Oracle application-development-framework-best-practices

ADF Best Practices (Collated from various sources)

Table of Contents 1. Overview 2. Entity Objects 3. View Objects 4. Application Module 5. Other General ADF Business Components Best Practices 6. Pages 7. Java Script 8. Bindings 9. TaskFlows 10. Beans 11. Other General Java Best Practices 12. Web.xml 13. Weblogic.xml 14. Deployments 15. References

Overview Oracle Application Development Framework (Oracle ADF) is an innovative, yet mature Java EE development framework available from Oracle and directly supported and enabled by the award winning development environment, Oracle JDeveloper 11g. Oracle ADF is based on the Model-View-Controller (MVC) design pattern. An MVC application is separated into: 1) a model layer that handles interaction with data-sources and runs the business logic. 2) a view layer that handles the application user interface, and 3) a controller that manages the application flow and acts as the interface between the Model and the View layers. Oracle ADF implements MVC and further separates the model layer from the business services to enable service-oriented development of applications. The Oracle ADF architecture is based on four layers: 1) The Business Services layer - provides access to data from various sources and handles business logic (ADF Business Components, EJB, BPEL) 2) The Model layer - provides an abstraction layer on top of the Business Services layer, enabling the View and Controller layers to work with different implementations of Business Services in a consistent way (ADF Binding) 3) The Controller layer - provides a mechanism to control the flow of the Web application (JSF/ADF Controller) 4) The View layer - provides the user interface of the application (JSF, AF Faces, ADF Swing) The picture in the next slide gives a pictorial representation of the 4 different layers in ADF.

This document encompasses some of the best practices that must be followed when designing and building an ADF application. The document talks about these best practices in the following sequence 1. Entity Object 2. View Object 3. Application Module 4. Other General ADF BC Best Practices 5. Pages 6. JavaScript 7. Bindings 8. Taskflows 9. Beans 10. Other General Java Best Practices

11. web.xml 12. weblogic.xml 13. Deployment Entity Objects  Define at least one entity object key attribute per entity object - An entity object must has at least one attribute defined as the key.  Do not access an application module from an entity object - entity objects should not access application modules as this makes the entity object only useable within that application module.  Don't use ROWID as entity object key - By default if ADF BC doesn't find a primary key at design time for an entity object's related database table, it will generate an additional attribute mapping to ROWID. This will continue to work unless an Oracle database Real Application Cluster(RAC) is used where across database partitions different ROWIDs can be returned for the same row.  Define entity object attribute labels for UI displayed attributes - For all entity object attributes that are displayed in the UI set their default label.  Ensure entity object UI Hints and messages are internationalized – Assuming that the application will be translated all entity object field labels and other relevant UI hints and messages need to be managed via message bundles.  Use entity object attribute change indicators where appropriate - When creating an entity object that includes a column that indicates when the row was created and updated, set the change indicator property for that attribute. This provides a performance improvement when updating or deleting the record to the database as ADF BC only needs to check the attribute as marked with the change indicator rather than all attributes of the entity.  Define entity object attribute tooltips for UI displayed attributes where an explanation of the allowable values is required - For all entity object attributes that are displayed in the UI, where the attribute has a set of allowable value that isn't obvious, include a one sentence tooltip to describe this.  Use entity object history columns where appropriate - When creating an entity object based on a table with columns such as created_by, created_date, updated_by and updated_date, set the relating attribute history column properties.  Create error messages for entity object mandatory and precision validators – The default error messages for the pre-generated mandatory and precision validators can be overridden with clearer messages.

 Avoid using the entity object validateEntity() method for validation - do not override an entity object's EntityImpl validateEntity() method. Rather code any business logic as a  declarative method validator for the entity object itself. This comes with the added advantage all validations are visible in the entity object's business rules page.  Avoid entity object attribute validation in accessors - do not write code to validate an attribute in its setter accessor within the associated EntityImpl class for the entity object. Rather create a declarative method validator for the attribute.  Do not call postChanges unless you can guarantee a commit or rollback at the end the HTTP request – Typically the EntityImpl postChanges method is called by the ADF BC lifecycle upon a commit operation. However you can also programmatically call this method. As the postChanges method changes the state of the associated EntityImpl which then assumes the changes have been committed to the database, this can leave your entity object in a dirty state. As such only call the postChanges method directly if you know that at the end of the HTTP request you will commit or rollback the transaction. View Objects  Never use view object select * - Never use SELECT * for a view object query. Always specify all columns in the query.  Avoid hardcoding view object queries with literals - Don't hardcode view object where clauses or view criteria with literals. Always use bind variables.  Use view object bind variables over dynamic SQL - Bind variables also make the queries of view objects less susceptible to SQL injection attacks.  Don't define circular list of value dependencies - View objects allow you to define dependent/chained list of values. Be careful not to define a circular dependency as this can result in an infinite loop.  Ensure view object UI Hints and messages internationalized - Assuming that the application will be translated all view object field labels and other relevant UI hints and messages need to be managed via message bundles.  Avoid unnecessary view object duplication - In many cases very similar view object instances can be created from the same base definition with the correct use of applied view criteria when the instance is exposed via the application module.  View objects should include all key attributes from underlying entity objects – If a view object is based on one or more entity objects, then view object should include all the key attributes from each entity object.

