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SpringBoot2.動(dòng)態(tài)@Value的實(shí)現(xiàn)方式

importmon.collect.Sets;

importorg.springframework.beans.factory.config.BeanDefinition;

importorg.springframework.beans.factory.config.BeanExpressionContext;

importorg.springframework.beans.factory.config.ConfigurableBeanFactory;

importorg.springframework.beans.factory.config.Scope;

importorg.springframework.util.StringUtils;

importjava.util.Set;

importjava.util.Stack;

*Placeholderhelperfunctions.

publicclassPlaceholderHelper{

privatestaticfinalStringPLACEHOLDER_PREFIX="${";

privatestaticfinalStringPLACEHOLDER_SUFFIX="}";

privatestaticfinalStringVALUE_SEPARATOR=":";

privatestaticfinalStringSIMPLE_PLACEHOLDER_PREFIX="{";

privatestaticfinalStringEXPRESSION_PREFIX="#{";

privatestaticfinalStringEXPRESSION_SUFFIX="}";

*Resolveplaceholderpropertyvalues,e.g.

*br/

*br/

*"${somePropertyValue}"-"theactualpropertyvalue"

publicObjectresolvePropertyValue(ConfigurableBeanFactorybeanFactory,StringbeanName,Stringplaceholder){

//resolvestringvalue

StringstrVal=beanFactory.resolveEmbeddedValue(placeholder);

BeanDefinitionbd=(beanFactory.containsBean(beanName)beanFactory

.getMergedBeanDefinition(beanName):null);

//resolveexpressionslike"#{systemProperties.myProp}"

returnevaluateBeanDefinitionString(beanFactory,strVal,bd);

privateObjectevaluateBeanDefinitionString(ConfigurableBeanFactorybeanFactory,Stringvalue,

BeanDefinitionbeanDefinition){

if(beanFactory.getBeanExpressionResolver()==null){

returnvalue;

Scopescope=(beanDefinition!=nullbeanFactory

.getRegisteredScope(beanDefinition.getScope()):null);

returnbeanFactory.getBeanExpressionResolver()

.evaluate(value,newBeanExpressionContext(beanFactory,scope));

*Extractkeysfromplaceholder,e.g.

*ul

*li${some.key}="some.key"/li

*li${some.key:${some.other.key:100}}="some.key","some.other.key"/li

*li${${some.key}}="some.key"/li

*li${${some.key:other.key}}="some.key"/li

*li${${some.key}:${another.key}}="some.key","another.key"/li

*li#{newjava.text.SimpleDateFormat('${some.key}').parse('${another.key}')}="some.key","another.key"/li

*/ul

publicSetStringextractPlaceholderKeys(StringpropertyString){

SetStringplaceholderKeys=Sets.newHashSet();

if(!isNormalizedPlaceholder(propertyString)!isExpressionWithPlaceholder(propertyString)){

returnplaceholderKeys;

StackStringstack=newStack();

stack.push(propertyString);

while(!stack.isEmpty()){

StringstrVal=stack.pop();

intstartIndex=strVal.indexOf(PLACEHOLDER_PREFIX);

if(startIndex==-1){

placeholderKeys.add(strVal);

continue;

intendIndex=findPlaceholderEndIndex(strVal,startIndex);

if(endIndex==-1){

//invalidplaceholder

continue;

StringplaceholderCandidate=strVal.substring(startIndex+PLACEHOLDER_PREFIX.length(),endIndex);

//${some.key:other.key}

if(placeholderCandidate.startsWith(PLACEHOLDER_PREFIX)){

stack.push(placeholderCandidate);

}else{

//some.key:${some.other.key:100}

intseparatorIndex=placeholderCandidate.indexOf(VALUE_SEPARATOR);

if(separatorIndex==-1){

stack.push(placeholderCandidate);

}else{

stack.push(placeholderCandidate.substring(0,separatorIndex));

StringdefaultValuePart=

normalizeToPlaceholder(placeholderCandidate.substring(separatorIndex+VALUE_SEPARATOR.length()));

if(!Strings.isNullOrEmpty(defaultValuePart)){

stack.push(defaultValuePart);

//hasremainingpart,e.g.${a}.$

if(endIndex+PLACEHOLDER_SUFFIX.length()strVal.length()-1){

StringremainingPart=normalizeToPlaceholder(strVal.substring(endIndex+PLACEHOLDER_SUFFIX.length()));

if(!Strings.isNullOrEmpty(remainingPart)){

stack.push(remainingPart);

returnplaceholderKeys;

privatebooleanisNormalizedPlaceholder(StringpropertyString){

returnpropertyString.startsWith(PLACEHOLDER_PREFIX)propertyString.endsWith(PLACEHOLDER_SUFFIX);

privatebooleanisExpressionWithPlaceholder(StringpropertyString){

returnpropertyString.startsWith(EXPRESSION_PREFIX)propertyString.endsWith(EXPRESSION_SUFFIX)

propertyString.contains(PLACEHOLDER_PREFIX);

privateStringnormalizeToPlaceholder(StringstrVal){

intstartIndex=strVal.indexOf(PLACEHOLDER_PREFIX);

if(startIndex==-1){

returnnull;

intendIndex=strVal.lastIndexOf(PLACEHOLDER_SUFFIX);

if(endIndex==-1){

returnnull;

returnstrVal.substring(startIndex,endIndex+PLACEHOLDER_SUFFIX.length());

privateintfindPlaceholderEndIndex(CharSequencebuf,intstartIndex){

intindex=startIndex+PLACEHOLDER_PREFIX.length();

intwithinNestedPlaceholder=0;

while(indexbuf.length()){

if(StringUtils.substringMatch(buf,index,PLACEHOLDER_SUFFIX)){

if(withinNestedPlaceholder0){

withinNestedPlaceholder--;

index=index