Eureka的服务注册和服务发现是一起的，服务发现是一个服务，将自己暴露给Eureka的服务注册，这样别人就可以通过Eureka调用服务了。Eureka服务注册本身是也个服务，也可以配置集群。

Eureka的服务注册会在集群中同步服务发现的数据，保证服务高可用。通过Feign,Ribbon等方式可以调用服务注册暴露的服务，Feign和Ribbon都是客户端的LB（负载均衡），实际使用中，可加一层网关Zuul,Zuul网关也可以做集群，在网关之上可以配置服务端的LB。

这里做一个二维码的微服务，来说明Eureka服务发现。

Eureka服务发现，需要引入spring-cloud-starter-eureka

springfox-swagger2是一套在线Rest API文档zxing是用于二维码的生成和解析的

//build.gradlegroup 'org.sauceggplant'version '0.0.1-SNAPSHOT'apply plugin: 'java'apply plugin: 'spring-boot'sourceCompatibility = 1.8targetCompatibility = 1.8repositories {    maven{url 'http://192.168.56.103:8081/repository/zhaozx/'}}dependencies {    compile 'org.springframework.cloud:spring-cloud-starter-config:1.3.1.RELEASE'    compile 'org.springframework.cloud:spring-cloud-starter-eureka:1.3.1.RELEASE'    compile 'org.springframework.boot:spring-boot-actuator:1.5.3.RELEASE'    compile 'io.springfox:springfox-swagger2:2.7.0'    compile 'io.springfox:springfox-swagger-ui:2.7.0'    compile 'com.google.zxing:core:3.3.0'    compile 'com.google.zxing:javase:3.3.0'    testCompile 'org.springframework.boot:spring-boot-starter-test:1.5.3.RELEASE'}buildscript {    repositories {        maven{url 'http://192.168.56.103:8081/repository/zhaozx/'}    }    dependencies {        classpath 'org.springframework.boot:spring-boot-gradle-plugin:1.5.3.RELEASE'    }}jar {    baseName = 'QRCode'    version =  '0.0.1-SNAPSHOT'}

启动类中配置@EnableEurekaClient启动Eureka的服务发现

//QRCodeApplication.javapackage org.sauceggplant.qrcode;import org.springframework.boot.SpringApplication;import org.springframework.boot.autoconfigure.SpringBootApplication;import org.springframework.cloud.netflix.eureka.EnableEurekaClient;@SpringBootApplication@EnableEurekaClientpublic class QRCodeApplication {    public static void main(String[] args) {        SpringApplication.run(QRCodeApplication.class,args);    }}

二维码服务的Controller,与SpringMVC的Controller没什么区别。

@RestController声明一个restful风格的Controller@RequestMapping表示请求的路径@ApiOperation是swagger2的注解，加上注解后可以生成在线swagger文档@RequestParam是请求的参数（@RequestBody请求体）@ResponseBody是返回的内容

//QRCodeController.javapackage org.sauceggplant.qrcode.controller;import com.google.zxing.*;import com.google.zxing.client.j2se.BufferedImageLuminanceSource;import com.google.zxing.common.BitMatrix;import com.google.zxing.client.j2se.MatrixToImageWriter;import com.google.zxing.common.HybridBinarizer;import io.swagger.annotations.ApiOperation;import org.springframework.http.HttpStatus;import org.springframework.http.ResponseEntity;import org.springframework.web.bind.annotation.*;import sun.misc.BASE64Decoder;import sun.misc.BASE64Encoder;import javax.imageio.ImageIO;import javax.servlet.http.HttpServletResponse;import java.awt.image.BufferedImage;import java.io.*;import java.util.HashMap;import java.util.Map;@RestController@RequestMapping("/qrcode")public class QRCodeController {    private static BASE64Decoder decoder = new BASE64Decoder();    private static BASE64Encoder encoder = new BASE64Encoder();    @ApiOperation(value = "获取二维码图片",notes = "获取二维码图片",produces="image/*")    @RequestMapping(value = "/image", method = RequestMethod.GET, produces="image/*")    public void getQRCode(HttpServletResponse response, @RequestParam int width,@RequestParam int height,@RequestParam String format,@RequestParam String content) {        try {            width=width==0?200:width;            height=height==0?200:height;            format=format==null?"png":format;            Map
    
