Tuesday Mar 19, 2013

ADF Mobile and SDO: making the connection

One of the great difficulties in building a mobile application is building a strong web service back-end. If you are using ADF BC as your data access layer, service-enabled application modules are a compelling option. My good friend Frank Nimphius published an article in Oracle Magazine on that very topic, titled Consume Early; Consume Often

In the perspective of an ADF Mobile application, the web service methods exposed by the SDO interfaces of ADF BC view objects are accessed through the web service data control. It is worth remembering that, at this point, SDO interfaces can be reached through the SOAP protocol only. Support for REST interactions is currently planned for ADF 12c. Fortunately, the WSDL description for the service is generated by JDeveloper.

It is possible to bind directly your AMX pages to the web service data control. Shay Shmeltzer has posted a few blog entries where he uses this technique, even for calling web services with complex parameters. Some use cases, however, can be implemented more cleanly by calling the web service data control in Java code, which implies the page is bound to a bean or to a POJO-based data control. But how does one invoke the web service data control from code?

The first step is to look at the structure for the data control. Suppose I want to call the createVisit method exposed by the VisitsWS data control. The method accepts a single input parameter of type java.lang.Object

Calling the method with any random object will not work. The data control expects an object of a very specific type, with attributes matching its own definition. It is possible to determine the name of the type expected by the data control by hovering above the parameter with the mouse pointer, as shown in the screenshot below.

VisitsWS.Types.createVisit.visit is not implemented through a Java class; it is a virtual type managed by the data control. In ADF Mobile, the web service data control, when operating over the SOAP protocol, requires parameters to be passed as instances of the oracle.adfmf.util.GenericType interface. The only way to instantiate such objects is to use the GenericTypeBeanSerializationHelper class provided by the framework.  This class will transform POJO instances to and from GenericType.

Below is a  code sample that shows how to build the GenericType and  invoke the web service through the data control.

Visit visit = new Visit();

// Set attribute values for visit here.

List namesList = new ArrayList(1);
List paramsList = new ArrayList(1);
List typesList = new ArrayList(1);

GenericType gtVisit = GenericTypeBeanSerializationHelper.toGenericType("VisitsWS.Types.createVisit.visit", visit);

namesList.add("visit");
paramsList.add(gtVisit);
typesList.add(Object.class);

try {
    AdfmfJavaUtilities.invokeDataControlMethod("VisitsWS", null, "createVisit", namesList, paramsList, typesList);
} catch (AdfInvocationException ex) {
    // If the web service is not available throw a nice exception
    if (AdfInvocationException.CATEGORY_WEBSERVICE.compareTo(ex.getErrorCategory()) == 0) {
        throw new RuntimeException("Error with the server. Please try later.");
    }
}

There are a few things you should take into account when creating your POJO objects.

  • The attributes must have the same name as the data control attribute they are mapped to. 
  • The attributes must preferably be of type java.lang.String. Other types may work, but you may run into problems.
  • When manipulating dates, it is essential to express them in the ISO-8601 format expected by the SOAP service layer. This can be achieved through the oracle.adfmf.misc.ISO8601DateTimeUtil class.
  • If the service you invoke is based on a view object that contains attributes retrieved through a join that are marked as a reference, your POJO must declare these attributes as transient. This way, no values will be transmitted back to the server in the case of create and update operations. Failing to do so will raise a JBO exception on the server.  

By the way, if you found this post interesting, one of the two presentations I will make at the ODTUG Kaleidoscope 2013 conference in June will show you how to build flexible and SOA-compliant back-ends using Oracle ADF. See you in New Orleans! 

Monday Feb 25, 2013

ADF Mobile on BlackBerry 10: a failed but instructive experiment

With the release of their new handsets and operating system, Blackberry occupied lots of media space recently. This prompted me to have a deeper look at their platform and to experiment a bit in relation to ADF Mobile. You shouldn't read anything in this, by the way; my personal curiosity doesn't foreshadow Oracle's strategy. 

