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Box layout managers take the space they get from their parent layout or widget, divide it up into a number of boxes, or cells, and make each widget in the layout fill one box.

QHBoxLayout is one of the two available box layouts in PyQt. This layout manager allows you to arrange widgets horizontally, one next to the other. The widgets are added to the layout from left to right. This means that the widget that you add first in your code will be the left-most widget in the layout.

To add widgets to a QHBoxLayout object, you call .addWidget(widget, stretch, alignment) on the layout object. This method takes one required argument and two optional arguments:

Here’s a small application that shows how to create a horizontal layout using QHBoxLayout. In this example, you’ll use QPushButton objects to better visualize where each widget will be placed in the layout according to the order in which you add the widgets to your code:

On line 15, you create a QHBoxLayout object called layout. On lines 17 to 19, you add three buttons to layout using .addWidget(). Note that you pass 1 and 2 to the stretch parameter in the Center and Right-Most buttons, respectively. On line 21, you set layout as your window’s top-level layout using .setLayout().

If you run this application, then you’ll get the following window on your screen:

This window contains three buttons arranged in a horizontal fashion. Note that the Left-Most button corresponds to the first button that you add in your code. So, buttons are shown in the same order (from left to right) that you add them in your code (from top to bottom).

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One of the application programming interface (APIs) that are part of the J2EE (now JEE) enterprise application building standard from Sun Microsystems is the enterprise JavaBeans.

The EJBs are the objects that application server give to the server side.

The roles played by the EJB container and EJBs are defined by the EJB specification.

The standard server-side distributed component model is provided by EJBs. The goal of the EJBs is to give programmers a model that will allow them to abstract from the general problems of a business application. Being based on components allows them to be flexible and reuse.

JavaBeans should not be confused with enterprise java bean. JavaBeans are a component model created by Sun Microsystems for building applications, but they can't be used in distributed object environments because they don't support remote invocation.

There are three types of EJBs.

The EJBs are in an application server container. The specification describes how the EJB interacts with the container and how client code interacts with it.

Each EJB must have a Java implementation class.

The java implementation class will be instantiated by the EJB container. The EJB client code uses java interface. The home and remote interface specify the signatures of the EJB's remote methods.

There are two groups for remote methods.

The EJB container creates classes for the Java interface that will act as a proxy for the client. The client invokes a method on the generated proxies which in turn places the method arguments in a message and sends it to the EJB server. The EJB server is used to communicate by proxies.

The server will call a method from the Java implementation class to handle the remote method call.

The "Home" interface allows client code to manipulate methods that are not associated with a particular instance. The create method can be overload if you use the "Home" Interface.

The type of class methods that can be defined are methods that create an EJB or find an existing EJB.

Application developers can define new class methods without being limited to just creating or deletion them.

The public instance methods in charge of performing the operations are specified in the remote interface.

A session bean can only implement one interface with a different client type in mind. Those clients that run on the same virtual machine as the EJB container can use the local interface. The remote interface is for clients that are outside of the EJB container. The container returns a scrull of the object that implements the remote interface after a client query.

The server knows how to handle RPCs. This type of interface is also a POJO.

The EJB implementation classes are supplied by application developers who provide the business logic or maintain the business data of the object interface, that is, they implement all the methods specified by the application.

When calling the method on the " home" interface, calls are diverted to the corresponding method of the bean's implementation class, with the first letter of the " home" interface capitalized and keeping the same type of arguments.

For example: create.

The method calls on the remote interface are referred to as the implementation method of the bean's class.

The navigation semantic units do not comply with the standard that recommends screen shots on programmatic components.

The J2EE specification has evolved with the EJB specification. There are different versions that have existed.

• Look at and feel the ribs, the spine (back bone), and the pelvis.
• Look at the waist of the cat – also referred to as the abdominal tuck.
• Assess the amount of muscle present.
• Assess the amount of fat present – eg a saggy tummy!
• Look at the cat from above and from the side.