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PopQuiz IBM Exam #488: WebSphere Application Server SSE 4.0 30 questions. Answers and explanations can be found at the end of the quiz. courtesy of Whizlabs Software Questions 1. A web application modeling a chess game is to be developed. The application is to be built on J2EE platform using different web components like EJB's, JSP's, Servlets. Which of the following type of EJBs is most suited for representing a game of chess?
2. You are responsible for designing and developing various web applications for your organization. You have an option to choose from various technologies and EJB is one of them. In which of the following scenarios listed below, EJB is advisable to be used?
3. In which of the following scenarios would you use BMP in preference to CMP for developing an enity bean? (Choose 3 correct answers)
4. Which of the following are true for primary keys of enity beans?
5. Which of the following is true about comparing beans for identity?
6. All JSP pages, by default take part in an HTTP session. Which of the following is true regarding the values which can be put into a session?
7. JSP provides certain implicit objects accessible within the JSP. These objects do not need to be declared or instantiated by the JSP author, but are provided by the web container/server. Each of these objects can be associated with a scope attribute which defines where there is a reference to the object and when that reference is removed. Which of the following are true combinations of an object and corresponding scope?
8. Which of the following statements is true regarding the two syntax shown below for using a JavaBean component in JSP page? a) b.) Choices:
9. The shared resources created by the init() method should be declared ____, in case the server implementation uses multiple instances of a single servlet class. (Fill in the blank)
10. Consider a shopping cart web application which uses session management, implemented using Servlet API (HttpSession interface). Whenever a new user logins, his name (String type) is stored in a session using the setAttribute() method of the HttpSession interface. The variable used to store the user name is "myName". To retrieve the user name from the session, which of the following lines of code is correct, assuming request and response are arguments of type HttpServletRequest and HttpServletResponse respectively, to the service() method of the servlet?
11. While designing and developing servlets you need not worry about the thread safety of class variables. True/False?
12. Which of the following use of tag for a JSP which uses java.sun.com.MyBean JavaBean component are correct? Choices:
13. Which of the following are the methods for state/session management in the context of Servlets?
14. Which of the following needs to be done to end the client session of a Stateful Session Bean?
15. If no matching beans are found, the findByPrimaryKey method defined in the home object of an entity bean will:
16. A datasource has been created and configured (in WebSphere Application Server, Advanced Single Server Edition) to have an orphanTimeout of 30. A servlet acquires a connection from that datasource and holds the connection for 2 minutes without using it. If the servlet attempts to use the connection after that, which statement is true?
17. Which of the following transaction attributes can be specified only for session beans and also cannot be specified for individual methods ?
18. A session bean's business method has the transaction attribute set to 'Required'. A client attempts to invoke the bean method without a transaction context. What will be the result?:
19. In the EJB Development Environment of IBM Visual Age for Java, an association is a relationship that exists between:
20. In which of the following situations do we need to regenerate the deployed code for an enterprise bean in Visual Age for Java?
21. Which of the following are true when trying to export and later import enterprise beans using Visual Age For Java? (Choose 2 right answers).
22. Which of the following cannot be performed using the Application Assembly tool?
23. A new Web module has been added to an existing application running under WebSphere application server. Which of the following needs to be done for the changes to take effect ?
24. WebSphere AEs supports different methods for mapping CMP EJBs to a database. You want EJB fields to be created for the fields in a database table. Which of these methods will you choose?
25. Which of the following is false about the SEAppInstall tool of the WebSphere Application Server, Advanced Single Server Edition?
26. An enterprise application which consists of servlets and EJBs has been installed and is running in WebSphere Application Server, Advanced Single Server Edition After making some changes to the application , the changes are applied and saved without restarting the server or application. If the application is tested now , which of the following changes would have taken effect?
27. Which of the following statements are true about implementing custom finder helpers for CMP entity beans in WebSphere Application Server, Advanced Single Server Edition?
28. Which of the following are valid values for the module visibility property in WebSphere Application Server, Advanced Single Server Edition?
29. Which of the following are true for the launchClient batch command in WebSphere Application Server, Advanced Single Server Edition?
30. Which of the following is not a EJB container property in WebSphere Application Server, Advanced Single Server Edition?