The BlackBerry 10 OS, as you may know, is able to run most Android applications through a runtime which supports about 70% of Android's APIs. Just for the sake of it, I tried to repackage a very simple ADF Mobile application and deploy it on the BlackBerry 10 simulator. Deployment was successful, and I was even able to get past the splash screen. It is only then that the application failed with an error message stating « Network_ERR: XMLHttpRequest Exception 101 ». This application is self-contained and didn't call any web services, by the way. The root cause of the error was obviously something else.

To be truthful, I expected the experiment to fail. The Android toolkit provided by BlackBerry contains an executable that scans APKs (packaged Android applications) for compatibility. When I ran it on my ADF Mobile APK, it flagged various minor problems (since we are using various hardware features) as well as a major issue: the presence of native code. You can see the full output below:

Apk2Bar /Verifier version 1.5.1
Research In Motion Ltd ? 2012 All rights reserved.
[osname.apk]:(res/drawable-xhdpi/adfmf_icon.png) found an alternate icon with better size:impact=1
[osname.apk]:(AndroidManifest.xml) uses-feature: android.hardware.camera:required minimal Tablet OS version=2.1:impact=2
[osname.apk]:(AndroidManifest.xml) uses-feature: android.hardware.telephony:required minimal Tablet OS version=10.0.6:impact=2
[osname.apk]:(AndroidManifest.xml) uses-feature: android.hardware.camera.autofocus:required minimal Tablet OS version=10.0.9:impact=2
[osname.apk]:(AndroidManifest.xml) native-code: armeabi:impact=5
[osname.apk]:(com/phonegap/AudioHandler.java:275) uses method: android.media.AudioManager$setRouting:impact=1
[osname.apk]:(com/phonegap/AudioHandler.java:272) uses method: android.media.AudioManager$setRouting:impact=1
[osname.apk]:(com/phonegap/AudioPlayer.java:193) uses method: android.media.MediaPlayer$setAudioStreamType:impact=1
[osname.apk]:Summary: [5]=1; [4]=0; [3]=0; [2]=3; [1]=4;
Summary: [5]=1; [4]=0; [3]=0; [2]=3; [1]=4;
Impact Legend: [5]=Severe; [4]=High /context; [3]=Medium /context; [2]=Medium-low /context; [1]=Minor;

The offending native code is part of the JVM that we package with the application itself. Therefore, there is nothing we can do to circumvent the issue right now. Further releases of ADF Mobile could replace the current JVM, thus creating more favorable conditions for this to work.

I must say I was impressed by the developer tools provided by BlackBerry (formerly Research in Motion), especially the device simulator. Its boot time is an order of magnitude shorter than the Android Emulator's, and it was a joy to use.

Does your organization plans to get BlackBerry 10 devices? Is this new platform a more interesting target than Windows Phone? Let us know!   

 

Wednesday Feb 13, 2013

Evaluating EL expressions the Java way in ADF Mobile

Expression language (EL) is used all over the place in JSF and ADF Faces, since it enables the presentation layer (JSPX / JSF pages) to communicate with the application logic (managed beans). ADF Mobile uses exactly the same pattern with its AMX technology, which delivers a JSF-like development experience to build an HTML5-based user interface. The key point here is JSF-like, since internal implementation details may vary between the two.

It is sometimes useful to evaluate EL expressions in the managed bean itself rather than delegate the task to the page. Typically, in ADF web applications, this is done like this:

import javax.el.ELContext;
import javax.el.ExpressionFactory;
import javax.el.ValueExpression;
import javax.faces.application.Application;
import javax.faces.context.FacesContext;


public static Object resolveExpression(String expression) {
    FacesContext facesContext = getFacesContext();
    Application app = facesContext.getApplication();
    ExpressionFactory elFactory = app.getExpressionFactory();
    ELContext elContext = facesContext.getELContext();
    ValueExpression valueExp = 
        elFactory.createValueExpression(elContext, expression,
                                        Object.class);
    return valueExp.getValue(elContext);
}

This code snippet will not work as is in ADF Mobile, since there are no FacesContext or Application objects.

