Java中实现http请求的方式
RestTemplate是Spring提供的用于访问Rest服务的客户端，RestTemplate提供了多种便捷访问远程Http服务的方法，能够大大提高客户端的编写效率。RestTemplate提供了常见的REST请求方案的模版，例如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。在java开发中，经常遇到需要调用第三方提供的接口
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在java开发中，经常遇到需要调用第三方提供的接口服务的需求，下面对实现http请求的方式进行浅入浅析并进行实例尝试。
在java开发中，实现访问第三方接口服务的常见方式：
- 通过JDK类Java.net.HttpURLConnection;
- 通过commons-httpclient封装好的HttpClient；
- 通过org.apache.httpcomponents封装好的CloseableHttpClient；
- 通过com.squareup.okhttp3封装好的OkHttpClient；
- 通过springboot中RestTemplate；
1、HttpURLConnection
JDK原生提供的net包，无需其他jar包，实例如下
public class HttpUrlConnectionClientUtil {
/**
* Http get请求
* @param httpUrl 连接
* @return 响应数据
*/
public static String doGet(String httpUrl){
HttpURLConnection connection = null;
InputStream is = null;
BufferedReader br = null;
StringBuffer result = new StringBuffer();
try {
//创建连接
URL url = new URL(httpUrl);
connection = (HttpURLConnection) url.openConnection();
//设置请求方式
connection.setRequestMethod("GET");
//设置连接超时时间
connection.setReadTimeout(15000);
//开始连接
connection.connect();
//获取响应数据
if (connection.getResponseCode() == 200) {
//获取返回的数据
is = connection.getInputStream();
if (null != is) {
br = new BufferedReader(new InputStreamReader(is, "UTF-8"));
String temp = null;
while (null != (temp = br.readLine())) {
result.append(temp);
}
}
}
} catch (IOException e) {
e.printStackTrace();
} finally {
if (null != br) {
try {
br.close();
} catch (IOException e) {
e.printStackTrace();
}
}
if (null != is) {
try {
is.close();
} catch (IOException e) {
e.printStackTrace();
}
}
//关闭远程连接
connection.disconnect();
}
return result.toString();
}
/**
* Http post请求
* @param httpUrl 连接
* @param param 参数
* @return
*/
public static String doPost(String httpUrl, String param) {
HttpURLConnection connection = null;
OutputStream os = null;
InputStream is = null;
BufferedReader br = null;
StringBuffer result = new StringBuffer();
try {
//创建连接对象
URL url = new URL(httpUrl);
//创建连接
connection = (HttpURLConnection) url.openConnection();
//设置请求方法
connection.setRequestMethod("POST");
//设置连接超时时间
connection.setConnectTimeout(15000);
//设置读取超时时间
connection.setReadTimeout(15000);
//DoOutput设置是否向httpUrlConnection输出，DoInput设置是否从httpUrlConnection读入，此外发送post请求必须设置这两个
//设置是否可读取
connection.setDoOutput(true);
connection.setDoInput(true);
//设置通用的请求属性
connection.setRequestProperty("accept", "*/*");
connection.setRequestProperty("connection", "Keep-Alive");
connection.setRequestProperty("user-agent", "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1)");
connection.setRequestProperty("Content-Type", "application/json;charset=utf-8");
//拼装参数
if (null != param && !param.equals("")) {
//设置参数
os = connection.getOutputStream();
//拼装参数
os.write(param.getBytes("UTF-8"));
}
//读取响应
if (connection.getResponseCode() == 200) {
is = connection.getInputStream();
if (null != is) {
br = new BufferedReader(new InputStreamReader(is, "UTF-8"));
String temp = null;
while (null != (temp = br.readLine())) {
result.append(temp);
result.append("\r\n");
}
}
}
} catch (MalformedURLException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} finally {
if(br!=null){
try {
br.close();
} catch (IOException e) {
e.printStackTrace();
}
}
if(os!=null){
try {
os.close();
} catch (IOException e) {
e.printStackTrace();
}
}
if(is!=null){
try {
is.close();
} catch (IOException e) {
e.printStackTrace();
}
}
//关闭连接
connection.disconnect();
}
return result.toString();
}
public static void main(String[] args) {
String messageByGet = doGet("http://***");
*** resultByGet = JSON.parseObject(messageByGet, ***.class);
System.out.println(resultByGet);
Map param = new HashMap<>();
param.put("name","admin");
String str = JSON.toJSONString(param);
String messageByPost = doPost("http://***", str);