Answers 1. Choice D is correct. Stateless session beans are those which do not maintain its state between client calling its method. Every method invocation is treated as a new interaction with the client. On the other hand, stateful session bean maintains a state that is available to client in the subsequent calls. Entity Beans are convenient components for business objects which represent the real life entities. For example, A Customer, A Product, An Order, A Line Item, A Campaign Event, A Quotation etc are some entities that you might have in your CRM application. EJB 2.0 specification introduced a new type of session bean, which is integrated with a Java Messaging Server (JMS) system. These are called Message Driven Beans (MDB). It is possible that the JMS associated with the application server, on receiving any message, would create or invoke a message driven bean. A 'Game of Chess' would be represented by a stateful session bean because with every call to its move() method, the state is changed and between the call to this method the state would be maintained. 2. Choices A, B and D are correct. A transaction is a unit-of-work or a set of tasks that are executed together. Transactions are atomic; in other words, all the tasks in a transaction must be completed together to consider the transaction a success. Transactions are managed automatically, so as a bean developer you don't need to use any APIs to explicitly manage a bean's involvement in a transaction. Simply declaring the transactional attribute at deployment time tells the EJB server how to manage the bean at runtime. Thus choosing EJBs when transaction management is required is a wise decision. Thus choice A is correct. Apart from Transaction Management, the EJB container providers various other facilities like Concurrency Service which is very useful in scenarios where a resource is simultaneosly shared by more than one user. Thus choice B is correct. EJBs provide standard APIs for application development. The application developed on one Application Server can be migrated to another one with little modifications. Also being written in Java, EJB's provide platform independence. A solution like .Net could prove successful in a situation where platform independence is not required and being locked to single vendor is also acceptable. Thus choice C is not correct. If your require your business logic to be protected by a firewall, then you can deploy the web server and application server on separate machines and stick a firewall in the middle. Thus choice D is correct. If your application is just a big GUI to a database--heavy on data logic but no business logic--you could achieve a deployment easily using JSPs with tag libraries connecting to a database via JDBC. Thus EJB is not advisable in this scenario. Thus choice E is not correct. 3. Choices A, B and E are correct. Container managed beans are the simplest to develop because they allow you to focus on the business logic , delegating the responsibility of persistence to the EJB container.The advantage of container managed persistence is that the bean can be defined independent of the database used to store its state. The bean state is stored independently which makes the bean more reusable and flexible across applications. You must use BMP if any of the following is true about an entity bean:The bean's persistent data is stored in more than one data source or the bean's persistent data is stored in a data source that is not supported by the EJB server that you are using. Bean managed persistence is also the alternative to container managed persistence when the deployment tools are inadequate for mapping the bean instance's state to the database. 4. Choices B, C and D are correct. Although primary keys can be primitive wrappers , primary keys cannot be primitive types, because some of the semantics of Ejb interfaces prohibit the use of primitives. All fields in the primary key should be declared public so that the container can read the fields at runtime via java reflection. Since the primary key would be used in remote invocations ,it should be serializable. It should override equals and hashcode methods so that they behave properly when invoked. 5. Choice A is correct. An EJB object is a distributed object stub and therefore contains a lot of networking and other state. As a result, references to 2 EJB objects maybe unequal, even if they both represent the same unique bean. The EJBObject.isIDentical method returns true if two EJB object references represent the same bean, even if the EJB object stubs are different object instances. Since stateless beans do not retain the conversational state, they are considered identical if they are of the same type. But stateful session beans are not considered to be identical just because they are of the same type since they maintain the conversational state of the clients. For entiy beans, if they have the same home and primary key, they are considered to be identical. 6. Choice B is correct. Any valid Java object can be stored in a session. A session object is identified by a session ID which is a unique key. Primitives can't be placed into a session. You need to wrap a primitive first (using a wrapper class, e,g. for int Integer is used to wrap the int variable) to store it into a session. Here is an example which stores an object of type MyObject (user defined object) into a session. The object is identified with the key "obj". <% To retrieve an instance of this object, following code is used: <%MyObject myObj = (MyObject)session.getValue("obj"); %> 7. A, C, D and E are correct choices. The request object has request scope. An object inside a request scope is accessible from all the pages processing the request where the object was created. Thus A is correct. B is incorrect as response is not a valid scope. The valid scopes are: application, session, request and page. The response object has page scope. An object inside a page is accessible only from the page in which it was created. The session object has session scope. An object inside session scope is visible from all the pages belonging to the session in which it was created. Thus C is also correct. The application object has application scope. An object inside an application scope is accessible from all the pages that belong to the particular application. Thus D is also correct. E is correct as page object has page scope. An object inside a page is accessible only from the page in which it was created. F is incorrect as out is not a valid scope. The out object like response also has page scope. 