strategies that are needed when moving J2EE applications from Application Server 6.x and Application Server 7 to the Application Server Platform Edition 8.1product line. However, Application Server 8.1 provides backward compatibility standard, with Application Server 7 as the baseline. That is, applications developed in Application Server 7 can be deployable directly to Application Server 8.1 with minimum or no changes.

The sections that follow describe issues that arise while migrating the main components of a typical J2EE application from Application Server 6.x/7.x to Application Server Platform Edition 8.1.

This chapter contains the following sections:

The migration issues described in this chapter are based on an actual migration that was performed for a J2EE application called iBank, a simulated online banking service, from Application Server 6.x to Sun Java System Application Server 8.1. This application reflects all aspects of a traditional J2EE application.

The following areas of the J2EE specification are covered by the iBank application:

The iBank application is described in detail in Chapter 9, iBank Application Specification.

Migrating Deployment Descriptors

There are two types of deployment descriptors, namely, Standard Deployment Descriptors and Runtime Deployment Descriptors. Standard deployment descriptors are portable across J2EE platform versions and vendors and does not require any modifications. Currently, there are exceptions due to standards interpretation. The following table lists such deployment descriptors.

Source Deployment Descriptor  

Target Deployment Descriptor  

ejb-jar.xml - 1.1

ejb-jar.xml - 2.0

web.xml

web.xml

application.xml

application.xml

The J2EE standard deployment descriptors ejb-jar.xml, web.xml and application.xml are not modified significantly. However, the ejb-jar.xml deployment descriptor is modified to make it compliant with EJB 2.0 specification in order to make the application deployable on Sun Java System Application Server 8.1.

Runtime deployment descriptors are vendor and product specific and are not portable across application servers due to difference in their format. Hence, deployment descriptors require migration. This section describes how you can manually create the runtime deployment descriptors and migrate relevant information.

The following table summarizes the deployment descriptor migration mapping.

Source Deployment Descriptor  

Target Deployment Descriptor  

ias-ejb-jar.xml

sun-ejb-jar.xml

<bean-name>-ias-cmp.xml

sun-cmp-mappings.xml

ias-web.xml

sun-web.xml

The standard deployment descriptors of Application Server 6.x needs modification when moving to Application Server 8.1 because of non-conformance with the DTDs.

A majority of the information required for creating sun-ejb-jar.xml and sun-web.xml comes from ias-ejb-jar.xml and ias-web.xml respectively. However, there is some information that is required and extracted from the home interface (java file) of the CMP entity bean, in case the sun-ejb-jar.xml being migrated declares one. This is required to build the <query-filter> construct inside the sun-ejb-jar.xml, which requires information from inside the home interface of that CMP entity bean. If the source file is not present during the migration time, the <query-filter> construct is created, but with missing information (which manifests itself in the form of REPLACE ME phrases in the migrated sun-ejb-jar.xml).

Additionally, if the ias-ejb-jar.xml contains a <message-driven> element, then information from inside this element is picked up and used to fill up information inside both ejb-jar.xml and sun-ejb-jar.xml. Also, inside the <message-driven> element of ias-ejb-jar.xml, there is an element <destination-name>, which holds the JNDI name of the topic or queue to which the MDB listens. In Application Server 6.5, the naming convention for this jndi name is cn=<SOME_NAME>. Since a JMS Topic or Queue with this name is not deployable on Application Server, the application server changes this to <SOME_NAME>, and inserts this information in the sun-ejb-jar.xml. This change must be reflected for all valid input files, namely, all .java, .jsp and .xml files. Hence, this JNDI name change is propagated across the application, and if some source files that contain reference to this jndi-name are unavailable, the administrator must make the changes manually so that the application becomes deployable.

Migrating Web Applications

Application Server 6.x support servlets (Servlet API 2.2), and JSPs (JSP 1.1). Sun Java System Application Server 8.1 supports Servlet API 2.4 and JSP 2.0.

