近期在做項目時用到HttpClient工具,用來獲取一個pdf文件的鏈接,然後把pdf轉換成圖片。現在對HttpClient這個工具的使用做下記錄,方便以後查閱。
HttpClient作用:用來模擬發送get或者post請求,並獲取請求返回結果。
HttpClient使用步驟:
無論是使用HttpGet,還是使用HttpPost,都必須通過如下4步來訪問HTTP資源。
1.創建httpclient。
HttpClient client = new DefaultHttpClient()
2、創建HttpGet或HttpPost對象,將要請求的URL通過構造方法傳入HttpGet或HttpPost對象。
HttpGet request = new HttpGet(url);
3、使用DefaultHttpClient類的execute方法發送HTTP GET或HTTP POST請求,並返回HttpResponse對象。
HttpResponse response = client.execute(request);
int code = response.getStatusLine().getStatusCode();//如果code=200表示請求成功
4、通過HttpResponse接口的getEntity方法返回響應信息,並進行相應的處理。
HttpEntity entity = response.getEntity();
InputStream is = entity.getContent();
如果使用HttpPost方法提交HTTP POST請求,則需要使用HttpPost類的setEntity方法設置請求參數。參數則必須用NameValuePair[]數組存儲。
網上還有一位朋友做了個httpUtils工具,裏面封裝發送get和post請求。
package com.marco.common;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.URI;
import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.HttpStatus;
import org.apache.http.NameValuePair;
import org.apache.http.StatusLine;
import org.apache.http.client.HttpClient;
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.entity.StringEntity;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.message.BasicNameValuePair;
import org.apache.http.protocol.HTTP;
import org.apache.http.util.EntityUtils;
import org.apache.log4j.Logger;
/**
* @author 馬弦
* @date 2017年10月23日 下午2:49
* HttpClient工具類
*/
public class HttpUtil {
private static Logger logger = Logger.getLogger(HttpUtil.class);
/**
* get請求
* @return
*/
public static String doGet(String url) {
try {
HttpClient client = new DefaultHttpClient();
//發送get請求
HttpGet request = new HttpGet(url);
HttpResponse response = client.execute(request);
/**請求發送成功,並得到響應**/
if (response.getStatusLine().getStatusCode() == HttpStatus.SC_OK) {
/**讀取服務器返回過來的json字符串數據**/
String strResult = EntityUtils.toString(response.getEntity());
return strResult;
}
}
catch (IOException e) {
e.printStackTrace();
}
return null;
}
/**
* post請求(用於key-value格式的參數)
* @param url
* @param params
* @return
*/
public static String doPost(String url, Map params){
BufferedReader in = null;
try {
// 定義HttpClient
HttpClient client = new DefaultHttpClient();
// 實例化HTTP方法
HttpPost request = new HttpPost();
request.setURI(new URI(url));
//設置參數
List<NameValuePair> nvps = new ArrayList<NameValuePair>();
for (Iterator iter = params.keySet().iterator(); iter.hasNext();) {
String name = (String) iter.next();
String value = String.valueOf(params.get(name));
nvps.add(new BasicNameValuePair(name, value));
//System.out.println(name +"-"+value);
}
request.setEntity(new UrlEncodedFormEntity(nvps,HTTP.UTF_8));
HttpResponse response = client.execute(request);
int code = response.getStatusLine().getStatusCode();
if(code == 200){ //請求成功
in = new BufferedReader(new InputStreamReader(response.getEntity()
.getContent(),"utf-8"));
StringBuffer sb = new StringBuffer("");
String line = "";
String NL = System.getProperty("line.separator");
while ((line = in.readLine()) != null) {
sb.append(line + NL);
}
in.close();
return sb.toString();
}
else{ //
System.out.println("狀態碼:" + code);
return null;
}
}
catch(Exception e){
e.printStackTrace();
return null;
}
}
/**
* post請求(用於請求json格式的參數)
* @param url
* @param params
* @return
*/
public static String doPost(String url, String params) throws Exception {
CloseableHttpClient httpclient = HttpClients.createDefault();
HttpPost httpPost = new HttpPost(url);// 創建httpPost
httpPost.setHeader("Accept", "application/json");
httpPost.setHeader("Content-Type", "application/json");
String charSet = "UTF-8";
StringEntity entity = new StringEntity(params, charSet);
httpPost.setEntity(entity);
CloseableHttpResponse response = null;
try {
response = httpclient.execute(httpPost);
StatusLine status = response.getStatusLine();
int state = status.getStatusCode();
if (state == HttpStatus.SC_OK) {
HttpEntity responseEntity = response.getEntity();
String jsonString = EntityUtils.toString(responseEntity);
return jsonString;
}
else{
logger.error("請求返回:"+state+"("+url+")");
}
}
finally {
if (response != null) {
try {
response.close();
} catch (IOException e) {
e.printStackTrace();
}
}
try {
httpclient.close();
} catch (IOException e) {
e.printStackTrace();
}
}
return null;
}
}