01、前言
假设我们有个场景，我们需要实现服务之间的数据隔离、配置隔离、依赖的spring bean之间隔离。大家会有什么实现思路？今天给大家介绍spring-cloud-context里面有个NamedContextFactory可以达到上面的效果
NamedContextFactory简介
NamedContextFactory可以实现子容器，通过它创建子容器，然后通过NamedContextFactory.Specification可以定制子容器会用到的bean。
所以为什么通过NamedContextFactory可以达到数据隔离、配置隔离、依赖的spring bean之间隔离，本质就是利用NamedContextFactory为不同的服务，创建出不同的子容器，子容器之间彼此不共享，从而达到隔离的效果。
下面通过一个示例来讲解
02、示例
注： 示例就模拟一个用户注册成功后发送华为云短信，下单成功后发送阿里云短信为例子
01、模拟定义短信接口
代码语言：javascript复制public interface SmsService {
void send(String phone, String content);
}02、模拟定义相应短信实现类
代码语言：javascript复制public class DefaultSmsService implements SmsService {
@Override
public void send(String phone, String content) {
System.out.printf("send to %s content %s used default sms%n", phone, content);
}
}public class AliyunSmsService implements SmsService {
@Override
public void send(String phone, String content) {
System.out.printf("send to %s content %s used aliyun sms%n", phone, content);
}
}public class HuaWeiSmsService implements SmsService {
@Override
public void send(String phone, String content) {
System.out.printf("send to %s content %s used huawei sms%n", phone, content);
}
}03、自定义短信默认配置类
代码语言：javascript复制@Configuration
public class DefaultSmsClientConfiguration {
@Bean
@ConditionalOnMissingBean
public SmsService smsService(){
return new DefaultSmsService();
}
}04、定制短信需要的子容器NamedContextFactory.Specification
代码语言：javascript复制public class SmsClientSpecification implements NamedContextFactory.Specification{
private String name;
private Class<?>[] configuration;
public SmsClientSpecification() {
}
public SmsClientSpecification(String name, Class<?>[] configuration) {
this.name = name;
this.configuration = configuration;
}
@Override
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
@Override
public Class<?>[] getConfiguration() {
return configuration;
}
public void setConfiguration(Class<?>[] configuration) {
this.configuration = configuration;
}
@Override
public boolean equals(Object o) {
if (this == o) {
return true;
}
if (o == null || getClass() != o.getClass()) {
return false;
}
SmsClientSpecification that = (SmsClientSpecification) o;
return Arrays.equals(configuration, that.configuration)
&& Objects.equals(name, that.name);
}
@Override
public int hashCode() {
return Objects.hash(configuration, name);
}
@Override
public String toString() {
return new StringBuilder("SmsSpecification{").append("name='")
.append(name).append("', ").append("configuration=")
.append(Arrays.toString(configuration)).append("}").toString();
}
}属性讲解
name： 子容器的名称（示例中我们会把用户服务名和订单服务名当成子容器名称）
configuration： name子容器需要的configuration
NamedContextFactory.Specification的作用是当创建子容器时，如果容器的name匹配了Specification的name，则会加载 Specification对应Configuration类，并将Configuration类里面标注@Bean的返回值注入到子容器中
05、为不同的服务创建不同的SmsClientSpecification并注入到spring容器中
代码语言：javascript复制@Configuration
@Import(SmsClientConfigurationRegistrar.class)
@Target(ElementType.TYPE)
@Retention(RetentionPolicy.RUNTIME)
@Documented
public @interface SmsClient {
/**
* Synonym for name (the name of the client).
*
* @see #name()
* @return name of the Sms client
*/
String value() default "";
/**
* The name of the sms client, uniquely identifying a set of client resources,
* @return name of the Sms client
*/
String name() default "";
/**
* A custom <code>@Configuration</code> for the sms client. Can contain override
* <code>@Bean</code> definition for the pieces that make up the client
*/
Class<?>[] configuration() default {};
}@Configuration
@Retention(RetentionPolicy.RUNTIME)
@Target({ ElementType.TYPE })
@Documented
@Import(SmsClientConfigurationRegistrar.class)
public @interface SmsClients {
SmsClient[] value() default {};
Class<?>[] defaultConfiguration() default {};
}注： 利用import机制，将SmsClientSpecification注入到spring容器
代码语言：javascript复制public class SmsClientConfigurationRegistrar implements ImportBeanDefinitionRegistrar {
@Override
public void registerBeanDefinitions(AnnotationMetadata metadata,
BeanDefinitionRegistry registry) {
Map<String, Object> attrs = metadata
.getAnnotationAttributes(SmsClients.class.getName(), true);
if (attrs != null && attrs.containsKey("value")) {
AnnotationAttributes[] clients = (AnnotationAttributes[]) attrs.get("value");
for (AnnotationAttributes client : clients) {
registerClientConfiguration(registry, getClientName(client),
client.get("configuration"));
}
}
if (attrs != null && attrs.containsKey("defaultConfiguration")) {
String name;
if (metadata.hasEnclosingClass()) {
name = "default." metadata.getEnclosingClassName();
