10、RestTemplate方式实现远程调用Client

一、JSONObject类详解：

JSONobject是FastJson提供的对象，在API中是用一个私有的常量map进行封装的，实际就是一个map，只不过 FastJson对其进行了封装，添加了很多方便快捷的属性方法。

添加相关依赖：

<dependency>
    <groupId>com.alibaba</groupId>
    <artifactId>fastjson</artifactId>
    <version>1.2.79</version>
</dependency>

1、将Java对象转化成String：

2、将String类型转json对象，取JSON中KEY对应的VALUE：

3、将String对象转化为List类型：

public class JSONObjectDemo {

    public static void main(String[] args) {
        //创建对象
        List<JsonObjectVO> list = new ArrayList<>();
        //对象1
        JsonObjectVO vo1 = new JsonObjectVO();
        vo1.setUuid(UUID.randomUUID().toString());
        vo1.setName("1");
        //对象2
        JsonObjectVO vo2 = new JsonObjectVO();
        vo2.setUuid(UUID.randomUUID().toString());
        vo2.setName("2");
        list.add(vo1);
        list.add(vo2);
        ResponseVO responseVO = ResponseVO.builder()
                .uuid(UUID.randomUUID().toString())
                .list(list)
                .build();
        /**
         * 1、java对象转化成String
         * toPrint:{"list":[{"name":"1","uuid":"b73bb9e8-f7a3-4dcf-8d8d-51313c7f5fd7"},{"name":"2","uuid":"ef109d35-cd07-45cd-9b45-791b205c878f"}],"uuid":"dbc3b9c6-2360-4b83-9d15-b88fe7980f27"}
         * */
        String str = JSONObject.toJSONString(responseVO);
        /**
         * 2、String类型转json对象，取JSON中的KEY
         * toPrint:[{"name":"1","uuid":"b73bb9e8-f7a3-4dcf-8d8d-51313c7f5fd7"},{"name":"2","uuid":"ef109d35-cd07-45cd-9b45-791b205c878f"}]
         * */
        Object data = JSONObject.parseObject(str).get("list");
        /**
         * 3、将String对象转化为List类型
         * toPrint:[JsonObjectVO(uuid=aebd390d-f543-4410-9c3a-98f2cb057757, name=1), JsonObjectVO(uuid=d170bb12-7570-47dd-8f2d-9ec2df5573c5, name=2)]
         * */
        List<JsonObjectVO> aList = JSONObject.parseArray(JSONObject.toJSONString(data),JsonObjectVO.class);

        System.out.println(str);
        System.out.println(data);
        System.out.println(aList);
    }
}

二、RestTemplate详解：

RestTemplate是由Spring框架提供的一个可调用REST服务的类，它简化了与HTTP服务的通信方式，统一了RESTFUL的标准，封装了HTTP连接。相较于之前常用的HttpClient，RestTemplate是一种更为优雅的调用RESTFul服务的方式。

1、添加依赖：

<!--JSONObject插件-->
<dependency>
    <groupId>com.alibaba</groupId>
    <artifactId>fastjson</artifactId>
    <version>1.2.79</version>
</dependency>
<dependency>
    <groupId>org.apache.commons</groupId>
    <artifactId>commons-lang3</artifactId>
    <version>3.1</version>
</dependency>

2、声明RestTemplate配置类：

import org.springframework.context.annotation.Bean;
import org.springframework.context.annotation.Configuration;
import org.springframework.web.client.RestTemplate;

@Configuration
public class RestTemplateConfig {
    @Bean
    public RestTemplate restTemplate(){
        return new RestTemplate();
    }

}

3、自定义远程调用Client通用工具类（重）：

import com.alibaba.fastjson.JSONObject;
import lombok.extern.slf4j.Slf4j;
import org.apache.commons.lang3.StringUtils;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.HttpEntity;
import org.springframework.http.HttpMethod;
import org.springframework.http.ResponseEntity;
import org.springframework.stereotype.Component;
import org.springframework.util.LinkedMultiValueMap;
import org.springframework.util.MultiValueMap;
import org.springframework.web.client.RestTemplate;

import java.util.HashSet;
import java.util.Map;
import java.util.Optional;

