RestTemplate<org.springframework.web.client.RestTemplate>

从Spring3.0开始支持的一个HTTP请求工具，提供了REST请求方案的模版，GET 请求、POST 请求、PUT请求、DELETE请求以及一些通用的请求执行方法exchange以及execute。

RestTemplate 继承自InterceptingHttpAccessor并且实现了RestOperations接口，其中，RestOperations接口定义了基本的 RESTful 操作，这些操作在RestTemplate中实现。

案例代码：

import org.springframework.http.ResponseEntity;
import org.springframework.web.client.RestTemplate;
import org.what21.cloud.entity.User;

import java.util.HashMap;
import java.util.List;
import java.util.Map;

public class RestTemplateGetForEntityDemo {

    public static void getForEntityReturnBean(){
        String url = "http://127.0.0.1:9001/user/get/1";
        RestTemplate rest = new RestTemplate();
        ResponseEntity<User> responseEntity = rest.getForEntity(url, User.class);
        User user = responseEntity.getBody();
        System.out.println(user);
    }

    public static void getForEntityReturnBean2(){
        String url = "http://127.0.0.1:9001/user/get2?id={id}";
        RestTemplate rest = new RestTemplate();
        Map<String, Object> paramMap = new HashMap<String, Object>();
        paramMap.put("id", 2);
        ResponseEntity<String> responseEntity = rest.getForEntity(url,String.class,paramMap);
        System.out.println(responseEntity.getBody());
    }

    public static void getForEntityReturnList(){
        String url = "http://127.0.0.1:9001/user/list";
        RestTemplate rest = new RestTemplate();
        ResponseEntity<List> responseEntity = rest.getForEntity(url, List.class);
        List<Map> dataList = responseEntity.getBody();
        System.out.println(dataList);
        for(Map map : dataList){
            System.out.println(map.get("id") + "," + map.get("username")+"," + map.get("realName"));
        }
    }

    public static void main(String[] args) {
        getForEntityReturnBean();
        getForEntityReturnBean2();
        getForEntityReturnList();
    }

}

import org.springframework.web.client.RestTemplate;
import org.what21.cloud.entity.User;

import java.util.HashMap;
import java.util.List;
import java.util.Map;

public class RestTemplateGetForObjectDemo {

    public static void getForObjectReturnBean(){
        String url = "http://127.0.0.1:9001/user/get/1";
        RestTemplate rest = new RestTemplate();
        User user = rest.getForObject(url, User.class);
        System.out.println(user);
    }

    public static void getForObjectReturnBean2(){
        String url = "http://127.0.0.1:9001/user/get2?id={id}";
        RestTemplate rest = new RestTemplate();
        Map<String, Object> paramMap = new HashMap<String, Object>();
        paramMap.put("id", 2);
        String json = rest.getForObject(url,String.class,paramMap);
        System.out.println(json);
    }

    public static void getForObjectReturnList(){
        String url = "http://127.0.0.1:9001/user/list";
        RestTemplate rest = new RestTemplate();
        List<Map> dataList = rest.getForObject(url, List.class);
        System.out.println(dataList);
        for(Map map : dataList){
            System.out.println(map.get("id") + "," + map.get("username")+"," + map.get("realName"));
        }
    }

    public static void main(String[] args) {
        getForObjectReturnBean();
        getForObjectReturnBean2();
        getForObjectReturnList();
    }

}

import com.alibaba.fastjson.JSONObject;
import lombok.extern.slf4j.Slf4j;
import org.apache.http.client.HttpClient;
import org.apache.http.client.config.RequestConfig;
import org.apache.http.impl.client.DefaultHttpRequestRetryHandler;
import org.apache.http.impl.client.HttpClientBuilder;
import org.springframework.http.*;
import org.springframework.http.client.*;
import org.springframework.web.client.RestTemplate;
import org.what21.cloud.entity.User;

import java.io.IOException;
import java.util.*;