*** resultByPost = JSON.parseObject(messageByPost, ***.class);
System.out.println(resultByPost);
}
}
结果类似如下
2、HttpClient
引入依赖
<dependency>
<groupId>commons-httpclient</groupId>
<artifactId>commons-httpclient</artifactId>
<version>3.1</version>
</dependency>
public class HttpClientUtil {
/**
* httpClient的get请求方式
* 使用GetMethod来访问一个URL对应的网页实现步骤：
* 1.生成一个HttpClient对象并设置相应的参数；
* 2.生成一个GetMethod对象并设置响应的参数；
* 3.用HttpClient生成的对象来执行GetMethod生成的Get方法；
* 4.处理响应状态码；
* 5.若响应正常，处理HTTP响应内容；
* 6.释放连接。
* @param url
* @param charset
* @return
*/
public static String doGet(String url, String charset) {
//1.生成HttpClient对象并设置参数
HttpClient httpClient = new HttpClient();
//设置Http连接超时为5秒
httpClient.getHttpConnectionManager().getParams().setConnectionTimeout(5000);
//2.生成GetMethod对象并设置参数
GetMethod getMethod = new GetMethod(url);
//设置get请求超时为5秒
getMethod.getParams().setParameter(HttpMethodParams.SO_TIMEOUT, 5000);
//设置请求重试处理，用的是默认的重试处理：请求三次
getMethod.getParams().setParameter(HttpMethodParams.RETRY_HANDLER, new DefaultHttpMethodRetryHandler());
String response = "";
//3.执行HTTP GET 请求
try {
int statusCode = httpClient.executeMethod(getMethod);
//4.判断访问的状态码
if (statusCode != HttpStatus.SC_OK) {
System.err.println("请求出错：" + getMethod.getStatusLine());
}
//5.处理HTTP响应内容
//HTTP响应头部信息，这里简单打印
Header[] headers = getMethod.getResponseHeaders();
for(Header h : headers) {
System.out.println(h.getName() + "headers:" + h.getValue());
}
//读取HTTP响应内容，这里简单打印网页内容
//读取为字节数组
byte[] responseBody = getMethod.getResponseBody();
response = new String(responseBody, charset);
System.out.println("response:" + response);
//读取为InputStream，在网页内容数据量大时候推荐使用
//InputStream response = getMethod.getResponseBodyAsStream();
} catch (HttpException e) {
System.out.println("请检查输入的URL!");
e.printStackTrace();
} catch (IOException e) {
//发生网络异常
System.out.println("发生网络异常!");
} finally {
//6.释放连接
getMethod.releaseConnection();
}
return response;
}
/**
* post请求
* @param url
* @param json
* @return
*/
public static String doPost(String url, JSONObject json, String charset){
HttpClient httpClient = new HttpClient();
PostMethod postMethod = new PostMethod(url);
postMethod.addRequestHeader("accept", "*/*");
postMethod.addRequestHeader("connection", "Keep-Alive");
//设置json格式传送
postMethod.addRequestHeader("Content-Type", "application/json;charset=utf-8");
//必须设置下面这个Header
postMethod.addRequestHeader("User-Agent", "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/58.0.3029.81 Safari/537.36");
//添加请求参数
//postMethod.addParameter("params", json.toJSONString());
try {
postMethod.setRequestEntity(new StringRequestEntity(json.toJSONString(), "application/json", "utf-8"));
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
}
String response = "";
try {
int code = httpClient.executeMethod(postMethod);
if (code == 200){
byte[] responseBody = postMethod.getResponseBody();
response = new String(responseBody, charset);
System.out.println("response:" + response);
// 返回值中文乱码
//response = postMethod.getResponseBodyAsString();
}
} catch (IOException e) {
e.printStackTrace();
}
return response;
}
public static void main(String[] args) {
String messageByGet = doGet("http://***", "UTF-8");
System.out.println(messageByGet);
JSONObject jsonObject = new JSONObject();
jsonObject.put("name","admin");
String messageByPost = doPost("http://***", jsonObject, "UTF-8");
System.out.println(messageByPost);
}
}
结果类似如下
3、CloseableHttpClient
引入依赖
<dependency>
<groupId>org.apache.httpcomponents</groupId>
<artifactId>httpclient</artifactId>
<version>4.5.2</version>
</dependency>
public class CloseableHttpClientUtil {
private static String tokenString = "";
private static String AUTH_TOKEN_EXPIRED = "AUTH_TOKEN_EXPIRED";
private static CloseableHttpClient httpClient = null;
/**
* 以get方式调用第三方接口
