Java工具類--通過HttpClient傳送http請求
在寫網路程式的時候，經常會有從網址獲取資料的需求，上一篇解析JSON就需要從百度獲取天氣資料，本文介紹一種Java傳送http請求的工具–HttpClient。
##HttpClient的介紹
The most essential function of HttpClient is to execute HTTP methods. Execution of an HTTP method involves one or several HTTP request / HTTP response exchanges, usually handled internally by HttpClient. The user is expected to provide a request object to execute and HttpClient is expected to transmit the request to the target server return a corresponding response object, or throw an exception if execution was unsuccessful.
HttpClient最基本的功能就是執行http方法，執行http方法包括了一次或者幾次HTTP請求和相應的變化，通常也是通過HttpClient來處理的。只要使用者提供一個request的物件，HttpClient就會將使用者的請求傳送到目標伺服器上，並且返回一個respone物件，如果沒有執行成功將丟擲一個異常。
通過文件的介紹我們可以知道，傳送HTTP請求一般可以分為以下步驟
- 取得HttpClient物件
- 封裝http請求
- 執行http請求
- 處理結果
其中可以傳送的請求型別有GET, HEAD, POST, PUT, DELETE, TRACE 和 OPTIONS
HttpClient supports out of the box all HTTP methods defined in the HTTP/1.1 specification: GET, HEAD, POST, PUT, DELETE, TRACE and OPTIONS.
官方文件中的示例
//1.獲得一個httpclient物件
CloseableHttpClient httpclient = HttpClients.createDefault();
//2.生成一個get請求
HttpGet httpget = new HttpGet("http://localhost/");
//3.執行get請求並返回結果
CloseableHttpResponse response = httpclient.execute(httpget);
try {
//4.處理結果
} finally {
response.close();
}
介紹一下最常用的HttpGet和HttpPost。
RESTful提倡，通過HTTP請求對應的POST、GET、PUT、DELETE來完成對應的CRUD操作。
所以本文介紹一下通過GET獲取資料和POST提交資料的實現方法。
##傳送HttpGet
先介紹傳送HttpGet請求
/**
* 傳送HttpGet請求
* @param url
* @return
*/
public static String sendGet(String url) {
//1.獲得一個httpclient物件
CloseableHttpClient httpclient = HttpClients.createDefault();
//2.生成一個get請求
HttpGet httpget = new HttpGet(url);
CloseableHttpResponse response = null;
try {
//3.執行get請求並返回結果
response = httpclient.execute(httpget);
} catch (IOException e1) {
e1.printStackTrace();
}
String result = null;
try {
//4.處理結果，這裡將結果返回為字串
HttpEntity entity = response.getEntity();
if (entity != null) {
result = EntityUtils.toString(entity);
}
} catch (ParseException | IOException e) {
e.printStackTrace();
} finally {
try {
response.close();
} catch (IOException e) {
e.printStackTrace();
}
}
return result;
}
##傳送HttpPost
傳送HttpPost的方法和傳送HttpGet很類似，只是將請求型別給位HttpPost即可。
程式碼如下
/**
* 傳送不帶引數的HttpPost請求
* @param url
* @return
*/
public static String sendPost(String url) {
//1.獲得一個httpclient物件
CloseableHttpClient httpclient = HttpClients.createDefault();
//2.生成一個post請求
HttpPost httppost = new HttpPost(url);
CloseableHttpResponse response = null;
try {
//3.執行get請求並返回結果
response = httpclient.execute(httppost);
} catch (IOException e) {
e.printStackTrace();
}
//4.處理結果，這裡將結果返回為字串
HttpEntity entity = response.getEntity();
String result = null;
try {
result = EntityUtils.toString(entity);
} catch (ParseException | IOException e) {
e.printStackTrace();
}
return result;
}
##帶引數的HttpPost
傳送帶引數的HttpPost
Many applications need to simulate the process of submitting an HTML form, for instance, in order to log in to a web application or submit input data. HttpClient provides the entity class UrlEncodedFormEntity to facilitate the process.
