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配置文件@ConfigurationProperties读取List、Map参数

背景

在SpringBoot环境中，我们有“使用不完的”注解。这也是SpringBoot替代了传统的Spring项目中的xml配置的原因。在使用这些annotation的时候，我们一定要了解这些注解背后的原理以及约定。

package org.springframework.boot.context.properties;

import java.lang.annotation.Documented;  
import java.lang.annotation.ElementType;  
import java.lang.annotation.Retention;  
import java.lang.annotation.RetentionPolicy;  
import java.lang.annotation.Target;

import org.springframework.core.annotation.AliasFor;

@Target({ ElementType.TYPE, ElementType.METHOD })
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface ConfigurationProperties {  
  ......
}

支持的类型

List

custom.config.config1.folders[0]=/root  
custom.config.config1.folders[1]=/home/user1  
custom.config.config1.folders[2]=/home/user2

对应的Java实现

@ConfigurationProperties(prefix = "custom.config.config1")
public class Config1Properties{  
    private List<String> folders;
    ...
}

Map

custom.config.config1.map.key1=value1  
custom.config.config1.map.key2=value2  
custom.config.config1.map.key3=value3  
custom.config.config1.map.key4=value4  
custom.config.config1.map.key5=value5

对应的Java实现

@ConfigurationProperties(prefix = "custom.config.config1")
public class Config1Properties{  
    private Map<String, String> map;
    ...
}

Object

custom.config.config1.server.host=host1  
custom.config.config1.server.port=22  
custom.config.config1.server.username=username1  
custom.config.config1.server.password=password1

对应的Java实现

@ConfigurationProperties(prefix = "custom.config.config1")
public class Config1Properties{  
    private ServerProperties server;
    ...
    public static class ServerProperties {
        private String host;
        private int port;
        private String username;
        private String password;
        ...
    }
}

Object List

custom.config.config1.servers[0].host=host1  
custom.config.config1.servers[0].port=22  
custom.config.config1.servers[0].username=username1  
custom.config.config1.servers[0].password=password1  
custom.config.config1.servers[1].host=host2  
custom.config.config1.servers[1].port=22  
custom.config.config1.servers[1].username=username2  
custom.config.config1.servers[1].password=password2

对应的Java实现

@ConfigurationProperties(prefix = "custom.config.config1")
public class Config1Properties{  
    private List<ServerProperties> servers;
    ...
    public static class ServerProperties {
        private String host;
        private int port;
        private String username;
        private String password;
        ...
    }
}

Map的使用案例

比如，我们同时需要连接多个OSS（阿里对象存储），那我们就可以利用ConfigurationProperties的方式来配置多个。而且可以通过Spring的加载动态的注入到容器中去。

配置中心的配置：

# OSS1配置
oss.multi.clients.accout.accessKeyId=xxx  
oss.multi.clients.accout.accessKeySecret=xxx  
oss.multi.clients.accout.privateEndpoint=xxx  
oss.multi.clients.accout.bucketName=bucket-b-test

# OSS2配置
oss.multi.enabled=true  
oss.multi.clients.xdtrans.accessKeyId=xxx  
oss.multi.clients.xdtrans.accessKeySecret=xxx  
oss.multi.clients.xdtrans.privateEndpoint=xxx  
oss.multi.clients.xdtrans.bucketName=bucket-a-test

对应的Java实现

@Data
@EqualsAndHashCode(callSuper = false)
@ConfigurationProperties(prefix = OssConstants.MULTI_CONFIG_PREFIX)
public class MultiOssProperties {  
    private Map<String, OssProperties> clients;

    @Data
    public static class OssProperties {
        private String accessKeyId;
        private String accessKeySecret;
        private String publicEndpoint;
        private String privateEndpoint;
        private String bucketName;
        private String object;
    }

动态的定义我们需要的BeanDefinition。

public class MultiOssScannerConfigurer implements BeanDefinitionRegistryPostProcessor, InitializingBean, ApplicationContextAware, BeanNameAware {

    private ApplicationContext applicationContext;

    @Setter
    private MultiOssProperties multiOssProperties;

    @Override
    public void setBeanName(String name) {
        log.info("init bean {}", name);
    }

    @Override
    public void afterPropertiesSet() throws Exception {
        Objects.requireNonNull(this.multiOssProperties, "multiOssProperties不能为空");
        Objects.requireNonNull(this.applicationContext, "applicationContext不能为空");
    }

  // 动态的定义Bean
    @Override
    public void postProcessBeanDefinitionRegistry(BeanDefinitionRegistry beanDefinitionRegistry) throws BeansException {
        String beanSuffixName = StringUtils.capitalize(OssConstants.BEAN_SUFFIX_NAME);
    // productCodes实际与oss.multi.clients.xdtrans的xdtrans保持一致
        multiOssProperties.getClients().forEach((productCode, ossProperties) -> {
            AbstractBeanDefinition beanDefinition = BeanDefinitionBuilder.genericBeanDefinition(OssClient.class,
                    () -> OssClientUtils.buildOssClient(ossProperties))
                    .getRawBeanDefinition();
            beanDefinition.setInitMethodName("init");
            beanDefinition.setDestroyMethodName("shutDown");
            beanDefinitionRegistry.registerBeanDefinition(productCode + beanSuffixName, beanDefinition);
        });
    }

