第Value注解支持對象類型ConfigurationProperties功能目錄真實業(yè)務(wù)場景解決方案一解決方案二

真實業(yè)務(wù)場景

（不希望配置類注冊為Bean或不希望聲明@ConfigurationProperties）

假設(shè)某一個jar包內(nèi)封裝了DataSourceProperties

@Configuration

@ConfigurationProperties(

prefix="my.datasource"

@Data

publicclassDataSourceProperties{

privateListStringsuffix;

privateListDataSourceDetailProperties

在jar包的Configuration中，某個@Bean的構(gòu)造過程中引用了這個DataSourceProperties

publicJdbcTemplatebuildJdbcTemplate(DataSourcePropertiesdataSourceProperties){

在某個業(yè)務(wù)場景中，同時存在兩個DataSourceProperties會造成一個問題，注入的時候會提示有多個候選的bean但是沒法去修改Jar包中的內(nèi)容

自己重復(fù)寫一個DataSourceProperties不是很優(yōu)雅

這時候引出了一個需求，DataSourceProperties不希望注冊為Bean，但是能夠從配置文件讀取構(gòu)建對象

解決方案一

使用perties.bind.Binder從配置文件構(gòu)建配置對象

@Bean

publicJdbcTemplatebuildJdbcTemplate(Environmentenvironment){

Binderbinder=Binder.get(environment);

DataSourceProperties

properties1=binder.bind("my.datasource1",Bindable.of(DataSourceProperties.class)).get(),

properties2=binder.bind("my.datasource2",Bindable.of(DataSourceProperties.class)).get();

binder.bind(xxx,Bindable.of(type)).get()似乎是重復(fù)的編碼方式？

解決方案二

使@Value注解能夠支持自動調(diào)用這段代碼binder.bind(xxx,Bindable.of(type)).get()例如

@Bean

publicJdbcTemplatebuildJdbcTemplate(@Value("my.datasource1")DataSourcePropertiesproperties1,

@Value("my.datasource2")DataSourcePropertiesproperties2){

org.springframework.beans.factory.support.DefaultListableBeanFactory#doResolveDependency最后會交由converter處理

Classtype=descriptor.getDependencyType();

Objectvalue=getAutowireCandidateResolver().getSuggestedValue(descriptor);

if(value!=null){

if(valueinstanceofString){

StringstrVal=resolveEmbeddedValue((String)value);

BeanDefinitionbd=(beanName!=nullcontainsBean(beanName)

getMergedBeanDefinition(beanName):null);

value=evaluateBeanDefinitionString(strVal,bd);

TypeConverterconverter=(typeConverter!=nulltypeConverter:getTypeConverter());

try{

returnconverter.convertIfNecessary(value,type,descriptor.getTypeDescriptor());

catch(UnsupportedOperationExceptionex){

//AcustomTypeConverterwhichdoesnotsupportTypeDescriptorresolution...

return(descriptor.getField()!=null

converter.convertIfNecessary(value,type,descriptor.getField()):

converter.convertIfNecessary(value,type,descriptor.getMethodParameter()));

項目啟動時，添加StringtoObject的轉(zhuǎn)換器，支持@Value并且bind:開頭（防止影響@Value原有功能）

packagecom.nuonuo.accounting.guiding.support.spring;

importorg.springframework.beans.factory.annotation.Value;

importperties.bind.Bindable;

importperties.bind.Binder;

importorg.springframework.boot.convert.ApplicationConversionService;

importorg.springframework.context.ApplicationContextInitializer;

importorg.springframework.context.ConfigurableApplicationContext;

importorg.springframework.core.convert.TypeDescriptor;

importorg.springframework.core.convert.converter.ConditionalGenericConverter;

importjava.util.Set;

importstaticjava.util.Collections.singleton;

*@authoruhfun

publicclassValuePropertiesBindableAnnotationSupportimplementsApplicationContextInitializerConfigurableApplicationContext{

privatestaticfinalStringPREFIX="bind:";

@Override

publicvoidinitialize(ConfigurableApplicationContextcontext){

Binderbinder=Binder.get(context.getEnvironment());

((ApplicationConversionService)context.getBeanFactory().getConversionService()).addConverter(newConditionalGenericConverter(){

@Override

publicbooleanmatches(TypeDescriptorsourceType,TypeDescriptortargetType){

Valuevalue=targetType.getAnnotation(Value.class);

returnvalue!=nullvalue.value().startsWith(PREFIX);

@Override

publicSetConvertiblePairgetConvertibleTypes(){

returnsingleton(newConvertiblePair(String.class,Object.class));

@Override

publicObjectconvert(Objectsource,TypeDescriptorsourceType,TypeDescriptortargetType){

Valuevalue=targetType.getAnnotation(Value.class);

Classtype=targetType.getType();

assertvalue!=null;

returnbinder.bind(value.value().replace(PREFIX,""),Bindable.of(type)).get();

轉(zhuǎn)換后代碼執(zhí)行binder.bind(value.value().replace(PREFIX,),Bindable.of(type)).get();目的就達(dá)成了

在META-INF/spring.factories中添加注冊的Bean

#ApplicationContextInitializer

org.springframework.context.ApplicationContextInitializer=\

com.nuonuo.accounting.guiding.support.spring.ValuePropertiesBindableAnnotationSupport,\

最終效果

@Bean

publicJdbcTempl