Sure, you could retrieve the expression factory by doing this:

import oracle.adfmf.framework.api.AdfmfJavaUtilities;
import oracle.adfmf.framework.model.AdfELContext;

AdfELContext ctx = AdfmfJavaUtilities.getAdfELContext();
ExpressionFactory factory = ctx.getExpressionFactory();

But ADF Mobile provides helper methods that will retrieve the context and expression factory behind the scenes for you.  For example, if you want to evaluate in Java an EL expression that retrieves a message (key ERROR_MSG) from a ressource bundle (declared as viewcontrollerBundle):

import oracle.adfmf.framework.api.Model
import oracle.adfmf.framework.contract.adf.NameValuePair;
...
Model mod = new Model();
NameValuePair[] result = null;

result = mod.getValue(new String[] { "#{viewcontrollerBundle.ERROR_MSG}" });
String value = (String)(result[0].getValue());

The code above will work out of the box if the AMX pages referencing the bean declare the bundle. If that's not the case, you must simply add this line of code before calling getValue on the Model object:

mod.loadBundle(<resource_bundle_basename>, <var_attribute>);

How would you use this technique in a real-world scenario? Suppose, for example, that you need to bind a single amx:outputText to several different values in a resource bundle, the specific text string to be displayed being determined at runtime. In ADF web applications, you could use nested EL to achieve your goal:

#{viewcontrollerBundle[<EL_expression_for_bundle_key>]}

This doesn't work in ADF Mobile currently. Thus, you can sidestep the issue by creating a method binding on a bean and reference it in the page. 

Monday Feb 04, 2013

ADF Mobile: Checking the operating system's name

Recently, somebody asked on the OTN forums how to check the name of the operating system from an ADF Mobile application. This is useful in order to provide a user experience better tailored to a specific mobile platform, for example. 

The first idea I had was to query the JVM's built-in properties: 


System.getProperty("os.name")

This, however, returns Linux on an Android device. This is not surprising, as Google's mobile OS uses the Linux kernel as its foundation. On the other hand, this answer lacks specificity. How can we get a better one?

Turns out  the most reliable way to achieve this task is to use the DeviceManager interface, which supports the DeviceFeatures data control. 


DeviceManager device = DeviceManagerFactory.getDeviceManager();
String os = device.getOs();

The code sample above will return Android as expected on my device.

ADF Mobile and resource bundles

In my last post, I described the three bundle types available to ADF Developers. Last week, I learned that the ADF Mobile framework doesn't support all the choices offered by its server-side older brother. Only XLIFF bundles are available in the current version. You can read more about this here.

Sunday Jan 20, 2013

Internationalization: which bundle type is right for you?

Choice is one of the fundamental tenets of JDeveloper's approach to development. This probably explains why so many people on the OTN forums and the ADF Enterprise Methodology Group ask for guidance on picking the best alternative to handle specific use cases. Most of the time, the answer will start with: Well... It depends. Developer skills, functional requirements, performance expectations and other variables make it difficult to come up with a single, straightforward recommendation. This is the case with resource bundles. 

In the context of the Java platform, a resource bundle is simply a collection of objects related to a specific locale. Each object can be retrieved by its key, which must be unique among all the bundles available to an application. When a program needs a locale-specific resource, such as the string for an error message, it can load it from the resource bundle that is appropriate for the current user's locale. This mechanism allows you to write programs that can:

  • be easily localized, or translated, into different languages
  • handle multiple locales at once
  • be easily modified later to support even more locales
    Source: Javadoc for the ResourceBundle class. 

JDeveloper supports three different types of resource bundles: Java classes, .properties files and XLIFF files. All three behave exactly in the same way at runtime; choosing one type or the other will be completely transparent to the end user and will not likely impact performance or resource usage in a well-designed application. Why would you pick one type over the other, then?

[Read More]

Thursday Jan 03, 2013

The slow JDeveloper startup mystery

I am currently producing my first ADF Insider session. It contains a few recorded demonstrations, which I did using an Oracle Enterprise Linux 6.3 virtual machine. I was pleased by the performance and polish of the OS, and recording was a breeze. If only JDeveloper hadn't been so slow to start...

Now, some of you will probably tell me this is business as usual. This is unfair. Since the first 11g release in 2007, JDeveloper's performance has improved steadily. Bex Huff also gave very effective advice on his blog on how to tune your JVM options to improve the tool's speed. And the improvements brought in the 11.1.2 branch show we can expect even more performance for 12c.