HttpClient通過UrlEncodedFormEntity，來提交帶引數的請求
將需要提交的引數放在map裡
程式碼如下
/**
* 傳送HttpPost請求，引數為map
* @param url
* @param map
* @return
*/
public static String sendPost(String url, Map<String, String> map) {
CloseableHttpClient httpclient = HttpClients.createDefault();
List<NameValuePair> formparams = new ArrayList<NameValuePair>();
for (Map.Entry<String, String> entry : map.entrySet()) {
//給引數賦值
formparams.add(new BasicNameValuePair(entry.getKey(), entry.getValue()));
}
UrlEncodedFormEntity entity = new UrlEncodedFormEntity(formparams, Consts.UTF_8);
HttpPost httppost = new HttpPost(url);
httppost.setEntity(entity);
CloseableHttpResponse response = null;
try {
response = httpclient.execute(httppost);
} catch (IOException e) {
e.printStackTrace();
}
HttpEntity entity1 = response.getEntity();
String result = null;
try {
result = EntityUtils.toString(entity1);
} catch (ParseException | IOException e) {
e.printStackTrace();
}
return result;
}
##完整程式碼
完成程式碼如下，用到的jar包有httpclient-4.5.1.jar，httpcore-4.4.3.jar，依賴的jar有commons-logging-1.2.jar
注意是Apache HttpClient，不是commons-httpclient
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import org.apache.http.Consts;
import org.apache.http.HttpEntity;
import org.apache.http.NameValuePair;
import org.apache.http.ParseException;
import org.apache.http.client.entity.UrlEncodedFormEntity;
import org.apache.http.client.methods.CloseableHttpResponse;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.message.BasicNameValuePair;
import org.apache.http.util.EntityUtils;
/**
* @author GWCheng
*
*/
public class HttpUtil {
private static final CloseableHttpClient httpclient = HttpClients.createDefault();
/**
* 傳送HttpGet請求
* @param url
* @return
*/
public static String sendGet(String url) {
HttpGet httpget = new HttpGet(url);
CloseableHttpResponse response = null;
try {
response = httpclient.execute(httpget);
} catch (IOException e1) {
e1.printStackTrace();
}
String result = null;
try {
HttpEntity entity = response.getEntity();
if (entity != null) {
result = EntityUtils.toString(entity);
}
} catch (ParseException | IOException e) {
e.printStackTrace();
} finally {
try {
response.close();
} catch (IOException e) {
e.printStackTrace();
}
}
return result;
}
/**
* 傳送HttpPost請求，引數為map
* @param url
* @param map
* @return
*/
public static String sendPost(String url, Map<String, String> map) {
List<NameValuePair> formparams = new ArrayList<NameValuePair>();
for (Map.Entry<String, String> entry : map.entrySet()) {
formparams.add(new BasicNameValuePair(entry.getKey(), entry.getValue()));
}
UrlEncodedFormEntity entity = new UrlEncodedFormEntity(formparams, Consts.UTF_8);
HttpPost httppost = new HttpPost(url);
httppost.setEntity(entity);
CloseableHttpResponse response = null;
try {
response = httpclient.execute(httppost);
} catch (IOException e) {
e.printStackTrace();
}
HttpEntity entity1 = response.getEntity();
String result = null;
try {
result = EntityUtils.toString(entity1);
} catch (ParseException | IOException e) {
e.printStackTrace();
}
return result;
}
/**
* 傳送不帶引數的HttpPost請求
* @param url
* @return
*/
public static String sendPost(String url) {
HttpPost httppost = new HttpPost(url);
CloseableHttpResponse response = null;
try {
response = httpclient.execute(httppost);
} catch (IOException e) {
e.printStackTrace();
}
HttpEntity entity = response.getEntity();
String result = null;
try {
result = EntityUtils.toString(entity);
} catch (ParseException | IOException e) {
e.printStackTrace();
}
return result;
}
}
##測試用例
伺服器端程式碼
@Controller
@RequestMapping("/test")
// /test/**
public class TestController {
// /test/view post 提交資料，模擬表單
@RequestMapping(value = "/view", method = RequestMethod.POST)
