- 1.减少重复的请求数，降低依赖服务的返回数据始终保持一致。
- 2.==在同一个用户请求的上下文中，相同依赖服务的返回数据始终保持一致==。
- 3.请求缓存在run()和construct()执行之前生效，所以可以有效减少不必要的线程开销。
1 通过hystrixcommand类实现
1.1 开启缓存功能
继承hystrixcommand或hystrixobservablecommand，覆盖getcachekey()方法，指定缓存的key，开启缓存配置。
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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("调用失败"); 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
通过servlet的filter配置hystrix的上下文。
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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中的缓存是不共享的，还有这个request内部一个threadlocal，所以request只能限于当前线程。
1.3 清除失效缓存
继承hystrixcommand或hystrixobservablecommand，在更新接口调用完成后，清空缓存。
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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("调用失败");// return user;// } @override protected string getcachekey() { return user.getusername(); }} |
2 使用@cacheresult、@cacheremove和@cachekey标注来实现缓存
2.1 使用@cacheresult实现缓存功能
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@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用来标示缓存key(cachekey)的生成函数。函数的名称可任意取名，入参和标注@cacheresult的方法是一致的，返回类型是string。
2.2 使用@cacheresult和@cachekey实现缓存功能
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@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();} |
标注@hystrixcommand注解的方法，使用@cachekey标注需要指定的参数作为缓存key。
2.3 使用@cacheremove清空缓存
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@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必须指定commandkey，否则程序无法找到缓存位置。
以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持服务器之家。
原文链接：https://blog.csdn.net/zhuchuangang/article/details/74566185
