揭秘SpringBoot！一分鐘教你實(shí)現(xiàn)配置的動(dòng)態(tài)神刷新

更新時(shí)間：2024年03月08日 08:39:37 作者：無心六神通

在今天的指南中,我們將深入探索SpringBoot?動(dòng)態(tài)刷新的強(qiáng)大功能,讓你的應(yīng)用保持最新鮮的狀態(tài),想象一下,無需重啟,你的應(yīng)用就能實(shí)時(shí)更新配置,是不是很酷？跟我一起,讓我們揭開這項(xiàng)技術(shù)如何讓開發(fā)變得更加靈活和高效的秘密吧！

# I. 配置使用姿勢

既然要支持配置的動(dòng)態(tài)刷新，那么我們就得先看一下，在SpringBoot中，常見的配置使用姿勢有哪些

# 1. @Value注解綁定

直接通過@Value注解，將一個(gè)對象得成員變量與Environment中的配置進(jìn)行綁定，如

@Slf4j

@RestController

public class IndexController

@Value("${config.type:-1}")

private Integer type;

@Value("${config.wechat:默認(rèn)}")

private String wechat;


private String email;


@Value("${config.email:default@email}")

public IndexController setEmail(String email) {

this.email = email;

return this;

}

}

注意：@Value支持SpEL

# 2. @ConfigurationProperties綁定

通過@ConfigurationProperties注解聲明一個(gè)配置類，這個(gè)類中的成員變量都是從Environment中進(jìn)行初始化

如：

@ConfigurationProperties(prefix = "config")

public class MyConfig {


private String user;


private String pwd;


private Integer type;

}

# 3. Environment.getProperty()直接獲取配置

直接從上下文中獲取配置，也常見于各種使用場景中，如

environment.getProperty("config.user");

# II. 配置刷新

接下來我們看一下，如何實(shí)現(xiàn)配置刷新后，上面的三種使用姿勢都能獲取到刷新后的值

# 1. 自定義一個(gè)屬性配置源

自定義一個(gè)配置源，我們直接基于內(nèi)存的ConcurrentHashMap來進(jìn)行模擬，內(nèi)部提供了一個(gè)配置更新的方法，當(dāng)配置刷新之后，還會(huì)對外廣播一個(gè)配置變更事件

public class SelfConfigContext {

private static volatile SelfConfigContext instance = new SelfConfigContext();


public static SelfConfigContext getInstance() {

return instance;

}


private Map<String, Object> cache = new ConcurrentHashMap<>();


public Map<String, Object> getCache() {

return cache;

}


private SelfConfigContext() {

// 將內(nèi)存的配置信息設(shè)置為最高優(yōu)先級(jí)

cache.put("config.type", 33);

cache.put("config.wechat", "一灰灰blog");

cache.put("config.github", "liuyueyi");

}



/**

* 更新配置

*

* @param key

* @param val

*/

public void updateConfig(String key, Object val) {

cache.put(key, val);

ConfigChangeListener.publishConfigChangeEvent(key);

}

}



/**

* 主要實(shí)現(xiàn)配置變更事件發(fā)布于監(jiān)聽

*/

@Component

public class ConfigChangeListener implements ApplicationListener<ConfigChangeListener.ConfigChangeEvent> {


@Override

public void onApplicationEvent(ConfigChangeEvent configChangeEvent) {

SpringValueRegistry.updateValue(configChangeEvent.getKey());

}


public static void publishConfigChangeEvent(String key) {

SpringUtil.getApplicationContext().publishEvent(new ConfigChangeEvent(Thread.currentThread().getStackTrace()[0], key));

}


@Getter

public static class ConfigChangeEvent extends ApplicationEvent {

private String key;


public ConfigChangeEvent(Object source, String key) {

super(source);

this.key = key;

}

}

}

接下來就需要將這個(gè)自定義的配置元，注冊到 environment 上下文，在這里我們可以借助ApplicationContextInitializer來實(shí)現(xiàn)，在上下文初始化前，完成自定義配置注冊

【擴(kuò)展點(diǎn)】容器刷新前回調(diào)ApplicationContextInitializer | 一灰灰Blogopen in new window

public class SelfConfigContextInitializer implements ApplicationContextInitializer<ConfigurableApplicationContext> {

@Override

public void initialize(ConfigurableApplicationContext configurableApplicationContext) {