* @param url
* @param token
* @return
*/
public static String doGet(String url, String token) {
//创建HttpClient对象
CloseableHttpClient httpClient = HttpClientBuilder.create().build();
HttpGet httpGet = new HttpGet(url);
if (null != tokenString && !tokenString.equals("")) {
tokenString = getToken();
}
//api_gateway_auth_token自定义header头，用于token验证使用
httpGet.addHeader("api_gateway_auth_token",tokenString);
httpGet.addHeader("User-Agent", "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/58.0.3029.81 Safari/537.36");
try {
HttpResponse response = httpClient.execute(httpGet);
if (response.getStatusLine().getStatusCode() == HttpStatus.SC_OK) {
//返回json格式
String res = EntityUtils.toString(response.getEntity());
return res;
}
} catch (IOException e) {
e.printStackTrace();
}
return null;
}
/**
* 以post方式调用第三方接口
* @param url
* @param json
* @return
*/
public static String doPost(String url, JSONObject json) {
if (null == httpClient) {
httpClient = HttpClientBuilder.create().build();
}
HttpPost httpPost = new HttpPost(url);
if (null != tokenString && tokenString.equals("")) {
tokenString = getToken();
}
//api_gateway_auth_token自定义header头，用于token验证使用
httpPost.addHeader("api_gateway_auth_token", tokenString);
httpPost.addHeader("User-Agent", "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/58.0.3029.81 Safari/537.36");
try {
StringEntity stringEntity = new StringEntity(json.toString());
stringEntity.setContentEncoding("UTF-8");
//发送json数据需要设置contentType
stringEntity.setContentType("application/json;charset=utf-8");
//设置请求参数
httpPost.setEntity(stringEntity);
HttpResponse response = httpClient.execute(httpPost);
if (response.getStatusLine().getStatusCode() == HttpStatus.SC_OK) {
//返回json格式
String res = EntityUtils.toString(response.getEntity());
return res;
}
} catch (IOException e) {
e.printStackTrace();
} finally {
if (httpClient != null){
try {
httpClient.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
return null;
}
public static void main(String[] args) {
String messageByGet = doGet("http://***", "");
System.out.println(messageByGet);
JSONObject jsonObject = new JSONObject();
jsonObject.put("name","admin");
String response = doPost("http://***", jsonObject);
System.out.println(response);
}
}
结果类似如下
4、OkHttpClient
引入依赖
<dependency>
<groupId>com.squareup.okhttp3</groupId>
<artifactId>okhttp</artifactId>
<version>3.10.0</version>
</dependency>
@Slf4j
public class OkHttpClientUtil {
private volatile static OkHttpClient client;
private static final MediaType JSON = MediaType.parse("application/json; charset=utf-8");
private static final int MAX_IDLE_CONNECTION = 10;
private static final long KEEP_ALIVE_DURATION = 60;
private static final long CONNECT_TIMEOUT = 30;
private static final long READ_TIMEOUT = 30;
/**
* 单例模式(双重检查模式) 获取类实例
*
* @return client
*/
private static OkHttpClient getInstance() {
if (client == null) {
synchronized (OkHttpClient.class) {
if (client == null) {
client = new OkHttpClient.Builder()
.connectTimeout(CONNECT_TIMEOUT, TimeUnit.SECONDS)
.readTimeout(READ_TIMEOUT, TimeUnit.SECONDS)
.connectionPool(new ConnectionPool(MAX_IDLE_CONNECTION, KEEP_ALIVE_DURATION,TimeUnit.MINUTES))
.build();
}
}
}
return client;
}
public static String syncPost(String url, String json) {
RequestBody body = RequestBody.create(JSON, json);
Request request = new Request.Builder()
.url(url)
.post(body)
.build();
try {
Response response = OkHttpClientUtil.getInstance().newCall(request).execute();
if (response.isSuccessful()) {
String result = response.body().string();
log.info("syncPost response = {}, responseBody= {}", response, result);
return result;
}
String result = response.body().string();
log.info("syncPost response = {}, responseBody= {}", response, result);
throw new IOException("三方接口返回http状态码为" + response.code());
