hystrix緩存的作用是
- 1.減少重復的請求數，降低依賴服務的返回數據始終保持一致。
- 2.==在同一個用戶請求的上下文中，相同依賴服務的返回數據始終保持一致==。
- 3.請求緩存在run()和construct()執行之前生效，所以可以有效減少不必要的線程開銷。
1 通過HystrixCommand類實現
1.1 開啟緩存功能
繼承HystrixCommand或HystrixObservableCommand，覆蓋getCacheKey()方法，指定緩存的key，開啟緩存配置。
import com.netflix.hystrix.HystrixCommand;import com.netflix.hystrix.HystrixCommandGroupKey;import com.netflix.hystrix.HystrixCommandKey;import com.netflix.hystrix.HystrixRequestCache;import com.netflix.hystrix.strategy.concurrency.HystrixConcurrencyStrategyDefault;import com.szss.demo.orders.vo.UserVO;import org.slf4j.Logger;import org.slf4j.LoggerFactory;import org.springframework.web.client.RestTemplate;public class UserCacheCommand extends HystrixCommand<UserVO> { private static final Logger LOGGER = LoggerFactory.getLogger(UserCacheCommand.class); private static final HystrixCommandKey GETTER_KEY= HystrixCommandKey.Factory.asKey("CommandKey"); private RestTemplate restTemplate; private String username; public UserCacheCommand(RestTemplate restTemplate, String username) { super(Setter.withGroupKey(HystrixCommandGroupKey.Factory.asKey("userCacheCommand")).andCommandKey(GETTER_KEY)); this.restTemplate = restTemplate; this.username = username; } @Override protected UserVO run() throws Exception { LOGGER.info("thread:" + Thread.currentThread().getName()); return restTemplate.getForObject("http://users-service/user/name/{username}", UserVO.class, username); } @Override protected UserVO getFallback() { UserVO user = new UserVO(); user.setId(-1L); user.setUsername("調用失敗"); return user; } @Override protected String getCacheKey() { return username; } public static void flushCache(String username){ HystrixRequestCache.getInstance(GETTER_KEY, HystrixConcurrencyStrategyDefault.getInstance()).clear(username); }}1.2 配置HystrixRequestContextServletFilter
通過servlet的Filter配置hystrix的上下文。
import com.netflix.hystrix.strategy.concurrency.HystrixRequestContext;import javax.servlet.*;import javax.servlet.annotation.WebFilter;import java.io.IOException;@WebFilter(filterName = "hystrixRequestContextServletFilter",urlPatterns = "/*",asyncSupported = true)public class HystrixRequestContextServletFilter implements Filter { public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException { HystrixRequestContext context = HystrixRequestContext.initializeContext(); try { chain.doFilter(request, response); } finally { context.shutdown(); } } @Override public void init(FilterConfig filterConfig) throws ServletException { } @Override public void destroy() { }}在不同context中的緩存是不共享的，還有這個request內部一個ThreadLocal，所以request只能限于當前線程。
1.3 清除失效緩存
繼承HystrixCommand或HystrixObservableCommand，在更新接口調用完成后，清空緩存。
import com.netflix.hystrix.HystrixCommand;import com.netflix.hystrix.HystrixCommandGroupKey;import com.netflix.hystrix.HystrixCommandKey;import com.szss.demo.orders.vo.UserVO;import org.slf4j.Logger;import org.slf4j.LoggerFactory;import org.springframework.http.HttpEntity;import org.springframework.web.client.RestTemplate;public class UserUpdateCacheCommand extends HystrixCommand<UserVO> { private static final Logger LOGGER = LoggerFactory.getLogger(UserUpdateCacheCommand.class); private static final HystrixCommandKey GETTER_KEY = HystrixCommandKey.Factory.asKey("CommandKey"); private RestTemplate restTemplate; private UserVO user; public UserUpdateCacheCommand(RestTemplate restTemplate, UserVO user) { super(Setter.withGroupKey(HystrixCommandGroupKey.Factory.asKey("userUpdateCacheCommand"))); this.restTemplate = restTemplate; this.user = user; } @Override protected UserVO run() throws Exception { LOGGER.info("thread:" + Thread.currentThread().getName()); HttpEntity<UserVO> u = new HttpEntity<UserVO>(user); UserVO userVO=restTemplate.postForObject("http://users-service/user",u,UserVO.class); UserCacheCommand.flushCache(user.getUsername()); return userVO; }// @Override// protected UserVO getFallback() {// UserVO user = new UserVO();// user.setId(-1L);// user.setUsername("調用失敗");// return user;// } @Override protected String getCacheKey() { return user.getUsername(); }}2 使用@CacheResult、@CacheRemove和@CacheKey標注來實現緩存
2.1 使用@CacheResult實現緩存功能
@CacheResult(cacheKeyMethod = "getCacheKey") @HystrixCommand(commandKey = "findUserById", groupKey = "UserService", threadPoolKey = "userServiceThreadPool") public UserVO findById(Long id) { ResponseEntity<UserVO> user = restTemplate.getForEntity("http://users-service/user?id={id}", UserVO.class, id); return user.getBody(); } public String getCacheKey(Long id) { return String.valueOf(id); }@CacheResult注解中的cacheKeyMethod用來標示緩存key(cacheKey)的生成函數。函數的名稱可任意取名，入參和標注@CacheResult的方法是一致的，返回類型是String。
2.2 使用@CacheResult和@CacheKey實現緩存功能
@CacheResult @HystrixCommand(commandKey = "findUserById", groupKey = "UserService", threadPoolKey = "userServiceThreadPool") public UserVO findById2(@CacheKey("id") Long id) { ResponseEntity<UserVO> user = restTemplate.getForEntity("http://users-service/user?id={id}", UserVO.class, id); return user.getBody(); }標注@HystrixCommand注解的方法，使用@CacheKey標注需要指定的參數作為緩存key。
2.3 使用@CacheRemove清空緩存
@CacheRemove(commandKey = "findUserById") @HystrixCommand(commandKey = "updateUser",groupKey = "UserService",threadPoolKey = "userServiceThreadPool") public void updateUser(@CacheKey("id")UserVO user){ restTemplate.postForObject("http://users-service/user",user,UserVO.class); }@CacheRemove必須指定commandKey，否則程序無法找到緩存位置。
以上就是本文的全部內容，希望對大家的學習有所幫助，也希望大家多多支持VeVb武林網。
新聞熱點
疑難解答
圖片精選