What I saw in my VM was beyond what I had seen before, anyway. The splash screen was being displayed for nearly a minute before the progress bar showed... And no update centers were available when I checked for updates, preventing me from downloading any. Clearly, something was amiss. With 8gb allocated to it and two virtual CPU cores, resources weren't the problem. After searching on the web for a few minutes and coming back empty-handed, I decided to start JDeveloper on the command line.

[Read More]

Friday Dec 21, 2012

The great Windows 8 experiment

Two weeks ago, I decided to make the plunge: I upgraded my personal workstation to Windows 8. Why? Sure, I wanted to check if JDeveloper and WebLogic worked correctly. But I must admit my main motivation was curiosity. You see, when I read quotes such as: « On a regular PC, Windows 8 is Mr. Hyde: a monster that terrorizes poor office workers and strangles their productivity. », it was hard to resist the temptation of forging my own opinion. 

Today, I am writing this post under Windows 8. And I have no intention to go back to Windows 7.

I have very little to report about Oracle's Java tools. They simply just work, as I expected. The JVM  abstracts the underlying OS as on any other platform. I only had two small glitches up to now.

[Read More]

Friday Dec 14, 2012

Saddling your mountain lion with JDeveloper

Last October, Apple released Java Update 2012-006. This patch brought the Apple-provided JDK for OS X Lion v10.7 and OS X Mountain Lion v10.8 to version 1.6.0_37. At the same time, it disabled the Apple Java plugins and removed the Java Preferences panel that enabled users to manage the various Java releases on their computer.

On the Windows and Linux platforms, JDeveloper 11g R1 has been certified  to run on Java 7 since patch set 5. This is not the case on OS X.  

( The above is not a typo. Apple's OS for personal computer is now known as OS X; the « Mac » prefix has been dropped with the 10.8 release. And it's pronounced « Oh-Ess-Ten », by the way. )

Please note JDeveloper 11g R2 is not certified either. On any platform. It will generally work, but there are known issues with ADF Mobile. Personally, I would recommend to wait for 12c before going to JDK 7. 

Now, suppose you have installed Oracle's JDK 7 on your Mac. JDeveloper will not run on it. It will even not install. Susan and I discovered this the hard way while setting up the ADF Mobile hands-on lab we ran at the UKOUG 2012 conference. The lab was a great success nevertheless, attracting nearly a hundred delegates. It was great to see the interest ADF Mobile already generates, especially among PL/SQL Developers and DBAs. But what did we do to make it work? 

[Read More]

Thursday Dec 13, 2012

How to force ADF to speak your language (or any common language) in the logs

When I started working for Oracle, one of the first tasks I was given was to contribute some content to a great ADF course Frank and Chris are building. Among other things, they asked me to work on a module about Internationalization. While doing research work, I unearthed a little gem I had overlooked all those years. 

JDeveloper, as you may know, speaks your language - as long as your language is English, that is. Oracle ADF, on the other hand, is a citizen of the world. It is available in more than 25 different languages. But while this is a wonderful feature for end users, it is rather cumbersome for developers. Why is that? Have you ever tried to search the OTN forums for a solution with a non-English error message as your query? I have, once. But how can you force ADF to use English for its logging operations? 
[Read More]

Wednesday Dec 12, 2012

I owe you an explanation

Welcome to my blog!

I am Frédéric Desbiens, a new member of the ADF Product Management team.  I joined Oracle only a few weeks ago. My boss is Grant Ronald, and I have the privilege to work in the same team as Susan Duncan, Frank Nimphius, Lynn Munsinger and Chris Muir. I share with them a passion for all things Java and ADF. With this blog, I hope to help you be more successful with our products – whether you are a customer or a partner.  

[Read More]
About

Frédéric Desbiens

The musings of a member of the ADF Product Management team.

I focus here on my favorite development framework but also have a strong interest in Mobile Development, Oracle WebCenter and Oracle SOA Suite.

Attentive readers will even find posts about IT Strategy from time to time, an interest of mine since I completed my MBA in 2006.

The views expressed on this blog are my own and do not necessarily reflect the views of Oracle.

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