Within these environments it is essential to group the different components of an application (servlets, JSP and HTML pages and other resources) together within an archive file (J2EE-standard Web application module) deploying it on the application server.

According to the J2EE specification, a Web application is an archive file (WAR file) with the following structure:

Migrating Java Server Pages and JSP Custom Tag Libraries

Application Server 6.x complies with the JSP 1.1 specification and Application Server 8.1 complies with the JSP 2.0 specification.

JSP 2.0 specification contains many new features, as well as updates to the JSP 1.1 specification.

These changes are enhancements and are not required to migrate to JSP pages from JSP 1.1 to 2.0.

The implementation of JSP custom tag libraries in Application Server 6.x complies with the J2EE specification. Consequently, migrating JSP custom tag libraries to the Application Server Platform Edition 8.1does not pose any particular problem, nor require any modifications.

Migrating Servlets

Application Server 6.x supports the Servlet 2.2 API. Sun Java System Application Server 8.1 supports the Servlet 2.4 API.

Servlet API 2.4 leaves the core of servlets relatively untouched. Most changes are concerned with adding new features outside the core.

The most significant features are:

These changes are enhancements and are not required to be made when migrating servlets from Servlet API 2.2 to 2.4.

However, if the servlets in the application use JNDI to access resources in the J2EE application (such as data sources or EJBs), some modifications might be needed in the source files or in the deployment descriptor.

These modifications are explained in detail in the following sections:

One last scenario might require modifications to the servlet code. Naming conflicts can occur with Application Server 6.x if a JSP page has the same name as an existing Java class. In this case, the conflict must be resolved by modifying the name of the JSP page in question. This in turn can mean editing the code of the servlets that call this JSP page. This issue is resolved in Application Server as it uses a new class loader hierarchy. In the new version of the application server, for a given application, one class loader loads all EJB modules and another class loader loads web module. As these two loaders do not talk with each other, there is no naming conflict.

Obtaining a Data Source from the JNDI Context

To obtain a reference to a data source bound to the JNDI context, look up the data source’s JNDI name from the initial context object. The object retrieved in this way is then be cast as a DataSource type object:

ds = (DataSource)ctx.lookup(JndiDataSourceName);

For detailed information, refer to section “Migrating JDBC Code.”

Declaring EJBs in the JNDI Context

Please refer to section Declaring EJBs in the JNDI Context in Chapter 5, Migrating from EJB 1.1 to EJB 2.0.”

Potential Servlets and JSP Migration Problems

The actual migration of the components of a Servlet / JSP application from Application Server 6.x to Application Server 8.1does not require any modifications to the component code.

If the Web application is using a server resource, a DataSource for example, the Application Server requires that this resource to be declared inside the web.xml file and, correspondingly, inside the sun-web.xml file. To declare a DataSource called jdbc/iBank, the <resource-ref> tag in the web.xml file is as follows:

<resource-ref>
   <res-ref-name>jdbc/iBank</res-ref-name>
   <res-type>javax.sql.XADataSource</res-type>
   <res-auth>Container</res-auth>
   <res-sharing-scope>Shareable</res-sharing-scope>
</resource-ref>

The corresponding declaration inside the sun-web.xml file looks like this:

<?xml version="1.0" encoding="UTF-8"?>
<! DOCTYPE FIX ME: need confirmation on the DTD to be used for this file
<sun-web-app>
   <resource-ref>
      <res-ref-name>jdbc/iBank</res-ref-name>
      <jndi-name>jdbc/iBank</jndi-name>
   </resource-ref>
 </sun-web-app>

Migrating Web Application Modules

Migrating applications from Application Server 6.x to Sun Java System Application Server 8.1 does not require any changes to the Java code or Java Server Pages. However, you must change the following files:

The Application Server adheres to J2EE 1.4 standards, according to which, the web.xml file inside a WAR file must comply with the revised DTD at http://java.sun.com/dtd/web-app_2_3.dtd. This DTD is a superset of the previous versions’ DTD, hence only the <! DOCTYPE definition needs to be changed inside the web.xml file, which is to be migrated. The modified <! DOCTYPE declaration looks like:

<!DOCTYPE web-app PUBLIC "-//Sun Microsystems, Inc.// 
                        DTD Web Application 2.3//EN" 
                        "http://java.sun.com/dtd/web-app_2_3.dtd">

In Application Server Platform Edition 8.1, the name of this file is changed to sun-web.xml.