8. A is correct. Both of the above syntax are valid for using a JavaBean component in a JSP page. The second format is used when there is a need to include jsp:setProperty statements, for initializing java bean properties. In both the above formats, the value of the id attribute determines the unique identifier used to refer the bean. The value of the class attribute is the complete path (including package structure) and the bean class name. A JavaBean like any other object in a JSP page has an associated scope attribute, defined by the scope variable, which determines where there is a reference to the object and when that reference is removed. Here is an example which uses MyBean JavaBean class in mypackage package having an application scope, identified by "myBean." 9. The correct answer is Static. Depending on the server implementation, the server may create a single instance to service all client requests or it may create a pool of instances. In case, the server creates a pool of instances, the instance variables will not be shared by all requests, as each instance will have the copy of its variables. Thus for shared resources to be shared across all requests, they should be declared static as static variables (or class variables) are global variables; there will be only variable for all instances. For example, a database connection object is declared as static to be shared across all instances. 10. E is the correct choice. Choice C and D are incorrect as getSession() is the method of HttpServletRequest interface. Choice B is incorrect as the syntax used here is incorrect; the input argument to getAttribute() method is of String type ("myName" should be used instead of myName). Choice A is incorrect as the return type of getAttribute method is Object and thus explicit casting is needed for assignment to string. The correct code will be : String userName = (String)request.getSession().getAttribute("myName"); 11. Choice B (False) is correct. The class variables are not thread safe. Since there is only one class variable for each instance of a servlet, multiple or concurrent servlet requests will share the class variable. Class variables will be shared between service() threads as well as between different instances of the servlet class. Even the SingleThreadModel interface does not prevent synchronization problems that result from servlets accessing shared resources such as static class variables or classes outside of the scope of the servlet. Thus the above statement is incorrect. 12. Choices B and C are correct. A jsp:useBean action associates an instance of a Java programming language object defined within a given scope and available with a given id with a newly declared scripting variable of the same id . Following is the syntax of the jsp:useBean action: where beandetails can be one of:
Following is the description of various attributes: a) id - The case sensitive name used to identify the object instance. b) scope - The scope within which the reference is available. The default value is page. c) class - The fully qualified (including package name) class name. d) beanName - The name of a Bean, as you would supply to instantiate() method in the java.beans.Beans class. This attribute can also be a request time expression. e) type - This optional attribute specifies the type of the class, and follows standard java casting rules. The type must be a superclass, an interface, or the class itself. The default value is the same as the value of the class attribute. From the rules above, we can say:
13. A, B, C and E are correct choices. State management is the ability to maintain client's current state by passing client-specific information between the client and the server. In contrast, session management provides an association between the client and the server that allows server to uniquely identify each client. This association persists across the requests for a specified period of time. Allowing clients to select their background color of an their html page is an example of state management. With state management, the client identity can't be maintained. For e.g., two clients select red as their background color. With only state management, the server can determine the preferred background color for each of these clients but it cannot distinguish one client from the other. The solution to this is the session management, which is the superset of state management and maintains both state as well as identity. Rewritten URLs pass state information between the client and server by embedding information in the URL of all hyperlinks within an HTML document. The information is passed in the query string of a URL in the form of name/value pairs. For example: http://www.whizlabs.com/servlets/SampleServlet?bcolor=blue This method is only effective when the client follows a hyperlink. If a client needs to submit an HTML Form by clicking a button, the Hidden Variables method is used. A hidden variable operates like an HTML input field (e.g., text field) in that when the page is submitted, the client transmits the field's name/value pair to the server. On receiving the client's POST request, the server extracts the value of the variable (using getParameter() or getParameterValues() method of HttpServletRequest interface) and uses it to construct the next HTML document/page. Generally the combination of both rewritten URLs and hidden variables is used to maintain state and session with HTTP. Cookie is a simple mechanism that allows the server to instruct the client to store some amount of state information. In turn, this information is returned to the server with each client request. The session management mechanism in the Servlet API resides in the HttpSession interface. An HttpSession object encapsulates the essential information of an HTTP session, such as a unique session ID and other client-specific information. An HTTP redirect allows the server to respond to a client request with instructions to load a resource at a different location. It is not a mechanism for state/session management. Thus A,B,C and E are correct while D is incorrect. 