@Slf4j
public class RestTemplateExchangeDemo {

    static class RestTemplateConsumerLogger implements ClientHttpRequestInterceptor {

        @Override
        public ClientHttpResponse intercept(HttpRequest httpRequest, byte[] bytes, ClientHttpRequestExecution clientHttpRequestExecution) throws IOException {
            // 传递header参数
            HttpHeaders headers = httpRequest.getHeaders();
            headers.add("header_name", "header_value");
            headers.add("header_token", "token_value");
            return clientHttpRequestExecution.execute(httpRequest, bytes);
        }
    }

    public static RestTemplate restTemplate() {
        //生成一个设置了连接超时时间、请求超时时间、异常重试次数3次
        RequestConfig config = RequestConfig.custom().setConnectionRequestTimeout(10000).setConnectTimeout(10000).setSocketTimeout(30000).build();
        HttpClientBuilder builder = HttpClientBuilder.create().setDefaultRequestConfig(config).setRetryHandler(new DefaultHttpRequestRetryHandler(3, false));
        HttpClient httpClient = builder.build();
        ClientHttpRequestFactory requestFactory = new HttpComponentsClientHttpRequestFactory(httpClient);
        RestTemplate restTemplate = new RestTemplate(requestFactory);
        restTemplate.setInterceptors(Collections.singletonList(new RestTemplateConsumerLogger()));
        return restTemplate;
    }

    public static User getUser(RestTemplate restTemplate, String remoteUrl, Integer id) {
        //设置Http的Header
        HttpHeaders headers = new HttpHeaders();
        headers.setContentType(MediaType.APPLICATION_JSON);
        //设置访问参数
        HashMap<String, Object> params = new HashMap<>();
        params.put("id", id);
        //设置访问的Entity
        HttpEntity entity = new HttpEntity<>(params, headers);
        ResponseEntity<String> result = null;
        try {
            //发起一个POST请求
            result = restTemplate.exchange(remoteUrl, HttpMethod.POST, entity, String.class);
            User user = JSONObject.parseObject(result.getBody(), User.class);
            return user;
        } catch (Exception e) {
            e.printStackTrace();
            log.error("调用错误：" + e.getMessage());
        }
        return null;
    }

    public static void main(String[] args) {
        RestTemplate restTemplate = restTemplate();
        User user = getUser(restTemplate, "http://127.0.0.1:9001/user/get3", 3);
        System.out.println(user);
    }

}

import com.alibaba.fastjson.JSON;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.beans.factory.annotation.Qualifier;
import org.springframework.web.bind.annotation.*;
import org.what21.cloud.entity.User;
import org.what21.cloud.entity.param.UserGetParam;
import org.what21.cloud.service.IUserService;

import javax.servlet.http.HttpServletRequest;
import java.util.List;

@RestController
@RequestMapping("/user")
public class UserController {

    @Autowired
    @Qualifier("userService")
    IUserService userService;

    @RequestMapping(path = "/list", method = {RequestMethod.GET})
    public String list() {
        List<User> userList = userService.listUsers();
        return JSON.toJSONString(userList);
    }

    @RequestMapping(path = "/get/{id}", method = {RequestMethod.GET, RequestMethod.POST})
    public String get(@PathVariable("id") Integer id) {
        User user = userService.getUser(id);
        return JSON.toJSONString(user);
    }

    @RequestMapping(path = "/get2", method = {RequestMethod.GET, RequestMethod.POST})
    public String get2(@RequestParam("id") Integer id) {
        User user = userService.getUser(id);
        return JSON.toJSONString(user);
    }

    @RequestMapping(path = "/get3", method = {RequestMethod.GET, RequestMethod.POST})
    public String get3(HttpServletRequest request, @RequestBody UserGetParam userGetParam) {
        System.out.println("header_token = " + request.getHeader("header_token"));
        System.out.println("header_name = " + request.getHeader("header_name"));
        User user = userService.getUser(userGetParam.getId());
        return JSON.toJSONString(user);
    }

}