2, Application Context
(1) What is Application Context
l Concentrated application information that can be used by all components
l bean defined position
l Load multiple contexts
l level contexts
l IL8N, message resources
l Resource access
l Event communication
(2) ApplicationContext
l extended BeanFactory
l can have a parent Context
l Implementation:
FileSystemXmlapplicationContext
ClassPathXMLApplicationContext
XMLWebApplicationContext
l example:
ApplicationContext CTX = New FileSystemXmlapplicationContext ("c: /beans.xml");
EXAMPLEBEAN EB = (Examplebean) CTX.getBean ("ExampleBean");
l ApplicationContext can read multiple files
String [] ctxs = new string [] {"ctx1.xml", "ctx2.xml"};
ApplicationContext CTX = New FileSystemXmlapplicationContext (CTXS);
(3) Level Contexts
l If a bean is not found in Context, it will go to the parent CONTEXT to find
l Create a hierarchical contexts
ApplicationContext Parent = New ClassPathXMLApplicationContext ("CTX1.xml");
ApplicationContext CTX = New FileSystemXmlapplicationContext ("CTX2.xml", Parent);
(4) Resources
l ApplicationContext processing resource location
l ApplicationContext method:
Resource getResource (String location)
• URL full circuit, such as File: C: /Test.dat
? Relative file path, such as web-inf / Test.dat
ClassPath Pseudo URL, such as ClassPath: Test.dat
Interface resource {
Boolean exissrs ();
Boolean isopen ();
String getdescription ();
File getFile () throws oException;
InputStream GetInputStream () THROWS IOException;
}
(5) Resource editor
l Built-in PropertyEditor
l Configuring resource properties in Bean definitions
l example:
(6) IL8N
l International application news
l ApplicationContext method:
String getMessage (String code, Object [] args, string default, locale LOC
Represents a Messagesource Bean.
l ApplicationContext Search for Messagesource Bean (Must implement Messagesource interface)
l Example: Define two resource beam messages and errors in ClassPath
Search in ClassPath:
Messages_PT_br.properties ErrorS_PT_Br.Properties
Messages_pt.properties Errors_pt.properties
Messages.properties ERRORS.PROPERTIES
(7) event
l Event communication
• ApplicationContext handling events, call listeners
Beans must implement the ApplicationListener interface to receive events
? Application can extend ApplicationEvent
? Built-in event:
2 contextrefreeshedEvent
2 ContextCloseDevent
2 RequesthandEvent
l Listening event
Public class mylistenerbean imports applicationListener {
Public void onapplicationEvent (ApplicationEvent E) {
// process evenet
}
}
l Send event
Public Class ExampleBeaMplements ApplicationContextaWare {
ApplicationContext CTX;
Public void setApplicationContext (ApplicationContext CTX)
Throws beansexception {
THIS.CTX = CTX;
}
Public void sendevent () {
CTX.Publishevent (New MyApplicationEvent (this));
}
}
(8) BeanFactoryPostProcessor
l can be used to configure BeanFactory or Beans in it; application context automatically detect BeanFactoryPostProcessor's beans in their bean definition, applying them before other Beans created
l POST Processor Bean must implement the BeanFactoryPostProcessor interface L example: add a custom editor to Context
Public class mypostProcessor imports beanfactoryPostProcessor {
Void PostProcessBeanFactory (ConfigurableListableBeanFactory bf) {
DateFormat FMT = New SimpleDateFormat ("D / M / YYYY");
CustomDateEditor DateEditor = New CustomDateEditor (FMT, FALSE);
Bf.registerCustomeditor (java.util.date.class, dateeditor);
}
}
(9) CustomeditorConfigurer
l BeanFactoryPostProcessor implements a convenient registration custom property editor
(10) Typical application contexts
l Application Contexts is usually linked to a range defined by the J2EE server.
• Javax.Servlet.ServletContext: SRING provides the ability to instantiate the Context by listener or servlet
? Servlet: Each servlet can have its own application Context, from the web application context
? EJBS: Load from the XML document in the EJB JAR file
l Don't use Singleton to boot bean factory