} catch (Exception e) {
log.error("syncPost() url:{} have a ecxeption {}", url, e);
throw new RuntimeException("syncPost() have a ecxeption {}" + e.getMessage());
}
}
public static String syncGet(String url, Map<String, Object> headParamsMap) {
Request request;
final Request.Builder builder = new Request.Builder().url(url);
try {
if (!CollectionUtils.isEmpty(headParamsMap)) {
final Iterator<Map.Entry<String, Object>> iterator = headParamsMap.entrySet().iterator();
while (iterator.hasNext()) {
final Map.Entry<String, Object> entry = iterator.next();
builder.addHeader(entry.getKey(), (String) entry.getValue());
}
}
request = builder.build();
Response response = OkHttpClientUtil.getInstance().newCall(request).execute();
String result = response.body().string();
log.info("syncGet response = {},responseBody= {}", response, result);
if (!response.isSuccessful()) {
throw new IOException("三方接口返回http状态码为" + response.code());
}
return result;
} catch (Exception e) {
log.error("remote interface url:{} have a ecxeption {}", url, e);
throw new RuntimeException("三方接口返回异常");
}
}
public static void main(String[] args) {
String messageByGet = syncGet("http://***", null);
System.out.println(messageByGet);
JSONObject jsonObject = new JSONObject();
jsonObject.put("pageNum", 1);
jsonObject.put("pageSize", 10);
jsonObject.put("name","admin");
String messageByPost = syncPost("http://***", jsonObject.toJSONString());
System.out.println(messageByPost);
}
}
结果类似如下
5、RestTemplate
引入依赖
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
RestTemplate是Spring提供的用于访问Rest服务的客户端，RestTemplate提供了多种便捷访问远程Http服务的方法，能够大大提高客户端的编写效率。RestTemplate提供了常见的REST请求方案的模版，例如 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。
@Configuration
public class RestTemplateConfig {
@Bean
public RestTemplate restTemplate(ClientHttpRequestFactory factory){
return new RestTemplate(factory);
}
@Bean
public ClientHttpRequestFactory simpleClientHttpRequestFactory(){
SimpleClientHttpRequestFactory factory = new SimpleClientHttpRequestFactory();
factory.setConnectTimeout(15000);
factory.setReadTimeout(5000);
return factory;
}
}
@Autowired
private RestTemplate restTemplate;
private static final String getUrl = "http://***";
private static final String postUrl = "http://***";
@Test
void get1() {
ResponseEntity<ResponseData> responseEntity = restTemplate.getForEntity(getUrl, ResponseData.class);
ResponseData responseData = responseEntity.getBody();
System.out.println(responseData);
}
@Test
void get2() {
ResponseData responseData = restTemplate.getForObject(getUrl, ResponseData.class);
System.out.println(responseData);
}
@Test
void post1() {
Map param = new HashMap<>();
param.put("name","admin");
ResponseEntity<String> responseEntity = restTemplate.postForEntity(postUrl, param, String.class);
String body = responseEntity.getBody();
System.out.println(body);
}
@Test
void post2() {
Map param = new HashMap<>();
param.put("name","admin");
String body = restTemplate.postForObject(postUrl, param, String.class);
System.out.println(body);
}
@Test
void exchange() {
//header参数
HttpHeaders headers = new HttpHeaders();
String token = "1234567890";
headers.add("Authorization", token);
headers.setContentType(MediaType.APPLICATION_JSON);
//放入body中的json参数
JSONObject jsonObject = new JSONObject();
jsonObject.put("pageNum", 1);
jsonObject.put("pageSize", 10);
jsonObject.put("name","admin");
//组装
HttpEntity<JSONObject> request = new HttpEntity<>(jsonObject, headers);
ResponseEntity<String> responseEntity = restTemplate.exchange(postUrl, HttpMethod.POST, request, String.class);
String body = responseEntity.getBody();
System.out.println(body);
}
若是普通java工程推荐使用OkHttpClient，若是spring工程推荐使用RestTemplate。
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