 Define at least one view object key attribute - A view object must has at least one attribute defined as the key. This is particularly important for view objects that are marked for passivation as the key is required to restore the current row on activation.  Rarely use view object expert mode - Rarely use expert mode for view objects. If the query you wish to execute can be implemented by modifying other properties of the view object over expert mode this should be your preference. For example SQL functions on attributes can be applied at the attribute level.  Use declarative SQL view objects where possible - Declarative SQL based view objects selectively prune the attributes included in the underlying query based on the attributes accessed via the binding and UI layers. This results in faster turn around with the database and less middle tier memory consumed.  Avoid read only view objects for speed benefits alone - Older ADF manuals recommended using read only view objects as there was a minor speed benefit. Since JDeveloper 11g this is no longer true as the caching mechanism has been improved. Today read only view objects should be reserved for complex queries such as those with set operations (e.g. UNION, MINUS, INTERSECT) and connect by queries. All other view objects should be based on entity objects. If the view object needs to be read only, unselect the "Updateable" property when the entity object is mapped to view objects.  Avoid case insensitive view criteria if not needed - For view objects using view criteria, ensure to uncheck the case insensitive option if it not needed as it will make database queries slower unless an Oracle RDBMS function based index is available.  Ensure to use view object accessor tuning - ensure to set the view object exposed through the view accessor tuning options appropriate to how the view object will be used.  Use type-safe view object getter/setter accessors - If accessing any attribute for the view object, always use the type-safe getter and setter methods provided by the ViewRowImpl over the generic getAttribute and setAttribute methods.  Use type-safe bind variable getter/setter accessors - If accessing bind variable for the view object, always use the type-safe getter and setter methods provided by the ViewObjectImpl over the generic getAttribute and setAttribute methods.  Check view object SQL performance - Ensure to check the performance in the database of the underlying view object queries, especially critical for search forms. If need be seek guidance from your DBA on creating the appropriate database indexes for the search criteria.  Consider view object fetch size and access mode - Consider the view object tuning options for how the view object will be used. If the view object is used to display a page of 10 records for example, set the Batch/Fetch size of the view object to 10 + 1 too.

 Use createRowSetIterator() for view object programmatic iteration - if in code you need to programmatically iterate over the rows provided by a view object, use the createRowSetIterator() and closeRowSetIterator() methods to manage a separate RowSetIterator to the default provided by the view object, as the default may be bound to the user interface  Use view criteria over editing view object where clauses - Rather than customizing a view objects where clause which makes the use of the view object less flexible, use a viewcriteria instead. Application Module  Use optimistic locking - Only use optimistic locking (the default) for web applications, rely on the global setting in the adf-config.xml file to set this.  Use application module JDBC data source only - Only use JDBC data sources for application module configurations, do not use JDBC URLs.  Close callableStatement and preparedStatements - Via the  ApplicationModuleImpl you can retrieve a DBTransactionImpl to call createCallableStatement or createPreparedStatements. These both return JDBC objects which require you to close the statements once complete. This requires a try/catch/final block to ensure the JDBC connection is closed at the end of its use.  Carefully consider using transactions within overridden ADF BC code – Besides custom methods, generally speaking ADF BC manages user transactions on the developers behalf. Any usage of get(DB)Transaction() .commit() or rollback() should be considered very carefully based on the possible side effects it may have to open transactions within the AM scope.  Use view object typesafe getters - By default the AppModuleImpl contains getter methods to return the associated data model view objects exposed through the application module editor. Ensure for the relating view objects that you've first generated the associated ViewObjectImpl class and that the getter method in the AppModuleImpl returns the typesafe class (e.g CustomerViewImpl) rather than the parent ViewObjectImpl.  Extend custom exceptions with JboException or subclasses – Generally speaking custom Java exceptions in code should be avoided and applications should rely on declarative validation instead. However if an application does write any programmatic exceptions all custom exceptions written in the ADF BC model layer should extend JboException or a valid subclass such as AttrValException that when raised the error is handled gracefully by the UI layer.  Do not import view or controller classes - The model project should not import or use classes from the view or controller layers such as oracle.adf.controller, oracle.adf.view or org.apache.myfaces.trinidad otherwise they are in violation of the MVC pattern.

