Spring Cloud Ribbon：负载均衡的服务调用

我会带着你远行 2024-04-22 19:03 57阅读 0赞

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## Spring Cloud Ribbon：负载均衡的服务调用 ##

> Spring Cloud Ribbon 是Spring Cloud Netflix 子项目的核心组件之一，主要给服务间调用及API网关转发提供负载均衡的功能，本文将对其用法进行详细介绍

### Ribbon简介 ###

> Ribbon 是 Netflix 公司开源的一个用于负载均衡的客户端组件，它是 Spring Cloud 生态系统中的一部分；Ribbon 的主要目标是提供一种简单且可定制的负载均衡解决方案，用于在微服务架构中实现服务之间的调用和负载均衡

### RestTemplate ###

> RestTemplate 是 Spring Framework 提供的一个用于进行 HTTP 请求的客户端工具类；简化了在 Java 应用程序中进行 HTTP 通信的过程，并提供了丰富的方法来处理请求和响应  
>   
>   
> RestTemplate 提供了各种方法来执行不同类型的 HTTP 请求，包括 GET、POST、PUT、DELETE 等；支持发送请求并接收响应的各种数据类型，如字符串、字节数组、JSON 对象等

#### GET请求方法 ####

<T> T getForObject(String url, Class<T> responseType, Object... uriVariables);
    
    <T> T getForObject(String url, Class<T> responseType, Map<String, ?> uriVariables);
    
    <T> T getForObject(URI url, Class<T> responseType);
    
    <T> ResponseEntity<T> getForEntity(String url, Class<T> responseType, Object... uriVariables);
    
    <T> ResponseEntity<T> getForEntity(String url, Class<T> responseType, Map<String, ?> uriVariables);
    
    <T> ResponseEntity<T> getForEntity(URI var1, Class<T> responseType);

#### POST请求方法 ####

<T> T postForObject(String url, @Nullable Object request, Class<T> responseType, Object... uriVariables);
    
    <T> T postForObject(String url, @Nullable Object request, Class<T> responseType, Map<String, ?> uriVariables);
    
    <T> T postForObject(URI url, @Nullable Object request, Class<T> responseType);
    
    <T> ResponseEntity<T> postForEntity(String url, @Nullable Object request, Class<T> responseType, Object... uriVariables);
    
    <T> ResponseEntity<T> postForEntity(String url, @Nullable Object request, Class<T> responseType, Map<String, ?> uriVariables);
    
    <T> ResponseEntity<T> postForEntity(URI url, @Nullable Object request, Class<T> responseType);

#### PUT请求方法 ####

void put(String url, @Nullable Object request, Object... uriVariables);
    
    void put(String url, @Nullable Object request, Map<String, ?> uriVariables);
    
    void put(URI url, @Nullable Object request);

#### DELETE请求方法 ####

void delete(String url, Object... uriVariables);
    
    void delete(String url, Map<String, ?> uriVariables);
    
    void delete(URI url);

### 创建user-service模块 ###

> 创建user-service，用于给Ribbon提供服务调用

>  *  添加依赖
> 
>     <dependency>
>         <groupId>org.springframework.cloud</groupId>
>         <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
>     </dependency>
>     <dependency>
>         <groupId>org.springframework.boot</groupId>
>         <artifactId>spring-boot-starter-web</artifactId>
>     </dependency>
> 
>  *  添加application.yml配置
> 
>     server:
>       port: 8201
>     spring:
>       application:
>         name: user-service
>     eureka:
>       client:
>         register-with-eureka: true
>         fetch-registry: true
>         service-url:
>           defaultZone: http://localhost:8001/eureka/
> 
>  *  添加UserController用于提供调用接口
> 
>     /**
>      * Created by macro on 2019/8/29.
>      */
>     @RestController
>     @RequestMapping("/user")
>     public class UserController {
>          
>     
>         private Logger LOGGER = LoggerFactory.getLogger(this.getClass());
>     
>         @Autowired
>         private UserService userService;
>     
>         @PostMapping("/create")
>         public CommonResult create(@RequestBody User user) {
>          
>             userService.create(user);
>             return new CommonResult("操作成功", 200);
>         }
>     
>         @GetMapping("/{id}")
>         public CommonResult<User> getUser(@PathVariable Long id) {
>          
>             User user = userService.getUser(id);
>             LOGGER.info("根据id获取用户信息，用户名称为：{}",user.getUsername());
>             return new CommonResult<>(user);
>         }
>     
>         @GetMapping("/getUserByIds")
>         public CommonResult<List<User>> getUserByIds(@RequestParam List<Long> ids) {
>          
>             List<User> userList= userService.getUserByIds(ids);
>             LOGGER.info("根据ids获取用户信息，用户列表为：{}",userList);
>             return new CommonResult<>(userList);
>         }
>     
>         @GetMapping("/getByUsername")
>         public CommonResult<User> getByUsername(@RequestParam String username) {
>          
>             User user = userService.getByUsername(username);
>             return new CommonResult<>(user);
>         }
>     
>         @PostMapping("/update")
>         public CommonResult update(@RequestBody User user) {
>          
>             userService.update(user);
>             return new CommonResult("操作成功", 200);
>         }
>     
>         @PostMapping("/delete/{id}")
>         public CommonResult delete(@PathVariable Long id) {
>          
>             userService.delete(id);
>             return new CommonResult("操作成功", 200);
>         }
>     }