System.out.println("postProcessEnvironment#initialize");

ConfigurableEnvironment env = configurableApplicationContext.getEnvironment();

initialize(env);

}


protected void initialize(ConfigurableEnvironment environment) {

if (environment.getPropertySources().contains("selfSource")) {

// 已經(jīng)初始化過了，直接忽略

return;

}


MapPropertySource propertySource = new MapPropertySource("selfSource", SelfConfigContext.getInstance().getCache());

environment.getPropertySources().addFirst(propertySource);

}

}

接下來注冊這個(gè)擴(kuò)展點(diǎn)，直接選擇在項(xiàng)目啟動(dòng)時(shí)，進(jìn)行注冊

@SpringBootApplication

public class Application {

public static void main(String[] args) {

SpringApplication springApplication = new SpringApplication(Application.class);

springApplication.addInitializers(new SelfConfigContextInitializer());

springApplication.run(args);

}

}

# 2. Environment配置刷新

envionment實(shí)時(shí)獲取配置的方式，支持配置刷新應(yīng)該相對簡單，如直接吐出一個(gè)接口，支持更新我們自定義配置源的配置，不做任何變更，這個(gè)配置應(yīng)該時(shí)同時(shí)更新的

首先提供一個(gè)Spring的工具類，用于更簡單的獲取Spring上下文

@Component

public class SpringUtil implements ApplicationContextAware, EnvironmentAware {

private static ApplicationContext applicationContext;

private static Environment environment;


private static Binder binder;


@Override

public void setApplicationContext(ApplicationContext applicationContext) throws BeansException {

SpringUtil.applicationContext = applicationContext;

}


@Override

public void setEnvironment(Environment environment) {

SpringUtil.environment = environment;

binder = Binder.get(environment);

}


public static ApplicationContext getApplicationContext() {

return applicationContext;

}


public static Environment getEnvironment() {

return environment;

}


public static Binder getBinder() {

return binder;

}

}

配置更新的示例

@Slf4j

@RestController

public class IndexController {

@GetMapping(path = "update")

public String updateCache(String key, String val) {

SelfConfigContext.getInstance().updateConfig(key, val);

return "ok";

}


@GetMapping(path = "get")

public String getProperty(String key) {

return SpringUtil.getEnvironment().getProperty(key);

}

}

執(zhí)行驗(yàn)證一下:

# 3. `@ConfigurationProperties` 配置刷新

之前在介紹自定義屬性配置綁定時(shí)介紹過，通過Binder來實(shí)現(xiàn)綁定配置的Config對象動(dòng)態(tài)刷新，我們這里同樣可以實(shí)現(xiàn)配置變更時(shí)，主動(dòng)刷新@ConfigurationProperties注解綁定的屬性

具體實(shí)現(xiàn)如下，

@Slf4j
@Component
public class ConfigAutoRefresher implements ApplicationRunner {
    private Binder binder;
 
    /**
     * 配置變更之后的刷新
     */
    @EventListener()
    public void refreshConfig(ConfigChangeListener.ConfigChangeEvent event) {
        log.info("配置發(fā)生變更，開始動(dòng)態(tài)刷新: {}", event);
        SpringUtil.getApplicationContext().getBeansWithAnnotation(ConfigurationProperties.class).values().forEach(bean -> {
            Bindable<?> target = Bindable.ofInstance(bean).withAnnotations(AnnotationUtils.findAnnotation(bean.getClass(), ConfigurationProperties.class));
            bind(target);
        });
    }
 
    /**
     * 重新綁定bean對象對應(yīng)的配置值
     *
     * @param bindable
     * @param <T>
     */
    public <T> void bind(Bindable<T> bindable) {
        ConfigurationProperties propertiesAno = bindable.getAnnotation(ConfigurationProperties.class);
        if (propertiesAno != null) {
            BindHandler bindHandler = getBindHandler(propertiesAno);
            this.binder.bind(propertiesAno.prefix(), bindable, bindHandler);
        }
    }
 
    private BindHandler getBindHandler(ConfigurationProperties annotation) {
        BindHandler handler = new IgnoreTopLevelConverterNotFoundBindHandler();
        if (annotation.ignoreInvalidFields()) {
            handler = new IgnoreErrorsBindHandler(handler);
        }
        if (!annotation.ignoreUnknownFields()) {
            UnboundElementsSourceFilter filter = new UnboundElementsSourceFilter();
            handler = new NoUnboundElementsBindHandler(handler, filter);
        }
        return handler;
    }
 