This XML file must declare the Application Server-specific properties and resources that are required by the Web application.

See Potential Servlets and JSP Migration Problems for information about important inclusions to this file.

If the ias-web.xml of the Application Server 6.5 application is present and does declare Application Server 6.5 specific properties, then this file needs to be migrated to Application Server standards. The DTD file name has to be changed to sun-web.xml. For more details, see URL http://wwws.sun.com/software/dtd/appserver/sun-web-app_2_4-1.dtd

Once you have made these changes to the web.xml and ias-web.xml files, the Web application (WAR file) can be deployed from the Application Server’s deploytool GUI interface or from the command line utility asadmin. The deployment command must specific the type of application as web.

Invoke the asadmin command line utility by running asadmin.bat file or the asadmin.sh script in the Application Server’s bin directory.

The command at the asadmin prompt is:

asadmin deploy -u username -w password
-H hostname 
-p adminport 
--type web 
[--contextroot contextroot] 
[--force=true] 
[--name component-name] 
[--upload=true] filepath

Migrating Enterprise EJB Modules

Application Server 6.x supports EJB 1.1, and the Application Server supports EJB 2.0. Therefore, both can support:

EJB 2.0, however, introduces a new type of enterprise bean, called a message-driven bean (MDB).

J2EE 1.4 specification dictates that the different components of an EJB must be grouped together in a JAR file with the following structure:

Application Server 6.x use this archive structure. However, the EJB 1.1 specification leaves each EJB container vendor to implement certain aspects as they see fit:

EJB Migration

As mentioned in Chapter 4, Understanding Migration, while Application Server 6.x supports the EJB 1.1 specification, Application Server also supports the EJB 2.0 specification. The EJB 2.0 specification introduces the following new features and functions to the architecture:

Although the EJB 1.1 specification continues to be supported in the Application Server, the use of the EJB 2.0 architecture is recommended to leverage its enhanced capabilities.

For detailed information on migrating from EJB 1.1 to EJB 2.0, please refer to Chapter 5, Migrating from EJB 1.1 to EJB 2.0

EJB Changes Specific to Application Server Platform Edition 8.1

Migrating EJBs from Application Server 6.x to Application Server 8.1 is done without making any changes to the EJB code. However, the following DTD changes are required.

Session Beans

Note –

To avoid changing JNDI names throughout the application, declare the JNDI name of the EJB as ejb/<ejb-name> inside the <jndi-name> tag.

Entity Beans

Message Driven Beans

Application Server provides seamless Message Driven Support through the tight integration of Sun Java System Message Queue with the Application Server, providing a native, built-in JMS Service.

This installation provides Application Server with a JMS messaging system that supports any number of Application Server instances. Each server instance, by default, has an associated built-in JMS Service that supports all JMS clients running in the instance.

Both container-managed and bean-managed transactions, as defined in the Enterprise JavaBeans Specification, v2.0, are supported.

Message Driven Bean support in iPlanet Application Server was restricted to developers, and used many of the older proprietary APIs. Messaging services were provided by iPlanet Message Queue for Java 2.0. An LDAP directory was also required under iPlanet Application Server to configure the Queue Connection Factory object.

The QueueConnectionFactory, and other elements required to configure Message Driven Beans in Application Server are now specified in the ejb-jar.xml file.

For more information on the changes to deployment descriptors, see Migrating Deployment Descriptors For information on Message Driven Beans see Using Message-Driven Beans in Sun Java System Application Server Platform Edition 8.1 2005Q2 Update 2 Developer’s Guide.

