微服务技术系列教程（21） - SpringCloud- 负载均衡器Ribbon

@RestController
public class ServiceBController {
    @Autowired
    private RestTemplate restTemplate;
    @Autowired
    private DiscoveryClient discoveryClient;
    private int requestCount = 1;
    @RequestMapping("/discoveryClient")
    public String discoveryClient() {
        String serviceUrl = getServiceUrl() + "/getMember";
        return "请求地址为 -> " + serviceUrl;
    }
    @RequestMapping("/getServiceUrl")
    private String getServiceUrl() {
        List<ServiceInstance> instances = discoveryClient.getInstances("app-service-a");
        if (instances == null || instances.size() == 0) {
            return null;
        }
        int size = instances.size();
        int index = requestCount % size;
        requestCount++;
        return instances.get(index).getUri().toString();
    }
}

public interface HttpMessageConverter<T> {
        //指示此转换器是否可以读取给定的类。
    boolean canRead(Class<?> clazz, @Nullable MediaType mediaType);
        //指示此转换器是否可以写给定的类。
    boolean canWrite(Class<?> clazz, @Nullable MediaType mediaType);
        //返回List<MediaType>
    List<MediaType> getSupportedMediaTypes();
        //读取一个inputMessage
    T read(Class<? extends T> clazz, HttpInputMessage inputMessage)
            throws IOException, HttpMessageNotReadableException;
        //往output message写一个Object
    void write(T t, @Nullable MediaType contentType, HttpOutputMessage outputMessage)
            throws IOException, HttpMessageNotWritableException;
}

public class Notice {
    private int status;
    private Object msg;
    private List<DataBean> data;
}
public  class DataBean {
  private int noticeId;
  private String noticeTitle;
  private Object noticeImg;
  private long noticeCreateTime;
  private long noticeUpdateTime;
  private String noticeContent;
}

@Test
public void rtGetEntity(){
        RestTemplate restTemplate = new RestTemplate();
        ResponseEntity<Notice> entity = restTemplate.getForEntity("http://fantj.top/notice/list/1/5"
                , Notice.class);
        HttpStatus statusCode = entity.getStatusCode();
        System.out.println("statusCode.is2xxSuccessful()"+statusCode.is2xxSuccessful());
        Notice body = entity.getBody();
        System.out.println("entity.getBody()"+body);
        ResponseEntity.BodyBuilder status = ResponseEntity.status(statusCode);
        status.contentLength(100);
        status.body("我在这里添加一句话");
        ResponseEntity<Class<Notice>> body1 = status.body(Notice.class);
        Class<Notice> body2 = body1.getBody();
        System.out.println("body1.toString()"+body1.toString());
    }
statusCode.is2xxSuccessful()true
entity.getBody()Notice{status=200, msg=null, data=[DataBean{noticeId=21, noticeTitle='aaa', ...
body1.toString()<200 OK,class com.waylau.spring.cloud.weather.pojo.Notice,{Content-Length=[100]}>

/**
* 带参数与不带参的get请求
*/
@Test
public void restTemplateGetTest(){
   RestTemplate restTemplate = new RestTemplate();
   Notice notice = restTemplate.getForObject("http://xxx.top/notice/list/1/5", Notice.class);
   //Notice notice = restTemplate.getForObject("http://fantj.top/notice/list/{1}/{2}" , Notice.class,1,5);
   System.out.println(notice);
}

@Test
public void rtPostObject(){
    RestTemplate restTemplate = new RestTemplate();
    String url = "http://47.xxx.xxx.96/register/checkEmail";
    HttpHeaders headers = new HttpHeaders();
    headers.setContentType(MediaType.APPLICATION_FORM_URLENCODED);
    MultiValueMap<String, String> map= new LinkedMultiValueMap<>();
    map.add("email", "xxx@qq.com");
    HttpEntity<MultiValueMap<String, String>> request = new HttpEntity<>(map, headers);
    ResponseEntity<String> response = restTemplate.postForEntity( url, request , String.class );
    System.out.println(response.getBody());
}

@SpringBootApplication
@EnableEurekaClient
public class App {
    public static void main(String[] args) {
        SpringApplication.run(App.class, args);
    }
    @Bean
    //@LoadBalanced//@LoadBalanced就能让这个RestTemplate在请求时拥有客户端负载均衡的能力（增加@LoadBalanced，就不能使用127.0.0.1,只能使用应用名)
    RestTemplate restTemplate() {
        return new RestTemplate();
    }
}