@Slf4j
@Component
public class HttpClientUtil {
    @Autowired
    private RestTemplate restTemplate;

    /**
     * @Param basisUrl:根地址(不带请求参数)
     * @Param param:请求参数
     * @Param method:请求方式(HttpMethod.GET、HttpMethod.POST......)
     * @Param authToken:请求令牌
     */
    public String getUrlResponse(String basisUrl, Map<Object, Object> param, HttpMethod method, String authToken) {
        MultiValueMap heards = new LinkedMultiValueMap();
        if (StringUtils.isNotBlank(authToken)) {
            heards.add("Authorization", authToken);
        }
        //合成请求地址
        String url = buildUrl(basisUrl, param);
        log.info("请求地址为：" + url);
        HttpEntity<Object> httpEntity = new HttpEntity<>(heards);
        ResponseEntity<Object> response = restTemplate.exchange(url, method, httpEntity, Object.class, param);
        String jsonString = JSONObject.toJSONString(response.getBody());
        return jsonString;
    }

    /**
     * 拼接url地址:
     * 例：http://127.0.0.1:xxx/xx/xxx?xx=xx&xx=xx
     */
    private String buildUrl(String basisUrl, Map<Object, Object> param) {
        StringBuilder params = new StringBuilder(basisUrl);
        params.append("?");
        Optional.ofNullable(param.entrySet()).orElse(new HashSet<>()).stream().forEach((Map.Entry entry) -> {
            params.append(entry.getKey()).append("=").append(entry.getValue()).append("&");
        });
        return params.toString().substring(0, params.toString().length() - 1);
    }
}

三、远程调用的实现：

1、test-demo工程：

声明控制类：

@RestController
@RequestMapping("/v1")
public class DemoController {
    @Autowired
    private DemoService demoService;

    /**
     * get方式
     * 查询全量信息
     *
     * http://localhost:8081/v1/get-detail?pageNum=1&pageSize=8
     * */
    @GetMapping("/get-detail")
    public Response<List<ResponseVO>> list1(
            @RequestParam(value = "pageNum", required = false , defaultValue = "1") Integer pageNum,
            @RequestParam(value = "pageSize", required = false , defaultValue = "8") Integer pageSize) {
        return Response.success(demoService.selectDetail(pageNum , pageSize));
    }

    /**
     * post方式
     * 查询全量信息
     *
     * http://localhost:8081/v1/post-detail
     * */
    @PostMapping("/post-detail")
    public Response<List<ResponseVO>> list2() {
        return Response.success(demoService.selectList());
    }
}

2、client-demo工程：

（1）、获取test-demo工程接口返回：

@Component
@Slf4j
public class HttpClient {
    @Autowired
    private HttpClientUtil httpClientUtil;

    @Value("${url.v1.clent:http://localhost:8081/v1}")
    private String url;

    public String getGetMethodURL() {
        return url + "/get-detail";
    }

    public String list() {
        //获取根地址
        String url = getGetMethodURL();
        //放置请求参数
        Map<Object, Object> param = new HashMap<>();
        param.put("pageNum", 1);
        param.put("pageSize", 100);
        String jsonString = httpClientUtil.getUrlResponse(url, param, HttpMethod.GET, null);
        Object data = JSONObject.parseObject(jsonString).get("entity");
        if (ObjectUtils.isEmpty(data)) {
            return "数据为空";
        }
        String dataList = JSONObject.toJSONString(data);
        return dataList;
    }

}

（2）、业务类：

@Service
public class DemoServiceImpl implements DemoService {
    @Autowired
    private HttpClient httpClient;

    @Override
    public String selectList() {
        return httpClient.list();
    }
}

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