    @Override
    public void postProcessBeanFactory(ConfigurableListableBeanFactory configurableListableBeanFactory) throws BeansException {
    }

    @Override
    public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {
        this.applicationContext = applicationContext;
    }

}

通过binder来让配置与对应的Java代码产生关系：

@Configuration
@EnableConfigurationProperties(MultiOssProperties.class)
@ConditionalOnProperty(prefix = OssConstants.MULTI_CONFIG_PREFIX, value = "enabled")
public class MultiOssAutoConfiguration {

    /**
     * 初始化多个 ossClient 自动配置
     *
     * @param environment 环境变量属性
     * @return OssClient 自动扫描注册器
     */
    @Bean
    public MultiOssScannerConfigurer multiOssScannerConfigurer(Environment environment) {
        Binder binder = Binder.get(environment);
        MultiOssProperties properties = binder.bind(OssConstants.MULTI_CONFIG_PREFIX, MultiOssProperties.class).get();
        MultiOssScannerConfigurer multiOssScannerConfigurer = new MultiOssScannerConfigurer();
        multiOssScannerConfigurer.setMultiOssProperties(properties);
        return multiOssScannerConfigurer;
    }
}

如何使用?

@Getter
@AllArgsConstructor
public enum OssTypeEnum {  
        // 注意一下这里的beanName,要跟上面的postProcessBeanDefinitionRegistry保持一致
    XDtransOssClient("xdtransOssClient", "oss1"),
    DianDianOssClient("ddacctOssClient", "oss2"),
    ;

    private final String beanName;
    private final String desc;

    // 根据BeanName来Spring容器中获取即可
    public OssClient getBean() {
        return SpringContextHolder.getBean(beanName, OssClient.class);
    }

Binder是如何映射的？

通过上面的代码 binder.bind(OssConstants.MULTI_CONFIG_PREFIX, MultiOssProperties.class).get(); 来进行bind。

protected final <T> T bind(ConfigurationPropertyName name, Bindable<T> target, BindHandler handler, Context context, boolean allowRecursiveBinding) {  
        context.clearConfigurationProperty();
        try {
            target = handler.onStart(name, target, context);
            if (target == null) {
                return null;
            }
            Object bound = bindObject(name, target, handler, context,allowRecursiveBinding);
            return handleBindResult(name, target, handler, context, bound);
        } catch (Exception ex) {
            return handleBindError(name, target, handler, context, ex);
        }
}

如果我们的key是：oss.multi.clients.accout.xxx

实际上对应的是Map，那么它的引用名字就是clients。具体的key就是accout，那么对应的value就是OssProperties。

private Object bindBean(ConfigurationPropertyName name, Bindable<?> target,  
        BindHandler handler, Context context, boolean allowRecursiveBinding) {
    if (containsNoDescendantOf(context.getSources(), name)
            || isUnbindableBean(name, target, context)) {
        return null;
    }
    BeanPropertyBinder propertyBinder = (propertyName, propertyTarget) -> bind(
            name.append(propertyName), propertyTarget, handler, context, false);
    Class<?> type = target.getType().resolve(Object.class);
    if (!allowRecursiveBinding && context.hasBoundBean(type)) {
        return null;
    }
    return context.withBean(type, () -> {
        Stream<?> boundBeans = BEAN_BINDERS.stream()
                .map((b) -> b.bind(name, target, context, propertyBinder));
        return boundBeans.filter(Objects::nonNull).findFirst().orElse(null);
    });
}

配置文件@ConfigurationProperties读取List、Map参数

具体的一个bind情况。

private static final List<BeanBinder> BEAN_BINDERS;

static {  
    List<BeanBinder> binders = new ArrayList<>();
    binders.add(new JavaBeanBinder());
    BEAN_BINDERS = Collections.unmodifiableList(binders);
}

public <T> T bind(ConfigurationPropertyName name, Bindable<T> target, Context context,  
        BeanPropertyBinder propertyBinder) {
    boolean hasKnownBindableProperties = hasKnownBindableProperties(name, context);
    Bean<T> bean = Bean.get(target, hasKnownBindableProperties);
    if (bean == null) {
        return null;
    }
    BeanSupplier<T> beanSupplier = bean.getSupplier(target);
    boolean bound = bind(propertyBinder, bean, beanSupplier);
    return (bound ? beanSupplier.get() : null);
}
// 返回对应的对象
public BeanSupplier<T> getSupplier(Bindable<T> target) {  
    return new BeanSupplier<>(() -> {
        T instance = null;
        if (target.getValue() != null) {
            instance = target.getValue().get();
        }
        if (instance == null) {
            instance = (T) BeanUtils.instantiateClass(this.resolvedType);
        }
        return instance;
    });
}