14. Choice C is correct. The EJBHome.remove() method is responsible for deleting a bean. The argument is either the javax.ejb.Handle of the bean or, if its an enitity bean, its primary key. The Handle is essentially a serializable pointer to a specific bean. For session beans, the EJBHome.remove() on the bean ends the session's service to the client. When EJBHome.remove() is invoked, the remote reference to the session beans becomes invalid and any conversational state maintained by the bean is lost. If for some reason the bean can't be removed, RemoveException is thrown 15. Choice C is correct. findByPrimaryKey is a standard method that all home interfaces for entity beans must support. With Container Managed Persistence , implementations of find methods are generated automatically at deployment time.Find methods that return a single remote reference throw a FinderException if an application error occurs and a ObjectNotFoundException if a matching bean cannot be found. The ObjectNotFoundException is a subtype of FinderException and is only thrown by find methods which return single remote references. Find methods that return an Enumeration or Collection type return an empty collection of no matching beans can be found or throw a FinderException if an application error occurs. 16. Choice A is correct. StaleConnectionException indicates that the connection currently being held is no longer valid. This can occur for numerous reasons, including:
17. Choice A is correct. The transaction attribute defines the transactional manner in which the container invokes enterprise bean methods. If the transaction attribute is set to BeanManaged, it notifies the container that the bean class directly handles transaction demarcation. This attribute value can be specified only for session beans and it cannot be specified for individual bean methods. If the transaction attribute is set to Mandatory, it directs the container to always invoke the bean method within the transaction context associated with the client. If the transaction attribute is set to Supports, it directs the container to invoke the bean method within a transaction context if the client invokes the bean method within a transaction. If the transaction attribute is set to NotSupported, it directs the container to invoke bean methods without a transaction context. 18. Choice A is correct. The transaction attribute defines the transactional manner in which the container invokes enterprise bean methods. This attribute is set for individual methods in a bean. Setting the transaction attribute to Required, directs the container to invoke the bean method within a transaction context. If a client invokes a bean method from within a transaction context, the container invokes the bean method within the client transaction context. If a client invokes a bean method outside of a transaction context, the container creates a new transaction context and invokes the bean method from within that context. The transaction context is passed to any enterprise bean objects or resources that are used by this bean method. 19. Choice A is correct. In the EJB Development Environment, an association is a relationship that exists between two CMP entity beans within an EJB group. There are three main types of association: one-to-one, one-to-many, and many-to-many. In a one-to-one (1:1) association, a CMP entity bean is associated with a single instance of another CMP entity bean. For example, an Employee bean could be associated with only a single instance of an EmployeeID bean, because an employee can have only one employee identifier on file. In a one-to-many (1:M) association, a CMP entity bean is associated with multiple instances of another CMP entity bean. For example, a Department bean could be associated with multiple instances of an Employee bean, because most departments are made up of multiple employees. In a many-to-many (M:M) association, multiple instances of a CMP entity bean are associated with multiple instances of another CMP entity bean. A many-to-many association is created by joining two 1:M associations. 20. Choices C, E and D are correct. You do not need to regenerate the deployed code for an enterprise bean in if an enterprise bean method is changed or a user-added method of the enterprise bean is changed. You do need to regenerate the deployed code for an enterprise bean in the following situations:
21. Choices A and C are correct.If you want to export and later import enterprise beans that exist in an inheritance or association relationship, you must export the project containing the beans into a repository (.dat) file to preserve the information that defines the inheritance or association. When you later import from the .dat file, the inheritance and association information is preserved. Inheritance and association information is not preserved if you import the enterprise beans in an EJB JAR file. 22. Choice C is correct. The Application Assembly Tool allows creating, viewing, and editing the content and assembly properties of Web modules, EJB modules, application client modules, and J2EE applications. It has property dialog boxes for creating new objects and for accessing and modifying properties for a module. The tool uses the property values to automatically generate deployment descriptor files for the module. There are also wizards provided for quickly creating modules. Wizards gather minimum requirements for creating the module and generating the deployment descriptor. Also the Application Assembly Tool checks that an archive is complete, and that deployment descriptor properties and references contain appropriate values. C is done by the ResourceAnalyzer tool. 23. Choice B is correct. Hot deployment is the process of adding new components (such as enterprise beans, servlets, and JSP files) to a running server without having to stop the application server process and start it again. Dyamic reloading is the ability to change an existing component without needing to restart the server in order for the change to take effect. Dynamic reloading involves changes to the implementation of a component of an application, such as changing the implementation of a servlet, changes to the settings of the application, such as changing the deployment descriptor for a Web module. Because adding a new module requires a change to server-cfg.xml, the server must be restarted to pick up the change. 