java - @Value 注解和数据库 PropertyPlaceHolderConfigurer

Question

我的 Spring XML 中有两个 PropertyPlaceHolderConfigurer。第一个从文件中获取应用程序属性。第二个从数据库获取用户属性，如下所示:

<myConfiguration>
<bean id="databaseProperties"
            class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
            <property name="systemPropertiesModeName" value="SYSTEM_PROPERTIES_MODE_OVERRIDE" />
            <property name="properties">

                <bean class="org.apache.commons.configuration.ConfigurationConverter"
                    factory-method="getProperties">
                    <constructor-arg>
                        <ref bean="propertiesSource" />
                    </constructor-arg>
                </bean>
            </property>
        </bean>

        <bean id="propertiesSource" class="org.apache.commons.configuration.DatabaseConfiguration">
            <constructor-arg type="javax.sql.DataSource" ref="tomcatDataSource" />
            <constructor-arg value="application_properties" />
            <constructor-arg value="PROPERTY_KEY" />
            <constructor-arg value="PROPERTY_VALUE" />
        </bean>

        <bean id="propertiesService" class="com.xxx.PropertiesServiceImpl">
            <property name="propertiesSource" ref="propertiesSource"></property>
        </bean>
<myConfiguration>

它工作正常，我可以通过注入(inject)“propertiesService”来访问这些属性，例如:

@Autowired
private PropertiesService propertiesService;

这是:

public class PropertiesServiceImpl implements PropertiesService {

    @Autowired
    private DatabaseConfiguration propertiesSource;


    private Properties properties;

    @Override
    public String getProperty(String key) {
        if (properties == null) {
            properties = ConfigurationConverter.getProperties(propertiesSource);
        }
        return properties.getProperty(key);
    }


    @Override
    public Properties getProperties() {
        if (properties == null) {
            properties = ConfigurationConverter.getProperties(propertiesSource);
        }
        return properties;
    }

问题是我喜欢使用@Value注释，但它不起作用。

我已经尝试过:

private @Value("#{propertiesService.helloWorld}") String helloWorld;

当然，该属性存在并且可以通过“propertiesService”访问，但它会导致下一个错误:

Caused by: org.springframework.expression.spel.SpelEvaluationException: EL1008E:(pos 18): Property or field 'helloWorld' cannot be found on object of type 'com.infraportal.model.properties.PropertiesServiceImpl' - maybe not public?
    at org.springframework.expression.spel.ast.PropertyOrFieldReference.readProperty(PropertyOrFieldReference.java:224)
    at org.springframework.expression.spel.ast.PropertyOrFieldReference.getValueInternal(PropertyOrFieldReference.java:94)
    at org.springframework.expression.spel.ast.PropertyOrFieldReference.access$000(PropertyOrFieldReference.java:46)
    at org.springframework.expression.spel.ast.PropertyOrFieldReference$AccessorLValue.getValue(PropertyOrFieldReference.java:374)
    at org.springframework.expression.spel.ast.CompoundExpression.getValueInternal(CompoundExpression.java:88)
    at org.springframework.expression.spel.ast.SpelNodeImpl.getValue(SpelNodeImpl.java:120)
    at org.springframework.expression.spel.standard.SpelExpression.getValue(SpelExpression.java:242)
    at org.springframework.context.expression.StandardBeanExpressionResolver.evaluate(StandardBeanExpressionResolver.java:161)

这让我认为 Spring 正在寻找“getHelloWorld()”方法，而不是使用“getProperty(String key)”

有什么建议吗？

Answer 1

您需要在 EL 中引用的 bean 上显式指定要调用哪个方法，并提供如下参数值

@Value("#{propertiesService.getProperty('helloWorld')}") 
private String helloWorld;