    @Override
    public void run(ApplicationArguments args) throws Exception {
        log.info("初始化!");
        ConfigurableEnvironment environment = (ConfigurableEnvironment) SpringUtil.getEnvironment();
        this.binder = new Binder(ConfigurationPropertySources.from(environment.getPropertySources()),
                new PropertySourcesPlaceholdersResolver(environment),
                new DefaultConversionService(),
                ((ConfigurableApplicationContext) SpringUtil.getApplicationContext())
                        .getBeanFactory()::copyRegisteredEditorsTo);
    }
}

注意上面的實(shí)現(xiàn)，分三類：

public <T> void bind(Bindable<T> bindable): 具體實(shí)現(xiàn)綁定配置刷新的邏輯

核心思想就是將當(dāng)前對象與environment配置進(jìn)行重新綁定

public void run: binder初始化

在應(yīng)用啟動(dòng)之后進(jìn)行回調(diào)，確保是在environment準(zhǔn)備完畢之后回調(diào)，獲取用于屬性配置綁定的binder，避免出現(xiàn)envionment還沒有準(zhǔn)備好

也可以借助實(shí)現(xiàn)EnvironmentPostProcessor來實(shí)現(xiàn)

public void refreshConfig(ConfigChangeListener.ConfigChangeEvent event)：配置刷新

通過@EventListener監(jiān)聽配置變更事件，找到所有的ConfigurationProperties修飾對象，執(zhí)行重新綁定邏輯

接下來我們驗(yàn)證一下配置變更是否會(huì)生效

@Data
@Component
@ConfigurationProperties(prefix = "config")
public class UserConfig {
    private String user;
 
    private String pwd;
 
    private Integer type;
 
    private String wechat;
}
 
 
@Slf4j
@RestController
public class IndexController {
    @Autowired
    private UserConfig userConfig;
    @GetMapping(path = "/user")
    public UserConfig user() {
        return userConfig;
    }
 
    @GetMapping(path = "update")
    public String updateCache(String key, String val) {
        selfConfigContainer.refreshConfig(key, val);
        SelfConfigContext.getInstance().updateConfig(key, val);
        return JSON.toJSONString(userConfig);
    }
}

定義一個(gè)UserConfig來接收config前綴開始的配置，通過update接口來更新相關(guān)配置，更新完畢之后返回UserConfig的結(jié)果

# 4. @Value 配置刷新

最后我們再來看一下@Value注解綁定的配置的刷新策略

其核心思想就是找出所有@Value綁定的成員變量，當(dāng)監(jiān)聽到配置變更之后，通過反射的方式進(jìn)行刷新

關(guān)鍵的實(shí)現(xiàn)如下

/**
 * 配置變更注冊, 找到 @Value 注解修飾的配置，注冊到 SpringValueRegistry，實(shí)現(xiàn)統(tǒng)一的配置變更自動(dòng)刷新管理
 *
 * @author YiHui
 * @date 2023/6/26
 */
@Slf4j
@Component
public class SpringValueProcessor implements BeanPostProcessor {
    private final PlaceholderHelper placeholderHelper;
 
    public SpringValueProcessor() {
        this.placeholderHelper = new PlaceholderHelper();
    }
 
    @Override
    public Object postProcessBeforeInitialization(Object bean, String beanName) throws BeansException {
        Class clazz = bean.getClass();
        for (Field field : findAllField(clazz)) {
            processField(bean, beanName, field);
        }
        for (Method method : findAllMethod(clazz)) {
            processMethod(bean, beanName, method);
        }
        return bean;
    }
 
    private List<Field> findAllField(Class clazz) {
        final List<Field> res = new LinkedList<>();
        ReflectionUtils.doWithFields(clazz, res::add);
        return res;
    }
 
    private List<Method> findAllMethod(Class clazz) {
        final List<Method> res = new LinkedList<>();
        ReflectionUtils.doWithMethods(clazz, res::add);
        return res;
    }
 
