Java调用RestFul接口

使用Java调用RestFul接口，以POST请求为例，以下提供几种方法：

一、通过HttpURLConnection调用

 1 public String postRequest(String url, String param) {
 2     StringBuffer result = new StringBuffer();
 3
 4     HttpURLConnection conn = null;
 5     OutputStream out = null;
 6     BufferedReader reader = null;
 7     try {
 8         URL restUrl = new URL(url);
 9         conn = (HttpURLConnection) restUrl.openConnection();
10         conn.setRequestMethod("POST");
11         conn.setDoOutput(true);
12         conn.setDoInput(true);
13
14         conn.setRequestProperty("accept", "*/*");
15         conn.setRequestProperty("connection", "Keep-Alive");
16         conn.setRequestProperty("user-agent", "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1;SV1)");
17         conn.setRequestProperty("Content-Type", "application/json; charset=utf-8");
18
19         conn.connect();
20         out = conn.getOutputStream();
21         out.write(param.getBytes());
22         out.flush();
23
24         int responseCode = conn.getResponseCode();
25         if(responseCode != 200){
26             throw new RuntimeException("Error responseCode:" + responseCode);
27         }
28
29         String output = null;
30         reader = new BufferedReader(new InputStreamReader(conn.getInputStream(), "utf-8"));
31         while((output=reader.readLine()) != null){
32             result.append(output);
33         }
34     } catch (Exception e) {
35         e.printStackTrace();
36         throw new RuntimeException("调用接口出错：param+"+param);
37     } finally {
38         try {
39             if(reader != null){
40                 reader.close();
41             }
42             if(out != null){
43                 out.close();
44             }
45             if(conn != null){
46                 conn.disconnect();
47             }
48         } catch (Exception e2) {
49             e2.printStackTrace();
50         }
51     }
52
53     return result.toString();
54 }

二、通过Spring提供的RestTemplate模板调用

 1 public class RestTemplateUtil {
 2
 3     @Autowired
 4     private RestTemplate restTemplate;
 5
 6     @Bean
 7     public RestTemplate restTemplate(){
 8         RestTemplate template = new RestTemplate();
 9         // messageConverters是RestTemplate的一个final修饰的List类型的成员变量
10         // messageConverters的第二个元素存储的是StringHttpMessageConverter类型的消息转换器
11         // StringHttpMessageConverter的默认字符集是ISO-8859-1,在此处设置utf-8字符集避免产生乱码
12         template.getMessageConverters().set(1, new StringHttpMessageConverter(Charset.forName("utf-8")));
13         return template;
14     }
15
16     public String post(String url, String jsonParam){
17         // 自定义请求头
18         HttpHeaders headers = new HttpHeaders();
19         headers.setContentType(MediaType.APPLICATION_JSON);
20         headers.setAcceptCharset(Collections.singletonList(Charset.forName("utf-8")));
21         headers.setAccept(Collections.singletonList(MediaType.APPLICATION_JSON));
22
23         // 参数
24         HttpEntity<String> entity = new HttpEntity<String>(jsonParam, headers);
25         // POST方式请求
26         ResponseEntity<String> responseEntity = restTemplate.exchange(url, HttpMethod.POST, entity, String.class);
27         if(responseEntity == null){
28             return null;
29         }
30
31         return responseEntity.getBody().toString();
32     }
33
34 }

三、通过HttpClient调用

 1 public class HttpClientUtil {
 2
 3     public String post(String url, Map<String, Object> pramMap) throws Exception {
 4         String result = null;
 5         // DefaultHttpClient已过时,使用CloseableHttpClient替代
 6         CloseableHttpClient closeableHttpClient = null;
 7         CloseableHttpResponse response = null;
 8         try {
 9             closeableHttpClient = HttpClients.createDefault();
10             HttpPost postRequest = new HttpPost(url);
11             List<NameValuePair> pairs = new ArrayList<>();
12             if(pramMap!=null && pramMap.size() > 0){
13                 for (Map.Entry<String, Object> entry : pramMap.entrySet()) {
14                     pairs.add(new BasicNameValuePair(entry.getKey(), String.valueOf(entry.getValue())));
15                 }
16             }
17             UrlEncodedFormEntity formEntity = new UrlEncodedFormEntity(pairs, "utf-8");
18             postRequest.setEntity(formEntity);
19
20             response = closeableHttpClient.execute(postRequest);
21             if(response!=null && response.getStatusLine().getStatusCode()==HttpStatus.SC_OK){
22                 result = EntityUtils.toString(response.getEntity(), "utf-8");
23             }else{
24                 throw new Exception("post请求失败,url" + url);
25             }
26
27         } catch (Exception e) {
28             e.printStackTrace();
29             throw e;
30         } finally {
31             try {
32                 if(response != null){
33                     response.close();
34                 }
35                 if(closeableHttpClient != null){
36                     closeableHttpClient.close();
37                 }
38             } catch (IOException e) {
39                 e.printStackTrace();
40             }
41         }
42
43         return result;
44     }
45
46 }