HttpClient使用方法及基本引數含義
一、方法
使用HttpClient傳送請求、接收響應很簡單,一般需要如下幾步即可。
1. 建立HttpClient物件。
2. 建立請求方法的例項,並指定請求URL。如果需要傳送GET請求,建立HttpGet物件;如果需要傳送POST請求,建立HttpPost物件。
3. 如果需要傳送請求引數,可呼叫HttpGet、HttpPost共同的setParams(HetpParams params)方法來新增請求引數;對於HttpPost物件而言,也可呼叫setEntity(HttpEntity entity)方法來設定請求引數。
4. 呼叫HttpClient物件的execute(HttpUriRequest request)傳送請求,該方法返回一個HttpResponse。
5. 呼叫HttpResponse的getAllHeaders()、getHeaders(String name)等方法可獲取伺服器的響應頭;呼叫HttpResponse的getEntity()方法可獲取HttpEntity物件,該物件包裝了伺服器的響應內容。程式可通過該物件獲取伺服器的響應內容。
6. 釋放連線。無論執行方法是否成功,都必須釋放連線
二。程式碼
import java.io.IOException;
import java.net.URI;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import org.apache.http.NameValuePair;
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.client.utils.URIBuilder;
import org.apache.http.entity.ContentType;
import org.apache.http.entity.StringEntity;
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;
public static String doGet(String url, Map<String, String> param) {
// 建立Httpclient物件
CloseableHttpClient httpclient = HttpClients.createDefault();
String resultString = "";
CloseableHttpResponse response = null;
try {
// 建立uri
URIBuilder builder = new URIBuilder(url);
if (param != null) {
for (String key : param.keySet()) {
builder.addParameter(key, param.get(key));
}
}
URI uri = builder.build();
// 建立http GET請求
HttpGet httpGet = new HttpGet(uri);
// 執行請求
response = httpclient.execute(httpGet);
// 判斷返回狀態是否為200
if (response.getStatusLine().getStatusCode() == 200) {
resultString = EntityUtils.toString(response.getEntity(), "UTF-8");
}
} catch (Exception e) {
e.printStackTrace();
} finally {
try {
if (response != null) {
response.close();
}
httpclient.close();
} catch (IOException e) {
e.printStackTrace();
}
}
return resultString;
}
public static String doGet(String url) {
return doGet(url, null);
}
public static String doPost(String url, Map<String, String> param) {
// 建立Httpclient物件
CloseableHttpClient httpClient = HttpClients.createDefault();
CloseableHttpResponse response = null;
String resultString = "";
try {
// 建立Http Post請求
HttpPost httpPost = new HttpPost(url);
// 建立引數列表
if (param != null) {
List<NameValuePair> paramList = new ArrayList<>();
for (String key : param.keySet()) {
paramList.add(new BasicNameValuePair(key, param.get(key)));
}
// 模擬表單
UrlEncodedFormEntity entity = new UrlEncodedFormEntity(paramList);
httpPost.setEntity(entity);
}
// 執行http請求
response = httpClient.execute(httpPost);
resultString = EntityUtils.toString(response.getEntity(), "utf-8");
} catch (Exception e) {
e.printStackTrace();
} finally {
try {
response.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
return resultString;
}
public static String doPost(String url) {
return doPost(url, null);
}
public static String doPostJson(String url, String json) {
// 建立Httpclient物件
CloseableHttpClient httpClient = HttpClients.createDefault();
CloseableHttpResponse response = null;
String resultString = "";
try {
// 建立Http Post請求
HttpPost httpPost = new HttpPost(url);
// 建立請求內容
StringEntity entity = new StringEntity(json, ContentType.APPLICATION_JSON);
httpPost.setEntity(entity);
// 執行http請求
response = httpClient.execute(httpPost);
resultString = EntityUtils.toString(response.getEntity(), "utf-8");
} catch (Exception e) {
e.printStackTrace();
} finally {
try {
response.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
return resultString;
}