    /**
     * 成員變量上添加 @Value 方式綁定的配置
     *
     * @param bean
     * @param beanName
     * @param field
     */
    protected void processField(Object bean, String beanName, Field field) {
        // register @Value on field
        Value value = field.getAnnotation(Value.class);
        if (value == null) {
            return;
        }
        Set<String> keys = placeholderHelper.extractPlaceholderKeys(value.value());
 
        if (keys.isEmpty()) {
            return;
        }
 
        for (String key : keys) {
            SpringValueRegistry.SpringValue springValue = new SpringValueRegistry.SpringValue(key, value.value(), bean, beanName, field);
            SpringValueRegistry.register(key, springValue);
            log.debug("Monitoring {}", springValue);
        }
    }
 
    /**
     * 通過 @Value 修飾方法的方式，通過一個(gè)傳參進(jìn)行實(shí)現(xiàn)的配置綁定
     *
     * @param bean
     * @param beanName
     * @param method
     */
    protected void processMethod(Object bean, String beanName, Method method) {
        //register @Value on method
        Value value = method.getAnnotation(Value.class);
        if (value == null) {
            return;
        }
        //skip Configuration bean methods
        if (method.getAnnotation(Bean.class) != null) {
            return;
        }
        if (method.getParameterTypes().length != 1) {
            log.error("Ignore @Value setter {}.{}, expecting 1 parameter, actual {} parameters", bean.getClass().getName(), method.getName(), method.getParameterTypes().length);
            return;
        }
 
        Set<String> keys = placeholderHelper.extractPlaceholderKeys(value.value());
 
        if (keys.isEmpty()) {
            return;
        }
 
        for (String key : keys) {
            SpringValueRegistry.SpringValue springValue = new SpringValueRegistry.SpringValue(key, value.value(), bean, beanName, method);
            SpringValueRegistry.register(key, springValue);
            log.info("Monitoring {}", springValue);
        }
    }
}

上面的實(shí)現(xiàn)，主要利用到BeanPostProcessor，在bean初始化之后，掃描當(dāng)前bean中是否有@Value綁定的屬性，若有，則注冊到自定義的SpringValueRegistry中

注意事項(xiàng)：

@Value有兩種綁定姿勢，直接放在成員變量上，以及通過方法進(jìn)行注入

所以上面的實(shí)現(xiàn)策略中，有Field和Method兩種不同的處理策略；

@Value支持SpEL表達(dá)式，我們需要對配置key進(jìn)行解析

相關(guān)的源碼，推薦直接在下面的項(xiàng)目中進(jìn)行獲取，demo中的實(shí)現(xiàn)也是來自apollo-client

接下來再看一下注冊配置綁定的實(shí)現(xiàn)，核心方法比較簡單，兩個(gè)，一個(gè)注冊，一個(gè)刷新

@Slf4j
public class SpringValueRegistry {
    public static Map<String, Set<SpringValue>> registry = new ConcurrentHashMap<>();
 
    /**
     * 像registry中注冊配置key綁定的對象W
     *
     * @param key
     * @param val
     */
    public static void register(String key, SpringValue val) {
        if (!registry.containsKey(key)) {
            synchronized (SpringValueRegistry.class) {
                if (!registry.containsKey(key)) {
                    registry.put(key, new HashSet<>());
                }
            }
        }
 
        Set<SpringValue> set = registry.getOrDefault(key, new HashSet<>());
        set.add(val);
    }
 
    /**
     * key對應(yīng)的配置發(fā)生了變更，找到綁定這個(gè)配置的屬性，進(jìn)行反射刷新
     *
     * @param key
     */
    public static void updateValue(String key) {
        Set<SpringValue> set = registry.getOrDefault(key, new HashSet<>());
        set.forEach(s -> {
            try {
                s.update((s1, aClass) -> SpringUtil.getBinder().bindOrCreate(s1, aClass));
            } catch (Exception e) {
                throw new RuntimeException(e);
            }
        });
    }
 