Migrating Enterprise Applications

According to the J2EE specifications, an enterprise application is an EAR file, which must have the following structure:

In the application deployment descriptor, the modules that make up the enterprise application and the Web application’s context root are defined.

Application server 6.x and the Application Server 8.1support the J2EE model wherein applications are packaged in the form of an enterprise archive (EAR) file (extension .ear). The application is further subdivided into a collection of J2EE modules, packaged into Java archives (JAR files, which have a .jar file extension) and EJBs and Web archives (WAR files, which have a .war file extension) for servlets and JSPs.

It is essential to follow the steps listed here before deploying an enterprise application:

ProcedureTo Build an EAR File

Steps

  1. Package EJBs in one or more EJB modules.

  2. Package the components of the Web application in a Web module.

  3. Assemble the EJB modules and Web modules in an enterprise application module.

  4. Define the name of the enterprise application’s root context, which will determine the URL for accessing the application.

    The Application Server uses a newer class loader hierarchy than Application Server 6.x does. In the new scheme, for a given application, one class loader loads all EJB modules and another class loader loads Web modules. These two are related in a parent child hierarchy where the JAR module class loader is the parent module of the WAR module class loader. All classes loaded by the JAR class loader are available/accessible to the WAR module but the reverse is not true. If a certain class is required by the JAR file as well as the WAR file, then the class file must be packaged inside the JAR module only. If this guideline is not followed it can lead to class conflicts.

Application Root Context and Access URL

There is a major ”difference between Application Server 6.x and the Application Server, concerning the applications access URL (root context of the application’s Web module. If AppName is the name of the root context of an application deployed on a server called hostname, the access URL for this application will differ depending on the application server used:

The TCP port used as default by Application Server is port 8080.

Although the difference in access URLs between Application Server 6.x and the Application Server might appear minor, it can be problematic when migrating applications that make use of absolute URL references. In such cases, it is necessary to edit the code to update any absolute URL references so that they are no longer prefixed with the specific marker used by the Web Server plug-in for Application Server 6.x.

Applications With Form-based Authentication

Applications developed on Application Server 6.5 that use form-based authentication can pass the request parameters to the Authentication Form or the Login page. The Login page could be customized to display the authentication parameters based on the input parameters.

For example:

http://gatekeeper.uk.sun.com:8690/NASApp/test/secured/page.jsp?arg1=test&arg2=m

Application Server 8.1 does not support the passing of request parameters while displaying the Login page. The applications that uses form-based authentication, which passes the request parameters can not be migrated to Application Server 8.1. Porting such applications to Application Server 8.1 requires significant changes in the code. Instead, you can store the request parameter information in the session, which can be retrieved while displaying the Login page.

The following code example demonstrates the workaround:

Before changing the code in 6.5:

---------index-65.jsp -----------
<%@page contentType="text/html"%>
<html>
<head><title>JSP Page</title></head>
<body>
go to the <a href="secured/page.htm">secured a rea</a>
</body>
</html>
----------login-65.jsp--------------
<%@page contentType="text/html"%>
<html>
<head> </head>
<body>
<!-- Print login form -->
<h3>Parameters</h3><br>
out.println("arg1 is " + request.getParameter("arg1"));
out.println("arg2 is " + request.getParameter("arg2"));
</body>
</html>

After changing the code in Application Server 8.1:

---------index-81.jsp -----------
<%@page contentType="text/html"%>
<html>
<head><title>JSP Page</title></head>
<body>
<%session.setAttribute("arg1","test"); %>
<%session.setAttribute("arg2","me"); %>
go to the <a href="secured/page.htm">secured area</a>
</body>
</html>

The index-81.jsp shows how you can store the request parameters in a session.