      hints = new HashMap
     
      ();            hints.put(EncodeHintType.CHARACTER_SET, "UTF-8");            BitMatrix bitMatrix = new MultiFormatWriter().encode(content==null?"NULL":content,BarcodeFormat.QR_CODE, width, height, hints);            OutputStream outputStream = (OutputStream)response.getOutputStream();            MatrixToImageWriter.writeToStream(bitMatrix,format,outputStream);            if(outputStream!=null){                outputStream.close();            }        } catch (WriterException e) {            e.printStackTrace();        } catch (IOException e) {            e.printStackTrace();        }    }    @ApiOperation(value = "获取二维码信息",notes = "获取二维码信息")    @RequestMapping(method = RequestMethod.GET)    @ResponseBody    public ResponseEntity
      
        getQRCodeString(@RequestParam int width,@RequestParam int height,@RequestParam String format,@RequestParam String content) {        try {            width=width==0?200:width;            height=height==0?200:height;            format=format==null?"png":format;            Map
       
         hints = new HashMap
        
         ();            hints.put(EncodeHintType.CHARACTER_SET, "UTF-8");            BitMatrix bitMatrix = new MultiFormatWriter().encode(content==null?"NULL":content,BarcodeFormat.QR_CODE, width, height, hints);            ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();            MatrixToImageWriter.writeToStream(bitMatrix,format,byteArrayOutputStream);            String data = encoder.encode(byteArrayOutputStream.toByteArray());            return new ResponseEntity(data,HttpStatus.OK);        } catch (WriterException e) {            e.printStackTrace();            return new ResponseEntity(null, HttpStatus.INTERNAL_SERVER_ERROR);        } catch (IOException e) {            e.printStackTrace();            return new ResponseEntity(null, HttpStatus.INTERNAL_SERVER_ERROR);        }    }    @ApiOperation(value = "获取二维码信息",notes = "获取二维码信息")    @RequestMapping(method = RequestMethod.POST)    @ResponseBody    public ResponseEntity
         
           postQRCode(@RequestBody(required = true) String content) { try { byte[] data = decoder.decodeBuffer(content); BufferedImage image; ByteArrayInputStream in = new ByteArrayInputStream(data); image = ImageIO.read(in); LuminanceSource source = new BufferedImageLuminanceSource(image); Binarizer binarizer = new HybridBinarizer(source); BinaryBitmap binaryBitmap = new BinaryBitmap(binarizer); Map
          
            hints = new HashMap
           
            (); hints.put(DecodeHintType.CHARACTER_SET, "UTF-8"); Result result = new MultiFormatReader().decode(binaryBitmap, hints); return new ResponseEntity(result.getText(), HttpStatus.OK); } catch (IOException e) { e.printStackTrace(); return new ResponseEntity(null, HttpStatus.INTERNAL_SERVER_ERROR); } catch (NotFoundException e) { e.printStackTrace(); return new ResponseEntity(null, HttpStatus.INTERNAL_SERVER_ERROR); } }}
           
          
         
        
       
      
     
    

Swagger2配置

//SwaggerConfiguration.javapackage org.sauceggplant.qrcode.swagger;import org.springframework.context.annotation.Bean;import org.springframework.context.annotation.Configuration;import springfox.documentation.builders.ApiInfoBuilder;import springfox.documentation.builders.PathSelectors;import springfox.documentation.builders.RequestHandlerSelectors;import springfox.documentation.spi.DocumentationType;import springfox.documentation.spring.web.plugins.Docket;import springfox.documentation.swagger2.annotations.EnableSwagger2;@Configuration@EnableSwagger2public class SwaggerConfiguration {    @Bean    public Docket docket(){        return new Docket(DocumentationType.SWAGGER_2)                .apiInfo(new ApiInfoBuilder()                        .title("二维码微服务")                        .description("二维码生成，解析")                        .version("0.0.1-SNAPSHOT")                        .build())                .select()                .apis(RequestHandlerSelectors.basePackage("org.sauceggplant.qrcode.controller"))                .paths(PathSelectors.any())                .build();    }}

application.yml

#application.ymlserver:  port: 8762spring:  application:    name: QRCode#  cloud:#    config:#      server:#        git:#         url: http://192.168.56.101/zhaozx/config-repo/qrcode#  profiles:#    active: deveureka:  client:    serviceUrl:      defaultZone: http://127.0.0.1:8761/eureka/  #Eureka服务注册成地址

bootstrap.yml

#bootstrap.ymleureka:  instance:    lease-renewal-interval-in-seconds: 10     # 心跳时间，即服务续约间隔时间（缺省为30s）    lease-expiration-duration-in-seconds: 60  # 发呆时间，即服务续约到期时间（缺省为90s）  client:    healthcheck:      enabled: true