7 Using JSP components

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7 Using JSP components
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7.1 The JSP component model

• ? JavaBeans
• 7.1.1 Component architectures
• Component self-contained, reusable software
  elements that encapsulate application behavior or
  data into a discrete package
• 7.1.2 Benefits of a component architecture
• Abstraction
• Reusability
• 7.1.3 Component design for web projects
• 7.1.4 Building applications from components

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7.2 JavaBean fundamentals

• Bean containers? allows developers to call up
  beans, configure them and access their
  information and behavior
• Bean properties
• ? named attributes of the bean that maintain its
  state and control its behavior
• Trigger and linked properties? properties used
  to trigger behavior and report information?
  changing the value of one updates the value of
  others linked properties
• Indexed properties? collection of values, each
  value is accessible through an index number
• Property data types? Java primitives, Java
  objects, user-defined objects, other beans
• Bean property sheets? description of the
  features of a bean

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7.2 JavaBean fundamentals

• 7.2.1 The different types of JavaBeans
• Visual component beans? elements of GUIs
• Data beans? access to a collection of
  information
• Service beans? perform specific tasks or
  calculations ( worker beans)

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7.3 JSP bean tags

• 7.3.1 Tag-based component programming
• 7.3.2 Accessing JSP components
• 7.3.3 Initializing beans
• 7.3.4 Controlling a beans scope

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7.3 JSP bean tags

• 7.3.1 Tag-based component programming
• ltjspuseBeangtltjspsetPropertygtltjspgetPropertygt
• Custom tag libraries? support additional
  programming constructions and functionality

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7.3 JSP bean tags

• 7.3.2 Accessing JSP components
• The ltjspuseBeangt tag
• make a bean available by creating or fetching an
  existing one from the server
• requires two attributes id and class
• ltjspuseBean idbean name classclass namegt
• other attributes scope, type, beanName
• The ID attribute
• unique name for the bean
• case sensitive
• first character must be a letter
• only letters, numbers and _ are allowed

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7.3 JSP bean tags

• 7.3.2 Accessing JSP components
• The class attribute
• fully qualified name of the bean class
• The type attribute
• if you need to refer to the bean as another type,
  for example a base class or an interface that the
  bean implements
• if you specify both class and type, the bean will
  be created using the class, then cast to type
• The beanName attribute
• specifies the name of a bean which will be passed
  to the instantiate() method of the
  java.beans.Beans class
• can be assigned throug a runtime expression

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7.3 JSP bean tags

• 7.3.2 Accessing JSP components
• The tag body
• Initialize any user configurable properties of
  the bean
• ltjspuseBeangt in action
• Only available to portions of the page following
  the tag
• Accessing bean properties with ltjspgetPropertygt
• ltjspgetProperty namebean name
  propertyproperty name/gt
• The ltjspsetPropertygt tag
• ltjspsetProperty namebean name
  propertyproperty name valueproperty value/gt
• Indexed properties
• Collection of values
• lt bean.getPropertyName(index) gt

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7.3 JSP bean tags

• 7.3.3 Initializing beans
• ? setting the value of configurable properties
• ? first time the bean is created
• bean configuration
• in the body tag of ltjspuseBeangt
• ltjspuseBean idmyBean classbe.syntra.MyBeangt
  ltjspsetProperty namemyBean
  propertycounter value0/gtlt/jspuseBeangt
• initializing beans from the request
• ltform actionpage.jspgt
• Specifying default initialization values
• ltjspsetProperty namecounter propertystart
  value0/gtltjspsetProperty namecounter
  propertystart valuestartValue/gt
• A security consideration
• ltjspsetProperty property/gt

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7.3 JSP bean tags

• 7.3.4 Controlling a beans scope