Spring source Reading (vi)

This is an analysis of the Spring Bean attribute injection code Populatebean, the source analysis is as follows

    /*** Populate The Bean instance in the given Beanwrapper and the property values * from the bean definition. * Enrich Bean Instance Properties *@paramBeanname The name of the bean *@paramMBD The bean definition for the bean *@parambw Beanwrapper with Bean instance*/    protected voidPopulatebean (String beanname, rootbeandefinition mbd, @Nullable beanwrapper bw) {propertyvalues PVs=mbd.getpropertyvalues (); if(BW = =NULL) {            if(!Pvs.isempty ()) {                Throw Newbeancreationexception (Mbd.getresourcedescription (), Beanname,"Cannot apply property values to null instance"); }            Else {                //Skip Property Population phase for null instance.                return; }        }        //Give any instantiationawarebeanpostprocessors the opportunity to modify the//State of the bean before properties is set. This can is used, for example,//To the support styles of field injection. //call the processor before the property is set        BooleanContinuewithpropertypopulation =true; if(!mbd.issynthetic () &&hasinstantiationawarebeanpostprocessors ()) {             for(Beanpostprocessor bp:getbeanpostprocessors ()) {if(BPinstanceofinstantiationawarebeanpostprocessor) {Instantiationawarebeanpostprocessor IBP=(Instantiationawarebeanpostprocessor) BP; if(!ibp.postprocessafterinstantiation (Bw.getwrappedinstance (), beanname)) {continuewithpropertypopulation=false;  Break; }                }            }        }        if(!continuewithpropertypopulation) {            return; }        if(Mbd.getresolvedautowiremode () = = Rootbeandefinition.autowire_by_name | |Mbd.getresolvedautowiremode ()==Rootbeandefinition.autowire_by_type) {mutablepropertyvalues Newpvs=Newmutablepropertyvalues (PVS); //Add property values based on Autowire by name if applicable.            if(Mbd.getresolvedautowiremode () = =rootbeandefinition.autowire_by_name)            {Autowirebyname (beanname, MBD, BW, Newpvs); }            //Add property values based on Autowire by type if applicable.            if(Mbd.getresolvedautowiremode () = =Rootbeandefinition.autowire_by_type)            {Autowirebytype (beanname, MBD, BW, Newpvs); } PVs=Newpvs; }        BooleanHasinstawarebpps =hasinstantiationawarebeanpostprocessors (); BooleanNeedsdepcheck = (Mbd.getdependencycheck ()! =Rootbeandefinition.dependency_check_none); //Set Bean Properties        if(Hasinstawarebpps | |Needsdepcheck) {propertydescriptor[] Filteredpds=Filterpropertydescriptorsfordependencycheck (BW, mbd.allowcaching); if(Hasinstawarebpps) { for(Beanpostprocessor bp:getbeanpostprocessors ()) {if(BPinstanceofinstantiationawarebeanpostprocessor) {Instantiationawarebeanpostprocessor IBP=(Instantiationawarebeanpostprocessor) BP; PVs=ibp.postprocesspropertyvalues (PVs, Filteredpds, Bw.getwrappedinstance (), beanname); if(PVs = =NULL) {                            return; }                    }                }            }            if(Needsdepcheck) {checkdependencies (Beanname, MBD, Filteredpds, PVS);    }} applypropertyvalues (Beanname, MBD, BW, PVS); }

During the debug process we know that there are 7 beanpostprocessor in total

For @autowired, the attribute value injected by the @Value annotation is autowiredannotationbeanpostprocessor processed. We further analyze the code for Autowiredannotationbeanpostprocessor injection properties

