Springboot @Value注入boolean如何设置默认值
Springboot @Value注入boolean如何设置默认值
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@Value注入boolean设置默认值
问题描述
Springboot 中读取配置文件
test：
业务代码如下
@Value("${test:true}")privatebooleantest;
报错如下
nested exception is org.springframework.beans.TypeMismatchException: Failed to convert value of type 'java.lang.String' to required type 'boolean'; nested exception is java.lang.IllegalArgumentException: Invalid boolean value []
问题分析
根据报错可知，主要问题在于 注入时 test 的值是 String 类型，无法转换成 boolean 类型。
@Value("${test:true}")privateStringtest;
于是更改了接收类型，看看获取到的值是否是 true，结果发现 test 值为 “”，而不是设置的默认值
解决方案
报错问题在于只要配置文件中有 test: 所以系统就默认 test 为 “” 而不是按照我所设想的为空所以默认值为 true。
直接删除配置文件中的 test: 即可正常启动。
@Value 源码阅读
在排查问题的过程中也粗略的跟读了一下源码
//org.springframework.beans.TypeConverterSupport#doConvert()private<T>TdoConvert(Objectvalue,Class<T>requiredType,MethodParametermethodParam,Fieldfield)throwsTypeMismatchException{try{returnfield!=null?this.typeConverterDelegate.convertIfNecessary(value,requiredType,field):this.typeConverterDelegate.convertIfNecessary(value,requiredType,methodParam);}catch(ConverterNotFoundExceptionvar6){thrownewConversionNotSupportedException(value,requiredType,var6);}catch(ConversionExceptionvar7){thrownewTypeMismatchException(value,requiredType,var7);}catch(IllegalStateExceptionvar8){thrownewConversionNotSupportedException(value,requiredType,var8);}catch(IllegalArgumentExceptionvar9){//最终异常从这里抛出thrownewTypeMismatchException(value,requiredType,var9);}}
最终赋值在
//org.springframework.beans.TypeConverterDelegate#doConvertTextValue()privateObjectdoConvertTextValue(ObjectoldValue,StringnewTextValue,PropertyEditoreditor){try{editor.setValue(oldValue);}catch(Exceptionvar5){if(logger.isDebugEnabled()){logger.debug("PropertyEditor["+editor.getClass().getName()+"]doesnotsupportsetValuecall",var5);}}//此处发现newTextValue为""editor.setAsText(newTextValue);returneditor.getValue();}
接下来就是如何将 字符串 true 转换为 boolean 的具体代码：
//org.springframework.beans.propertyeditors.CustomBooleanEditor#setAsText()publicvoidsetAsText(Stringtext)throwsIllegalArgumentException{Stringinput=text!=null?text.trim():null;if(this.allowEmpty&&!StringUtils.hasLength(input)){this.setValue((Object)null);}elseif(this.trueString!=null&&this.trueString.equalsIgnoreCase(input)){this.setValue(Boolean.TRUE);}elseif(this.falseString!=null&&this.falseString.equalsIgnoreCase(input)){this.setValue(Boolean.FALSE);}elseif(this.trueString!=null||!"true".equalsIgnoreCase(input)&&!"on".equalsIgnoreCase(input)&&!"yes".equalsIgnoreCase(input)&&!"1".equals(input)){if(this.falseString!=null||!"false".equalsIgnoreCase(input)&&!"off".equalsIgnoreCase(input)&&!"no".equalsIgnoreCase(input)&&!"0".equals(input)){thrownewIllegalArgumentException("Invalidbooleanvalue["+text+"]");}this.setValue(Boolean.FALSE);}else{this.setValue(Boolean.TRUE);}}
tips：windows 中使用 IDEA 去查找类可以使用 ctrl + shift +alt +N的快捷键组合去查询，mac 系统则是 commond + O
Spring解析@Value
1、初始化PropertyPlaceholderHelper对象