----------login-81.jsp--------------
<%@page contentType="text/html"%>
<html>
<head> </head>
<body>
<!-- Print login form -->
<h3>Parameters</h3><br>
<!--retrieving the parameters from the session -->
out.println("arg1 is"+(String)session.getAttribute("arg1"));
out.println("arg2 is” + (String)session.getAttribute("arg2"));
</body>
</html>

Migrating Proprietary Extensions

A number of classes proprietary to the Application Server 6.x environment might have been used in applications. Some of the proprietary packages used by Application Server 6.x are listed below:

These APIs are not supported in the Application Server. Applications using any classes belonging to the above package must be rewritten to use standard J2EE APIs. Applications using custom JSP tags and UIF framework also need to be rewritten to use standard J2EE APIs.

For a sample migration walkthrough using the iBank application, see Chapter 7, Migrating a Sample Application - an Overview.

Migrating UIF

The Application Server does not support the use of Unified Integration Framework (UIF) API for applications. Instead, it supports the use of J2EE Connector Architecture (JCA) for integrating the applications. However, the applications developed in Application Server 6.5 use the UIF. In order to deploy such applications to the Application Server, migrate the UIF to the J2EE Connector Architecture. This section discusses the prerequisites and steps to migrate the applications using UIF to Application Server.

Before migrating the applications, ensure that the UIF is installed on Application Server 6.5. To check for the installation, follow either of the following approaches:

Checking in the Registry Files

UIF is installed as a set of application server extensions. They are registered in the application server registry during the installation. Search for the following strings in the registry to check whether UIF is installed.

Extension Name Set:

The registry file on Solaris Operating Environment can be found at the following location:

AS_HOME/AS/registry/reg.dat

Checking for UIF Binaries in Installation Directories

UIF installers copy specific binary files in to the application server installation. Successfully finding the files listed below, indicates that UIF is installed.

The location of the following files on Solaris and Windows is:

AS_HOME/AS/APPS/bin

List of files to be searched on Solaris:

List of files to be searched on Windows:

Before migrating the UIF to Application Server, ensure that the UIF API is being used in the applications. To verify its usage:

Contact appserver-migration@sun.com for information about UIF migration to the Application Server.

Migrating JDBC Code

With the JDBC API, there are two methods of database access:

Note –

Application Server does not support the Native Type 2 JDBC drivers bundled with Application Server 6.x. Code that uses the Type 2 drivers to access third party JDBC drivers, must be manually migrated.

Establishing Connections Through the DriverManager Interface

Although this database access method is not recommended, as it is obsolete and is not very effective, there can be some applications that still use this approach.

In this case, the access code is similar to the following:

public static final String driver = "oracle.jdbc.driver.OracleDriver";
public static final String url = 
  "jdbc:oracle:thin:tmb_user/tmb_user@iben:1521:tmbank";
Class.forName(driver).newInstance();
Properties props = new Properties();
props.setProperty("user", "tmb_user");
props.setProperty("password", "tmb_user");
Connection conn = DriverManager.getConnection(url, props);

This code can be fully ported from Application Server 6.x to Application Server, as long as the Application Server is able to locate the classes needed to load the right JDBC driver. In order to make the required classes accessible to the application deployed in the Application Server, place the archive (JAR or ZIP) for the driver implementation in the /lib directory of the Application Server installation directory.

Modify the CLASSPATH by setting the path for the driver through the Admin Console GUI.

Using JDBC 2.0 Data Sources

Using JDBC 2.0 data sources to access a database provides performance advantages, such as transparent connection pooling, enhanced productivity by simplifying code and implementation, and code portability.

If there is a datasource by the name ”xyz’ on Application Server 6.x application and you do not want any impact on your JNDI lookup code, make sure that the datasource you create for Application Server 8.1 is prefixed with jdbc. For example: jdbc/xyz.

For information on configuring JDBC Datasources, see Chapter 3, JDBC Resources, in Sun Java System Application Server Platform Edition 8.1 2005Q2 Update 2 Administration Guide.

