This chapter describes the considerations and strategies that are needed when moving Java EE applications from Application Server 6.x,, 7.x, or from servers such as Weblogic, Websphere servers to the Application Server Platform Edition 9 product line.
The sections that follow describe issues that arise while migrating the main components of a typical Java EE application from other application servers to Application Server Platform Edition 9.
This chapter contains the following sections:
Several migration issues described in this chapter are based on an actual migration that was performed for a Java EE application called iBank, a simulated online banking service, from Application Server 6.x to Sun Java System Application Server 9. This application reflects all aspects of a traditional Java EE application.
The following areas of the Java EE specification are covered by the iBank application:
Servlets, especially with redirection to JSP pages (model-view-controller architecture)
JSP pages, especially with static and dynamic inclusion of pages
JSP custom tag libraries
Creation and management of HTTP sessions
Database access through the JDBC API
Enterprise JavaBeans: Stateful and Stateless session beans, CMP and BMP entity beans.
Assembly and deployment in line with the standard packaging methods of the J2EE application
There are two types of deployment descriptors, namely, Standard Deployment Descriptors and Runtime Deployment Descriptors. Standard deployment descriptors are portable across Java EE 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 in Sun Application 6.x /7.x
Source Deployment Descriptor in Websphere 4.0 /5.x
Source Deployment Descriptor in WebLogic 4.0 /5.x
Target Deployment Descriptor in 9
The Java EE standard deployment descriptors ejb-jar.xml, web.xml and application.xml are not modified and therefore need not be changed.
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. You can use the Migration Tool for Application Server 9 to migrate these deplyment descriptors.
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.
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 (Java EE-standard Web application module) deploying it on the application server.
According to the Java EE specification, a Web application is an archive file (WAR file) with the following structure:
A root directory containing the HTML pages, JSP, images and other static resources of the application.
A META-INF/ directory containing the archive manifest file MANIFEST.MF containing the version information for the SDK used and, optionally, a list of the files contained in the archive.
A WEB-INF/ directory containing the application deployment descriptor (web.xml file) and all the Java classes and libraries used by the application, organized as follows:
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 9does not pose any particular problem, nor require any modifications.
Application Server 6.x supports the Servlet 2.2 API. Sun Java System Application Server 9 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:
Servlets now require JDK 1.2 or later
Filter mechanisms have been created
Application lifecycle events have been added
Internationalization support has been added
Error and security attributes have been expanded
HttpUtils class has been deprecated
Several DTD behaviors have been expanded and clarified
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 Java EE 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.
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.”
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 applications from Application Server 6.x to Sun Java System Application Server 9 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 9, 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.
asadmin deploy -u username -w password -H hostname -p adminport --type web [--contextroot contextroot] [--force=true] [--name component-name] [--upload=true] filepath
Stateful or stateless session beans
Entity beans with bean-managed persistence (BMP), or container-managed persistence (CMP)
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:
META-INF/ directory with an XML deployment descriptor named ejb-jar.xml
The .class files corresponding to the home interface, remote interface, the implementation class, and the auxiliary classes of the bean with their package
Application Server 6.x uses this archive structure. However, the EJB 1.1 specification leaves each EJB container vendor to implement certain aspects as they see fit:
Database persistence of CMP EJBs (particularly the configuration of mapping between the bean’s CMP fields and columns in a database table).
Implementation of the custom finder method logic for CMP beans.
Application Server 6.x/7.x and Application Server 9do not handle migrations in the same way, which means that some XML files must be modified:
The <!DOCTYPE definition must be modified to point to the latest DTD URL (in the case of J2EE standard DDs, like ejb-jar.xml).
Replace the ias-ejb-jar.xml file with the modified version of this file (for example, file sun-ejb-jar.xml, which is created manually according to the DTDs). For more information, see http://wwws.sun.com/software/dtd/appserver/sun-ejb-jar_2_1-1.dtd
Replace all the <ejb-name>-ias-cmp.xml files with one sun-cmp-mappings.xml file, which is created manually. For more information, see http://wwws.sun.com/software/dtd/appserver/sun-cmp-mapping_1_2.dtd
Optionally, for CMP entity beans, use the capture-schema utility in the Application Server’s bin directory to generate the dbschema. Then place it above the META-INF directory for the entity beans.
As mentioned in Chapter 4, Understanding Migration, while Application Server 6.x supports the EJB 1.1 specification and Application Server 8 supports EJB 2.0, Application Server 9 supports the EJB 3.0 specification.
Although the EJB 1.1 and 2.0 specification continues to be supported in the Application Server, the use of the EJB 3.0 architecture is recommended to leverage its enhanced capabilities.
For detailed information on migrating from EJB 1.1 to 2.0 to EJB 3.0, please refer to Chapter 5, Migrating EJB
A META-INF/ directory containing the XML deployment descriptor of the J2EE application called application.xml
The JAR and WAR archive files for the EJB modules and Web module of the enterprise application, respectively
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 9support 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:
Package EJBs in one or more EJB modules.
Package the components of the Web application in a Web module.
Assemble the EJB modules and Web modules in an enterprise application module.
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.
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:
With Application Server 6.x, which is always used jointly with a Web front-end, the access URL for the application takes the following form (assuming the Web server is configured on the standard HTTP port, 80):
With the Application Server, the URL takes the form:
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 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.
Application Server 9 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 9. Porting such applications to Application Server 9 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 9:
---------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>
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.
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:
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:
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:
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:
Check for the usage of netscape.bsp package name in the Java sources
Check for the usage of access_cBSPRuntime.getcBSPRuntime method in the sources. You must call this method to acquire the UIF runtime.
Contact email@example.com for information about UIF migration to the Application Server.
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.
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 8, Configuring Security, in Sun Java System Application Server Platform Edition 9 Administration Guide.
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:
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.
In Sun Java System Application Server 9, 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 9. 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 9, 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:
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 9, 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 9.
The default IIOP port is 3700 in Sun Java System Application Server 9; the actual value of the IIOP Port can be found in the domain.xml configuration file.