>>>>> 3 Springboot Source Code Analysis-Build Springapplication

 Package com.microservice.framework; Import org.springframework.boot.SpringApplication; Import org.springframework.boot.autoconfigure.SpringBootApplication; @SpringBootApplication  Public class myspringaplication {    publicvoid  run (string[] args) {        new springapplication (myspringaplication.  Class);        Sa.run (args);}    }

Springboot startup process:

1. Building Springapplication Objects

2. Execute run ()

First, build Springapplication object

     /**       * The application context would load beans from the specified sources       */public      c9> springapplication (Object ... sources) {         initialize (sources);     }

Description

• When the class is instantiated, the bean is loaded into the applicationcontext.
• The entry here is a Class<com.microservice.framework.myspringapplication> object such as Myspringapplication.class

Private Finalset<object> sources =NewLinkedhashset<object>(); Private Booleanwebenvironment; PrivateClass<?>Mainapplicationclass; Private voidInitialize (object[] sources) {if(Sources! =NULL&& sources.length > 0) {             This. Sources.addall (arrays.aslist (sources)); }         This. webenvironment =deducewebenvironment (); Setinitializers (Collection) getspringfactoriesinstances (Applicationcontextinitializer.class)); Setlisteners (Collection) getspringfactoriesinstances (Applicationlistener.class));  This. Mainapplicationclass =Deducemainapplicationclass (); }

Steps:

• Puts the incoming Myspringapplication.class object into the Set collection
• Determine if it is a Web environment
• Create a Applicationinitializer list
• Initializing the Applicationlistener list
• Initializing the main class Mainapplicationclass

1.1. Put the incoming Myspringapplication.class object into the set set

1.2. Determine if it is a Web environment:

Private Static FinalString[] web_environment_classes = {"Javax.servlet.Servlet",            "Org.springframework.web.context.ConfigurableWebApplicationContext" }; Private Booleandeducewebenvironment () { for(String classname:web_environment_classes) {if(! Classutils.ispresent (ClassName,NULL)) {                return false; }        }        return true; }

Description: By looking in classpath for the existence of all classes contained in the web_environment_classes array (actually 2 classes), if present the current program is a Web application, or vice versa.

1.3. Create a Applicationcontextinitializer list

PrivateList<applicationcontextinitializer<?>>initializers;  Public voidsetinitializers (Collection<?extendsApplicationcontextinitializer<?>>initializers) {         This. initializers =NewArraylist<applicationcontextinitializer<?>>();  This. Initializers.addall (initializers); }    Private<T> collection<?extendsT> Getspringfactoriesinstances (class<t>type) {        returnGetspringfactoriesinstances (Type,NewClass<?>[] {}); }    Private<T> collection<?extendsT> Getspringfactoriesinstances (class<t>type, Class<?>[] parametertypes, Object ... args) {ClassLoader ClassLoader=Thread.CurrentThread (). Getcontextclassloader (); //Use names and ensure unique to protect against duplicatesset<string> names =NewLinkedhashset<string>(Springfactoriesloader.loadfactorynames (Type, classLoader)); List<T> instances =NewArraylist<t>(Names.size ()); //Create instances from the names         for(String name:names) {Try{Class<?> Instanceclass =classutils.forname (name, ClassLoader);                Assert.isassignable (type, instanceclass); Constructor<?> constructor =Instanceclass.getconstructor (parametertypes); T instance=(T) constructor.newinstance (args);            Instances.add (instance); }            Catch(Throwable ex) {Throw NewIllegalArgumentException ("Cannot instantiate" + Type + ":" +name, ex);        }} annotationawareordercomparator.sort (instances); returninstances; }

Steps:

• Call Springfactoriesloader.loadfactorynames (type, classLoader) to get all the names of spring factories, (Here is the full class name for the four Applicationcontextinitializer implementation classes, see below)
• Creates its object for each spring factories based on the name read. (4 objects created here)
• Sorts and returns the list of created objects.

where Springfactoriesloader.loadfactorynames (type, ClassLoader) is as follows:

/*** The location-to-look for factories.     * <p>can is present in multiple JAR files. */     Public Static FinalString factories_resource_location = "Meta-inf/spring.factories"; /*** Load The fully qualified class names of factory implementations of the * given type from {@value#FACTORIES_RESOURCE_LOCATION}, using the given * class loader. */     Public StaticList<string> Loadfactorynames (class<?>Factoryclass, ClassLoader ClassLoader) {String Factoryclassname=Factoryclass.getname (); Try{Enumeration<URL> urls = (ClassLoader! =NULL?classloader.getresources (factories_resource_location): Classloader.getsystemresources (FACTORIES_R            esource_location)); List<String> result =NewArraylist<string>();  while(Urls.hasmoreelements ()) {URL URL=urls.nextelement (); Properties Properties= Propertiesloaderutils.loadproperties (Newurlresource (URL)); String Factoryclassnames=Properties.getproperty (factoryclassname);            Result.addall (Arrays.aslist (Stringutils.commadelimitedlisttostringarray (Factoryclassnames))); }            returnresult; }        Catch(IOException ex) {Throw NewIllegalArgumentException ("Unable to load [" + factoryclass.getname () + "] factories from location [" + Factories_resource_location + "]", ex); }    }

Meta-inf/spring-factories

1 # application Context initializers2 org.springframework.context.applicationcontextinitializer=3 Org.springframework.boot.context.ConfigurationWarningsApplicationContextInitializer,4  Org.springframework.boot.context.ContextIdApplicationContextInitializer,5  Org.springframework.boot.context.config.DelegatingApplicationContextInitializer,6 Org.springframework.boot.context.web.ServerPortInfoApplicationContextInitializer

Description

• Get all the meta-inf/spring-factories files from all jars. (There is only one under Spring-boot-1.3.0.release.jar here)
• Iterate through each of the spring-factories files and get its next key to Factoryclass.getname () (Here is the entry

  Org.springframework.context.ApplicationContextInitializer) value (here are the above four Applicationcontextinitializer implementation classes)

The effect of the above four classes:

At this point, the setup applicationcontextinitialize is complete.

Summary: The entire setinitializers is actually initializing the properties of Springapplication list<applicationcontextinitializer<?>> Initializers is a list of ArrayList, with four instances in the list:

• Examples of Configurationwarningsapplicationcontextinitializer
• Examples of Contextidapplicationcontextinitializer
• Delegatingapplicationcontextinitializer instances
• Serverportinfoapplicationcontextinitializer instances

1.4. Initialize the Applicationlistener list

PrivateList<applicationlistener<?>>listeners; /*** Sets the {@linkApplicationlistener}s that would be applied to the springapplication * and registered with the {@linkApplicationContext}. * @paramlisteners the listeners to set*/     Public voidSetlisteners (collection<?extendsApplicationlistener<?>>listeners) {         This. Listeners =NewArraylist<applicationlistener<?>>();  This. Listeners.addall (listeners); }

Meta-inf/spring-factories

# application Listenersorg.springframework.context.ApplicationListener=  Org.springframework.boot.builder.ParentContextCloserApplicationListener, Org.springframework.boot.context.FileEncodingApplicationListener, Org.springframework.boot.context.config.AnsiOutputApplicationListener, Org.springframework.boot.context.config.ConfigFileApplicationListener, Org.springframework.boot.context.config.DelegatingApplicationListener, Org.springframework.boot.liquibase.LiquibaseServiceLocatorApplicationListener, Org.springframework.boot.logging.ClasspathLoggingApplicationListener, Org.springframework.boot.logging.LoggingApplicationListener

The functions of the above eight listener are as follows:

At this point, the entire Setlisteners method is finished, initializing a list collection containing the above 8 Applicationlistener instances.

1.5. Initialize the main class Mainapplicationclass

PrivateClass<?>Mainapplicationclass; PrivateClass<?>Deducemainapplicationclass () {Try{stacktraceelement[] stackTrace=Newruntimeexception (). Getstacktrace ();  for(stacktraceelement stacktraceelement:stacktrace) {if("Main". Equals (Stacktraceelement.getmethodname ())) {                    returnClass.forName (Stacktraceelement.getclassname ()); }            }        }        Catch(ClassNotFoundException ex) {//Swallow and Continue        }        return NULL; }

Description: Gets the main class object where the main () method resides and assigns a value to the Mainapplicationclass property of Springapplication.

At this point, the initialization of the Springapplication object is complete.

Summary: The entire springapplication initialization process, is the initialization of the

• a sources that contains the myspringapplication.class of the entry parameter . Set<object>
• Whether a current environment is a Boolean webenvironment of the Web environment
• A list that contains 4 Applicationcontextinitializer instances
• A list that contains 8 Applicationlistener instances
• A class object of the main class where the Main method resides.

Attention:

This article basic reference Http://zhaox.github.io/java/2016/03/22/spring-boot-start-flow complete, the author of the article has been resolved very well, I copy it here again, just to deepen the memory!!!

>>>>> 3 Springboot Source Code Analysis-Build Springapplication