24. Choice C is correct. WebSphere supports 3 methods for mapping CMP EJBs to a database. In the Top-down approach , the information in the EJB is used to create a database table that corresponds to the managed fields of the CMP EJB. In the Meet-in-the-middle approach , there is a pre-specified correspondence between the managed fields in the CMP EJB and the columns in one or more database tables.In the bottom-up approach,EJB fields are created for columns in the database table. By default , WebSphere chooses the Top-down approach. While generating deployment code using the Application Assembly Tool, the type of mapping chosen is displayed on the console. 25. Choice C is correct. SEAppInstall is a tool for installing an application into a server configuration file and preparing this application to run within an application server. The application installer accomplishes the following: Locates and resolves bindings for each module in the EAR file Updates the server configuration file to reflect that the application is installed Puts the .ear file and its contents into the required arrangement in the directories under WebSphere Application Server Validates the configuration information in an EAR file and optionally, in the WebSphere Application Server. The -install option of the SEAppInstall command takes an EAR file, or expanded directory containing the EAR file contents and configures this file within a server configuration file specified via the optional -configFile parameter. The -validation option of SEAppInstall validates the bindings and extensions in an enterprise application (EAR) even if the EAR is not already installed. 26. Choice A is correct. When you change the URL pattern field and save the changes , the file getting changed is web.xml WebSphere Application Server 4.0 supports dynamic reloading of web.xml, so the changes are reflected. When the ContextRoot field is modified , the file getting changed is application.xml WAS 4.0 does not support dynamic reloading of application.xml For the changes to take effect, you have 2 options: Stop & Start WAS or Run the DrAdmin utility to retstart the application. The module visibility parameter is a property of the Application Server itself. Since it is recorded in server-cfg.xml, we need to stop and restart the server for the changes to take effect. Since adding a new EJB module requires a change to server-cfg.xml, the server must be restarted to pick up the change. 27. Choice A, B and E are correct. EJB query language is recommended for implementing custom finder helpers, but the use of SQL is still supported. To implement custom finder helpers, you should use a deployment descriptor extension document rather than a helper finder interface. The use of helper finder interfaces has been deprecated but is still supported to some extent. If you are working with existing EJB 1.0 JAR files, you can continue to define SQL query strings or method declarations in the helper finder interface. The EJB query language defines finder methods for entity beans with container-managed persistence. The definition uses a language based on SQL that allows searches on the persistent attributes of an Enterprise Java Bean and associated bean attributes. The query language is independent of the bean's mapping to a relational datastore and is portable. The query language is compiled into SQL at deployment time based on the schema mapping for the bean. 28. Choices A, B and C are correct. The classloader isolation mode to use for the application server. By changing the default visibility level, it is possible to have visibility of classes in other modules, or even other applications. Set the mode to "SERVER" to allow all application classloaders on the system to have visibility of all other application classloaders in the system. Set the mode to "APPLICATION" to allow all classloaders in a J2EE application to have visibility of other classloaders in the same application. Set the mode to "MODULE" to use one classloader per module. Each module (EAR, JAR, or WAR) has its own unique classloader. Set the mode to "COMPATIBILITY" for compatibility with applications from WebSphere Application Server 3.5.x and 3.0.2.x. 29. Choices A and C are correct. You have to pass parameters to the launchClient command. You can pass parameters to your client application program as well. The launchClient command allows you to do both. The launchClient command requires that the first parameter is either an Ear file specifying the client application to launch or a request for launchClient usage information.All other parameters intended for the launchClient command must begin with the -CC prefix. Parameters that are not Ear files, or usage requests, or that begin with the -CC prefix, are ignored by the application client runtime, and are passed directly to the client application program. 30. Choices D and E are correct. 'Allow OverFlow' is a propery of the Session Manager of the WebSphere Application Server. It specifies whether to allow the number of sessions in memory to exceed the value specified by Max In Memory Session Count property. 'Installed Web Modules' is a property of the Web Container. It specifies the Web modules that are installed into the Web container of this server. The remaining answers are properties of the EJB container itself. 'Application Server' is the application server of which the EJB container is a part. 'Default Data Source' is the data source used to connect to a JDBC-compliant data source like DB2. 'Passivation directory' is the directory into which the container will save the persistent state of passivated session beans. Questions and answers provided by Whizlabs Software. To order the full version of this exam simulation, click here. More Pop Quiz: |
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