使用RestTemplate客户端调用微服务发布的Restful接口

我就是我 2024-04-23 02:55 76阅读 0赞

**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 2021.0.1.0

**3.1.2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][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: 18303
      servlet:
        context-path: /hub-303-rest
    spring:
      application:
        name: hub-example-303-resttemplate
      cloud:
        nacos:
          discovery:
            server-addr: 127.0.0.1:18848
            username: nacos
            password: nacos
            namespace: aa3eebb6-daa2-4db8-9a29-03dd8a17db15
            group: DEFAULT_GROUP
          config:
            server-addr: 127.0.0.1:18848
            username: nacos
            password: nacos
            namespace: aa3eebb6-daa2-4db8-9a29-03dd8a17db15
            group: DEFAULT_GROUP
            file-extension: yaml
            shared-configs:
              - dataId: hub-example01-config.yml
                group: DEFAULT_GROUP
                refresh: true

**3.4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
      @LoadBalanced
      public 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")
      @Autowired
      private 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 {
      @Autowired
      private 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][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>
          
          <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>
          
          <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

[http_127.0.0.1_8848_nacos]: http://127.0.0.1:8848/nacos
[http_127.0.0.1_18302_hub-302-feign_hub_example_city_queryCityByCity]: http://127.0.0.1:18302/hub-302-feign/hub/example/city/queryCityByCity