開篇
本例是在springboot整合h2內存數據庫，實現單元測試與數據庫無關性和使用resttemplate消費spring boot的restful服務兩個示例的基礎上改造而來
在使用resttemplate來消費spring boot的restful服務示例中，我們提到，調用spring boot服務的時候，需要將服務的url寫死或者是寫在配置文件中，但這兩種方式，無論哪一種，一旦ip地址發生了變化，都需要改動程序，并重新部署服務，使用ribbon的時候，可以有效的避免這個問題。
前言：
軟負載均衡的實現方式有兩種，分別是服務端的負載均衡和客戶端的負載均衡
服務端負載均衡：當瀏覽器向后臺發出請求的時候，會首先向反向代理服務器發送請求，反向代理服務器會根據客戶端部署的ip：port映射表以及負載均衡策略，來決定向哪臺服務器發送請求，一般會使用到nginx反向代理技術。
客戶端負載均衡：當瀏覽器向后臺發出請求的時候，客戶端會向服務注冊器(例如：eureka server)，拉取注冊到服務器的可用服務信息，然后根據負載均衡策略，直接命中哪臺服務器發送請求。這整個過程都是在客戶端完成的，并不需要反向代理服務器的參與。
一、啟動eureka server
請參考該例：spring cloud中啟動eureka server
二、啟動微服務，并注冊到eureka server上
spring cloud-將spring boot服務注冊到eureka server上
為了演示負載均衡的效果，再啟動一個為服務，注意需要將端口號改成不一致
三、添加ribbon支持
1、添加ribbon的依賴
2、添加負載均衡支持
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package com.chhliu.springboot.restful; import org.springframework.beans.factory.annotation.autowired; import org.springframework.boot.springapplication; import org.springframework.boot.autoconfigure.springbootapplication; import org.springframework.boot.web.client.resttemplatebuilder; import org.springframework.cloud.client.loadbalancer.loadbalanced; import org.springframework.cloud.netflix.eureka.enableeurekaclient; import org.springframework.context.annotation.bean; import org.springframework.web.client.resttemplate; @springbootapplication@enableeurekaclientpublic class springbootresttemplateapplication { @autowired private resttemplatebuilder builder; @bean @loadbalanced // 添加負載均衡支持，很簡單，只需要在resttemplate上添加@loadbalanced注解，那么resttemplate即具有負載均衡的功能,如果不加@loadbalanced注解的話，會報java.net.unknownhostexception:springboot-h2異常，此時無法通過注冊到eureka server上的服務名來調用服務，因為resttemplate是無法從服務名映射到ip:port的，映射的功能是由loadbalancerclient來實現的。 public resttemplate resttemplate() { return builder.build(); } public static void main(string[] args) { springapplication.run(springbootresttemplateapplication.class, args); } } |
3、修改調用微服務的url
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package com.chhliu.springboot.restful.controller; import org.springframework.beans.factory.annotation.autowired; import org.springframework.web.bind.annotation.getmapping; import org.springframework.web.bind.annotation.pathvariable; import org.springframework.web.bind.annotation.restcontroller; import org.springframework.web.client.resttemplate; import com.chhliu.springboot.restful.vo.user; @restcontrollerpublic class resttemplatecontroller { @autowired private resttemplate resttemplate; @getmapping("/template/{id}") public user findbyid(@pathvariable long id) {// 將原來的ip:port的形式，改成注冊到eureka server上的應用名即可 user u = this.resttemplate.getforobject("http://springboot-h2/user/" + id, user.class); system.out.println(u); return u; } } |
四、查看eureka server狀態
五，在瀏覽器中，多次刷新http://localhost:7904/template/2地址
六、測試結果
7900端口服務：
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hibernate: select user0_.id as id1_0_0_, user0_.age as age2_0_0_, user0_.balance as balance3_0_0_, user0_.name as name4_0_0_, user0_.username as username5_0_0_ from user user0_ where user0_.id=? hibernate: select user0_.id as id1_0_0_, user0_.age as age2_0_0_, user0_.balance as balance3_0_0_, user0_.name as name4_0_0_, user0_.username as username5_0_0_ from user user0_ where user0_.id=? hibernate: select user0_.id as id1_0_0_, user0_.age as age2_0_0_, user0_.balance as balance3_0_0_, user0_.name as name4_0_0_, user0_.username as username5_0_0_ from user user0_ where user0_.id=? hibernate: select user0_.id as id1_0_0_, user0_.age as age2_0_0_, user0_.balance as balance3_0_0_, user0_.name as name4_0_0_, user0_.username as username5_0_0_ from user user0_ where user0_.id=? |
7901端口服務：
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hibernate: select user0_.id as id1_0_0_, user0_.age as age2_0_0_, user0_.balance as balance3_0_0_, user0_.name as name4_0_0_, user0_.username as username5_0_0_ from user user0_ where user0_.id=? hibernate: select user0_.id as id1_0_0_, user0_.age as age2_0_0_, user0_.balance as balance3_0_0_, user0_.name as name4_0_0_, user0_.username as username5_0_0_ from user user0_ where user0_.id=? hibernate: select user0_.id as id1_0_0_, user0_.age as age2_0_0_, user0_.balance as balance3_0_0_, user0_.name as name4_0_0_, user0_.username as username5_0_0_ from user user0_ where user0_.id=? hibernate: select user0_.id as id1_0_0_, user0_.age as age2_0_0_, user0_.balance as balance3_0_0_, user0_.name as name4_0_0_, user0_.username as username5_0_0_ from user user0_ where user0_.id=? hibernate: select user0_.id as id1_0_0_, user0_.age as age2_0_0_, user0_.balance as balance3_0_0_, user0_.name as name4_0_0_, user0_.username as username5_0_0_ from user user0_ where user0_.id=? |
7904端口服務：
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user [id=2, username=user2, name=李四, age=20, balance=100.00] 2017-01-23 09:58:05.682 info 7436 --- [erlistupdater-0] c.netflix.config.chaineddynamicproperty : flipping property: springboot-h2.ribbon.activeconnectionslimit to use next property: niws.loadbalancer.availabilityfilteringrule.activeconnectionslimit = 2147483647user [id=2, username=user2, name=李四, age=20, balance=100.00] user [id=2, username=user2, name=李四, age=20, balance=100.00] user [id=2, username=user2, name=李四, age=20, balance=100.00] user [id=2, username=user2, name=李四, age=20, balance=100.00] user [id=2, username=user2, name=李四, age=20, balance=100.00] user [id=2, username=user2, name=李四, age=20, balance=100.00] user [id=2, username=user2, name=李四, age=20, balance=100.00] user [id=2, username=user2, name=李四, age=20, balance=100.00] |
從上面的測試結果可以看出，總共調了7904端口服務9次，其中7904端口服務調7900端口服務4次，調7901端口5次，剛好是9次
經過上面的幾個步驟，就基本使用ribbon實現了客戶端負載均衡的功能
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服務器之家。
原文鏈接：http://blog.csdn.net/liuchuanhong1/article/details/54691566