public void viewTest(PrintWriter out, HttpServletResponse response, @RequestParam("param1") String param1,
@RequestParam("param2") String param2) {
response.setContentType("application/json;charset=UTF-8");
Gson gson = new GsonBuilder().create();
Map<String, Object> map = new HashMap<String, Object>();
map.put("param1", param1);
map.put("param2", param2);
System.out.println(gson.toJson(map));
out.print(gson.toJson(map));
}
// /test/view?param1=aaa¶m2=bbb get
@RequestMapping(value = "/view", method = RequestMethod.GET)
public void viewTest3(PrintWriter out, HttpServletResponse response, @RequestParam("param1") String param1,
@RequestParam("param2") String param2) {
response.setContentType("application/json;charset=UTF-8");
Gson gson = new GsonBuilder().create();
Map<String, Object> map = new HashMap<String, Object>();
map.put("param1", param1);
map.put("param2", param2);
System.out.println(gson.toJson(map));
out.print(gson.toJson(map));
}
// /test/view2/{courseId}
@RequestMapping(value = "/view2/{param}", method = RequestMethod.GET)
public void viewTest1(PrintWriter out, HttpServletResponse response, @PathVariable("param") String param) {
response.setContentType("application/json;charset=UTF-8");
Gson gson = new GsonBuilder().create();
Map<String, Object> map = new HashMap<String, Object>();
map.put("param", param);
out.print(gson.toJson(map));
}
// /test/view3
@RequestMapping(value = "/view3", method = RequestMethod.POST)
public void viewTest2(PrintWriter out, HttpServletResponse response) {
response.setContentType("application/json;charset=UTF-8");
Gson gson = new GsonBuilder().create();
Map<String, Object> map = new HashMap<String, Object>();
map.put("status", "success");
out.print(gson.toJson(map));
}
}
測試程式碼
public class HttpClientTest {
@Test
public void testGet() {
//百度天氣的api
//String url1 = "http://api.map.baidu.com/telematics/v3/weather?location=%E5%8C%97%E4%BA%AC&output=json&ak=W69oaDTCfuGwzNwmtVvgWfGH";
String url1 = "http://localhost:8080/wechat/test/view2/你好世界";
String result1 = HttpUtil.sendGet(url1);
System.out.println(result1);
//輸出{"param":"你好世界"}
}
@Test
public void testPost() throws UnsupportedEncodingException{
String url = "http://localhost:8080/wechat/test/view";
Map<String,String> map = new HashMap<String,String>();
map.put("param1", "你好世界");
map.put("param2", "哈哈");
String result = HttpUtil.sendPost(url, map);
System.out.println(result);
//輸出結果{"param1":"你好世界","param2":"哈哈"}
}
@Test
public void testPost1() throws UnsupportedEncodingException{
String url = "http://localhost:8080/wechat/test/view3";
String result = HttpUtil.sendPost(url);
System.out.println(result);
//輸出結果{"status":"success"}
}
}
建議通過HttpGet獲取資訊，HttpPost提交資訊，而HttpGet獲取資訊時需要提交的引數一般會在url中體現，或者以？傳參，或者在url中傳參，所以就沒寫HttpGet帶引數的。也希望大家能遵循Http的設計原則，通過HttpGet, HttpPost, HttpPut, HttpDelete,來實現獲取資料，提交資料，修改資料，和刪除資料的方法。
2018年10月25修改
依賴
<!--apache工具類-->
<dependency>
<groupId>org.apache.commons</groupId>
<artifactId>commons-lang3</artifactId>
<version>3.1</version>
</dependency>
<dependency>
<groupId>org.apache.commons</groupId>
<artifactId>commons-collections4</artifactId>
<version>4.1</version>
</dependency>
<!--lombok-->
<dependency>
<groupId>org.projectlombok</groupId>
<artifactId>lombok</artifactId>
<version>1.18.2</version>
<scope>provided</scope>
</dependency>
<!--httpclient-->
<dependency>
<groupId>org.apache.httpcomponents</groupId>
<artifactId>httpclient</artifactId>
<version>4.5.6</version>
</dependency>
<dependency>
<groupId>org.apache.httpcomponents</groupId>
<artifactId>httpmime</artifactId>
<version>4.5.6</version>
</dependency>
<!--log-->
<dependency>
<groupId>org.slf4j
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