 
    @Data
    public static class SpringValue {
        /**
         * 適合用于：配置是通過set類方法實(shí)現(xiàn)注入綁定的方式，只有一個(gè)傳參，為對應(yīng)的配置key
         */
        private MethodParameter methodParameter;
        /**
         * 成員變量
         */
        private Field field;
        /**
         * bean示例的弱引用
         */
        private WeakReference<Object> beanRef;
        /**
         * Spring Bean Name
         */
        private String beanName;
        /**
         * 配置對應(yīng)的key： 如 config.user
         */
        private String key;
        /**
         * 配置引用，如 ${config.user}
         */
        private String placeholder;
        /**
         * 配置綁定的目標(biāo)類型
         */
        private Class<?> targetType;
 
        public SpringValue(String key, String placeholder, Object bean, String beanName, Field field) {
            this.beanRef = new WeakReference<>(bean);
            this.beanName = beanName;
            this.field = field;
            this.key = key;
            this.placeholder = placeholder;
            this.targetType = field.getType();
        }
 
        public SpringValue(String key, String placeholder, Object bean, String beanName, Method method) {
            this.beanRef = new WeakReference<>(bean);
            this.beanName = beanName;
            this.methodParameter = new MethodParameter(method, 0);
            this.key = key;
            this.placeholder = placeholder;
            Class<?>[] paramTps = method.getParameterTypes();
            this.targetType = paramTps[0];
        }
 
        /**
         * 配置基于反射的動(dòng)態(tài)變更
         *
         * @param newVal String: 配置對應(yīng)的key   Class: 配置綁定的成員/方法參數(shù)類型， Object 新的配置值
         * @throws Exception
         */
        public void update(BiFunction<String, Class, Object> newVal) throws Exception {
            if (isField()) {
                injectField(newVal);
            } else {
                injectMethod(newVal);
            }
        }
 
        private void injectField(BiFunction<String, Class, Object> newVal) throws Exception {
            Object bean = beanRef.get();
            if (bean == null) {
                return;
            }
            boolean accessible = field.isAccessible();
            field.setAccessible(true);
            field.set(bean, newVal.apply(key, field.getType()));
            field.setAccessible(accessible);
            log.info("更新value: {}#{} = {}", beanName, field.getName(), field.get(bean));
        }
 
        private void injectMethod(BiFunction<String, Class, Object> newVal)
                throws Exception {
            Object bean = beanRef.get();
            if (bean == null) {
                return;
            }
            Object va = newVal.apply(key, methodParameter.getParameterType());
            methodParameter.getMethod().invoke(bean, va);
            log.info("更新method: {}#{} = {}", beanName, methodParameter.getMethod().getName(), va);
        }
 
        public boolean isField() {
            return this.field != null;
        }
    }
}

SpringValue的構(gòu)建，主要就是基于反射需要使用到的一些關(guān)鍵信息的組成上；可以按需進(jìn)行設(shè)計(jì)補(bǔ)充

到此，關(guān)于@Value注解的配置動(dòng)態(tài)刷新就已經(jīng)實(shí)現(xiàn)了，接下來寫幾個(gè)demo驗(yàn)證一下

@Slf4j
@RestController
public class IndexController {
    @Value("${config.type:-1}")
    private Integer type;
    @Value("${config.wechat:默認(rèn)}")
    private String wechat;
 
    private String email;
 
    @Value("${config.email:default@email}")
    public IndexController setEmail(String email) {
        this.email = email;
        return this;
    }
 
 
    @GetMapping(path = "update")
    public String updateCache(String key, String val) {
        SelfConfigContext.getInstance().updateConfig(key, val);
        return wechat + "_" + type + "_" + email;
    }
}

# 5. 小結(jié)

本文主要介紹了項(xiàng)目中配置的動(dòng)態(tài)刷新的實(shí)現(xiàn)方案，也可以看作是apollo配置中心的簡易實(shí)現(xiàn)原理，其中涉及到的知識(shí)點(diǎn)較多，下面做一個(gè)簡單的小結(jié)

配置的三種使用姿勢

@Value綁定
@ConfigurationProperties綁定對象
environment.getProperty()

自定義配置源加載

environment.getPropertySources().addFirst(MapPropertySource)

配置刷新

Binder實(shí)現(xiàn)ConfigurationProperties刷新
反射實(shí)現(xiàn)@Value注解刷新

到此這篇關(guān)于揭秘SpringBoot！一分鐘教你實(shí)現(xiàn)配置的動(dòng)態(tài)神刷新的文章就介紹到這了,更多相關(guān)SpringBoot 動(dòng)態(tài)刷新內(nèi)容請搜索腳本之家以前的文章或繼續(xù)瀏覽下面的相關(guān)文章希望大家以后多多支持腳本之家！

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