使用RestTemplate客户端调用微服务发布的Restful接口
记录：393
场景：在Spring Cloud微服务架构中，使用nacos注册和配置微服务，使用RestTemplate客户端调用微服务发布的Restful接口。
版本：JDK 1.8,SpringBoot 2.6.3,springCloud 2021.0.1,Nacos 2.1.1。
3.1初始化准备
3.1.1创建Maven工程
使用IntelliJ IDEA创建Maven工程。
(1)微服务名称
名称：hub-example-303-resttemplate
(2)微服务groupId和artifactId
groupId: com.hub
artifactId: hub-example-303-resttemplate
(3)微服务核心模块版本
spring-boot 2.6.3
spring-cloud 2021.0.1
spring-cloud-alibaba 2021.0.1.03.1.2准备nacos
Nacos版本：Nacos 2.1.1。
(1)启动和登录nacos
启动命令：sh startup.sh -m standalone
地址：http://127.0.0.1:8848/nacos
用户名/口令：nacos/nacos
(2)创建命名空间
命名空间ID：aa3eebb6-daa2-4db8-9a29-03dd8a17db15
命名空间名：hub
3.2修改pom.xml
修改pom.xml，引入项目依赖Jar和管理Jar包。
3.2.1修改pom.xml文件
(1)RestTemplate依赖
org.springframework.web.client.RestTemplate，在spring-web-5.3.15.jar中。引入以下依赖就自动导入了。
<dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-web</artifactId>
</dependency>(2)RestTemplate依赖
使用RestTemplate调用微服务时，且微服务注册在Nacos时，需引入客户端负载均衡包。
<dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-starter-loadbalancer</artifactId>
</dependency>3.2.2全量pom.xml文件
全量pom.xml文件请参考附录：3.10.1全量pom.xml文件
3.3创建bootstrap.yml文件和配置nacos
3.3.1创建bootstrap.yml
server:port: 18303servlet:context-path: /hub-303-rest
spring:application:name: hub-example-303-resttemplatecloud:nacos:discovery:server-addr: 127.0.0.1:18848username: nacospassword: nacosnamespace: aa3eebb6-daa2-4db8-9a29-03dd8a17db15group: DEFAULT_GROUPconfig:server-addr: 127.0.0.1:18848username: nacospassword: nacosnamespace: aa3eebb6-daa2-4db8-9a29-03dd8a17db15group: DEFAULT_GROUPfile-extension: yamlshared-configs:- dataId: hub-example01-config.ymlgroup: DEFAULT_GROUPrefresh: true3.4创建启动类
3.4.1创建包
com.hub.example.domain：微服务使用到的DTO等实体类。
com.hub.example.controller：Controller类，发布Restful接口。
com.hub.example.config：配置类。
3.4.2启动类
包名：com.hub.example。
启动类：HubExampleFeignApplication。
(1)内容
@SpringBootApplication
@ComponentScan(basePackages = "com.hub.example.*")
@EnableDiscoveryClient
public class HubExampleRestApplication {public static void main(String[] args) {SpringApplication.run(HubExampleRestApplication.class, args);}
}(2)解析
@SpringBootApplication，SpringBoot标记启动类的注解。
@ComponentScan，扫描指定的包，将组件加载到IOC容器中。
@EnableDiscoveryClient，开启服务发现功能。
3.5创建配置
3.5.1配置类
@Configuration
public class RestTemplateConfiguration {@Bean(name = "msRestTemplate")@Primary@LoadBalancedpublic RestTemplate msRestTemplate() {return new RestTemplate();}
}3.5.2解析
使用RestTemplate调用注册到Nacos的微服务时，需加上@LoadBalanced注解，启动客户端负载均衡，否则会报错。
3.6编写Controller代码
3.6.1Controller代码
@RestController
@RequestMapping("/hub/example/city")
@RefreshScope
@Slf4j
public class CityController {@Qualifier("msRestTemplate")@Autowiredprivate RestTemplate msRestTemplate;@PostMapping("/queryCityByCityId")public ResultObj<CityDTO> queryCityByCityId(String cityId) {// 1.组装请求头HttpHeaders httpHeaders = new HttpHeaders();httpHeaders.set("cityNo","0517");httpHeaders.setContentType(MediaType.APPLICATION_JSON);// 2.组装请求实体HttpEntity<String> httpEntity = new HttpEntity<>(cityId,httpHeaders);String url="http://hub-example-301-nacos/hub-301-nacos/hub/example/city/queryCityByCityId";ResponseEntity<String> responseEntity = msRestTemplate.postForEntity(url,httpEntity,String.class,new Object[0]);// 3.解析应答实体String result = responseEntity.getBody();ResultObj resultObj= JSONUtil.toBean(result,ResultObj.class);CityDTO cityDTO =JSONUtil.toBean((JSONObject) resultObj.getData(),CityDTO.class);return ResultObj.data(200, cityDTO, "执行成功");}@PostMapping("/queryCityByCity")public ResultObj<CityDTO> queryCityByCity(@RequestBody CityReqDTO cityReqDTO) {// 1.组装请求头HttpHeaders httpHeaders = new HttpHeaders();httpHeaders.set("cityNo","0517");httpHeaders.setContentType(MediaType.APPLICATION_JSON);// 2.组装请求实体HttpEntity<CityReqDTO> httpEntity = new HttpEntity<>(cityReqDTO,httpHeaders);String url="http://hub-example-301-nacos/hub-301-nacos/hub/example/city/queryCityByCity";ResponseEntity<CityDTO> responseEntity = msRestTemplate.postForEntity(url,httpEntity,CityDTO.class,new Object[0]);// 3.解析应答实体CityDTO cityDTO = responseEntity.getBody();return ResultObj.data(200, cityDTO, "执行成功");}
