Spring @Value注入值失败，错误信息提示：Could not resolve placeholder
问题根源：
@Value("${wx.app.config.appid}")
public Object appid;
异常信息：
Caused by: java.lang.IllegalArgumentException: Could not resolve placeholder 'wx.app.config.appid' in string value "${wx.app.config.appid}"
at org.springframework.util.PropertyPlaceholderHelper.parseStringValue(PropertyPlaceholderHelper.java:174)
at org.springframework.util.PropertyPlaceholderHelper.replacePlaceholders(PropertyPlaceholderHelper.java:126)
at org.springframework.core.env.AbstractPropertyResolver.doResolvePlaceholders(AbstractPropertyResolver.java:236)
at org.springframework.core.env.AbstractPropertyResolver.resolveRequiredPlaceholders(AbstractPropertyResolver.java:210)
at org.springframework.context.support.PropertySourcesPlaceholderConfigurer$2.resolveStringValue(PropertySourcesPlaceholderConfigurer.java:172)
at org.springframework.beans.factory.support.AbstractBeanFactory.resolveEmbeddedValue(AbstractBeanFactory.java:823)
at org.springframework.beans.factory.support.DefaultListableBeanFactory.doResolveDependency(DefaultListableBeanFactory.java:1084)
at org.springframework.beans.factory.support.DefaultListableBeanFactory.resolveDependency(DefaultListableBeanFactory.java:1064)
at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor$AutowiredFieldElement.inject(AutowiredAnnotationBeanPostProcessor.java:585)
at org.springframework.beans.factory.annotation.InjectionMetadata.inject(InjectionMetadata.java:88)
at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:366)
... 79 more
解决方法：
Spring引入.properties文件的两种方法（如下）
1.通过xml方式加载.properties文件
<bean class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer"> <property name="locations"> <array> <value>classpath:conn.propertiesvalue> array> property> bean>
2.通过注解方式加载.properties文件
<context:ignore-unresolvable="true" location="classpath:config/**/*.properties" system-properties-mode="OVERRIDE"/>
知道了怎么配置，就知道自己有没有配置错误，如果配置没有问题，那么就继续找问题，Could not resolve placeholder占位符不能被解析，那就是没有在.properties中找到要注入的值了，原来是在xml里面配置了2个ignore-unresolvable，这就是定位问题所在了。
<context:property-placeholder location="classpath*:/mybatis/db.properties"/> <context:property-placeholder ignore-unresolvable="true" location="classpath:config/config-wxapp.properties" ignore-resource-not-found="true"/>
一个是引入配置文件.properties，一个是引入db配置文件.properties，其实配置多个并不是报错的主要问题所在，是因为spring的加载机制，原来是Spring容器采用反射扫描的发现机制，在探测到Spring容器中有一个org.springframework.beans.factory.config.PropertyPlaceholderConfigurer的Bean就会停止对剩余PropertyPlaceholderConfigurer的扫描（Spring 3.1已经使用PropertySourcesPlaceholderConfigurer替代PropertyPlaceholderConfigurer了），所以根据加载的顺序，配置的第二个property-placeholder就被没有被spring加载，我想引入的config-wxapp.properties就没有被引入，所以在使用@Value注入的时候占位符就解析不了...解决方法就是把2个property-placeholder注解配置合并在一起就好了
<context:property-placeholder ignore-unresolvable="true" location="classpath*:config/config-*.properties,classpath*:mybatis/db.properties" ignore-resource-not-found="true"/>
posted @
2018-01-12 10:02 dawn-tangzedong 阅读(
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