    /*** autowired Attribute injection *@authorCoshaho *@paramPVs *@paramPDS Injection Property configuration, not used in method *@paramBean Bean Instance *@paramBeanname *@return     * @throwsbeancreationexception*/     Publicpropertyvalues postprocesspropertyvalues (propertyvalues PVs, propertydescriptor[] pds, Object Bean, Strin G Beanname)throwsbeancreationexception {//Get Injection Property configuration informationInjectionmetadata metadata =Findautowiringmetadata (Beanname, Bean.getclass (), PVS); Try {            //Attribute Injectionmetadata.inject (Bean, beanname, PVS); }        Catch(Beancreationexception ex) {Throwex; }        Catch(Throwable ex) {Throw NewBeancreationexception (Beanname, "Injection of autowired dependencies failed", ex); }        returnPVs; }     Public voidInject (Object target, @Nullable String beanname, @Nullable propertyvalues PVs)throwsThrowable {//get the property queue to be injectedCollection<injectedelement> checkedelements = This. checkedelements; Collection<InjectedElement> elementstoiterate =(checkedelements!=NULL? Checkedelements: This. injectedelements); if(!Elementstoiterate.isempty ()) {            Booleandebug =logger.isdebugenabled ();  for(injectedelement element:elementstoiterate) {if(Debug) {Logger.debug ("Processing injected element of bean '" + beanname + "':" +element); }                //Attribute InjectionElement.inject (Target, Beanname, PVS); }        }    }

Injectionmetadata is the bean injection property configuration, Injectionelement is a single injection property configuration, and Injectionelement.inject is a single attribute injection method. Injectionelement.inject calls the Defaultlistablebeanfactory.doresolvedependency method to get the property value

@Overrideprotected voidInject (Object bean, @Nullable String beanname, @Nullable propertyvalues PVs)throwsthrowable {Field field= (Field) This. Member;        Object value; if( This. Cached) {Value= Resolvedcachedargument (Beanname, This. Cachedfieldvalue); }        Else {            //Get Injection Property Configuration: Property name, class nameDependencydescriptor desc =NewDependencydescriptor (field, This. required);            Desc.setcontainingclass (Bean.getclass ()); Set<String> Autowiredbeannames =NewLinkedhashset<> (1); Assert.state (Beanfactory!=NULL, "No beanfactory available"); TypeConverter TypeConverter=Beanfactory.gettypeconverter (); Try {                //Get Property valueValue =beanfactory.resolvedependency (DESC, Beanname, Autowiredbeannames, TypeConverter); }            Catch(Beansexception ex) {Throw NewUnsatisfieddependencyexception (NULL, Beanname,Newinjectionpoint (field), ex); }            synchronized( This) {                if(! This. Cached) {                    if(Value! =NULL|| This. Required) {                         This. Cachedfieldvalue =desc;                        Registerdependentbeans (Beanname, autowiredbeannames); if(autowiredbeannames.size () = = 1) {String autowiredbeanname=Autowiredbeannames.iterator (). Next (); if(Beanfactory.containsbean (autowiredbeanname)) {if(Beanfactory.istypematch (Autowiredbeanname, Field.gettype ())) { This. Cachedfieldvalue =Newshortcutdependencydescriptor (DESC, Autowiredbeanname, Field.gettype ());                    }                            }                        }                    } Else {                         This. Cachedfieldvalue =NULL; }                     This. cached =true; }            }        }        if(Value! =NULL) {reflectionutils.makeaccessible (field); //Reflection Settings PropertiesField.set (bean, value); }    }         PublicObject resolvedependency (dependencydescriptor descriptor, @Nullable String requestingbeanname, @Nullable S ET<String> autowiredbeannames, @Nullable TypeConverter TypeConverter)throwsbeansexception {descriptor.initparameternamediscovery (Getparameternamediscoverer ()); if(Optional.class==Descriptor.getdependencytype ()) {            returncreateoptionaldependency (descriptor, requestingbeanname); }        Else if(Objectfactory.class= = Descriptor.getdependencytype () | |Objectprovider.class==Descriptor.getdependencytype ()) {            return NewDependencyobjectprovider (descriptor, requestingbeanname); }        Else if(Javaxinjectproviderclass = =Descriptor.getdependencytype ()) {            return Newjsr330providerfactory (). Createdependencyprovider (descriptor, requestingbeanname); }        Else{Object result=getautowirecandidateresolver (). Getlazyresolutionproxyifnecessary (descriptor, requestingbeanname); if(Result = =NULL) {                //Get injected valueresult =doresolvedependency (descriptor, Requestingbeanname, Autowiredbeannames, TypeConverter); }            returnresult; }    }

Spring source Reading (vi)