如何在Spring 4中使用注释重新加载属性文件？

Question

我有一个简单的应用程序，其中我使用几个属性文件来获取其他用户编辑的内容（指向网站的链接等）。

我加载属性的类如下所示：

@Configuration
@PropertySource("classpath:salestipsWhitelist.properties")
public class SalestipsWhitelist {

@Autowired
Environment env;

public Environment getEnv() {
    return env;
}

public void setEnv(Environment env) {
    this.env = env;
}

@Bean
   public static PropertySourcesPlaceholderConfigurer propertySourcesPlaceholderConfigurer() {
      return new PropertySourcesPlaceholderConfigurer();
   }
}

一些属性文件：

UPS_MPP_M_L=True
UPS_MPP_M_M=True
UPS_MPP_M_MP=True
UPS_MPP_M_S=True

这可以正常工作，但是如果我对properties-file进行更改，则必须重新加载应用程序以可视化所做的任何更改。

如果我将位置移动到磁盘而不是类路径，是否可以定期或手动重新加载？ 我不希望更改时自动完成此操作，因为我想控制何时完成/更新。

Answer 1

这可以治疗。 需要Java 7，Apache Commons日志记录，Apache Commons lang（v2.6）和Apache Commons Configuration：

package corejava.reloadTest;

import org.apache.commons.configuration.ConfigurationException;
import org.apache.commons.configuration.PropertiesConfiguration;
import org.apache.commons.configuration.reloading.FileChangedReloadingStrategy;

public class MyApplicationProperties {
    private static PropertiesConfiguration configuration = null;

    static {
        try {
            configuration = new PropertiesConfiguration("test.properties");
        } catch (ConfigurationException e) {
            e.printStackTrace();
        }
        configuration.setReloadingStrategy(new FileChangedReloadingStrategy());
    }

    public static synchronized String getProperty(final String key) {
        return (String) configuration.getProperty(key);
    }
}

并使用以下命令进行测试：

package corejava.reloadTest;

public class TestReloading {
    public static void main(String[] args) {
        while (true) {
            try {
                Thread.sleep(2000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            System.out.println(MyApplicationProperties.getProperty("key"));
        }
    }
}

更改test.properties时的输出是这样的（test.props的原始内容是key = value，后来在程序执行中更改为key = value1）：

value
value
value
value
value
Jan 17, 2015 2:05:26 PM org.apache.commons.configuration.PropertiesConfiguration reload
INFO: Reloading configuration. URL is file:/D:/tools/workspace   /AutoReloadConfigUsingApacheCommons/resources/test.properties
value1
value1
value1

您也可以考虑使用类似Groovy的DSL来考虑《 Spring Framework官方参考文档》可 刷新bean 。

Answer 2

必须重写PropertyPlaceholderConfigurer才能重新加载新的Properties

您需要重写processProperties方法，以使包含属性的StringValueResolver变为可加载。 这是我的代码

import java.io.IOException;
import java.util.Properties;
import org.springframework.beans.BeansException;
import org.springframework.beans.factory.config.ConfigurableListableBeanFactory;
import org.springframework.beans.factory.config.PropertyPlaceholderConfigurer;
import org.springframework.util.PropertyPlaceholderHelper;
import org.springframework.util.PropertyPlaceholderHelper.PlaceholderResolver;
import org.springframework.util.StringValueResolver;


public class ReloadablePropertyPlaceholderConfigurer 
                                    extends PropertyPlaceholderConfigurer {

    private ReloadablePlaceholderResolvingStringValueResolver reloadableValueResolver;


    public void reloadProperties() throws IOException {
        Properties props = mergeProperties();
        this.reloadableValueResolver.refreshProperties(props);
    }


    @Override
    protected void processProperties(ConfigurableListableBeanFactory beanFactoryToProcess, Properties props)
            throws BeansException {
        this.reloadableValueResolver = new ReloadablePlaceholderResolvingStringValueResolver(props);
        StringValueResolver valueResolver = this.reloadableValueResolver;
        this.doProcessProperties(beanFactoryToProcess, valueResolver);
    }


    private class ReloadablePlaceholderResolvingStringValueResolver 
            implements StringValueResolver {

        private final PropertyPlaceholderHelper helper;
        private final ReloadablePropertyPlaceholderConfigurerResolver resolver;

        public ReloadablePlaceholderResolvingStringValueResolver(Properties props) {
            this.helper = new PropertyPlaceholderHelper(placeholderPrefix, placeholderSuffix, valueSeparator, ignoreUnresolvablePlaceholders);
            this.resolver = new ReloadablePropertyPlaceholderConfigurerResolver(props);
        }

        @Override
        public String resolveStringValue(String strVal) throws BeansException {
            String value = this.helper.replacePlaceholders(strVal, this.resolver);
            return (value.equals(nullValue) ? null : value);
        }

        private void refreshProperties(Properties props){
            this.resolver.setProps(props);
        }
    }

    private class ReloadablePropertyPlaceholderConfigurerResolver 
            implements PlaceholderResolver {

        private Properties props;
        private ReloadablePropertyPlaceholderConfigurerResolver(Properties props) {
            this.props = props;
        }

        @Override
        public String resolvePlaceholder(String placeholderName) {
            return ReloadablePropertyPlaceholderConfigurer.this.resolvePlaceholder(placeholderName, props, SYSTEM_PROPERTIES_MODE_FALLBACK);
        }

        public void setProps(Properties props) {
            this.props = props;
        }
   }
}

这是properties-config.xml的配置。所有这些属性都可以在运行时作为原型Bean重新加载。

<bean id="propertyConfigurer" class="com.cn21.mail189.analysis.commons.expand.ReloadablePropertyPlaceholderConfigurer">
    <property name="ignoreUnresolvablePlaceholders" value="true" />
    <property name="locations">
        <list>
            <!-- database config -->
            <value>classpath:spring/dbconfig.properties</value>
            <!-- app config -->
            <value>classpath:spring/app.properties</value>
            <!-- some other config -->
            <value>classpath:xxxx.properties</value>
        </list>
    </property>
</bean>`

Answer 3

内部applicationContext.xml

<bean id="beanId" class="org.apache.commons.configuration.reloading.FileChangedReloadingStrategy">
    <property name="refreshDelay" value="30000" /> <!-- 30 seconds -->
</bean>
<bean id="reloadableProperties" class="org.apache.commons.configuration.PropertiesConfiguration">
    <constructor-arg value="file:/web/${weblogic.Domain}/${weblogic.Name}/${app.Name}/reloadable_cfg/Reloadable.properties"/>
    <property name="reloadingStrategy" ref="propertiesReloadingStrategy"/>
</bean>