}3.6.2解析RestTemplate调用远程微服务
(1)调用方式
String url="http://hub-example-301-nacos/hub-301-nacos/hub/example/city/queryCityByCity";
ResponseEntity<CityDTO> responseEntity = msRestTemplate.postForEntity(url,httpEntity,CityDTO.class,new Object[0]);(2)解析
在url中，hub-example-301-nacos，是目标微服务的名称，即微服务注册在Nacos中名称。
/hub-301-nacos，是目标微服务配置的server.servlet.context-path属性。
/hub/example/city/queryCityByCity，是目标微服务的Controller路径：@RequestMapping("/hub/example/city")；和方法上的请求路径：@PostMapping("/queryCityByCity")。
3.6.3解析请求实体和响应实体
org.springframework.web.client.RestTemplate，操作http请求的客户端。
org.springframework.util.MultiValueMap，存储请求头的key、value键值对。
org.springframework.http.HttpHeaders，http请求头。
org.springframework.http.HttpEntity，http请求实体。
org.springframework.http.ResponseEntity，http响应实体。
在HttpHeaders中的核心属性：
final MultiValueMap<String, String> headers;在HttpEntity中的核心属性：
private final HttpHeaders headers;
private final T body;在HttpEntity中的核心属性：
ResponseEntity中的核心属性（其中headers和body从HttpEntity中继承）：
private final Object status;
private final HttpHeaders headers;
private final T body;3.6.4使用RestTemplate传递请求头信息
使用RestTemplate传递请求头信息。
HttpHeaders httpHeaders = new HttpHeaders();
httpHeaders.set("cityNo","0517");
httpHeaders.setContentType(MediaType.APPLICATION_JSON);3.7支撑对象
3.7.1CityDTO
@Data
public class CityDTO implements Serializable {private Long cityId;private String cityName;private Double landArea;private Long population;private Double gross;private String cityDescribe;private String dataYear;@JsonFormat(pattern = "yyyy-MM-dd HH:mm:ss")private Date updateTime;
}3.7.2ResultObj
@Data
public class ResultObj<T> implements Serializable {private int code;private boolean success;private String msg;private T data;private ResultObj(int code, T data, String msg) {this.code = code;this.data = data;
this.msg = msg;
this.success = code == 200;}public static <T> ResultObj<T> data(int code, T data, String msg) {return new ResultObj<>(code, data, msg);}
}3.7.3CityReqDTO
@Data
public class CityReqDTO {private Long cityId;private String cityName;
}3.8目标微服务信息
使用RestTemplate调用的远程微服务信息。
3.8.1目标微服名称
微服务名：hub-example-301-nacos
3.8.2目标微服Controller
@RestController
@RequestMapping("/hub/example/city")
@RefreshScope
@Slf4j
public class CityController {@Autowiredprivate HttpServletRequest request;@PostMapping("/queryCityByCityId")public ResultObj<CityDTO> queryCityByCityId(String cityId) {log.info("cityNo = " + request.getHeader("cityNo"));CityDTO cityDTO = new CityDTO();cityDTO.setCityId(cityId != null ? Long.parseLong(cityId) : 1L);cityDTO.setCityName(cityName);cityDTO.setUpdateTime(new Date());return ResultObj.data(200, cityDTO, "执行成功");}@PostMapping("/queryCityByCity")public CityDTO queryCityByCity(@RequestBody CityReqDTO cityReqDTO) {CityDTO cityDTO = new CityDTO();cityDTO.setCityId(cityReqDTO.getCityId());cityDTO.setCityName(cityReqDTO.getCityName());cityDTO.setCityDescribe(cityReqDTO.getCityName() + "是一个互联网城市.");cityDTO.setUpdateTime(new Date());return cityDTO;}
}3.9使用Postman工具测试
使用Postman工具测试。
测试地址：http://127.0.0.1:18302/hub-302-feign/hub/example/city/queryCityByCity
测试入参：
{"cityId":"20230326","cityName":"杭州"
}返回结果：
{"code": 200,"success": true,"msg": "执行成功","data": {"cityId": 20230326,"cityName": "杭州","landArea": null,"population": null,"gross": null,"cityDescribe": "杭州是一个互联网城市.","dataYear": null,"updateTime": "2023-03-26 21:16:55"}