protectedStringplaceholderPrefix="${";protectedStringplaceholderSuffix="}";@NullableprotectedStringvalueSeparator=":";privatestaticfinalMap<String,String>wellKnownSimplePrefixes=newHashMap<>(4);static{wellKnownSimplePrefixes.put("}","{");wellKnownSimplePrefixes.put("]","[");wellKnownSimplePrefixes.put(")","(");}publicPropertyPlaceholderHelper(StringplaceholderPrefix,StringplaceholderSuffix,@NullableStringvalueSeparator,booleanignoreUnresolvablePlaceholders){Assert.notNull(placeholderPrefix,"'placeholderPrefix'mustnotbenull");Assert.notNull(placeholderSuffix,"'placeholderSuffix'mustnotbenull");//默认值${this.placeholderPrefix=placeholderPrefix;//默认值}this.placeholderSuffix=placeholderSuffix;StringsimplePrefixForSuffix=wellKnownSimplePrefixes.get(this.placeholderSuffix);//当前缀为空或跟定义的不匹配，取传入的前缀if(simplePrefixForSuffix!=null&&this.placeholderPrefix.endsWith(simplePrefixForSuffix)){this.simplePrefix=simplePrefixForSuffix;}else{this.simplePrefix=this.placeholderPrefix;}//默认值:this.valueSeparator=valueSeparator;this.ignoreUnresolvablePlaceholders=ignoreUnresolvablePlaceholders;}
2、解析@Value
protectedStringparseStringValue(Stringvalue,PlaceholderResolverplaceholderResolver,Set<String>visitedPlaceholders){StringBuilderresult=newStringBuilder(value);//是否包含前缀，返回第一个前缀的开始indexintstartIndex=value.indexOf(this.placeholderPrefix);while(startIndex!=-1){//找到最后一个后缀的indexintendIndex=findPlaceholderEndIndex(result,startIndex);if(endIndex!=-1){//去掉前缀后缀，取出里面的字符串Stringplaceholder=result.substring(startIndex+this.placeholderPrefix.length(),endIndex);StringoriginalPlaceholder=placeholder;if(!visitedPlaceholders.add(originalPlaceholder)){thrownewIllegalArgumentException("Circularplaceholderreference'"+originalPlaceholder+"'inpropertydefinitions");}//递归判断是否存在占位符，可以这样写${acm.endpoint:${address.server.domain:}}placeholder=parseStringValue(placeholder,placeholderResolver,visitedPlaceholders);//根据key获取对应的值StringpropVal=placeholderResolver.resolvePlaceholder(placeholder);//值不存在，但存在默认值的分隔符if(propVal==null&&this.valueSeparator!=null){//获取默认值的索引intseparatorIndex=placeholder.indexOf(this.valueSeparator);if(separatorIndex!=-1){//切掉默认值的字符串StringactualPlaceholder=placeholder.substring(0,separatorIndex);//切出默认值StringdefaultValue=placeholder.substring(separatorIndex+this.valueSeparator.length());//根据新的key获取对应的值propVal=placeholderResolver.resolvePlaceholder(actualPlaceholder);//如果值不存在，则把默认值赋值给当前值if(propVal==null){propVal=defaultValue;}}}//如果当前值不为NULLif(propVal!=null){//递归获取存在占位符的值信息propVal=parseStringValue(propVal,placeholderResolver,visitedPlaceholders);//替换占位符result.replace(startIndex,endIndex+this.placeholderSuffix.length(),propVal);if(logger.isTraceEnabled()){logger.trace("Resolvedplaceholder'"+placeholder+"'");}startIndex=result.indexOf(this.placeholderPrefix,startIndex+propVal.length());}elseif(this.ignoreUnresolvablePlaceholders){//Proceedwithunprocessedvalue.startIndex=result.indexOf(this.placeholderPrefix,endIndex+this.placeholderSuffix.length());}else{thrownewIllegalArgumentException("Couldnotresolveplaceholder'"+placeholder+"'"+"invalue\""+value+"\"");}visitedPlaceholders.remove(originalPlaceholder);}else{startIndex=-1;}}returnresult.toString();}
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