 Don't hardcode human readable text - Do not hardcode human readable text in your ADF Business Component Java code. Rather store any hardcoded text in a resource bundle and refer to the key value-pair instead.  Don't introduce HTTP session dependencies into ADF BC, rely of ADFContext where possible - ADF BC code should maintain separation and not assume that it is being  called from within the context of an ADF Web Application. The HTTP session and other UI layer states should not be accessed directly if you need to use the ADFContext object to access these instead. Other General ADF Dusiness Components Best Practices  Define a jbo.debugoutput run option - Within the ADF Business Component model project properties define a new Run/Debug/Profile option entitled JboDebugOutputConsole where the Launch Setting → Java options is set to -Djbo.debugoutput =console. Only use this setting for none production systems, it is not supported in production ADF applications.  Ensure jbo.debugoutput disabled for production - Ensure the Java command line - Djbo.debugoutput=console option is not enabled for production ADF systems. Pages  Use JSPX rather than JSP for 11gR1 applications - If using a JDeveloper 11gR1 release (which doesn’t use Facelets), use JSPX XML compliant files rather than JSP.  Don't hardcode human readable text - Do not hardcode human readable text in your pages/fragments. Rather store any hardcoded text in a resource bundle and refer to the key- value pair instead.  Avoid inline HTML use - Embedded HTML in JSF pages is often responsible for breaking the behavior of the ADF Faces Layout components. Additionally HTML embedded in a JSF page assumes that the page is indeed being rendered in a conventional browser and may link the application to a particular subset of browsers.  Consider command partialSubmit=true - Command components such as af:commandButton by default when pressed cause a complete page refresh with the server. If not navigating between pages, consider using partialSubmit=true which will result in only components with their partialTriggers set to be processed.  Avoid long component ID lengths - Avoid long component ID names as this has a performance hit.  Use rendered=false over visible=false if possible - If you wish to hide a component use rendered=false over visible=false when possible as the first results in the server skipping the

processing of the component and sending it over the wire to the browser, while the 2nd requires the server to process the component, send it over the wire, the browser to process it then hide it.  Consider that visible=false presents a security risk for components – As components with visible=false are still sent to the client then hidden, it's easy for hackers to see them in the browser DOM, manipulate them and if they're submittable components send them on the next request. Instead either use rendered=false so the component isn't sent to the browser in the first place, or back the submittable component by a validation rule to ensure it can't be submitted when the component is meant to be hidden.  Never rely on UI side validation - Never solely rely on UI (browser) validation alone as this can be easily exploited by hackers. As example a selectOneChoice on the browser provides an allowable list of values the user can select from, but doesn't validate that the user hasn't submitted a different value not in the list. Always back UI side validation up with server side validation to catch such workarounds.  Avoid hardcoding EL literals - Avoid hardcoding literals in EL expressions. Instead place the hardcoding in a managed bean and refer to it through a boolean accessor instead. For example the EL expression #{bindings.Status.inputValue == 'Updateable'} could be replaced with #{editBookings.updateable}.  Avoid repeating EL conditions - If there is a common EL condition used through out a page consider placing the logic in a bean boolean accessor instead.  Restrict the use of EL evaluation in code - Evaluating expression language within (and only within) Java Code can be error prone and requires a context switch which is inherently slow. It is preferable to inject EL values as managed properties to a bean and therefore allow the design time to validate the reference, or if the values must be determined at the point the code is evaluated, access the values via Java context objects or other Java constructs.  Do not prefix EL references to managed beans in request, session or application scope with the *Scope prefix - Although it seems to be a good thing to be explicit about the scope that you expect such an object to be in, doing so will bypass the JSF creation routines if the bean does not already exist. This is not an issue for the ADF specific scopes. JavaScript  Component ID Lookup using AdfPage.PAGE.findComponentByAbsoluteId() -  Component lookup in this way, with the complete and absolute ID of the component in question is the most reliable.