}
else {
name = "default." metadata.getClassName();
}
registerClientConfiguration(registry, name,
attrs.get("defaultConfiguration"));
}
Map<String, Object> client = metadata
.getAnnotationAttributes(SmsClient.class.getName(), true);
String name = getClientName(client);
if (name != null) {
registerClientConfiguration(registry, name, client.get("configuration"));
}
}
private String getClientName(Map<String, Object> client) {
if (client == null) {
return null;
}
String value = (String) client.get("value");
if (!StringUtils.hasText(value)) {
value = (String) client.get("name");
}
if (StringUtils.hasText(value)) {
return value;
}
throw new IllegalStateException(
"Either 'name' or 'value' must be provided in @SmsClient");
}
private void registerClientConfiguration(BeanDefinitionRegistry registry, Object name,
Object configuration) {
BeanDefinitionBuilder builder = BeanDefinitionBuilder
.genericBeanDefinition(SmsClientSpecification.class);
builder.addConstructorArgValue(name);
builder.addConstructorArgValue(configuration);
registry.registerBeanDefinition(name ".SmsClientSpecification",
builder.getBeanDefinition());
}
}06、创建短信NameContextFactory
代码语言：javascript复制public class SmsClientNameContextFactory extends NamedContextFactory<SmsClientSpecification> {
public SmsClientNameContextFactory() {
super(DefaultSmsClientConfiguration.class, "sms", "sms.client.name");
}
public SmsService getSmsService(String serviceName) {
return getInstance(serviceName, SmsService.class);
}
}注： super三个参数讲解
代码语言：javascript复制public NamedContextFactory(Class<?> defaultConfigType, String propertySourceName,
String propertyName) {
this.defaultConfigType = defaultConfigType;
this.propertySourceName = propertySourceName;
this.propertyName = propertyName;
}defaultConfigType： 默认配置类，NamedContextFactory创建子容器时，默认就会加载该配置类，该配置类主要用来做兜底，当找不到容器为name的configuration，则会使用该配置类 propertySourceName： 给propertySource取个名称 propertyName： 子容器可以通过读取配置propertyName来获取容器名。当创建子容器时通常会提供子容器的容器name。子容器中的Environment会被写入一条配置，sms.client.name=容器name
07、将SmsClientNameContextFactory注入到spring容器
代码语言：javascript复制@Bean
@ConditionalOnMissingBean
public SmsClientNameContextFactory smsClientNameContextFactory(@Autowired(required = false) List<SmsClientSpecification> smsSpecifications){
SmsClientNameContextFactory smsClientNameContextFactory = new SmsClientNameContextFactory();
smsClientNameContextFactory.setConfigurations(smsSpecifications);
return smsClientNameContextFactory;
}08、创建不同的短信配置类
代码语言：javascript复制public class AliyunSmsClientConfiguration {
@ConditionalOnMissingBean
@Bean
public SmsService smsService() {
return new AliyunSmsService();
}
}public class HuaWeiSmsClientConfiguration {
@ConditionalOnMissingBean
@Bean
public SmsService smsService() {
return new HuaWeiSmsService();
}
}注： 因为上述配置只需被子容器加载，因此不需要加 @Configuration
09、为用户服务和订单服务指定NamedContextFactory.Specification
代码语言：javascript复制@Configuration
@SmsClients(value = {@SmsClient(name = OrderService.SERVICE_NAME, configuration = AliyunSmsClientConfiguration.class),
@SmsClient(name = UserService.SERVICE_NAME, configuration = HuaWeiSmsClientConfiguration.class)})
public class SmsClientAutoConfiguration {
}10、测试
模拟用户注册
代码语言：javascript复制@Service
@RequiredArgsConstructor
public class UserService {
private final ApplicationContext applicationContext;
public static final String SERVICE_NAME = "userService";
public void registerUser(String userName, String password,String mobile){
System.out.println("注册用户" userName "成功");
UserRegisterEvent event = new UserRegisterEvent(userName,password,mobile);
applicationContext.publishEvent(event);
}
}@Component
@RequiredArgsConstructor
public class UserRegisterListener {
private final SmsClientNameContextFactory smsClientNameContextFactory;
@EventListener
@Async
public void listener(UserRegisterEvent event) {
SmsService smsService = smsClientNameContextFactory.getSmsService(UserService.SERVICE_NAME);
smsService.send(event.getMobile(), "恭喜您注册成功！初始密码为：" event.getPassword() "，请尽快修改密码！");
}
}核心：
代码语言：javascript复制SmsService smsService = smsClientNameContextFactory.getSmsService(UserService.SERVICE_NAME);和 @SmsClient(name = UserService.SERVICE_NAME）对应起来
运行查看控制台
当服务名不匹配时，再观察控制台
发现此时是走默认配置
03、总结
本文主要是聊下通过NamedContextFactory来实现服务隔离，核心点就是通过创建不同子容器进行隔离。这种方式在ribbon、openfeign、以及loadbalancer都有类似的实现，感兴趣朋友可以查阅其源码。不过这边有细节点需要注意，因为NamedContextFactory默认是懒加载创建子容器，所以可能第一次调用会比较慢。这也是ribbon第一次调用慢的原因
04、demo链接
https://github.com/lyb-geek/springboot-learning/tree/master/springboot-named-context-factory
