Spring Environment拓展点

有时候，开发者需要在系统的bean初始化前，内置环境变量到Spring的Environment，下面就介绍三种环境变量生效方式。

介绍前，先提供下内置环境变量到Environment的公共代码。

公共代码

public class DefaultGatewayProperties {

    public static final String ENDPOINT_PATH = "flux.metadata-registry.endpointPath";
    public static final String ROOT_PATH = "flux.metadata-registry.root-path";
    public static final String SERVICE_PATH = "flux.metadata-registry.servicePath";
    public static final String ADDRESS = "flux.metadata-registry.address";

    public Map<String, Object> getDefaultProperties(ConfigurableEnvironment environment) {
        if (environment.getPropertySources().contains("gatewayEnvironment")) {
            return null;
        }
        Map<String, Object> gatewayProperties = getGatewayProperties(environment);
        return gatewayProperties;
    }

    private Map<String, Object> getGatewayProperties(ConfigurableEnvironment environment) {
        Map<String, Object> gatewayEnvironment = new HashMap<>();
        gatewayEnvironment.put(ENDPOINT_PATH, "/admin-endpoint");
        gatewayEnvironment.put(ROOT_PATH, "/admin-endpoint");
        gatewayEnvironment.put(SERVICE_PATH, "/admin-service");
        String address = environment.getProperty("biz.zookeeper.address");
        if (StringUtils.isBlank(address)) {
            address = environment.getProperty("zookeeper.address");
        }
        gatewayEnvironment.put(ADDRESS, address);
        // 内置配置到 Environment
        MapPropertySource propertySource = new MapPropertySource("gatewayEnvironment", gatewayEnvironment);
        environment.getPropertySources().addFirst(propertySource);
        return gatewayEnvironment;
    }
}

方式一：FactoryBean & property-placeholder

public class GatewayPropertiesFactoryBean extends DefaultGatewayProperties implements FactoryBean<Properties>, EnvironmentAware {

    private Environment environment;

    @Override
    public Properties getObject() throws Exception {
        Properties p = new Properties();
        Map<String, Object> defaultProperties = super.getDefaultProperties((ConfigurableEnvironment) environment);
        if (defaultProperties != null) {
            p.putAll(defaultProperties);
        }
        return p;
    }

    @Override
    public Class<?> getObjectType() {
        return Properties.class;
    }

    @Override
    public void setEnvironment(Environment environment) {
        this.environment = environment;
    }
}

<bean id="configBeanConfigBean"
      class="com.access.boot.autoconfigure.env.GatewayPropertiesFactoryBean"/>
<context:property-placeholder properties-ref="configBeanConfigBean"/>

方式二：EnvironmentPostProcessor

在 META-INF/spring.factories 配置

org.springframework.boot.env.EnvironmentPostProcessor=\
	com.access.boot.autoconfigure.GatewayEnvironmentPostProcessor

/**
 * 通过 spring.factories 配置
 * org.springframework.boot.env.EnvironmentPostProcessor=\
 * com.access.boot.autoconfigure.GatewayEnvironmentPostProcessor
 * 使用 @Configuration 等其他方式配置不生效
 */
public class GatewayEnvironmentPostProcessor extends DefaultGatewayProperties implements EnvironmentPostProcessor {

    @Override
    public void postProcessEnvironment(ConfigurableEnvironment environment, SpringApplication application) {
        super.getDefaultProperties(environment);
    }
}

方式三：GatewayApplicationContextInitializer

Apollo配置中心是通过这种方式实现Apollo的数据初始化。

在 META-INF/spring.factories 配置

org.springframework.boot.env.EnvironmentPostProcessor=\
	com.access.boot.autoconfigure.GatewayApplicationContextInitializer

/**
 * 通过 spring.factories 配置
 * org.springframework.context.ApplicationContextInitializer=\
 * com.access.boot.autoconfigure.GatewayApplicationContextInitializer
 */
public class GatewayApplicationContextInitializer extends DefaultGatewayProperties implements
        ApplicationContextInitializer<ConfigurableApplicationContext> {

    @Override
    public void initialize(ConfigurableApplicationContext context) {
        ConfigurableEnvironment environment = context.getEnvironment();
        super.getDefaultProperties(environment);
    }
}