}3.10附录
3.10.1全量pom.xml文件
<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"><modelVersion>4.0.0</modelVersion><groupId>com.hub</groupId><artifactId>hub-example-303-resttemplate</artifactId><version>1.0-SNAPSHOT</version><parent><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-parent</artifactId><version>2.6.3</version></parent><description>应用RestTemplate调用微服务</description><packaging>jar</packaging><properties><maven.compiler.source>1.8</maven.compiler.source><maven.compiler.target>1.8</maven.compiler.target><project.build.sourceEncoding>UTF-8</project.build.sourceEncoding><project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding><spring.boot.maven.plugin.version>2.6.3</spring.boot.maven.plugin.version><spring.boot.version>2.6.3</spring.boot.version><spring.cloud.version>2021.0.1</spring.cloud.version><spring.cloud.alibaba.version>2021.0.1.0</spring.cloud.alibaba.version><nacos.client.version>2.1.1</nacos.client.version><lombok.version>1.18.24</lombok.version><guava.version>30.1-jre</guava.version><hutool.version>5.8.12</hutool.version></properties><dependencyManagement><dependencies><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-parent</artifactId><version>${spring.boot.version}</version><type>pom</type><scope>import</scope></dependency><dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-dependencies</artifactId><version>${spring.cloud.version}</version><type>pom</type><scope>import</scope></dependency><dependency><groupId>com.alibaba.cloud</groupId><artifactId>spring-cloud-alibaba-dependencies</artifactId><version>${spring.cloud.alibaba.version}</version><type>pom</type><scope>import</scope></dependency></dependencies></dependencyManagement><dependencies><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter</artifactId></dependency><dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-web</artifactId></dependency><dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-starter-bootstrap</artifactId></dependency><!--nacos注册中心--><dependency><groupId>com.alibaba.cloud</groupId><artifactId>spring-cloud-starter-alibaba-nacos-discovery</artifactId><exclusions><exclusion><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-starter-netflix-ribbon</artifactId></exclusion></exclusions></dependency><dependency><groupId>org.springframework.cloud</groupId><artifactId>spring-cloud-starter-loadbalancer</artifactId></dependency><!--nacos配置中心--><dependency><groupId>com.alibaba.cloud</groupId><artifactId>spring-cloud-starter-alibaba-nacos-config</artifactId><exclusions><exclusion><groupId>com.alibaba.nacos</groupId><artifactId>nacos-client</artifactId></exclusion></exclusions></dependency><dependency><groupId>com.alibaba.nacos</groupId><artifactId>nacos-client</artifactId><version>${nacos.client.version}</version></dependency><dependency><groupId>org.projectlombok</groupId><artifactId>lombok</artifactId><version>${lombok.version}</version></dependency><dependency><groupId>com.google.guava</groupId><artifactId>guava</artifactId><version>${guava.version}</version></dependency><dependency><groupId>cn.hutool</groupId><artifactId>hutool-all</artifactId><version>${hutool.version}</version></dependency></dependencies><build><finalName>${project.artifactId}</finalName><plugins><plugin><groupId>org.springframework.boot</groupId><artifactId>spring-boot-maven-plugin</artifactId><version>${spring.boot.maven.plugin.version}</version><configuration><fork>true</fork><addResources>true</addResources></configuration><executions><execution><goals><goal>repackage</goal></goals></execution></executions></plugin></plugins></build>
</project>以上，感谢。
2023年3月26日