 JavaScript strings invoked from the ExtendedRenderKitService should be minimal - This ensures that the packets sizes for roundtrips are kept to a minimum and also ensures that the code that is invoked in this way is subject to the same scrutiny as other JavaScript used by the system.  Avoid inline page/fragment JavaScript and CSS - Avoid placing custom JavaScript and CSS in your page and page fragments as these must be loaded by the browser each time the page/fragment is accessed. Instead place the JavaScript and CSS respectively in separate .JS and .CSS files so they can be cached by the browser.  Avoid inlineStyle and contentStyle CSS added to a page - CSS added directly in a page is not compressed, it makes the page harder to manage and maintain, and increases the page download size. Use inlineStyle and contentStyle properties for dynamic color coding only and have the properties referencing a managed bean property to return the CSS string  Do not use percentage height styles - Heights expressed as a percentage are not reliable and behavior differs between browsers. Use absolute values for height if height must be specified at all Bindings  Only interact with the business model through the binding layer - Accessing the underlying business model (e.g. an application module) via the dataprovider can have multiple negative effects such as causing memory and connection leaks, getting the wrong sessions data and breaking the auto PPR functionality.  Don’t reference #{data} - The #{data} expression root is not guaranteed to provide access to the required data. Success will depend on the state of the cache. If data is needed in a particular view / method then create an explicit binding in that scope. TaskFlows  Define a common task flow template - All bounded task flows can be designed to inherit from a single task flow template that can be used to provide common functionality like exception handling and logging.  Use required parameters - Use the required attribute for any parameter to ensure that the design time and runtime environments can identify that a particular parameter is optional or required.  Avoid multiple task flow definitions in one task flow file - for each task flow XML metadata file restrict the file to one task flow definition.

 Unbounded task flow should only be used for entry points - Any view exposed through the adfc- config unbounded Task Flow is accessible via the URL and open to user manipulation. As such the actual pages exposed in this way should be restricted.  Use bound methods on task flows rather than invokeAction executables in the pageDef - Although the use of invokeAction is allowed it is generally much clearer to use a method activity in a page flow to explicitly show when code is executed before a page or fragment is displayed. Also the invokeAction mechanism has no way to cleanly execute associated code once before the page renders, using the method activity provides you with the cleanest interface for implementing this logic. Beans  Limit custom code in bean accessors - As the JSF lifecycle may call the getter and setter method in your beans multiple times, keep the code as small as possible to avoid unnecessary processing.  Use beans only defined in the task flow for reuse - To make them reusable, taskflows should not reference managed beans that weren't defined within the task flow.  Avoid applicationScope and sessionScope variables - Use applicationScope and sessionScope variables with care as they create a tight coupling and unintended dependencies within code.  Use unbounded task flow scope pageFlowScope variables over sessionScope to support multi browser tabs - ADF supports users opening multiple browser tabs onto your application. From the user's perspective these are two separate connections to the application, and as such the state for each should be separate. Variables stored in sessionScope will be shared across both browser tabs as only one instance of the sessionScope bean will be instantiated. Alternatively for pageFlowScope beans one is instantiated per browser tab.  Define applicationScope and sessionScope beans in adfc-config.xml - applicationScope and sessionScope managed beans should be defined in the adfc-config.xml file.  Define unbounded task flow beans in adfc-config.xml - For any page or page fragment used by an application's unbounded task flow, any relating bean used by the page should also be defined in the adfc-config.xml.

