Spring遠程調用HttpClient/RestTemplate的方法

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一、HttpClient

兩個系統間如何互相訪問？兩個tomcat上的項目如何互相訪問？

       采用HttpClient實現跨系統的接口調用。

介紹：

官網：http://hc.apache.org/index.html

現在也叫：HttpComponents

HttpClient可以發送get、post、put、delete、…等請求

使用：

導入坐標

<dependency>
  <groupId>org.apache.httpcomponents</groupId>
  <artifactId>httpclient</artifactId>
  <version>4.4</version>
</dependency>
//1、使用HttpClient發起Get請求
public class DoGET {
 
  public static void main(String[] args) throws Exception {
    // 創建Httpclient對象,相當於打開瞭瀏覽器
    CloseableHttpClient httpclient = HttpClients.createDefault();
 
    // 創建HttpGet請求，相當於在瀏覽器輸入地址
    HttpGet httpGet = new HttpGet("http://www.baidu.com/");
 
    CloseableHttpResponse response = null;
    try {
      // 執行請求，相當於敲完地址後按下回車。獲取響應
      response = httpclient.execute(httpGet);
      // 判斷返回狀態是否為200
      if (response.getStatusLine().getStatusCode() == 200) {
        // 解析響應，獲取數據
        String content = EntityUtils.toString(response.getEntity(), "UTF-8");
        System.out.println(content);
      }
    } finally {
      if (response != null) {
        // 關閉資源
        response.close();
      }
      // 關閉瀏覽器
      httpclient.close();
    }
 
  }
}
 
 
//2、使用HttpClient發起帶參數的Get請求
public class DoGETParam {
 
  public static void main(String[] args) throws Exception {
    // 創建Httpclient對象
    CloseableHttpClient httpclient = HttpClients.createDefault();
    // 創建URI對象，並且設置請求參數
    URI uri = new URIBuilder("http://www.baidu.com/s").setParameter("wd", "java").build();
    
    // 創建http GET請求
    HttpGet httpGet = new HttpGet(uri);
 
    // HttpGet get = new HttpGet("http://www.baidu.com/s?wd=java");
    
    CloseableHttpResponse response = null;
    try {
      // 執行請求
      response = httpclient.execute(httpGet);
      // 判斷返回狀態是否為200
      if (response.getStatusLine().getStatusCode() == 200) {
        // 解析響應數據
        String content = EntityUtils.toString(response.getEntity(), "UTF-8");
        System.out.println(content);
      }
    } finally {
      if (response != null) {
        response.close();
      }
      httpclient.close();
    }
  }
}
 
 
//3、使用HttpClient發起POST請求
public class DoPOST {
  public static void main(String[] args) throws Exception {
    // 創建Httpclient對象
    CloseableHttpClient httpclient = HttpClients.createDefault();
    // 創建http POST請求
    HttpPost httpPost = new HttpPost("http://www.oschina.net/");
    // 把自己偽裝成瀏覽器。否則開源中國會攔截訪問
    httpPost.setHeader("User-Agent", "Mozilla/5.0 (Windows NT 10.0; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/56.0.2924.87 Safari/537.36");
 
    CloseableHttpResponse response = null;
    try {
      // 執行請求
      response = httpclient.execute(httpPost);
      // 判斷返回狀態是否為200
      if (response.getStatusLine().getStatusCode() == 200) {
        // 解析響應數據
        String content = EntityUtils.toString(response.getEntity(), "UTF-8");
        System.out.println(content);
      }
    } finally {
      if (response != null) {
        response.close();
      }
      // 關閉瀏覽器
      httpclient.close();
    }
 
  }
}
 
 
//4、使用HttpClient發起帶有參數的POST請求
public class DoPOSTParam {
 
  public static void main(String[] args) throws Exception {
    // 創建Httpclient對象
    CloseableHttpClient httpclient = HttpClients.createDefault();
    // 創建http POST請求，訪問開源中國
    HttpPost httpPost = new HttpPost("http://www.oschina.net/search");
 
