Details several ways that Spring can inject properties through the @Value annotation

scenario

If you have the following properties file dev.properties, inject the following tag

tag=123

Through PropertyPlaceholderConfigurer

<bean class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
  <property name="location" value="dev.properties" />
</bean>

code

@Value("${tag}")
private String tag;

Through PreferencesPlaceholderConfigurer

<bean id="appConfig" class="org.springframework.beans.factory.config.PreferencesPlaceholderConfigurer">
  <property name="location" value="dev.properties" />
</bean>

Code:

@Value("${tag}")
private String tag;

Through PropertiesFactoryBean

  <bean id="config" class="org.springframework.beans.factory.config.PropertiesFactoryBean">
    <property name="location" value="dev.properties" />
  </bean>

Code:

@Value("#{config['tag']}")
private String tag;

Through util: properties

The effect is the same as PropertiesFactoryBean1

Code:

@Value("#{config['tag']}")
private String tag;

The other way

Sometimes it is possible to write directly without using a document

<bean id="appConfig" class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
  <!--<property name="location" value="classpath:${env}.properties" />-->
  <property name="properties">
    <props>
      <prop key="tag">123</prop>
    </props>
  </property>
</bean>

Code:

@Value("${tag}")
private String tag;