 Define bounded task flow bean in their own .xml file - For any page or page fragment used by a bounded task flow, any relating managed bean used by the page should also be defined in the bounded task flow's .xml file.  Avoid business logic in bean methods - complex business logic that manipulates model layer data should not be placed in the ViewController layer. Consider placing such code in the model layer instead and making one programmatic call from the bean.  Variables in applicationScope and sessionScope beans - Be mindful of the variables you store in applicationScope and sessionScope as they may be stored there for longer than necessary.  Define all managed beans explicitly in XML rather than through a mix of XML and annotations - As of JSF2 we can use annotations in code to define classes as managed beans in the standard JSF scopes. However, such annotations do not exist for the ADF specific scopes and mixing both techniques may make it harder to track down the definition when maintaining the code.  Only create backing beans when actually needed, do not bind unnecessary component references into backing beans - You only need a Backing Bean when you actually need somewhere to hold event handler code. If you have no such code requirements, don’t bother to create the bean.  Utilize common utility class or Backing Bean superclass for common functions - Utility Methods are often reused within multiple backing beans and a common provider class can save a lot of time and coding mistakes Other General Java Best Practices  Don't use internal ADF packages - Do not use any of the following ADF packages within your Java code as Oracle does not guarantee to change the implementation in the future  Don't use System.exit() - Executing System.exit() in a running ADF application will force the JVM container to quit. Do not use this.  Don't hardcode human readable text that will be displayed in the UI - Do not hardcode human readable text in your Java code or web pages that will be displayed to the user. Rather store any hardcoded text in a resource bundle and refer to the key value-pair instead.  Ensure catch blocks do not swallow errors - Stubbed try/catch blocks that do not re-throw or report exceptions by logging may be concealing bugs. Rather ensure all catch blocks rethrow exceptions so they percolate through the ADF controller or ADF model exception handlers.

 Include Javadoc - provide an appropriate level of documentation through out your code.  Don't use System.out.* or System.err.* - Do not use functions like System.out.println.for debugging and do not leave this unnecessarily in your code.  Use the ADFLogger- Make use of ADFLogger in your ADF applications.  Consider user level logging in production – Enterprise manager now supports user level tracing which allows you to lower the log level for a single session. Traditionally turning on logging on production systems would result in a flood of information for all sessions making the reason to write logging in the first place less than useful. However with the ability to turn logging on for a specific user this makes the implementation of logging more useful.  Consider logging granularity - Don’t write all log messages at the same logging level. Consider what information will be of use for respectively; reporting, error details, live analysis by support and specialized analysis by the development team.  Always reformat code - All code should be reformatted before check in to assist readability.  Remove commented out code - Do not leave commented out code in your source code upon check in. Web.xml  Consider setting oracle.adf.view.rich.security.FRAME_BUSTING for production – consider the web.xml oracle.adf.view.rich.security.FRAME_BUSTING context parameters options to prevent clickjacking, which occurs when a malicious web site pulls a page originating from another domain into a frame and overlays it with a counterfeit page.  Consider oracle.adf.view.rich.versionString.HIDDEN=false for production – set the web.xml oracle.adf.view.rich.versionString.HIDDEN context parameter to true to remove the ADF Faces version information on each page to reduce the size of the page and also remove an attack vector by unnecessarily publishing the version of ADF.  Deployment to Production Systems Versus Development/Testing Systems org.apache.myfaces.trinidad.CHECK_FILE_MODIFICATION=false If this parameter is true, there will be an automatic check of the modification date of your JSPs, and saved state will be discarded when JSP's change. It will also automatically check if your skinning css files have changed without you having to restart the server. This makes development easier, but adds overhead. For this reason this parameter should be set to false when your application is deployed in environments other than Development instances. Weblogic.xml

 url.rewriting.enabled should be false - If enabled, the feature would cause security vulnerability because the session identifier would be exposed in certain scenarios. Deployment  Use ojdeploy for Packaging - For applications leveraging ADF Security or MDS, this is an important step to ensure that all of the correct metadata is included in the archive.  Ensure connection information is not deployed with the application - Connections should be configured by the consumer of the application – usually though the Java EE data source mechanism.  Packaged EAR file should include information bearing Manifiest file  Use ADF Libraries appropriately for reusable components - ADF Libraries provide the best mechanism to ensure the discoverability of metadata based artifacts within a standard JAR format. References 1) Oracle ADF Technical overview: http://www.oracle.com/technetwork/developer-tools/adf/adf- 11-overview-1-129504.pdf 2) Oracle ADF Web Developer’s Guide 11.1.2.1.0 http://docs.oracle.com/cd/E24382_01/web.1112/e16181.pdf 3) Oracle ADF Fusion Developer's Guide 11.1.2.1.0 http://docs.oracle.com/cd/E29049_01/web.1112/e16182.pdf 4) ADF Code Guidelines v1.00 - 30/09/2012 http://www.oracle.com/technetwork/developer- tools/adf/learnmore/adf-code-guidelines-v1-00-1845659.pdf 5) More Details on Frame Busting http://seclab.stanford.edu/websec/framebusting/framebust.pdf 6) Oracle® Fusion Middleware Performance and Tuning Guide http://docs.oracle.com/cd/E23943_01/core.1111/e10108/adf.htm

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