### 创建ribbon-service模块 ###

> 创建ribbon-service模块调用user-service模块演示负载均衡的服务调用

>  *  添加依赖
> 
>     <dependency>
>         <groupId>org.springframework.boot</groupId>
>         <artifactId>spring-boot-starter-web</artifactId>
>     </dependency>
>     <dependency>
>         <groupId>org.springframework.cloud</groupId>
>         <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
>     </dependency>
>     <dependency>
>         <groupId>org.springframework.cloud</groupId>
>         <artifactId>spring-cloud-starter-netflix-ribbon</artifactId>
>     </dependency>
> 
>  *  配置application.yml
> 
> 配置端口、注册中心地址及user-service的调用路径
> 
>     server:
>       port: 8301
>     spring:
>       application:
>         name: ribbon-service
>     eureka:
>       client:
>         register-with-eureka: true
>         fetch-registry: true
>         service-url:
>           defaultZone: http://localhost:8001/eureka/
>     service-url:
>       user-service: http://user-service

### 负载均衡 ###

>  *  @LoadBalanced注解赋予RestTemplate负载均衡的能力
> 
>     /**
>      * Created by macro on 2019/8/29.
>      */
>     @Configuration
>     public class RibbonConfig {
>          
>     
>         @Bean
>         @LoadBalanced
>         public RestTemplate restTemplate(){
>          
>             return new RestTemplate();
>         }
>     }
> 
>  *  添加UserRibbonController类
> 
> 注入RestTemplate，使用其调用user-service中提供的相关接口
> 
>     /**
>      * Created by macro on 2019/8/29.
>      */
>     @RestController
>     @RequestMapping("/user")
>     public class UserRibbonController {
>          
>         @Autowired
>         private RestTemplate restTemplate;
>         @Value("${service-url.user-service}")
>         private String userServiceUrl;
>     
>         @GetMapping("/{id}")
>         public CommonResult getUser(@PathVariable Long id) {
>          
>             return restTemplate.getForObject(userServiceUrl + "/user/{1}", CommonResult.class, id);
>         }
>     
>         @GetMapping("/getByUsername")
>         public CommonResult getByUsername(@RequestParam String username) {
>          
>             return restTemplate.getForObject(userServiceUrl + "/user/getByUsername?username={1}", CommonResult.class, username);
>         }
>     
>         @GetMapping("/getEntityByUsername")
>         public CommonResult getEntityByUsername(@RequestParam String username) {
>          
>             ResponseEntity<CommonResult> entity = restTemplate.getForEntity(userServiceUrl + "/user/getByUsername?username={1}", CommonResult.class, username);
>             if (entity.getStatusCode().is2xxSuccessful()) {
>          
>                 return entity.getBody();
>             } else {
>          
>                 return new CommonResult("操作失败", 500);
>             }
>         }
>     
>         @PostMapping("/create")
>         public CommonResult create(@RequestBody User user) {
>          
>             return restTemplate.postForObject(userServiceUrl + "/user/create", user, CommonResult.class);
>         }
>     
>         @PostMapping("/update")
>         public CommonResult update(@RequestBody User user) {
>          
>             return restTemplate.postForObject(userServiceUrl + "/user/update", user, CommonResult.class);
>         }
>     
>         @PostMapping("/delete/{id}")
>         public CommonResult delete(@PathVariable Long id) {
>          
>             return restTemplate.postForObject(userServiceUrl + "/user/delete/{1}", null, CommonResult.class, id);
>         }
>     }

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