Looking Up the Data Source Via JNDI To Obtain a Connection

To obtain a connection from a data source, do the following:

ProcedureTo Connect to a Data Source

Steps

  1. Obtain the initial JNDI context.

    To guarantee portability between different environments, the code used to retrieve an InitialContext object (in a servlet, in a JSP page, or an EJB) is as follows:

    InitialContext ctx = new InitialContext();

  2. Use a JNDI lookup to obtain a data source reference.

    To obtain a reference to a data source bound to the JNDI context, look up the data source’s JNDI name from the initial context object. The object retrieved in this way is cast as a DataSource type object:

    ds = (DataSource)ctx.lookup(JndiDataSourceName);

  3. Use the data source reference to obtain the connection.

    This operation requires the following line of code:

    conn = ds.getConnection();

    Application Server 6.x and Application Server both follow these technique to obtain a connection from the data source.

Migrating Rich Clients

This section describes the steps for migrating RMI/IIOP and ACC clients developed in Planet Application Server 6.x to the Application Server.

Authenticating a Client in Application Server 6.x

Application Server 6.x provides a client-side callback mechanism that enables applications to collect authentication data from the user, such as the username and the password.The authentication data collected by the iPlanet CORBA infrastructure is propagated to the application server via IIOP.

If ORBIX 2000 is the ORB used for RMI/IIOP, portable interceptors implement security by providing hooks, or interception points, which define stages within the request and reply sequence.

Authenticating a Client in Sun Java System Application Server 8.1

The authentication is done based on JAAS (Java Authorization and Authentication System API). If a client does not provide a CallbackHandler, then the default CallbackHandler, called the LoginModule, is used by the ACC to obtain the authentication data.

For detailed instructions on using JAAS for authentication, see Chapter 9, Configuring Security, in Sun Java System Application Server Platform Edition 8.1 2005Q2 Update 2 Administration Guide.

Using ACC in Application Server 6.x and Sun Java System Application Server 8.1

In Application Server 6.x, no separate appclient script is provided. You are required to place the iasacc.jar file in the classpath instead of the iascleint.jar file. The only benefit of using the ACC for packaging application clients in 6.x is that the JNDI names specified in the client application are indirectly mapped to the absolute JNDI names of the EJBs.

In case of Application Server 6.x applications, a stand-alone client uses the absolute name of the EJB in the JNDI lookup. That is, outside an ACC, the following approach is used to lookup the JNDI:

initial.lookup(“ejb/ejb-name”);
initial.lookup(“ejb/module-name/ejb-name”);

If your application was developed using Application Server 6.5 SP3, you would have used the prefix “java:comp/env/ejb/” when performing lookups via absolute references.

initial.lookup("java:comp/env/ejb/ejb-name");

In Sun Java System Application Server 8.1, the JNDI lookup is done on the jndi-name of the EJB. The absolute name of the ejb must not be used. Also, the prefix, java:comp/env/ejb is not supported in Sun Java System Application Server 8.1. Replace the iasclient.jar, iasacc.jar, or javax.jar JAR files in the classpath with appserv-ext.jar.

If your application provides load balancing capabilities, in Sun Java System Application Server 8.1, load balancing capabilities are supported only in the form of S1ASCTXFactory as the context factory on the client side and then specifying the alternate hosts and ports in the cluster by setting the com.sun.appserv.iiop.loadbalancingpolicy system property as follows:

com.sun.appserv.iiop.loadbalancingpolicy=

roundrobin,host1:port1,host2:port2,...,

This property provides the administrator with a list of host:port combinations to round robin the ORBs. These host names can also map to multiple IP addresses. If this property is used along with org.omg.CORBA.ORBInitialHost and org.omg.CORBA.ORBInitialPort as system properties, the round robin algorithm will round robin across all the values provided. If, however, a host name and port number are provided in your code, in the environment object, that value overrides any other system property settings.

The Provider URL to which the client is connected in Application Server 6.5 is the IIOP host and port of the CORBA Executive Engine (CXS Engine). In case of Sun Java System Application Server 8.1, the client needs to specify the IIOP listener Host and Port number of the instance. No separate CXS engine exists in Sun Java System Application Server 8.1.

The default IIOP port is 3700 in Sun Java System Application Server 8.1; the actual value of the IIOP Port can be found in the domain.xml configuration file.