    // 根據開源中國的請求需要，設置post請求參數
    List<NameValuePair> parameters = new ArrayList<NameValuePair>(0);
    parameters.add(new BasicNameValuePair("scope", "project"));
    parameters.add(new BasicNameValuePair("q", "java"));
    parameters.add(new BasicNameValuePair("fromerr", "8bDnUWwC"));
    // 構造一個form表單式的實體
    UrlEncodedFormEntity formEntity = new UrlEncodedFormEntity(parameters);
    // 將請求實體設置到httpPost對象中
    httpPost.setEntity(formEntity);
 
    CloseableHttpResponse response = null;
    try {
      // 執行請求
      response = httpclient.execute(httpPost);
      // 判斷返回狀態是否為200
      if (response.getStatusLine().getStatusCode() == 200) {
        // 解析響應體
        String content = EntityUtils.toString(response.getEntity(), "UTF-8");
        System.out.println(content);
      }
    } finally {
      if (response != null) {
        response.close();
      }
      // 關閉瀏覽器
      httpclient.close();
    }
  }
}

 二、RestTemplate

RestTemplate是Spring提供的用於訪問Rest服務的客戶端，RestTemplate提供瞭多種便捷訪問遠程Http服務的方法

HTTP開發是用apache的HttpClient開發，代碼復雜，還得操心資源回收等。代碼很復雜，冗餘代碼多。

導入坐標

<dependency>
  <groupId>org.springframework.boot</groupId>
  <artifactId>spring-boot-starter-web</artifactId>
</dependency>

創建RestTemplate對象

@Configuration//加上這個註解作用，可以被Spring掃描
public class RestTemplateConfig {
  /**
   * 創建RestTemplate對象，將RestTemplate對象的生命周期的管理交給Spring
   * @return
   */
  @Bean
  public RestTemplate restTemplate(){
    RestTemplate restTemplate = new RestTemplate();
    //主要解決中文亂碼
    restTemplate.getMessageConverters().set(1, new StringHttpMessageConverter(StandardCharsets.UTF_8));
    return restTemplate;
  }
}

RestTempController

import org.springframework.http.ResponseEntity;
import org.springframework.stereotype.Controller;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.client.RestTemplate;
 
import javax.annotation.Resource;
 
@RestController
@RequestMapping("/consumer")
public class ConsumerController {
  // 從Spring的容器中獲取restTemplate
  @Resource
  private RestTemplate restTemplate;
 
  /**
   * 通過Get請求，保存數據
   */
  @GetMapping("/{id}")
  public ResponseEntity<String> findById(@PathVariable Integer id){
    //發起遠程請求:通過RestTemplate發起get請求
    ResponseEntity<String> entity = restTemplate.getForEntity("http://localhost:8090/goods2/1", String.class);
    System.out.println("entity.getStatusCode():"+entity.getStatusCode());
    System.out.println(entity.getBody());
    return entity;
  }
 
  /**
   * 通過Post請求，保存數據
   */
  @PostMapping
  public ResponseEntity<String> saveGoods(@RequestBody Goods goods){
    //通過RestTemplate發起遠程請求
    /**
     * 第一個參數：遠程地址URI
     * 第二個參數：數據
     * 第三個參數：返回值類型
     */
    ResponseEntity<String> entity = restTemplate.postForEntity("http://localhost:8090/goods2", goods, String.class);
    System.out.println("entity.getStatusCode():"+entity.getStatusCode());
    System.out.println(entity.getBody());
    return entity;
  }
 
  @PutMapping
  public ResponseEntity<String> updateGoods(@RequestBody Goods goods){
    restTemplate.put("http://localhost:8090/goods2",goods);
    return new ResponseEntity<>("修改成功", HttpStatus.OK);
  }
 
  @DeleteMapping("/{id}")
  public ResponseEntity<String> deleteById(@PathVariable Integer id){
    restTemplate.delete("http://localhost:8090/goods2/"+id);
    return new ResponseEntity<>("刪除成功", HttpStatus.OK);
  }
}

隻用maven不用springboot框架時隻需要導入依賴到pom文件

<dependency>
  <groupId>org.springframework</groupId>
  <artifactId>spring-web</artifactId>
</dependency>

直接new RestTemplate()對象使用即可

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